Open AccessUnusual high‐redshift radio broad absorption‐line quasar 1624+3758
Author(s) -
Benn C. R.,
Carballo R.,
Holt J.,
Vigotti M.,
GonzálezSerrano J. I.,
Mack K.H.,
Perley R. A.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09143.x
Subject(s) - physics , quasar , astrophysics , redshift , active galactic nucleus , astronomy , emission spectrum , luminosity , spectral line , accretion (finance) , galaxy
We present observations of the most radio‐luminous broad absorption‐line (BAL) quasar known, 1624+3758, at redshift z = 3.377 . The quasar has several unusual properties. (1) The Fe ii UV191 1787‐Å emission line is very prominent. (2) The BAL trough (BALnicity index 2990 km s −1 ) is detached by 21 000 km s −1 and extends to velocity v =−29 000 km s −1 . There are additional intrinsic absorbers at −1900 and −2800 km s −1 . (3) The radio rotation measure of the quasar, 18 350 rad m −2 , is the second highest known. The radio luminosity is P 1.4 GHz = 4.3 × 10 27 W Hz −1 ( H 0 = 50 km s −1 Mpc −1 , q 0 = 0.5) and the radio loudness is R *= 260 . The radio source is compact and the radio spectrum is GHz‐peaked, consistent with it being relatively young. The width of the C iv emission line, in conjunction with the total optical luminosity, implies a black hole mass M BH ∼ 10 9 M ⊙ , L / L Eddington ≈ 2 . The high Eddington ratio and the radio‐loudness place this quasar in one corner of Boroson's two‐component scheme for the classification of active galactic nuclei, implying a very high accretion rate, and this may account for some of the unusual observed properties. The v =−1900 km s −1 absorber is a possible Lyman‐limit system, with N (H i ) = 4 × 10 18 cm −2 , and a covering factor of 0.7. A complex mini‐BAL absorber at v =−2200 to −3400 km s −1 is detected in each of C iv , N v and O vi . The blue and red components of the C iv doublet happen to be unblended, allowing both the covering factor and optical depth to be determined as a function of velocity. Variation of the covering factor with velocity dominates the form of the mini‐BAL, with the absorption being saturated (e −τ ≈ 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 C iv mini‐BAL, suggesting that radiation pressure plays a role in accelerating the outflow.