25 July 2008

Joseph Hennawi, University of Chicago, Berkeley

Quasars Probing Quasars: Understanding the Physics of Massive Galaxy Formation  

One of the most important problems in galaxy formation is understanding the physics which governs the observed bimodality in the galaxy population. Lower mass galaxies are gas rich and form a "blue cloud" in the color magnitude diagram, whereas more massive "red-and- dead" galaxies are gas poor and inhabit the red sequence. As a result, all galaxy formation models include some variant of feedback which acts to "quench" star formation in massive systems. Observing the formation epoch of red and dead galaxies will shed light on the physics behind this quenching. The strong clustering of luminous quasars at z ~ 2-3 indicates that they are indeed the progenitors of galaxies on the red sequence today. I will introduce a novel technique whereby a foreground quasar can be studied in absorption against a background quasar, resolving scales as small as 30kpc. This experiment reveals a rich absorption spectrum which contains a wealth of information about the physical conditions of gas in massive proto- galaxies. I will review absorption line modeling techniques and discuss the implications of these new observations for galaxy formation and feedback scenarios.