On this poster we report the progress of our spectral and imaging survey
of nearby field galaxies.
Galaxy evolution is one of the key questions in current astronomy.
Recent observations of distant galaxies have provided surprising
evidence for strong and recent evolution of cluster galaxies, as well as
evidence for powerful starbursts in field galaxies. These observations
conflict with previous ideas of orderly and early galaxy evolution.
( Litt.: e.g., Broadhurst et al. 1988; Tyson 1988; Colless et al.
1990; Koo and Kron 1992; Koo et al. 1993; Lilly 1993 )
PROBLEMS IN EVOLUTION TESTS
The galaxy evolution theories can be tested by comparing the images and
spectra of galaxies at different redshifts, but two problems complicate
The purpose of our study is to obtain an accurate description of the
distribution of magnitude, structural parameters, color, and spectral
type for a large number of field galaxies. The observed emission line
strengths will allow us to measure the star formation rate in nearby
galaxies with greater precision than was previously possible. In
addition, we will use absorption line diagnostics to study the star
formation history of these galaxies, as demonstrated by Caldwell et
al. (1993) for galaxies in the Coma Cluster. The magnitude and
structural parameters (effective radius and surface brightness) are
necessary to calculate the detection rates at increasing redshift.
These data will be used as an aid in understanding the spectra of
galaxies at higher redshift, and in measuring the changes in star
formation rates over time.
SURVEY WHAT?; SAMPLE SELECTION
Because many galaxy properties like color, star formation rate and
emission line strength correlate with magnitude (e.g. Moody and
Kirshner 1988), our sample must span a broad range in absolute
magnitude. As a result, we want to avoid a purely magnitude or diameter
limited sample. We chose a mixed approach: we selected galaxies from
the first CFA redshift catalogue, which contains galaxies to a limiting
magnitude of m_B=14.5 (Huchra et al. 1983). We calculated the
absolute magnitude for each galaxy, and put galaxies in 1 magnitude
bins. We then drew galaxies from each bin so that the magnitude
distribution approximated the observed galaxy luminosity function.
Thus, of the 1006 galaxies that met our selection criteria, 196
SPECTRA AND IMAGES
We are in the process of obtaining integrated spectra at higher
resolution (4.5-6.0 Å ) and for a larger sample (196) than is
available in the literature (e.g. Kennicutt 1992). The FAST
spectrograph at the F.L.Whipple Observatory's 60'' Telescope
(Mt. Hopkins, Arizona) is mounted
with a thinned Loral 2720 x 512 CCD giving a spectral range of either
3250--7250Å or 3600--7500Å at 1.5Å per pixel and a
total throughput of telescope, spectrograph and CCD of ~ 55% at
(of the four galaxies shown on this poster) _________________________________________________ GALAXY NAME UGC # V_LG M_B TYPE _________________________________________________ A 1159+6237 7009 1120 -15.98 10 A 1552+1645 10086 2206 -17.31 -2 A 1531+6744 9896 6461 -19.72 5A IC 4213 8280 815 -15.58 5A _________________________________________________Table 1: Cross-reference to the UGC catalog, velocity with respect to the Local Group (km/sec), absolute blue magnitude for H0=100 km/sec/Mpc and numerical type for the four galaxies presented here.
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