Oral Presentation

Enhanced star-forming activity in a young proto-cluster at the cosmic noon probed by deep narrow-band imgaing

Author(s): Kazuki Daikuhara

Presenter: Kazuki Daikuhara (Tohoku University)

Low-mass galaxies at high redshifts are the building blocks of more massive galaxies at later times and are thus key populations for understanding galaxy formation and evolution. We have made deep narrow-band observations for two proto-clusters and the general field in COSMOS at z~2. In a clumpy young proto-cluster, USS1558, at z=2.53, we find many star-forming galaxies well above the star-forming main sequence at the low-mass end for the field galaxies. This suggests that some environmental effects may work in low-mass galaxies in high-density regions to enhance their star-forming activities. On the massive side of USS1558, as well as in a more evolved proto-cluster, PKS1138 at z=2.16, no significant differences in the distribution on the main sequence diagram are found compared to the field galaxies. We also find that the star-forming activity within individual galaxies in the proto-clusters is more centrally concentrated than those in the field. This is probably due to the enhanced interactions between galaxies in the proto-cluster, which can lose the angular momentum of the gas, drive it towards the galaxy center, and lead to a central starburst. Moreover, due to the depth of our observations, we have discovered unique objects that are detected only in the narrow-band and not in the broad-bands. These objects are expected to be very young galaxies in formation with intense star formation but with extremely low stellar mass yet.