Poster: Mapping the Stellar Fossil Record of M101 with HETDEX: Spatially Resolved Ages and Metallicities

We present integrated-light and spatially resolved analyses of the stellar populations in the nearby, face-on spiral galaxy M101 (NGC 5457) using integral field spectroscopy from the VIRUS spectrograph, taken as part of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX); alongside this work, we release the reduced M101 VIRUS data cube for community use. The VIRUS wavelength range (3500-5500 Å) provides access to age- and metallicity-sensitive absorption features across a large fraction of M101’s star-forming disk. We combine a high-S/N integrated spectrum with archival multiwavelength photometry to constrain global stellar properties via full spectrophotometric fitting with pPXF and to infer the integrated star formation history (SFH) with Bagpipes. Both spectral fitting and SFH modeling suggest a young component of age 200-300 Myr, comparable to the timescale for the M101-NGC 5474 interaction, as well as underlying older population. We further map stellar population parameters over the main star-forming disk and construct radial profiles of stellar ages and metallicities, finding evidence for both secular and external evolution. Together, these resolved stellar population maps and gradients provide a disk-wide view of how secular evolution and environment have played a role in M101’s formation and evolution.

Sep 14, 2026 12:00 PM — 5:00 PM