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| 4. |
- Espada, D., et al.
(författare)
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Star Formation Efficiencies at Giant Molecular Cloud Scales in the Molecular Disk of the Elliptical Galaxy NGC 5128 (Centaurus A)
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 887:1
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Tidskriftsartikel (refereegranskat)abstract
- We present ALMA CO (1-0) observations toward the dust lane of the nearest elliptical and radio galaxy, NGC 5128 (Centaurus A), with high angular resolution (similar to 1 '', or 18 pc), including information from large to small spatial scales and total flux. We find a total molecular gas mass of 1.6 x 10(9) M-circle dot and reveal the presence of filamentary components more extended than previously seen, up to a radius of 4 kpc. We find that the global star formation rate is similar to 1 M-circle dot yr(-1), which yields a star formation efficiency (SFE) of 0.6 Gyr(-1) (depletion time tau = 1.5 Gyr), similar to those in disk galaxies. We show the most detailed view to date (40 pc resolution) of the relation between molecular gas and star formation within the stellar component of an elliptical galaxy, from a scale of several kiloparsecs to the circumnuclear region close to the powerful radio jet. Although on average the SFEs are similar to those of spiral galaxies, the circumnuclear disk (CND) presents SFEs of 0.3 Gyr(-1), lower by a factor of 4 than the outer disk. The low SFE in the CND is in contrast to the high SFEs found in the literature for the circumnuclear regions of some nearby disk galaxies with nuclear activity, probably as a result of larger shear motions and longer active galactic nucleus feedback. The higher SFEs in the outer disk suggest that only central molecular gas or filaments with sufficient density and strong shear motions will remain in similar to 1 Gyr, which will later result in the compact molecular distributions and low SFEs usually seen in other giant ellipticals with cold gas.
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| 7. |
- Espada, D., et al.
(författare)
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Disentangling the Circumnuclear Environs of Centaurus A. III. An Inner Molecular Ring, Nuclear Shocks, and the CO to Warm H-2 Interface
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 843:2
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Tidskriftsartikel (refereegranskat)abstract
- We present the distribution and kinematics of the molecular gas in the circumnuclear disk (CND; 400 pc ×200 pc) of Centaurus A with resolutions of ∼5 pc (0.″3) and shed light onto the mechanism feeding the active galactic nucleus (AGN) using CO(3-2), HCO + (4-3), HCN(4-3), and CO(6-5) observations obtained with ALMA. Multiple filaments or streamers of tens to a hundred parsec scale exist within the CND, which form a ring-like structure with an unprojected diameter of 9″ ×6″ (162 pc ×108 pc) and a position angle P.A. ≃ 155°. Inside the nuclear ring, there are two leading and straight filamentary structures with lengths of about 30-60 pc at P.A. ≃ 120° on opposite sides of the AGN, with a rotational symmetry of 180° and steeper position-velocity diagrams, which are interpreted as nuclear shocks due to non-circular motions. Along the filaments, and unlike other nearby AGNs, several dense molecular clumps present low HCN/HCO + (4-3) ratios (≲0.5). The filaments abruptly end in the probed transitions at r ≃ 20 pc from the AGN, but previous near-IR H 2 (J = 1-0)S(1) maps show that they continue in an even warmer gas phase (T ∼ 1000 K), winding up in the form of nuclear spirals, and forming an inner ring structure with another set of symmetric filaments along the N-S direction and within r ≃ 10 pc. The molecular gas is governed primarily by non-circular motions, being the successive shock fronts at different scales where loss of angular momentum occurs, a mechanism that may feed efficiently powerful radio galaxies down to parsec scales.
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| 9. |
- Gruber, M., et al.
