EDP Sciences
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Highlighted papers
Effect of rotational mixing and metallicity on hot star wind mass-loss rates (Krticka et al
Thursday, 10 July 2014 08:00

Vol. 567
In section 7. Stellar structure and evolution

Effect of rotational mixing and metallicity on the hot star wind mass-loss rates

by J. Krticka and J. Kubat A&A 567, A63


The metallicity dependence of the mass loss rate of hot stars is often described as scaling with the overall metallicity. The authors look into the impact of CNO processed material on the mass loss rate. Their calculations show that while it has small effect for solar metallicity stars, it can have important consequences for metal-poor stars.

 
Grain growth in the envelopes and disks of Class I protostars (Miotello et al.)
Monday, 07 July 2014 08:28

Vol. 567
In section 6. Interstellar and circumstellar matter

Grain growth in the envelopes and disks of Class I protostars

by A. Miotello, L. Testi, G. Lodato, L. Ricci, G. Rosotti, K. Brooks, A. Maury, and A. Natta, A&A 567, A32


alt

The authors present new 3 mm ATCA data of two Class I young stellar objects, Elias29 and WL12, which are expected to be surrounded by both an extended envelope and a disk. In the (u, v) plane the two sources present a similar behavior. First, there is a nearly constant emission at long baselines, which suggests the presence of an unresolved component. Second, the fluxes increase at short baselines, indicating the presence of an extended envelope. Our data analysis leads to unusually low values of the spectral index, which indicates that mm-sized dust grains have already formed at this early stage both in the envelopes and in the central, compact disk-like structures. This result may provide new constraints for the initial dust evolution in protoplanetary disks.

 
Mapping the Milky Way bulge at high resolution [...] (Schultheis et al.)
Monday, 23 June 2014 08:23

Vol. 566
In section 5. Galactic structure, stellar clusters and populations

Mapping the Milky Way bulge at high resolution: the 3D dust extinction, CO and X factor maps

by M. Schultheis, B.Q. Chen, B.W. Jiang, et al., A&A 566, A120


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Although we live inside a galaxy, we know more about the distribution of the dense and dusty interstellar medium of nearby galaxies than that of our own. Schultheis et al. here use the VVV near-infrared survey together with the Besançon stellar population synthesis model of the Milky Way to construct the highest resolution 3D extinction map of the inner Galaxy to date. The map has a resolution of 6 arcmin and traces dust extinction up to 10 kpc along the Galactic plane and up to 30 magnitudes of visual extinction (about 3 mag in Ak). The authors find a large amount of material in front of the Galactic bar, specifically, between 5-7 kpc. Knowing the dust distribution in the Milky Way will provide an additional way to interpret molecular line data, in particular toward the Galactic center and will help better characterize the stellar population of the Galactic bulge.

 
Dynamical star-disk interaction in the young stellar system V354 Mon (Fonseca et al.)
Monday, 07 July 2014 11:35

Vol. 567
In section 7. Stellar structure and evolution

Dynamical star-disk interaction in the young stellar system V354 Monocerotis

by N.N.J. Fonseca, S.H.P. Alencar, J. Bouvier, et al. A&A 567, A39


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The light curve of the classical T Tauri star V354 Mon shows periodical minima that vary in depth and width at each rotational cycle. The photometric observations carried out by the authors indicate that the system becomes slightly bluer as the flux increases. The spectra obtained by the authors exhibit variable emission lines, with redshifted absorption components associated with a disk wind and blueshifted ones with the accretion process, which confirms the magnetospheric accretion scenario. From the analysis of the photometric and spectroscopic data, the authors identify correlations between the emission line variability and the light-curve modulation of the young system, such as the occurrence of pronounced redshifted absorption in the Hα line at the epoch of minimum flux. The authors find that the accretion funnel is seen projected onto the stellar photosphere along the line of sight, which implies that the hot spot coincides with the light-curve minima. They conclude that material non-uniformly distributed in the inner part of the circumstellar disk is the main cause of the photometric modulation, but do not exclude that there might be hot and cold spots at the stellar surface. The distortion in the inner part of the disk is thought to be created by the dynamical interaction between the stellar magnetosphere and the circumstellar disk, as also observed in the T Tauri star AA Tau and predicted by magneto-hydrodynamical numerical simulations.

 
PKS 1830-211 (Muller er al.)
Friday, 20 June 2014 09:10

Vol. 566
In section 4. Extragalactic astronomy

An ALMA Early Science survey of molecular absorption lines toward PKS1830-211. Analysis of the absorption profiles

by S. Muller, F. Combes, M. Guelin, et al. A&A 566, A112



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Detection of chloronium and measurement of the 35Cl/37Cl isotopic ratio at z=0.89 toward PKS 1830-211

by S. Muller, J.H. Black, M. Guelin, et al. A&A 566, L6


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alt

Gravitational lensing has made various "gifts to humanity" and one of these is illustrated in the two papers by Muller et al. highlighted in this issue. These authors have used ALMA to make a molecular spectral scan of absorption lines in a foreground galaxy (the lensing galaxy) at z=0.89 against the background of the blazar PKS 1830-211. This allows them to examine the composition of "normal" molecular gas at high red shift. Interestingly, the abundance distribution is similar to what is seen in Milky Way clouds which is somewhat surprising given the expected variation in metallicity, dust properties, etc. A byproduct of this research was the detection of both the 35Cl and 37Cl forms of chloronium (protonated HCl or H2CL+) with an isotope ratio similar to the one in Milky Way clouds .

 
Herschel-Planck optical-depth maps. I. Orion (Lombardi et al.)
Monday, 09 June 2014 11:47

Vol. 566
In section 6. Interstellar and circumstellar matter

Herschel-Planck dust optical-depth and column-density maps. I. Method description and results for Orion

by M. Lombardi, H. Bouy, J. Alves, and C. Lada, A&A 566, A45


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Our understanding of the star formation rate in galaxies other than our own is based on various forms of the Schmidt law, which relates the star formation rate to gas mass. The Schmidt law is empirical and is typically valid on size scales of a few hundred parsecs or more. It clearly would be interesting to establish the validity of this type of relationship in the Milky Way, with the ultimate aim of deriving the physical basis of the Milky Way. This requires studying the density or column density distribution in Milky Way clouds where young stars are forming. The study of the Orion complex by Lombardi et al. does this by combining dust emission maps from Herschel, and Planck with dust extinction maps based on the 2MASS survey. The result is a map covering more than 2 orders of magnitude in column density (from a K extinction of 0.05 mag to 10 mag.), which shows that the local protostar column density varies with approximately the square of the gas column.

 

Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

Mirror sites: CDS | EDP Sciences
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