The redshift distribution of FIRST radio sources at 1 mJy (original) (raw)

Radio sources in the 2dF Galaxy Redshift Survey: AGN, starburst galaxies and their cosmic evolution

Radio continuum surveys can detect galaxies over a very wide range in redshift, making them powerful tools for studying the distant universe. Until recently, though, identifying the optical counterparts of faint radio sources and measuring their redshifts was a slow and laborious process which could only be carried out for relatively small samples of galaxies. Combining data from all-sky radio continuum surveys with optical spectra from the new large-area redshift surveys now makes it possible to measure redshifts for tens of thousands of radio-emitting galaxies, as well as determining unambiguously whether the radio emission in each galaxy arises mainly from an active nucleus (AGN) or from processes related to star formation. Here we present some results from a recent study of radio-source populations in the 2dF Galaxy Redshift Survey, including a new derivation of the local star-formation density, and discuss the prospects for future studies of galaxy evolution using both radio an...

Redshifts of CLASS Radio Sources

Astronomical Journal, 2000

Spectroscopic observations of a sample of 42 flat-spectrum radio sources from the Cosmic Lens All-Sky Survey (CLASS) have yielded a mean redshift of <z>=1.27<z> = 1.27<z>=1.27 with an RMS spread of 0.95, at a completeness level of 64%. The sample consists of sources with a 5-GHz flux density of 25-50 mJy, making it the faintest flat-spectrum radio sample for which the redshift distribution has been studied. The spectra, obtained with the Willam Herschel Telescope (WHT), consist mainly of broad-line quasars at z>1z>1z>1 and narrow-line galaxies at z<0.5z<0.5z<0.5. Though the mean redshift of flat-spectrum radio sources exhibits little variation over more than two orders of magnitude in radio flux density, there is evidence for a decreasing fraction of quasars at weaker flux levels. In this paper we present the results of our spectroscopic observations, and discuss the implications for constraining cosmological parameters with statistical analyses of the CLASS survey.

Unveiling the population of high-redshift radio galaxies using centimeter GMRT survey

arXiv: Astrophysics of Galaxies, 2014

Ultra Steep Spectrum (USS) radio sources are one of the efficient tracers of High Redshift Radio Galaxies (HzRGs). To search for HzRGs candidates, we investigate properties of a large sample of faint USS sources derived from our deep 325 MHz GMRT observations combined with 1.4 GHz VLA data on the two subfields (i.e., VLA-VIMOS VLT Deep Survey (VVDS) and Subaru X-ray Deep Field (SXDF)) in the XMM-LSS field. The available redshift estimates show that majority of our USS sample sources are at higher redshifts with the median redshifts ~ 1.18 and ~ 1.57 in the VLA-VVDS and SXDF fields. In the VLA-VVDS field, ~ 20% of USS sources lack the redshift estimates as well as the detection in the deep optical, IR surveys, and thus these sources may be considered as potential high-z candidates. The radio luminosity distributions suggest that a substantial fraction (~ 40%) of our USS sample sources are radio-loud sources, distributed over redshifts ~ 0.5 to 4.