- ID:
- ivo://CDS.VizieR/J/ApJ/887/82
- Title:
- Galactic carbon stars infrared spectroscopy
- Short Name:
- J/ApJ/887/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New infrared spectra of 33 Galactic carbon stars from FORCAST on SOFIA reveal strong connections between stellar pulsations and the dust and molecular chemistry in their circumstellar shells. A sharp boundary in overall dust content, which predominantly measures the amount of amorphous carbon, separates the semiregular and Mira variables, with the semiregulars showing little dust in their spectra and the Miras showing more. In semiregulars, the contribution from SiC dust increases rapidly as the overall dust content grows, but in Miras, the SiC dust feature grows weaker as more dust is added. A similar dichotomy is found with the absorption band from CS at ~7.3{mu}m, which is generally limited to semiregular variables. Observationally, these differences make it straightforward to distinguish semiregular and Mira variables spectroscopically without the need for long-term photometric observations or knowledge of their distances. The rapid onset of strong SiC emission in Galactic carbon stars in semiregular variables points to a different dust-condensation process before strong pulsations take over. The break in the production of amorphous carbon between semiregulars and Miras seen in the Galactic sample is also evident in Magellanic carbon stars, linking strong pulsations in carbon stars to the strong mass-loss rates which will end their lives as stars across a wide range of metallicities.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/626/A44
- Title:
- Galactic center CO rot-vib absorption lines
- Short Name:
- J/A+A/626/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the near- to mid-infrared wavelength domain, bright continuum sources in the central parsec of the Galactic center (GC) are subject to foreground absorption. These sources therefore represent ideal probes of the intervening material that is responsible for the absorption along the line of sight. Our aim is to shed light on the location and physics of the absorbing clouds. We try to find out which of the gaseous absorbing materials is intimately associated with the GC and which one is associated with clouds at a much larger distance. We used the capabilities of CRIRES spectrograph located at ESO Very Large Telescope in Chile to obtain absorption spectra of individual lines at a high spectral resolution of R=65000, that is, 5km/s. We observed the 12CO R(0), P(1), P(2), P(3), P(4), P(5), P(6), P(7) and P(9) transition lines, applied standard data reduction, and compared the results with literature data. Results. We present the results of CRIRES observations of 13 infrared sources located in the central parsec of the Galaxy. The data provide direct evidence for a complex structure of the interstellar medium along the line of sight and in the close environment of the central sources. In particular we find four cold foreground clouds at radial velocities vLS R of the order of -145, -85, -60, and -40+\/-15km/s that show absorption in the lower transition lines from R(0) to P(2) and in all the observed spectra.We also find in all sources an absorption in velocity range of 50-60km/s, possibly associated with the so-called 50km/s cloud and suggesting an extension of this cloud in front of the GC. Finally, we detect individual absorption lines that are probably associated with material much closer to the center and with the sources themselves, suggesting the presence of cold gas in the local region.
- ID:
- ivo://CDS.VizieR/J/A+A/493/785
- Title:
- Galactic disk stellar populations from ISOGAL
- Short Name:
- J/A+A/493/785
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify the stellar populations (mostly red giants and young stars) detected in the ISOGAL survey at 7 and 15um towards a field (LN45) in the direction l=-45, b=0.0. The sources detected in the survey of the Galactic plane by the Infrared Space Observatory were characterised based on colour-colour and colour-magnitude diagrams. We combine the ISOGAL catalogue with the data from surveys such as 2MASS and GLIMPSE. Interstellar extinction and distance were estimated using the red clump stars detected by 2MASS in combination with the isochrones for the AGB/RGB branch. Absolute magnitudes were thus derived and the stellar populations identified from their absolute magnitudes and their infrared excess. A standard approach to analysing the ISOGAL disc observations has been established. We identify several hundred RGB/AGB stars and 22 candidate young stellar objects in the direction of this field in an area of 0.16deg^2^. An overdensity of stellar sources is found at distances corresponding to the distance of the Scutum-Crux spiral arm. In addition, we determined mass-loss rates of AGB-stars using dust radiative transfer models from the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/653/1325
- Title:
- Galactic distribution of infrared dark clouds
- Short Name:
- J/ApJ/653/1325
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using ^13^CO(J=1-0) molecular line emission (112GHz) from the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey (BU-FCRAO GRS), we have established kinematic distances to 313 infrared dark clouds (IRDCs) by matching the morphology of the molecular line emission in distinct velocity channels to their mid-infrared extinction.
- ID:
- ivo://CDS.VizieR/J/ApJ/680/349
- Title:
- Galactic distribution of IRDCs
- Short Name:
- J/ApJ/680/349
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CS(2-1) measurements toward a large sample of fourth Galactic quadrant infrared dark clouds (IRDCs) were made with the Australia Telescope National Facility Mopra telescope in order to establish their kinematic distances and Galactic distribution. Due to its large critical density, CS unambiguously separates the dense IRDCs from more diffuse giant molecular clouds. The fourth-quadrant IRDCs show a pronounced peak in their radial galactocentric distribution at R=6kpc. The first-quadrant IRDC distribution (traced by ^13^CO emission) also shows a peak, but at a galactocentric radius of R=5kpc rather than 6kpc. The reliability of the MSX IRDC catalog by Simon and coworkers is estimated by using the CS detection rate of IRDC candidates. The overall reliability is at least 58%, and increases to near 100% for high contrasts, Galactic longitudes within ~30{deg} of the Galactic center, and large mid-IR backgrounds. A significant fraction of our IRDC sample (14%) showed two CS velocity components, which probably represent two distinct IRDCs along the same line of sight.
- ID:
- ivo://CDS.VizieR/J/ApJS/235/41
- Title:
- Galactic EB stars with eccentric orbits based on ETDs
- Short Name:
- J/ApJS/235/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A comprehensive catalog of 623 galactic eclipsing binary (EB) systems with eccentric orbits is presented with more than 2830 times of minima determined from the archived photometric data by various sky-survey projects and new photometric measurements. The systems are divided into two groups according to whether the individual system has a GCVS name or not. All the systems in both groups are further classified into three categories (D, A, and A+III) on the basis of their eclipse timing diagrams: 453 D systems showing just constantly displaced secondary minima, 139 A systems displaying only apsidal motion (AM), and 31 A+III systems exhibiting both AM and light-time effects. AM parameters for 170 systems (A and A+III systems) are consistently calculated and cataloged with basic information for all systems. Some important statistics for the AM parameters are discussed and compared with those derived for the eccentric EB systems in the Large and Small Magellanic Clouds.
- ID:
- ivo://CDS.VizieR/J/ApJ/852/50
- Title:
- Galactic halo with APOGEE. II. Abundances.
- Short Name:
- J/ApJ/852/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation processes that led to the current Galactic stellar halo are still under debate. Previous studies have provided evidence for different stellar populations in terms of elemental abundances and kinematics, pointing to different chemical and star formation histories (SFHs). In the present work, we explore, over a broader range in metallicity (-2.2<[Fe/H]<+0.5), the two stellar populations detected in the first paper of this series from metal-poor stars in DR13 of the Apache Point Observatory Galactic Evolution Experiment (APOGEE). We aim to infer signatures of the initial mass function (IMF) and the SFH from the two {alpha}-to-iron versus iron abundance chemical trends for the most APOGEE-reliable {alpha}-elements (O, Mg, Si, and Ca). Using simple chemical-evolution models, we infer the upper mass limit (Mup) for the IMF and the star formation rate, and its duration for each population. Compared with the low-{alpha} population, we obtain a more intense and longer-lived SFH, and a top-heavier IMF for the high-{alpha} population.
258. Galactic H2O masers
- ID:
- ivo://CDS.VizieR/J/A+AS/101/153
- Title:
- Galactic H2O masers
- Short Name:
- J/A+AS/101/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The association between galactic H2O masers and IRAS sources from the Point Source Catalog (Cat. II/125) is established for 442 sources out of a list of 505 objects, which includes all the galactic H2O masers north of 30{deg}, known up to 1988. Using a multivariate statistical analysis on the four far-IR fluxes of the associated IRAS source, galactic H2O masers are reclassified into two classes: those associated to star forming regions (SFR, 52%) and those associated to late type stars (STAR, 45%). The remaining 3% cannot be included in either class. The present classification is compared with others in the literature. Distances for a large subsample of 1120 masers are derived, using the galactic rotation curve for SFR and literature data for STAR.The parameters of the H2O maser emission (e.g. integrated flux, luminosity, variability), collected in a homogeneous way in the Arcetri H2O atlas (Comoretto et al. 1990A&AS...84..179C), and those of the associated IRAS sources (e.g. flux density, luminosity, colours) are used to investigate, in a statistical way, the properties of the STAR and SFR classes. In particular, we investigate the spatial distribution of masers both in the galactic plane and perpendicular to it. We also compare the H2O and IRAS luminosities, finding a good correlation. Moreover, we find that high luminosity sources show low colour temperatures and vice versa. The spectral profile and variability are then investigated by different means. Finally, the luminosity function for each maser class is derived.
- ID:
- ivo://CDS.VizieR/J/A+A/376/997
- Title:
- Galactic mass-losing AGB stars
- Short Name:
- J/A+A/376/997
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AGB mass-losing sources are easy to identify and to characterize in the near-infrared range (1-5{mu}m). We make use of the near-infrared data acquired by the Japanese space experiment IRTS to study a sample of sources detected in the 2 celestial strips surveyed by the IRTS. Mass-loss rates and distances are estimated for 40 carbon-rich sources and 86 oxygen-rich sources of which 8 are probably of S-type. Although the sample is small, one sees a dependence of the relative contribution of the two kinds of sources to the replenishment of the interstellar medium (ISM) on the galactocentric distance. E.g. from 6 to 8kpc, oxygen-rich sources in our sample contribute 10-12 times as much as carbon rich sources, whereas from 10 to 12kpc, the latters contribute 3-4 times as much as the formers. Therefore, one would expect a gradient in the composition of the ISM between 6 and 12kpc from the Galactic Centre, especially in its dust component. Most of the replenishment (>50%) by AGB stars is due to sources with mass-loss rate larger than 10^-6^M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/73
- Title:
- Galactic MCs associated with HII regions
- Short Name:
- J/ApJ/831/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relations between star formation and properties of molecular clouds (MCs) are studied based on a sample of star-forming regions in the Galactic Plane. Sources were selected by having radio recombination lines to provide identification of associated MCs and dense clumps. Radio continuum emission and mid-infrared emission were used to determine star formation rates (SFRs), while ^13^CO and submillimeter dust continuum emission were used to obtain the masses of molecular and dense gas, respectively. We test whether total molecular gas or dense gas provides the best predictor of SFR. We also test two specific theoretical models, one relying on the molecular mass divided by the free-fall time, the other using the free-fall time divided by the crossing time. Neither is supported by the data. The data are also compared to those from nearby star-forming regions and extragalactic data. The star formation "efficiency," defined as SFR divided by mass, spreads over a large range when the mass refers to molecular gas; the standard deviation of the log of the efficiency decreases by a factor of three when the mass of relatively dense molecular gas is used rather than the mass of all of the molecular gas.
