RESEARCH
My research involves studying the evolution of massive galaxies by analyzing:
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1)the stellar populations and star formation histories of high-redshift galaxies directly through deep infrared imaging, and
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2)the evolution of the gas and dust content of galaxies and the intergalactic medium throughout cosmic history, as revealed by absorption in the spectra of background quasars.
Selected Publications:
“Large-SCale Star Formation-Driven Outflows at 1<z<2 in the 3D-HST Survey”
Lundgren et al. 2012b
ApJ, Submitted (arxiv.org:1207.7077)
“Tracing the Mass Growth and Star Formation Rate Evolution of Massive Galaxies from z=6 to z=1 in the Hubble Ultra-Deep Field”
Lundgren et al. 2012a
ApJ, Submitted
“The Dark Matter Haloes and host galaxies of MgII
Lundgren et al. 2011
MNRAS, vol 417, p.304
Quasars are galaxies that have actively-accreting central supermassive black holes. This activity in the galactic nucleus produces luminosities 100-1000 times greater than normal galaxies, allowing quasars to be observed from the distant Universe.
Absorption lines in quasar spectra probe gas and dust from galaxies and the intergalactic medium along the sight. A cartoon depiction of absorption lines in the spectrum of a high-redshift quasar is shown at right. The colorful simulated image of large-scale structure was produced by John Healy (Durham University). Beneath the image is an example of how absorption from clouds and filaments of neutral Hydrogen might appear in a quasar spectrum. At wavelengths greater than the quasar’s rest-frame Lyman-alpha emission, intervening absorption features from metals (Mg, Fe, C, etc.,) can be more clearly seen.
probing faint galaxies with
Quasar absorption lines
Galaxies in the Hubble Ultra-deep Field
The highly-successful recent servicing of the Hubble Space Telescope has enabled the deepest-ever views of the high-redshift Universe using the newly installed WFC3/IR camera. I am currently working with Pieter van Dokkum and collaborators to identify and analyze high-redshift galaxies with new imaging of the Hubble Ultra-Deep Field. ...more to come!
Although it is well-established that intervening absorption lines probe gas and dust along quasar lines of sight to high redshift, the exact origin of the absorption is not yet well understood. While some absorbers may be caused by virialized gas in extended galaxy haloes, others may be tracers of super-winds from supernovae or starburst activity. Comparing the spatial distributions of quasar absorption lines to those of better-understood observable galaxies allows us to gain more information about their environments and their relationship to large scale structure in the Universe.
My PhD thesis included an analysis of the real-space clustering of intervening MgII absorption line systems identified in the Sloan Digital Sky Survey. We were able to confirm with high precision the results of Bouche et al. 2006, which showed that weaker (W<1.4A) Mg II absorption line features are significantly more clustered than their stronger (W>1.4A) counterparts, challenging the classical picture that the equivalent width of the gas absorption increases with the dark matter halo mass of the absorber’s host galaxy. This adds to mounting evidence that the strongest metal lines in quasar spectra trace outflows from actively star-forming galaxies.