(författare)
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Operation time and clinical outcomes for open infrarenal abdominal aortic aneurysms to remain stable in the endovascular era
- 2023
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Ingår i: Frontiers in Cardiovascular Medicine. - : Frontiers Media S.A.. - 2297-055X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Endovascular aortic repair (EVAR) has become a routine procedure worldwide. Ultimately, the increasing number of EVAR cases entails changing conditions for open surgical repair (OSR) regarding patient selection, complexity, and surgical volume. This study aimed to assess the time trends of open abdominal aortic aneurysm (AAA) repair in a high-volume single center in Austria over a period of 20 years, focusing on the operation time and clinical outcomes.Materials and methods: A retrospective analysis of all patients treated for infrarenal AAAs with OSR or EVAR between January 2000 and December 2019 was performed. Infrarenal AAA was defined as the presence of a >10-mm aortic neck. Cases with ruptured or juxtarenal AAAs were excluded from the analysis. Two cohorts of patients treated with OSR at different time periods, namely, 2000-2009 and 2010-2019, were assessed regarding demographical and procedure details and clinical outcomes. The time periods were defined based on the increasing single-center trend toward the EVAR approach from 2010 onward.Results: A total of 743 OSR and 766 EVAR procedures were performed. Of OSR cases, 589 were infrarenal AAAs. Over time, the EVAR to OSR ratio was stable at around 50:50 (p = 0.488). After 2010, history of coronary arterial bypass (13.4% vs. 7.2%, p = 0.027), coronary artery disease (38.1% vs. 25.1%, p = 0.004), peripheral vascular disease (35.1% vs. 21.3%, p = 0.001), and smoking (61.6% vs. 34.3%, p < 0.001) decreased significantly. Age decreased from 68 to 66 years (p = 0.023). The operation time for OSR remained stable (215 vs. 225 min, first vs. second time period, respectively, p = 0.354). The intraoperative (5.8% vs. 7.2%, p = 0.502) and postoperative (18.3% vs. 20.8%, p = 0.479) complication rates also remained stable. The 30-day mortality rate did not change over both time periods (3.0% vs. 2.4%, p = 0.666).Conclusion: Balanced EVAR to OSR ratio, similar complexity of cases, and volume over the two decades in OSR showed stable OSR time without compromise in clinical outcomes.
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| 12. |
- Miura, R.E., et al.
(författare)
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A giant molecular cloud catalogue in the molecular disc of the elliptical galaxy NGC 5128 (Centaurus A)
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 504:4, s. 6198-6215
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Tidskriftsartikel (refereegranskat)abstract
- We present the first census of giant molecular clouds (GMCs) complete down to 106 M⊙ and within the inner 4 kpc of the nearest giant elliptical and powerful radio galaxy, Centaurus A. We identified 689 GMCs using CO(1-0) data with 1 arcsec spatial resolution (∼20 pc) and 2 km s-1 velocity resolution obtained with the Atacama Large Millimeter/submillimeter Array. The I(CO)-N(H2) conversion factor based on the virial method is XCO = (2 ± 1) × 1020 cm-2(K km s-1)-1 for the entire molecular disc, consistent with that of the discs of spiral galaxies including the Milky Way, and XCO = (5 ± 2) × 1020 cm-2(K km s-1)-1 for the circumnuclear disc (CND; within a galactocentric radius of 200 pc). We obtained the GMC mass spectrum distribution and find that the best truncated power-law fit for the whole molecular disc, with index γ≃ -2.41 ± 0.02 and upper cut-off mass $\sim \! 1.3\times 10^{7}\, \mathrm{M}_{\odot }$, is also in agreement with that of nearby disc galaxies. A trend is found in the mass spectrum index from steep to shallow as we move to inner radii. Although the GMCs are in an elliptical galaxy, the general GMC properties in the molecular disc are as in spiral galaxies. However, in the CND, large offsets in the line-width-size scaling relations (∼0.3 dex higher than those in the GMCs in the molecular disc), a different XCO factor, and the shallowest GMC mass distribution shape (γ= -1.1 ± 0.2) all suggest that there the GMCs are most strongly affected by the presence of the active galactic nucleus and/or shear motions.
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| 14. |
- Sormani, Mattia C., et al.
(författare)
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Self-consistent modelling of the Milky Way's nuclear stellar disc
- 2022
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 512:2, s. 1857-1884
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Tidskriftsartikel (refereegranskat)abstract
- The nuclear stellar disc (NSD) is a flattened high-density stellar structure that dominates the gravitational field of the Milky Way at Galactocentric radius $30\, {\rm pc}\lesssim R\lesssim 300\, {\rm pc}$. We construct axisymmetric self-consistent equilibrium dynamical models of the NSD in which the distribution function is an analytic function of the action variables. We fit the models to the normalized kinematic distributions (line-of-sight velocities + VIRAC2 proper motions) of stars in the NSD survey of Fritz et al., taking the foreground contamination due to the Galactic Bar explicitly into account using an N-body model. The posterior marginalized probability distributions give a total mass of $M{\rm NSD} = 10.5{+1.1}{-1.0} \times 108 \, \, \rm M\odot$, roughly exponential radial and vertical scale lengths of $R{\rm disc} = 88.6{+9.2}{-6.9} \, {\rm pc}$ and $H{\rm disc}=28.4{+5.5}{-5.5} \, {\rm pc}$, respectively, and a velocity dispersion $\sigma \simeq 70\, {\rm km\, s{-1}}$ that decreases with radius. We find that the assumption that the NSD is axisymmetric provides a good representation of the data. We quantify contamination from the Galactic Bar in the sample, which is substantial in most observed fields. Our models provide the full 6D (position + velocity) distribution function of the NSD, which can be used to generate predictions for future surveys. We make the models publicly available as part of the software package agama.
