| 1. |
- Niemi, MEK, et al.
(author)
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- 2021
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swepub:Mat__t
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| 2. |
- Kanai, M, et al.
(author)
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- 2023
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swepub:Mat__t
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| 3. |
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| 4. |
- Coustenis, A., et al.
(author)
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TandEM : Titan and Enceladus mission
- 2009
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In: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:3, s. 893-946
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Journal article (peer-reviewed)abstract
- TandEM was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini-Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (MontgolfiSre) and possibly several landing probes to be delivered through the atmosphere.
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| 5. |
- Miglio, A., et al.
(author)
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PLATO as it is : A legacy mission for Galactic archaeology
- 2017
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In: Astronomical Notes - Astronomische Nachrichten. - : WILEY-V C H VERLAG GMBH. - 0004-6337 .- 1521-3994. ; 338:6, s. 644-661
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Journal article (peer-reviewed)abstract
- Deciphering the assembly history of the Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps of the Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with a well-defined view of the current chemo-kinematical structure of the Milky Way, but it will only enable a blurred view on the temporal sequence that led to the present-day Galaxy. As demonstrated by the (ongoing) exploitation of data from the pioneering photometric missions CoRoT, Kepler, and K2, asteroseismology provides the way forward: solar-like oscillating giants are excellent evolutionary clocks thanks to the availability of seismic constraints on their mass and to the tight age-initial mass relation they adhere to. In this paper we identify five key outstanding questions relating to the formation and evolution of the Milky Way that will need precise and accurate ages for large samples of stars to be addressed, and we identify the requirements in terms of number of targets and the precision on the stellar properties that are needed to tackle such questions. By quantifying the asteroseismic yields expected from PLATO for red giant stars, we demonstrate that these requirements are within the capabilities of the current instrument design, provided that observations are sufficiently long to identify the evolutionary state and allow robust and precise determination of acoustic-mode frequencies. This will allow us to harvest data of sufficient quality to reach a 10% precision in age. This is a fundamental prerequisite to then reach the more ambitious goal of a similar level of accuracy, which will be possible only if we have at hand a careful appraisal of systematic uncertainties on age deriving from our limited understanding of stellar physics, a goal that conveniently falls within the main aims of PLATO's core science. We therefore strongly endorse PLATO's current design and proposed observational strategy, and conclude that PLATO, as it is, will be a legacy mission for Galactic archaeology.
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| 6. |
- Rousseau-Nepton, L., et al.
(author)
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SIGNALS : I. Survey description
- 2019
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 489:4, s. 5530-5546
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Journal article (peer-reviewed)abstract
- SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, is a large observing programme designed to investigate massive star formation and HII regions in a sample of local extended galaxies. The programme will use the imaging Fourier transform spectrograph SITELLE at the Canada-France-Hawaii Telescope. Over 355 h (54.7 nights) have been allocated beginning in fall 2018 for eight consecutive semesters. Once completed, SIGNALS will provide a statistically reliable laboratory to investigate massive star formation, including over 50 000 resolved HII regions: the largest, most complete, and homogeneous data base of spectroscopically and spatially resolved extragalactic HII regions ever assembled. For each field observed, three datacubes covering the spectral bands of the filters SN1 (363386 nm), SN2 (482-513 nm), and SN3 (647-685 nm) are gathered. The spectral resolution selected for each spectral band is 1000, 1000, and 5000, respectively. As defined, the project sample will facilitate the study of small-scale nebular physics and many other phenomena linked to star formation at a mean spatial resolution of similar to 20 pc. This survey also has considerable legacy value for additional topics, including planetary nebulae, diffuse ionized gas, and supernova remnants. The purpose of this paper is to present a general outlook of the survey, notably the observing strategy, galaxy sample, and science requirements.
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| 7. |
- de Blok, W.J.G., et al.
(author)
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an overview of the MHONGOOSE survey: Observing nearby galaxies with MeerKAT
- 2016
-
In: Proceedings of Science. - 1824-8039.
-
Conference paper (peer-reviewed)abstract
- MHONGOOSE is a deep survey of the neutral hydrogen distribution in a representative sample of 30 nearby disk and dwarf galaxies with H I masses from ∼ 106 to ∼ 1011 M, and luminosities from MR ∼ 12 to MR ∼ −22. The sample is selected to uniformly cover the available range in log(MHI). Our extremely deep observations, down to H I column density limits of well below 1018 cm−2 — or a few hundred times fainter than the typical H I disks in galaxies — will directly detect the effects of cold accretion from the intergalactic medium and the links with the cosmic web. These observations will be the first ever to probe the very low-column density neutral gas in galaxies at these high resolutions. Combination with data at other wavelengths, most of it already available, will enable accurate modeling of the properties and evolution of the mass components in these galaxies and link these with the effects of environment, dark matter distribution, and other fundamental properties such as halo mass and angular momentum. MHONGOOSE can already start addressing some of the SKA-1 science goals and will provide a comprehensive inventory of the processes driving the transformation and evolution of galaxies in the nearby universe at high resolution and over 5 orders of magnitude in column density. It will be a Nearby Galaxies Legacy Survey that will be unsurpassed until the advent of the SKA, and can serve as a highly visible, lasting statement of MeerKAT’s capabilities.
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| 8. |
- Hartley, Philippa, et al.
(author)
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SKA Science Data Challenge 2: analysis and results
- 2023
-
In: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 523:2, s. 1967-1993
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Journal article (peer-reviewed)abstract
- The Square Kilometre Array Observatory (SKAO) will explore the radio sky to new depths in order to conduct transformational science. SKAO data products made available to astronomers will be correspondingly large and complex, requiring the application of advanced analysis techniques to extract key science findings. To this end, SKAO is conducting a series of Science Data Challenges, each designed to familiarize the scientific community with SKAO data and to drive the development of new analysis techniques. We present the results from Science Data Challenge 2 (SDC2), which invited participants to find and characterize 233 245 neutral hydrogen (H i) sources in a simulated data product representing a 2000 h SKA-Mid spectral line observation from redshifts 0.25-0.5. Through the generous support of eight international supercomputing facilities, participants were able to undertake the Challenge using dedicated computational resources. Alongside the main challenge, 'reproducibility awards' were made in recognition of those pipelines which demonstrated Open Science best practice. The Challenge saw over 100 participants develop a range of new and existing techniques, with results that highlight the strengths of multidisciplinary and collaborative effort. The winning strategy - which combined predictions from two independent machine learning techniques to yield a 20 per cent improvement in overall performance - underscores one of the main Challenge outcomes: that of method complementarity. It is likely that the combination of methods in a so-called ensemble approach will be key to exploiting very large astronomical data sets.
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| 9. |
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| 10. |
- Rex, M., et al.
(author)
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The far-infrared/submillimeter properties of galaxies located behind the Bullet cluster
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:Article Number: L13
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Journal article (peer-reviewed)abstract
- The Herschel Lensing Survey (HLS) takes advantage of gravitational lensing by massive galaxy clusters to sample a population of high-redshift galaxies which are too faint to be detected above the confusion limit of current far-infrared/submillimeter telescopes. Measurements from 100-500 mu m bracket the peaks of the far-infrared spectral energy distributions of these galaxies, characterizing their infrared luminosities and star formation rates. We introduce initial results from our science demonstration phase observations, directed toward the Bullet cluster (1E0657-56). By combining our observations with LABOCA 870 mu m and AzTEC 1.1 mm data we fully constrain the spectral energy distributions of 19 MIPS 24 mu m-selected galaxies which are located behind the cluster. We find that their colors are best fit using templates based on local galaxies with systematically lower infrared luminosities. This suggests that our sources are not like local ultra-luminous infrared galaxies in which vigorous star formation is contained in a compact highly dust-obscured region. Instead, they appear to be scaled up versions of lower luminosity local galaxies with star formation occurring on larger physical scales.
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| 11. |
- Kramer, C., et al.
