Physics
Scientific paper
Sep 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000phdt.........9r&link_type=abstract
Thesis (PhD). THE UNIVERSITY OF CHICAGO, Source DAI-B 61/03, p. 1450, Sep 2000, 168 pages.
Physics
8
Scientific paper
Moderate resolution spectra were recorded for 24 radio selected quasars (z ~ 2.5) discovered in the FIRST VLA survey. This work is motivated by the study of a heterogeneous set of QSO absorption line spectra which showed that as many as 36% of the absorbers normally thought to be intergalactic are correlated with physical properties of the background QSO (Richards et al. 1999). Spectra were taken for these 24 quasars in order to test this finding on a more homogeneous data set. The spectra have been searched for the most frequently observed absorption lines. The absorption line properties are compared to the radio properties of the quasars. The primary results are summarized as follows: (1)The excess of C IV absorbers in flat-spectrum quasars as compared to steep-spectrum quasars is confirmed. This excess does not seem to be the result of a bias in the quality of the QSO spectra or the QSO redshift. (2)A less significant excess of high- velocity C IV absorbers is seen in radio- quiet QSOs as compared to radio-loud QSOs. (3)The Sloan Digital Sky Survey QSO spectra will allow for the detection of a high-velocity, narrow population of intrinsic absorbers as small as 7%. (4)Though C IV is more prevalent than Mg II, high-velocity C IV absorbers in steep-spectrum quasars are observed only as often as Mg II. The true frequency of C IV absorption by intervening galaxies may be closer to that of Mg II. (5)The ``associated'' absorption population has a HWHM of ~1200kms-1 as measured from the tail of ``infalling'' absorbers. These infalling absorbers cannot be reconciled by offsets from the systemic redshift. (6)The associated systems display a tail of ``ejected'' material at blueshifts up to 6000 km s-1. This feature is not easily accounted for by a virialized population and argues for a significant contribution by ejected material. (7)The velocity distribution of associated absorbers is well centered at zero. This finding is at odds with the evidence that C IV emission redshifts are typically too small. This offset from systemic may result from C IV absorbers being tied to the C IV BELR.
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