Rochester, NY –
Astronomers have uncovered crucial clues to the origin and evolution
of an enigmatic class of low-mass galaxies. Dr. Eva K. Grebel,
an associate astronomer at the Max Planck Institute for Astronomy
in Heidelberg, Germany, is reporting these findings today at the
American Astronomical Society meeting in Rochester, NY. Her studies
reveal a possible evolutionary link between more massive galaxies
and the least massive dwarf galaxies known. These results are
of special interest since these dwarf galaxies are considered
ancient building blocks of galaxies such as our own Milky Way.
The recently discovered, dim dwarf spheroidal
galaxy Peg dSph, which is hiding behind bright foreground stars.
Peg dSph is a member of the class of the lowest-mass dwarf galaxies
known and a companion of the massive spiral galaxy Andromeda at
a distance of 2.5 million lightyears from us. The evolution of
Peg dSph was probably affected by the gravitational pull and ram
pressure effects from Andromeda, from which it is separated by
880,000 light years.
Picture credit:
Grebel and Guhathakurta 1999, obtained
with the W.M. Keck II telescope.
Dwarf galaxies are small, dim galaxies
that contain many fewer stars than our Milky Way. But what these
inconspicuous galaxies lack in size they make up for in numbers:
They outnumber more massive galaxies by at least a factor of 10
and are the most numerous galaxies in the Universe. Like chicks
around a hen they tend to cluster around high-mass galaxies, but
rather than being its offspring they were usually born at the
same time. The larger galaxies are thought to have consumed many
of their lesser siblings, making today's dwarfs survivors of an
earlier much richer dwarf population. Since low-mass dwarf galaxies
are usually dominated by populations with ages of several billion
years
Max Planck Institute for Astronomy
Königstuhl
17, 69117 Heidelberg, Germany
Tel.: (+49
6221) 528 0, Fax: (+49 6221) 528 246
Press Release
Embargoed For Release until 3:40 p.m. EDT, June 5, 2000