(author)
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PACS and SPIRE photometer maps of M33: First results of the HERschel M33 Extended Survey (HERM33ES)
- 2010
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:Article Number: L67
-
Journal article (peer-reviewed)abstract
- Context. Within the framework of the HERM33ES key program, we are studying the star forming interstellar medium in the nearby, metal-poor spiral galaxy M33, exploiting the high resolution and sensitivity of Herschel. Aims. We use PACS and SPIRE maps at 100, 160, 250, 350, and 500 mu m wavelength, to study the variation of the spectral energy distributions (SEDs) with galacto-centric distance. Methods. Detailed SED modeling is performed using azimuthally averaged fluxes in elliptical rings of 2 kpc width, out to 8 kpc galacto-centric distance. Simple isothermal and two-component grey body models, with fixed dust emissivity index, are fitted to the SEDs between 24 mu m and 500 mu m using also MIPS/Spitzer data, to derive first estimates of the dust physical conditions. Results. The far-infrared and submillimeter maps reveal the branched, knotted spiral structure of M33. An underlying diffuse disk is seen in all SPIRE maps (250-500 mu m). Two component fits to the SEDs agree better than isothermal models with the observed, total and radially averaged flux densities. The two component model, with beta fixed at 1.5, best fits the global and the radial SEDs. The cold dust component clearly dominates; the relative mass of the warm component is less than 0.3% for all the fits. The temperature of the warm component is not well constrained and is found to be about 60 K +/- 10 K. The temperature of the cold component drops significantly from similar to 24 K in the inner 2 kpc radius to 13 K beyond 6 kpc radial distance, for the best fitting model. The gas-to-dust ratio for beta = 1.5, averaged over the galaxy, is higher than the solar value by a factor of 1.5 and is roughly in agreement with the subsolar metallicity of M33.
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| 12. |
- Pérez-González, P.G.P., et al.
(author)
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Improving the identification of high-z Herschel sources with position priors and optical/NIR and FIR/mm photometric redshifts
- 2010
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:Article Number: L15
-
Journal article (peer-reviewed)abstract
- We present preliminary results about the detection of high redshift (U)LIRGs in the Bullet cluster field by the PACS and SPIRE instruments within the Herschel Lensing Survey (HLS) Program. We describe in detail a photometric procedure designed to recover robust fluxes and deblend faint Herschel sources near the confusion noise. The method is based on the use of the positions of Spitzer/MIPS 24 mu m sources as priors. Our catalogs are able to reliably (5 sigma) recover galaxies with fluxes above 6 and 10 mJy in the PACS 100 and 160 mu m channels, respectively, and 12 to 18 mJy in the SPIRE bands. We also obtain spectral energy distributions covering the optical through the far-infrared/millimeter spectral ranges of all the Herschel detected sources, and analyze them to obtain independent estimations of the photometric redshift based on either stellar population or dust emission models. We exemplify the potential of the combined use of Spitzer position priors plus independent optical and IR photometric redshifts to robustly assign optical/NIR counterparts to the sources detected by Herschel and other (sub-)mm instruments.
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| 13. |
- Aalto, Susanne, 1964, et al.
(author)
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Probing highly obscured, self-absorbed galaxy nuclei with vibrationally excited HCN
- 2015
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 584
-
Journal article (peer-reviewed)abstract
- We present high resolution (0.'' 4) IRAM PdBI and ALMA mm and submm observations of the (ultra) luminous infrared galaxies ((U)LIRGs) IRAS 17208-0014, Arp220, IC 860 and Zw049.057 that reveal intense line emission from vibrationally excited (nu(2) = 1) J = 3-2 and 4-3 HCN. The emission is emerging from buried, compact (r 5 x 10(13) L-circle dot kpc(-2). These nuclei are likely powered by accreting supermassive black holes (SMBHs) and/or hot (>200 K) extreme starbursts. Vibrational, nu(2) = 1, lines of HCN are excited by intense 14 mu m mid-infrared emission and are excellent probes of the dynamics, masses, and physical conditions of (U)LIRG nuclei when H-2 column densities exceed 10(24) cm(-2). It is clear that these lines open up a new interesting avenue to gain access to the most obscured AGNs and starbursts. Vibrationally excited HCN acts as a proxy for the absorbed mid-infrared emission from the embedded nuclei, which allows for reconstruction of the intrinsic, hotter dust SED. In contrast, we show strong evidence that the ground vibrational state (. = 0), J = 3-2 and 4-3 rotational lines of HCN and HCO+ fail to probe the highly enshrouded, compact nuclear regions owing to strong self-and continuum absorption. The HCN and HCO+ line profiles are double-peaked because of the absorption and show evidence of non-circular motions-possibly in the form of in-or outflows. Detections of vibrationally excited HCN in external galaxies are so far limited to ULIRGs and early-type spiral LIRGs, and we discuss possible causes for this. We tentatively suggest that the peak of vibrationally excited HCN emission is connected to a rapid stage of nuclear growth, before the phase of strong feedback.
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| 14. |
- Belete, A. Bewketu, et al.
(author)
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Molecular gas kinematics in the nuclear region of nearby Seyfert galaxies with ALMA
- 2021
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 654
-
Journal article (peer-reviewed)abstract
- Context. The study of the distribution, morphology, and kinematics of cold molecular gas in the nuclear and circumnuclear regions of active galactic nuclei (AGNs) helps to characterise and hence to quantify the impact of the AGNs on the host galaxy over its lifetime. Aims. We present the analysis of the molecular gas in the nuclear regions of three Seyfert galaxies, NGC 4968, NGC 4845, and MCG-06-30-15, using Atacama Large sub-Millimetre Array (ALMA) observations of the CO(2-1) emission line. The aim is to determine the kinematics of the gas in the central (∼1 kpc) region and thereby to probe nuclear fueling and feedback of AGNs. Methods. We used two different softwares, namely the 3D-Based Analysis of Rotating Object via Line Observations and DiskFit, to model the kinematics of the gas in the molecular disc, and thereby to determine the gas rotation and any kinematical perturbations. Results. Circular motions dominate the kinematics of the molecular gas in the central discs, mainly in NGC 4845 and MCG-06-30-15; however there is clear evidence of non-circular motions in the central (∼1 kpc) region of NGC 4845 and NGC 4968. The strongest non-circular motion is detected in the inner disc of NGC 4968, mainly along the minor kinematic axis, with a velocity ∼115 km s-1. Of all DiskFit models, the bisymmetric model is found to give the best fit for NGC 4968 and NGC 4845, indicating that the observed non-circular motions in the inner disc of these galaxies could result from the nuclear barred structure, where the gas streams in elliptical orbits aligned along the bar. If the dynamics of NGC 4968 is modelled as a corotation pattern just outside of the bar, the bar pattern speed becomes ωb = 52 km s-1 kpc-1; the corotation is set at 3.5 kpc; and the inner Lindblad resonance (ILR) ring is R = 300 pc, corresponding to the CO emission ring. In the NGC 4968 galaxy, the torques exerted on the gas by the bar are positive in the centre, within the gas nuclear ring, and negative outside. This shows that the gas is transiently trapped in the ILR. The comparison of the CO intensity maps with the map of the cold dust emission shows an absence of CO in the centre of NGC 4968; also the dust distribution and CO emission in and around the centre of NGC 4845 have similar extensions. The 1.2 mm ALMA continuum is peaked and compact in NGC 4968 and MCG-06-30-15, but their CO(2-1) emissions have extended distributions. Allowing the CO-to-H2 conversion factor αCO between 0.8 and 3.2, which is typical of nearby galaxies of the same type, the molecular mass M(H2) is estimated to be ∼3 - 12 × 107 M⊙ (NGC 4968), ∼9 - 36 × 107 M⊙ (NGC 4845), and ∼1 - 4 × 107 M⊙ (MCG-06-30-15). Conclusions. We conclude that the observed non-circular motions in the molecular disc of NGC 4968 and likely those seen in NGC 4845 are due to the presence of the bar in the nuclear region. We discuss the possibility that the observed pattern in the kinematics might be a consequence of the presence of AGNs, and this might be the case for NGC 4845. At the current spectral and spatial resolution and sensitivity, we cannot claim any strong evidence in these sources of the long sought feedback or feeding effect resulting from the presence of AGNs.
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| 15. |
- Boone, F., et al.
