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Research
I am working with Dr. Rene Walterbos on two different projects involving star
formation in other galaxies which will be combined in my dissertation thesis.
Star Formation in HI Selected Galaxies:
The first project involves using broad-band B and R and narrow-band H-alpha
images of 69 galaxies selected from the HI Parkes All Sky Survey (HIPASS) to explore
star formation in low surface brightness (LSB) galaxies that optically selected
samples are biased against. As expected, our HIPASS sample contains a higher
fraction of relatively bluer, more LSB galaxies than an optically selected
comparison sample. We have found that the most LSB galaxies that are
missed by optical samples may make up as much as 14% of the local number density
while only making up about 3% of the total star formation rate (SFR) density and
1% of the luminosity density. Schmidt law population synthesis models were used to
estimate the typical mean age for the galaxies in our sample to be approximately
4 Gyr with a rms deviation of about 3.2 Gyr, implying that the progenitors of
these objects should contain few if any stars at redshifts greater than 1. We
also find that the most LSB galaxies in the sample form lower luminosity HII
regions and have higher diffuse fractions (the fraction of the H-alpha luminosity
attributed to diffuse ionized gas) than typical disk galaxies. This implies that
either these galaxies form smaller star clusters than typical spirals or the HII
regions in these objects leak a significant fraction of their ionizing photons into
the ISM. A paper dealing with the general sample properties has been accepted to
the Astrophysical Journal and is scheduled for publication on October 1, 2004; a
second paper on the HII region properties has been submitted to the Astrophysical
Journal.
Star Formation in Early-type Galaxies:
The second project deals with a large spectroscopic sample (~37,000 galaxies) of
early-type (E, S0, and Sa) galaxies taken from the second data release of the
Sloan Digital Sky Survey. We are using this sample to identify star forming early-
type galaxies to explore the possibility that they are the progenitors of post-star-
burst early-type galaxies referred to as E+A galaxies. We are in the process of
preparing two papers on this project; one that deals with the sample selection,
general properties, and abundance of star forming and E+A galaxies as functions of
galaxy environment and redshift. The second deals with the results of the use of
population synthesis models to explore the possible distributions for the star
formation time scales in these objects. We have also been awarded time on the
Apache Point Observatory (APO) 3.5 meter telescope to image a subsample of nearby
star forming early-type galaxies to explore the large scale distributions of
star forming regions within these objects which will be the subject of a third
paper.
Publications
Star Formation in HI Selected Galaxies. II. HII Region Properties, 2005, ApJ, accepted
Star Formation in HI Selected Galaxies. I. Sample Characteristics, 2004, ApJ, 613, 914
Actively Star-forming Elliptical Galaxies at Low Redshifts in the Sloan Digital Sky Survey, 2004, ApJL, 601, 127
The First Data Release of the Sloan Digital Sky Survey, 2004, AJ, 126, 2081
Meetings
SDSS Collaboration Meetings:
Spring 2004 (NMSU): presented talk on star formation in early-type galaxies during Galaxy Working Group meeting
Fall 2003 (FNAL): presented talk on star formation in early-type galaxies during Galaxy Working Group meeting
Spring 2003 (USNO)
Fall 2002 (Princeton)
AAS meetings:
Winter 2005 (meeting no. 205): presented dissertation talk, Star Formation in Early-type Galaxies
Summer 2002 (meeting no. 200): presented two posters, Star Formation Properties of HI Selected Galaxies I. Overall properties, and Star Formation Properties of HI Selected Galaxies II. HII Regions Characteristics
Summer 2001 (meeting no. 198): presented talk, Star Formation Properties of HIPASS Galaxies I: Sample Characteristics
Postdoctoral Work
I successfully defended my Ph.D. thesis on Star Formation at the Extreme Ends of the Hubble Sequence, on August 7, 2005. I then accepted a postdoctoral fellowship at the University of New Mexico, to work with Greg Taylor. I have joined the Long Wavelength Array (LWA) team, developing a New Mexico radio telescope aray which will explore the Universe at frequencies in the range 20-80 MHz with arcsecond level resolution and mJy level sensitivity.