Research in Extragalactic Astronomy

Extragalactic astronomy and cosmology have long been particular research specialties of the UCSC faculty. Only a few particular projects are mentioned here.



Enabled in large part by the great sensitivity of the Keck Telescopes, UCSC astronomers have pursued a broad range of extragalactic astronomy. Some questions are on relatively small scales: What can the kinematics, structure, and stellar content of dwarf elliptical galaxies tell us about galaxy formation? Asked the thesis of recent PhD graduate Marla Geha (now a Hubble Fellow). Other inquiries address the very large and luminous, such as Joe Miller's investigation of the central energy sources in active galaxies. And attention must be paid to the stuff between galaxies, as with Jason Prochaska's work on the enrichment of intergalactic gas near distant galaxies.

Promising new techniques are also being explored. How can gamma-ray bursts be used as tracers of star formation, for example, or as backlights to study the intergalactic medium? How can adaptive optics be used to study the host galaxies of quasars?


The Deep Extragalactic Evolutionary Probe (DEEP) is a major collaboration between UCSC, UCB, UH Manoa, Johns Hopkins, and Caltech to conduct a large scale survey of distant galaxies using the Keck Telescopes and HST. The core UCSC participants are Professors Sandy Faber (co-PI), Raja GuhaThakurta, Garth Illingworth, and David Koo.

The first phase, DEEP I, is now completed. Using the Keck Low-Resolution Imaging Spectrometer (LRIS) spectrograph, it concentrated on three fields in the sky (SA 68, HDF, and Groth strip) and studied all galaxies primarily in the redshift range 0.3-1.3.

The second phase, DEEP II, is now underway at Keck (120 nights budgeted), using the new Deep Imaging Multi-Object Spectrograph (DEIMOS). DEIMOS is the largest spectroscopic detector of its type ever made, capable of observing 140 galaxies at a time. The goal of DEEP II is to measure redshifts of more than 50,000 galaxies brighter than I-band magnitude 23.5, and 5000 additional galaxies in a more sensitive survey that goes one magnitude deeper.

The goals of this immense project include studies of evolution of galaxies and structure over time. Questions to be answered include the connection between dark matter and luminous galaxies, the role of dark energy and accelerating expansion, and the way that galaxies formed and developed. DEEP complements both the shallower, wider-area Sloan Digital Sky Survey (SDSS)and the very early snapshot of the Universe frozen in the cosmic microwave background radiation (CMBR) taken with the Wilkinson Microwave Anisotropy Probe (WMAP). Collectively, the SDSS, DEEP, and WMAP studies will reveal the creation of the Universe we view today.


Theoretical extragalactic astrophysics and cosmology include many different investigations at UCSC. At the low mass end, Doug Lin and his collaborators have studied star format in dwarf spheroidal galaxies, thought to be the building blocks of all larger galactic entities.

The entwined histories of star formation and black hole formation have been continuing themes in the work of Piero Madau, exploring how both fusion energy in stars and accretion energy near black holes have developed over the history of the Universe. Either process, or both, may have been important at early epochs when the intergalactic medium was reionized, so they are crucial to understanding the thermodynamic history of the intergalactic and intra-cluster mediums. The growth of supermassive black holes is potentially a tracer of the merger activity of galaxies, connecting theories for the growth of galactic structures to observations of the redshift and luminosity distribution of active galaxies where black hole accretion energy dominates. The physical process that communicates energy released by supermassive black holes to the surrounding gas, shutting down star formation in galaxies and clusters, is an another area of intense research at UCSC.

An active group in the physics department works on particle cosmology and the connection of astrophysics to string theory and other ideas in modern high energy physics. Frequent interactions between members of the two departments (who share floors in the same building) allow extensive collaborative work between physicists and both theoretical and observational astrophysicists.

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