(author)
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An extended Herschel drop-out source in the center of AS1063: A normal dusty galaxy at z = 6.1 or SZ substructures?
- 2013
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 559, s. L1-
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Journal article (peer-reviewed)abstract
- In the course of our 870 μm APEX/LABOCA follow-up of the Herschel Lensing Survey we have detected a source in AS1063 (RXC J2248.7-4431) that has no counterparts in any of the Herschel PACS/SPIRE bands, it is a Herschel "drop-out" with S870=S500 ≥ 0:5. The 870 μm emission is extended and centered on the brightest cluster galaxy, suggesting either a multiply imaged background source or substructure in the Sunyaev-Zel'dovich increment due to inhomogeneities in the hot cluster gas of this merging cluster. We discuss both interpretations with emphasis on the putative lensed source. Based on the observed properties and on our lens model we find that this source may be the first submillimeter galaxy (SMG) with a moderate far-infrared (FIR) luminosity (LFIR. © ESO 2013.
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| 16. |
- Burillo, S. G., et al.
(author)
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ALMA resolves the torus of NGC 1068: Continuum and molecular line emission
- 2016
-
In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 823:1, s. Art. no. L12-
-
Journal article (peer-reviewed)abstract
- We used the Atacama Large Millimeter Array (ALMA) to map the emission of the CO(6-5) molecular line and the 432 mu m continuum emission from the 300 pc sized circumnuclear disk (CND) of the nearby Seyfert 2 galaxy NGC 1068 with a spatial resolution of similar to 4 pc. These observations spatially resolve the CND and, for the first time, image the dust emission, the molecular gas distribution, and the kinematics from a 7-10 pc diameter disk that represents the submillimeter counterpart of the putative torus of NGC 1068. We fitted the nuclear spectral energy distribution of the torus using ALMA and near-and mid-infrared (NIR/MIR) data with CLUMPY torus models. The mass and radius of the best-fit solution for the torus are both consistent with the values derived from the ALMA data alone: M-gas(torus) = (1 +/- 0.3) x 10(5) M-circle dot and R-torus = 3.5 +/- 0.5 pc. The dynamics of the molecular gas in the torus show strong non-circular motions and enhanced turbulence superposed on a surprisingly slow rotation pattern of the disk. By contrast with the nearly edge-on orientation of the H2O megamaser disk, we found evidence suggesting that the molecular torus is less inclined (i = 34 degrees-66 degrees) at larger radii. The lopsided morphology and complex kinematics of the torus could be the signature of the Papaloizou-Pringle instability, long predicted to likely drive the dynamical evolution of active galactic nuclei tori.
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| 17. |
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| 18. |
- Combes, Françoise, et al.
(author)
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PKS 1413+135: OH and H i at z = 0.247 with MeerKAT
- 2023
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 671
-
Journal article (peer-reviewed)abstract
- The BL Lac object PKS 1413+135 was observed by the Large Survey Project MeerKAT Absorption Line Survey (MALS) in the L-band, at 1139 MHz and 12931379 MHz, targeting the HI and OH lines in absorption at z=0.24671. The radio continuum might come from the nucleus of the absorbing galaxy or from a background object at redshift lower than 0.5, as suggested by the absence of gravitational images. The HI absorption line is detected at a high signal-To-noise ratio, with a narrow central component, and with a red wing, confirming previous results. The OH 1720 MHz line is clearly detected in (maser) emission, peaking at a velocity shifted by-10 to-15 km s-1 with respect to the HI peak. The 1612 MHz line is lost due to radio frequency interference. The OH 1667 MHz main line is tentatively detected in absorption, but not the 1665 MHz line. Over 30 years a high variability is observed in optical depths, due to the rapid changes of the line of sight caused by the superluminal motions of the radio knots. The HI line has varied by 20% in depth, while the OH-1720 MHz depth has varied by a factor of ∼3. The position of the central velocity and the widths also varied. The absorbing galaxy is an early-Type spiral (maybe S0) seen edge-on, with a prominent dust lane, covering the whole disk. Given the measured mass concentration and the radio continuum size at centimeter wavelengths (100 mas corresponding to 400 pc at z=0.25), the width of the absorption lines from the nuclear regions are expected up to 250 km s-1. The narrowness of the observed lines (< 15 km s-1) suggests that the absorption comes from an outer gas ring, as frequently observed in S0 galaxies. The millimetric lines are even narrower (< 1 km s-1), which corresponds to the continuum size restricted to the core. The radio core is covered by individual 1 pc molecular clouds, whose column density is a few 1022 cm-2, which is compatible with the gas screen detected in X-rays.
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| 19. |
- Combes, F., et al.
(author)
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PKS 1830-211: OH and HI at z = 0.89 and the first MeerKAT UHF spectrum
- 2021
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 648
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Journal article (peer-reviewed)abstract
- The Large Survey Project (LSP) "MeerKAT Absorption Line Survey"(MALS) is a blind H I 21 cm and OH 18 cm absorption line survey in the L- and UHF-bands, primarily designed to better determine the occurrence of atomic and molecular gas in the circumgalactic and intergalactic medium, and its redshift evolution. Here we present the first results using the UHF band obtained towards the strongly lensed radio source PKS 1830-211, revealing the detection of absorption produced by the lensing galaxy. With merely 90 min of data acquired on-source for science verification and processed using the Automated Radio Telescope Imaging Pipeline (ARTIP), we detect in absorption the known H I 21 cm and OH 18 cm main lines at z = 0.89 at an unprecedented signal-to-noise ratio (4000 in the continuum, in each 6 km s-1 wide channel). For the first time we report the detection of OH satellite lines at z = 0.89, which until now have not been detected at z > 0.25. We decompose the OH lines into a thermal and a stimulated contribution, where the 1612 and 1720 MHz lines are conjugate. The total OH 1720 MHz emission line luminosity is 6100 L⊙. This is the most luminous known 1720 MHz maser line and is also among the most luminous of the OH main line megamasers. The absorption components of the different images of the background source sample different light paths in the lensing galaxy, and their weights in the total absorption spectrum are expected to vary in time on daily and monthly time scales. We compare our normalized spectra with those obtained more than 20 years ago, and find no variation. We interpret the absorption spectra with the help of a lens galaxy model derived from an N-body hydrodynamical simulation, with a morphology similar to its optical HST image. The resulting absorption lines depend mainly on the background continuum and the radial distribution of the gas surface density for each atomic and molecular species. We show that it is possible to reproduce the observations assuming a realistic spiral galaxy disk without invoking any central gas outflows. However, there are distinct and faint high-velocity features in the ALMA millimeter absorption spectra that most likely originate from high-velocity clouds or tidal features. These clouds may contribute to broaden the H I and OH spectra.
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| 20. |
- Emig, K.L., et al.
(author)
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Discovery of Hydrogen Radio Recombination Lines at z = 0.89 toward PKS 1830-211
- 2023
-
In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 944:1
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Journal article (peer-reviewed)abstract
- We report the detection of stimulated hydrogen radio recombination line (RRL) emission from ionized gas in a z = 0.89 galaxy using 580-1670 MHz observations from the MeerKAT Absorption Line Survey. The RRL emission originates in a galaxy that intercepts and strongly lenses the radio blazar PKS 1830−211 (z = 2.5). This is the second detection of RRLs outside of the local Universe and the first clearly associated with hydrogen. We detect effective H144α (and H163α) transitions at observed frequencies of 1156 (798) MHz by stacking 17 (27) RRLs with 21σ (14σ) significance. The RRL emission contains two main velocity components and is coincident in velocity with H i 21 cm and OH 18 cm absorption. We use the RRL spectral line energy distribution and a Bayesian analysis to constrain the density (n e ) and the volume-averaged path length (ℓ) of the ionized gas. We determine log ( n e ) = 2.0 − 0.7 + 1.0 cm−3 and log ( ℓ ) = − 0.7 − 1.1 + 1.1 pc toward the northeast (NE) lensed image, likely tracing the diffuse thermal phase of the ionized ISM in a thin disk. Toward the southwest (SW) lensed image, we determine log ( n e ) = 3.2 − 1.0 + 0.4 cm−3 and log ( ℓ ) = − 2.7 − 0.2 + 1.8 pc, tracing gas that is more reminiscent of H scii regions. We estimate a star formation (surface density) rate of ΣSFR ∼ 0.6 M ⊙ yr−1 kpc−2 or SFR ∼ 50 M ⊙ yr−1, consistent with a star-forming main-sequence galaxy of M ⋆ ∼ 1011 M ⊙. The discovery presented here opens up the possibility of studying ionized gas at high redshifts using RRL observations from current and future (e.g., SKA and ngVLA) radio facilities.
