Spatial clustering of USS radio sources and galaxies

BORNANCINI CARLOS G.; PADILLA NELSON; DE BREUCK CARLOS; GARCÍA LAMBAS DIEGO

Foz do Iguaçu

Congreso; IAG--LENAC XIII Advanced School of Astrophysics & LENAC Special Session; 2006

IAG & LENAC

We present measurements of the clustering properties of galaxies in the field of redshift range 0.5 <~z<~ 1.5 Ultra Steep Spectrum radio sources selected from the Sydney University Molonglo Sky Survey and the National Radio Astronomy Observatories Very Large Array Sky Survey. Galaxies in these USS fields were identified in deep near-infrared observations, complete down to Ks= 20, using the IRIS2 instrument at the Anglo-Australian Telescope. We used the redshift distribution of Ks < 20 galaxies taken from Cimatti et al. (2002) to constrain the correlation length r0. We find a strong correlation signal of galaxies with Ks < 20 around our USS sample. A comoving correlation length r0= 14.0 +/- 2.8h-1 Mpc and gamma= 1.98 +/- 0.15 are derived in a flat cosmological model universe. We compare our findings with those obtained in a cosmological N-body simulation populated with GALFORM semi-analytic galaxies. We find that clusters of galaxies with masses in the range M= 1013.4-14.2h-1Msolar have a cluster-galaxy cross-correlation amplitude comparable to those found between the USS hosts and galaxies. These results suggest that distant radio galaxies are excellent tracers of galaxy overdensities and pinpoint the progenitors of present day rich clusters of galaxies.