JUDY CHENG

    RESEARCH
    • SEGUE STELLAR LIBRARY, September 2007 - present
      I am working with Professor Connie Rockosi at UC Santa Cruz to compile a library of stellar spectra in the Sloan Extension for Galactic Understand and Exploration (SEGUE), part of the Sloan Digital Sky Survey (SDSS). The data from SEGUE, which include multi-band photometry and medium resolution spectra of over 100,000 stars, are an excellent resource for a search of rare giant stars. Giant stars are especially important because they contribute significantly to light that we observe from distant galaxies. However, they are relatively rare because the of the short duration of the giant phase in stellar evolution. Some example spectra and preliminary results are shown here.
    • RED SEQUENCE MORPHOLOGIES, November 2006 - present
      I am currently working with Professor Sandra Faber and graduate student Genevieve Graves at UC Santa Cruz to study the properties of red galaxies. I am trying to determine a method of classifying red galaxies imaged by the Sloan Digital Sky Survey (SDSS) using a combination of photometric quantities measured by SDSS and light profile parameters measured by Galaxy IMage 2D (GIM2D), written by Luc Simard. Of particular interest is a method of distinguishing between red elliptical galaxies and red disk galaxies. These two types are likely to have followed different evolutionary tracks, and classifying a large samples of red galaxies is the first step toward understanding the nature of these differences. I gave a talk about this project in January 2008; see the presentation here.
    • COMETS IN THE ALPHA CENTAURI SYSTEM, September 2006 - June 2006
      I worked with Valentino Gonzalez and Greg Laughlin on understanding the delivery of volatiles into the alpha Centauri binary system. Some theories posit that water was delivered to the Earth by long period comets that collided with the planet earlier in its history. We assume that terrestrial planets orbit the two stars (see the work done by Javiera Guedes and Erica Davis) and that the binary system is surrounded by its own analogous cloud of comets. The alpha Centauri system is especially interesting because of the presence of a third star, Proxima, which is currently located about 15000 AU from the binary. We ran a number of N-body simulations to examine Proxima's role in perturbing the orbits of these comets inward toward the binary system. For more information, some results, and some really great movies, click here.
    • THE POST-AGB STAR/PRE-PLANETARY NEBULAE TRANSITION, June 2005 - August 2005
      I worked with Mark Morris of UCLA as part of the Research Experiences for Undergraduates (REU) program run by the National Science Foundation (NSF). I studied two pre-planetary nebulae through the analysis of images from the telescopes at The Keck Observatory. By comparing the Keck images with images form the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope, we found evidence that one of the objects, AFGL 3068, is a binary pair. While the Keck images showed two point sources, this was not enough evidence to show that the object is a binary pair. The ACS image displayed a large spiral structure that is characteristic of a binary pair in which one star is losing mass rapidly. The expected separation of the two stars (which was calculated using the expansion velocity of the spiral structure and the distance between the crests) was consistent with the separation between the two sources in the Keck image. The paper I wrote at the end of that summer is located here: High-Resolution imaging of Objects in the Post-AGB to Planetary Nebula Transition. The results from this research were also presented at the International Astronomical Union Symposium 234 in April 2006: A Binary-Driven Pinwheel Outflow from the Extreme Carbon Star, AFGL3068 (abstract #72).
    • CYGNUS LOOP SUPERNOVA REMNANT, June 2004 - May 2006
      I worked with William P. Blair and Ravi Sankrit on data from the Far Ultraviolet Spectroscopic Explorer (FUSE). We analyzed emission line spectra from a portion of the Cygnus Loop Supernova Remnant known as the XA region. Six target locations were chosen from this region to analyze the kinematics and elemental abundances of the interstellar medium surrounding the remnant. Spatial variations were also studied. The data and some preliminary conclusions were presented at the American Astronomical Society meeting in January 2004: FUSE Observations of the XA Region in the Cygnus Loop SNR. The results were published in the Astronomical Journal in May 2007: Far Ultraviolet Spectroscopic Explorer Spectroscopy of the XA Region in the Cygnus Loop Supernova Remnant.
    TEACHING
    • Astronomy 2: Overview of the Universe, Joe Miller, Spring 2007
    • Astronomy 2: Overview of the Universe, Adriane Steinacker, Winter 2007
    • Astronomy 2: Overview of the Universe, Steve Vogt, Fall 2006