A Probable Overabundance of Phosphorus in the Broad Absorption Line Region of the QSO PG 0946+301

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Session 42 -- Metallicity in AGN and the Near-AGN Environment
Oral presentation, 8:30am - 12:30pm, June 14, 1995, 9:20am - 6:30pm

[42.08] A Probable Overabundance of Phosphorus in the Broad Absorption Line Region of the QSO PG 0946+301

V. T. Junkkarinen, E. A. Beaver, E. M. Burbidge, R. D. Cohen, F. Hamann, R. W. Lyons (CASS/UCSD), T. A. Barlow (Caltech)

HST/FOS UV spectra (G190H and G270H) of the BALQSO PG 0946+301 (V = 16, $\rm z_e$ = 1.223) show absorption features that correspond to P V $\lambda$$\lambda$1118,1128 and P IV $\lambda$951 at the redshift ($\rm z_a$ = 1.149) of the strongest absorption component in the Si IV $\lambda$$\lambda$1394,1403 and C IV $\lambda$$\lambda$1548,1551 absorption troughs. All of the features mentioned above have a FWHM of roughly 550 $\rm km~s^{-1}$. The resolution of the G270H and G190H spectra is about half this value, and random unblended Ly $\alpha$ forest lines have widths near the instrumental resolution. The large widths of the apparent P V and P IV features increase the probability that these features are at least somehow associated with the BAL region. Modeling the absorption near $\lambda$1120\AA \ (rest) with only seven Fe III lines (rest wavelengths from 1122.5\AA \ to 1131.4 \AA ), using a template created from the Si IV BAL, produces a significantly worse fit than modeling that spectral region with broad P V $\lambda$$\lambda$1118,1128 absorption. We conclude that the most likely identification is P V. The inferred column densities for C IV and P V are: N(C IV) $\approx$ $9 \times 10^{15}$ $\rm cm^{-2}$ and N (P V) $\approx$ $7 \times 10^{14}$ $\rm cm^{-2}$. If the above column density estimates are accurate and the BAL region is photoionized, then the estimated elemental abundance ratio is C/P $\approx$ 13. Since the cosmic abundance ratio C/P = 1000 (Gravese and Anders, 1989 Cosmic Abundances of Matter, AIP, Conf. Proc. ed. C. J. Waddington (New York: AIP), 183), phosphorus is probably overabundant relative to carbon by a factor of 80 in the PG 0946+301 BALR. We compare our results with other evidence for enchanced element abundances in BALQSOs (Turnshek, 1988, in QSO Absorption Lines: Probing the Universe, 8 and Korista et al. 1992, ApJ, 401, 529).

This research has been supported in part by NASA NAS5--29293 and NAG5--1630.

8:30a program listing