My Work
I am currently involved with two large surveys of HI absorbers: the First Large Absorption Survey in HI (FLASH; PIs Elaine Sadler & Elizabeth Mahony) and the MUSE-ALMA Haloes Survey (PI Céline Péroux). In addition to this, I am working on interpreting galaxy-absorber studies using the cosmological simulation TNG50 with Rahul Ramesh and Dylan Nelson. Below is a short summary of past and ongoing works. A full list of publications can be found here: ADS/ORCiD.
The ASKAP-FLASH survey blindly targets HI 21-cm absorption at 0.4 < z < 1.0 towards background radio continuum sources. ASKAP's large spectral bandwidth, large field of view and location in a radio-quiet zone opens up a completely new parameter space for studying 21-cm absorption. We expect at least several hundred absorbers for the full FLASH survey.
During my Honours, I reduced and analysed MUSE data centred on the z = 0.45 absorber towards PKS 1610-771. I found evidence for extragalactic HI caused by interactions between two galaxies near the sightline.
Currently, I work with the survey team on analysing optical counterparts to these absorbers in the pilot and full survey. I also help with the analysis of absorption lines using the automated FLASHfinder algorithm by identifying regions in the spectra affected by RFI or correlator issues.
During my time at ESO, I worked on the MUSE-ALMA Haloes survey with Céline Péroux and Martin Zwaan. The survey consisted of 19 MUSE fields centred on 32 strong HI absorbers with median redshift z ~ 0.6.
My work included the extraction of spectra for continuum and emission-line sources for all 19 fields. This resulted in in >700 sources with MUSE spectra. I combined the MUSE catalogues with the list of objects from HST imaging analysed by Arjun Karki to create the final catalogues for the survey paper.
In my first paper, we connected the properties of the HI absorbers with their galaxy counterparts. In total, we found 79 galaxies associated with the 32 absorbers and that more than 50% of absorbers had multiple associated galaxies. Additionally, we studied the distribution of HI and metals around the CGM.
My second paper looked at the various gas flows traced by absorbers in the CGM. We found evidence for outflows, inflows, gas in the intragroup medium and low-mass satellite galaxies all contributing to the population of absorbers.
Inspired and perhaps, slightly frustrated by the fragmentary information provided by absorption-line studies, I started a small collaboration with Céline Péroux, Rahul Ramesh and Dylan Nelson to understand the physical origins of absorbers using observationally-driven TNG50 mocks. More specifically, we seek to understand the relationship between line of sight velocity and the physical distance, the importance of low-mass satellite galaxies in absorber-galaxy studies and the fidelity of using the azimuthal angle to identify inflows and outflows. The work is still in progress and soon to be submitted. A copy of the paper is available upon request.
We plan to extend the study to other ions such as Mg II, C IV and O VI and to higher redshifts, allowing us to interpret results from upcoming JWST surveys.