Our ability to detect a galaxy depends not on its brightness, but on its surface brightness – the fainter the surface brightness, the less contrast the galaxy will have against the sky background. The last decade has seen a growing appreciation that there are a large number of Milky Way-mass spiral galaxies that have gone unnoticed because, unlike the Milky Way, they have retained most of their gas rather than produce stars. These Low Surface Brightness (LSB) galaxies are a valuable if elusive key to understanding galaxy evolution.
The MUSCEL program (MUltiwavelength observations of the Structure, Chemistry, and Evolution of LSB galaxies) aims to determine the physical conditions that sent these low surface brightness (LSB) galaxies down a different evolutionary path. Along with my collaborators, Rachel Kuzio de Naray and Sharon Wang, I am working to paint a complete pictures of the star-formation histories, chemical enrichment patterns, and dark matter halos of a sample of LSB galaxies. Our goal is to shed light on why their star formation has been so slow, and, potentially, why galaxies like our Milky Way turned out the way they did.
Our technique relies on ground-based optical spectra combined with space-based UV and IR imaging data. When used together, this information allows us to reconstruct the history of each location within our target galaxies going back billions of years (with the caveat that the stars have moved since then).