A search for distant radio galaxies from SUMSS and NVSS: III. radio spectral energy distributions and the z-alpha correlation

Details A search for distant radio galaxies from SUMSS and NVSS: III. radio spectral energy distributions and the z-alpha correlation A search for distant radio galaxies from SUMSS and NVSS: III. radio spectral energy distributions and the z-alpha correlation

2006-06-20

arxiv.org/abs/astro-ph/0606469v1

Mon.Not.Roy.Astron.Soc.371:852-866,2006

Astronomy and Astrophysics

Astrophysics

MNRAS in press

Scientific paper

10.1111/j.1365-2966.2006.10714.x

This is the third in a series of papers that present observations and results for a sample of 76 ultra-steep-spectrum radio sources designed to find galaxies at high redshift. Here we present multi-frequency radio observations, from the Australia Telescope Compact Array, for a subset of 37 galaxies from the sample. Matched resolution observations at 2.3, 4.8 and 6.2GHz are presented for all galaxies, with the z<2 galaxies additionally observed at 8.6 and 18GHz. New angular size constraints are reported for 19 sources based on high resolution 4.8 and 6.2GHz observations. Functional forms for the rest-frame spectral energy distributions are derived: 89% of the sample is well characterised by a single power law, whilst the remaining 11% show some flattening toward higher frequencies: not one source shows any evidence for high frequency steepening. We discuss the implications of this result in light of the empirical correlation between redshift and spectral index seen in flux limited samples of radio galaxies. Finally, a new physical mechanism to explain the redshift -- spectral index correlation is posited: extremely steep spectrum radio galaxies in the local universe usually reside at the centres of rich galaxy clusters. We argue that if a higher fraction of radio galaxies, as a function of redshift, are located in environments with densities similar to nearby rich clusters, then this could be a natural interpretation for the correlation. We briefly outline our plans to pursue this line of investigation.

Affiliated with

Also associated with

No associations

Rating

A search for distant radio galaxies from SUMSS and NVSS: III. radio spectral energy distributions and the z-alpha correlation does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with A search for distant radio galaxies from SUMSS and NVSS: III. radio spectral energy distributions and the z-alpha correlation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A search for distant radio galaxies from SUMSS and NVSS: III. radio spectral energy distributions and the z-alpha correlation will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-39453