- ID:
- ivo://CDS.VizieR/J/A+A/335/467
- Title:
- High galactic latitude RASS X-ray sources
- Short Name:
- J/A+A/335/467
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a summary of spectroscopic identifications for a complete sample of bright soft high galactic latitude X-ray sources drawn from the ROSAT All-Sky Survey which have PSPC count-rates CR>0.5cts/s and hardness ratios HR1<0. Of a total of 397 sources, 270 had catalogued counterparts although most of these were not previously known as X-ray sources; of the remaining 127 sources neither X-ray nor optical properties were previously known. Of the whole sample of very soft X-ray sources 155 were also discovered by the Wide-Field-Camera on board ROSAT. We present spectroscopic identifications of 108 sources and other identifications for further 18 sources; 1 source remains unidentified so far. In practically all cases a unique optical counterpart exists facilitating identification. The largest source classes are AGN, magnetic cataclysmic variables, and hot white dwarfs.
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- ID:
- ivo://CDS.VizieR/J/A+A/347/47
- Title:
- High galactic latitude RASS X-ray sources. II.
- Short Name:
- J/A+A/347/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a summary of spectroscopic identifications of bright soft high galactic latitude X-ray sources from the ROSAT All-Sky Survey with total PSPC count rates 0.11<CR<0.5cts/s and hardness ratios HR1<0. This study supplements the identification program of a complete sample of sources with CR>=0.5cts/s presented previously. Spectroscopic identifications are presented for 70 of 77 sources, 5 sources are identified by other means, and subsidiary information is given for 2 as yet unidentified sources. In practically all cases, a unique optical counterpart exists. As for the brighter fraction of the sample, the largest source classes are Seyfert 1 galaxies, magnetic cataclysmic variables, and hot white dwarfs. In the Galactic Pole caps at |b|>400, Seyfert galaxies dominate, whereas at intermediate latitudes galactic objects as magnetic cataclysmic variables and white dwarfs become relatively more frequent.
- ID:
- ivo://CDS.VizieR/J/ApJ/693/8
- Title:
- High-redshift QSOs in the COSMOS survey
- Short Name:
- J/ApJ/693/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new measurement of the space density of high-redshift (z~3.0-4.5), X-ray-selected quasi-stellar objects (QSOs) obtained by exploiting the deep and uniform multiwavelength coverage of the COSMOS survey. We have assembled a large (40 objects), homogeneous sample of z>3 QSOs with X-ray flux F0.5-2keV>10^-15^erg/cm^2^/s, and available spectroscopic (22) or photometric (18) redshifts. We discuss their optical (color-color diagrams) and X-ray properties, their number counts and space densities and compare our findings with previous works and model predictions.
- ID:
- ivo://CDS.VizieR/J/ApJS/209/12
- Title:
- High-velocity clouds from GASS. I.
- Short Name:
- J/ApJS/209/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of high-velocity clouds (HVCs) from the Galactic All Sky Survey (GASS) of southern sky neutral hydrogen, which has 57mK sensitivity and 1 km/s velocity resolution and was obtained with the Parkes Telescope. Our catalog has been derived from the stray-radiation-corrected second release of GASS. We describe the data and our method of identifying HVCs and analyze the overall properties of the GASS population. We catalog a total of 1693 HVCs at declinations <0{deg}, including 1111 positive velocity HVCs and 582 negative velocity HVCs. Our catalog also includes 295 anomalous velocity clouds (AVCs). The cloud line-widths of our HVC population have a median FWHM of ~19 km/s, which is lower than that found in previous surveys. The completeness of our catalog is above 95% based on comparison with the HIPASS catalog of HVCs upon which we improve by an order of magnitude in spectral resolution. We find 758 new HVCs and AVCs with no HIPASS counterpart. The GASS catalog will shed unprecedented light on the distribution and kinematic structure of southern sky HVCs, as well as delve further into the cloud populations that make up the anomalous velocity gas of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/70
- Title:
- Hot subdwarf stars from Gaia DR2 and LAMOST DR5
- Short Name:
- J/ApJ/868/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We selected 4593 hot subdwarf candidates from the Gaia DR2 Hertzsprung-Russell (HR) diagram. By combining the sample with Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) DR5, we identified 294 hot subdwarf stars, including 169 sdB, 63 sdOB, 31 He-sdOB, 22 sdO, 7 He-sdO, and 2 He-sdB stars. The atmospheric parameters (e.g., Teff, logg, log(nHe/nH)) are obtained by fitting the hydrogen (H) and helium (He) line profiles with synthetic spectra. Two distinct He sequences of hot subdwarf stars are clearly presented in the Teff-logg diagram. We found that the He-rich sequence consists of the bulk of sdB and sdOB stars, as well as all of the He-sdB, He-sdO, and He-sdOB stars in our samples, while all the stars in the He-weak sequence belong to the sdO spectral type, combined with a few sdB and sdOB stars. We demonstrated that the combination of Gaia DR2 and LAMOST DR5 allows one to uncover a huge number of new hot subdwarf stars in our Galaxy.
