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Start Over Subject infrared astronomy Content Level Research
311. Galactic halo with APOGEE. II. Abundances.
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.
312. 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.
313. Galactic mass-losing AGB stars
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.
314. Galactic MCs associated with HII regions
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.
315. Galactic midplane Spitzer red sources
ID:
ivo://CDS.VizieR/J/AJ/136/2413
Title:
Galactic midplane Spitzer red sources
Short Name:
J/AJ/136/2413
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a highly reliable flux-limited census of 18949 point sources in the Galactic midplane that have intrinsically red mid-infrared colors. These sources were selected from the Spitzer Space Telescope Galactic Legacy Infrared Midplane Survey Extraordinaire (GLIMPSE) I and II surveys of 274{deg}^2^ of the Galactic midplane, and consist mostly of high- and intermediate-mass young stellar objects (YSOs) and asymptotic giant branch (AGB) stars. The selection criteria were carefully chosen to minimize the effects of position-dependent sensitivity, saturation, and confusion. The distribution of sources on the sky and their location in the Infrared Array Camera and the Multiband Image Photometer for Spitzer 24um color-magnitude and color-color space are presented. Using this large sample, we find that YSOs and AGB stars can be mostly separated by simple color-magnitude selection criteria into approximately 50%-70% of YSOs and 30%-50% of AGB stars. Planetary nebulae and background galaxies together represent at most 2%-3% of all the red sources. 1004 red sources in the GLIMPSE II region, mostly AGB stars with high mass-loss rates, show significant (>=0.3mag) variability at 4.5 and/or 8.0um. With over 11,000 likely YSOs and over 7000 likely AGB stars, this is to date the largest uniform census of AGB stars and high- and intermediate-mass YSOs in the Milky Way Galaxy.
316. Galactic Plane Infrared Polarization Survey, DR4
ID:
ivo://CDS.VizieR/J/ApJS/249/23
Title:
Galactic Plane Infrared Polarization Survey, DR4
Short Name:
J/ApJS/249/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Galactic Plane Infrared Polarization Survey (GPIPS) seeks to characterize the magnetic field in the dusty Galactic disk using near-infrared stellar polarimetry. All GPIPS observations were completed using the 1.83m Perkins telescope and Mimir instrument. GPIPS observations surveyed 76 deg^2^ of the northern Galactic plane, from Galactic longitudes 18{deg}-56{deg} and latitudes -1{deg} to +1{deg}, in the H band (1.6 {mu}m). Surveyed stars span 7th-16th mag, resulting in nearly 10 million stars with measured linear polarizations. Of these stars, ones with m_H_<12.5mag and polarization percentage uncertainties under 2% were judged to be high quality and number over one million. GPIPS data reveal plane-of-sky magnetic field orientations for numerous interstellar clouds for A_V_ values to ~30mag. The average sky separation of stars with m_H_<12.5mag is about 30'', or about 60 per Planck polarization resolution element. Matching to Gaia DR2 showed the brightest GPIPS stars are red giants with distances in the 0.6-7.5kpc range. Polarization orientations are mostly parallel to the Galactic disk, with some zones showing significant orientation departures. Changes in orientations are stronger as a function of Galactic longitude than of latitude. Considered at 10' angular scales, directions that show the greatest polarization fractions and narrowest polarization position angle distributions are confined to about 10 large, coherent structures that are not correlated with star-forming clouds. The GPIPS polarimetric and photometric data products (Data Release 4 catalogs and images) are publicly available for over 13 million stars.
317. Galaxies and QSOs FIR size and surface brightness
ID:
ivo://CDS.VizieR/J/A+A/591/A136
Title:
Galaxies and QSOs FIR size and surface brightness
Short Name:
J/A+A/591/A136
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use Herschel 70 to 160{mu}m images to study the size of the far-infrared emitting region in about 400 local galaxies and quasar (QSO) hosts. The sample includes normal "main-sequence" star-forming galaxies, as well as infrared luminous galaxies and Palomar-Green QSOs, with different levels and structures of star formation. Assuming Gaussian spatial distribution of the far-infrared (FIR) emission, the excellent stability of the Herschel point spread function (PSF) enables us to measure sizes well below the PSF width, by subtracting widths in quadrature. We derive scalings of FIR size and surface brightness of local galaxies with FIR luminosity, with distance from the star-forming main-sequence, and with FIR color. Luminosities L_FIR_~10^11^L_{sun}_ can be reached with a variety of structures spanning 2dex in size. Ultraluminous L_FIR_~10^12^L_{sun}_ galaxies far above the main-sequence inevitably have small R_e,70_~0.5kpc FIR emitting regions with large surface brightness, and can be close to optically thick in the FIR on average over these regions. Compared to these local relations, first ALMA sizes for the dust emission regions in high redshift galaxies, measured at somewhat longer rest wavelengths, suggest larger sizes at the same IR luminosity. We report a remarkably tight relation with 0.15dex scatter between FIR surface brightness and the ratio of [CII] 158{mu}m emission and FIR emission - the so-called [CII]-deficit is more tightly linked to surface brightness than to FIR luminosity or FIR color. Among 33 z<=0.1 PG QSOs with typical L_FIR_/L_Bol,AGN_~0.1, 19 have a measured 70{mu}m half light radius, with median R_e,70_=1.1kpc. This is consistent with the FIR size for galaxies with similar L_FIR_ but lacking a QSO, in accordance with a scenario where the rest FIR emission of these types of QSOs is, in most cases, due to host star formation.
318. Galaxies in Southern Bright Star Fields I.
ID:
ivo://CDS.VizieR/J/A+A/406/593
Title:
Galaxies in Southern Bright Star Fields I.
