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16361. Ultraluminous X-Ray Sources in External Galaxies Catalog
ID:
ivo://nasa.heasarc/ulxrbcat
Title:
Ultraluminous X-Ray Sources in External Galaxies Catalog
Short Name:
ULXRB
Date:
28 Mar 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table is a catalog of ultraluminous X-ray sources (ULXs) in external galaxies, where ULXs have been defined as compact, off-nuclear X-ray sources with X-ray luminosities in the range of 10<sup>39</sup> - 10<sup>41</sup> erg/s. The aim of this catalog is to provide easy access to the properties of ULXs, their possible counterparts at other wavelengths (optical, IR, and radio), and the properties of their host galaxies. The catalog contains 229 ULXs found in 85 galaxies which had been reported in the astronomy literature as of April 2004. Most ULXs are stellar-mass-black hole X-ray binaries, but it cannot be excluded that some ULXs might be intermediate-mass black holes. A small fraction of the candidate ULXs might be background Active Galactic Nuclei (AGN) or Supernova Remnants (SNRs). ULXs with luminosity above 10<sup>40</sup> erg/s are found in both starburst galaxies and in the halos of early-type galaxies. Some notes on individual galaxies and/or ULXs in this catalog can be found in the file <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/429/1125/notes.dat">https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/429/1125/notes.dat</a> which is available at the CDS. This table was created by the HEASARC in January 2005, based on CDS tables J/A+A/429/1125/table1a.dat and table1b.dat. It was updated in September 2012 to correct an error in the declination signs of the NGC 253 objects. This is a service provided by NASA HEASARC .
16362. Ultraluminous X-ray sources in nearby galaxies
ID:
ivo://CDS.VizieR/J/ApJS/157/59
Title:
Ultraluminous X-ray sources in nearby galaxies
Short Name:
J/ApJS/157/59
Date:
21 Oct 2021
Publisher:
CDS
Description:
X-ray observations have revealed in other galaxies a class of extranuclear X-ray point sources with X-ray luminosities of 10^39^-10^41^ergs/s, exceeding the Eddington luminosity for stellar mass X-ray binaries. These ultraluminous X-ray sources (ULXs) may be powered by intermediate-mass black holes of a few thousand M_Sun_ or stellar mass black holes with special radiation processes. In this paper, we present a survey of ULXs in 313 nearby galaxies with D_25_>1 within 40Mpc with 467 ROSAT High Resolution Imager (HRI) archival observations. The HRI observations are reduced with uniform procedures, refined by simulations that help define the point source detection algorithm employed in this survey. A sample of 562 extragalactic X-ray point sources with L_X_=10^38^-10^43^ergs/s is extracted from 173 survey galaxies, including 106 ULX candidates within the D_25_ isophotes of 63 galaxies and 110 ULX candidates between 1D_25_ and 2D_25_ of 64 galaxies, from which a clean sample of 109 ULXs is constructed to minimize the contamination from foreground or background objects.
16363. Ultraluminous X-Ray Sources in Nearby Galaxies Catalog
ID:
ivo://nasa.heasarc/ulxngcat
Title:
Ultraluminous X-Ray Sources in Nearby Galaxies Catalog
Short Name:
ULXNGCAT
Date:
28 Mar 2025
Publisher:
NASA/GSFC HEASARC
Description:
One hundred and seven ultraluminous X-ray sources (ULXs) with 0.3-10.0 keV luminosities in excess of 10<sup>39</sup> erg s<sup>-1</sup> are identified in a complete sample of 127 nearby galaxies. The sample includes all galaxies within 14.5 Mpc above the completeness limits of both the Uppsala Galaxy Catalogue and the Infrared Astronomical Satellite survey. The galaxy sample spans all Hubble types, a four-decade range in mass, 7.5 < log (M/M<sub>sun</sub>) < 11.4, and in star formation rate, 0.0002 < SFR(M<sub>sun</sub> yr<sup>-1</sup>) <= 3.6. ULXs are detected in this sample at rates of one per 3.2 x 10<sup>10</sup> M<sub>sun</sub>, one per ~0.5 M<sub>sun</sub> yr<sup>-1</sup> star formation rate, and one per 57 Mpc<sup>3</sup> corresponding to a luminosity density of ~2 x 10<sup>37</sup> erg s<sup>-1</sup> Mpc<sup>-3</sup>. At these rates, the authors estimate as many as 19 additional ULXs remain undetected in fainter dwarf galaxies within the survey volume. An estimated 14 objects, or 13%, of the 107 ULX candidates are expected to be background sources. The differential ULX luminosity function shows a power-law slope alpha ~ -0.8 to -2.0 with an exponential cutoff at ~20 x 10<sup>39</sup> erg s<sup>-1</sup> with precise values depending on the model and on whether the ULX luminosities are estimated from their observed numbers of counts or, for a subset of candidates, from their spectral shapes. Extrapolating the observed luminosity function predicts at most one very luminous ULX, L<sub>X</sub> ~ 10<sup>41</sup> erg s<sup>-1</sup>, within a distance as small as 100 Mpc. The luminosity distribution of ULXs within the local universe cannot account for the recent claims of luminosities in excess of 2 x 10<sup>41</sup> erg s<sup>-1</sup>, requiring a new population class to explain these extreme objects. This table was created by the HEASARC in November 2011 based on an electronic version of Table 1 from the reference paper that was obtained from the ApJ web site. This is a service provided by NASA HEASARC .
