ROSAT OBSERVATIONS OF QUIESCENT LOW-MASS DISK GALAXIES - NO EVIDENCE OF BARYONIC BLOW-OUT

To test the hypothesis that galactic winds associated with star formation in low mass disk galaxies can be an effective means of relocating cold disk gas to a warm tenuous halo, we have obtained long exposure ROSAT PSPC observations of three such galaxies. The sensitivity of the PSPC to the presence of an extended, approximately 0.15 KEV halo of 10(9) M. of gas, is quite high for the exposure times we used. We failed to detect this halo in all three cases and the observed x-ray luminosity of the galaxy is two orders of magnitude less than the hypothetical case in which the mass of gas that has been expelled by previous generations of star formation is equal to the stellar mass of the galaxy itself This limit is much less than the actual mass of cold gas in these galaxies. Thus, we were unable to verify directly the presence of significant galactic winds in these three galaxies either because they are not operative, because their halos are not sufficiently massive to aid in the retention of this gas, or because the amount of injected gas is just a small percentage of the cold disk gas. if the latter reason is emblematic of low mass galaxies then we would not expect the detection of halos. We also report here the serendipitous detection of Abell 1560, a distance class 7 cluster of unknown redshift.