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My dissertation research focused on the Stellar Mass - Halo Mass (SMHM) relation for the most massive galaxy clusters in the local, low-redshift, universe. The SMHM relation compares the observable amount of stellar matter, to the total mass of the galaxy cluster. A large discrepancy exists among published SMHM relations. To address this discrepancy, we incorporate the magnitude gap, the difference in brightness between the Brightest Central Galaxy (BCG) and the nth brightest cluster member, as a 3rd parameter into our analysis.
To investigate whether the incorporation of the magnitude gap in the SMHM relation explains the previously observed range in published SMHM relations and reduces the intrinsic scatter in the relation, we use a combination of observations from SDSS-DR12 and simulated clusters from the Henriques et al. (2012) prescription of the MILLENNIUM Simulation. Once we have measured each of the three parameters and their respective errors, we use a Bayesian approach and an MCMC analysis to determine the slope, zero-point, stretch factor (which measures the impact of the magnitude gap), and the intrinsic scatter.
We observe a stratification between the stellar mass and magnitude gap, at fixed halo mass in both the SDSS-C4 observations and simulations. Our quantitative results highlight that the stretch-factor is definitively non-zero and that the intrinsic scatter significantly decreases with the incorporation of the magnitude gap. Additionally, the observation of the magnitude gap stratification serves as observational evidence for the hierarchical growth of BCGs.
The results of this work will be presented in the publication Golden-Marx & Miller (2018).
We then analyzed the redshift evolution of the impact of the magnitude gap by looking at these same parameters out to higher redshifts using the Guo et al. (2011) prescription of the MILLENNIUM simulation and SDSS-redMaPPer data (Rykoff et al. 2014) along with the SDSS-C4 sample from Golden-Marx & Miller (2018). Our analysis covers the redshift range 0.03 < z < 0.3. To do this analysis we incorporated both redshift and magnitude gap into the SMHM relation. In doing so, we found the first statistically significant observational evidence that the slope of the SMHM relation decreases at higher redshift, which aligns with the hierarchical assembly of the BCG. Additionally, we reconfirmed the results of our previous work by using the SDSS -redMaPPer clusters.
This works is presented in the publication Golden-Marx & Miller 2019
Additionally, I am currently working on extending this analysis out to z=0.6 using DES data and the ILLUSTRIS TNG300 simulation.
I am also starting a project which focuses on measuring more accurate photometry of bright galaxies in DES with Dr. Yuanyuan Zhang.
SDSS DR12 C4 cluster
Prior Research
Prior Research
Prior to working on the SMHM relation with Prof. Miller, I studied Classical Oe and Be stars in the field of the Small Magellanic Cloud (SMC) with Prof. Oey. Our research primarily focused on Oe stars and how the frequency of Oe (and Be stars) is inversely correlated with metallicity. Our work, presented in Golden-Marx et al. (2016), presents a large population of Oe stars previously unidentified in the SMC, including some of the earliest type Oe stars to date. We find that Oe stars are much more common in the SMC and that a significant population of field O stars are Oe stars.
Intergalactic Tramp Novae
As an undergrad, I did an REU at the American Museum of Natural History, where I worked with Prof. Michael Shara and Dave Zurek studying intergalactic tramp novae in the M81 group. Tramp novae are classical novae, which have been removed their host galaxy due to tidal interactions. The goal of this work was to use tramp novae as a tracer for the fraction of stars which are removed from their host galaxies due to tidal interactions. I also continued this project as part of my senior thesis at Brown University.
Fossil Group Galaxies
While at Brown University, I worked with Prof. Ian Dell'Antonio. The scope of the project focused primarily on Fossil Group Galaxy progenitors and whether Fossil galaxies form via dry, star formationless mergers. Fossil galaxies are massive galaxy groups with large magnitude gaps (> 2.5) and large X-ray Luminosities. Fossil Galaxies, the magnitude gap, and galaxy clusters have continued to be an area of research that I am actively studying.
Galaxy Classification
My first research experience was working with Prof. Mary Crone-Odekon of Skidmore College. My work focused primarily on classifying galaxies and identifying mergers and tidal tails in the MKW 11 Cluster.
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