We present observations of the most radio-luminous BAL quasar known , 1624+3758 , at redshift z = 3.377 .
The quasar has several unusual properties : ( 1 ) The FeII UV191 1787-Å emission line is very prominent .
( 2 ) The BAL trough ( BALnicity index 2990 kms ^ { -1 } ) is detached by 21000 kms ^ { -1 } and extends to velocity v = -29000 kms ^ { -1 } .
There are additional intrinsic absorbers at -1900 and -2800 kms ^ { -1 } .
( 3 ) The radio rotation measure of the quasar , 18350 rad m ^ { -2 } , is the second-highest known . The radio luminosity is P _ { 1.4 GHz } = 4.3 \times 10 ^ { 27 } WHz ^ { -1 } ( H _ { 0 } = 50 kms ^ { -1 } Mpc ^ { -1 } , q _ { 0 } = 0.5 ) , radio loudness R ^ { * } = 260 .
The radio source is compact ( \sol 2.8 kpc ) and the radio spectrum is GHz-peaked , consistent with it being relatively young .
The width of the CIV emission line , in conjunction with the total optical luminosity , implies black-hole mass M _ { BH } \sim 10 ^ { 9 } M _ { \odot } , L / L _ { Eddington } \approx 2 .
The high Eddington ratio , and the radio-loudness , place this quasar in one corner of Boroson ’ s ( 2002 ) 2-component scheme for the classification of AGN , implying a very high accretion rate , and this may account for some of the unusual observed properties . The v = -1900 kms ^ { -1 } absorber is a possible Lyman-limit system , with N ( HI ) = 4 \times 10 ^ { 18 } cm ^ { -2 } , and covering factor 0.7 . A complex mini-BAL absorber at v = -2200 – -3400 kms ^ { -1 } is detected in each of CIV , NV and OVI .
The blue and red components of the CIV doublet happen to be unblended , allowing both the covering factor and optical depth to be determined as a function of velocity .
Variation of covering factor with velocity dominates the form of the mini-BAL , with the absorption being saturated ( e ^ { - \tau } \approx 0 ) over most of the velocity range .
The velocity dependence of the covering factor , and the large velocity width , imply that the mini-BAL is intrinsic to the quasar .
There is some evidence of line-locking between velocity components in the CIV mini-BAL , suggesting that radiation pressure plays a role in accelerating the outflow .