Dr. Claire E. Murray

Galaxy evolution is driven by where, when and how stars form. In particular, the flow of material through the interstellar medium (ISM) -- from diffuse plasma to molecular, star-forming clouds -- is crucial. I use sensitive radio observations of neutral hydrogen (HI) and molecular gas to trace this flow in the Galactic and Magellanic ISM.

Scylla: a multi-headed attack on dust evolution and star formation

I am the PI of Scylla: a 500-orbit Hubble Space Telescope (HST) parallel imaging program (Cycles 27-29) to complement the HST Ultraviolet (UV) Legacy library of Young Stars as Essential Standards (ULLYSES) survey. We will: (1) map the extinction curve and dust grain properties at high resolution in a diverse range of interstellar conditions; (2) constrain the multi-dimensional structure of gas in the Large and Small Magellanic Clouds; and (3) measure the comprehensive star formation and chemical enrichment histories of nearby dwarf galaxies.

The nature and distribution of cold, optically-thick HI

Based on a large sample of 21 cm absorption lines, I found that optically-thick HI does not dominate the "dark" gas mass budget in the local ISM , rather it is a combination of intrinsic variations in dust grain emissivity and H2 undetected by standard tracers. Using machine learning techniques, I plan to characterize the nature of cold, optically-thick HI on large scales. Above is an all-Northern sky map of the cold neutral medium, derived from the first convolutional neural network applied to diffuse gas in the local ISM..

The temperature of the ISM

I am a leading member of "21-cm Spectral Line Observations of Neutral Gas with the VLA", the largest, most sensitive survey of Galactic HI absorption at the Karl G. Jansky Very Large Array (VLA). To detect the cold and warm neutral ISM simultaneously, I developed novel calibration strategies for improving 21cm sensitivity.

Unexpectedly warm neutral medium

I detected absorption by the warm neutral medium (WNM) with unexpectedly high excitation temperature , indicating that Lyman-alpha scattering is important for HI excitation, with consequences for disentangling astrophysical effects from HI signals throughout cosmic time.

Autonomous Gaussian Decomposition

I helped to develop an automatic method to decompose spectra into Gaussian functions using derivative spectroscopy and supervised machine learning. The code, GaussPy, is written in Python and is publicly available!

Connecting observations with simulations

Using AGD, I conducted detailed comparisons between 21-SPONGE and 3D numerical simulations, demonstrating how and where 21cm spectra recover "true" ISM conditions.

Mysterious Magellanic Molecules

I detected the first evidence for absorption by HCO+ in the Magellanic System -- a low-metallicity, dynamically complex neighbor to the Milky Way providing a important laboratory for molecule formation at high redshift.

Dr. Claire E. Murray