Scientific Interests:
Very high-energy gamma-ray and neutrino astrophysics
Dark Matter
Particle Physics
Recent Highlights:
- Fermi Detects Gamma Rays from the Binary Source Cygnus X-3. Cygnus X-3 is a rather famous X-ray object that was "discovered" as a soure of TeV and even PeV gamma rays in the 1970's and the 1980's. In fact, these discoveries accelerated the growth of the field of VHE astronomy. In the 1990's and 2000's, Cygnus X-3 was not firmly detected by any gamam-ray telescope,leading to speculation that the original results were statistical fluctations. Now, recent observations by the Large Area Telescope (LAT) of the Fermi Gamma-ray Space Telescope show a clear detection of Cygnus X-3, where the gamma-ray signal is correlated with the 4.8 hour orbital period of the binary system. Contributing to the LAT analysis were two UCLA undergraduates: Nickolas McColl and Laura Marchand and this work led to a paper published in the journal Science.
- VERITAS makes the first detection of gamma rays from a starburst galaxy (M82). This discovery provides important clues towards understanding the origins of cosmic rays. Read the journal article in Nature. Popular articles can be found at 7th Space, at Astronomy.com, in the Cern Courier, at the National Science Foundation Website, and in the UCLA Today news.
- VERITAS Discovers VHE gamma rays from a powerful blazar 1ES 0502+675. This source is one of the most distant objects known to emit TeV gamma rays. Since TeV photons are expected to be absorbed by intergalactic radiation fields, this discovery is surprising because it implies that the Universe is more transparent at these energies than expected. Indeed, there are speculations that some sort of new physics may be involved. The discovery was announced in an Astronomical Telegram. Rachel Courtland wrote a nice article in the New Scientist on the possible existence of axion-like particles to explain the observations.
Experimental Program:
Very Energetic Radiation
Imaging Telescope Array System (VERITAS)
VERITAS is state-of-the-art observatory of very high-energy gamma
rays in the energy range between 50 GeV and 50 TeV.
VERITAS consists of four large (12m diameter) reflectors, each viewed
by a camera of 500 photomultiplier tubes. Each tube is read out by a
500 MHz Flash-ADC. The VERITAS construction took place between 2003
and 2007, with the full four-telescope array starting operations in
September 2007. VERITAS has produced a wide variety of scientific results
based on the first three years of operation (2007-10).
UCLA has primary responsibility for the
Level 1 Trigger, the Level 3 (multi-Telescope)
Trigger, and the online data storage and archiving facility.
Scientists at UCLA are involved in a broad range of scientic
topics, including Galactic sources, extragalactic sources,
dark matter, and astroparticle physics.
General AntiParticle Spectrometer
(GAPS) Experiment
GAPS is a proposed balloon-borne experiment to search for anti-deuterons in the
cosmic rays. Anti-deuterons at energies below 1 GeV are a unique signature
of annihilating weakly-interacting dark matter. GAPS will consist of a large
array of Si(Li) detectors surrounded by a time of flight (ToF) detector. A prototype
instrument is being built for balloon flight in mid 2011.
UCLA is responsible for elements of the time-of-flight, trigger, and electronic systems.
Fermi Gamma-ray Space
Telescope (FGST)
Fermi is a high-energy gamma-ray satellite launched by NASA on
June 11, 2008.
The Large Area Telescope (LAT) on Fermi has an
energy range between 10 MeV and 300 GeV. The LAT consists of silicon strip detectors
for tracking and a CsI calorimeter for energy measurement.
Fermi is fully operational with many exciting results so far and more to come.
Advanced Gamma-ray Imaging
System (AGIS), now Cherenkov Telescope Array (CTA)
CTA is a future, major gamma-ray observatory that would greatly expand
our understanding of the high-energy and very high-energy universe.
Currently in an R&D phase, CTA could consist of ~50 atmospheric
Cherenkov telescopes spread out over an area of ~1 sq-km. CTA would be
a logical follow-up to the VERITAS and Fermi missions that are currently
operational.
