| 1. |
- Barnes, Ashley T., et al.
(författare)
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Mother of dragons: A massive, quiescent core in the dragon cloud (IRDC G028.37+00.07)
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 675
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Tidskriftsartikel (refereegranskat)abstract
- Context. Core accretion models of massive star formation require the existence of massive, starless cores within molecular clouds. Yet, only a small number of candidates for such truly massive, monolithic cores are currently known. Aims. Here we analyse a massive core in the well-studied infrared-dark cloud (IRDC) called the dragon clouda'(also known as G028.37+00.07 or Cloud Ca). This core (C2c1) sits at the end of a chain of a roughly equally spaced actively star-forming cores near the center of the IRDC. Methods. We present new high-angular-resolution 1 mm ALMA dust continuum and molecular line observations of the massive core. Results. The high-angular-resolution observations show that this region fragments into two cores, C2c1a and C2c1b, which retain significant background-subtracted masses of 23 M· and 2 M· (31 M· and 6 M· without background subtraction), respectively. The cores do not appear to fragment further on the scales of our highest-angular-resolution images (0.2 , 0.005 pc ∼ 1000 AU). We find that these cores are very dense (nH2 > 106 cm-3) and have only trans-sonic non-thermal motions ( 3s ∼ 1). Together the mass, density, and internal motions imply a virial parameter of
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| 2. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 3. |
- Cosentino, Giuliana, 1990, et al.
(författare)
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Deuterium fractionation across the infrared-dark cloud G034.77-00.55 interacting with the supernova remnant W44
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 675
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Tidskriftsartikel (refereegranskat)abstract
- Supernova remnants (SNRs) may regulate star formation in galaxies. For example, SNR-driven shocks may form new molecular gas or compress pre-existing clouds and trigger the formation of new stars. Aims. To test this scenario, we measured the deuteration of N2H+, DNfrac 2H+- a well-studied tracer of pre-stellar cores - across the infrared-dark cloud (IRDC) G034.77-00.55, which is known to be experiencing a shock interaction with the SNR W44. Methods. We use N2H+ and N2D+ J = 1-0 single pointing observations obtained with the 30m antenna at the Instituto de Radioastronomia Millimetrica to infer DN2H+ frac towards five positions across the cloud, namely a massive core, different regions across the shock front, a dense clump, and ambient gas. Results. We find DN2H+ frac in the range 0.03-0.1, which is several orders of magnitude larger than the cosmic D/H ratio (∼10-5). The DN2H+ frac across the shock front is enhanced by more than a factor of 2 (DNfrac 2H+∼ 0.05-0.07) with respect to the ambient gas (=0.03) and similar to that measured generally in pre-stellar cores. Indeed, in the massive core and dense clump regions of this IRDC we measure DN2H+ frac ∼ 0.1.
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| 4. |
- Entekhabi, N., et al.
(författare)
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Astrochemical modelling of infrared dark clouds
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 662
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Tidskriftsartikel (refereegranskat)abstract
- Context. Infrared dark clouds (IRDCs) are cold, dense regions of the interstellar medium (ISM) that are likely to represent the initial conditions for massive star and star cluster formation. It is thus important to study the physical and chemical conditions of IRDCs to provide constraints and inputs for theoretical models of these processes. Aims. We aim to determine the astrochemical conditions, especially the cosmic ray ionisation rate (CRIR) and chemical age, in different regions of the massive IRDC G28.37+00.07 by comparing observed abundances of multiple molecules and molecular ions with the predictions of astrochemical models. Methods. We have computed a series of single-zone, time-dependent, astrochemical models with a gas-grain network that systematically explores the parameter space of the density, temperature, CRIR, and visual extinction. We have also investigated the effects of choices of CO ice binding energy and temperatures achieved in the transient heating of grains when struck by cosmic rays. We selected ten positions across the IRDC that are known to have a variety of star formation activity. We utilised mid-infrared extinction maps and sub-millimetre (sub-mm) emission maps to measure the mass surface densities of these regions needed for abundance and volume density estimates. The sub-mm emission maps were also used to measure temperatures. We then used Instituto de Radioas-tromía Milimétrica (IRAM) 30 m observations of various tracers, especially C18O(1-0), H13CO+(1-0), HC18O+(1-0), and N2H+(1-0), to estimate column densities and thus abundances. Finally, we investigated the range of astrochemical conditions that are consistent with the observed abundances. Results. The typical physical conditions of the IRDC regions are nH ∼ 3 ×-104 to 105 cm-3 and T ∼ 10 to 15 K. Strong emission of H13CO+(1-0) and N2H+(1-0) is detected towards all the positions and these species are used to define relatively narrow velocity ranges of the IRDC regions, which are used for estimates of CO abundances, via C18O(1-0). We would like to note that CO depletion factors are estimated to be in the range fD ∼ 3 to 10. Using estimates of the abundances of CO, HCO+, and N2H+, we find consistency with astrochemical models that have relatively low CRIRs of ζ ∼ 10-18 to ∼10-17 s-1, with no evidence for systematic variation with the level of star formation activity. Astrochemical ages, which are defined with a reference to an initial condition of all H in H2, all C in CO, and all other species in atomic form, are found to be <1 Myr. We also explore the effects of using other detected species, that is HCN, HNC, HNCO, CH3OH, and H2CO, to constrain the models. These generally lead to implied conditions with higher levels of CRIRs and older chemical ages. Considering the observed fD versus nH relation of the ten positions, which we find to have relatively little scatter, we discuss potential ways in which the astrochemical models can match such a relation as a quasi-equilibrium limit valid at ages of at least a few free-fall times, that is 3;0.3 Myr, including the effect of CO envelope contamination, small variations in temperature history near 15 K, CO-ice binding energy uncertainties, and CR-induced desorption. We find general consistency with the data of ∼0.5 Myr-old models that have ζ ∼ 2-5-10-18 s-1 and CO abundances set by a balance of freeze-out with CR-induced desorption. Conclusions. We have constrained the astrochemical conditions in ten regions in a massive IRDC, finding evidence for relatively low values of CRIR compared to diffuse ISM levels. We have not seen clear evidence for variation in the CRIR with the level of star formation activity. We favour models that involve relatively low CRIRs (≲ 10-17 s-1) and relatively old chemical ages (≳ 3;0.3 Myr, i.e. 3;3tff). We discuss potential sources of systematic uncertainties in these results and the overall implications for IRDC evolutionary history and astrochemical models.
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| 5. |
- Jones, Benedict C, et al.
(författare)
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To which world regions does the valence-dominance model of social perception apply?
- 2021
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Ingår i: Nature Human Behaviour. - : Springer Science and Business Media LLC. - 2397-3374. ; 5:1, s. 159-169
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Tidskriftsartikel (refereegranskat)abstract
- Over the past 10 years, Oosterhof and Todorov's valence-dominance model has emerged as the most prominent account of how people evaluate faces on social dimensions. In this model, two dimensions (valence and dominance) underpin social judgements of faces. Because this model has primarily been developed and tested in Western regions, it is unclear whether these findings apply to other regions. We addressed this question by replicating Oosterhof and Todorov's methodology across 11 world regions, 41 countries and 11,570 participants. When we used Oosterhof and Todorov's original analysis strategy, the valence-dominance model generalized across regions. When we used an alternative methodology to allow for correlated dimensions, we observed much less generalization. Collectively, these results suggest that, while the valence-dominance model generalizes very well across regions when dimensions are forced to be orthogonal, regional differences are revealed when we use different extraction methods and correlate and rotate the dimension reduction solution. PROTOCOL REGISTRATION: The stage 1 protocol for this Registered Report was accepted in principle on 5 November 2018. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.7611443.v1 .
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| 6. |
- Law, Chi Yan, 1990, et al.
(författare)
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Polarized Light from Massive Protoclusters (POLIMAP). I. Dissecting the Role of Magnetic Fields in the Massive Infrared Dark Cloud G28.37+0.07
- 2024
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 967:2
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic fields may play a crucial role in setting the initial conditions of massive star and star cluster formation. To investigate this, we report SOFIA-HAWC+ 214 μm observations of polarized thermal dust emission and high-resolution GBT-Argus C18O(1-0) observations toward the massive Infrared Dark Cloud (IRDC) G28.37+0.07. Considering the local dispersion of B-field orientations, we produce a map of the B-field strength of the IRDC, which exhibits values between ∼0.03 and 1 mG based on a refined Davis-Chandrasekhar-Fermi method proposed by Skalidis & Tassis. Comparing to a map of inferred density, the IRDC exhibits a B-n relation with a power-law index of 0.51 ± 0.02, which is consistent with a scenario of magnetically regulated anisotropic collapse. Consideration of the mass-to-flux ratio map indicates that magnetic fields are dynamically important in most regions of the IRDC. A virial analysis of a sample of massive, dense cores in the IRDC, including evaluation of magnetic and kinetic internal and surface terms, indicates consistency with virial equilibrium, sub-Alfvénic conditions, and a dominant role for B-fields in regulating collapse. A clear alignment of magnetic field morphology with the direction of the steepest column density gradient is also detected. However, there is no preferred orientation of protostellar outflow directions with the B-field. Overall, these results indicate that magnetic fields play a crucial role in regulating massive star and star cluster formation, and therefore they need to be accounted for in theoretical models of these processes.
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| 7. |
- Appel, Sabrina M., et al.
(författare)
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What Sets the Star Formation Rate of Molecular Clouds? The Density Distribution as a Fingerprint of Compression and Expansion Rates
- 2023
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 954:1
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Tidskriftsartikel (refereegranskat)abstract
- We use a suite of 3D simulations of star-forming molecular clouds, with and without stellar feedback, magnetic fields, and driven turbulence, to study the compression and expansion rates of the gas as functions of density. We show that, around the mean density, supersonic turbulence promotes rough equilibrium between the amounts of compressing and expanding gas, consistent with continuous gas cycling between high- and low-density states. We find that the inclusion of protostellar jets produces rapidly expanding and compressing low-density gas. We find that the gas mass flux peaks at the transition between the lognormal and power-law forms of the density probability distribution function (PDF). This is consistent with the transition density tracking the post-shock density, which promotes an enhancement of mass at this density (i.e., shock compression and filament formation). At high densities, the gas dynamics are dominated by self-gravity: the compression rate in all of our runs matches the rate of the run with only gravity, suggesting that processes other than self-gravity have little effect at these densities. The net gas mass flux becomes constant at a density below the sink formation threshold, where it equals the star formation rate. The density at which the net gas mass flux equals the star formation rate is one order of magnitude lower than our sink threshold density, corresponds to the formation of the second power-law tail in the density PDF, and sets the overall star formation rates of these simulations.
