- ID:
- ivo://CDS.VizieR/J/A+A/638/A46
- Title:
- The XXL Survey. XLI. GMRT XXL-N 610MHz
- Short Name:
- J/A+A/638/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the space density evolution of active galactic nuclei (AGN) using the 610MHz radio survey of the XXL-North field, performed with the Giant Metrewave Radio Telescope (GMRT). The survey covers an area of 30.4deg^2^, with a beamsize of 6.5arcsec. The survey is divided into two parts, one covering an area of 11.9deg^2^ with 1{sigma} rms noise of 200uJy/beam and the other spanning 18.5deg^2^ with rms noise of 45uJy/beam. We extracted the catalog of radio components above 7. The catalog was cross-matched with a multi-wavelength catalog of the XXL-North field (covering about 80% of the radio XXL-North field) using a likelihood ratio method, which determines the counterparts based on their positions and their optical properties. The multi-component sources were matched visually with the aid of a computer code: Multi-Catalog Visual Cross-Matching (MCVCM). A flux density cut above 1mJy selects AGN hosts with a high purity in terms of star formation contamination based on the available source counts. After crossmatching and elimination of observational biases arising from survey incompleteness, the number of remaining sources was 1150. We constructed the rest-frame 1.4GHz radio luminosity functions of these sources using the maximum volume method. This survey allows us to probe luminosities of 23<~log(L1.4GHz[W/Hz])<~28 up to redshifts of z~=2.1. Our results are consistent with the results from the literature in which AGN are comprised of two differently evolving populations, where the high luminosity end of the luminosity functions evolves more strongly than the low-luminosity end.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/157/194
- Title:
- Total ALFALFA H I fluxes for extended sources
- Short Name:
- J/AJ/157/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A procedure is presented to improve on measurement of total H I fluxes for extended sources in the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey of neutral hydrogen sources in the nearby universe. A number of tests of the procedure are detailed, and we verify that we recover all of the flux measured with much larger telescope beams. Total fluxes are reported for all sources (1) exceeding 10 Jy km/s in the {alpha}.100 catalog (Haynes et al. 2018ApJ...861...49H), or (2) with Uppsala General Catalog (Cat. VII/26) diameters 3.0 arcmin or more, or (3) ALFALFA pipeline isophotal ellipse area more than 3.0 times the Arecibo beam. Total fluxes are also provided for a number of confused pairs and small groups including one or more of those high-flux sources. These data should be of use in baryonic Tully-Fisher studies and other applications where the measurement of the total reservoir of neutral atomic gas is important.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A113
- Title:
- Towards Cosmicflows-4 HI data catalog
- Short Name:
- J/A+A/646/A113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this study, we present an update of a compilation of line width measurements of neutral atomic hydrogen (HI) galaxy spectra at 21 cm wavelength. Our All Digital HI (ADHI) catalog consists of the previous release augmented with our new HI observations and an analysis of archival data. This study provides the required HI information to measure the distances of spiral galaxies through the application of the Tully-Fisher (TF) relation. We conducted observations at the Green Bank telescope (GBT) and reprocessed spectra obtained at the Nancay radiotelescope by the Nancay Interstellar Baryons Legacy Extragalactic Survey (NIBLES) and Kinematics of the Local Universe (KLUN) collaborations and we analyzed the recently published full completion Arecibo Legacy Fast ALFA (ALFALFA) 100% survey in order to identify galaxies with good quality HI line width measurements. This paper adds new HI data adequate for TF use for 385 galaxies observed at GBT, 889 galaxies from archival Nancay spectra, and 1515 rescaled Arecibo ALFALFA spectra. In total, this release adds 1274 new good quality measurements to the ADHI catalog. Today, the ADHI database contains 18,874 galaxies, for which 15,433 have good quality data for TF use. The final goal is to compute accurate distances to spiral galaxies, which will be included in the next generation of peculiar velocities catalog: Cosmicflows-4. This paper adds new HI data adequate for TF use for 385 galaxies observed at GBT, 889 galaxies from archival Nancay spectra, and 1515 rescaled Arecibo ALFALFA spectra. In total, this release adds 1274 new good quality measurements to the ADHI catalog. Today, the ADHI database contains 18874 galaxies, for which 15433 have good quality data for TF use. The final goal is to compute accurate distances to spiral galaxies, which will be included in the next generation of peculiar velocities catalog: Cosmicflows-4.
