Investigating the M101 Group with Deep Narrowband Imaging

Abstract

I present deep, narrowband imaging of the nearby spiral galaxy M101 and its environment in a series of projects investigating its star-forming properties, metallicity distribution, and evolutionary history. The M101 Group, although being a relatively poor group with only one major member, is a dynamically active group. M101 itself is thought to have had a recent encounter with its most massive satellite NGC 5474. Using narrowband images targeting key emission lines (Hα, Hβ, [OIII]λλ4959,5007, and [OII]λ3727), I can investigate how this interaction might have propagated throughout the M101 Group and within the individual galaxies themselves.

In the first project, I searched for extragalactic star-forming regions in the M101 Group as these objects may be isolated star-forming events tracing the tidal debris from the interaction. After carefully removing stellar contaminants and high-redshift background objects, I found that of the 27 objects found, almost none of them were outlying star forming regions or new star-forming dwarfs. This reaffirms that the interaction was likely a weak interaction, not prone to producing tidal debris.

In the second project, I used the complete spatial coverage of our narrowband images to estimate the oxygen abundances of the M101 Group. With three calibration techniques for the strong-line ratio R23, I estimated abundances for ~720 HII regions scattered across three galaxies, the most extensive sample of HII regions in the M101 Group to date. M101 shows a strong abundance gradient with some evidence for flattening beyond R ~ 15 kpc. I interpret these abundance patterns in the context of M101’s interaction history and the internal dynamics of its disk.

Finally, I present ongoing research using the same narrowband imaging dataset to study M101’s intermediate age stellar populations as well as the properties of the diffuse ionized gas throughout M101’s disk.

Ray Garner

TAMU Astronomy Postdoctoral Researcher

I’m a scientist, Star Wars fan, and amateur photographer raised in Georgia. My research interests include galaxy evolution, star formation, satellite galaxies, and nebular diagnostics.