Kristen Garofali

My research interests lie in probing massive star and binary evolution using resolved X-ray source populations in nearby galaxies. Massive stars are catalysts in the cycle of star formation, feedback, galactic chemical evolution, and compact object formation so understanding their evolution, in particular the end stages of their lifetimes, is of great importance to a broad range of astrophysics. A list of my publications can be found here.

In particular, I study high-mass X-ray binary (HMXB) and supernova remnant (SNR) populations in nearby galaxies using a combination of Chandra, XMM-Newton, and the Hubble Space Telescope (HST) in order to learn more about the life and death cycles of massive stars, the effects of multiplicity on massive star evolution, and the influence of host galaxy properties such as metallicity, star formation history, and star formation rate on the observed populations.

My most recent work has focused on the HMXB population in M33, which we have identified and characterized using a combination of Chandra, HST, and XMM-Newton. We leverage archival data from both Chandra and the Hubble Space Telescope to identify HMXB candidates and their potential donor star counterparts (below gif). We can then measure ages for these candidate HMXBs using the surrounding stellar population as a clock. Modeling the color-magnitude diagram of the stellar population in the vicinity of a young source, such as an HMXB, yields a star formation history for that region and thus a formation timescale, or age, for that source.

This animation first displays the deep Chandra coverage available for M33 from Tullmann et al. (2011), and next the Local Group Galaxy Survey (Massey et al. 2006) of M33 overlaid with the archival HST fields pertinent to this work (magenta). Cyan and white crosses are X-ray sources from Tullmann et al. (2011) that fall within the current archival HST coverage, and the upcoming M33 HST legacy survey (white regions; PI: J. Dalcanton), respectively. The next two frames are zoom-ins on one portion of an RGB (F814W,F606W, blue equivalent) rendered HST ACS field in the disk of M33 showing a good candidate HMXB: the X-ray error circle (0.7") is in white, and the position of the potential HMXB donor star (bright, blue star) is indicated with white arrow).