A search for UV absorption lines from low-redshift galaxies

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Session 4 -- AGNs
Display presentation, Monday, 9:20-6:30, Pauley Room

[4.20] A search for UV absorption lines from low-redshift galaxies

David V. Bowen, J. C. Blades (STScI), Max Pettini (Royal Greenwich Observatory)

We present the results of a search for UV absorption lines in the spectra of quasars and supernovae whose sightlines probe the disks and haloes of low-redshift galaxies. Our survey concentrates on looking for Mg~II$\lambda\lambda 2796,2803$ and C~IV$\lambda\lambda 1548,1550$ resonance absorption lines using the Goddard High Resolution Spectrograph (GHRS) aboard HST. This instrument provides very sensitive limits ($30-60$~m\AA ) for detecting absorption from intervening gas.

We have selected seven quasars, SN 1992A, and SN 1993J to probe the interstellar media of many types of galaxies, including a spheroidal dwarf (Leo I), two irregulars (LMC and UGC 1807), an elliptical (NGC 1380), and numerous field and cluster spirals. The separations between QSO sightline and galaxy range from $2-3$~kpc to $\sim\:100\:h^{-1}$~kpc. Of the data obtained so far, we find Mg~II absorption towards Mrk~205, which shines through the disk of NGC~4319, and SN 1993j which exploded in M83 and which was observed at 3~km~s$^{-1}$ resolution with the GHRS echelle grating. In both cases the separations are small. We fail to find absorption towards any of the other pairs, including some with equally small separations. In contrast, the local Galactic Mg~II lines, which are often observed simultaneously are always strong, and contain important velocity information on Milky Way halo gas.

Monday program listing