Keck HIRES Spectra of Three Broad Absorption-Line QSOs

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Session 18 -- AGN Spectroscopy
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[18.13] Keck HIRES Spectra of Three Broad Absorption-Line QSOs

T.A. Barlow and V.T. Junkkarinen (CASS/UCSD)

We have observed three broad absorption-line QSOs (BALQSOs) with the Keck HIRES spectrograph with a resolution of 8 km s$^{-1}$ and a signal-to-noise of roughly 30-40 per resolution element. We chose three bright, high-redshift QSOs: Q1246-057 ($z_{em}$=2.22), CSO 755 (1524+517, $z_{em}$=2.88), and Q1408+567 ($z_{em}$=2.50). All three QSOs have detached (8,000 to 15,000 km s$^{-1}$ outflow) C IV $\lambda$1549 BALs which appear smooth in lower resolution spectra.

In all cases, the BAL troughs remained smooth such that the lines appear to be fully resolved even at lower resolution (200 km s$^{-1}$). This refutes suggestions made in previous studies that the BALs may be composed of narrow, optically thick components which could have explained the apparent high metallicity and/or the observation of apparently saturated doublet lines which do not reach zero intensity.

If we assume the the BAL region is made up of clouds with FWHM velocity dispersions of about 6 km s$^{-1}$ (10,000 K), then these BALs must be made up of at least several thousand components. This gives a limit on the cloud sizes of $<10^7$ meters (assuming $n_e>10^6$ and N(H)$\simeq 10^{19}$.)

We also observed several narrower absorption lines near the BALs which may be related to BAL phenomenon. Most of these lines appear broad, resolved, and do not break up into obvious components. The structure of these lines appear to differ from systems with $z_{abs}<P> This work has been supported by NASA Grant NAG 5-1630.

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