- ID:
- ivo://CDS.VizieR/J/AJ/135/1350
- Title:
- Hot variable stars in NGC 330
- Short Name:
- J/AJ/135/1350
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a sample of 150 hot stars in NGC 330, a SMC cluster containing a high fraction of Be stars, we searched for photometric variables using OGLE II data. At least one third of all stars are variable, with 38 being periodic. We found 27 pulsators ({lambda} Eri variables), six eclipsing systems, two bursting sources, and several stars with unusual photometric behavior. Pulsations are present in ~30% of known Be stars, and they are long lived, lasting more than a decade. The strongest pulsators are associated with stars evolved from the main sequence.
- ID:
- ivo://CDS.VizieR/J/AJ/136/2136
- Title:
- HST/ACS Atlas of Great Orion Nebula proplyds
- Short Name:
- J/AJ/136/2136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the atlas of protoplanetary disks in the Orion Nebula based on the Wide Field Channel of the Advanced Camera for Surveys (ACS/WFC) images obtained for the Hubble Space Telescope (HST) Treasury Program on the Orion Nebula Cluster. The observations have been carried out in five photometric filters nearly equivalent to the standard B, V, H{alpha}, I, and z passbands. Our master catalog lists 178 externally ionized protoplanetary disks (proplyds), 28 disks seen only in absorption against the bright nebular background (silhouette disks), eight disks seen only as dark lanes at the midplane of extended polar emission (bipolar nebulae or reflection nebulae), and five sources showing jet emission with no evidence of either external ionized gas emission or dark silhouette disks.
- ID:
- ivo://CDS.VizieR/J/AJ/142/183
- Title:
- HST photometry of globulars in M81 (NGC 3031)
- Short Name:
- J/AJ/142/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform aperture photometry and profile fitting on 419 globular cluster (GC) candidates with m_V_<=23mag identified in Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) BVI imaging, and estimate the effective radii of the clusters. We identify 85 previously known spectroscopically confirmed clusters, and newly identify 136 objects as good cluster candidates within the 3{sigma} color and size ranges defined by the spectroscopically confirmed clusters, yielding a total of 221 probable GCs. The luminosity function peak for the 221 probable GCs with estimated total dereddening applied is V~(20.26+/-0.13)mag, corresponding to a distance of ~3.7+/-0.3Mpc. The blue and red GC candidates, and the metal-rich and metal-poor spectroscopically confirmed clusters, respectively, are similar in half-light radius. Red confirmed clusters are about 6% larger in median half-light radius than blue confirmed clusters, and red and blue good GC candidates are nearly identical in half-light radius. The total population of confirmed and "good" candidates shows an increase in half-light radius as a function of galactocentric distance.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/146
- Title:
- HST/WFC3 observations in HUDF and GOODS-S
- Short Name:
- J/ApJ/743/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the high angular resolution in the near-infrared of the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope to determine YHVz color-color-selection criteria to identify and characterize 1.5<z<3.5 galaxies in the Hubble Ultra Deep Field 2009 (HUDF09) and Early Release Science (GOODS-South) fields. The WFC3 NIR images reveal galaxies at these redshifts that were undetected in the rest-frame UV HUDF/GOODS images, as well as true centers and regular disks in galaxies classified as highly irregular in rest-frame UV light. Across the 1.5<z<2.15 redshift range, regular disks are unveiled in the WFC3 images of ~25% of both intermediate and high mass galaxies, i.e., above 10^10^M_{sun}_. Meanwhile, galaxies maintaining diffuse and/or irregular morphologies in the rest-frame optical light - i.e., not yet dynamically settled - at these epochs are almost entirely restricted to masses below 10^11^M_{sun}_. In contrast at 2.25<z<3.5 these diffuse and/or irregular structures overwhelmingly dominate the morphological mix in both the intermediate and high mass regimes, while no regular disks, and only a small fraction (~25%) of smooth spheroids, are evident above 10^11^M_{sun}_. Strikingly, by 1.5<z<2.25 roughly two out of every three galaxies at the highest masses are spheroids. In our small sample, the fraction of star-forming galaxies at these mass scales decreases concurrently from ~60% to ~5%. If confirmed, this indicates that z~2 is the epoch of both the morphological transformation and quenching of star formation which assemble the first substantial population of massive ellipticals.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/55
- Title:
- HST/WFC3 SNR discoveries in M83 (NGC5236)
- Short Name:
- J/ApJ/788/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an optical/NIR imaging survey of the face-on spiral galaxy M83, using data from the Hubble Space Telescope Wide Field Camera 3 (WFC3). Seven fields are used to cover a large fraction of the inner disk, with observations in nine broadband and narrowband filters. In conjunction with a deep Chandra survey and other new radio and optical ground-based work, these data enable a broad range of science projects to be pursued. We provide an overview of the WFC3 data and processing and then delve into one topic, the population of young supernova remnants (SNRs). We used a search method targeted toward soft X-ray sources to identify 26 new SNRs. Many compact emission nebulae detected in [FeII]1.644{mu}m align with known remnants and this diagnostic has also been used to identify many new remnants, some of which are hard to find with optical images. We include 37 previously identified SNRs that the data reveal to be <0.5" in angular size and thus are difficult to characterize from ground-based data. The emission line ratios seen in most of these objects are consistent with shocks in dense interstellar material rather than showing evidence of ejecta. We suggest that the overall high elemental abundances in combination with high interstellar medium pressures in M83 are responsible for this result.
