Research

I’m a civil servant astrophysicist at the NASA Goddard Space Flight Center.  My research focuses on the evolution of star-forming galaxies and central black holes.  CV.   Publications on ADS.

Before coming to NASA, I was a Carnegie Fellow and Spitzer Fellow at the Carnegie Observatories; graduate student at Steward Observatory, Univ. of Arizona; and undergraduate at Penn State.

Advising:

I actively recruit graduate students in the Washington/ Baltimore area to conduct research with me.  I sponsor postdocs through the NASA Postdoctoral Program, as well as the Hubble and Einstein fellowship programs.  Please contact me at  or my NASA email.

The big picture of my research:

My research focuses on two topics: galaxies that are rapidly forming stars, and the black holes that lurk in the centers of galaxies.   Galaxies built themselves up through violent, vigorous bursts of star formation; such events are rare today, but were common in the past.   I want to know how this star formation worked.   But since distant starburst galaxies are too faint to study in detail, I “cheat” by using gravitational telescopes: rare cases where the light from galaxies has been magnified by factors of ~30x. This lets me push past the limits of current telescopes, to see how galaxies formed their stars.

I’m also fascinated by the million-to-billion solar mass black holes that lurk in the centers of galaxies, particularly those that are hidden by thick clouds of gas and dust. I experiment with new ways to find such buried black holes and to measure their properties and their impact on their host galaxies.

Experts may add this jargon to the above: active galactic nuclei (AGN), Compton-thick, multiwavelength diagnostic spectroscopy, gravitational lensing, AGN & stellar feedback, Hubble, Spitzer, Keck, Magellan, Herschel, Chandra. 

Lensed Galaxies:

Gravitationally lensed galaxies offer rare opportunities to study, at high spatial and spectral resolution, the inner workings of galaxies throughout cosmic history.   My research exploits these “gravitational telescopes” by obtaining diagnostic spectroscopy from Magellan and Keck, as well as images from Hubble, Spitzer, Herschel, and Chandra.  Recent papers:  Wuyts et al. 2014; Rigby et al. 2015Bordoloi et al. 2016.  NASA featured this science in the Hubble Space Telescope Year in Review.  My recent colloquium on lensed galaxies can be watched online.

I also pioneered diagnostic spectroscopy of lensed galaxies in the infrared. Our mid-IR IRS spectra of 23 Spitzer–selected lensed galaxies (Rigby et al. 2008) shows that the physical conditions of z~2.5 galaxies are much different than counterparts at z=0. We also pioneered the use of Paschen alpha to measure star formation rates in the distant universe (Papovich et al. 2009Finkelstein et al. 2011; Rujopakarn et al. 2012), a technique JWST will use frequently.

Active galactic nuclei (AGN):

We do not yet know what fraction of black hole accretion history took place in an obscured phase.   Though Compton-thick AGN are common at z=0, the long-sought-for population of obscured AGN in the distant universe remains undiscovered and uncharacterized.   New diagnostics (Diamond-Stanic et al. 2009Rigby et al. 2009; Teng et al. 2014; Teng et al. 2015) characterize the properties of obscured AGN.

Less obscured accretion onto central black holes is also fascinating.   I’ve measured the X-ray/mid-IR colors of AGN (Rigby et al. 2004 and Alonso-Herrero et al. 2004); the redshift distribution of optically–faint AGN (Rigby et al. 2005); demonstrated why half of X-ray–selected AGN lack optical AGN lines ( Rigby et al. 2006).

Cosmic distance scale:

I’m a member of the Carnegie Hubble Program, which is measuring the Hubble constant to a final systematic uncertainty of only 3% by observing Cepheid variable stars with the Spitzer Space Telescope.  We’ve published 13 papers to date.

Quasar absorption lines:

I used to work on quasar absorption lines, particularly weak MgII absorbers.  Papers:  Churchill et al. 1999; Charlton et al. 2000Charlton, Churchill, & Rigby 2000;  Rigby, Charlton, & Churchill 2002; Charlton et al. 2003Milutinovic et al. 2006.