Dr. Jane Rigby's Research

I'm an astrophysicist at the NASA Goddard Space Flight Center, outside of Washington DC.

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.

Gravitationally 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.

I'm obtaining high-quality rest-UV and rest-optical spectra with the Magellan and Keck telescopes, as well as imagery from Hubble, Spitzer, Herschel, and Chandra, in collaboration with M. Gladders, K. Sharon, and E. Wuyts (U. of Chicago) (Rigby et al. 2011; Sharon et al. 2011 submitted to ApJ; Wuyts et al. 2011 submitted to ApJ.) This spectroscopic survey is characterizing stellar populations, abundances, physical conditions, and outflows in star-forming galaxies at the epoch of peak star formation.

I have 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 z~2.5 galaxies have much brighter aromatic features (relative to total IR luminosity) than z=0 galaxies, which suggests that the physical conditions in star-forming galaxies have evolved dramatically. We also pioneered the use of Paschen alpha to measure star formation rates in the distant universe (Papovich et al. 2009), a technique that JWST will use frequently.

Highly-Obscured AGN:

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 highly--obscured AGN remains undiscovered and uncharacterized in the distant universe.   We are using new techniques ( Donley et al. 2005) to find these AGN by their non-stellar power-law slopes and X-ray weakness, and are using new diagnostics (Diamond-Stanic et al. 2009; Rigby et al. 2009) characterize the properties of obscured AGN.

In the local universe, I am also investigating how obscured AGN reprocess their absorbed optical/UV/X-ray energy into the infrared. For a sample of 9 Compton--thick AGN in host galaxies with low star formation rates, and a control sample, I've obtained Spitzer 5--160 micron SEDs and spectra, as well as duPont and Bok 2.3m optical spectra.   This extraordinary spectral coverage offers new tests of narrow line region physics, and also direct measures of the obscuring geometry.

NGC 1068 in X-rays (Chandra)

Diagnostics of the Initial Mass Function:

I defended my Ph.D. thesis, "X-ray and Infrared Diagnostics of Star-forming and Accretion Activity in Galaxies" on 8 March 2006.  My thesis advisor was Professor George Rieke.

For the first part of my thesis (Rigby & Rieke 2004), I tackled an old question: what is the stellar initial mass function (IMF) of starbursts?  To answer, I tested near- and mid-IR diagnostics of the IMF of starburst galaxies.  I found that the ionizing fields of nearby starbursts are surprisingly soft, indicating either that the highest-mass stars are either missing (a truncated IMF) or are heavily enshrouded for much of their main-sequence lifetimes.

The IR properties of X-ray selected AGN:

In the second half of my thesis, I examined the Spitzer properties of AGN in cosmological deep fields (primarily CDF-S, but also Lockman Hole and Extended Groth Strip), focusing on:  

• 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);
• why half of X-ray--selected AGN lack optical AGN lines ( Rigby et al. 2006);
• finding highly-obscured AGN ( Donley et al. 2005 and Alonso-Hererro et al. 2006).

CDF-S at 24um

Other Research at Steward:

• I wrote a white paper showing how to integrate the IRIS 10-20 um spectrometer with the MMT adaptive optics system --- low-speed, low-order corrections are sufficient.
• I worked with grad student Kris Eriksen to understand the ultraluminous x-ray source in Ho IX, using the MMT, VATT, and Cloudy models (Eriksen et al., in preparation).
• I tested whether grad student Andy Marble has indeed found the widest--separation pair of lensed QSO images.
• George Rieke and I searched with the 90" Bok telescope for graviationally-lensed arcs in X-ray--selected clusters of galaxies.

Past Research at Penn State:

For 3 years (as an undergrad) I was a member of the Penn State Quasar Absorption Line Group.   We discovered a unique kind of object: weak MgII absorbers.   These gas clouds are probably not associated with bright galaxies, yet some have solar metallicities.  How were these clouds enriched? Why are they so numerous?   And why do they lack luminous counterparts?   The discovery paper is  Churchill et al. 1999, and we model the sources with Cloudy in  Rigby, Charlton, and Churchill 2002.   See also Charlton et al. 2003 and Charlton et al. 2000.   We continued this collaboration to find analogous absorption at low redshift (Milutinovic et al. 2006).

I also wrote readout and control software for the JCAM near-infrared spectrograph on the 9 m Hobby-Eberly Telescope.

Past Research at NRAO:

In 1998, I was a Summer Student at NRAO in Socorro, NM.  With K. Anantharamaiah, I searched for radio recombination lines (RRLs) in Seyfert galaxy Mrk 231 and elliptical galaxy NGC 1052 (Omar et al. 2002).