Chemical Abundances in Giant LSB Disk Galaxies

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Session 39 -- Spiral, Dwarf and Irregular Galaxies
Display presentation, Wednesday, June 14, 1995, 9:20am - 6:30pm

[39.07] Chemical Abundances in Giant LSB Disk Galaxies

T. E. Pickering, C. D. Impey (Steward Observatory)

Some of the largest galaxies known belong to the so-called ``Malin-type'' class of galaxies. Like their prototype, Malin 1 (Impey \& Bothun 1989), these galaxies have large scale lengths ($>10$ kpc, $H_{0} = 100$ km s$^{-1}$ Mpc$^{-1}$), low central surface brightnesses, and generally large HI masses ($> 10^{10} M_{\odot}$). Previous studies of chemical abundances of LSB galaxies (e.g. McGaugh 1994) have found them to have generally low metallicities ($Z < \frac{1}{3}Z_{\odot}$). However, only a couple galaxies in this sample have scale lengths of greater than 10 kpc. The APM survey for LSB galaxies (Impey et al.\ 1995) has turned up 10 more Malin-type galaxies as defined by a ``diffuseness index'' $\mu_{B} + 5 \log \alpha^{-1} > 27.0$ (Sprayberry et al.\ 1995). We present preliminary results from a program to study the chemical abundances in these galaxies via spectroscopy of H II regions. Preliminary analysis has found that some of these galaxies have fairly high metallicities with $Z \simeq Z_{\odot}$ or more. This is somewhat surprising since these galaxies seem otherwise rather unevolved. Along with other evidence, this seems to imply that these galaxies have undergone previous episodes of star formation or have been slowly forming stars for some time.

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