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| 8. |
- Barnes, A. T., et al.
(författare)
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ALMA-IRDC: dense gas mass distribution from cloud to core scales
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 503:3, s. 4601-4626
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Tidskriftsartikel (refereegranskat)abstract
- Infrared dark clouds (IRDCs) are potential hosts of the elusive early phases of high mass star formation (HMSF). Here, we conduct an in-depth analysis of the fragmentation properties of a sample of 10 IRDCs, which have been highlighted as some of the best candidates to study HMSF within the Milky Way. To do so, we have obtained a set of large mosaics covering these IRDCs with Atacama Large Millimeter/submillimeter Array (ALMA) at Band 3 (or 3 mm). These observations have a high angular resolution (similar to 3 arcsec; similar to 0.05 pc), and high continuum and spectral line sensitivity (similar to 0.15 mJy beam(-1) and similar to 0.2 K per 0.1 km s(-1) channel at the N2H+ (1 - 0) transition). From the dust continuum emission, we identify 96 cores ranging from low to high mass (M = 3.4-50.9M(circle dot)) that are gravitationally bound (alpha(vir) = 0.3-1.3) and which would require magnetic field strengths of B = 0.3-1.0 mG to be in virial equilibrium. We combine these results with a homogenized catalogue of literature cores to recover the hierarchical structure within these clouds over four orders of magnitude in spatial scale (0.01-10 pc). Using supplementary observations at an even higher angular resolution, we find that the smallest fragments (<0.02 pc) within this hierarchy do not currently have the mass and/or the density required to form high-mass stars. None the less, the new ALMA observations presented in this paper have facilitated the identification of 19 (6 quiescent and 13 star-forming) cores that retain >16M(circle dot) without further fragmentation. These high-mass cores contain trans-sonic non-thermal motions, are kinematically sub-virial, and require moderate magnetic field strengths for support against collapse. The identification of these potential sites of HMSF represents a key step in allowing us to test the predictions from high-mass star and cluster formation theories.
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| 9. |
- Bisbas, Thomas G., et al.
(författare)
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Photodissociation region diagnostics across galactic environments
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 502:2, s. 2701-2732
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Tidskriftsartikel (refereegranskat)abstract
- We present three-dimensional astrochemical simulations and synthetic observations of magnetized, turbulent, self-gravitating molecular clouds. We explore various galactic interstellar medium environments, including cosmic ray ionization rates in the range of zeta(CR) = 10(-17)-10(-14)S(-1), far-UV intensities in the range of G(theta) = 1-10(3) and metallicities in the range of Z = 0.1-2Z(circle dot). The simulations also probe a range of densities and levels of turbulence, including cases where the gas has undergone recent compression due to cloud-cloud collisions. We examine: (i) the column densities of carbon species across the cycle of CII, CI, and CO, along with OI, in relation to the H I-to-H-2 transition; (ii) the velocity-integrated emission of [CII] 158 mu m, [C-13 II] 158 mu m, [C I] 609 mu m and 370 mu m, [O I] 63 mu m and 146 mu m, and of the first ten (CO)-C-12 rotational transitions; (iii) the corresponding Spectral Line Energy Distributions; (iv) the usage of [C II] and [O I] 63 mu m to describe the dynamical state of the clouds; (v) the behaviour of the most commonly used ratios between transitions of CO and [CI]; and (vi) the conversion factors for using CO and CI as H-2-gas tracers. We find that enhanced cosmic ray energy densities enhance all aforementioned line intensities. At low metallicities, the emission of [C11] is well connected with the H-2 column, making it a promising new H-2 tracer in metal-poor environments. The conversion factors of X-CO and X-CI depend on metallicity and the cosmic ray ionization rate, but not on FUV intensity. In the era of ALMA, SOFIA, and the forthcoming CCAT-prime telescope, our results can be used to understand better the behaviour of systems in a wide range of galactic and extragalactic environments.
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| 10. |
- Cable, Jennifer, et al.
(författare)
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Sleep and circadian rhythms : pillars of health-a Keystone Symposia report
- 2021
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Ingår i: Annals of the New York Academy of Sciences. - : John Wiley & Sons. - 0077-8923 .- 1749-6632. ; 1506:1, s. 18-34
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Tidskriftsartikel (refereegranskat)abstract
- The human circadian system consists of the master clock in the suprachiasmatic nuclei of the hypothalamus as well as in peripheral molecular clocks located in organs throughout the body. This system plays a major role in the temporal organization of biological and physiological processes, such as body temperature, blood pressure, hormone secretion, gene expression, and immune functions, which all manifest consistent diurnal patterns. Many facets of modern life, such as work schedules, travel, and social activities, can lead to sleep/wake and eating schedules that are misaligned relative to the biological clock. This misalignment can disrupt and impair physiological and psychological parameters that may ultimately put people at higher risk for chronic diseases like cancer, cardiovascular disease, and other metabolic disorders. Understanding the mechanisms that regulate sleep circadian rhythms may ultimately lead to insights on behavioral interventions that can lower the risk of these diseases. On February 25, 2021, experts in sleep, circadian rhythms, and chronobiology met virtually for the Keystone eSymposium "Sleep & Circadian Rhythms: Pillars of Health" to discuss the latest research for understanding the bidirectional relationships between sleep, circadian rhythms, and health and disease.
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| 11. |
- Cai, Maxwell X., et al.
(författare)
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Inside-out planet formation: VI. oligarchic coagulation of planetesimals from a pebble ring?
- 2022
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 510:4, s. 5486-5499
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Tidskriftsartikel (refereegranskat)abstract
- Inside-Out Planet Formation (IOPF) is a theory addressing the origin of Systems of Tightly-Packed Inner Planets (STIPs) via in situ formation and growth of the planets. It predicts that a pebble ring is established at the pressure maximum associated with the dead zone inner boundary (DZIB) with an inner disc magnetorotational instability (MRI)-active region. Using direct N -body simulations, we study the collisional evolution of planetesimals formed from such a pebble ring, in particular, examining whether a single dominant planet emerges. We consider a variety of models, including some in which the planetesimals are continuing to grow via pebble accretion. We find that the planetesimal ring undergoes oligarchic evolution, and typically turns into 2 or 3 surviving oligarchs on nearly coplanar and circular orbits, independent of the explored initial conditions or form of pebble accretion. The most massive oligarchs typically consist of about 70 per cent of the total mass, with the building-up process typically finishing within ∼10 5 yr. Ho we ver, a relati vely massi ve secondary planet al w ays remains with ∼30 -65 per cent of the mass of the primary. Such secondary planets have properties that are inconsistent with the observed properties of the innermost pairs of planets in STIPs. Thus, for IOPF to be a viable theory for STIP formation, it needs to be sho wn ho w oligarchic growth of a relatively massive secondary from the initial pebble ring can be a v oided. We discuss some potential additional physical processes that should be included in the modelling and explored as next steps.
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| 12. |
- Calabrese, Claudia, et al.
(författare)
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Genomic basis for RNA alterations in cancer
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 578:7793, s. 129-136
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Tidskriftsartikel (refereegranskat)abstract
- Transcript alterations often result from somatic changes in cancer genomes1. Various forms of RNA alterations have been described in cancer, including overexpression2, altered splicing3 and gene fusions4; however, it is difficult to attribute these to underlying genomic changes owing to heterogeneity among patients and tumour types, and the relatively small cohorts of patients for whom samples have been analysed by both transcriptome and whole-genome sequencing. Here we present, to our knowledge, the most comprehensive catalogue of cancer-associated gene alterations to date, obtained by characterizing tumour transcriptomes from 1,188 donors of the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA)5. Using matched whole-genome sequencing data, we associated several categories of RNA alterations with germline and somatic DNA alterations, and identified probable genetic mechanisms. Somatic copy-number alterations were the major drivers of variations in total gene and allele-specific expression. We identified 649 associations of somatic single-nucleotide variants with gene expression in cis, of which 68.4% involved associations with flanking non-coding regions of the gene. We found 1,900 splicing alterations associated with somatic mutations, including the formation of exons within introns in proximity to Alu elements. In addition, 82% of gene fusions were associated with structural variants, including 75 of a new class, termed 'bridged' fusions, in which a third genomic location bridges two genes. We observed transcriptomic alteration signatures that differ between cancer types and have associations with variations in DNA mutational signatures. This compendium of RNA alterations in the genomic context provides a rich resource for identifying genes and mechanisms that are functionally implicated in cancer.
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| 13. |
- Caretta, Martina Angela, et al.
(författare)
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Water
- 2022
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Ingår i: Climate Change 2022: Impacts, Adaptation and Vulnerability : Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change - Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 14. |
- Cevallos Soto, Arturo, 1993, et al.
