In recent years evidence has been mounting that a substantial amount of baryonic matter appears to be "missing" from our current inventory of the Universe. This implies that significant repositories of baryonic matter are awaiting discovery. The most likely form of this repository is a very diffuse galaxy whose existence is effectively masked by the brightness and noise of the night sky background. In order to determine if such galaxies exist, three observational surveys, employing different observing techniques, were undertaken to search for previously undiscovered and uncatalogued galaxies with the aim of discovering these "missing" repositories of baryonic matter. The first, and most extensive, survey was a CCD based LSB galaxy survey which found 119 previously unidentified LSB galaxies. The colors of the galaxies in the Texas survey range continuously from very blue through very red, and include a group of old galaxies which show evidence for recent star formation. This survey for LSB galaxies is the first to discover a significant population of objects with red colors, provoking the development of a computer model to examine the effects starburst activity has on galaxies and to better understand the range of colors found. The other two surveys employed space-based telescopes to determine if non-terrestrial observing techniques are effective in uncovering diffuse galaxies. The second project examined an Astro-1 UIT deep image of the Fornax cluster for purposes of determining the efficacy of vacuum ultraviolet imaging in terms of the recovery of very faint and/or diffuse galaxies. A 1000 second near-UV image detected 10 of these galaxies. The third survey employed the HST WFPC2 to search for LSB galaxies surrounding known galaxies in the Virgo cluster. Four fields were surveyed and 215 galaxies, ranging from bright ellipticals through very diffuse LSB galaxies, were found. All three survey methods proved successful, showing that much of the baryonic matter in the universe could lie in galaxies whose small angular size and/or low surface brightness has resulted in their remaining undetected until recently (if at all).
展开▼
