AAS 203rd Meeting, January 2004
Session 70 Interstellar Medium
Oral, Tuesday, January 6, 2004, 2:00-3:30pm, Regency VII

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[70.02] The Neutral Interstellar Medium in Nearby Luminous Compact Blue Galaxies

C. A. Garland, J. P. Williams (Institute for Astronomy, University of Hawaii), D. J. Pisano (CSIRO Australia Telescope National Facility), R. Guzmán, F. J. Castander (University of Florida)

We observed 20 nearby Luminous Compact Blue Galaxies (LCBGs) in H {\small{I}} and CO(J=2-1) with the GBT and JCMT. These ~L\star galaxies are blue, high surface brightness, starbursting, high metallicity galaxies with an underlying older stellar population. They are common at z~1, but rare in the local Universe. It has been proposed that intermediate redshift LCBGs may be the progenitors of local dwarf ellipticals or low luminosity spirals, or that they may be more massive disks forming from the center outward to become L\star galaxies. To discriminate between the various possible evolutionary scenarios it is essential to measure their masses--to check whether these objects are as massive as implied by their high luminosities--and their gas content for future star formation to constrain the amount of fading of their stellar populations.

To measure the dynamical masses and gas properties of LCBGs we chose a local (D \leq 70 Mpc) sample from the Sloan Digital Sky Survey using the same color (B-V \leq 0.6), surface brightness (SBe \leq 21 mag arc sec-2), and luminosity (MB \leq -18.5) criteria as intermediate redshift LCBGs.

We find a wide range of gas properties in local LCBGs. H {\small{I}} masses span the range found in nearby spirals, while gas fractions, MHI/MDYN(R < R25), range from normal spiral to gas rich galaxies. The fractions of molecular to atomic gas mass are consistent with late-type low luminosity spirals.

From the H {\small{I}} spectra, the dynamical masses (within R25) range from 4 \times 109 to 1 \times 1011 M\odot, consistent with local late-type spirals and dwarf ellipticals. Many nearby LCBGs have smaller dynamical masses than local galaxies of the same luminosity. Using IRAS star formation rates, we find the molecular gas may be depleted in 3 \times 107 to 2 \times 108 years, while the atomic gas may be depleted in 3 \times 107 to 1 \times 1010 years. These findings indicate that LCBGs are a heterogeneous group of galaxies; they are not likely to evolve into one homogeneous galaxy class.

The author(s) of this abstract have provided an email address for comments about the abstract: garland@ifa.hawaii.edu

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