(författare)
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Inside-out planet formation - VII. Astrochemical models of protoplanetary discs and implications for planetary compositions
- 2022
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 517:2, s. 2285-2308
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Tidskriftsartikel (refereegranskat)abstract
- Inside-out planet formation (IOPF) proposes that the abundant systems of close-in Super-Earths and Mini-Neptunes form in situ at the pressure maximum associated with the dead zone inner boundary (DZIB). We present a model of physical and chemical evolution of protoplanetary disc midplanes that follows gas advection, radial drift of pebbles, and gas-grain chemistry to predict abundances from similar to 300 au down to the DZIB near 0.2 au. We consider typical disc properties relevant for IOPF, i.e. accretion rates 10(-9) < (m) over dot/(M-circle dot, yr(-1)) < 10(-8) and viscosity parameter alpha = 10(-)(4), and evolve for fiducial duration of 10(5) yr. For outer, cool disc regions, we find that C and up to 90 per cent of 0 nuclei start locked in CO and O-2 ice, which keeps abundances of CO2 and H2O one order of magnitude lower. Radial drift of icy pebbles is influential, with gas-phase abundances of volatiles enhanced up to two orders of magnitude at icelines, while the outer disc becomes depleted of dust. Discs with decreasing accretion rates gradually cool, which draws in icelines closer to the star. At less than or similar to 1 au, advective models yield water-rich gas with C/O ratios less than or similar to 0.1, which may be inherited by atmospheres of planets forming here via IOPF. For planetary interiors built by pebble accretion, IOPF predicts volatile-poor compositions. However, advectively enhanced volatile mass fractions of similar to 10 per cent can occur at the water iceline.
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| 15. |
- Cheng, Yu, et al.
(författare)
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Gas Kinematics of the Massive Protocluster G286.21+0.17 Revealed by ALMA
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 894:2
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Tidskriftsartikel (refereegranskat)abstract
- We study the gas kinematics and dynamics of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array using spectral lines of {equation presented}(3-2), and DCN(3-2). On the parsec clump scale, C18O emission appears highly filamentary around the systemic velocity, N2D+ and DCO+ are more closely associated with the dust continuum, and DCN is strongly concentrated toward the protocluster center, where no or only weak detection is seen for N2D and DCO+, possibly due to this region being at a relatively evolved evolutionary stage. Spectra of 76 continuum-defined dense cores, typically a few 1000 au in size, are analyzed to measure their centroid velocities and internal velocity dispersions. There are no statistically significant velocity offsets of the cores among the different dense gas tracers. Furthermore, the majority (71%) of the dense cores have subthermal velocity offsets with respect to their surrounding, lower-density C18O-emitting gas. Within the uncertainties, the dense cores in G286 show internal kinematics that are consistent with being in virial equilibrium. On clump scales, the core-to-core velocity dispersion is also similar to that required for virial equilibrium in the protocluster potential. However, the distribution in velocity of the cores is largely composed of two spatially distinct groups, which indicates that the dense molecular gas has not yet relaxed to virial equilibrium, perhaps due to there being recent/continuous infall into the system.
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| 16. |
- Cheng, Yu, et al.
(författare)
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Star Formation in a Strongly Magnetized Cloud
- 2021
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 916:2
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Tidskriftsartikel (refereegranskat)abstract
- We study star formation in the Center Ridge 1 (CR1) clump in the Vela C giant molecular cloud, selected as a high column density region that shows the lowest level of dust continuum polarization-angle dispersion, likely indicating that the magnetic field is relatively strong. We observe the source with the Atacama Large Millimeter/submillimeter Array 7 m array at 1.05 and 1.3 mm wavelengths, which enable measurements of dust temperature, core mass, and astrochemical deuteration. A relatively modest number of 11 dense cores are identified via their dust continuum emission, with masses spanning from 0.17-6.7 M-circle dot. Overall CR1 has a relatively low compact dense gas fraction compared with other typical clouds with similar column densities, which may be a result of the strong magnetic field and/or the very early evolutionary stage of this region. The deuteration ratios, D-frac, of the cores, measured with N2H+(3-2) and N2D+(3-2) lines, span from 0.011-0.85, with the latter being one of the highest values yet detected. The level of deuteration appears to decrease with evolution from prestellar to protostellar phase. A linear filament, running approximately parallel with the large scale magnetic field orientation, is seen connecting the two most massive cores, each having CO bipolar outflows aligned orthogonally to the filament. The filament contains the most deuterated core, likely to be prestellar and located midway between the protostars. The observations permit measurement of the full deuteration structure of the filament along its length, which we present. We also discuss the kinematics and dynamics of this structure, as well as of the dense core population.
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| 17. |
- Cheng, Yu, et al.
(författare)
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Stellar Variability in a Forming Massive Star Cluster
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 897:1
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Tidskriftsartikel (refereegranskat)abstract
- We present a near-infrared (NIR) variability analysis for a 6′ 6′ region, which encompasses the massive protocluster G286.21+0.17. The total sample comprises more than 5000 objects, of which 562 show signs of a circumstellar disk based on their infrared colors. The data includes Hubble Space Telescope observations taken in two epochs separated by 3 yr in the F110W and F160W bands. 363 objects (7% of the sample) exhibit NIR variability at a significant level (Stetson index >1.7), and a higher variability fraction (14%) is found for the young stellar objects with disk excesses. We identified four high amplitude (>0.6 mag) variables seen in both NIR bands. Follow-up and archival observations of the most variable object in this survey (G286.2032+0.1740) reveal a rising light curve over 8 yr from 2011 to 2019, with a K band brightening of 3.5 mag. Overall the temporal behavior of G286.2032+0.1740 resembles that of typical FU Ori objects; however, its pre-burst luminosity indicates it has a very low mass (<0.12 M o˙), making it an extreme case of an outburst event that is still ongoing.
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| 18. |
- Cheng, Yu, et al.
(författare)
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The Disk Population in a Distant Massive Protocluster
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 940:2
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Tidskriftsartikel (refereegranskat)abstract
- The unprecedented angular resolution and sensitivity of the Atacama Large Millimeter/submillimeter Array make it possible to unveil disk populations in distant (>2 kpc), embedded young cluster environments. We have conducted an observation toward the central region of the massive protocluster G286.21+0.16 at 1.3 mm. With a spatial resolution of 23 mas and a sensitivity of 15 mu Jy beam(-1), we detect a total of 38 protostellar disks. These disks have dust masses ranging from about 53 to 1825 M (circle plus), assuming a dust temperature of 20 K. This sample is not closely associated with previously identified dense cores, as would be expected for disks around Class 0 protostars. Thus, we expect our sample, being flux-limited, to be mainly composed of Class I/flat-spectrum source disks, since these are typically more massive than Class II disks. Furthermore, we find that the distributions of disk masses and radii are statistically indistinguishable from those of the Class I/flat-spectrum objects in the Orion molecular cloud, indicating that similar processes are operating in G286.21+0.16 to regulate disk formation and evolution. The cluster center appears to host a massive protostellar system composed of three sources within 1200 au, including a potential binary with 600 au projected separation. Relative to this center, there is no evidence for widespread mass segregation in the disk population. We do find a tentative trend of increasing disk radius versus distance from the cluster center, which may point to the influence of dynamical interactions being stronger in the central regions.
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| 19. |
- Cosentino, Giuliana, 1990, et al.
(författare)
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Negative and positive feedback from a supernova remnant with SHREC. a detailed study of the shocked gas in IC443
- 2022
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 511:1, s. 953-963
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Tidskriftsartikel (refereegranskat)abstract
- Supernova remnants (SNRs) contribute to regulate the star formation efficiency and evolution of galaxies. As they expand into the interstellar medium (ISM), they transfer vast amounts of energy and momentum that displace, compress, and heat the surrounding material. Despite the extensive work in galaxy evolution models, it remains to be observationally validated to what extent the molecular ISM is affected by the interaction with SNRs. We use the first results of the ESO-ARO Public Spectroscopic Survey SHREC to investigate the shock interaction between the SNR IC443 and the nearby molecular clump G. We use high-sensitivity SiO(2-1) and (HCO+)-C-13 (1-0) maps obtained by SHREC together with SiO(1-0) observations obtained with the 40-m telescope at the Yebes Observatory. We find that the bulk of the SiO emission is arising from the ongoing shock interaction between IC443 and clump G. The shocked gas shows a well-ordered kinematic structure, with velocities blue-shifted with respect to the central velocity of the SNR, similar to what observed towards other SNR-cloud interaction sites. The shock compression enhances the molecular gas density, n(H-2), up to >10(5) cm(-3), a factor of >10 higher than the ambient gas density and similar to values required to ignite star formation. Finally, we estimate that up to 50 per cent of the momentum injected by IC443 is transferred to the interacting molecular material. Therefore, the molecular ISM may represent an important momentum carrier in sites of SNR-cloud interactions.
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| 20. |
- Cosentino, Giuliana, 1990, et al.
(författare)
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SiO emission as a probe of cloud-cloud collisions in infrared dark clouds
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 499:2, s. 1666-1681
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Tidskriftsartikel (refereegranskat)abstract
- Infrared dark clouds (IRDCs) are very dense and highly extincted regions that host the initial conditions of star and stellar cluster formation. It is crucial to study the kinematics and molecular content of IRDCs to test their formation mechanism and ultimately characterize these initial conditions. We have obtained high-sensitivity Silicon Monoxide, SiO(2-1), emission maps towards the six IRDCs, G018.82-00.28, G019.27+00.07, G028.53-00.25, G028.67+00.13, G038.95-00.47, and G053.11+00.05 (cloud A, B, D, E, I, and J, respectively), using the 30-m antenna at the Instituto de Radioastronomia Millimetrica (IRAM30m). We have investigated the SiO spatial distribution and kinematic structure across the six clouds to look for signatures of cloud-cloud collision events that may have formed the IRDCs and triggered star formation within them. Towards clouds A, B, D, I, and J, we detect spatially compact SiO emission with broad-line profiles that are spatially coincident with massive cores. Towards the IRDCs A and I, we report an additional SiO component that shows narrow-line profiles and that is widespread across quiescent regions. Finally, we do not detect any significant SiO emission towards cloud E. We suggest that the broad and compact SiO emission detected towards the clouds is likely associated with ongoing star formation activity within the IRDCs. However, the additional narrow and widespread SiO emission detected towards cloud A and I may have originated from the collision between the IRDCs and flows of molecular gas pushed towards the clouds by nearby H II regions.
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| 21. |
- Costa Silva, A. R., et al.
