Laura Lopez -- University of California Santa Cruz (UCSC): Research

My PhD thesis regards two separate stages of the stellar life cycle: stellar birth and stellar death. My advisors on these topics are Professor Enrico Ramirez-Ruiz (UCSC), Professor Jason Xavier Prochaska (UCSC), Professor Mark Krumholz (UCSC), and Professor Alberto Bolatto (UMd). I expect to finish this work and to defend my thesis in the Spring of 2011.

In the area of star formation, I am studying the energy injection and momentum deposition mechanisms of HII regions in the Large Magellanic Cloud (LMC). Specifically, I am analyzing images of roughly two-hundred HII regions at many different wavelengths (radio, infrared, optical, UV, and X-ray) to assess the dominant pressure sources that control the dynamics of HII regions, and thus are thought to regulate the efficiency and timescale of the star-formation process. The proximity, low obscuration, active star formation, and copious archived imaging of the LMC makes it an ideal candidate for a systematic comparison of how feedback changes as a function of age, environment, metallicity, and size of HII regions. This work is the first to probe multiple modes of feedback observationally in a large sample.

With regard to stellar death, I have developed new methods to quantify the X-ray morphology of young supernova remnants (SNRs) observed with the Chandra X-ray Telescope. By applying three techniques (a power-ratio/multipole expansion method, two-point correlation, and wavelet-transform analysis) to archival ACIS observations of galactic and extragalactic SNRs, we can assess properties like chemical segregation and mixing, distribution asymmetries, and sub-structure. Detailed comparison between sources provides insights regarding the nature of the explosions, the effects of heating and environments, and particle acceleration properties. We were awarded an archival Chandra grant to support this work.

Related papers:

Lopez, L. A., Ramirez-Ruiz, E., Badenes, C., Huppenkothen, D., Jeltema, T. E., Pooley, D. A. "Typing Supernova Remnants Using X-ray Line Emission Morphologies", 2009, ApJL, 706, L106 ADS
Lopez, L. A., Ramirez-Ruiz, E., Pooley, D. A., Jeltema, T. E. "Tools to Dissect Supernova Remnants Observed with Chandra: Methods and Application to the Galactic Remnant W49B", 2009, ApJ, 691, 875: ADS

Four additional papers of my thesis are in the pipeline currently to be submitted over the next year (before I apply for jobs): one probing the morphology of X-ray line emission in Galactic and LMC SNRs; one studying SNR particle acceleration sites from the X-ray and radio synchrotron filament sizes; one on feedback mechanisms within 30 Doradus; one on feedback mechanisms across all two-hundred LMC HII regions.

I also work with Professor Niel Brandt of the PSU Astronomy & Astrophysics Department on X-ray observations of high-redshift radio-loud quasars (RLQs). We observed twelve RLQs at z=3.5-4.7 with Chandra ACIS to investigate X-ray jets and intrinsic X-ray absorption in high-z RLQs. A search for extended X-ray emission associated with kpc-scale radio jets revealed only limited evidence for X-ray extension in our sample, evidence against an X-ray jet origin of inverse Compton scattering of CMB photons. We have obtained Very Large Array (VLA) Radio Telescope images to explore further the nature of broad-band jets at high redshift.