Astronomy of Various Kinds

Want to see Fan Mountain's first light?

A high resolution VLA image of NVSS 2146+82, the second largest known FRII radio galaxy.

• Click here for my curriculum vita (HTML format).
• Click here for my curriculum vita (PS format, more up-to-date version).
• Click here for a few links to astronomy resources on the Web.

Research Interests:

• Galactic Structure
• Globular Cluster Dynamics
• Galaxy Formation and Evolution
• AGN (specifically radio galaxies and blazars)

• Milky Way Satellite and Globular Cluster Orbital Alignments: While I was considering various thesis topics, I began work on a side project that became the first part of my thesis (with Steve Majewski). We searched for fossil evidence of accretion events in the Milky Way halo. Assuming the Searle & Zinn picture of the halo having formed from accretion of fragments is correct, we should be able to find evidence of such accretion events in the current distribution of satellites in the halo. Support for this idea includes the Sagittarius dwarf, which shows signs of ongoing tidal disruption by the Milky Way, the alignment of the rest of the dwarf galaxy satellites along Lynden-Bell's two "Great Streams", and association of young second parameter globular clusters with the Sagittarius and Fornax dwarf galaxies. Assuming this picture is correct, we should find that satellites disrupted or created in a common tidal event should share similar orbital trajectories in galactic coordinates. We have therefore compared the distribution of the orbital parameters of certain subsamples of globular clusters and dwarf satellite galaxies searching for evidence of common orbital poles.
  
  
• The Pyxis Globular Cluster: Our analysis of the spatial and dynamical associations between globular clusters and Milky Way satellite galaxies suggests to us that the Pyxis globular cluster is a likely candidate to have been tidally torn from the Magellanic Clouds by the Milky Way. We have therefore begun the process of measuring its space motion by getting a radial velocity for several bright giants in the cluster. In addition, we were able to measure a spectroscopic metallicity for the brightest star, confirming the values derived photometrically by CMD fitting. Assuming the LMC capture origin is correct for Pyxis, we published a prediction for its proper motion given our measured radial velocity. This article will appear in the October, 2000 issue of PASP.
  
  
• Other Milky Way Halo Studies: I've collaborated on several projects with other members of the Majewski research group here at UVa. I've contributed to our study of the Sagittarius dwarf (Majewski, Siegel et al. 1999), the Magellanic Stream (Majewski, Ostheimer et al. 2000), and Omega Cen (Majewski, Patterson et al. 2000). Also, I participated in the study of a potential stellar moving group found serendipitously among field stars surrounding NGC 6791 (Peterson, Green, Majewski, & Palma 2000).
  
  
• The Giant FR II NVSS 2146+82: My Master's research project involved optical observations of the giant FR II radio galaxy, NVSS 2146+82. This object was discovered in the first field observed during the NRAO VLA Sky Survey ( NVSS); an observation which occurred while I was an REU summer student at NRAO's VLA site in 1994. As a group, the summer students were given VLA time to observe an object of our choice. Naturally, we chose to use our group time to observe this beast. It turns out that Alan Bridle and Bill Cotton have been following up on this object with the VLA, so I decided to look into the optical properties of the FR II host galaxy. With Dr. Steven Majewski I've observed the host in the UBVRI with the Palomar 60". Majewski and Matt Bershady also took spectra of the host as part of a separate observing program. Mike Siegel kindly donate 5 minutes of KPNO 4m time to get a few deep images in V and I, also. We have determined the redshift of the host to be z=0.145, indicating a linear size of 4 Mpc from lobe to lobe! What is the most interesting, though, is that this giant FR II appears to be near the edge of a dense group of galaxies, possibly of Abell richness class 0. An article is available in the May, 2000 issue of AJ (vol. 119, p. 2068) with the VLA maps, optical spectra, and optical photometry of the galaxy. In addition, we were awarded some ROSAT time (just prior to its untimely demise) to search for any hot IGM associated with the overdensity of galactic companions found associated with the host galaxy. Although we were unable to detect the IGM, our upper limit is consistent with the values found for other low redshift Abell Class 0 clusters containing FR II radio galaxies.
  
  
• VLA Imaging of BL Lacs:As an undergraduate at Penn State, I got started in astronomical research by working with Dr. Eric Feigelson. I spent a summer reducing approximately 750 snapshot images taken with the Very Large Array (that's the array of radio telescopes pictured above). The snapshots have been used to help identify a new, complete sample of BL Lacertae objects. (the results became part of Sally Laurent-Muehleisen's PhD thesis.) For my senior thesis, 'Radio Images of the Final Seven BL Lac Objects from the HEAO-1 Large Area Sky Survey and their Impact on Unified Scheme Theory', I calibrated and reduced VLA A and B configuration observations of 7 BL Lacs from the HEAO-1 sample. My thesis was published as part of the paper, 'Radio Constraints on Relativistic Beaming Models of BL Lacertae Objects' ApJ 465,115.