Modern day galaxies populate a bimodal distribution, in both morphology and color space. Their morphological and color properties are also inter-related, with lenticular and elliptical galaxies exhibiting red colors and spiral galaxies exhibiting blue colors. In color space, there is a genuine dearth of intermediate colored galaxies, suggesting that the transition a galaxy undergoes to transform must be rapid, and quenching galaxies, rare. Gas - its presence, absence, and mechanics - serves as the anchor of a galaxy’s transformation from blue to red. I will discuss the nature of gas in transitioning and transitioned galaxies through two lenses: (1) How a galaxy transition is impacts the behavior of molecular gas, and (2) how new observations of molecular gas in quenching and quenched galaxies has recast our understanding of how they ultimately metamorphose from blue, star-forming spirals into red, quiescent ellipticals and lenticulars.

Speaker: Katey Alatalo (STScI)

The 2026 Spring Colloquium talks are held on Wednesdays at 3:00 PM. This colloquium is hosted by STScI and will be held as an in-person and virtual event.

You may join in person at STScI’s John N. Bahcall Auditorium or virtually on the STScI Research YouTube channel.

Please direct questions or comments to contact above. The 2026 Spring Colloquium members are: Nimisha Kumari (STScI), Elena Manjavacas (STScI), Jack Neustadt (JHU), Kevin Schlaufman (JHU), Adam Smercina (STScI), Ethan Vishniac (JHU).