Extragalactic Astronomy and Cosmology @ UCSC

Extragalactic astronomy and cosmology represent UCSC's efforts to understand the structure and evolution of the universe on the largest scales, including the formation and dynamics of galaxies, clusters and superclusters, the large-scale-structure of the universe, and the evolution of the universe from the earliest times.

The subjects have long been particular research specialties of the UCSC faculty. We focus on a few aspects of research here to give an illustration UCSC's activities.

 

Extragalactic Astronomy

Enabled in large part by the great sensitivity of the Keck Telescopes, UCSC astronomers have pursued a broad range of extragalactic astronomy, from the kinematics of dwarf elliptical galaxies to the distribution of galaxies and quasars -- and the stuff in between them -- on the largest scales.  

As an example, 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.

 

Galaxy formation and evolution

Complementing the observational effort of DEEP and other surveys is an intense effort led by Joel Primack, Piero Madau, Anthony Aguirre and others, toward theoretically understanding the formation of galaxies through detailed numerical simulations of large swathes of the universe, and comprehensive models of galaxy formation enfolding the myriad physical processes involved.  Primack, Madau, and collaborators specialize in state of the art massively parallel numerical simulations of how dark matter clumps and organizes into the backbone of cosmic structure, on scales from tiny proto-galaxies to stucture on the scale of the observable universe.  Modeling by Primack, Madau and Aguirre works to understand how galaxies connect with the intergalactic medium form which they form, and to understand the origin of the first stars and galaxies.  As well, these models produce a wid array of predictions for the types, luminosities, morphologies, masses, and abundances of galaxies, which can be compared in detail to observational surveys.

 

The intergalactic medium

In-between the galaxies lies the intergalactic medium (IGM), composed mostly of hyrogen and helium gas along with an intriguing sprinkling of heavier elements such as carbon, silicon and oxygen.  UCSC has a strong effort (see the PISGM group) led by Jason X. Prochaska, Madau, Aguirre and others to understand the complex interplay between the and galaxies.  How does the IGM feed galaxies?  How do galaxies feed back upon the IGM with energy, chemical enrichment, and radation?  What can the IGM tell us about the cosmic history of galaxy and star formation?  These consitute some of the big open questions in physical cosmology that UCSC researchers are making significant headway in answering.

 

Dark Matter

While cosmologists are nearly certain that most of the matter of the universe is a 'dark' type that gravitates but is otherwise invisible, the nature of this dark matter remains a mystery.  UCSC has one of the world's strongest groups seeking to elucidate dark matter, connecting the FERMI mission, the high-energy group working on the LHC particle physics experiment, and the dark matter cosmology effort at UCSC.  Tying these groups together are researchers such as Stefano Profumo, Michael Dine, and Tom Banks from the particle physics group, Joel Primack, Piero Madau and Anthony Aguirre in cosmology, and Steve Ritz, Tesla Jeltema, and Robert Johnson and other SCIPP personnel working on the Large Hadron Collider, the Fermi Space Telescope and other experiments that may probe dark matter.

 

Dark Energy

A profound mystery in modern cosmology is the underlying cause of the accelerated expansion of the universe, which may result from an additional component of the universe termed dark energy or from modifications to general relativity on large scales.  UCSC faculty use multiwavelength observations and numerical simulations to shed light on this "dark" component of the universe.  In particular, Rebecca Bernstein and Tesla Jeltema are members of the Dark Energy Survey (DES) which achieved first light in September 2012.  Robert Johnson, Tesla Jeltema, and Connie Rockosi will also be involved in preparation work for the next generation large-area survey LSST .

 

The Early Universe

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. Tom Banks and Michael Dine explore cosmology and its connection to string theory.  Stefano Profumo specializes in the cosmological genesis of dark and other matter, and early-universe processes that may give rise to gravitational waves.  Anthony Aguirre probes the physics of cosmological 'inflation', a phase believed by many cosmologist to occur in the very early universe, which may have given rise to all of the observable universe, and perhaps many more such regions like it!