C. Roger Lynds
Dr. C. Roger Lynds is an observer at the National
Optical Astronomy Observatories (NOAO) in Tucson,
AZ. His main areas of interest include Galaxy Evolution
and Cosmology. Dr. Lynds has been engaged in two
types of projects bearing on the subject of star
formation histories of galaxies. One approach has
been to study the photometric characteristics of
galaxies revealed in long-exposure images obtained
with the Hubble Space Telescope. The aim is to develop
evidence of a higher incidence of star formation
at great distances and early epochs in the lifetime
of the Universe. In particular, are we beginning
to see galaxies in their first phase of star formation
when we go to very early epochs?
At the other end of the distance scale, Lynds has
been working on local galaxies dominated by current
star formation. The goal has been to determine whether
or not there are any galaxies at the current epoch
which are undergoing their very first phase of star
formation. One galaxy, VII-Zw-403, a very blue,
dwarf galaxy, was originally thought to be an entirely
new galaxy. However, Hubble Space Telescope observations
reveal that there is a smoothly distributed, evolved
population of stars in which the star forming regions
are embedded. Another galaxy, I-Zw-18, has seemed
to be an even more promising example of an entirely
new galaxy. It is somewhat more distant than VII-Zw-403
so that only the supergiants and blue main sequence
stars are resolved, but Lynds has found evidence
that there is a substructure of unresolved red stars
which likely represent the giant branch of an evolved
population of stars. The conclusion may very well
be that, at the current epoch, star formation only
occurs within the gravitational potential wells
of galaxies of older stars.
Dr. Lynds's future research is expected to continue
along much the same lines. He hopes to develop evidence
of a relationship between the abundance of heavy
elements in star-forming regions and the mass of
neutral hydrogen clouds in which the host galaxy
may be embedded. One might expect that if such hydrogen
clouds are essentially primordial, having few if
any heavy elements, any stars formed from such material
would reflect that fact.
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