- 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.
Number of results to display per page
Search Results
- 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.
- 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.
- 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.
- 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.
- 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.
14817. Ultraviolet Excess Galaxies
- ID:
- ivo://CDS.VizieR/VII/63
- Title:
- Ultraviolet Excess Galaxies
- Short Name:
- VII/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog contains a list of 412 faint galaxies selected for their apparent ultraviolet excess. The galaxies were selected from a 3-color (UBV) plate taken with the Palomar 48-inch Schmidt telescope. The 14-inch-square plates cover an area of 30 square degrees centered on Kapteyn Selected Area 28. The catalog includes running numbers, coordinates, color codes, magnitude codes, morphologies, diameters, and notes. The catalogued galaxies were selected by eye from the Palomar Schmidt 3-color (UBV) plate PS24771, centered on Kapteyn Selexted Area 28 and taken by Usher under conditions of good seeing and transparency.
- ID:
- ivo://CDS.VizieR/J/ApJ/861/153
- Title:
- Ultraviolet Extinction in the GALEX Bands. UVEXT
- Short Name:
- J/ApJ/861/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interstellar extinction in ultraviolet is the most severe in comparison with optical and infrared wavebands and a precise determination plays an important role in correctly recovering the ultraviolet brightness and colors of objects. By finding the observed bluest colors at the given effective temperature and metallicity range of dwarf stars, stellar intrinsic colors, C_B,V_^0^, C_NUV,B_^0^, C_FUV,B_^0^, and C_FUV,NUV_^0^, are derived according to the stellar parameters from the LAMOST spectroscopic survey and photometric results from the GALEX and APASS surveys. With the derived intrinsic colors, the ultraviolet color excesses are calculated for about 25,000 A- and F-type dwarf stars. Analysis of the color excess ratios yields the extinction law related to the GALEX UV bands: E_NUV,B_/E_B,V_=3.77, E_FUV,B_/E_B,V_=3.39, and E_FUV,NUV_/E_B,V_=-0.38. The results agree very well with previous works in the NUV band and in general with the extinction curve derived by Fitzpatrick (1999PASP..111...63F) for R_V_=3.35.
14819. Ultraviolet P Cygni profiles
- ID:
- ivo://CDS.VizieR/J/ApJS/95/163
- Title:
- Ultraviolet P Cygni profiles
- Short Name:
- J/ApJS/95/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have selected spectra of 232 stars from the IUE archives for inclusion in an atlas intended for various uses but tailored especially for the study of stellar winds. The atlas covers the range in spectral types from O3 to F8. The full atlas covers the reduced and normalized high resolution spectra from the IUE long- and short-wavelength spectrographs. Here we discuss the selection of the stars and the data reduction, and we present in velocity units the profiles of lines formed in the stellar winds. The selected lines cover a wide range of ionizations, allowing a comparison of the profiles from different ions in the wind of each star and a comparison of the different wind lines as a function of spectral type and luminosity. We also present the basic data on the program stars to facilitate study of the dependence of wind features on stellar parameters such as luminosity, temperature, escape velocity, and v sin i. We provide an overview of the characteristic behavior of the wind lines in the H-R diagram. The complete spectra are available in digital form through the NASA Astrophysics Data System (ADS). We offer a description of the electronic database that is available through the ADS and guidelines for obtaining access to that database.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3761
- Title:
- Ultraviolet quasi-stellar objects
- Short Name:
- J/AJ/137/3761
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of spectroscopically confirmed quasi-stellar objects (QSOs) with FUV-NUV color (as measured by Galaxy Evolution Explorer (GALEX) photometry, FUV band: 1344-1786{AA}, NUV band: 1771-2831{AA}) bluer than canonical QSO templates and than the majority of known QSOs. We analyze their FUV to NIR colors, luminosities, and optical spectra. The sample includes a group of 150 objects at low redshift (z<0.5), and a group of 21 objects with redshift 1.7<z<2.6.