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| 21. |
- Henkel, C., et al.
(author)
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Molecular line emission in NGC 4945, imaged with ALMA
- 2018
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 615
-
Journal article (peer-reviewed)abstract
- NGC 4945 is one of the nearest (D ≈ 3.8 Mpc; 1 00 ≈ 19 pc) starburst galaxies. To investigate the structure, dynamics, and composition of the dense nuclear gas of this galaxy, ALMA band 3 (λ ≈ 3−4 mm) observations were carried out with ≈2 00 resolution. Three HCN and two HC + isotopologues, CS, C 3 H 2 , SiO, HCO, and CH 3 C 2 H were measured. Spectral line imaging demonstrates the presence of a rotating nuclear disk of projected size 10 00 × 2 00 reaching out to a galactocentric radius of r ≈ 100 pc with position angle PA = 45 ◦ ± 2 ◦ , inclination i = 75 ◦ ± 2 ◦ and an unresolved bright central core of size <∼ 2 00 . The continuum source, representing mostly free-free radiation from star forming regions, is more compact than the nuclear disk by a linear factor of two but shows the same position angle and is centered 0 00 . 39 ± 0 00 . 14 northeast of the nuclear accretion disk defined by H 2 O maser emission. Near the systemic velocity but outside the nuclear disk, both HCN J = 1 → 0 and CS J = 2 → 1 delineate molecular arms of length >∼ 15 00 ( >∼ 285 pc) on opposite sides of the dynamical center. These are connected by a (deprojected) ≈ 0.6 kpc sized molecular bridge, likely a dense gaseous bar seen almost ends-on, shifting gas from the front and back side into the nuclear disk. Modeling this nuclear disk located farther inside (r <∼ 100 pc) with tilted rings provides a good fit by inferring a coplanar outflow reaching a characteristic deprojected velocity of ≈50 km s −1 . All our molecular lines, with the notable exception of CH 3 C 2 H, show significant absorption near the systemic velocity (≈571 km s −1 ), within the range ≈500-660 km s −1 . Apparently, only molecular transitions with low critical H 2 density (n crit<∼ 10 4 cm −3 ) do not show absorption. The velocity field of the nuclear disk, derived from CH 3 C 2 H, provides evidence for rigid rotation in the inner few arcseconds and a dynamical mass of M tot = (2.1 ± 0.2) × 10 8 M inside a galactocentric radius of 2 00 . 45 (≈45 pc), with a significantly flattened rotation curve farther out. Velocity integrated line intensity maps with most pronounced absorption show molecular peak positions up to ≈1 00 . 5 (≈30 pc) southwest of the continuum peak, presumably due to absorption, which appears to be most severe slightly northeast of the nuclear maser disk. A nitrogen isotope ratio of 14 N/ 15 N ≈ 200-450 is estimated. This range of values is much higher then previously reported on a tentative basis. Therefore, because 15 N is less abundant than expected, the question for strong 15 N enrichment by massive star ejecta in starbursts still remains to be settled.
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| 22. |
- Herber, O. R., et al.
(author)
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What feedback do reviewers give when reviewing qualitative manuscripts? A focused mapping review and synthesis
- 2020
-
In: BMC Medical Research Methodology. - : Springer Science and Business Media LLC. - 1471-2288. ; 20:1
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Journal article (peer-reviewed)abstract
- Background Peer review is at the heart of the scientific process. With the advent of digitisation, journals started to offer electronic articles or publishing online only. A new philosophy regarding the peer review process found its way into academia: the open peer review. Open peer review as practiced by BioMed Central (BMC) is a type of peer review where the names of authors and reviewers are disclosed and reviewer comments are published alongside the article. A number of articles have been published to assess peer reviews using quantitative research. However, no studies exist that used qualitative methods to analyse the content of reviewers' comments. Methods A focused mapping review and synthesis (FMRS) was undertaken of manuscripts reporting qualitative research submitted to BMC open access journals from 1 January - 31 March 2018. Free-text reviewer comments were extracted from peer review reports using a 77-item classification system organised according to three key dimensions that represented common themes and sub-themes. A two stage analysis process was employed. First, frequency counts were undertaken that allowed revealing patterns across themes/sub-themes. Second, thematic analysis was conducted on selected themes of the narrative portion of reviewer reports. Results A total of 107 manuscripts submitted to nine open-access journals were included in the FMRS. The frequency analysis revealed that among the 30 most frequently employed themes "writing criteria" (dimension II) is the top ranking theme, followed by comments in relation to the "methods" (dimension I). Besides that, some results suggest an underlying quantitative mindset of reviewers. Results are compared and contrasted in relation to established reporting guidelines for qualitative research to inform reviewers and authors of frequent feedback offered to enhance the quality of manuscripts. Conclusions This FMRS has highlighted some important issues that hold lessons for authors, reviewers and editors. We suggest modifying the current reporting guidelines by including a further item called "Degree of data transformation" to prompt authors and reviewers to make a judgment about the appropriateness of the degree of data transformation in relation to the chosen analysis method. Besides, we suggest that completion of a reporting checklist on submission becomes a requirement.
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| 23. |
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| 27. |
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| 28. |
- Wagenveld, Jonah D., et al.
(author)
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The MeerKAT Absorption Line Survey: Homogeneous continuum catalogues towards a measurement of the cosmic radio dipole
- 2023
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 673
-
Journal article (peer-reviewed)abstract
- The number counts of homogeneous samples of radio sources are a tried and true method of probing the large-scale structure of the Universe, as most radio sources outside the Galactic plane are at cosmological distances. As such, they are expected to trace the cosmic radio dipole, an anisotropy analogous to the dipole seen in the cosmic microwave background (CMB). Results have shown that although the cosmic radio dipole matches the direction of the CMB dipole, it has a significantly larger amplitude. This unexplained result challenges our assumption of the Universe being isotropic, which can have large repercussions for the current cosmological paradigm. Though significant measurements have been made, sensitivity to the radio dipole is generally hampered by systematic effects that can cause large biases in the measurement. Here we assess these systematics with data from the MeerKAT Absorption Line Survey (MALS), a blind search for absorption lines with pointings centred on bright radio sources. With the sensitivity and field of view of MeerKAT, thousands of sources are observed in each pointing, allowing for the possibility of measuring the cosmic radio dipole given enough pointings. We present the analysis of ten MALS pointings, focusing on systematic effects that could lead to an inhomogeneous catalogue. We describe the calibration and creation of full band continuum images and catalogues, producing a combined catalogue containing 16 307 sources and covering 37.5 square degrees of sky down to a sensitivity of 10 μJy beam-1. We measure the completeness, purity, and flux recovery statistics for these catalogues using simulated data. We investigate different source populations in the catalogues by looking at flux densities and spectral indices and how they might influence source counts. Using the noise characteristics of the pointings, we find global measures that can be used to correct for the incompleteness of the catalogue, producing corrected number counts down to 100-200 μJy. We show that we can homogenise the catalogues and properly account for systematic effects. We determine that we can measure the dipole to 3significance with 100 MALS pointings.
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| 29. |
- Aalto, Susanne, 1964, et al.
