Search

Start Over Subject infrared astronomy
11. Abundances of two very metal-poor stars
ID:
ivo://CDS.VizieR/J/ApJ/819/103
Title:
Abundances of two very metal-poor stars
Short Name:
J/ApJ/819/103
Date:
21 Oct 2021
Publisher:
CDS
Description:
From high resolution (R~=45000), high signal-to-noise ratio (S/N>400) spectra gathered with the Immersion Grating Infrared Spectrograph (IGRINS) in the H and K photometric bands, we have derived elemental abundances of two bright, well-known metal-poor halo stars: the red giant HD 122563 and the subgiant HD 140283. Since these stars have metallicities approaching [Fe/H]=-3, their absorption features are generally very weak. Neutral-species lines of Mg, Si, S and Ca are detectable, as well as those of the light odd-Z elements Na and Al. The derived IR-based abundances agree with those obtained from optical-wavelength spectra. For Mg and Si the abundances from the infrared transitions are improvements to those derived from shorter wavelength data. Many useful OH and CO lines can be detected in the IGRINS HD 122563 spectrum, from which derived O and C abundances are consistent to those obtained from the traditional [OI] and CH features. IGRINS high resolutions H- and K-band spectroscopy offers promising ways to determine more reliable abundances for additional metal-poor stars whose optical features are either not detectable, or too weak, or are based on lines with analytical difficulties.
12. A catalog of MIPSGAL disk and ring sources
ID:
ivo://CDS.VizieR/J/AJ/139/1542
Title:
A catalog of MIPSGAL disk and ring sources
Short Name:
J/AJ/139/1542
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of 416 extended, resolved, disk and ringlike objects as detected in the MIPSGAL 24um survey of the Galactic plane. This catalog is the result of a search in the MIPSGAL image data for generally circularly symmetric, extended "bubbles" without prior knowledge or expectation of their physical nature. Most of the objects have no extended counterpart at 8um or 70um, with less than 20% detections at each wavelength. For the 54 objects with central point sources, the sources are nearly always seen in all Infrared Array Camera bands. About 70 objects (16%) have been previously identified, with another 35 listed as Infrared Astronomical Satellite sources.
13. A catalogue of cross-matched radio/infrared/X-ray sources
ID:
ivo://CDS.VizieR/V/138
Title:
A catalogue of cross-matched radio/infrared/X-ray sources
Short Name:
V/138
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of cross-correlated radio, infrared and X-ray sources using a very restrictive selection criteria with an IDL-based code developed by us. The significance of the observed coincidences was evaluated through Monte Carlo simulations of synthetic sources following a well-tested protocol. We found 3320 coincident radio/X-ray sources with a high statistical significance characterized by the sum of error-weighted coordinate differences. For 997 of them, 2MASS counterparts were found. The percentage of chance coincidences is less than 1%. X-ray hardness ratios of well-known populations of objects were used to provide a crude representation of their X-ray spectrum and to make a preliminary diagnosis of the possible nature of unidentified X-ray sources. The results support the fact that the X-ray sky is largely dominated by Active Galactic Nuclei at high galactic latitudes (|b|>=10deg). At low galactic latitudes (|b|<=10deg) most of unidentified X-ray sources (~94%) lie at |b|>=2deg. This result suggests that most of the unidentified sources found toward the Milky Way plane are galactic objects. Well-known and unidentified sources were classified in different tables with their corresponding radio/infrared and X-ray properties. These tables are intended as a useful tool for researchers interested in particular identifications.
