Lunch talk on Jul. 5, 2021

GOODS-ALMA: Optically dark ALMA galaxies shed light on a cluster in formation at z = 3.5

Speaker: Luwenjia Zhou (Nanjing University)

Venue: SWIFAR Building 2111

Time: 12:30 PM, Monday, Jul. 5, 2021

Abstract: 

Thanks to its outstanding angular resolution, the Atacama Large Millimeter/submillimeter Array (ALMA) has recently unambiguously identified a population of optically dark galaxies with redshifts greater than z = 3, which play an important role in the cosmic star formation in massive galaxies. In this work we study the properties of the six optically dark galaxies detected in the 69 arcmin2 GOODS-ALMA 1.1mm continuum survey. While none of them are listed in the deepest H-band based CANDELS catalog in the GOODS-South field down to H = 28.16 AB, we were able to de-blend two of them from their bright neighbor and measure an H-band flux for them. We present the spectroscopic scan follow-up of five of the six sources with ALMA band 4. We present evidence that nearly 70% (4/6 of galaxies) of the optically dark galaxies belong to the same overdensity of galaxies at z ∼ 3.5. overdensity The most massive one, AGS24, is the most massive galaxy without an active galactic nucleus (AGN) at z > 3 in the GOODS-ALMA field. It falls in the very center of the peak of the galaxy surface density, which suggests that the surrounding overdensity is a proto-cluster in the process of virialization and that AGS24 is the candidate progenitor of the future brightest cluster galaxy (BCG).

Report PPT:  SWIFAR_Luwenja Zhou.pdf