(author)
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The hidden heart of the luminous infrared galaxy IC 860: I. A molecular inflow feeding opaque, extreme nuclear activity
- 2019
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 627
-
Journal article (peer-reviewed)abstract
- High-resolution (0.'03-0.'09 (9-26 pc)) ALMA (100-350 GHz (λ3 to 0.8 mm)) and (0.'04 (11 pc)) VLA 45 GHz measurements have been used to image continuum and spectral line emission from the inner (100 pc) region of the nearby infrared luminous galaxy IC 860. We detect compact (r ∼ 10 pc), luminous, 3 to 0.8 mm continuum emission in the core of IC 860, with brightness temperatures TB > 160 K. The 45 GHz continuum is equally compact but significantly fainter in flux. We suggest that the 3 to 0.8 mm continuum emerges from hot dust with radius r ∼ 8 pc and temperature Td ∼ 280 K, and that it is opaque at millimetre wavelengths, implying a very large H2 column density N(H2)≥ 1026 cm-2. Vibrationally excited lines of HCN v2 = 1f J = 4 - 3 and 3-2 (HCN-VIB) are seen in emission and spatially resolved on scales of 40-50 pc. The line-to-continuum ratio drops towards the inner r = 4 pc, resulting in a ring-like morphology. This may be due to high opacities and matching HCN-VIB excitation- and continuum temperatures. The HCN-VIB emission reveals a north-south nuclear velocity gradient with projected rotation velocities of v = 100 km s-1 at r = 10 pc. The brightest emission is oriented perpendicular to the velocity gradient, with a peak HCN-VIB 3-2 TB of 115 K (above the continuum). Vibrational ground-state lines of HCN 3-2 and 4-3, HC15N 4-3, HCO+ 3-2 and 4-3, and CS 7-6 show complex line absorption and emission features towards the dusty nucleus. Redshifted, reversed P-Cygni profiles are seen for HCN and HCO+ consistent with gas inflow with vin ≤ 50 km s-1. Foreground absorption structures outline the flow, and can be traced from the north-east into the nucleus. In contrast, CS 7-6 has blueshifted line profiles with line wings extending out to -180 km s-1. We suggest that a dense and slow outflow is hidden behind a foreground layer of obscuring, inflowing gas. The centre of IC 860 is in a phase of rapid evolution where an inflow is building up a massive nuclear column density of gas and dust that feeds star formation and/or AGN activity. The slow, dense outflow may be signaling the onset of feedback. The inner, r = 10 pc, IR luminosity may be powered by an AGN or a compact starburst, which then would likely require a top-heavy initial mass function.
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| 30. |
- Burillo, S. G., et al.
(author)
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ALMA images the many faces of the NGC 1068 torus and its surroundings
- 2019
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 632
-
Journal article (peer-reviewed)abstract
- Aims. We investigate the fueling and the feedback of nuclear activity in the nearby (D = 14 Mpc) Seyfert 2 barred galaxy NGC 1068 by studying the distribution and kinematics of molecular gas in the torus and its connections to the host galaxy disk. Methods.We used the Atacama Large Millimeter Array (ALMA ) to image the emission of a set of molecular gas tracers in the circumnuclear disk (CND) and the torus of the galaxy using the CO(2-1), CO(3-2), and HCO+(4-3) lines and their underlying continuum emission with high spatial resolutions (0:0300 0:0900 ' 26 pc). These transitions, which span a wide range of physical conditions of molecular gas (n(H2) 103107 cm3), are instrumental in revealing the density radial stratification and the complex kinematics of the gas in the torus and its surroundings. Results. The ALMA images resolve the CND as an asymmetric ringed disk of D ' 400 pc in size and '1:4 108 M in mass. The CND shows a marked deficit of molecular gas in its central '130 pc region. The inner edge of the ring is associated with the presence of edge-brightened arcs of NIR polarized emission, which are identified with the current working surface of the ionized wind of the active galactic nucleus (AGN). ALMA proves the existence of an elongated molecular disk/torus in NGC 1068 of Mgas torus ' 3 105 M, which extends over a large range of spatial scales D ' 1030 pc around the central engine. The new observations evidence the density radial stratification of the torus: the HCO+(4-3) torus, with a full size DHCO+(43) = 11 0:6 pc, is a factor of between two and three smaller than its CO(2-1) and CO(3-2) counterparts, which have full sizes of DCO(32) = 26 0:6 pc and DCO(21) = 28 0:6 pc, respectively. This result brings into light the many faces of the molecular torus. The torus is connected to the CND through a network of molecular gas streamers detected inside the CND ring. The kinematics of molecular gas show strong departures from circular motions in the torus, the gas streamers, and the CND ring. These velocity field distortions are interconnected and are part of a 3D outflow that reflects the eects of AGN feedback on the kinematics of molecular gas across a wide range of spatial scales around the central engine. In particular, we estimate through modeling that a significant fraction of the gas inside the torus ('0:40:6 Mgas torus) and a comparable amount of mass along the gas streamers are outflowing. However, the bulk of the mass, momentum, and energy of the molecular outflow of NGC 1068 is contained at larger radii in the CND region, where the AGN wind and the radio jet are currently pushing the gas assembled at the Inner Lindblad Resonance (ILR) ring of the nuclear stellar bar. Conclusions. In our favored scenario a wide-angle AGN wind launched from the accretion disk of NGC1068 is currently impacting a sizable fraction of the gas inside the torus. However, a large gas reservoir ('1:21:8 105 M), which lies close to the equatorial plane of the torus, remains unaected by the feedback of the AGN wind and can therefore continue fueling the AGN for at least '14 Myr. Nevertheless, AGN fueling currently seems thwarted on intermediate scales (15 pc r 50 pc).
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| 31. |
- Burillo, S. G., et al.
(author)
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ALMA imaging of C2H emission in the disk of NGC 1068
- 2017
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 608, s. A56-
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Journal article (peer-reviewed)abstract
- Aims. We study the feedback of star formation and nuclear activity on the chemistry of molecular gas in NGC 1068, a nearby (D = 14 Mpc) Seyfert 2 barred galaxy, by analyzing whether the abundances of key molecular species such as ethynyl (C2H), which is a classical tracer of photon dominated regions (PDR), change in the different environments of the disk of the galaxy. Methods. We used the Atacama Large Millimeter Array (ALMA) to map the emission of the hyperfine multiplet of C2H(N = 1-0) and its underlying continuum emission in the central r similar or equal to 35" (2.5 kpc) region of the disk of NGC 1068 with a spatial resolution 1.0 x 0.7 (similar or equal to 50-70 pc). We used maps of the dust continuum emission obtained at 349 GHz by ALMA to derive the H-2 gas column densities and combined these with the C2H map at matched spatial resolution to estimate the fractional abundance of this species. We developed a set of time-dependent chemical models, which include shocks, gas-phase PDRs, and gas-grain chemical models to determine the origin of the C2H gas. Results. A sizeable fraction of the total C2H line emission is detected from the r similar or equal to 1.3 kpc starburst (SB) ring, which is a region that concentrates the bulk of the recent massive star formation in the disk traced by the Pa alpha emission complexes imaged by the Hubble Space Telescope (HST). However, the brightest C2H emission originates from a r similar or equal to 200 pc off -centered circumnuclear disk (CND), where evidence of a molecular outflow has been previously found in other molecular tracers imaged by ALMA. We also detect significant emission that connects the CND with the outer disk in a region that probes the interface between the molecular disk and ionized gas outflow out to r similar or equal to 400 pc. We derived the fractional abundances of C2H (X(C2H)) assuming local thermodynamic equilibrium (LTE) conditions and a set of excitation temperatures (T-ex) constrained by the previous multiline CO studies of the galaxy. Our estimates range from X(C2H) similar or equal to a few 10(-8) in the SB ring up to X(C2H) similar or equal to a few 10(-7) in the outflow region. The PDR models that incorporate gas-grain chemistry are able to account for X(C2H) in the SB ring for moderately dense (n(H-2) >= 10(4) cm(-3)) and moderately UV-irradiated gas (UV-field = 10(4-5) cm(-3)). Conclusions. We find that the transient conditions required to fit the high values of X(C2H) in the outflow are likely due to UV or X-ray irradiated non-dissociative shocks associated with the highly turbulent interface between the outflow and molecular gas in NGC 1068. Although the inferred local timescales are short, the erosion of molecular clouds by the active galactic nucleus (AGN) wind and/or the jet likely resupplies the interface working surface continuously, making a nearly steady state persist in the disk of the galaxy.
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| 32. |
- Burillo, S. G., et al.
