Radiogalaxies in the Sloan Digital Sky Survey: spectral index-environment correlations

CARLOS BORNANCINI; ANA LAURA O'MILL; SEBASTIÁN GUROVICH; DIEGO GARCÍA LAMBAS

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Wiley-Blackwell

Año: 2010 vol. 406 p. 197 - 207

0035-8711

We analyze optical and radio properties of radiogalaxies detected in the Sloan Digital Sky Survey (SDSS). The sample of radio sources are selected from the catalogue of Kimball & Ivezi\'c (2008) with flux densities at 325, 1400 and 4850 MHz, using WENSS, NVSS and GB6 radio surveys and from flux measurements at 74 MHz taken from VLA Low-frequency Sky Survey \citep{cohen}. We study radiogalaxy spectral properties using radio colour-colour diagrams and find that our sample follows a single power law from 74 to 4850 MHz. The spectral index vs. spectroscopic redshift relation ($\alpha-z$) is not significant for our sample of radio sources. We analyze a subsample of radio sources associated with clusters of galaxies identified from the maxBCG catalogue and find that about 40% of radio sources with ultra steep spectra (USS, $\alpha