Solar Tower Atmospheric
Cherenkov Effect Experiment (STACEE)
STACEE used the atmospheric Cherenkov technique to detect gamma rays
at energies between 50 and 500 GeV. Until recently, this energy
range was not explored by any other experiment. In 1999, a early version
of STACEE detected ~4,800 high-energy gamma rays from the Crab Nebula,
and in 2001, rapid flares of gamma rays were detected from the blazar
Markarian 421. Operating between 2001 and 2007, STACEE carried out
a comprehensive program of observations of galactic and extragalactic
sources. In 2006, STACEE reported spectral measurements of the Crab Nebula
and Markarian 421 at energies between 150 GeV and 1500 GeV. In 2009,
STACEE reported results from observations of 23 gamma-ray bursts, the pulsar
PSR 1951+32, and the Draco dwarf galaxy. UCLA was the lead university on STACEE.
Research Group (as of January 2011):
Pratik Majumdar, Staff Research Associate, pratik-at-astro.ucla.edu
Isaac Mognet, Research Associate, mognet-at-astro.ucla.edu
Jeff Zweerink, Asst. Research Physicist, zweerink-at-astro.ucla.edu
Alexis Popkow, Graduate Student, agpopkow-at-sbcglobal.net
Tracy Zhang, Graduate Student, satrfx-at-astro.ucla.edu
Julie Curtis, Undergraduate
Brandon Maupin, Undergraduate
Alumni:
Post-docs and students who have worked with me (their last known location and position):
Former Post-Docs (chronological)
| Corbin Covault | Case Western Reserve University, Assoc. Professor |
| Kevin Green | Castelebridge, LLC |
| Brian Fick | Michigan Technical University, Professor |
| Lucy Fortson | University of Minnesota, Assoc. Professor |
| Mark Chantell | University of Chicago, Staff |
| Zoa Conner | George Washington University |
| Jim Hinton | University of Leicester, Professor |
| Jeff Zweerink | UCLA, Asst. Research Physicist (part-time) |
| Amanda Weinstein | Iowa State University, Asst. Professor |
Former Graduate Students (chronological)
| Joseph Fowler | Princeton University, Asst. Professor |
| Scott Oser | University of British Columbia, Assoc. Professor and Canada Research Chair |
| Jennifer Carson | Claremont Colleges, Instructor |
| Alex Jarvis | Disney Productions, Analyst |
| Ozlem Celik | Goddard Space Flight Center, Postdoctoral Researcher |
| Ken Chow | (Financial sector) |
Former Undergraduates (chronological, from 1990-2010)
| Peter Burke | University of California, Irvine, Assoc. Professor |
| Sunil Golwala | California Inst. of Technology, Professor |
| Peter Rauske | University of Chicago, Graduate Student |
| Zandra Wells | Lawrence Family Practice, MD |
| Hugh Kim | Tiger Asia Management, Director |
| Matthew Pritchard | Cornell University, Assoc. Professor |
| Anthony Miceli | University of Washington, Graduate Student |
| Dan Schuette | Lincoln Laboratories, M.I.T., Scientist |
| Eugene Chae | University of Chicago (last known location) |
| Nicolas Rassat | Ecole Polytechnique, Graduate Student |
| Susan Channels | Costa Mesa, CA, CPA |
| Jason Minamora | California Inst. of Technology, Graduate Student |
| Katy Tschann-Grimm | SUNY-Stony Brook, Graduate Student |
| Thomas Fishman | Columbia University, Graduate Student |
| Jeffrey Dunworth | University of California, San Diego, Graduate Student |
| William Gignac | University of Michigan, Graduate Student |
| Cyrus Rustomji | University of California, San Diego, Graduate Student |
| Jennifer Helsby | University of Chicago, Graduate Student |
| Jennifer Sierchio | University of Arizona, Undergraduate Student |
| Daniel Margala | University of California, Irvine, Graduate Student |
| Nickolas McColl | University of California, Santa Barbara, Graduate Student |
| Laura Marchand | (Private industry) |
| Jacob Schwartz | UCLA Undergraduate |
| Brandon Maupin | UCLA Undergraduate |
| Richie Nagi | UCLA Undergraduate |
| Sabrina Hong | UCLA Undergraduate |
Support:
My current research is supported by the National Science Foundation, the Department of Energy, NASA, and UCLA. I have also received support from the Sloan Foundation and the Grainger Foundation.