(author)
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High-resolution imaging of the molecular outflows in two mergers: IRAS 17208-0014 and NGC 1614
- 2015
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 580
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Journal article (peer-reviewed)abstract
- Context. Galaxy evolution scenarios predict that the feedback of star formation and nuclear activity (AGN) can drive the transformation of gas-rich spiral mergers into (ultra) luminous infrared galaxies and, eventually, lead to the build-up of QSO/elliptical hosts. Aims. We study the role that star formation and AGN feedback have in launching and maintaining the molecular outflows in two starburst-dominated advanced mergers, NGC 1614 (DL = 66 Mpc) and IRAS 17208-0014 (DL = 181 Mpc), by analyzing the distribution and kinematics of their molecular gas reservoirs. Both galaxies present evidence of outflows in other phases of their ISM. Methods. We used the Plateau de Bure interferometer (PdBI) to image the CO(10) and CO(21) line emissions in NGC 1614 and IRAS 17208-0014, respectively, with high spatial resolution (0: 0051: 002). The velocity fields of the gas were analyzed and modeled to find the evidence of molecular outflows in these sources and characterize the mass, momentum, and energy of these components. Results. While most (95%) of the CO emission stems from spatially resolved (23 kpc-diameter) rotating disks, we also detect in both mergers the emission from high-velocity line wings that extend up to -500-700 km s1, well beyond the estimated virial range associated with rotation and turbulence. The kinematic major axis of the line-wing emission is tilted by 90 in NGC 1614 and by 180 in IRAS 17208-0014 relative to the major axes of their respective rotating disks. These results can be explained by the existence of non-coplanar molecular outflows in both systems: the outflow axis is nearly perpendicular to the rotating disk in NGC 1614, but it is tilted relative to the angular momentum axis of the rotating disk in IRAS 17208-0014. Conclusions. In stark contrast to NGC 1614, where star formation alone can drive its molecular outflow, the mass, energy, and momentum budget requirements of the molecular outflow in IRAS 17208-0014 can be best accounted for by the existence of a so far undetected (hidden) AGN of LAGN71011 L The geometry of the molecular outflow in IRAS 17208-0014 suggests that the outflow is launched by a non-coplanar disk that may be associated with a buried AGN in the western nucleus.
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| 33. |
- Combes, R., et al.
(author)
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Combinatorial bandits revisited
- 2015
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In: Advances in Neural Information Processing Systems. - : Neural Information Processing Systems. ; , s. 2116-2124
-
Conference paper (peer-reviewed)abstract
- This paper investigates stochastic and adversarial combinatorial multi-armed bandit problems. In the stochastic setting under semi-bandit feedback, we derive a problem-specific regret lower bound, and discuss its scaling with the dimension of the decision space. We propose ESCB, an algorithm that efficiently exploits the structure of the problem and provide a finite-time analysis of its regret. ESCB has better performance guarantees than existing algorithms, and significantly outperforms these algorithms in practice. In the adversarial setting under bandit feedback, we propose COMBEXP, an algorithm with the same regret scaling as state-of-the-art algorithms, but with lower computational complexity for some combinatorial problems.
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| 34. |
- Combes, R., et al.
(author)
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Dynamic rate and channel selection in cognitive radio systems
- 2015
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In: IEEE Journal on Selected Areas in Communications. - 0733-8716 .- 1558-0008. ; 33:5, s. 910-921
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Journal article (peer-reviewed)abstract
- In this paper, we investigate dynamic channel and rate selection in cognitive radio systems that exploit a large number of channels free from primary users. In such systems, transmitters may rapidly change the selected (channel, rate) pair to opportunistically learn and track the pair offering the highest throughput. We formulate the problem of sequential channel and rate selection as an online optimization problem and show its equivalence to a structured multiarmed-bandit problem. The structure stems from inherent properties of the achieved throughput as a function of the selected channel and rate. We derive fundamental performance limits satisfied by any channel and rate adaptation algorithm and propose algorithms that achieve (or approach) these limits. In turn, the proposed algorithms optimally exploit the inherent structure of the throughput. We illustrate the efficiency of our algorithms using both test-bed and simulation experiments, in both stationary and nonstationary radio environments. In stationary environments, the packet successful transmission probabilities at the various channel and rate pairs do not evolve over time, whereas in nonstationary environments, they may evolve. In practical scenarios, the proposed algorithms are able to track the best channel and rate quite accurately without the need for any explicit measurement of and feedback on the quality of the various channels.
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| 35. |
- Combes, R., et al.
(author)
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Learning to rank : Regret lower bounds and efficient algorithms
- 2015
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In: Performance Evaluation Review. - : ACM Press. - 0163-5999 .- 1557-9484. ; 43:1, s. 231-244
-
Journal article (peer-reviewed)abstract
- Algorithms for learning to rank Web documents, display ads, or other types of items constitute a fundamental component of search engines and more generally of online services. In such systems, when a user makes a request or visits a web page, an ordered list of items (e.g. documents or ads) is displayed; the user scans this list in order, and clicks on the first relevant item if any. When the user clicks on an item, the reward collected by the system typically decreases with the position of the item in the displayed list. The main challenge in the design of sequential list selection algorithms stems from the fact that the probabilities with which the user clicks on the various items are unknown and need to be learned. We formulate the design of such algorithms as a stochastic bandit optimization problem. This problem differs from the classical bandit framework: (1) the type of feedback received by the system depends on the actual relevance of the various items in the displayed list (if the user clicks on the last item, we know that none of the previous items in the list are relevant); (2) there are inherent correlations between the average relevance of the items (e.g. the user may be interested in a specific topic only). We assume that items are categorized according to their topic and that users are clustered, so that users of the same cluster are interested in the same topic. We investigate several scenarios depending on the available sideinformation on the user before selecting the displayed list: (a) we first treat the case where the topic the user is interested in is known when she places a request; (b) we then study the case where the user cluster is known but the mapping between user clusters and topics is unknown. For both scenarios, we derive regret lower bounds and devise algorithms that approach these fundamental limits.
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| 36. |
- Combes, R., et al.
(author)
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Unimodal Bandits with Continuous Arms : Order-optimal Regret without Smoothness
- 2020
-
In: Performance Evaluation Review. - : Association for Computing Machinery (ACM). - 0163-5999 .- 1557-9484. ; 48:1, s. 107-108
-
Journal article (peer-reviewed)abstract
- We consider stochastic bandit problems with a continuous set of arms and where the expected reward is a continuous and unimodal function of the arm. For these problems, we propose the Stochastic Polychotomy (SP) algorithms, and derive finite-time upper bounds on their regret and optimization error. We show that, for a class of reward functions, the SP algorithm achieves a regret and an optimization error with optimal scalings, i.e., O( g T ) and O(1/ g T ) (up to a logarithmic factor), respectively.
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| 37. |
- Combes, R., et al.
(author)
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Unimodal Bandits with Continuous Arms : Order-optimal Regret without Smoothness
- 2020
-
In: SIGMETRICS Performance 2020 - Abstracts of the 2020 SIGMETRICS/Performance Joint International Conference on Measurement and Modeling of Computer Systems. - New York, NY, USA : Association for Computing Machinery, Inc. ; , s. 107-108
-
Conference paper (peer-reviewed)abstract
- We consider stochastic bandit problems with a continuous set of arms and where the expected reward is a continuous and unimodal function of the arm. For these problems, we propose the Stochastic Polychotomy (SP) algorithms, and derive finite-time upper bounds on their regret and optimization error. We show that, for a class of reward functions, the SP algorithm achieves a regret and an optimization error with optimal scalings, i.e., O(T) and O(1/T) (up to a logarithmic factor), respectively.
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| 38. |
- Dejongh, J, et al.
(author)
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An Integrated Approach to the Prediction of Systemic Toxicity using Computer-based Biokinetic Models and Biological In vitro Test Methods : Overview of a Prevalidation Study Based on the ECITTS Project.