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| 15. |
- Alfaro-Cuello, M., et al.
(författare)
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A Deep View into the Nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. II. Kinematic Characterization of the Stellar Populations
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 892:1
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Tidskriftsartikel (refereegranskat)abstract
- The Sagittarius dwarf spheroidal galaxy is in an advanced stage of disruption but still hosts its nuclear star cluster (NSC), M54, at its center. In this paper, we present a detailed kinematic characterization of the three stellar populations present in M54: Young metal-rich (YMR); intermediate-age metal-rich (IMR); and old metal-poor (OMP), based on the spectra of 6500 individual M54 member stars extracted from a large Multi-Unit Spectroscopic Explorer (MUSE)/Very Large Telescope data set. We find that the OMP population is slightly flattened with a low amount of rotation (0.8 km s-1) and with a velocity dispersion that follows a Plummer profile. The YMR population displays a high amount of rotation (5 km s-1) and a high degree of flattening, with a lower and flat velocity dispersion profile. The IMR population shows a high but flat velocity dispersion profile, with some degree of rotation (2 km s-1). We complement our MUSE data with information from Gaia DR2 and confirm that the stars from the OMP and YMR populations are comoving in 3D space, suggesting that they are dynamically bound. While dynamical evolutionary effects (e.g., energy equipartition) are able to explain the differences in velocity dispersion between the stellar populations, the strong differences in rotation indicate different formation paths for the populations, as supported by an N-body simulation tailored to emulate the YMR-OMP system. This study provides additional evidence for the M54 formation scenario proposed in our previous work, where this NSC formed via GC accretion (OMP) and in situ formation from gas accretion in a rotationally supported disk (YMR).
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| 17. |
- Davis, Timothy A., et al.
(författare)
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Revealing the intermediate-mass black hole at the heart of the dwarf galaxy NGC404 with sub-parsec resolution ALMA observations
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 496:4, s. 4061-4078
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Tidskriftsartikel (refereegranskat)abstract
- We estimate the mass of the intermediate-mass black hole at the heart of the dwarf elliptical galaxy NGC 404 using Atacama Large Millimetre/submillimetre Array (ALMA) observations of the molecular interstellar medium at an unprecedented linear resolution of approximate to 0.5 pc, in combination with existing stellar kinematic information. These ALMA observations reveal a central disc/torus of molecular gas clearly rotating around the black hole. This disc is surrounded by a morphologically and kinematically complex flocculent distribution of molecular clouds, that we resolve in detail. Continuum emission is detected from the central parts of NGC 404, likely arising from the Rayleigh-Jeans tail of emission from dust around the nucleus, and potentially from dusty massive star-forming clumps at discrete locations in the disc. Several dynamical measurements of the black hole mass in this system have been made in the past, but they do not agree. We show here that both the observed molecular gas and stellar kinematics independently require a approximate to 5 x 10(5) M-circle dot black hole once we include the contribution of the molecular gas to the potential. Our best estimate comes from the high-resolution molecular gas kinematics, suggesting the black hole mass of this system is 5.5(-3.8)(+4.1) x 10(5) M-circle dot (at the 99 per cent confidence level), in good agreement with our revised stellar kinematic measurement and broadly consistent with extrapolations from the black hole mass-velocity dispersion and black hole massbulge mass relations. This highlights the need to accurately determine the mass and distribution of each dynamically important component around intermediate-mass black holes when attempting to estimate their masses.
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| 18. |
- Fellström, Bengt, 1942-, et al.
(författare)
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Risk factors for reaching renal endpoints in the Assessment of Lescol in Renal Transplantation (ALERT) trial
- 2005
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Ingår i: Transplantation. - 0041-1337 .- 1534-6080. ; 79:2, s. 205-212
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Tidskriftsartikel (refereegranskat)abstract
- Background. The aim of the study was to identity risk factors for long-term renal transplant function and development of chronic allograft nephropathy (CAN) in renal transplant recipients included in the Assessment of Lescol in Renal Transplantation (ALERT) trial. Methods. The ALERT trial was a randomized, double-blind, placebo-controlled study of the effect of fluvastatin, 40 and 80 mg/day, in renal transplant recipients who were randomized to receive fluvastatin (Lescol) (n=1,050) or placebo (n=1,052) over 5 to 6 years of follow-up. Renal endpoints including graft loss or doubling of serum creatinine or death were analyzed by univariate and multivariate regression analysis in the placebo group. Results. There were 137 graft losses (13.5%) in the placebo group, mainly caused by CAN (82%). Univariate risk factors for graft loss or doubling of serum creatinine were as follows: serum creatinine, proteinuria, hypertension, pulse pressure, time since transplantation, donor age, human leukocyte antigen-DR mismatches, treatment for rejection, low high-density lipoprotein cholesterol, and smoking. Multivariate analysis revealed independent risk factors for graft loss as follows: serum creatinine (relative risk [RR], 3.12 per 100-µM increase), proteinuria (RR, 1.64 per 1-g/24 hr increase), and pulse pressure (RR, 1.12 per 10 mm Hg), whereas age was a protective factor. With patient death in the composite endpoint, diabetes mellitus, smoking, age, and number of transplantations were also risk factors. Conclusions. Independent risk factors for graft loss or doubling of serum creatinine or patient death are mainly related to renal transplant function, proteinuria, and blood pressure, which emphasizes the importance of renoprotective treatment regimens in this population.
