A brief introduction

I am an Associate Research Scholar in the Department of Astrophysical Sciences at Princeton University collaborating with Prof. Jenny Greene. Previously I was a Smithsonian Postdoctoral Fellow at the Harvard-Smithsonian Center for Astrophysics. My primary research area centers around understanding the physical mechanism by which all supermassive black holes grow, and investigating the interplay between Active Galactic Nuclei and the properties of their host galaxies.


Latest Research



X-ray Halos of Galaxies
Black Holes & Dark Matter

VIEW PROJECT

foo

Connecting Dark Matter Halos & Supermassive Black Holes

Observational studies of nearby galaxies have demonstrated correlations between the mass of the central supermassive black holes and properties of the host galaxies. Motivated by these correlations, the theoretical paradigm has emerged in which BHs and bulges coevolve. We studied 3130 elliptical galaxies selected from the Sloan Digital and ROSAT All Sky Surveys and demonstrated that the central stellar velocity dispersion exhibits a significantly tighter correlation with the total gravitating mass, traced by the X-ray luminosity of the hot gas, than with the stellar mass. This hints that the central stellar velocity dispersion, and hence the central gravitational potential, may be the fundamental property of elliptical galaxies that is most tightly connected to the larger-scale dark matter halo.

See our press coverage at the Harvard-Smithsonian and on CNET , and the Discovery Channel.

AGN-Galaxy Connections
Evolution of AGN Host Galaxies

VIEW PROJECT

foo

The evolution of AGN host galaxies throughout the last 9 billion years

AGN are capable of releasing enormous quantities of energy over their lifetimes, comparable to the binding energy of their hosts. In light of this, many galaxy-evolution simulations now incorporate AGN feedback as a form of self regulation for BH growth and star formation. The links between AGN and host evolution should be reflected in the galaxy characteristics. By harnessing the immense statistical power of the SDSS, Bootes and DEEP2 surveys, we identified AGN at X-ray, infrared and radio wavelengths out to z=1.4. We found that BHs undergoing radiatively-efficient accretion appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion. Radiatively efficient AGN appear to be preferentially hosted in modest star-forming galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically-dominated accretion are almost exclusively observed in massive, passive galaxies. Crucially, we show that these different accretion-mode AGN have remained as separate galaxy populations throughout the last 9 Gyr.

Compton-thick AGN
Mid-IR Host-Galaxy Extinction

VIEW PROJECT

foo

Mid-IR Host-Galaxy Extinction in Compton-thick AGN

In nearby optical and radio-selected AGN, a weak correlation between gas column density and silicate (Si) absorption strength has been observed from Spitzer spectroscopy suggesting that selection of sources with strong Si-absorption is a good method to find the most heavily obscured AGN, i.e., Compton-thick sources. To first-order, these results would appear to agree with those predicted by simple uniform torus models. However, there is growing evidence that not all of the dust extinction can be attributed to an obscuring central torus. Indeed, we found that those Compton-thick AGN that exhibit strong Si-absorption features in the mid-infrared are hosted in highly inclined and/or merging galaxies, providing strong evidence that significant dust attenuation occurs within the AGN host-galaxy. This host-galaxy extinction is capable of hiding optical emission-line signatures in ~25-50% of nearby AGN

See more of my research

Collaborations, Friends & Colleagues



MASSIVE:
Exploring the largest galaxies in the Universe

Learn More

foo

HyperSuprimeCam Survey
Galaxy evolution across 1400 deg2

Learn More

foo

Multi-λ Surveys
Black holes throughout cosmic time

Learn More

foo

STACKFAST
Breaking through the noise floor in X-rays

Learn More

foo

Jenny Greene
Princeton University

Learn More

foo

Dave Alexander
Durham University

Learn More

foo

Bill & Christine Forman
Harvard-Smithsonian Center for Astrophysics

Learn More

foo

Ryan Hickox
Dartmouth College

Learn More

foo

My life in pictures



foo
foo
foo
foo
foo
foo

foo
foo
foo
foo
foo
foo
Learn more