Short Name:
J/A+A/406/593
Date:
21 Oct 2021
Publisher:
CDS
Description:
As a prerequisite for cosmological studies using adaptive optics techniques, we have begun to identify and characterize faint sources in the vicinity of bright stars at high Galactic latitudes. The initial phase of this work has been a program of K_s_ imaging conducted with SOFI at the ESO NTT. From observations of 42 southern fields evenly divided between the spring and autumn skies, we have identified 391 additional stars and 1589 galaxies lying at separations <60" from candidate guide stars in the magnitude range 9.0<R<12.4. When analyzed as a "discrete deep field" with 131-arcmin^2^ area, our dataset gives galaxy number counts that agree with those derived previously over the range 16<K_s_<20.5. This consistency indicates that in the aggregate, our fields should be suitable for future statistical studies. We provide our source catalogue as a resource for users of large telescopes in the southern hemisphere.
319. Galaxies in the zone of avoidance
ID:
ivo://CDS.VizieR/J/ApJ/449/527
Title:
Galaxies in the zone of avoidance
Short Name:
J/ApJ/449/527
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have selected a sample of 876 galaxy candidates from the IRAS Point Source Catalog in the region of 2h<RA<10h and 0deg<DE<36deg, which crosses the Galactic anticenter part of the Zone of Avoidance (ZOA) and includes most of the highly obscured Orion-Taurus complex region. We have identified galaxies among the candidate sources by attempting to detect the 21cm H I line of those sources which were not known to be galaxies at the beginning of the survey. In this manner, we constructed a galaxy sample which is largely free from Galactic reddening. Of the 272 observed candidates, 89 were detected in the H I line up to a heliocentric velocity of v_h_~16,000km/s. The resulting galaxy sample of 717 galaxies is fairly complete (within about 10%) and uniform (within about 4%) in the part of the survey area 10deg away from the Galactic plane and for velocities up to at least 9000km/s. This provides, for the first time, a largely unbiased view on the large-scale structures in much of the survey area. Our main results are the following: (1) Several large voids are identified. In particular, a void between RA~3h and 4h, up to v_h_~6000km/s, separates the Pisces-Perseus supercluster at RA<3h from structures at RA>4h; and a "nearby void" occupies most of our survey area and reaches out to a redshift of nearly 3000km/s. (2) We found no nearby galaxy concentration that could significantly contribute to the "Local Velocity Anomaly" (LVA), but a general excess of galaxies around v_h_~5000km/s in the survey area. (3) The contrast between the "Great Wall" at v_h_~8500km/s and the void in front of it appears to gradually diffuse out after it enters the Zone of Avoidance from the northern Galactic hemisphere. (4) Our data combined with other galaxy surveys in or near the Galactic anticenter part of the ZOA suggest that the main ridge of the Pisces-Perseus supercluster does also not extend to Abell 569, a cluster in the northern Galactic hemisphere, and that the simple gravitational model consisting of the Local Void of Tully & Fisher, our nearby void, and Puppis and Fornax-Eridanus clusters would predict a LVA whose direction is probably too far away from that derived from observations.
320. Galaxies redshifts, 210<l<360, |b|<15
ID:
ivo://CDS.VizieR/J/ApJS/107/521
Title:
Galaxies redshifts, 210<l<360, |b|<15
Short Name:
J/ApJS/107/521
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have carried out a redshift survey of an IRAS flux-limited (f_60_>0.6) galaxy sample behind the southern Milky Way, 210{deg}<l<360{deg} at |b|<15{deg}. The survey includes redshifts for 951 galaxies, ~500 of which are new. Of these 951 galaxies, 462 are in the zone 5{deg}<b<15{deg} and 353 are in the zone -15{deg}<b<-5{deg}. Though the innermost region of the Milky Way (|b|=5{deg}) remains opaque except in the longitude near 240, the detected galaxies show a high degree of completeness (~70%) in the zones 5{deg}<b<15{deg} and -15{deg}<b<-5{deg}. The cone diagrams exhibiting the detailed distribution of IRAS galaxies in the region 210{deg}<l<360{deg}, |b|<15{deg} shows two clusters in the Puppis region (l=240{deg}, b=-7{deg}, v=2400km/s; l=245{deg}, b=-5{deg}, v=7500km/s), the A3627 cluster (l=325{deg}, b=-7{deg}; v=4500km/s), the S4 cluster (l=280{deg}, b=7{deg}; v=5500km/s), and a possible void at l=245{deg}, v=3000km/s. The region 270{deg}<l<350{deg} is dominated by overdensity of galaxies representing the extension of the Hydra-Centaurus complex in the positive latitudes and the Pavo-Indus complex in the negative latitudes. A velocity histogram of galaxies in the GA region 290{deg}<l<350{deg}, |b|<15{deg}. reveals a substantial overdensity of galaxies in the velocity range 2400-5000km/s. The centroid of this overdensity is located at 4000km/s. The broad increased density of galaxies seen in our data corresponds with the distant concentration seen at 4500km/s in the supergalactic plane survey that covers the same longitude range like ours in l, but a larger range in latitude b (-30{deg} to -10{deg} and +10{deg} to +45{deg}). This lends support to the idea that the overdensity extends all the way from the Centaurus-Hydra complex (l=302{deg}, b=+22{deg}) in the north to the major concentration of the Pavo-Indus supercluster (l=332{deg}, b=-24{deg}) in the south, through the Milky Way. We conclude that the peak of the overdensity responsible for the peculiar velocity field in the local region is possibly situated in the Milky Way itself.