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| 19. |
- Holdaas, H., et al.
(författare)
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Effect of fluvastatin on cardiac outcomes in renal transplant recipients : A multicentre, randomised, placebo-controlled trial
- 2003
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Ingår i: The Lancet. - 0140-6736 .- 1474-547X. ; 361:9374, s. 2024-2031
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Tidskriftsartikel (refereegranskat)abstract
- Background: Renal transplant recipients are at increased risk of premature cardiovascular disease. Although statins reduce cardiovascular risk in the general population, their efficacy and safety in renal transplant recipients have not been established. We investigated the effects of fluvastatin on cardiac and renal endpoints in this population. Methods: We did a multicentre, randomised, double-blind, placebo-controlled trial in 2102 renal transplant recipients with total cholesterol 4·0-9·0 mmol/L. We randomly assigned patients fluvastatin (n=1050) or placebo (n=1052) and follow up was for 5-6 years. The primary endpoint was the occurrence of a major adverse cardiac event, defined as cardiac death, non-fatal myocardial infarction (MI), or coronary intervention procedure. Secondary endpoints were individual cardiac events, combined cardiac death or non-fatal MI, cerebrovascular events, non-cardiovascular death, all-cause mortality, and graft loss or doubling of serum creatinine. Analysis was by intention to treat. Findings: After a mean follow-up of 5·1 years, fluvastatin lowered LDL cholesterol concentrations by 32%. Risk reduction with fluvastatin for the primary endpoint (risk ratio 0·83 [95% CI 0·64-1·06], p=0·139) was not significant, although there were fewer cardiac deaths or non-fatal MI (70 vs 104, 0·65 [0·48-0·88] p=0·005) in the fluvastatin group than in the placebo group. Coronary intervention procedures and other secondary endpoints did not differ significantly between groups. Interpretation: Although cardiac deaths and non-fatal MI seemed to be reduced, fluvastatin did not generally reduce rates of coronary intervention procedures or mortality. Overall effects of fluvastatin were similar to those of statins in other populations.
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| 20. |
- Lang, L. F., et al.
(författare)
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Template-Based Image Reconstruction from Sparse Tomographic Data
- 2019
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Ingår i: Applied mathematics and optimization. - : Springer New York LLC. - 0095-4616 .- 1432-0606.
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Tidskriftsartikel (refereegranskat)abstract
- We propose a variational regularisation approach for the problem of template-based image reconstruction from indirect, noisy measurements as given, for instance, in X-ray computed tomography. An image is reconstructed from such measurements by deforming a given template image. The image registration is directly incorporated into the variational regularisation approach in the form of a partial differential equation that models the registration as either mass- or intensity-preserving transport from the template to the unknown reconstruction. We provide theoretical results for the proposed variational regularisation for both cases. In particular, we prove existence of a minimiser, stability with respect to the data, and convergence for vanishing noise when either of the abovementioned equations is imposed and more general distance functions are used. Numerically, we solve the problem by extending existing Lagrangian methods and propose a multilevel approach that is applicable whenever a suitable downsampling procedure for the operator and the measured data can be provided. Finally, we demonstrate the performance of our method for template-based image reconstruction from highly undersampled and noisy Radon transform data. We compare results for mass- and intensity-preserving image registration, various regularisation functionals, and different distance functions. Our results show that very reasonable reconstructions can be obtained when only few measurements are available and demonstrate that the use of a normalised cross correlation-based distance is advantageous when the image intensities between the template and the unknown image differ substantially.
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| 21. |
- McCoy, M., et al.
