Schneider, Stephen

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Professor, Department of Astronomy
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Astrophysics and Astronomy
My research centers around issues of low surface brightness (and possibly "no surface brightness") objects. I am interested in dynamical estimates and observational determinations of the amount of mass present in a wide variety of objects--clusters of galaxies, groups of galaxies, individual galaxies, and even planetary nebulae. My slant on this research is to investigate whether our natural human bias toward visible wavelengths of light has biased us against detecting certain classes of objects.
The class of low surface brightness galaxies appaears to be large but it is poorly studied. These galaxies' visual surface brightnesses barely exceed the sky background and have therefore been overlooked in most optical surveys. However, dynamical studies we have made of these galaxies' rotation speeds indicate that they are comparable in mass to the largest "normal" spiral galaxies. The mystery is why they show such weak star formation despite their mass. This may be due to a lack of interactions with other galaxies,
A more fundamental question is how many of these objects populate the universe? Unfortunately, objects with little star formation are difficult to detect at almost any wavelength, since stars are the ultimate source that powers almost all of the emission from galaxies. One of the only alternatives is to study the emission of neutral hydrogen at 21 cm, which is a primordial material and does not require starlight to excite the transition.
Our blind surveys are detecting many previously uncataloged objects which have a wide range of properties. They include nearby faint dwarf galaxies, peculiar objects which defy simple classification schemes. and the low surface brightness giants described above. This research is perhaps an indication that much of our understanding of extragalactic space is still in its infancy.
I have undertaken a wide array of observations here at the Five College Radio Astronomy Observatory, and at observatories around the country: the Arecibo Observatory in Puerto Rico, the VLA in New Mexico, the GBT in West Virginia, Nancay in France, and Kitt Peak in Arizona.

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