Super-massive black holes (SMBHs; >1e6 Msun) are now believed to reside at the centers of nearly all massive galaxies. As such, the cosmological evolution of AGNs and the growth of the SMBHs that power them are extremely important constraints on models of galaxy formation and evolution. Obtaining a true census of these AGN, however, has proven difficult due to various observational biases. Invariably, one must look to several different tracers such as >2keV X-ray continuum, mid-IR continuum, radio continuum/morphology, and high-ionization emission lines to understand the true AGN population. I have worked on large number of SMBH-related topics over the past ~20 years, from in-depth studies of nearby AGN to surveys of many 100s to 1000s of distant AGN, using some of the deepest Chandra, HST, Spitzer, and ground-based observations ever performed.

Current works in progress:

Galaxy Evolution:

Deep surveys have demonstrated that bright IR-selected dusty star-forming galaxies (DSFGs) trace a distinctly disjoint channel of obscured star formation from UV-selected galaxies. Both UV and IR samples need to be assessed to understand their relative contributions to cosmic star formation history. One of the most fundamental questions is how and why these different modes of star formation exist. For the past few years, I have been working on studies to find and characterize obscured and unobscured galaxies at high redshift.

Current works in progress:

Transients and Supernovae:

I began studying ultraluminous X-ray sources (ULXs) and supernovae (SNe) through the serendipitous detection of ULXs such as CG X-2 and SN1996cr wth Chandra in 2000 June (Sambruna et al. 2001, Bauer et al. 2001).

I eventually confirmed SN1996cr as a type IIn SN in 2006 using VLT spectroscopy (Bauer et al. 2007; 2008). SN1996cr showed several parallels with the peculiar SN 1987A (albeit >1000 times more luminous!), as well as nearby SN 1978K and SN 1979C. The archival X-ray and radio lightcurves and spectra for SN 1996cr indicated that a compact, dense shell was formed by the progenitor due to a dramatic stellar wind changes as little as 100 yrs prior to the SN, which created a wind-blown bubble; this rapid evolution is intriguing and must be reconciled against theoretical stellar evolution models. I have initiated wide-ranging follow-up observations of SN1996cr (see below).

SN1996cr and CG X-2 piqued my interest in transients more generally, and I am currently involved in follow-up programs to place constraints on these intriguing objects in conjunction with both the Millenium Institute of Astrophysics group and several international collaborations. I list below my ongoing/proposed projects.

Transient and SNe related projects:

Follow-up programs of SN 1996 to study its evolution:

Galactic Center:

I am involved in a several projects to study high- and low-mass X-ray binaries (HMXBs, LMXBs) in the inner 300 pc region of the Galactic Center using X-ray surveys. The goals of this study are to test various models for the Galactic Center star formation history, constrain the origin and fate of hot, X-ray emitting plasma that suffuses the region, and assemble a large sample of quiescent HMXBs for spectroscopic follow-up. Pinning down the positions of the best candidates is critical in order to facilitate meaningful multi-wavelength follow-up studies for the various underlying source populations, including the HMXBs. The lack of deep, high spatial resolution K-band imaging has been a major limitation to this point.

Current projects:

RBSC-NVSS Cross-Correlation:

For my PhD thesis (along with Jim Condon, Trinh Thuan, and John Broderick), I cross-identified the ROSAT All Sky Survey Bright Source Catalogue (RBSC; Voges et al. 1998) with the NRAO VLA Sky Survey (NVSS; Condon et al. 1998) and the USNO optical catalogue (USNO; Monet et al. 1999) to produce a well-defined sample of 1556 IDs for multi-wavelength studies. Here is a link to the full thesis in all its beastly glory (and ADS reference in case you wish to cite something from it). Here are the relevant chapters: