Astronomy and Astrophysics – Astronomy
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21431103l&link_type=abstract
American Astronomical Society, AAS Meeting #214, #311.03; Bulletin of the American Astronomical Society, Vol. 41, p.746
Astronomy and Astrophysics
Astronomy
Scientific paper
We present an analysis of new and archive VLA HI observations of a sample of 11 early-type galaxies rich in CO. We have compared these new HI maps to existing high resolution CO maps in an effort to better understand what physical factors determine the relative amounts of cold gas in early-type galaxies. Five of the eleven galaxies in the sample are detected in both HI and CO. The HI and CO in most of the galaxies is distributed in regular rotating disks. The H2/HI mass ratios for this sample range from 0.2-120. The behavior of the molecular fraction in our sample is broadly similar to that observed in field spirals. Recently it has been observed that the ratio of molecular to atomic gas in spiral galaxies is determined by hydrostatic pressure and the relation between the two is nearly linear. In order to explore whether this relationship also exists in early-type galaxies we have developed a realistic model of the stellar density/potential distribution using a multi-Gaussian expansion (MGE) fit to 2MASS K-band images. The stellar models show that in some cases the stellar density drops below the gas density within the transition radius and so the self gravity of the gas becomes important. Calculating the pressure using total gas maps constructed from the HI and CO maps and the stellar density derived from the MGE models indicate that the H2/HI is indeed linearly correlated with the midplane hydrostatic pressure. We also find that the central pressures in the disturbed and HI deficient early-types tend to be at least an order of magnitude greater than the normal field early-types.
Lucero Danielle M.
Young Lisa Marie
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