Currently an independent AI Alignment researcher | Former Postdoctoral Research Associate studying galaxy evolution

Currently, I am an independent researcher working on AI alignment research while I work towards transitioning into a career in ML Engineering. Previously, I was a postdoctoral research associate studying galaxy evolution at the University of Washington with Sarah Tuttle. Prior to that, I earned my PhD at UC Irvine working with Michael Cooper while also collaborating with James Bullock , Michael Boylan-Kolchin , and the Local Group .

Whenever possible with my limited free time, I try to get outside to enjoy some combination of snowboarding, nordic skiing, climbing, hiking, and camping.

Research Interests

Generally my research interests focus on dwarf galaxy evolution. More specifically, I am interested in how the environment surrounding a massive galaxy modifies the properties of the satellite galaxies orbiting within the hosts sphere of influence, roughly out to 1 Rvir.

Much of my time has been spent leading the design, data reduction, and analysis of a Keck/DEIMOS survey of low-mass galaxies in the vicinity of galaxy groups at intermediate redshift (z~0.8). This study aims to pull together a spectroscopically complete catalog of satellite galaxies down to log(Mstar) ~ 9.5 Msun around approximately 20 groups in the EGS and COSMOS extragalactic fields.

All of my published work to date has been systematically studying the properties of the satellite galaxies in the Local Group. Ultimately putting together a coherent model for environmental quenching around Milky Way-like hosts out to ~2 Rvir, assuming the distribution of satellite galaxies around the Milky Way and M31 are a respresentative sample.

This has led to a reasonably complete picture of environmental quenching extending down to the stellar mass scale of the "classical" MW dwarf galaxies. The figure below nicely presents an overview of this environmental quenching picture. For a more detailed description of my work and the various implications please see my published work below.

First Author Publications

Environmental Quenching with Gaia

This work in progress uses the recent proper motion measurements from Gaia DR2, combined with some of the latest N-body simulations, to constrain the quenching timescales for individual dwarf satellite galaxies of the Milky Way. Ultimately in an effort to understand environmental quenching in individual dwarf galaxies in the Local Group.

Environmental Quenching in the Field

This work applies the environmental quenching models from TCBFlash to the population of galaxies that reside just outside the virial radius of either the Milky Way or M31, i.e. the field. Demonstrating that quenching mechanisms operating inside the virial radius of the MW or M31 can fully explain the population of quenched galaxies currently residing just outside of Rvir.

Under Pressure

This paper tests how susceptible the population of gas rich field galaxies in the nearby Universe are to ram-pressure and turbulent-viscous stripping in a Milky Way-like environment. The main results show that ram pressure stripping becomes effective at the right stellar mass scale so as to explain the abrupt increase in the quenching efficiency observed in Local Group satellite galaxies. This paper adds further evidence to the picture of environmental quenching put forward in TCBFlash.

TCBFlash

This paper shows that the very efficient environmental quenching observed in the Local Group naturally leads to very short quenching timescales. Strongly favoring ram-pressure stripping as the dominant environmental quenching mechanism responsible for shutting down star formation in the classical dwarf galaxies of the Local Group.

Questions, comments, concerns, or snide remarks?

spfillingham [at] gmail [dot] com