(författare)
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NIR jets from a clustered region of massive star formation: Morphology and composition in the IRAS 18264-1152 region
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 659
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Tidskriftsartikel (refereegranskat)abstract
- Context. Massive stars play crucial roles in determining the physical and chemical evolution of galaxies. However, they form deeply embedded in their parental clouds, making it challenging to directly observe these stars and their immediate environments. It is known that accretion and ejection processes are intrinsically related, thus observing the massive protostellar outflows can provide crucial information about the processes governing massive star formation very close to the central engine. Aims. We aim to probe the IRAS 18264-1152 (also known as G19.88-0.53) high-mass star-forming complex in the near infrared (NIR) through its molecular hydrogen (H2) jets to analyse the morphology and composition of the line emitting regions and to compare with other outflow tracers. Methods. We observed the H2 NIR jets via K-band (1.9 2.5 μm) observations obtained with the integral field units VLT/SINFONI and VLT/KMOS. VLT/SINFONI provides the highest NIR angular resolution achieved so far for the central region of IRAS 18264-1152 (∼0.2). We compared the geometry of the NIR outflows with that of the associated molecular outflow, probed by CO (2-1) emission mapped with the Submillimeter Array. Results. We identify nine point sources in the SINFONI and KMOS fields of view. Four of these display a rising continuum in the K-band and are Brγ emitters, revealing that they are young, potentially jet-driving sources. The spectro-imaging analysis focusses on the H2 jets, for which we derived visual extinction, temperature, column density, area, and mass. The intensity, velocity, and excitation maps based on H2 emission strongly support the existence of a protostellar cluster in this region, with at least two (and up to four) different large-scale outflows, found through the NIR and radio observations. We compare our results with those found in the literature and find good agreement in the outflow morphology. This multi-wavelength comparison also allows us to derive a stellar density of ∼4000 stars pc-3. Conclusions. Our study reveals the presence of several outflows driven by young sources from a forming cluster of young, massive stars, demonstrating the utility of such NIR observations for characterising massive star-forming regions. Moreover, the derived stellar number density together with the geometry of the outflows suggest that stars can form in a relatively ordered manner in this cluster.
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| 22. |
- Crowe, S., et al.
(författare)
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Near-infrared observations of outflows and young stellar objects in the massive star-forming region AFGL 5180
- 2024
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 682
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Tidskriftsartikel (refereegranskat)abstract
- Context. Massive stars play important roles throughout the universe; however, their formation remains poorly understood. Observations of jets and outflows in high-mass star-forming regions, as well as surveys of young stellar object (YSO) content, can help test theoretical models of massive star formation. Aims. We aim at characterizing the massive star-forming region AFGL 5180 in the near-infrared (NIR), identifying outflows and relating these to sub-mm/mm sources, as well as surveying the overall YSO surface number density to compare to massive star formation models. Methods. Broad- and narrow-band imaging of AFGL 5180 was made in the NIR with the Large Binocular Telescope, in both seeing-limited (~0.5′) and high angular resolution (~0.09′) Adaptive Optics (AO) modes, as well as with the Hubble Space Telescope. Archival continuum data from the Atacama Millimeter/Submillimeter Array (ALMA) was also utilized. Results. At least 40 jet knots were identified via NIR emission from H2 and [FeII] tracing shocked gas. Bright jet knots outflowing from the central most massive protostar, S4 (estimated mass ~11 M⊙, via SED fitting), are detected towards the east of the source and are resolved in fine detail with the AO imaging. Additional knots are distributed throughout the field, likely indicating the presence of multiple driving sources. Sub-millimeter sources detected by ALMA are shown to be grouped in two main complexes, AFGL 5180 M and a small cluster ~15′ (0.15 pc in projection) to the south, AFGL 5180 S. From our NIR continuum images we identify YSO candidates down to masses of ~0.1 M⊙. Combined with the sub-mm sources, this yields a surface number density of such YSOs of N* ~ 103pc-2 within a projected radius of about 0.1 pc. Such a value is similar to those predicted by models of both core accretion from a turbulent clump environment and competitive accretion. The radial profile of N* is relatively flat on scales out to 0.2 pc, with only modest enhancement around the massive protostar inside 0.05 pc, which provides additional constraints on these massive star formation models. Conclusions. This study demonstrates the utility of high-resolution NIR imaging, in particular with AO, for detecting outflow activity and YSOs in distant regions. The presented images reveal the complex morphology of outflow-shocked gas within the large-scale bipolar flow of a massive protostar, as well as clear evidence for several other outflow driving sources in the region. Finally, this work presents a novel approach to compare the observed YSO surface number density from our study against different models of massive star formation.
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| 23. |
- Elia, Davide, et al.
(författare)
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The Hi-GAL compact source catalogue - II. The 360° catalogue of clump physical properties
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 504:2, s. 2742-2766
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Tidskriftsartikel (refereegranskat)abstract
- We present the 360° catalogue of physical properties of Hi-GAL compact sources, detected between 70 and 500 $\mu$m. This release not only completes the analogous catalogue previously produced by the Hi-GAL collaboration for -71° 2 á 2 67°, but also meaningfully improves it because of a new set of heliocentric distances, 120 808 in total. About a third of the 150 223 entries are located in the newly added portion of the Galactic plane. A first classification based on detection at 70 $\mu$m as a signature of ongoing star-forming activity distinguishes between protostellar sources (23 per cent of the total) and starless sources, with the latter further classified as gravitationally bound (pre-stellar) or unbound. The integral of the spectral energy distribution, including ancillary photometry from λ = 21 to 1100 $\mu$m, gives the source luminosity and other bolometric quantities, while a modified blackbody fitted to data for $\lambda \ge 160∼\mu$m yields mass and temperature. All tabulated clump properties are then derived using photometry and heliocentric distance, where possible. Statistics of these quantities are discussed with respect to both source Galactic location and evolutionary stage. No strong differences in the distributions of evolutionary indicators are found between the inner and outer Galaxy. However, masses and densities in the inner Galaxy are on average significantly larger, resulting in a higher number of clumps that are candidates to host massive star formation. Median behaviour of distance-independent parameters tracing source evolutionary status is examined as a function of the Galactocentric radius, showing no clear evidence of correlation with spiral arm positions.
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| 24. |
- Farias Osses, Juan Pablo, 1987, et al.
(författare)
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Hunting for Runaways from the Orion Nebula Cluster
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 900:1
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Tidskriftsartikel (refereegranskat)abstract
- We use Gaia DR2 to hunt for runaway stars from the Orion Nebula Cluster (ONC). We search a region extending 45 degrees around the ONC and out to 1 kpc to find sources that have overlapped in angular position with the cluster in the last similar to 10 Myr. We find similar to 17,000 runaway/walkaway candidates that satisfy this 2D traceback condition. Most of these are expected to be contaminants, e.g., caused by Galactic streaming motions of stars at different distances. We thus examine six further tests to help identify real runaways, namely: (1) possessing young stellar object (YSO) colors and magnitudes based on Gaia optical photometry; (2) having IR excess consistent with YSOs based on 2MASS and Wide-field Infrared Survey Explorer photometry; (3) having a high degree of optical variability; (4) having closest approach distances well-constrained to within the cluster half-mass radius; (5) having ejection directions that avoid the main Galactic streaming contamination zone; and (6) having a required radial velocity (RV) for 3D overlap of reasonable magnitude (or, for the 7% of candidates with measured RVs, satisfying 3D traceback). Thirteen sources, not previously noted as Orion members, pass all these tests, while another twelve are similarly promising, except they are in the main Galactic streaming contamination zone. Among these 25 ejection candidates, ten with measured RVs pass the most restrictive 3D traceback condition. We present full lists of runaway/walkaway candidates, estimate the high-velocity population ejected from the ONC, and discuss its implications for cluster formation theories via comparison with numerical simulations.
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| 25. |
- Farias Osses, Juan Pablo, 1987, et al.
(författare)
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Star cluster formation from turbulent clumps – III. Across the mass spectrum
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 523:2, s. 2083-2110
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Tidskriftsartikel (refereegranskat)abstract
- We study the formation and early evolution of star clusters that have a wide range of masses and background cloud mass surface densities, ∑cloud, which help set the initial sizes, densities, and velocity dispersions of the natal gas clumps. Initial clump masses of 300, 3000, and 30 000 M☉ are considered, from which star clusters are born with an assumed 50 per cent overall star formation efficiency and with 50 per cent primordial binarity. This formation is gradual, i.e. with a range of star formation efficiencies per free-fall time from 1 to 100 per cent, so that the formation time can range from 0.7 Myr for low-mass, high-∑cloud clumps to ∼30 Myr for high-mass, low-∑cloud clumps. Within this framework of the turbulent clump model, for a given ∑cloud, clumps of higher mass are of lower initial volume density, but their dynamical evolution leads to higher bound fractions and causes them to form much higher density cluster cores and maintain these densities for longer periods. This results in systematic differences in the evolution of binary properties, degrees of mass segregation, and rates of creation of dynamically ejected runaways. We discuss the implications of these results for observed star clusters and stellar populations.
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| 26. |
- Fedriani, Rubén, 1991, et al.
(författare)
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The sharpest view on the high-mass star-forming region S255IR: Near infrared adaptive optics imaging of the outbursting source NIRS3
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 676
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Massive stars have an impact on their surroundings from early in their formation until the end of their lives. However, very little is known about their formation. Episodic accretion may play a crucial role in the process, but only a handful of observations have reported such events occurring in massive protostars. Aims. We aim to investigate the outburst event from the high-mass star-forming region S255IR where the protostar NIRS3 recently underwent an accretion outburst. We follow the evolution of this source both in photometry and morphology of its surroundings. Methods. We performed near infrared adaptive optics observations on the S255IR central region using the Large Binocular Telescope in the Ks broadband as well as the H2 and Brγ narrow-band filters with an angular resolution of 07.06, close to the diffraction limit. Results. We discovered a new near infrared knot north-east of NIRS3 that we interpret as a jet knot that was ejected during the last accretion outburst and observed in the radio regime as part of a follow-up after the outburst. We measured a mean tangential velocity for this knot of 450 ± 50 km s1. We analysed the continuum-subtracted images from H2, which traces jet-shocked emission, and Brγ, which traces scattered light from a combination of accretion activity and UV radiation from the central massive protostar. We observed a significant decrease in flux at the location of NIRS3, with K = 13.48 mag being the absolute minimum in the historic series. Conclusions. Our observations strongly suggest a scenario where the episodic accretion is followed by an episodic ejection response in the near infrared, as was seen in the earlier radio follow-up. The ~2 μm photometry from the past 30 yr suggests that NIRS3 might have undergone another outburst in the late 1980s, making it the first massive protostar with such evidence observed in the near infrared.
