The optical/near-IR colors of broad absorption line quasars, including the candidte radio-loud BAL quasar 1556+3517

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Title: The optical/near-IR colors of broad absorption line quasars, including the candidte radio-loud BAL quasar 1556+3517
Author: Hall, Patrick; Martini, Paul; Depoy, Darren; Gatley, Ian
Abstract: A candidate radio-loud broad absorption line quasar (RLBAL) has been reported by Becker et al. (1997). We present JHK observations of this object and three other radio-detected BALs taken with the new Michigan-Dartmouth-MIT/Ohio State/Aladdin IR Camera (MOSAIC) on the KPNO 4-meter. The candidate RLBAL 1556+3517 has B−K=6.63, redder than all but one or two known z>1 quasars. This strongly suggests the observed continuum of this quasar is reddened by dust. Even when this extreme reddening is taken into account 1556+3517 is still probably radio-loud, although near-IR spectroscopy to measure its Balmer decrement will be needed to verify this. In addition, since it is a flat-spectrum object, VLBI observations to determine the extent (if any) to which beaming affects our estimate of its radio luminosity will be needed before 1556+3517 can be unequivocally declared a radio-loud BAL. We also use our data and data from the literature to show that optically selected BALs as a class have B−K colors consistent with the observed distribution for optically selected quasars as a whole. Thus there is currently no evidence that the tendency of optically selected BALs to be preferentially radio-intermediate (Francis, Hooper, & Impey 1993) is due to extinction artificially lowering estimated BAL optical luminosities. However, as most quasar surveys, both radio and optical, would be insensitive to a population of reddened radio-quiet BALs, the existence of a large population of reddened BALs similar to 1556+3517 cannot yet be ruled out. (Refer to PDF file for exact formulas).
Description: Also archived in: arXiv:astro-ph/9704182 v2 15 May 1997
Record URI: http://hdl.handle.net/1850/1914
Date: 1997-07-20

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