- ID:
- ivo://CDS.VizieR/J/ApJ/763/32
- Title:
- Galactic halo RRab stars from CSS
- Short Name:
- J/ApJ/763/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present analysis of 12227 type-ab RR Lyraes (RRLs; ~9400 are newly discovered) found among the 200 million public light curves in Catalina Surveys Data Release 1. These stars span the largest volume of the Milky Way ever surveyed with RRLs, covering ~20000deg^2^ of the sky (0{deg}<{alpha}<360{deg}, -22{deg}<{delta}<65{deg}) to heliocentric distances of up to 60kpc. Each of the RRLs is observed between 60 and 419 times over a six-year period. Using period finding and Fourier fitting techniques we determine periods and apparent magnitudes for each source. We find that the periods are generally accurate to {sigma}=0.002% in comparison to 2842 previously known RRLs and 100 RRLs observed in overlapping survey fields. We photometrically calibrate the light curves using 445 Landolt standard stars and show that the resulting magnitudes are accurate to ~0.05mag using Sloan Digital Sky Survey (SDSS) data for ~1000 blue horizontal branch stars and 7788 RRLs. By combining Catalina photometry with SDSS spectroscopy, we analyze the radial velocity and metallicity distributions for >1500 of the RRLs. Using the accurate distances derived for the RRLs, we show the paths of the Sagittarius tidal streams crossing the sky at heliocentric distances from 20 to 60kpc. By selecting samples of Galactic halo RRLs, we compare their velocity, metallicity, and distance with predictions from a recent detailed N-body model of the Sagittarius system. We find that there are some significant differences between the distances and structures predicted and our observations.
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- 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.
- ID:
- ivo://CDS.VizieR/J/ApJS/105/369
- Title:
- Galactic H I column densities
- Short Name:
- J/ApJS/105/369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined accurate values of the Galactic neutral hydrogen column density, N_H_, toward 220 quasars and active galactic nuclei from 21cm H I measurements made on the 130 Foot Telescope (42.7m). Accurate values of N_H_ have now been obtained for the whole PG bright quasar sample and most quasars that have been observed by ROSAT and the Hubble Space Telescope through mid-1993. The spectra were corrected for stray 21cm radiation yielding values of N_H_ with a typical uncertainty of 1x10^19cm^-2 for high Galactic latitude directions. The H I column densities will be useful for correcting for interstellar opacity at UV and soft X-ray wavelengths, and for estimating the reddening and extinction toward these objects.
- ID:
- ivo://CDS.VizieR/J/MNRAS/447/2307
- Title:
- Galactic HII region IRAS 16148-5011 content
- Short Name:
- J/MNRAS/447/2307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An investigation of the IRAS 16148-5011 region - a cluster at a distance of 3.6kpc - is presented here, carried out using multiwavelength data in near-infrared (NIR) from the 1.4m Infrared Survey Facility telescope, mid-infrared (MIR) from the archival Spitzer GLIMPSE (Galactic Legacy Infrared Midplane Survey Extraordinaire) survey, far-infrared (FIR) from the Herschel archive, and low-frequency radio continuum observations at 1280 and 843MHz from the Giant Metrewave Radio Telescope and Molonglo Survey archive, respectively. A combination of NIR and MIR data is used to identify 7 Class I and 133 Class II sources in the region. Spectral energy distribution (SED) analysis of selected sources reveals a 9.6M_{sun}_ high-mass source embedded in nebulosity. However, Lyman continuum luminosity calculation using radio emission - which shows a compact HII region - indicates the spectral type of the ionizing source to be earlier than B0-O9.5. Free-free emission SED modelling yields the electron density as 138cm^-3^, and thus the mass of the ionized hydrogen as ~16.4M_{sun}_. Thermal dust emission modelling, using the FIR data from Herschel and performing modified blackbody fits, helped us construct the temperature and column density maps of the region, which show peak values of 30K and 3.3x10^22^cm^-2^, respectively. The column density maps reveal an A_V_>20mag extinction associated with the nebular emission, and weak filamentary structures connecting dense clumps. The clump associated with this IRAS object is found to have dimensions of ~1.1pcx0.8pc, and a mass of 10^23^M_{sun}_.
5055. Galactic HII regions
- ID:
- ivo://CDS.VizieR/J/A+A/397/213
- Title:
- Galactic HII regions
- Short Name:
- J/A+A/397/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Master Catalog collects the information from 24 previously published lists and catalogs for 1442 Galactic HII regions. For each object, the Master Catalog quotes the original fluxes and diameters as well as the available information on radio line velocities, line widths and line temperatures and the errors on these quantities. The Synthetic Catalog at 2.7GHz summarizes the basic information of flux density and angular diameter for each of these objects. The catalog can be used for detailed studies of Galactic HII regions and, by extrapolation, for investigations of HII regions up to millimetric wavelengths.