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| 27. |
- Fedriani, Rubén, 1991, et al.
(författare)
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The SOFIA Massive (SOMA) Star Formation Survey. IV. Isolated Protostars
- 2023
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 942:1
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Tidskriftsartikel (refereegranskat)abstract
- We present similar to 10-40 mu m SOFIA-FORCAST images of 11 isolated protostars as part of the SOFIA Massive (SOMA) Star Formation Survey, with this morphological classification based on 37 mu m imaging. We develop an automated method to define source aperture size using the gradient of its background-subtracted enclosed flux and apply this to build spectral energy distributions (SEDs). We fit the SEDs with radiative transfer models, developed within the framework of turbulent core accretion (TCA) theory, to estimate key protostellar properties. Here, we release the sedcreator python package that carries out these methods. The SEDs are generally well fitted by the TCA models, from which we infer initial core masses M ( c ) ranging from 20-430 M (circle dot), clump mass surface densities sigma(cl) similar to 0.3-1.7 g cm(-2), and current protostellar masses m (*) similar to 3-50 M (circle dot). From a uniform analysis of the 40 sources in the full SOMA survey to date, we find that massive protostars form across a wide range of clump mass surface density environments, placing constraints on theories that predict a minimum threshold sigma(cl) for massive star formation. However, the upper end of the m (*)-sigma(cl) distribution follows trends predicted by models of internal protostellar feedback that find greater star formation efficiency in higher sigma(cl) conditions. We also investigate protostellar far-IR variability by comparison with IRAS data, finding no significant variation over an similar to 40 yr baseline.
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| 28. |
- Fontani, F., et al.
(författare)
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ALMA-IRDC - II. First high-angular resolution measurements of the N-14/N-15 ratio in a large sample of infrared-dark cloud cores
- 2021
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 503:3, s. 4320-4335
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Tidskriftsartikel (refereegranskat)abstract
- The N-14/N-15 ratio in molecules exhibits a large variation in star-forming regions, especially when measured from N2H+ isotopologues. However, there are only a few studies performed at high-angular resolution. We present the first interferometric survey of the N-14/N-15 ratio in N2H+ obtained with Atacama Large Millimeter Array observations towards four infrared-dark clouds harbouring 3 mm continuum cores associated with different physical properties. We detect (NNH+)-N-15 (1-0) in of the cores, depending on the host cloud. The N-14/N-15 values measured towards the millimetre continuum cores range from a minimum of similar to 80 up to a maximum of similar to 400. The spread of values is narrower than that found in any previous single-dish survey of high-mass star-forming regions and than that obtained using the total power data only. This suggests that the N-14/N-15 ratio is on average higher in the diffuse gaseous envelope of the cores and stresses the need for high-angular resolution maps to measure correctly the N-14/N-15 ratio in dense cores embedded in IRDCs. The average N-14/N-15 ratio of similar to 210 is also lower than the interstellar value at the Galactocentric distance of the clouds (similar to 300-330), although the sensitivity of our observations does not allow us to unveil N-14/N-15 ratios higher than similar to 400. No clear trend is found between the N-14/N-15 ratio and the core physical properties. We find only a tentative positive trend between N-14/N-15 and H-2 column density. However, firmer conclusions can be drawn only with higher sensitivity measurements.
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| 29. |
- Gardiner, Emiko C., et al.
(författare)
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Disk Wind Feedback from High-mass Protostars. IV. Shock-ionized Jets
- 2024
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 967:2
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Tidskriftsartikel (refereegranskat)abstract
- Massive protostars launch accretion-powered, magnetically collimated outflows, which play crucial roles in the dynamics and diagnostics of the star formation process. Here we calculate the shock heating and resulting free-free radio emission in numerical models of outflows of massive star formation within the framework of the Turbulent Core Accretion model. We postprocess 3D magnetohydrodynamic simulation snapshots of a protostellar disk wind interacting with an infalling core envelope, and calculate shock temperatures, ionization fractions, and radio free-free emission. We find heating up to ∼107 K and near-complete ionization in shocks at the interface between the outflow cavity and infalling envelope. However, line-of-sight averaged ionization fractions peak around ∼10%, in agreement with values reported from observations of massive protostar G35.20-0.74N. By calculating radio-continuum fluxes and spectra, we compare our models with observed samples of massive protostars. We find our fiducial models produce radio luminosities similar to those seen from low- and intermediate-mass protostars that are thought to be powered by shock ionization. Comparing to more massive protostars, we find our model radio luminosities are ∼10-100 times less luminous. We discuss how this apparent discrepancy either reflects aspects of our modeling related to the treatment of cooling of the post-shock gas or a dominant contribution in the observed systems from photoionization. Finally, our models exhibit 10 yr radio flux variability of ∼5%, especially in the inner 1000 au region, comparable to observed levels in some hypercompact H ii regions.
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| 30. |
- Garg, Kritika M., et al.
(författare)
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When colors mislead : Genomics and bioacoustics prompt re-classification of Asian flycatcher radiation (Aves: Niltavinae)
- 2024
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier. - 1055-7903 .- 1095-9513. ; 193
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Tidskriftsartikel (refereegranskat)abstract
- Traditional classification of many animals, including birds, has been highly dependent on external morphological characters like plumage coloration. However, both bioacoustics and genetic or genomic data have revolutionized our understanding of the relationships of certain lineages and led to sweeping taxonomic re-organizations. In this study, we present a case of erroneous delimitation of genus boundaries in the species-rich flycatcher subfamily Niltavinae. Genera within this subfamily have historically been delineated based on blue versus brown male body plumage until recent studies based on a few mitochondrial and nuclear loci unearthed several cases of generic misclassification. Here we use extensive bioacoustic data from 43 species and genomic data from 28 species for a fundamental reclassification of species in the Niltavinae. Our study reveals that song is an important trait to classify these birds even at the genus level, whereas plumage traits exhibit ample convergence and have led to numerous historic misattributions. Our taxonomic re-organization leads to new biogeographic limits of major genera, such that the genus Cyornis now only extends as far east as the islands of Sulawesi, Sula, and Banggai, whereas Eumyias is redefined to extend far beyond Wallace's Line to the islands of Seram and Timor. Our conclusions advise against an over-reliance on morphological traits and underscore the importance of integrative datasets.
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| 31. |
- Gorai, Prasanta, 1991, et al.
(författare)
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Astrochemical Diagnostics of the Isolated Massive Protostar G28.20-0.05
- 2024
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 960:2
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Tidskriftsartikel (refereegranskat)abstract
- We study the astrochemical diagnostics of the isolated massive protostar G28.20-0.05. We analyze data from Atacama Large Millimeter/submillimeter Array 1.3 mm observations with a resolution of 0.″2 (∼1000 au). We detect emission from a wealth of species, including oxygen-bearing (e.g., H2CO, CH3OH, CH3OCH3), sulfur-bearing (SO2, H2S), and nitrogen-bearing (e.g., HNCO, NH2CHO, C2H3CN, C2H5CN) molecules. We discuss their spatial distributions, physical conditions, correlation between different species, and possible chemical origins. In the central region near the protostar, we identify three hot molecular cores (HMCs). HMC1 is part of a millimeter continuum ring-like structure, is closest in projection to the protostar, has the highest temperature of ∼300 K, and shows the most line-rich spectra. HMC2 is on the other side of the ring, has a temperature of ∼250 K, and is of intermediate chemical complexity. HMC3 is further away, ∼3000 au in projection, cooler (∼70 K), and is the least line-rich. The three HMCs have similar mass surface densities (∼10 g cm−2), number densities (n H ∼ 109 cm−3), and masses of a few solar masses. The total gas mass in the cores and in the region out to 3000 au is ∼25 M ⊙, which is comparable to that of the central protostar. Based on spatial distributions of peak line intensities as a function of excitation energy, we infer that the HMCs are externally heated by the protostar. We estimate column densities and abundances of the detected species and discuss the implications for hot core astrochemistry.
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| 32. |
- Hsu, Chia-Jung, 1991, et al.
(författare)
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Deuterium Chemodynamics of Massive Pre-Stellar Cores
- 2021
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 502:1, s. 1104-1127
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Tidskriftsartikel (refereegranskat)abstract
- High levels of deuterium fractionation of $\rm N_2H^+$ (i.e., $\rm D_{frac}^{N_2H^+} = 0.1$) are often observed in pre-stellar cores (PSCs) and detection of $\rm N_2D^+$ is a promising method to identify elusive massive PSCs. However, the physical and chemical conditions required to reach such high levels of deuteration are still uncertain, as is the diagnostic utility of $\rm N_2H^+$ and $\rm N_2D^+$ observations of PSCs. We perform 3D magnetohydrodynamics simulations of a massive, turbulent, magnetised PSC, coupled with a sophisticated deuteration astrochemical network. Although the core has some magnetic/turbulent support, it collapses under gravity in about one freefall time, which marks the end of the simulations. Our fiducial model achieves relatively low $\rm D_{frac}^{N_2H^+} \sim0.002$ during this time. We then investigate effects of initial ortho-para ratio of $\rm H_2$ ($\rm OPR^{H_2}$), temperature, cosmic ray (CR) ionization rate, CO and N-species depletion factors and prior PSC chemical evolution. We find that high CR ionization rates and high depletion factors allow the simulated $\rm D_{frac}^{N_2H^+}$ and absolute abundances to match observational values within one freefall time. For $\rm OPR^{H_2}$, while a lower initial value helps the growth of $\rm D_{frac}^{N_2H^+}$, the spatial structure of deuteration is too widespread compared to observed systems. For an example model with elevated CR ionization rates and significant heavy element depletion, we then study the kinematic and dynamic properties of the core as traced by its $\rm N_2D^+$ emission. The core, undergoing quite rapid collapse, exhibits disturbed kinematics in its average velocity map. Still, because of magnetic support, the core often appears kinematically sub-virial based on its $\rm N_2D^+$ velocity dispersion.
