If the next month doesn't display, please refresh the page.

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.

May
27
Thu
Cake Talk by Kevin Harrington
May 27 @ 16:00 – 17:00
Cake Talk by Kevin Harrington

PASSAGES: A Multi-J CO and [CI] line study of single dish observations of the lensed Planck selected starbursts at cosmic noon

The peak epoch of cosmic star formation also coincides with the peak in the cosmic co-moving molecular gas mass density, at z ~2. Even with sensitive interferometers, only strongly lensed galaxies offer the feasibility to efficiently and systematically detect multiple emission lines tracing the full CO ladder and both atomic carbon fine-structure lines for high-z galaxies. In the past few years, our team has delved into the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts (PASSAGES) in order to conduct such systematic studies to better understand the most active star-forming galaxies in the early Universe. In this talk I will present the results of a state-of-the-art approach to model — simultaneously — both the detected emission lines and the dust SED. Using the largest assembly of ~200 CO/[CI] lines for any uniformly selected high-z sample, we have explicitly derived the infamous alpha conversion factors without assuming any excitation corrections or typically applied values. I will discuss the implications based on such spatially unresolved measurements, including a detailed perspective on the often-used dust continuum approach to deriving the molecular gas masses. I will also present our current understanding of the [CI] line excitation conditions in the context of these detailed radiative transfer models.
More details can be found in the recently published Harrington et al. 2021 (https://ui.adsabs.harvard.edu/abs/2021ApJ…908…95H/abstract    — the ApJ version is recommended; please see the supp tables/figs).