- ID:
- ivo://CDS.VizieR/J/AJ/150/147
- Title:
- Galactic HII regions. I. Stellar distances
- Short Name:
- J/AJ/150/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalog of spectrophotometric distances and line of sight systemic velocities to 103 HII regions between 90{deg}{<=}l<=195{deg} (longitude quadrants II and part of III). Two new velocities for each region are independently measured using 1 arcmin resolution 21cm HI and 2.6mm^12^CO line maps (from the Canadian Galactic Plane Survey and Five College Radio Astronomy Observatory Outer Galaxy Surveys) that show where gaseous shells are observed around the periphery of the ionized gas. Known and neighboring O- and B-type stars with published UBV photometry and MK classifications are overlaid onto 21cm continuum maps, and those stars observed within the boundary of the HII emission (and whose distance is not more than three times the standard deviation of the others) are used to calculate new mean stellar distances to each of the 103 nebulae. Using this approach of excluding distance outliers from the mean distance to a group of many stars in each HII region lessens the impact of anomalous reddening for certain individuals. The standard deviation of individual stellar distances in a cluster is typically 20% per stellar distance, and the error in the mean distance to the cluster is typically +/-10%. Final mean distances of nine common objects with very long baseline interferometry parallax distances show a 1:1 correspondence. Further, comparison with previous catalogs of HII regions in these quadrants shows a 50% reduction in scatter for the distance to Perseus spiral arm objects in the same region, and a reduction by ~1/2^0.5^ in scatter around a common angular velocity relative to the Sun {Omega}-{Omega}_0_(km/s/kpc). The purpose of the catalog is to provide a foundation for more detailed large-scale Galactic spiral structure and dynamics (rotation curve, density wave streaming) studies in the 2nd and 3rd quadrants, which from the Sun's location is the most favorably viewed section of the Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/738/27
- Title:
- Galactic HII regions RRL and continuum data
- Short Name:
- J/ApJ/738/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distribution of metals in the Galaxy provides important information about galaxy formation and evolution. HII regions are the most luminous objects in the Milky Way at mid-infrared to radio wavelengths and can be seen across the entire Galactic disk. We used the National Radio Astronomy Observatory (NRAO) Green Bank Telescope to measure radio recombination line (RRL) and continuum emission in 81 Galactic HII regions. We calculated LTE electron temperatures using these data. In thermal equilibrium metal abundances are expected to set the nebular electron temperature with high abundances producing low temperatures. Our HII region distribution covers a large range of Galactocentric radius (5-22kpc) and samples the Galactic azimuth range 330-60{deg}. Using our highest quality data (72 objects) we derived an O/H Galactocentric radial gradient of -0.0383+/-0.0074dex/kpc. Combining these data with a similar survey made with the NRAO 140 Foot telescope we get a radial gradient of -0.0446+/-0.0049dex/kpc for this larger sample of 133 nebulae.
- ID:
- ivo://CDS.VizieR/J/PASP/130/K4301
- Title:
- 101 Galactic HII regions spectroscopy
- Short Name:
- J/PASP/130/K4301
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We spectroscopically identify 101 Galactic HII regions using spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey, cross-matched with an HII region catalog derived from the all-sky Wide-Field Infrared Survey Explorer (WISE) data. Among all HII regions in our sample, 47 sources are newly confirmed. Spatially, most of our identified HII regions are located in the anti-center area of the Galaxy. For each of the HII regions, we accurately extract and measure the nebular emission lines of the spectra, and estimate the oxygen abundances using the strong-line method. We focus on the abundance distribution of HII regions in the Galactic anti-center area. Accordingly, we derive the oxygen abundance gradient with a slope of -0.036+/-0.004dex/kpc, covering a range of R_G_ from 8.1 to 19.3kpc. In particular, we also fit the outer disk objects with a slope of -0.039+/-0.012dex/kpc, which indicates that there is no flattening of the radial oxygen gradient in the outer Galactic disk.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A43
- Title:
- Galactic HI supershells kinetic energies
- Short Name:
- J/A+A/624/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We estimate the Galactic supershell (GS) masses and energies. We developed and used an automatic algorithm. The study was carried out making use of the Leiden-Argentine-Bonn (LAB) HI survey in the outer part of the Galaxy. The algorithm was applied only to a set of GSs from the catalogue of Suad et al. (2014, Cat. J/A+A/564/A116), those showing HI-emission surrounding its central cavity in at least three quarters (or 270 degrees) of its angular extent. A total of 490 GSs fulfilled this criterion. Among them, 308 are completely surrounded by walls of HI-emission (Group A) and in the remaining 182 the central HI minimum is surrounded by ridges of HI emission in at least 270{deg} of its angular extent (Group B).
5060. 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.