A HIRES Detection of Na I D Absorption in the Spectrum of the QSO PKS 2020$-$370 Due to the Galaxy Klemola 31A
Session 13 -- Integalactic medium
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

## [13.05] A HIRES Detection of Na I D Absorption in the Spectrum of the QSO PKS 2020$-$370 Due to the Galaxy Klemola 31A

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

By using the Keck telescope and HIRES spectrograph we have detected Na I D absorption lines in the spectrum of the QSO PKS 2020$-$370 (V = 17.5, z = 1.048) due to the galaxy Klemola 31A (z = 0.0288). The PKS 2020$-$370 line of sight is near an apparent spiral arm only 20{\tt"} from the nucleus of Klemola 31A which corresponds to 17 kpc ($\rm H_o$ = 50 $\rm km~s^{-1}~Mpc^{-1}$). The spectrum of PKS 2020$-$370 has strong Ca II absorption lines ($\rm W_{\lambda}$ $\approx$ 350 m\AA \ for the K line) at the galaxy redshift (Boksenberg et al, 1980, ApJ, 242, L145), but previous attempts to detect Na I have resulted in upper limits (Boisse et al. 1988, A\&A, 191, 193, Womble, 1992, thesis UCSD). We observed PKS 2020$-$370 with HIRES in May 1994 at a resolution of 8 $\rm km~s^{-1}$ FWHM for a total of 90 minutes. The Na I D doublet is detected with a total $\rm W_{\lambda}$ for the Na I 5891.6 \AA \ (vac) absorption line of about 160 m\AA . The absorption appears as two main velocity components separated by 23 $\rm km~s^{-1}$. The optically thin estimate for N(Na I) = 1.0 $\times$ $10^{12}$ $\rm cm^{-2}$ gives an estimated N(Ca II)/N(Na I) = 5. This value suggests that the gas in Klemola 31A along the QSO line of sight is halo like''. Along disk like'' lines of sight where Ca is thought to be depleted onto grains in our Galaxy, the N(Ca II)/N(Na I) ratio is usually small ($\le$ 1). Other QSO--galaxy pairs often show disk like N(Ca II)/N(Na I) ratios when the line of sight intersects starlight at 25 mag per sq. arcsec (Womble, 1992 thesis UCSD). The PKS 2020$-$370 sightline is near the optical extent of Klemola 31A but the N(Ca II)/N(Na I) is consistent with the sightline passing through two clouds in the halo.

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