A search for distant radio galaxies from SUMSS and NVSS: II. Optical Spectroscopy

Abstract

This is the second in a series of papers presenting observations and results for a sample of 76 ultra-steep-spectrum (USS) radio sources in the southern hemisphere designed to find galaxies at high redshift. Here we focus on the optical spectroscopy program for 53 galaxies in the sample. We report 35 spectroscopic redshifts, based on observations with the Very Large Telescope (VLT), the New Technology Telescope (NTT) and the Australian National University's 2.3m telescope; they include five radio galaxies with z>3. Spectroscopic redshifts for the remaining 18 galaxies could not be confirmed: three are occulted by Galactic stars, eight show continuum emission but no discernible spectral lines, whilst the remaining seven galaxies are undetected in medium-deep VLT integrations. The latter are either at very high redshift (z >~7) or heavily obscured by dust. A discussion of the efficiency of the USS technique is presented. Based on the similar space density of z>3 radio galaxies in our sample compared with other USS-selected samples, we argue that USS selection at 843-1400 MHz is an efficient and reliable technique for finding distant radio galaxies.

arXiv comment15 Pages including 49 PostScript figures. Accepted for publication in MNRAS. Corrected one author name; text unchanged

References in corpus (40)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• The many lives of active galactic nuclei: cooling flows, black holes and the luminosities and colours of galaxies
• The 2dF Galaxy Redshift Survey: Spectra and redshifts
• New Insight on Galaxy Formation and Evolution from Keck Spectroscopy of the Hawaii Deep Fields
• A Physical Model for the Co-evolution of QSOs and of their Spheroidal Hosts
• Clustering of Galaxies in a Hierarchical Universe: I. Methods and Results at z=0
• The emission line - radio correlation for radio sources using the 7C Redshift Survey
• SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. I. Science goals, survey design and instrumentation
• Old Galaxies in the Young Universe
• Deep radio imaging of the SCUBA 8-mJy survey fields: sub-mm source identifications and redshift distribution
• The radio luminosity function from the low-frequency 3CRR, 6CE & 7CRS complete samples
• Clustering of Galaxies in a Hierarchical Universe: II. Evolution to High Redshift
• Keck Spectroscopy of distant GOODS Spheroidal Galaxies: Downsizing in a Hierarchical Universe
• Near-infrared imaging and the K-z relation for radio galaxies in the 7C Redshift Survey
• Triggered Star Formation in a Massive Galaxy at z=3.8: 4C41.17
• Down-Sizing in Galaxy Formation at z~1 in the Subaru/XMM-Newton Deep Survey (SXDS)
• Jet-Induced Emission-Line Nebulosity and Star Formation in the High-Redshift Radio Galaxy 4C41.17
• Photometric redshifts from evolutionary synthesis with PEGASE: the code ZPEG and the z=0 age constraint
• Radiative Shock-Induced Collapse of Intergalactic Clouds
• Optical and Near-IR Imaging of Ultra Steep Spectrum Radio Sources - The K-z diagram of radio and optically selected galaxies
• CO(4-3) and dust emission in two powerful high-z radio galaxies, and CO lines at high redshifts
• A sample of 6C radio sources designed to find objects at redshift > 4: III --- imaging and the radio galaxy K-z relation
• A first sample of faint radio sources with virtually complete redshifts: I. Infrared images, the Hubble diagram, and the alignment effect
• The radio galaxy K-z relation: the 10^12 Msol mass limit; masses of galaxies from the L_K luminosity, up to z >4
• The evolution of early-type galaxies at z~1 from the K20 survey
• Hubble Space Telescope images of submillimeter sources: large, irregular galaxies at high redshift
• Morphological Evolution in High Redshift Radio Galaxies and the Formation of Giant Elliptical Galaxies
• Molecular gas at high redshift: jet-induced star formation?
• CO emission and associated HI absorption from a massive gas reservoir surrounding the z=3 radio galaxy B3 J2330+3927
• Spectroscopy of Ultra Steep Spectrum Radio Sources
• Radio Observations of the 13hr XMM/ROSAT Deep X-ray Survey Area
• Evidence that powerful radio jets have a profound influence on the evolution of galaxies
• Faint counts as a function of morphological type in a hierarchical merger model
• A sample of 6C radio sources designed to find objects at redshift > 4: the radio data
• CO(1-0) & CO(5-4) observations of the most distant known radio galaxy at z=5.2
• Extremely red galaxy counterparts to 7C radio sources
• Premature dismissal of high-redshift elliptical galaxies
• A search for distant radio galaxies from SUMSS and NVSS: I. Sample definition, radio and K-band imaging
• An Obscured Radio Galaxy at High Redshift

Cited by in corpus (22)

• Distant Radio Galaxies and their Environments
• Science with ASKAP - the Australian Square Kilometre Array Pathfinder
• Extragalactic Peaked-Spectrum Radio Sources at Low Frequencies
• A search for distant radio galaxies from SUMSS and NVSS: III. radio spectral energy distributions and the z-alpha correlation
• Deep GMRT 150 MHz observations of the LBDS-Lynx region: Ultra-Steep Spectrum Radio Sources
• Multiwavelength characterization of faint Ultra Steep Spectrum radio sources : A search for high-redshift radio galaxies
• A new search for distant radio galaxies in the Southern hemisphere -- III. Optical spectroscopy and analysis of the MRCR--SUMSS sample
• Imaging and Spectroscopy of Ultra Steep Spectrum Radio Sources
• Deciphering the large-scale environment of radio galaxies in the local Universe: where do they born, grow and die?
• What are the megahertz peaked-spectrum sources?
• A new search for distant radio galaxies in the southern hemisphere - I. Sample definition and radio properties
• The Australia Telescope Large Area Survey: 2.3 GHz observations of ELAIS-S1 and CDF-S
• Host Galaxies of z=4 Quasars
• The Science Case for PILOT I: Summary and Overview
• Radio-loud high-redshift protogalaxy candidates in Bootes
• Multi-line assessment of narrow-line regions in $z\sim$ 3 radio galaxies
• High-redshift quasars at $z\ge 3$: radio variability and MPS/GPS candidates
• A new search for distant radio galaxies in the Southern hemisphere -- II. 2.2 micron imaging
• Powerful Radio Sources in the Southern Sky. I. Optical Identifications
• Spatial clustering of USS sources and galaxies
• Witnessing the transformation of a quasar host galaxy at z=1.6
• Radio sources of the survey on the declination of the pulsar in Crab Nebula