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Mar
4
Thu
Cake talk by Hannah Stacey (MPA Garching)
Mar 4 @ 14:00 – 14:30

100-pc resolution of z~2 quasar host galaxies with ALMA: witnessing the formation of compact spheroids

With the advent of ALMA, the interstellar medium of high-redshift galaxies can be probed at remarkable resolution and sensitivity. We push the limits of ALMA even further by studying strongly lensed galaxies where we are able to probe structures of 10s–100s parsecs in scale. Using novel lens modelling techniques, we reconstruct the molecular interstellar medium (ISM) structure and kinematics of z~2 galaxies hosting luminous quasars, to give a new perspective on the physical processes that drive the formation and evolution of quiescent galaxies, from birth to quiescence. A key aspect in this study is how spheroids formed very high stellar densities and grew concurrently with their supermassive black holes. We find evidence the quasar host galaxies are observed in a stage during a rapid transformation into compact spheroids, where a high density of dynamically unstable gas leads to efficient star formation and black hole accretion. Furthermore, I present first results of mapping the structure and kinematics across the CO ladder – the highest resolution of the molecular ISM for a quasar host at cosmic noon – which demonstrates a highly non-homogeneous ISM.

Jun
24
Thu
Cake Talk: Thomas Greve and Seiji Fujimoto @ Zoom
Jun 24 @ 16:00 – 17:00
When: This Thursday @ 1600 CET
Duration: 1 hour (2 x 20 minute talks + questions)

Thomas Greve:

Galaxy Clusters – Emergence and Prominence
 
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.
Seiji Fujimoto: 
 

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 (μ20160) 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 μ160, 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.