- 1999
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In: Toxicology in Vitro. - 0887-2333 .- 1879-3177. ; 13:4-5, s. 549-54
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Journal article (peer-reviewed)abstract
- Chemical toxicity was estimated by integrating in vitro study results with physiologically-based biokinetic models for eight neurotoxic compounds (benzene, toluene, lindane, acrylamide, parathion/oxon, caffeine, diazepam and phenytoin). In vitro studies on general and specific neurotoxicity were performed and biotransformation and tissue-blood distribution studies were used in modelling the biokinetic behaviour of the compounds. Subsequently, neurotoxicity was estimated from the integrated in vitro and kinetic studies. These results were compared with in vivo data from the literature on minimal neurotoxicity for these compounds, such as lowest-observed-effect levels (LOELs). The discrepancy between estimated and experimental LOELs ranged from 2- to 10-fold. LOEL estimates for compounds with a relatively low toxicity were more accurate than for compounds with a relatively high toxicity. LOELs for the most active compounds could only be established after consideration of additional in vitro results from the literature. The present study has generated encouraging results on the risk assessment of chemicals from in vitro studies and computer simulations and has identified some key directions for future research.
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| 39. |
- Deka, P. P., et al.
(author)
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The MeerKAT Absorption Line Survey (MALS) Data Release. I. Stokes I Image Catalogs at 1-1.4 GHz
- 2024
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In: Astrophysical Journal, Supplement Series. - 1538-4365 .- 0067-0049. ; 270:2
-
Journal article (peer-reviewed)abstract
- The MeerKAT Absorption Line Survey (MALS) has observed 391 telescope pointings at the L band (900-1670 MHz) at delta less than or similar to +20 degrees. We present radio continuum images and a catalog of 495,325 (240,321) radio sources detected at a signal-to-noise ratio (S/N) > 5 over an area of 2289 deg(2) (1132 deg(2)) at 1006 MHz (1381 MHz). Every MALS pointing contains a central bright radio source (S 1 GHz greater than or similar to 0.2 Jy). The median spatial resolution is 12 ''(8 ''). The median rms noise away from the pointing center is 25 mu Jy beam(-1) (22 mu Jy beam-1) and is within similar to 15% of the achievable theoretical sensitivity. The flux density scale ratio and astrometric accuracy deduced from multiply observed sources in MALS are <1% (8% scatter) and 1 '', respectively. Through comparisons with NVSS and FIRST at 1.4 GHz, we establish the catalog's accuracy in the flux density scale and astrometry to be better than 6% (15% scatter) and 0.'' 8, respectively. The median flux density offset is higher (9%) for an alternate beam model based on holographic measurements. The MALS radio source counts at 1.4 GHz are in agreement with literature. We estimate spectral indices (alpha) of a subset of 125,621 sources (S/N > 8), confirm the flattening of spectral indices with decreasing flux density, and identify 140 ultra-steep-spectrum (alpha < -1.3) sources as prospective high-z radio galaxies (z > 2). We have identified 1308 variable and 122 transient radio sources comprising primarily active galactic nuclei that demonstrate long-term (26 yr) variability in their observed flux densities. The MALS catalogs and images are publicly available at https://mals.iucaa.in.
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| 40. |
- Falstad, Niklas, 1987, et al.
(author)
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CON-quest: Searching for the most obscured galaxy nuclei
- 2021
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 649
-
Journal article (peer-reviewed)abstract
- Context. Some luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) host extremely compact (r < 100 pc) and dusty nuclei. The high extinction associated with large column densities of gas and dust toward these objects render them hard to detect at many wavelengths. The intense infrared radiation arising from warm dust in these sources can provide a significant fraction of the bolometric luminosity of the galaxy and is prone to excite vibrational levels of molecules such as HCN. This results in emission from the rotational transitions of vibrationally excited HCN (HCN-vib); the brightest emission is found in compact obscured nuclei (CONs; ςHCN-vib > 1 L⊙ pc-2 in the J = 3-2 transition). However, there have been no systematic searches for CONs, and it is unknown how common they are. Aims. We aim to establish how common CONs are in the local Universe (z < 0.08), and whether their prevalence depends on the luminosity or other properties of the host galaxy. Methods. We conducted an Atacama Large Millimeter/submillimeter Array survey of the rotational J = 3-2 transition of HCN-vib in a volume-limited sample of 46 far-infrared luminous galaxies. Results. Compact obscured nuclei are identified in 38-13+18% of the ULIRGs, 21-6+12% of the LIRGs, and 0-0+9% of the lower luminosity galaxies. We find no dependence on the inclination of the host galaxy, but strong evidence of lower IRAS 25 μm to 60 μm flux density ratios (f25/f60) in CONs (with the exception of one galaxy, NGC 4418) compared to the rest of the sample. Furthermore, we find that CONs have stronger silicate features (s9.7 μm), but similar polycyclic aromatic hydrocarbon equivalent widths (EQW6.2 μm) compared to other galaxies. Along with signatures of molecular inflows seen in the far-infrared in most CONs, submillimeter observations also reveal compact, often collimated, outflows. Conclusions. In the local Universe, CONs are primarily found in (U)LIRGs, in which they are remarkably common. As such systems are often highly disturbed, inclinations are difficult to estimate, and high-resolution continuum observations of the individual nuclei are required to determine if the CON phenomenon is related to the inclinations of the nuclear disks. Further studies of the in- A nd outflow properties of CONs should also be conducted to investigate how these are connected to each other and to the CON phenomenon. The lower f25/f60 ratios in CONs as well as the results for the mid-infrared diagnostics investigated (EQW6.2 μm and s9.7 μm) are consistent with the notion that large dust columns gradually shift the radiation from the hot nucleus to longer wavelengths, making the mid- A nd far-infrared "photospheres"significantly cooler than the interior regions. Finally, to assess the importance of CONs in the context of galaxy evolution, it is necessary to extend this study to higher redshifts where (U)LIRGs are more common.
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| 41. |
- Falstad, Niklas, 1987, et al.
(author)
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Hidden or missing outflows in highly obscured galaxy nuclei?
- 2019
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 623
-
Journal article (peer-reviewed)abstract
- Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib), which is thought to trace warm and highly enshrouded galaxy nuclei. It has been suggested that the most intense HCN-vib emission from a galaxy is connected to a phase of nuclear growth that occurs before the nuclear feedback processes have been fully developed. Aims. We aim to investigate if there is a connection between the presence of strong HCN-vib emission and the development of feedback in (ultra)luminous infrared galaxies ((U)LIRGs). Methods. We collected literature and archival data to compare the luminosities of rotational lines of HCN-vib, normalized to the total infrared luminosity, to the median velocities of 119 μm OH absorption lines, potentially indicating outflows, in a total of 17 (U)LIRGs. Results. The most HCN-vib luminous systems all lack signatures of significant molecular outflows in the far-infrared OH absorption lines. However, at least some of the systems with bright HCN-vib emission have fast and collimated outflows that can be seen in spectral lines at longer wavelengths, including in millimeter emission lines of CO and HCN (in its vibrational ground state) and in radio absorption lines of OH. Conclusions. We conclude that the galaxy nuclei with the highest L HCN-vib /L IR do not drive wide-angle outflows that are detectable using the median velocities of far-infrared OH absorption lines. This is possibly because of an orientation effect in which sources oriented in such a way that their outflows are not along our line of sight also radiate a smaller proportion of their infrared luminosity in our direction. It could also be that massive wide-angle outflows destroy the deeply embedded regions responsible for bright HCN-vib emission, so that the two phenomena cannot coexist. This would strengthen the idea that vibrationally excited HCN traces a heavily obscured stage of evolution before nuclear feedback mechanisms are fully developed.
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| 42. |
- Fernandez-Ontiveros, J. A., et al.
