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GEORGE BECKER

My work with Wal Sargent centers on using quasar absorption lines to study the high-redshift intergalactic medium (IGM). We have obtained the first set of high-resolution spectra of quasars at z > 5 using Keck/HIRES. These data reveal an overabundance of low-ionization, metal-enriched absorption systems along a single sightline at z > 6, suggesting that large-scale variations in the ionization and/or enrichment state of the IGM may exists near the proposed epoch of reionization. I am characterizing the evolution of the Lyman-alpha forest over 4.5 < z < 6.4 in order to constrain variations in IGM ionization and density, extract IGM temperature information, and provide a framework in which to gauge the significance of the Gunn-Peterson troughs in the spectra of z > 6 quasars. I am also using a set of ~100 quasar spectra to measure the metagalactic UV background at z > 4 using the quasar proximity effect.

MILAN BOGOSAVLJEVIC

Before I started grad school, I remember reading about the fact that one can use the spectra of luminous quasars to investigate the physical conditions across the whole Universe - literally speaking! Most distant objects known to date are galaxies and quasars which lie at a cosmological redshift of z~6.5, meaning their light started its voyage towards us more than 12.8 billion years ago when the universe was only 13% of its present size. Spectra of quasars carry much information about the physical conditions of that era but they also cast light on everything that the photons encountered on their path to us. Unfortunately, distant quasars look very much like the billions of other stars in our astronomical images, and considerable effort is needed to find them.

During the first two years at Caltech, I have been involved in two surveys for the highest redshift quasars. One is called Palomar-Quest and it makes use of the Schmidt 48" telescope at Mt. Palomar and a camera containing 112 CCD chips to image large areas of sky every night. With this imaging data we will soon be able to find more of the most luminous quasars at z~6.

The second one was a small area "deep" survey where we obtained optical and near-infrared imaging at the Hale 200" telescope down to faint flux limits. We would select sources which have quasar-like colors and then observe them spectroscopically using the Keck telescope (Mauna Kea, Hawaii). In this way we have discovered a very faint quasar at z=5.7.

At present, astronomers know next to nothing about all but the brightest quasars at high redshifts and my thesis project will include discovering more faint quasars, constraining their numbers and distribution in luminosity. This information places important constraints on formation of galaxies and black holes which power quasar nuclei. In addition, in spectra of z>5 quasars we directly observe a signature of a Universe-wide reionization of intergalactic hydrogen, which is an important event in the evolution of the Universe as a whole and is linked to the appearance of the first sources of light - first stars and active galactic nuclei.

BRIAN CAMERON

Neutrons stars and black holes are the primary focus of my research. There are two major projects that will form the basis of my thesis. The first uses the newly commissioned laser guide star adaptive optics (LGS-AO) at the Keck II Telescope to measure proper motions of compact objects. The study will help constrain the formation mechanism of these objects and in some cases give us an idea of the type of environment in which the objects were formed. But more generally, I will be exploring the limits of ground-based astrometry with LGS-AO. This new system allows imaging at 3-4 times better than the Hubble Space Telescope in the near-infrared from the ground at a fraction of the cost. LGS-AO will be an inseparable of the next generation of extremely large ground-based observatories, and presents the primary technical challenge that must be solved before their construction. My goal is to better explore their theoretical and operational limitations.

The second major project I'm involved in is understanding compact objects in globular clusters. These dense environments lead to many stellar interactions and interesting binary evolution scenarios. One result are many recycled pulsating neutron stars that spin at millisecond periods. I use a combination of x-ray and radio signal processing techniques to study and search for these objects and also use them as probes of the cluster properties.

DANIEL GRIN

Axions, a solution to CP violation in the strong sector of the standard model, may also account for some fraction of the dark matter. Axions will be cold today and fall into cluster potential wells, and we might hope to see evidence of their existence through their decay to two photons. The photons produced may be optical, and by looking at high density regions, such as galaxy clusters, we may detect axions, or at the very least, limit their coupling to standard model particles. Currently, we've used data from the VIMOS IFU on the VLT to use the galaxy cluster A2390 to improve the last generation of constraints on the axion coupling strength by a factor of ~3. In the near future, we're hoping to improve these constraints and control all systematic effects, such as erroneous sky subtraction. I'm working on this project with Marc Kamionkowski, Jean-Paul Kneib (a professor at Marseilles), and Giovanni Covone (his former graduate student, now a professor in Naples). I've also begun work with Robert Caldwell (a visiting prof. from Dartmouth) to constrain models of the dark energy that treat general relativity as an effective field theory with a milli-eV cutoff by examining the achromatic effect this would have on gravitational lensing. By treating gravitational lensing as a tree-level scattering process in quantum gravity (analagous to Rutherford scattering in QED), we predict a dearth of high-deflection angle lenses which is not observed. By looking at lensed images of the QSO Q0957 using Chandra data, we are able to put a lower limit of 10^{-1} eV/c on the momentum cutoff in an effective theory of gravitation, ruling out the use of such a cutoff to explain the smallness of the cosmological constant. Finally, I'm trying to wrap up work with Michael Strauss (Princeton) on an undergraduate project I did, generating a sample of Lyman Limit absorption systems from the spectra of SDSS quasars.

MANSI KASLIWAL

I am a first year graduate student. My research interests are not well-defined and I have been exploring a few different wavelengths since I came to Caltech in June. Over ths summer, I completed a project on Ultraluminous Infrared Galaxies with scientists at Cornell University (my alma mater!) and the Spitzer Science Center. It was fun because we used photometric colors to estimate redshifts because z=1-2 is essentially a redshift desert in the mid-infrared and spectroscopic redshifts isn't quite an option. I have also been working on X-ray afterglows of Gamma Ray Bursts with Professor Shri Kulkarni's group. It's been fun trying to contribute a little piece to the jigsaw of broadband modeling of the afterglows that the group does (radio, optical infrared, x-ray and sometimes, ultra-violet). I also attended a Single Dish Radio Astronomy summer school at Arecibo and X-ray astronomy summer schoool at CFA this summer. I am planning to explore one more project before I decide on my thesis.

