The Epoch of Reionization (EoR) is the period in the universe's history during which the hydrogen in the intergalactic medium (IGM) was ionized by the first luminous sources. Reionization is closely linked to the process of structure formation in the universe, and studying this era is key to bridging the gap between our observations of the cosmic microwave background and the universe we know today.
One approach to probing the EoR is via the first ionizing sources. Specifically, my work focused on Lyman alpha (Lyα) emission from galaxies. Lyα is highly susceptible to attenuation by neutral hydrogen, so it can be used to infer information about the quantity and distribution of neutral hydrogen in the IGM during the EoR. I worked with Charlotte Mason at the Center for Astrophysics | Harvard & Smithsonian to implement scatter in the galaxy UV luminosity to dark matter halo mass relation to improve our model of Lyα visibility during reionization, and inferred the fraction of neutral hydrogen in the IGM using this model and current observations of galaxies.
Another method of studying reionization comes directly from the neutral hydrogen in the IGM. Neutral hydrogen emits radiation with a wavelength of 21 centimeters during its spin-flip transition, and this spectral line is a promising probe of the EoR. However, actually detecting the line requires overcoming significant observational challenges. These effects can be environmental (e.g. bright radio foregrounds from galactic and extragalactic sources, radio frequency interference (RFI), and atmospheric attenuation), or instrumental (e.g. calibration errors).
The Hydrogen Epoch of Reionization Array (HERA) is a radio interferometer currently under construction in South Africa designed to probe the large-scale structure during reionization via power spectral measurements of 21 cm line. I have used HERA commissioning data to examine the effects of RFI and calibration systematics on measurements of the 21 cm power spectrum from the EoR, and I am currently interested in modeling the effects of RFI on astrophysical parameter estimation from 21 cm EoR measurements.
I imaged the nearby edge-on galaxy NGC 4565 with data from the Low Frequency Array (LOFAR) at 144 MHz. Using this low frequency image, I created vertical intensity and spectral index profiles and characterized the cosmic ray transport mechanism in the galaxy as being primarily diffusive, rather than advective. This has implications for galactic outflows and the transfer of energy and heavy elements between the interstellar, circumgalactic, and intergalactic media.
See the paper here.
I contributed code to the SImulator of GAlaxy Millimetre/submillimetre Emission (SÍGAME) module, a code to post-process the results of cosmological galaxy formation simulations to extract the far-infrared line emission of galaxies. I primarily added analysis capabilities, including calculating radial profiles of a given far-infrared line and maps of line emission ratios (e.g., [CII]/[NII]). I also worked towards validation efforts, compiling observations of far-infrared lines at both high and low redshift to compare to simulation results.