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| 33. |
- Hsu, Chia-Jung, 1991, et al.
(författare)
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GMC collisions as triggers of star formation – VIII. The core mass function
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 522:1, s. 700-720
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Tidskriftsartikel (refereegranskat)abstract
- Compression in giant molecular cloud (GMC) collisions is a promising mechanism to trigger the formation of massive star clusters and OB associations. We simulate colliding and non-colliding magnetized GMCs and examine the properties of pre-stellar cores, selected from projected mass surface density maps, including after synthetic ALMA observations. We then examine core properties, including mass, size, density, velocity, velocity dispersion, temperature, and magnetic field strength. After 4 Myr, ∼1000 cores have formed in the GMC collision, and the high-mass end of the core mass function (CMF) can be fit by a power-law dN/dlogM ∝ M-α with α ≃ 0.7, i.e. relatively top heavy compared to a Salpeter mass function. Depending on how cores are identified, a break in the power law can appear around a few ×10 M☉. The non-colliding GMCs form fewer cores with a CMF with α ≃ 0.8–1.2, i.e. closer to the Salpeter index. We compare the properties of these CMFs to those of several observed samples of cores. Considering other properties, cores formed from colliding clouds are typically warmer, have more disturbed internal kinematics, and are more likely to be gravitational unbound, than cores formed from non-colliding GMCs. The dynamical state of the protocluster of cores formed in the GMC–GMC collision is intrinsically subvirial but can appear to be supervirial if the total mass measurement is affected by observations that miss mass on large scales or at low densities.
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| 34. |
- Jankovic, Marija R., et al.
(författare)
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MRI-active inner regions of protoplanetary discs. I. A detailed model of disc structure
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 504:1, s. 280-299
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Tidskriftsartikel (refereegranskat)abstract
- Short-period super-Earth-sized planets are common. Explaining how they form near their present orbits requires understanding the structure of the inner regions of protoplanetary discs. Previous studies have argued that the hot inner protoplanetary disc is unstable to the magnetorotational instability (MRI) due to thermal ionization of potassium, and that a local gas pressure maximum forms at the outer edge of this MRI-active zone. Here we present a steady-state model for inner discs accreting viscously, primarily due to the MRI. The structure and MRI-viscosity of the inner disc are fully coupled in our model; moreover, we account for many processes omitted in previous such models, including disc heating by both accretion and stellar irradiation, vertical energy transport, realistic dust opacities, dust effects on disc ionization, and non-thermal sources of ionization. For a disc around a solar-mass star with a standard gas accretion rate (dot M∼, 10-8 M· yr-1) and small dust grains, we find that the inner disc is optically thick, and the accretion heat is primarily released near the mid-plane. As a result, both the disc mid-plane temperature and the location of the pressure maximum are only marginally affected by stellar irradiation, and the inner disc is also convectively unstable. As previously suggested, the inner disc is primarily ionized through thermionic and potassium ion emission from dust grains, which, at high temperatures, counteract adsorption of free charges on to grains. Our results show that the location of the pressure maximum is determined by the threshold temperature above which thermionic and ion emission become efficient.
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| 35. |
- Jankovic, Marija R., et al.
(författare)
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MRI-active inner regions of protoplanetary discs - II. Dependence on dust, disc, and stellar parameters
- 2022
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 509:4, s. 5974-5991
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Tidskriftsartikel (refereegranskat)abstract
- Close-in super-Earths are the most abundant exoplanets known. It has been hypothesized that they form in the inner regions of protoplanetary discs, out of the dust that may accumulate at the boundary between the inner region susceptible to the magneto-rotational instability (MRI) and an MRI-dead zone further out. In Paper I, we presented a model for the viscous inner disc which includes heating due to both irradiation and MRI-driven accretion; thermal and non-thermal ionization; dust opacities; and dust effects on ionization. Here, we examine how the inner disc structure varies with stellar, disc, and dust parameters. For high accretion rates and small dust grains, we find that: (1) the main sources of ionization are thermal ionization and thermionic and ion emission; (2) the disc features a hot, high-viscosity inner region, and a local gas pressure maximum at the outer edge of this region (in line with previous studies); and (3) an increase in the dust-to-gas ratio pushes the pressure maximum outwards. Consequently, dust can accumulate in such inner discs without suppressing the MRI, with the amount of accumulation depending on the viscosity in the MRI-dead regions. Conversely, for low accretion rates and large dust grains, there appears to be an additional steady-state solution in which: (1) stellar X-rays become the main source of ionization; (2) MRI-viscosity is high throughout the disc; and (3) the pressure maximum ceases to exist. Hence, if planets form in the inner disc, larger accretion rates (and thus younger discs) are favoured.
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| 36. |
- Koda, Jin, et al.
(författare)
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On the Lifetime of Molecular Clouds with the “Tuning-fork” Analysis
- 2023
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 959:1
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Tidskriftsartikel (refereegranskat)abstract
- The “tuning-fork” (TF) analysis of CO and Hα emission has been used to estimate the lifetimes of molecular clouds in nearby galaxies. With simple model calculations, we show that this analysis does not necessarily estimate cloud lifetimes, but instead captures a duration of the cloud evolutionary cycle, from dormant to star-forming, and then back to a dormant phase. We adopt a hypothetical setup in which molecular clouds (e.g., traced in CO) live forever and form stars (e.g., H ii regions) at some frequency, which then drift away from the clouds. The TF analysis still returns a timescale for the immortal clouds. This model requires drifting motion to separate the newborn stars from the clouds, and we discuss its origin. We also discuss the physical origin of the characteristic spatial separation term in the TF analysis and a bias due to systematic error in the determination of the reference timescale.
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| 37. |
- Lahrouchi, Najim, et al.
(författare)
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Transethnic Genome-Wide Association Study Provides Insights in the Genetic Architecture and Heritability of Long QT Syndrome
- 2020
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Ingår i: Circulation. - : Lippincott Williams & Wilkins. - 0009-7322 .- 1524-4539. ; 142:4, s. 324-338
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Tidskriftsartikel (refereegranskat)abstract
- Background: Long QT syndrome (LQTS) is a rare genetic disorder and a major preventable cause of sudden cardiac death in the young. A causal rare genetic variant with large effect size is identified in up to 80% of probands (genotype positive) and cascade family screening shows incomplete penetrance of genetic variants. Furthermore, a proportion of cases meeting diagnostic criteria for LQTS remain genetically elusive despite genetic testing of established genes (genotype negative). These observations raise the possibility that common genetic variants with small effect size contribute to the clinical picture of LQTS. This study aimed to characterize and quantify the contribution of common genetic variation to LQTS disease susceptibility. Methods: We conducted genome-wide association studies followed by transethnic meta-analysis in 1656 unrelated patients with LQTS of European or Japanese ancestry and 9890 controls to identify susceptibility single nucleotide polymorphisms. We estimated the common variant heritability of LQTS and tested the genetic correlation between LQTS susceptibility and other cardiac traits. Furthermore, we tested the aggregate effect of the 68 single nucleotide polymorphisms previously associated with the QT-interval in the general population using a polygenic risk score. Results: Genome-wide association analysis identified 3 loci associated with LQTS at genome-wide statistical significance (P<5x10(-8)) nearNOS1AP,KCNQ1, andKLF12, and 1 missense variant inKCNE1(p.Asp85Asn) at the suggestive threshold (P<10(-6)). Heritability analyses showed that approximate to 15% of variance in overall LQTS susceptibility was attributable to common genetic variation (h2SNP0.148; standard error 0.019). LQTS susceptibility showed a strong genome-wide genetic correlation with the QT-interval in the general population (r(g)=0.40;P=3.2x10(-3)). The polygenic risk score comprising common variants previously associated with the QT-interval in the general population was greater in LQTS cases compared with controls (P<10-13), and it is notable that, among patients with LQTS, this polygenic risk score was greater in patients who were genotype negative compared with those who were genotype positive (P<0.005). Conclusions: This work establishes an important role for common genetic variation in susceptibility to LQTS. We demonstrate overlap between genetic control of the QT-interval in the general population and genetic factors contributing to LQTS susceptibility. Using polygenic risk score analyses aggregating common genetic variants that modulate the QT-interval in the general population, we provide evidence for a polygenic architecture in genotype negative LQTS.
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| 38. |
- Law, Chi Yan, 1990, et al.
(författare)
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Isolated Massive Star Formation in G28.20-0.05
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 939:2
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Tidskriftsartikel (refereegranskat)abstract
- We report high-resolution 1.3 mm continuum and molecular line observations of the massive protostar G28.20-0.05 with Atacama Large Millimeter/submillimeter Array. The continuum image reveals a ring-like structure with 2000 au radius, similar to morphology seen in archival 1.3 cm Very Large Array observations. Based on its spectral index and associated H30α emission, this structure mainly traces ionized gas. However, there is evidence for ∼30 M ⊙ of dusty gas near the main millimeter continuum peak on one side of the ring, as well as in adjacent regions within 3000 au. A virial analysis on scales of ∼2000 au from hot core line emission yields a dynamical mass of ∼80 M ⊙. A strong velocity gradient in the H30α emission is evidence for a rotating, ionized disk wind, which drives a larger-scale molecular outflow. An infrared spectral energy distribution (SED) analysis indicates a current protostellar mass of m * ∼ 40 M ⊙ forming from a core with initial mass M c ∼ 300 M ⊙ in a clump with mass surface density of Σcl ∼ 0.8 g cm−2. Thus the SED and other properties of the system can be understood in the context of core accretion models. A structure-finding analysis on the larger-scale continuum image indicates G28.20-0.05 is forming in a relatively isolated environment, with no other concentrated sources, i.e., protostellar cores, above ∼1 M ⊙ found from ∼0.1 to 0.4 pc around the source. This implies that a massive star can form in relative isolation, and the dearth of other protostellar companions within the ∼1 pc environs is a strong constraint on massive star formation theories that predict the presence of a surrounding protocluster.