(författare)
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ALMA Observations of the Physical and Chemical Conditions in Centaurus A
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 851:2
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Tidskriftsartikel (refereegranskat)abstract
- Centaurus A, with its gas-rich elliptical host galaxy, NGC 5128, is the nearest radio galaxy at a distance of 3.8 Mpc. Its proximity allows us to study the interaction among an active galactic nucleus, radio jets, and molecular gas in great detail. We present ALMA observations of low-J transitions of three CO isotopologues, HCN, HCO+, HNC, CN, and CCH toward the inner projected 500 pc of NGC 5128. Our observations resolve physical sizes down to 40 pc. By observing multiple chemical probes, we determine the physical and chemical conditions of the nuclear interstellar medium of NGC 5128. This region contains molecular arms associated with the dust lanes and a circumnuclear disk (CND) interior to the molecular arms. The CND is approximately 400 pc by 200 pc and appears to be chemically distinct from the molecular arms. It is dominated by dense gas tracers while the molecular arms are dominated by (CO)-C-12 and its rare isotopologues. The CND has a higher temperature, elevated CN/HCN and HCN/HNC intensity ratios, and much weaker (CO)-C-13 and (CO)-O-18 emission than the molecular arms. This suggests an influence from the AGN on the CND molecular gas. There is also absorption against the AGN with a low velocity complex near the systemic velocity and a high velocity complex shifted by about 60 km s(-1). We find similar chemical properties between the CND in emission and both the low and high velocity absorption complexes, implying that both likely originate from the CND. If the HV complex does originate in the CND, then that gas would correspond to gas falling toward the supermassive black hole.
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| 22. |
- Rasmont, Pierre, et al.
(författare)
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Climatic Risk and Distribution Atlas of European Bumblebees
- 2015
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Bok (refereegranskat)abstract
- Bumble bees represent one of the most important groups of pollinators. In addition to their ecological and economic relevance, they are also a highly charismatic group which can help to increase the interest of people in realizing, enjoying and conserving natural systems. However, like most animals, bumble bees are sensitive to climate. In this atlas, maps depicting potential risks of climate change for bumble bees are shown together with informative summary statistics, ecological background information and a picture of each European species.Thanks to the EU FP7 project STEP, the authors gathered over one million bumblebee records from all over Europe. Based on these data, they modelled the current climatic niche for almost all European species (56 species) and projected future climatically suitable conditions using three climate change scenarios for the years 2050 and 2100. While under a moderate change scenario only 3 species are projected to be at the verge of extinction by 2100, 14 species are at high risk under an intermediate change scenario. Under a most severe change scenario as many as 25 species are projected to lose almost all of their climatically suitable area, while a total of 53 species (77% of the 69 European species) would lose the main part of their suitable area.Climatic risks for bumblebees can be extremely high, depending on the future development of human society, and the corresponding effects on the climate. Strong mitigation strategies are needed to preserve this important species group and to ensure the sustainable provision of pollination services, to which they considerably contribute.
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| 23. |
- Schultheis, M., et al.
(författare)
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The nuclear stellar disc of the Milky Way : A dynamically cool and metal-rich component possibly formed from the central molecular zone
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 650
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Tidskriftsartikel (refereegranskat)abstract
- Context. The nuclear stellar disc (NSD) is, together with the nuclear star cluster (NSC) and the central massive black hole, one of the main components in the central parts of our Milky Way. However, until recently, only a few studies of the stellar content of the NSD have been obtained owing to extreme extinction and stellar crowding. Aims. We study the kinematics and global metallicities of the NSD based on the observations of K/M giant stars via a dedicated KMOS (VLT, ESO) spectroscopic survey. Methods. We traced radial velocities and metallicities, which were derived based on spectral indices (Na I and CO) along the NSD, and compared those with a Galactic bulge sample of APOGEE (DR16) and data from the NSC. Results. We find that the metallicity distribution function and the fraction of metal-rich and metal-poor stars in the NSD are different from the corresponding distributions and ratios of the NSC and the Galactic bulge. By tracing the velocity dispersion as a function of metallicity, we clearly see that the NSD is kinematically cool and that the velocity dispersion decreases with increasing metallicity contrary to the inner bulge sample of APOGEE (|b|< 4°). Using molecular gas tracers (H2CO, CO(4-3)) of the central molecular zone (CMZ), we find an astonishing agreement between the gas rotation and the rotation of the metal-rich population. This agreement indicates that the metal-rich stars could have formed from gas in the CMZ. On the other hand, the metal-poor stars show a much slower rotation profile with signs of counter-rotation, thereby indicating that these stars have a different origin. Conclusions. Coupling kinematics with global metallicities, our results demonstrate that the NSD is chemically and kinematically distinct with respect to the inner bulge, which indicates a different formation scenario.
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