Dr. Jane Rigby's Research

I'm an astronomer -- a Spitzer Fellow at the Carnegie Observatories in Pasadena, California.

My research interests include star-forming and star-bursting galaxies; luminous and ultra-luminous infrared galaxies and their evolution; active galactic nuclei (AGN), especially those that are extremely obscured ("Compton-thick"); gravitationally lensed galaxies as windows into the high-redshift universe; line diagnostics of AGN and star formation; the interplay between star-formation and black hole accretion; and multiwavelength (principally X-ray, optical, and infrared) astrophysics.

CV for Jane Rigby (pdf)

Publication List on ADS

Gravitationally Lensed Galaxies:

Gravitationally lensed galaxies offer rare opportunities to study, at high spatial and spectral resolution, the inner workings of galaxies out to high redshift. As such, I am constructing samples of gravitationally lensed galaxies at 0.5<z<3, then obtaining high--quality diagnostic spectroscopy.

For 23 Spitzer--selected galaxies, I have obtained mid-IR IRS spectra (Rigby et al. 2008), which surprisingly show that the AGN fraction is high, ~40%, and that z~2.5 galaxies have much brighter aromatic features (relative to total IR luminosity) than z=0 galaxies, which has important consequences for the calibration of star formation rate diagnostics.   With new spectra, we are measuring Paschen alpha and Brackett alpha fluxes for a subset of these galaxies: the first extinction--robust recombination line work at high redshift.

I have also begun a multi-semester campaign to obtain moderate--resolution optical spectroscopy with MAGE/Magellan for rest-UV--selected lensed galaxies.   These spectra probe stellar populations, metallicities, and outflows in typical star--forming galaxies at high redshift.

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.   New techniques ( Donley et al. 2005) find promising candidates by their non-stellar power-law slopes and X-ray weakness.   I have obtained deep Magellan spectra for 45 such candidates, finding unusually weak narrow line emission, suggesting very high extinction.

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 the National Radio Astronomy Observatory 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).