I'm a recent Ph.D. graduate from the Department of Physics and Astronomy at the University of California, Davis. I completed my M.S. in Physics at UC Davis in 2018 and I completed my B.S. in physics at Ithaca College in 2017. When not working I spend my time rock climbing, running, hiking, cooking, and playing with my two cats Kelvin and Joule and my dog Plum.
My research is focused on weak chemical tagging, a tool used extensively in galactic archaeology. Galactic archaeology is the science of understanding the formation and evolution of galaxies through precise measurements of their current state. Weak chemical tagging is a technique used to identify the birth location of a star using galactic chemical evolution models and measurements of stellar abundances. This technique works because stellar abundances are invariant (unchanging) observables, so they directly connect a star to its birth location. For all of the work that I do, I use hydrodynamic zoom-in simulations of Milky Way-like galaxies from the FIRE (Feedback In Realistic Environments) project.
Videos showing the redshift evolution of the gas (left) and stars (right) in a sample simulated galaxy.
Following up on my previous work (paper link) I have characterized the 3-D elemental abundance distributions of newly formed stars (paper link). This defines the initial conditions for chemical tagging. In this work, I provide functional forms and best fits to the evolution of stellar abundances, the evolution of galactic radial abundance gradients in newly formed stars, and the evolution of azimuthal scatter in abundances in newly formed stars. Download figure data from the paper here
Disk-wide stellar gradients, like gas gradients tend to get steeper with time. Additionally, we fit two component linear profiles to the radial abundance gradients in stars and find the inner gradient to be consistently steeper than the outer gradient.
Azimuthal scatter in stellar abundances is nearly independent of radius. Additionally, azimuthal abundance scatter in stars is on average less than the scatter seen in all gas. However, the scatter still decreases with decreasing redshift.
We find a transition lookback time after which the radial abundance variations are larger than the average 360 azimuthal abundance scatter. This transition time is approximately 1 Gyr earlier than the time seen in gas.
The solid lines show the radial and azimuthal abundance variations in newly formed stars, the dashed lines show these variations as reported in my previous paper. At present day, stellar and gas variations are comparable, however the variations are smaller in newly formed stars than in all gas at earlier times.
To understand the effectiveness of chemical tagging we need to first understand the initial conditions from which stars form. In my first paper, I explored the evolution of the 3-D distribution of abundances in the gas disks of Milky Way-like galaxies. The main takeaway from this paper is that gas disks are not azimuthally homogenous across time, as has been typically assumed. There exists a transition redshift for galaxies before which azimuthal variations dominate over radial gradients and current chemical tagging techniques are likely limited by current galactic chemical evolution models.
We find radial gradients tend to get steeper with time as galaxies become more rotationally dominated.
We find galaxies have strong azimuthal scatter at early times which decreases to match observed values at z=0.
We find galaxies transition from azimuthal scatter dominated to radial gradient dominated around z~0.8.
The distribution of transition redshifts for our suite of 11 galaxies.
Email me at mattbellardini[@]gmail[.]com