Research

My research focuses principally on topics related to supernovae (SNe), stellar feedback, star formation, and the interstellar medium (ISM). My work aims to bridge the gap between observations and theory by developing ways to compare meaningfully theoretical predictions with observational results. For this work, I use data from across the electromagnetic spectrum (radio, mm, infrared, optical, X-ray, and gamma ray) to have a complete view of the relevant processes.

In my work, I aim to set observational constraints using multiwavelength data (like the images shown above) to ascertain which processes dominate and their comparative role. For example, using these data, I mapped the pressures associated with the different feedback modes in the giant star-forming region 30 Doradus:

Left image: H-alpha image of 30 Doradus (Smith et al. 1999) with analyzed regions overplotted. Right four maps are pressure components across 30 Dor: (from left) Pdir, direct radiation pressure; PIR, dust-processed radiation pressure; PHII, the warm photoionized HII gas presure; Px, the hot shocked gas pressure. All 4 maps use the same color scale to enable visual comparison. Pdir dominates near the central star cluster, whereas PHII dominates at large radii by the HII region shell. Figure is adapted from Lopez et al. 2011.

Related to stellar death, I study the remnants of supernova explosions (SNRs) in the Milky Way and nearby galaxies. I have explored the morphological and spectral characteristics of SNRs to deduce the nature of the progenitors, the complexity of their environments, and their particle acceleration properties at shock fronts. As in my feedback work, I use data from the entire electromagnetic spectrum, with particular emphasis on SNRs at X-ray wavelengths, since the metals synthesized in the explosion are X-ray bright. 

One of the primary results from my PhD thesis was the discovery that SNRs “remember” their explosive origins, and their symmetry properties at several wavelengths reflect the geometry of their originating explosions (see the Figure below).

Figure demonstrating my symmetry analyses: I used a multipole expansion technique (the power-ratio method) to find the quadrupole power ratio P2/P0 (a measure of ellipticity/elongation) and the octupole power ratio P3/P0 (which quantifies mirror asymmetry) of the SNRs’ X-ray images (left) and mid-IR images (middle). Type Ia SNRs are the red points, and core-collapse SNRs are the blue. The Type Ia SNRs separate naturally from the core-collapse SNRs. Right: Two-color images (with the IR in red and X-ray in blue) of the SNRs in the power ratio plots. Figures are adapted from Lopez et al. 2011 and Peters et al. 2013.

Broadly, my research is related to stellar birth and death. Regarding stellar birth, I am principally interested in the star formation process and how it is regulated. Stellar feedback - the injection of energy and momentum by stars - is thought to be the culprit, and it takes many forms: e.g., stellar radiation, photoionization, stellar winds, supernovae, protostellar outflows/jets, and cosmic rays. These feedback modes occur at the small scales of individual stars, yet they shape the ISM over whole galaxies. Thus, despite the fundamental importance of feedback, its role in the dynamics of gas from small to large scales is highly uncertain.

Statistical comparison between sources revealed two SNRs which were anomalous compared to the others (see images on the right). Both are the most elliptical of all local SNRs, and their abundances are consistent with predicted chemical yields of jet-driven core-collapse SNe. These two SNRs are the first local analogues of gamma-ray bursts to be discovered.

Multiwavelength images of two extremely elliptical SNRs thought to be from jet-driven explosions (Lopez et al. 2013, 2014), similar to the explosions that produce gamma-ray bursts. Left: SNR W49B, with X-rays in blue, IR in yellow, and radio in purple. Right: SNR 0104-72.3, with X-rays in purple and IR in green. Images are from NASA/Chandra press releases.