Cake Talk: Thomas Greve and Seiji Fujimoto

When: This Thursday @ 1600 CET

Duration: 1 hour (2 x 20 minute talks + questions)

Galaxy clusters are the most massive gravitationally-bound objects in the Universe. Their alluring beauty so prominently on display in the present-day Universe, mega-parsec-sized structures containing up to thousands of galaxies residing in massive dark matter halos, belies what is likely a complex and prolonged formation history. In this caketalk I will discuss what we know and don’t know about how galaxy overdensities associated with protoclusters formed and evolved with cosmic time.  I will also discuss what role accreting supermassive black holes, so-called active galactic nuclei (AGN), might have had in the buildup of protoclusters.  I will present result from the RAGERS, SPT, and COSMOS2020 surveys – surveys that we are either leading or are deeply involved in at DAWN.

ALMA Lensing Cluster Survey: A Sub-kpc View of [CII] emission from a Sub-L* Galaxy in the epoch of reionization

I present bright [CII] 158 μm line detections from a strongly magnified and multiply-imaged (μ∼20−160) sub-L∗ (MUV = −19.75) Lyman-break galaxy (LBG) at z=6.0719 +/- 0.0004 from the ALMA Lensing Cluster Survey (ALCS). Owing to the uniquely deep and wide survey volume being explored by ALCS, we successfully detect emission lines at 268.7 GHz at ≥ 8σ exactly at positions of two multiple images of the LBG behind a massive galaxy cluster. Our lens models, updated with the latest spectroscopy from VLT/MUSE, indicate that a sub region of the LBG crosses the caustic and is lensed into a long (∼6″) arc with a local magnification of μ∼160, for which the [CII] line is also significantly detected. The source-plane reconstruction resolves the interstellar medium (ISM) structure, showing that the [CII] line is co-spatial with the rest-frame UV continuum at the scale of ∼300 pc. The [CII] line properties suggest that the LBG is a rotation-dominated system whose velocity gradient explains a slight difference of redshifts between the whole LBG and its sub region. The star formation rate (SFR)-L[CII] relations from the sub to the whole regions of the LBG are consistent with those of local galaxies. We evaluate the lower limit of the faint-end of the [CII] luminosity function at z=6, and find that it is consistent with predictions from semi-analytical models and from a SFR function at z=6 converted with the local SFR-L[CII] relation. These results imply that the local SFR-L[CII] relation is universal for a wide range of scales including the spatially resolved ISM, the whole region of the galaxy, and the cosmic scale, even in the epoch of reionization. I will also present JWST observations for this unique lensed system, which has been approved in cycle 1. I will also introduce our DAWN-IRES summer project working with Hollis at the end of the talk.