(author)
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A CO molecular gas wind 340 pc away from the Seyfert 2 nucleus in ESO420-G13 probes an elusive radio jet*
- 2020
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 633
-
Journal article (peer-reviewed)abstract
- A prominent jet-driven outflow of CO(2-1) molecular gas is found along the kinematic minor axis of the Seyfert 2 galaxy ESO 420-G13, at a distance of 340-600 pc from the nucleus. The wind morphology resembles the characteristic funnel shape, formed by a highly collimated filamentary emission at the base, and likely traces the jet propagation through a tenuous medium, until a bifurcation point at 440 pc. Here the jet hits a dense molecular core and shatters, dispersing the molecular gas into several clumps and filaments within the expansion cone. We also trace the jet in ionised gas within the inner less than or similar to 340 pc using the [NeII](12.8 mu m) line emission, where the molecular gas follows a circular rotation pattern. The wind outflow carries a mass of similar to 8 x 10(6) M-circle dot at an average wind projected speed of similar to 160 km s(-1), which implies a mass outflow rate of similar to 14 M-circle dot yr(-1). Based on the structure of the outflow and the budget of energy and momentum, we discard radiation pressure from the active nucleus, star formation, and supernovae as possible launching mechanisms. ESO 420-G13 is the second case after NGC 1377 where a previously unknown jet is revealed through its interaction with the interstellar medium, suggesting that unknown jets in feeble radio nuclei might be more common than expected. Two possible jet-cloud configurations are discussed to explain an outflow at this distance from the AGN. The outflowing gas will likely not escape, thus a delay in the star formation rather than quenching is expected from this interaction, while the feedback effect would be confined within the central few hundred parsecs of the galaxy.
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| 43. |
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| 44. |
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| 45. |
- Grasselli, Giacomo, et al.
(author)
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ESICM guidelines on acute respiratory distress syndrome : definition, phenotyping and respiratory support strategies
- 2023
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In: Intensive Care Medicine. - : Springer Nature. - 0342-4642 .- 1432-1238. ; 49, s. 727-759
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Journal article (peer-reviewed)abstract
- The aim of these guidelines is to update the 2017 clinical practice guideline (CPG) of the European Society of Intensive Care Medicine (ESICM). The scope of this CPG is limited to adult patients and to non-pharmacological respiratory support strategies across different aspects of acute respiratory distress syndrome (ARDS), including ARDS due to coronavirus disease 2019 (COVID-19). These guidelines were formulated by an international panel of clinical experts, one methodologist and patients' representatives on behalf of the ESICM. The review was conducted in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations. We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to assess the certainty of evidence and grade recommendations and the quality of reporting of each study based on the EQUATOR (Enhancing the QUAlity and Transparency Of health Research) network guidelines. The CPG addressed 21 questions and formulates 21 recommendations on the following domains: (1) definition; (2) phenotyping, and respiratory support strategies including (3) high-flow nasal cannula oxygen (HFNO); (4) non-invasive ventilation (NIV); (5) tidal volume setting; (6) positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM); (7) prone positioning; (8) neuromuscular blockade, and (9) extracorporeal life support (ECLS). In addition, the CPG includes expert opinion on clinical practice and identifies the areas of future research.
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| 46. |
- Hascoët, Sebastien, et al.
(author)
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Outcomes of transcatheter pulmonary SAPIEN 3 valve implantation: an international registry.
- 2023
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In: European heart journal. - 1522-9645. ; 45:3, s. 198-210
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Journal article (peer-reviewed)abstract
- Transcatheter pulmonary valve implantation (TPVI) is indicated to treat right-ventricular outflow tract (RVOT) dysfunction related to congenital heart disease (CHD). Outcomes of TPVI with the SAPIEN 3 valve that are insufficiently documented were investigated in the EUROPULMS3 registry of SAPIEN 3-TPVI.Patient-related, procedural, and follow-up outcome data were retrospectively assessed in this observational cohort from 35 centres in 15 countries.Data for 840 consecutive patients treated in 2014-2021 at a median age of 29.2 (19.0-41.6) years were obtained. The most common diagnosis was conotruncal defect (70.5%), with a native or patched RVOT in 50.7% of all patients. Valve sizes were 20, 23, 26, and 29mm in 0.4%, 25.5%, 32.1%, and 42.0% of patients, respectively. Valve implantation was successful in 98.5% [95% confidence interval (CI), 97.4%-99.2%] of patients. Median follow-up was 20.3 (7.1-38.4) months. Eight patients experienced infective endocarditis; 11 required pulmonary valve replacement, with a lower incidence for larger valves (P = .009), and four experienced pulmonary valve thrombosis, including one who died and three who recovered with anticoagulation. Cumulative incidences (95%CI) 1, 3, and 6 years after TPVI were as follows: infective endocarditis, 0.5% (0.0%-1.0%), 0.9% (0.2%-1.6%), and 3.8% (0.0%-8.4%); pulmonary valve replacement, 0.4% (0.0%-0.8%), 1.3% (0.2%-2.4%), and 8.0% (1.2%-14.8%); and pulmonary valve thrombosis, 0.4% (0.0%-0.9%), 0.7% (0.0%-1.3%), and 0.7% (0.0%-1.3%), respectively.Outcomes of SAPIEN 3 TPVI were favourable in patients with CHD, half of whom had native or patched RVOTs.
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| 47. |
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| 48. |
- Muller, Sebastien, 1976, et al.
(author)
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Protonated acetylene in the z = 0.89 molecular absorber toward PKS 1830-211
- 2024
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In: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 683
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Journal article (peer-reviewed)abstract
- We report the first interstellar identification of protonated acetylene, C2H3+, a fundamental hydrocarbon, in the z = 0.89 molecular absorber toward the gravitationally lensed quasar PKS 1830-211. The molecular species is identified from clear absorption features corresponding to the 212-101 (rest frequency 494.034 GHz) and 111-000 (431.316 GHz) ground-state transitions of ortho and para forms of C2H3+, respectively, in ALMA spectra toward the southwestern image of PKS 1830-211, where numerous molecules, including other hydrocarbons, have already been detected. From the simple assumption of local thermodynamic equilibrium (LTE) with cosmic microwave background photons and an ortho-to-para ratio of three, we estimate a total C2H3+ column density of 2 × 1012 cm-2 and an abundance of 10-10 compared to H2. However, formation pumping could affect the population of metastable states, yielding a C2H3+ column density higher than the LTE value by a factor of a few. We explore possible routes to the formation of C2H3+, mainly connected to acetylene and methane, and find that the methane route is more likely in PDR environment. As one of the initial hydrocarbon building blocks, C2H3+ is thought to play an important role in astrochemistry, in particular in the formation of more complex organic molecules.
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| 49. |
- Nishimura, Y., et al.
(author)
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CON-quest: II. Spatially and spectrally resolved HCN/HCO + line ratios in local luminous and ultraluminous infrared galaxies
- 2024
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In: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 686
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Journal article (peer-reviewed)abstract
- Context. Nuclear regions of ultraluminous and luminous infrared galaxies (U/LIRGs) are powered by starbursts and/or active galactic nuclei (AGNs). These regions are often obscured by extremely high columns of gas and dust. Molecular lines in the submillimeter windows have the potential to determine the physical conditions of these compact obscured nuclei (CONs). Aims. We aim to reveal the distributions of HCN and HCO+ emission in local U/LIRGs and investigate whether and how they are related to galaxy properties. Methods. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have conducted sensitive observations of the HCN J = 3-2 and HCO+J = 3-2 lines toward 23 U/LIRGs in the local Universe (z < 0.07) with a spatial resolution of ~0.3″ ( ~50-400 pc). Results. We detected both HCN and HCO+ in 21 galaxies, only HCN in one galaxy, and neither in one galaxy. The global HCN/HCO+ line ratios, averaged over scales of ~0.5-4 kpc, range from 0.4 to 2.3, with an unweighted mean of 1.1. These line ratios appear to have no systematic trend with bolometric AGN luminosity or star formation rate. The line ratio varies with position and velocity within each galaxy, with an average interquartile range of 0.38 on a spaxel-by-spaxel basis. In eight out of ten galaxies known to have outflows and/or inflows, we found spatially and kinematically symmetric structures of high line ratios. These structures appear as a collimated bicone in two galaxies and as a thin spherical shell in six galaxies. Conclusions. Non-LTE analysis suggests that the high HCN/HCO+ line ratio in outflows is predominantly influenced by the abundance ratio. Chemical model calculations indicate that the enhancement of HCN abundance in outflows is likely due to high-temperature chemistry triggered by shock heating. These results imply that the HCN/HCO+ line ratio can aid in identifying the outflow geometry when the shock velocity of the outflows is sufficiently high to heat the gas.
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