OBSERVATIONAL ASTRONOMY

My primary research utilizes multi-wavelength observations (X-ray through mid-infrared) in the investigation of local stellar populations. Of particular interest is the use of star clusters and giant stars to probe the structure and evolution, chemical and dynamical, of the Milky Way and other Local Group galaxies. Related issues such as the role of environment and dark matter content of Miliky way satellite galaxies are also currently under study.

GALACTIC STRUCTURE & DYNAMICS

Understanding the structure of a galaxy from only one point of view is challenging, however being inside that galaxy makes it much more difficult. We understand more about other galaxies sturcture than we do for our own Milky Way. Using the Spitzer Space Telescope and Two Micron All-Sky Survey (2MASS) plus dynamical data, we are able to explore the Galaxy as never before. We are using Galactic stars clusters as dynamical probes to determine the structure and evolution of the Milky Way.
 

Galactic Chemical Evolution (SDSS-III/APOGEE)
In addition to the dynamical work on the Galaxy, I am also a leader of the Sloan Digital Sky Survey III/Apache Point Observatory Galactic Evolution Experiment (SDSS-III/APOGEE). SDSS-III/APOGEE will survey 100,000 stars in the galaxy to measure kinematics and provide detailed chemical analysis of 17 elements in these stars. Many of these stars will be in star clusters. Thus, we will have age-dated tracers with good distances and chemistry suitable for investigating the chemical evolution of the Galactic disk.

Stellar Populations
One way to recreate the history of a galaxy is by examining the stellar populations within that galaxy. The basis for understanding observations of other galaxies relies on a deep understanding of local stellar populations. The WIYN Open Cluster Study (WOCS), , aims to provide the most details stellar population study of key nearby star clusters.

My current WOCS research focuses on the infrared (near and mid-IR) properties of the WOCS clusters, which is being used to derive the lower end of the mass function, and binary star populations of the clusters. The primary facility for Mid-IR imaging is the Spitzer Space Telescope. Consisting of a 0.85-meter telescope and the cryogenically-cooled IRAC camera, Spitzer allows the WOCS clusters to be investigated by obtaining photometry at 3.6-8.0 microns. In addition to the WOCS optical data, we have obtained deep phtometry with the IRAC observations. Deep NIR (i.e., J,H,Ks) observation are being conducted with a number of ground bases facilities. Some of this work is done in collaboration with research groups at Texas A&M University and the University of Wisconsin.

Dark Matter and Local Group Galaxies
Cosmological Cold Dark Matter (CDM) models predict that a galaxy like the Milky Way should have 100's of satelite gallaxies filled with dark matter. The reality is that the Milky Way has tens of satellites and how much dark matter they have is not well determined. A major complication in measuring this is that many of these galaxies are also being torn apart by the Milky Way. The dynamics of dwarf galaxies and stellar streams is the key to understand the evolution of dark matter on small scales. I have worked on exploring the Milky Way dwarf satellites, including Sagittarius, the Magellanic Clouds, GASS, Carina, Leo I and II, Ursa Minor, and Sculptor, as well as, investigating star clusters associated with the Galactic Anticenter Stellar Structure "GASS", also know as the "Ring", that may be associated with the proposed "Argo" or "Canis Major" dwarf galaxy. Much of this work is done in collaboration with research groups at the University of Virginia.

Tombaugh 2: the first open cluster with a significant abundance spread or embedded in a cold stellar stream (with Marino, A. F.; Villanova, S.; Carraro, G.; Majewski, S. R.; Geisler, D.), MNRAS, 391, 39 (2008)

Open Clusters as Galactic Disk Tracers. I. Project Motivation, Cluster Membership, and Bulk Three-Dimensional Kinematics (with Majewski, S.R.), Astronomical J., 136, 188 (2008)

Photometry and Spectroscopy of Old, Outer Disk Star Clusters: vdB-Hagen 176, Berkeley 29, and Saurer 1 (with Munoz, R.R.; Phelps, R.L.; Majewski, S.R.; Kunkel, W.E.), Astronomical J., 131, 922 (2006)

Star Clusters in the Galactic Anticenter Stellar Structure and the Origin of Outer Old Open Clusters (with Majewski, S.R.; Crane, J.D.; Reid, I.N.; Rocha-Pinto, H.J.; Phelps, R.L.; Patterson, R.J.; Munoz, R.R.) Astrophys. J. Letters, 602, 21 (2004)