DAVID LAW

I am a third-year graduate student in Chuck Steidel's research group, interested primarily in studying the kinematics and formation history of high-redshift (z ~ 2-3) galaxies. I have recently been working on exploring the connections between morphological type (based on Hubble Space Telescope data), photometric data (from Spitzer Space Telescope and assorted ground-based telescopes), and rest-frame UV spectra (from the Keck Telescope) in an effort to understand the physical processes dominating in these systems. In the near future, I intend to integrate spatially resolved kinematic information obtained using OSIRIS, a near-IR integral field spectrograph recently built for use with the Keck laser adaptive optics system.

I am also actively interested in Galactic structure, particularly regarding the orbital dynamics of satellite galaxies tidally disrupting in the Galactic halo. In collaboration with researchers at the University of Virginia and Wesleyan University I have used numerical modelling of the disrupting Sagittarius dwarf spheroidal galaxy to constrain the size and shape of the Galactic dark halo, as well as the interaction history of Sagittarius and other nearby dwarf galaxies.

The majority of my time is spent writing computer code for morphological/kinematic analysis, analyzing Keck LRIS and OSIRIS spectra, and coding/performing numerous simulated observations of z~2 galaxies to better understand the selection biases and physical interpretation of our observational data. As a part of our observational program, I typically visit the Keck Observatory once every six months. In the remainder of my time I read, fence, swing dance, practice Tai Chi, quest for the perfect cup of tea, and on occasion go clubbing in Hollywood with friends.

FRANCIS O'DONOVAN

My thesis work centers on a search for transiting extrasolar planets with my advisor David Charbonneau, currently at the CfA at Harvard. I use a dedicated planet-search automated telescope, Sleuth, situated at Palomar Observatory (CA), to monitor stars for evidence of transits of extrasolar gas-giant planets. This planet finder is the third instrument in the Transatlantic Exoplanet Survey (TrES) network. I follow up TrES candidates using two larger-aperture telescopes at Palomar, Sherlock (10") and the 60" telescope, to rule out most forms of false positives resulting from eclisping binaries.

The ultimate goal of my thesis is to identify new transiting planets, such as TrES-1, since we can learn about the structure and formation of these planets by determining their radius and mass. I have also participated in the first direct detection of radiation from an extrasolar planet, namely the identification of infrared radiation from TrES-1 from observations of the secondary eclipse of the system. The study of extrasolar planets has changed how we look at our own solar system. By discovering new transiting exoplanets, I hope to further increase our ability to explain how planetary systems are formed and to lay the groundwork for upcoming missions such as Kepler and TPF which are poised to find extrasolar Earths.

The routine maintenance of Sleuth and Sherlock requires a lot of travel to Palomar. Since I have my own telescope to play with, though, I don't have to observe in remote locations very often. On the other hand, with my advisor in Boston, I visit the East coast quite a bit! When I'm not in transit or at work (it does occasionally happen!), I try to squeeze in some training, either for the LA marathon or for my Tang Soo Do class. I'm also on a mission to see all the sights in LA, and maybe spot a celebrity or two.

NAVEEN REDDY

I am currently a sixth year graduate student and an active member of a small research group led by my advisor, Chuck Steidel, which utilizes the unique optical capabilities of the Keck telescope and LRIS-B instrument to select z~2 galaxies based on their rest-frame UV (UGR) colors and perform followup spectroscopy. My research focuses primarily on studying three aspects of high redshift galaxies. The first is an examination of multi-wavelength measures of the bolometric luminosities, star formation rates (SFRs), and extinction of z~2 galaxies with the aim of understanding the global energetics of these high redshift galaxies and whether the SFR relations and extinction properties of local starbursts extend to galaxies at redshifts z>1. The second aspect is a detailed study of the overlap between optical, near-IR, and submillimeter selected galaxies at z~2 in order to understand the relationship of galaxies, and how galaxy properties change, as a function of selection criteria. I have also quantified the mutual contributions of these samples to the star formation rate density at z~2, taking into account sample overlap. The third aspect of my research is aimed at quantifying the completeness of the UV-selected sample of z~2 galaxies and constructing the UV luminosity function (LF). Comparison with UV LFs at z>3 and recent GALEX results at z=0 will provide us with a view of the evolution of the massive star formation in galaxies over almost the entire age of the Universe. In addition to the studies comprising my thesis, I am also involved in a number of other projects to investigate the SEDs, masses, kinematics, and morphologies of z~2 galaxies.

In my (slowly dwindling) free time, I enjoy spending time with friends and family, eating out, watching movies, reading, hiking, and playing tennis and the piano. I also enjoy travelling, photography, and big planes.

CATHY SLESNICK

I am a fifth year student working with Lynne Hillenbrand and John Carpenter. For my thesis project I am looking for new young low mass stars and brown dwarfs in the Taurus and Upper Scorpius star-forming regions. The survey is a combined imaging and spectroscopic effort. Most of the data has been taken at Palomar Observatory though we also have Spitzer data on some of the new brown dwarfs.

Prior to my thesis work I was involved in 2 projects, also with Lynne. In 1st year I worked on a project to derive the star formation history of h&Chi Persei and in 2nd year I worked on IR-spectrscopy of young brown dwarfs in the ONC.

Outside of the office I enjoy running, hiking and SCUBA.