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| 39. |
- Lim, Wanggi, et al.
(författare)
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Star cluster formation in Orion A
- 2021
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 73, s. S239-S255
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Tidskriftsartikel (refereegranskat)abstract
- We introduce new analysis methods for studying the star cluster formation processes in Orion A, especially examining the scenario of a cloud-cloud collision. We utilize the CARMA-NRO Orion survey (CO)-C-13 (1-0) data to compare molecular gas to the properties of young stellar objects from the SDSS III IN-SYNC survey. We show that the increase of v(13CO) - v(YSO) and Sigma scatter of older YSOs can be signals of cloud-cloud collision. SOFIA-upGREAT 158 mu m [C II] archival data toward the northern part of Orion A are also compared to the (CO)-C-13 data to test whether the position and velocity offsets between the emission from these two transitions resemble those predicted by a cloud-cloud collision model. We find that the northern part of Orion A, including regions ONC-OMC-1, OMC-2, OMC-3, and OMC-4, shows qualitative agreements with the cloud-cloud collision scenario, while in one of the southern regions, NGC 1999, there is no indication of such a process in causing the birth of new stars. On the other hand, another southern cluster, L 1641 N, shows slight tendencies of cloud-cloud collision. Overall, our results support the cloud-cloud collision process as being an important mechanism for star cluster formation in Orion A.
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| 40. |
- Liu, Mengyao, et al.
(författare)
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SiO Outflows as Tracers of Massive Star Formation in Infrared Dark Clouds
- 2021
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 921:1
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Tidskriftsartikel (refereegranskat)abstract
- To study the early phases of massive star formation, we present ALMA observations of SiO(5-4) emission and VLA observations of 6 cm continuum emission toward 32 Infrared Dark Cloud clumps, spatially resolved down to less than or similar to 0.05 pc. Out of the 32 clumps, we detect SiO emission in 20 clumps, and in 11 of them the SiO emission is relatively strong and likely tracing protostellar outflows. Some SiO outflows are collimated, while others are less ordered. For the six strongest SiO outflows, we estimate basic outflow properties. In our entire sample, where there is SiO emission, we find 1.3 mm continuum and infrared emission nearby, but not vice versa. We build the spectral energy distributions (SEDs) of cores with 1.3 mm continuum emission and fit them with radiative transfer models. The low luminosities and stellar masses returned by SED fitting suggest these are early-stage protostars. We see a slight trend of increasing SiO line luminosity with bolometric luminosity, which suggests more powerful shocks in the vicinity of more massive YSOs. We do not see a clear relation between the SiO luminosity and the evolutionary stage indicated by L/M. We conclude that, as a protostar approaches a bolometric luminosity of similar to 10(2) L (circle dot), the shocks in the outflow are generally strong enough to form SiO emission. The VLA 6 cm observations toward the 15 clumps with the strongest SiO emission detect emission in four clumps, which is likely from shock-ionized jets associated with the more massive ones of these protostellar cores.
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| 41. |
- Liu, Mengyao, et al.
(författare)
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The SOFIA Massive (SOMA) Star Formation Survey. III. From Intermediate- to High-mass Protostars
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 904:1
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Tidskriftsartikel (refereegranskat)abstract
- We present similar to 10-40 mm SOFIA-FORCAST images of 14 intermediate-mass protostar candidates as part of the SOFIA Massive (SOMA) Star Formation Survey. We build spectral energy distributions, also using archival Spitzer, Herschel, and IRAS data. We then fit the spectral energy distributions with radiative transfer models of Zhang & Tan, based on turbulent core accretion theory, to estimate key protostellar properties. With the addition of these intermediate-mass sources, based on average properties derived from SED fitting, SOMA protostars span luminosities from similar to 10(2) to 10(6) L-circle dot, current protostellar masses from similar to 0.5 to 35 M-circle dot, and ambient clump mass surface densities, Scl, from 0.1 to g cm(-2). A wide range of evolutionary states of the individual protostars and of the protocluster environments is also probed. We have also considered about 50 protostars identified in infrared dark clouds that are expected to be at the earliest stages of their evolution. With this global sample, most of the evolutionary stages of high- and intermediate-mass protostars are probed. The best-fitting models show no evidence that a threshold value of the protocluster clump mass surface density is required to form protostars up to similar to 25 M.. However, to form more massive protostars, there is tentative evidence that Sigma(cl) needs to be greater than or similar to 1 g cm(-2). We discuss how this is consistent with expectations from core accretion models that include internal feedback from the forming massive star.
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| 42. |
- Mondal, Suman Kumar, et al.
(författare)
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Is There Any Linkage between Interstellar Aldehyde and Alcohol?
- 2021
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 922:2
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Tidskriftsartikel (refereegranskat)abstract
- It is speculated that there might be some linkage between interstellar aldehydes and their corresponding alcohols. Here an observational study and astrochemical modeling are coupled together to illustrate the connection between them. The ALMA cycle 4 data of a hot molecular core, G10.47+0.03, are utilized for this study. Various aldehydes (acetaldehyde, propanal, and glycolaldehyde), alcohols (methanol and ethylene glycol), and a ketone (acetone) are identified in this source. The excitation temperatures and column densities of these species were derived via the rotation diagram method assuming local thermodynamic equilibrium conditions. An extensive investigation is carried out to understand the formation of these species. Six pairs of aldehyde-alcohol are considered for this study: (i) methanal and methanol, (ii) ethanal and ethanol, (iii) propanal and 1-propanol, (iv) propenal and allyl alcohol, (v) propynal and propargyl alcohol, and (vi) glycolaldehyde and ethylene glycol. One pair of ketone-alcohol (acetone and isopropanol) and ketene-alcohol (ethenone and vinyl alcohol) are also considered. Two successive hydrogenation reactions in the ice phase are examined to form these alcohols from aldehydes, ketone, and ketene, respectively. Quantum chemical methods are extensively executed to review the ice-phase formation route and the kinetics of these species. Based on the obtained kinetic data, astrochemical modeling is employed to derive the abundances of these aldehydes, alcohols, ketone, and ketene in this source. It is seen that our model could successfully explain the observed abundances of various species in this hot molecular core.
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| 43. |
- Morello, Giuseppe, 1989, et al.
(författare)
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Spitzer thermal phase curve of WASP-121 b
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 676
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We analyse unpublished Spitzer observations of the thermal phase-curve of WASP-121 b, a benchmark ultra-hot Jupiter. Methods. We adopted the wavelet pixel-independent component analysis technique to remove challenging instrumental systematic effects in these datasets and we fit them simultaneously with parametric light-curve models. We also performed phase-curve retrievals to better understand the horizontal and vertical thermal structure of the planetary atmosphere. Results. We measured planetary brightness temperatures of ~2700 K (dayside) and ~700 1100 K (nightside), along with modest peak offsets of 5.9 ± 1.6 (3.6 μm) and 5.0 3.1+3.4 (4.5 μm) after mid-eclipse. These results suggest inefficient heat redistribution in the atmosphere of WASP-121 b. The inferred atmospheric Bond albedo and circulation efficiency align well with observed trends for hot giant exoplanets. Interestingly, the measured peak offsets correspond to a westward hot spot, which has rarely been observed. We also report consistent transit depths at 3.6 and 4.5 μm, along with updated geometric and orbital parameters. Finally, we compared our Spitzer results with previous measurements, including recent JWST observations. Conclusions. We extracted new information on the thermal properties and dynamics of an exoplanet atmosphere from an especially problematic dataset. This study probes the reliability of exoplanet phase-curve parameters obtained from Spitzer observations when state-of-the-art pipelines are adopted to remove the instrumental systematic effects. It demonstrates that Spitzer phase-curve observations provide a useful baseline for comparison with JWST observations, and shows the increase in parameters precision achieved with the newer telescope.
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| 44. |
- Moser, Emily, et al.
(författare)
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The High-mass Protostellar Population of a Massive Infrared Dark Cloud
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 897:2
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Tidskriftsartikel (refereegranskat)abstract
- We conduct a census of the high-mass protostellar population of the similar to 70,000Minfrared dark cloud (IRDC) G028.37+00.07, identifying 35 sources based on their 70 mu m emission, as reported in the Herschel Hi-GAL catalog of Molinari et al. We perform aperture photometry to construct spectral energy distributions, which are then fit with the massive protostar models of Zhang & Tan. We find that the sources span a range of isotropic luminosities from similar to 20 to 4500L. The most luminous sources are predicted to have current protostellar masses ofm(*) similar to 10Mforming from cores of massM(c) similar to 40 to 400M. The least luminous sources in our sample are predicted to be protostars with masses as low as similar to 0.5Mforming from cores withM(c) similar to 10M, which are the minimum values explored in the protostellar model grid. The detected protostellar population has a total estimated protostellar mass ofM(*) similar to 100M. Allowing for completeness corrections, which are constrained by comparison with an ALMA study in part of the cloud, we estimate a star formation efficiency per freefall time of similar to 3% in the IRDC. Finally, analyzing the spatial distribution of the sources, we find relatively low degrees of central concentration of the protostars. The protostars, including the most massive ones, do not appear to be especially centrally concentrated in the protocluster as defined by the IRDC boundary.
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| 45. |
- Nôga, Diana Aline, 1989-, et al.