14. A catalogue of Spitzer dark clouds
ID:
ivo://CDS.VizieR/J/A+A/505/405
Title:
A catalogue of Spitzer dark clouds
Short Name:
J/A+A/505/405
Date:
21 Oct 2021
Publisher:
CDS
Description:
The majority of stars form in clusters. Therefore a comprehensive view of star formation requires understanding the initial conditions for cluster formation. The goal of our study is to shed light on the physical properties of infrared dark clouds (IRDCs) and the role they play in the formation of stellar clusters. This article, the first of a series dedicated to the study of IRDCs, describes techniques developed to establish a complete catalogue of Spitzer IRDCs in the Galaxy. We have analysed Spitzer GLIMPSE and MIPSGAL data to identify a complete sample of IRDCs in the region of Galactic longitude and latitude 10{deg}<|l|<65{deg} and |b|<1{deg}. From the 8um observations we have constructed opacity maps and used a newly developed extraction algorithm to identify structures above a column density of N_H2_=1x10^22^cm^-2^. The 24um data are then used to characterize the star formation activity of each extracted cloud. A total of 11303 clouds have been extracted. A comparison with the existing MSX based catalogue of IRDCs shows that 80% of these Spitzer dark clouds were previously unknown. The algorithm also extracts ~20000 to 50000 fragments within these clouds, depending on detection threshold used.A first look at the MIPSGAL data indicates that between 20% and 68% of these IRDCs show 24um point-like association. This new database provides an important resource for future studies aiming to understand the initial conditions of star formation in the Galaxy.
15. Accretion history of massive stars
ID:
ivo://CDS.VizieR/J/MNRAS/496/3482
Title:
Accretion history of massive stars
Short Name:
J/MNRAS/496/3482
Date:
21 Oct 2021
Publisher:
CDS
Description:
The mass growth of protostars is a central element to the determination of fundamental stellar population properties such as the initial mass function. Constraining the accretion history of individual protostars is therefore an important aspect of star formation research. The goal of the study presented here is to determine whether high-mass (proto)stars gain their mass from a compact (<0.1pc) fixed-mass reservoir of gas, often referred to as dense cores, in which they are embedded, or whether the mass growth of high-mass stars is governed by the dynamical evolution of the parsec-scale clump that typically surrounds them. To achieve this goal, we performed a 350micron continuum mapping of 11 infrared dark clouds, along side some of their neighbouring clumps, with the ArTeMiS camera on APEX. By identifying about 200 compact ArTeMiS sources, and matching them with Herschel Hi-GAL 70micron sources, we have been able to produce mass vs. temperature diagrams. We compare the nature (i.e. starless or protostellar) and location of the ArTeMiS sources in these diagrams with modelled evolutionary tracks of both core-fed and clump-fed accretion scenarios. We argue that the latter provide a better agreement with the observed distribution of high-mass star-forming cores. However, a robust and definitive conclusion on the question of the accretion history of high-mass stars requires larger number statistics.
16. A cluster of compact radio sources in W40
ID:
ivo://CDS.VizieR/J/AJ/140/968
Title:
A cluster of compact radio sources in W40
Short Name:
J/AJ/140/968
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present deep 3.6 cm radio continuum observations of the HII region W40 obtained using the Very Large Array (VLA) in its A and B configurations. We detect a total of 20 compact radio sources in a region of 4'x4', with 11 of them concentrated in a band with 30" of extent. We also present JHK photometry of the W40 cluster taken with the QUIRC instrument on the University of Hawaii 2.2m telescope. These data reveal that 15 of the 20 VLA sources have infrared counterparts, and 10 show radio variability with periods less than 20 days. Based on these combined radio and IR data, we propose that eight of the radio sources are candidate ultracompact HII regions, seven are likely to be young stellar objects, and two may be shocked interstellar gas.
17. ACO 370, 2218 and 2390 fluxes at 7 and 15um
ID:
ivo://CDS.VizieR/J/A+A/407/791
Title:
ACO 370, 2218 and 2390 fluxes at 7 and 15um
Short Name:
J/A+A/407/791
Date:
21 Oct 2021
Publisher:
CDS
Description:
ESA's Infrared Space Observatory (ISO) was used to perform a deep survey with ISOCAM through three massive gravitationally lensing clusters of galaxies. The total area surveyed depends on source flux, with nearly seventy square arcminutes covered for the brighter flux levels in maps centred on the three clusters Abell 370, Abell 2218 and Abell 2390. We present maps and photometry at 6.7um (hereafter 7um) and 14.3um (hereafter 15um), showing a total of 145 mid-infrared sources and the associated source counts.
