U2-2016
Host: Matteo Bonetti
Cloud–Cloud Collisions and Triggered Star Formation
Rei Enokiya (National Astronomical Observatory of Japan, NAOJ)
Star formation is a fundamental process in galactic evolution. Over the past several decades, one of the key questions has been whether nstar formation is externally triggered or self-regulated within a closed nsystem. The role of external triggering, which ncan efficiently concentrate mass into a small volume, has attracted particular attention in connection with the formation of massive stellar clusters—processes that, in extreme cases, may lead to starbursts. In this talk, I will review our observational and theoretical studies of triggered star formation induced by cloud–cloud collisions over the past decade.
The Dust to Ice Ratio Varies Among and Within Interstellar Clouds toward the Galactic Center
Savannah Gramze (University of Florida)
The center of our Galaxy, the Milky Way, is an extreme environment hosting the supermassive blackhole Sgr A* and the massive nuclear stellar disk. The Central Molecular Zone (CMZ) surrounding it contains 80% of the Galaxy’s dense molecular gas. The CMZ is made of gas that is hotter, more turbulent, and more rich in molecules than the disk of the Galaxy where the Sun resides, yet it has a low star formation rate relative to the amount of dense gas present. In the cold, dense environment of infrared dark clouds, CO freezes out of the gas phase and onto dust grains. We present JWST NIRCam observations showing that the amount of ice varies between infrared dark clouds in the disk of the Galaxy and in the CMZ, and it varies among clouds within the CMZ itself. Even in regions with no evidence of cold dense clouds, we detect CO ice absorption. The amount of ice and extinction allows us to infer the line of sight locations of the clouds. High ice column densities in the CMZ point toward a higher gas phase metallicity than the disk. These measurements imply a varied history of chemical enrichment, lifetimes, and origins of the clouds.