Discovery of radio-loud quasars with z=4.72 and z=4.01

被引:41
作者
Hook, IM
McMahon, RG
机构
[1] Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA
[2] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England
关键词
quasars; general; individual; GB1428+4217; GB1713+2148;
D O I
10.1046/j.1365-8711.1998.01368.x
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We report the discovery of two radio-loud quasars with redshifts greater than 4: GB1428 + 4217, with z = 4.72, and GB1713 + 2148 with z = 4.01. This doubles the number of published radio-selected quasars with z>4, bringing the total to 4. GB1428 + 4217 is the third most distant quasar known and the highest redshift radio and X-ray source currently known. It has a radio flux density at 5 GHz of 259 +/- 31 mJy and an optical magnitude of R similar to 20.9. The rest frame absolute UV magnitude, M-v(1450 Angstrom), is -26.7, similar to that of the archetypal radio-selected quasar 3C273 [z = 0.158; M-v(1450 Angstrom) = -26.4]. GB1428 + 4217 is tentatively detected in ROSAT PSPC observations, which has been confirmed by more recent ROSAT observations described in a companion paper by Fabian et al. Both quasars were discovered during the CCD imaging phase of an investigation into the evolution of the space density of radio-loud quasars at high redshift. Combined with our earlier survey results, these objects give a lower limit on the space density of quasars with radio power P-5GHz > 5.8 x 10(26) W Hz(-1) sr(-1) between z = 4 and z = 5 of 1.4 +/- 0.9 x 10(-10) Mpc(-3). This can be compared to 2.9 +/- 0.2 x 10(-10) Mpc(-3) at z = 2 from Dunlop & Peacock for flat-spectrum sources of the same luminosity.
引用
收藏
页码:L7 / L12
页数:6
相关论文
共 29 条
[1]   THE ULTRAVIOLET-ABSORPTION SPECTRUM OF 3C-273 [J].
BAHCALL, JN ;
JANNUZI, BT ;
SCHNEIDER, DP ;
HARTIG, GF ;
BOHLIN, R ;
JUNKKARINEN, V .
ASTROPHYSICAL JOURNAL, 1991, 377 (01) :L5-L8
[2]  
Brinkmann W, 1997, ASTRON ASTROPHYS, V323, P739
[3]  
DUNLOP JS, 1990, MON NOT R ASTRON SOC, V247, P19
[4]   The extreme X-ray luminosity of the z=4.72 radio-loud quasar GB 1428+4217 [J].
Fabian, AC ;
Brandt, WN ;
McMahon, RG ;
Hook, IM .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1997, 291 (01) :L5-L7
[5]  
FALCO EE, 1997, UNPUB APJ
[6]   OBSCURATION OF QUASARS BY DUST IN DAMPED LYMAN-ALPHA SYSTEMS [J].
FALL, SM ;
PEI, YC .
ASTROPHYSICAL JOURNAL, 1993, 402 (02) :479-492
[7]   FAINT SPECTROPHOTOMETRIC STANDARD STARS FOR LARGE OPTICAL TELESCOPES .1. [J].
FILIPPENKO, AV ;
GREENSTEIN, JL .
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 1984, 96 (581) :530-536
[8]   THE 87GB CATALOG OF RADIO-SOURCES COVERING 0-DEGREES-LESS-THAN-DELTA-LESS-THAN+75-DEGREES AT 4.85 GHZ [J].
GREGORY, PC ;
CONDON, JJ .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1991, 75 (04) :1011-1291
[9]  
Hall PB, 1996, ASTROPHYS J, V462, P614, DOI 10.1086/177177
[10]   The space density of quasars at z>4 [J].
Hawkins, MRS ;
Veron, P .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1996, 281 (01) :348-356