18. A CS(2-1) survey of UC HII regions
ID:
ivo://CDS.VizieR/J/A+AS/115/81
Title:
A CS(2-1) survey of UC HII regions
Short Name:
J/A+AS/115/81
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have made a complete survey of the CS(2-1) emission toward IRAS point sources in the galactic plane. The sources observed were selected according to their far infrared (FIR) colors, which are characteristic of UC HII regions. They have 25{mu}m/12{mu}m flux ratios larger than 3.7 and 60{mu}m/12{mu}m flux ratios larger than 19.3. The survey covered a region from b=-2deg to b=2deg from l=300deg to l=0deg and from l=0deg to l=60deg, and from b=-4deg to b=4deg elsewhere. We detected 843 sources out of 1427 sources observed. The distributions of detected and undetected sources in a FIR color-color diagram show some differences, suggesting that more than one type of object is present in our observed sample.
19. A faint companion around CrA-9
ID:
ivo://CDS.VizieR/J/MNRAS/502/6117
Title:
A faint companion around CrA-9
Short Name:
J/MNRAS/502/6117
Date:
21 Oct 2021
Publisher:
CDS
Description:
Understanding how giant planets form requires observational input from directly imaged protoplanets. We used VLT/NACO and VLT/SPHERE to search for companions in the transition disc of 2MASS J19005804-3645048 (hereafter CrA-9), an accreting M0.75 dwarf with an estimated age of 1-2Myr. We found a faint point source at ~0.7-arcsec separation from CrA-9 (~108au projected separation). Our 3-epoch astrometry rejects a fixed background star with a 5{sigma} significance. The near-IR absolute magnitudes of the object point towards a planetary-mass companion. However, our analysis of the 1.0-3.8um spectrum extracted for the companion suggests it is a young M5.5 dwarf, based on both the 1.13um Na index and comparison with templates of the Montreal Spectral Library. The observed spectrum is best reproduced with high effective temperature (3057^+119^_-36_K) BT-DUSTY and BT-SETTL models, but the corresponding photometric radius required to match the measured flux is only 0.60^+0.01^_-0.04_ Jovian radius. We discuss possible explanations to reconcile our measurements, including an M-dwarf companion obscured by an edge-on circum-secondary disc or the shock-heated part of the photosphere of an accreting protoplanet. Follow-up observations covering a larger wavelength range and/or at finer spectral resolution are required to discriminate these two scenarios.
20. A GBT survey of large Galactic HII regions
ID:
ivo://CDS.VizieR/J/ApJS/234/33
Title:
A GBT survey of large Galactic HII regions
Short Name:
J/ApJS/234/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of our ongoing HII Region Discovery Survey (HRDS), we report the Green Bank Telescope detection of 148 new angularly large Galactic HII regions in radio recombination line (RRL) emission. Our targets are located at a declination of {delta}>-45{deg}, which corresponds to 266{deg}>l>-20{deg} at b=0{deg}. All sources were selected from the Wide-field Infrared Survey Explorer Catalog of Galactic HII Regions, and have infrared angular diameters >=260". The Galactic distribution of these "large" HII regions is similar to that of the previously known sample of Galactic HII regions. The large HII region RRL line width and peak line intensity distributions are skewed toward lower values, compared with that of previous HRDS surveys. We discover seven sources with extremely narrow RRLs <10km/s. If half the line width is due to turbulence, these seven sources have thermal plasma temperatures <1100K. These temperatures are lower than any measured for Galactic HII regions, and the narrow-line components may arise instead from partially ionized zones in the HII region photodissociation regions. We discover G039.515+00.511, one of the most luminous HII regions in the Galaxy. We also detect the RRL emission from three HII regions with diameters >100pc, making them some of the physically largest known HII regions in the Galaxy. This survey completes the HRDS HII region census in the Northern sky, where we have discovered 887 HII regions and more than doubled the size of the previously known census of Galactic HII regions.