 |
 |
|
|
My current research program involves studying the molecular, atomic,
and ionized components of the interstellar medium in galaxies. In
particular, I am looking at how the star formation rate depends on the
supply of atomic and molecular gas and how these parameters change with
galaxy type, luminosity, and environment. The goal is to find out how
and which global properties determine the yield of young stars per unit
mass of molecular gas, and the ratio of molecular to atomic gas within
and among galaxies. These studies draw on the results of the FCRAO
extragalactic CO survey, a program including participation of many
faculty, postdocs, and graduate students here at U.Mass. We have observed
the molecular content and distribution of 300 spiral and irregular galaxies
selected on the basis of their optical and infrared flux.L. Allen, J. Kenney, A. Lesser, B. Rownd, and I have also undertaken an H&alpha CCD imaging program using the now-retired #1-0.9 meter telescope at Kitt Peak. Comparison of the H&alpha and CO data provides information on the variations of star forming efficiencies with position in the 120 galaxies in our sample.
The results of the work are as follows: The ratio of molecular to atomic gas in 150 spirals decreases by a factor of 10 from Sab through Scd. However, the overall mean total gas surface density differs by only a factor of two between early and late spirals. The global yield of high mass star formation per unit molecular gas mass does not vary with type among spirals. Thus, the efficiency of high mass star formation is similar in late and early spirals. However, the yield is about seven times higher for merging/interacting galaxies than for isolated ones. Thus, galaxy collisions seem to have a large effect on the formation rate of high mass stars. For the galaxies NGC 6946 and M51, the yield of high mass stars is 2-20 times higher in the arms than between them, at the resolution of the FCRAO telescope.
The H&alpha and R-band images for
the 120 galaxies in our sample are a continuing source of research for our group. We
are also interested in making the images available to the astronomical community for
projects which involve the study of individual galaxies. If you are involved in a project
studying a galaxy for which we have an H&alpha image, feel free to copy the R-band and
H&alpha fits files, using the link below. If you have a project studying more than a handful of
galaxies, please contact me regarding use of the images. For large projects requiring the
use of a significant fraction of the images in our sample, we suggest the
possibility of a collaboration.
Whenever our images have been used, please include an acknowledgment in your publication,
and a reference to the Young et al. 1996 paper (see below). That paper describes the
observing procedure, the data calibration, and the photometric accuracy of the
observations.
For information on the images, click here.
For access to the fits files for the continuum-subtracted
H
images,
click here.
For access to the fits files for the R-band images
click here.
Last Update: 6/26/2003