- ID:
- ivo://CDS.VizieR/J/AJ/121/2381
- Title:
- UBRI photometry of radio galaxies
- Short Name:
- J/AJ/121/2381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a new estimate of the radio galaxy 1.4 GHz luminosity function and its evolution at intermediate redshifts (z~0.4). Photometric redshifts and color selection have been used to select B_J_<23.5 early-type galaxies from the Panoramic Deep Fields, a multicolor survey of two 25deg^2^ fields. Approximately 230 radio galaxies have then been selected by matching early-type galaxies with NVSS radio sources brighter than 5mJy. Estimates of the 1.4GHz luminosity function of radio galaxies measure significant evolution over the observed redshift range. For an {Omega}_M_=1 cosmology the evolution of the radio power is consistent with luminosity evolution where P(z)~P(0)(1+z)^K_L_^ and 3<K_L_<5. The observed evolution is similar to that observed for UVX and X-ray selected active galactic nuclei and is consistent with the same physical process being responsible for the optical and radio luminosity evolution of active galactic nuclei.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A92
- Title:
- Ultracompact extragalactic radio sources at 86GHz
- Short Name:
- J/A+A/622/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Very long baseline interferometry (VLBI) observations at 86 GHz (wavelength, {lambda}=3mm) reach a resolution of about 50{mu}as, probing the collimation and acceleration regions of relativistic outflows in active galactic nuclei (AGN). The physical conditions in these regions can be studied by performing 86GHz VLBI surveys of representative samples of compact extragalactic radio sources. To extend the statistical studies of compact extragalactic jets, a large global 86GHz VLBI survey of 162 compact radio sources was conducted in 2010-2011 using the Global Millimeter VLBI Array (GMVA). The survey observations were made in a snapshot mode, with up to five scans per target spread over a range of hour angles in order to optimize the visibility coverage. The survey data attained a typical baseline sensitivity of 0.1Jy and a typical image sensitivity of 5mJy/beam, providing successful detections and images for all of the survey targets. For 138 objects, the survey provides the first ever VLBI images made at 86GHz. Gaussian model fitting of the visibility data was applied to represent the structure of the observed sources and to estimate the flux densities and sizes of distinct emitting regions (components) in their jets. These estimates were used for calculating the brightness temperature (Tb) at the jet base (core) and in one or more moving regions (jet components) downstream from the core. These model-fit-based estimates of Tb were compared to the estimates of brightness temperature limits made directly from the visibility data, demonstrating a good agreement between the two methods. The apparent brightness temperature estimates for the jet cores in our sample range from 2.5x10^9^K to 1.3x10^12^K, with the mean value of 1.8x10^11^K. The apparent brightness temperature estimates for the inner jet components in our sample range from 7.0x10^7^K to 4.0x10^11^K. A simple population model with a single intrinsic value of brightness temperature, T0, is applied to reproduce the observed distribution. It yields T0=(3.77^+0.10^_0.14_)10^11^K for the jet cores, implying that the inverse Compton losses dominate the emission. In the nearest jet components, T0=(1.42^+0.16^_0.19_)10^11^K is found, which is slightly higher than the equipartition limit of 5x10^10^K expected for these jet regions. For objects with sufficient structural detail detected, the adiabatic energy losses are shown to dominate the observed changes of brightness temperature along the jet.
- 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.
- 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/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.
- ID:
- ivo://CDS.VizieR/J/AJ/148/16
- Title:
- Updated 3CRR sample of radio sources
- Short Name:
- J/AJ/148/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the consistency of the unified scheme of Fanaroff-Riley type II radio galaxies and quasars with their observed number and size distributions in the 3CRR sample. We separate the low-excitation galaxies from the high-excitation ones, as the former might not harbor a quasar within and thus may not be partaking in the unified scheme models. In the updated 3CRR sample, at low redshifts (z<0.5), the relative number and luminosity distributions of high-excitation galaxies and quasars roughly match the expectations from the orientation-based unified scheme model. However, a foreshortening in the observed sizes of quasars, which is a must in the orientation-based model, is not seen with respect to radio galaxies even when the low-excitation galaxies are excluded. This dashes the hope that the unified scheme might still work if one includes only the high-excitation galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A107
- Title:
- Variability of 198 extragalactic radio sources
- Short Name:
- J/A+A/553/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining measurements taken using the Wilkinson Microwave Anisotropy Probe (WMAP) from 2001 to 2008 with measurements taken using Planck from 2009 to 2010, we investigate the long-term flux density variability of extragalactic radio sources selected from the Planck Early Release Compact Source Catalogue. The single-year, single-frequency WMAP maps are used to estimate yearly-averaged flux densities of the sources in the four WMAP bands: Ka (33GHz), Q (41GHz), V (61GHz), and W (94GHz). We identify 82, 67, 32, and 15 sources respectively as variable at greater than 99% confidence level in these four bands. The amplitudes of variation are comparable between bands, and are not correlated with either the flux densities or the spectral indices of the sources. The number counts of WMAP Ka-band sources are stable from year to year despite the fluctuation caused by individual source variability. Most of our sources show strong correlation in variability between bands. Almost all the sources that show variability are blazars. We have attempted to fit two simple, four-parameter models to the time-series of 32 sources showing correlated variability at multiple frequencies - a long-term flaring model and a rotating-jet model. We find that 19 sources (60%) can be fit with the simple rotating-jet model, and ten of these also fit the simple long-term flaring model. The remaining 13 sources (40%) show more complex variability behaviour that is not consistent with either model. Extended radio galaxies in our sample show no sign of variability, as expected, with the exception of Pictor A for which we report evidence for a millimetre flare lasting between 2002 and 2010.