(författare)
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Habitual Short Sleep Duration, Diet, and Development of Type 2 Diabetes in Adults
- 2024
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Ingår i: JAMA Network Open. - : American Medical Association (AMA). - 2574-3805. ; 7:3
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Tidskriftsartikel (refereegranskat)abstract
- IMPORTANCE: Understanding the interplay between sleep duration, dietary habits, and the risk of developing type 2 diabetes (T2D) is crucial for public health and diabetes prevention strategies.OBJECTIVE: To investigate the associations of type of diet and duration of sleep with the development of T2D.DESIGN, SETTING, AND PARTICIPANTS: Data derived from the UK Biobank baseline investigation (2006-2010) were analyzed for this cohort study between May 1 and September 30, 2023. The association between sleep duration and healthy dietary patterns with the risk of T2D was investigated during a median (IQR) follow-up of 12.5 (11.8-13.2) years (end of follow-up, September 30, 2021).EXPOSURE: For the analysis, 247 867 participants were categorized into 4 sleep duration groups: normal (7-8 hours per day), mild short (6 hours per day), moderate short (5 hours per day), and extreme short (3-4 hours per day). Their dietary habits were evaluated based on population-specific consumption of red meat, processed meat, fruits, vegetables, and fish, resulting in a healthy diet score ranging from 0 (unhealthiest) to 5 (healthiest).MAIN OUTCOMES AND MEASURES: Cox proportional hazards regression analysis was used to calculate hazard ratios (HRs) and 95% CIs for the development of T2D across various sleep duration groups and healthy diet scores.RESULTS: The cohort comprised 247 867 participants with a mean [SD] age of 55.9 [8.1] years, of whom 52.3% were female. During the follow-up, 3.2% of participants were diagnosed with T2D based on hospital registry data. Cox regression analysis, adjusted for confounding variables, indicated a significant increase in the risk of T2D among participants with 5 hours or less of daily sleep. Individuals sleeping 5 hours per day exhibited a 1.16 adjusted HR (95% CI, 1.05-1.28), and individuals sleeping 3 to 4 hours per day exhibited a 1.41 adjusted HR (95% CI, 1.19-1.68) compared with individuals with normal sleep duration. Furthermore, individuals with the healthiest dietary patterns had a reduced risk of T2D (HR, 0.75 [95% CI, 0.63-0.88]). The association between short sleep duration and increased risk of T2D persisted even for individuals following a healthy diet, but there was no multiplicative interaction between sleep duration and healthy diet score.CONCLUSIONS AND RELEVANCE: In this cohort study involving UK residents, habitual short sleep duration was associated with increased risk of developing T2D. This association persisted even among participants who maintained a healthy diet. To validate these findings, further longitudinal studies are needed, incorporating repeated measures of sleep (including objective assessments) and dietary habits.
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| 46. |
- Okuda, Kazuhide S., et al.
(författare)
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3,4-Difluorobenzocurcumin Inhibits Vegfc-Vegfr3-Erk Signalling to Block Developmental Lymphangiogenesis in Zebrafish
- 2021
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Ingår i: Pharmaceuticals. - : MDPI. - 1424-8247. ; 14:7
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Tidskriftsartikel (refereegranskat)abstract
- Lymphangiogenesis, the formation of new lymphatic vessels from pre-existing vasculature, plays critical roles in disease, including in cancer metastasis and chronic inflammation. Preclinical and recent clinical studies have now demonstrated therapeutic utility for several anti-lymphangiogenic agents, but optimal agents and efficacy in different settings remain to be determined. We tested the anti-lymphangiogenic property of 3,4-Difluorobenzocurcumin (CDF), which has previously been implicated as an anti-cancer agent, using zebrafish embryos and cultured vascular endothelial cells. We used transgenic zebrafish labelling the lymphatic system and found that CDF potently inhibits lymphangiogenesis during embryonic development. We also found that the parent compound, Curcumin, does not inhibit lymphangiogenesis. CDF blocked lymphatic and venous sprouting, and lymphatic migration in the head and trunk of the embryo. Mechanistically, CDF impaired VEGFC-VEGFR3-ERK signalling in vitro and in vivo. In an in vivo pathological model of Vegfc-overexpression, treatment with CDF rescued endothelial cell hyperplasia. CDF did not inhibit the kinase activity of VEGFR3 yet displayed more prolonged activity in vivo than previously reported kinase inhibitors. These findings warrant further assessment of CDF and its mode of action as a candidate for use in metastasis and diseases of aberrant lymphangiogenesis.
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| 47. |
- O'Neill, Theo J., et al.
(författare)
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The Core Mass Function across Galactic Environments. III. Massive Protoclusters
- 2021
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 916:1
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Tidskriftsartikel (refereegranskat)abstract
- The stellar initial mass function (IMF) is fundamental for many areas of astrophysics, but its origin remains poorly understood. It may be inherited from the core mass function (CMF) or arise as a result of more chaotic, competitive accretion. Dense, gravitationally bound cores are seen in molecular clouds and some observations have suggested that the CMF is similar in shape to the IMF, though translated to higher masses by a factor of similar to 3. Here we measure the CMF in 28 dense clumps within 3.5 kpc that are likely to be central regions of massive protoclusters, observed via 1.3 mm dust continuum emission by the ALMAGAL project. We identify 222 cores using the dendrogram algorithm with masses ranging from 0.04 to 252 M-circle dot. We apply completeness corrections for flux and number recovery, estimated from core insertion and recovery experiments. At higher masses, the final derived CMF is well described by a single power law of the form dN/d log M proportional to M-alpha alpha similar or equal to 0.94 +/- 0.08. However, we find evidence of a break in this power-law behavior between similar to 5 and 15 M-circle dot, which is, to our knowledge, the first time such a break has been found in distant (greater than or similar to 1 kpc) regions by the Atacama Large Millimeter/submillimeter Array. We compare this massive protocluster CMF with those derived using the same methods in the G286 protocluster and a sample of infrared dark clouds. The massive protocluster CMF is significantly different, i.e., containing more massive cores, which is a potential indication of the role of environment on the CMF and IMF.
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| 48. |
- Prasad, Ram R. R., et al.
(författare)
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Modulated Self-Assembly of Catalytically Active Metal-Organic Nanosheets Containing Zr6 Clusters and Dicarboxylate Ligands
- 2024
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Ingår i: ACS Applied Materials and Interfaces. - 1944-8244 .- 1944-8252. ; 16:14, s. 17812-17820
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional metal–organic nanosheets (MONs) have emerged as attractive alternatives to their three-dimensional metal–organic framework (MOF) counterparts for heterogeneous catalysis due to their greater external surface areas and higher accessibility of catalytically active sites. Zr MONs are particularly prized because of their chemical stability and high Lewis and Brønsted acidities of the Zr clusters. Herein, we show that careful control over modulated self-assembly and exfoliation conditions allows the isolation of the first example of a two-dimensional nanosheet wherein Zr6 clusters are linked by dicarboxylate ligands. The hxl topology MOF, termed GUF-14 (GUF = Glasgow University Framework), can be exfoliated into monolayer thickness hns topology MONs, and acid-induced removal of capping modulator units yields MONs with enhanced catalytic activity toward the formation of imines and the hydrolysis of an organophosphate nerve agent mimic. The discovery of GUF-14 serves as a valuable example of the undiscovered MOF/MON structural diversity extant in established metal–ligand systems that can be accessed by harnessing the power of modulated self-assembly protocols.
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| 49. |
- Robberto, Massimo, et al.
(författare)
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An HST Study of the Substellar Population of NGC 2024
- 2024
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 960:1
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Tidskriftsartikel (refereegranskat)abstract
- We performed an HST/WFC3-IR imaging survey of the young stellar cluster NGC 2024 in three filters probing the 1.4 mu m H2O absorption feature, characteristic of the population of low-mass and substellar-mass objects down to a few Jupiter masses. We detect 812 point sources, 550 of them in all three filters with signal-to-noise ratio greater than 5. Using a distance-independent two-color diagram, we determine extinction values as high as A V similar or equal to 40. We also find that the change of effective wavelengths in our filters results in higher A V values as the reddening increases. Reconstructing a dereddened color-magnitude diagram, we derive a luminosity histogram both for the full sample of candidate cluster members and for an extinction-limited subsample containing the 50% of sources with A V less than or similar to 15. Assuming a standard extinction law like Cardelli et al. with a nominal R V = 3.1, we produce a luminosity function in good agreement with the one resulting from a Salpeter-like initial mass function for a 1 Myr isochrone. There is some evidence of an excess of luminous stars in the most embedded region. We posit that the correlation may be due to those sources being younger, and therefore overluminous, than the more evolved and less extincted cluster's stars. We compare our classification scheme based on the depth of the 1.4 mu m photometric feature with the results from the spectroscopic survey of Levine et al., and we report a few peculiar sources and morphological features typical of the rich phenomenology commonly encountered in young star-forming regions.
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| 50. |
- Robberto, Massimo, et al.
(författare)
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HST Survey of the Orion Nebula Cluster in the H2O 1.4 μm Absorption Band. I. A Census of Substellar and Planetary-mass Objects
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 896:1
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Tidskriftsartikel (refereegranskat)abstract
- In order to obtain a complete census of the stellar and substellar population, down to a few MJup in the ∼1 Myr old Orion Nebula Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble Space Telescope with the F139M and F130N filters. These bandpasses correspond to the 1.4 μm H2O absorption feature and an adjacent line-free continuum region. Out of 4504 detected sources, 3352 (about 75%) appear fainter than m 130 = 14 (Vega mag) in the F130N filter, a brightness corresponding to the hydrogen-burning limit mass (M ≃ 0.072 M⊙) at ∼1 Myr. Of these, however, only 742 sources have a negative F130M-F139N color index, indicative of the presence of H2O vapor in absorption, and can therefore be classified as bona fide M and L dwarfs, with effective temperatures T ≲ 2850 K at an assumed 1 Myr cluster age. On our color-magnitude diagram (CMD), this population of sources with H2O absorption appears clearly distinct from the larger background population of highly reddened stars and galaxies with positive F130M-F139N color index and can be traced down to the sensitivity limit of our survey, m 130 ≃ 21.5, corresponding to a 1 Myr old ≃3 MJup planetary-mass object under about 2 mag of visual extinction. Theoretical models of the BT-Settl family predicting substellar isochrones of 1, 2, and 3 Myr down to ∼1 MJup fail to reproduce the observed H2O color index at M ≲ 20 MJup. We perform a Bayesian analysis to determine extinction, mass, and effective temperature of each substellar member of our sample, together with its membership probability.
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