These are my old research pages and will no longer be updated (12/2011). Please see my new website here: http://www.ast.uct.ac.za/~hess
A copy of my CV can be found here (updated 10/11).
August 2005-Present: UW Astronomy Graduate Research, Madison, WI
Advisor: Eric Wilcots
For my thesis I am conducting a multi-wavelength study of groups around the Coma-A1367 Supercluster. The goal of this study is to better understand how environment impacts the evolution of groups and the galaxies within them. This part of the Universe that I propose to study includes a filament that stretches across the plane of the sky between the Coma and Abell 1367 clusters, centered on a redshift of cz ~ 7000 km/s. The groups in and around this supercluster inhabit a range of environments-low density regions on the edge of voids, intermediate density regions within the filament, and high density regions where the groups are falling into the cluster. Using ALFALFA, in combination with existing surveys (e.g. SDSS, 2MASS, NVSS), will provide an insight into the general properties of groups across this range of environments: the HI gas content, the group membership, galaxy colors, morphologies, and AGN frequency, for example. From my catalog, I will select a sub-sample of groups that are both interesting in their own right morphologically, as well as representative of the general group properties found across the range of environments. These groups will be the targets of a more detailed follow up study with the VLA, with WIYN, and with X-ray observations (?).
I am also interested in the problem of the hot intragroup medium. Galaxy groups fall in the intermediate range between single galaxies, and large clusters that may contain hundreds of them. When groups are observed in the X-ray, diffuse emission is detected between the galaxies that is far hotter than we expect. The temperature cannot be accounted for by heating in gravitational collapse. Other mechanisms include heating from starburst galactic outflows, and active galactic nuclei (AGN), that is, a super massive black hole at the center that is accreting materail and spewing out radiation and exciting electrons. Evidence points to the latter method as the most likely contributor. AGNs are likely a temporary state, so to trace the history of heat injection, observing low frequency synchrotron emission, may help us trace past AGN activity.
2006-2008: I searched for HI high velocity clouds in a nearby inclined spiral galaxy, NGC2997. HI clouds have been observed in the Milky Way and in nearby M31, but their origin is unknown. Leading candidates include galaxy interactions, galactic fountains, and infalling primordial HI clouds. NGC 2997 does not appear to have had a recent interactions, so the detection (or non-detection) of HI clouds places constraints on their possible origins. UPDATE: My paper can be found on NASA ADS here.
Fall 2006-Present: Arecibo
Fast Legacy ALFA Survey, Ithaca, NY & Puerto Rico
Related to my PhD Thesis. The "official" description of my project as it was submitted to the ALFALFA Oversight Committee can be viewed here. I am a member of the observing and data reduction teams.
Oversight committee: Noah Brosch, Riccardo Giovanelli, Martha Haynes, Lyle Hoffman, Brian Kent, & Emmanuel Momjian
Fall 2005-Fall 2007: UW Cosmology (Physics Dept), Madison, WI
Advisor: Peter Timbie
They are developing a bolometric interferometer to measure the polarization of the cosmic microwave background. Unfortunately, in the end I really only had time to attend groups meetings & give talks, but I remain interested in this kind of fundamental cosmology.
Summer 2005: NASA Academy Research Associate, GSFC, Greenbelt, MD
Advisors: Alan Kogut & Edward Wollack
I began the summer working on ARCADE, a balloon experiment designed to accurately measure the temperature of the cosmic microwave background (CMB) in seven frequencies. The CMB is almost a perfect blackbody at 2.73 K, however this spectrum may deviate from a true blackbody as a result of the first stars forming very early in the universe. To detect this shift, ARCADE will measure the difference between the sky temperature and the temperature of a target, that we know and can control very accurately--to better than microkelvin. Summer '05, the balloon was launched from a remote site in Eastern Texas. Things worked well, however the target did not get cold enough to measure the difference.
The rest of the summer I designed, built, and tested waveguides using stereolithography (SL). SL is a form of 3-dimensional printing. It uses a liquid photopolymer that is sensitive to UV light, to build up a 3-D object from 2-dimensional layers. Waveguides are used especially in radio and microwave astronomy as a means to collect light from the sky and direct it to a detector. Conventionally, waveguides are made from copper or aluminum, but they are usually expensive, and take a long time to design and build. Pieces made by SL are plastic, but lightweight, machinable, affordable, and have a fast turn around time. I evaluated the properties compared with conventional pieces, and their cryogenic potential (basically I got to play with liquid nitrogen).
Aug 2002-May 2005: CU Astronomy Undergraduate Research, Ithaca, NY
Advisors: Saul Teukolsky (physics) & Martha Haynes (astronomy)
Cornell's Extragalactic Group: EGG
I did a mish-mash of things, but largely worked to understand how SDSS and Arecibo observations may be used together to investigate the Tully-Fisher relation.