The tip of the red giant branch (TRGB) is a powerful distance indicator that will bridge the gap between local geometric parallaxes and the low-velocity Hubble flow in the JWST era. However, the slope and absolute magnitude of the TRGB has not been robustly calibrated in the near-infrared. To this end, I am reanalyzing a set of archival HST ACS/WFC + WFC3/IR imaging of 23 nearby dwarf and spiral galaxies to produce a calibration of the NIR TRGB color-absolute magnitude relation across a range of star-formation histories.
An illustration of the red giant "branch" (© Meredith Durbin 2019)
A cutout of the HST mosaic of Triangulum.
I am leading the data reduction and analysis for a large Hubble survey of M33, a follow-up to the PHAT program. The survey totals 472 individual HST exposures across six filters, from the near-ultraviolet to the near-infrared. In addition to creating the full-frame mosaics and accompanying release image shown here, I am preparing multiwavelength photometry, artificial star tests, and recent star-formation histories, all of which will be released as high-level science products through the HST archive.
The study of resolved stars in galaxy halos requires a combination of photometric depth, angular resolution, and wide-field coverage that WFIRST/WFI will be able to deliver like no other instrument. I work with Dr. Ben Williams and the WINGS Science Investigation Team to quantify WFIRST's ability to accurately measure the star-formation histories of halo populations and recover their ages and metallicities, and thus to optimize future observing strategies. I presented a poster with accompanying Jupyter notebooks on this at the Astronomy in the 2020s: Synergies with WFIRST meeting in June 2017.
NGC 4631 & NGC 4656 with the WFI footprint superimposed, adapted from Martínez-Delgado et al. 2015.
I am part of the third cohort of the University of Washington's Science, Technology, and Society Studies Certificate Program. I believe that an understanding of how STEM fields operate in relation to social power structures is a critical aspect of being a responsible scientist. I'm particularly interested in the epistemology of "big data", constructions of objectivity, and rhetorics of observation, exploration, and colonization in astronomy.
Prior to entering graduate school, I worked at Space Telescope Science Institute as a Research and Instrument Analyst, where I worked on the HST/WFC3-IR instrument (see WFC3 ISRs 2015-06 and 2015-01), built an internal web interface to access all WFC3 in-flight data and view ongoing monitoring results, and performed artificial galaxy tests and photometric redshift error estimation for the CANDELS survey. As an undergraduate at Pomona College I interned at Carnegie Observatories, where I studied the mid-IR RR Lyrae period-luminosity relation in ω Centauri.