AAS 197, January 2001
Session 111. Galaxy Morphology and Structure
Display, Thursday, January 11, 2001, 9:30-4:00pm, Exhibit Hall

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[111.10] Stellar Populations of LSB galaxies: spectral observations with the HET

M. Bergmann (Univ. of Texas, Austin), I. Jorgensen (Gemini Observatory)

We present good S/N low resolution spectra of eleven Low Surface Brightness (LSB) galaxies, observed with the Low Resolution Spectrograph on the Hobby-Eberly Telescope. The spectra cover a range of 4300Å < \lambda < 7000Å. The galaxies were chosen from the survey of O'Neil et al (1996), and cover a range of colors, from blue to very red. Four of the LSB galaxies have pure absorption line spectra, three of the galaxies have measurable absorption and emission features, and the remaining spectra show only emission features. We measure redshifts for each of the galaxies, and derive absorption line index strengths and emission line ratios, where appropriate.

The objects form a very heterogeneous group, with radial velocities ranging from 3000 km/s to 60,000 km/s (and not always in agreement with previously published velocities based on single dish HI observations). The absolute total magnitudes range from MB=-16 to MB=-21.5. Single Burst Stellar Population models for the four LSB's with no current star formation give luminosity weighted mean ages of 5.6Gyr with solar metallicity, to 17Gyr and 1/3 solar metallicity for the oldest system. For the galaxies with emission, the H\alpha equivalent widths range from 5Å- 78Å. The [NII]/H\alpha vs. [OIII]/H\beta emission line diagnostic is consistent with stellar HII regions as the ionizing source in all the emission line systems. We discuss these results in the context of various LSB galaxy formation models.

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