16364. Ultra-metal-poor stars LTE and NLTE abundances
ID:
ivo://CDS.VizieR/J/ApJ/847/142
Title:
Ultra-metal-poor stars LTE and NLTE abundances
Short Name:
J/ApJ/847/142
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new ultra-metal-poor stars parameters with [Fe/H] < -4.0 based on line-by-line non-local thermodynamic equilibrium (NLTE) abundances using an up-to-date iron model atom with a new recipe for non-elastic hydrogen collision rates. We study the departures from LTE in their atmospheric parameters and show that they can grow up to ~1.00dex in [Fe/H], ~150K in Teff and ~0.5dex in logg toward the lowest metallicities. Accurate NLTE atmospheric stellar parameters, in particular [Fe/H] being significantly higher, are the first step to eventually providing full NLTE abundance patterns that can be compared with Population III supernova nucleosynthesis yields to derive properties of the first stars. Overall, this maximizes the potential of these likely second-generation stars to investigate the early universe and how the chemical elements were formed.
16365. Ultra steep spectrum radio sources
ID:
ivo://CDS.VizieR/J/A+A/569/A52
Title:
Ultra steep spectrum radio sources
Short Name:
J/A+A/569/A52
Date:
21 Oct 2021
Publisher:
CDS
Description:
Ultra steep spectrum (USS) radio sources are one of the efficient tracers of powerful high-z radio galaxies (HzRGs). In contrast to searches for powerful HzRGs from radio surveys of moderate depths, fainter USS samples derived from deeper radio surveys can be useful in finding HzRGs at even higher redshifts and in unveiling a population of obscured weaker radio-loud AGN at moderate redshifts. Using our 325MHz GMRT observations (5{sigma}~800{mu}Jy) and 1.4GHz VLA observations (5{sigma}~80-100{mu}Jy) available in two subfields (VLA-VIMOS VLT Deep Survey (VLA-VVDS) and Subaru X-ray Deep Field (SXDF)) of the XMM-LSS field, we derive a large sample of 160 faint USS radio sources and characterize their nature. The optical and IR counterparts of our USS sample sources are searched using existing deep surveys, at respective wavelengths. We attempt to unveil the nature of our faint USS sources using diagnostic techniques based on mid-IR colors, flux ratios of radio to mid-IR, and radio luminosities. Redshift estimates are available for 86/116 (~74%) USS sources in the VLA-VVDS field and for 39/44 (~87%) USS sources in the SXDF fields with median values (z_median_)~1.18 and ~1.57, respectively, which are higher than estimates for non-USS radio sources (z_median non-USS_ ~0.99 and ~0.96), in the two subfields. The MIR color-color diagnostic and radio luminosities are consistent with most of our USS sample sources at higher redshifts (z>0.5) being AGN. The flux ratio of radio to mid-IR (S_1.4GHz_/S_3.6{mu}m_) versus redshift diagnostic plot suggests that more than half of our USS sample sources distributed over z~0.5 to 3.8 are likely to be hosted in obscured environments. A significant fraction (~26% in the VLA-VVDS and ~13% in the SXDF) of our USS sources without redshift estimates mostly remain unidentified in the existing optical, IR surveys, and exhibit high radio to mid-IR flux ratio limits similar to HzRGs, and so, can be considered as potential HzRG candidates. Our study shows that the criterion of ultra steep spectral index remains a reasonably efficient method to select high-z sources even at sub-mJy flux densities. In addition to powerful HzRG candidates, our faint USS sample also contains populations of weaker radio-loud AGNs potentially hosted in obscured environments.
