High-redshift QSOs in the FIRST survey

Benn, C. R.; Vigotti, M.; Pedani, M.; Holt, J.;Mack, K.-H.; Curran, R.; Sánchez, S. F.. High-redshift QSOs in the FIRST survey. Monthly Notices of the Royal Astronomical Society. 2002, Vol. Volume 329, Issue 1, pp. 221-226, p. -2002.

In a pilot search for high-redshift radio quasi-stellar objects (QSOs), we have obtained spectra of 55 FIRST sources (S1.4GHz>1mJy) with very red (O-E>3) starlike optical identifications. 10 of the candidates are QSOs with redshifts 3.6<z<4.4 (four were previously known), six with z>4. The remaining 45 candidates comprise: one z=2.6 broad-absorption-line (BAL) QSO; three low-redshift galaxies with narrow emission lines; 18 probable radio galaxies; and 23 M stars (mainly misidentifications). The success rate (high-redshift QSOs / spectroscopically-observed candidates) for this search is 1/2 for S1.4GHz>10mJy, and 1/9 for S1.4GHz>1mJy. With an effective search area of 4030deg2, the surface density of high-redshift (z>4) QSOs discovered with this technique is 0.0015deg-2.