Absorption in three intrinsically faint quasars: Q 0009-016, Q 0347-241, and Q 2116-358

Details Absorption in three intrinsically faint quasars: Q 0009-016, Q 0347-241, and Q 2116-358 Absorption in three intrinsically faint quasars: Q 0009-016, Q 0347-241, and Q 2116-358

Jul 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...287..719m&link_type=abstract

Astronomy and Astrophysics 287, 719-732 (1994)

Astronomy and Astrophysics

Astrophysics

23

Galaxies: Abundances, Intergalactic Medium, Quasars: Absorption Lines, Quasars: Individual: Q 0009-016, Q 0347-241, Q 2116-358

Scientific paper

We present spectra of three intrinsically faint (M_V_>-27) quasars: Q 0009-016 (z_em_=1.997), Q 0347-241 (z_em_=1.881) and Q 2116-358 (z_em_=2.341). A total of 6 CIV absorption systems are detected, half of which are z_abs_=~z_em_ systems occurring within {DELTA}v=+/-5000 km/s of the emission redshift. This high occurrence of z_abs_=~z_em_ absorption is consistent with the existence of a statistical excess of CIV absorption systems near the quasar redshift, and with the hypothesis that such systems tend to occur in objects intrinsically fainter than M_V_=~-27. In Q 0347-241, a new example of a z_abs_>z_em_ system is found, having an apparent relative velocity of {DELTA}v=~-900 km/s with respect to the background quasar. The lack of NV absorption seen in this high-ionisation system suggests that the absorbing gas is under-abundant in nitrogen with respect to carbon by a factor of 10-100. Q 2116-358 exhibits two close z_abs_ =~z_em_ systems at relative velocities {DELTA}v=~+3100 km/s and {DELTA} v=~+2000km/s. The ionisation levels of these two systems are markedly different, and correspond to a factor =~20 difference in ionisation parameter. Moreover, the two systems are `inverted' in the sense that the lower ionisation system is the one closest to Q 2116-358 in velocity. A damped Lyα system with hydrogen column density of N_HI_=~1.4x10^20^cm^-2^ is also detected in Q 2116-358 at z_abs_=1.9966. An analysis of the observed line strengths indicates that the data are all consistent with heavy element abundances of 3% of solar values. Previous determinations of metalicities of intervening systems have all resulted in values of <=20% of solar. In contrast, all three z_abs_=~z_em_ systems have [C/H]>0, and we take this as evidence that z_abs_=~z_em_ systems constitute a distinct class of absorbers of different nature than the intervening systems.

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