16366. Ultra-steep-spectrum radio sources
ID:
ivo://CDS.VizieR/J/AJ/123/637
Title:
Ultra-steep-spectrum radio sources
Short Name:
J/AJ/123/637
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present optical and/or near-IR images of 128 ultra-steep-spectrum radio sources. Roughly half of the objects are identified in the optical images (R<~24), while in the near-IR images, more than 94% are detected at K<~22. The mean K magnitude is 19.26 within a 2" diameter aperture. The distribution of R-K colors indicates that at least one-third of the objects observed have very red colors (R-K>5). The major axes of the identifications in the K band are preferentially oriented along the radio axes, with half of them having compact morphologies. The 22 sources with spectroscopic redshifts and K-band magnitudes follow the K-z relation found from previous radio samples, but with a larger scatter.
16367. Ultra-steep spectrum radiosources
ID:
ivo://CDS.VizieR/J/A+AS/108/79
Title:
Ultra-steep spectrum radiosources
Short Name:
J/A+AS/108/79
Date:
21 Oct 2021
Publisher:
CDS
Description:
Radio sources with ultra-steep spectra (USS; spectral index <~ -1.0) have been found to be excellent tracers of galaxies at redshifts z>~2. The samples are selected from the set of catalogues referenced below, in a range of frequencies from 38 to 408MHz; they are are fainter by a factor of three than the previously well-studied samples of USS sources from 4C. Snapshot observations of sources from these samples have been made with the VLA at 1.5arcsec resolution and are presented in the printed paper. The list of the sources (Appendix A of the paper) includes positions, flux densities and radio structures for a total number of 605 sources derived from these observations.
16368. Ultra-steep spectrum radio sources
ID:
ivo://CDS.VizieR/J/A+A/436/457
Title:
Ultra-steep spectrum radio sources
Short Name:
J/A+A/436/457
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of radio (VLA) and optical (ESO/La Silla) imaging of a sample of 52 radio sources having an ultra-steep radio spectrum with {alpha} mostly steeper than -1.1 at decimetre wavelengths (median {alpha}=-1.22). Radio-optical overlays are presented to an astrometric accuracy of ~1". For 41 of the sources, radio spectral indices are newly determined using unpublished observations made with the 100-m Effelsberg radio telescope. For 14 of the sources identified with relatively brighter optical counterparts, spectroscopic observations were also carried out at La Silla and their redshifts are found to lie in the range 0.4 to 2.6.
16369. Ultra steep spectrum radio sources catalog
ID:
ivo://CDS.VizieR/J/A+AS/143/303
Title:
Ultra steep spectrum radio sources catalog
Short Name:
J/A+AS/143/303
Date:
21 Oct 2021
Publisher:
CDS
Description:
The three tables contain the 669 Ultra Steep Spectrum sources from the 3 samples WN (WENSS-NVSS), TN (TEXAS-NVSS) and MP (MRC-PMN) (tables A.1, A.2 and A.3). For each source, the radio fluxes from the surveys and from VLA or ATCA observations are given, as well as coordinates, radio structure, angular size and position angle determined from the radio map indicated in the last column.
16370. Ultra-steep spectrum radio sources in SDSS
ID:
ivo://CDS.VizieR/J/MNRAS/406/197
Title:
Ultra-steep spectrum radio sources in SDSS
Short Name:
J/MNRAS/406/197
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyse optical and radio properties of radio galaxies detected in the Sloan Digital Sky Survey. The sample of radio sources is selected from the catalogue of Kimball & Ivezic (2008AJ....136..684K) with flux densities at 325, 1400 and 4850MHz, using Westerbork Northern Sky Survey, NRAO VLA Sky Survey and Green Bank 6cm radio surveys and from flux measurements at 74MHz taken from Very Large Array Low-Frequency Sky Survey (Cohen et al. 2006, Cat. VIII/79). We study radio galaxy spectral properties using radio colour-colour diagrams and find that our sample follows a single power law from 74 to 4850MHz.

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