A sample of radio-loud QSOs at redshift ~ 4
Abstract
We obtained spectra of 60 red, starlike objects (E< 18.8) identified with FIRST radio sources, S_{1.4GHz} > 1 mJy. Eight are QSOs with redshift z> 3.6.Combined with our pilot search (Benn et al 2002), our sample of 121 candidates yields a total of 18 z > 3.6 QSOs (10 of these with z > 4.0). 8% of candidates with S_{1.4GHz}< 10 mJy, and 37% of candidates with S_{1.4GHz}> 10 mJy are QSOs with z > 3.6. The surface density of E < 18.8, S_{1.4GHz} > 1mJy, z> 4 QSOs is 0.003 deg^{-2}. This is currently the only well-defined sample of radio-loud QSOs at z ~ 4 selected independently of radio spectral index. The QSOs are highly luminous in the optical (8 have M_B < -28, q_0 = 0.5, H_0 = 50 kms^{-1}Mpc^{-1}). The SEDs are as varied as those seen in optical searches for high-redshift QSOs, but the fraction of objects with weak (strongly self-absorbed) Ly alpha emission is marginally higher (3 out of 18) than for high-redshift QSOs from SDSS (5 out of 96).
Keywords
Cite
@article{arxiv.astro-ph/0311127,
title = {A sample of radio-loud QSOs at redshift ~ 4},
author = {J. Holt and C. R. Benn and M. Vigotti and M. Pedani and R. Carballo and J. I. Gonzalez-Serrano and K. -H. Mack and B. Garcia},
journal= {arXiv preprint arXiv:astro-ph/0311127},
year = {2009}
}
Comments
Accepted for publication in MNRAS, 9 pages, Latex, 5 postscript figures, 1 landscape table (postscript)