DAO Astronomy Colloquium Schedule
Online via Zoom, Victoria
Tuesdays at 11am unless otherwise indicated with (***)
Tues January 19th, 11am, Zoom: Kim-Vy Tran (UNSW) Recording
MOSEL & ZFIRE : Tracking Galaxy Growth at Cosmic Noon: MOSEL and ZFIRE are deep near-IR spectroscopic surveys that track how galaxies assemble at 1.5<z<3.5. With MOSEL, we confirm a population of Extreme Emission Line Galaxies at z~3 with Oxygen equivalent widths >250 Angstroms and hypothesize that most galaxies at z>3 go through a strong starburst phase. We compare galaxy kinematics to IllustrisTNG to determine how massive galaxies at z~3 build their stellar mass (mostly by accreting other galaxies) and end their star formation (puffy galaxies quench slower). I also summarize results from our ZFIRE survey where we find faint imprints of environmental effects on the Inter-Stellar Medium of cluster galaxies at z~2.
Tues January 26th, 4pm***, Zoom: Takuma Izumi (NAOJ) Recording
ALMA observations of z > 6 low-luminosity quasars: unbiased view on the early co-evolution and feedback: I will review our multi-wavelength campaign observations toward z > 6 optically “low-luminosity” quasars, which were originally discovered by our wide-field Subaru Hyper Suprime-Cam (HSC) optical imaging survey. Our HSC quasars are an order of magnitude fainter at rest-UV than previously-known luminous quasars. Subsequent NIR spectroscopic follow-up observations revealed a wide spread in their BH mass, hence Eddington ratio (~0.1 to 1). We have also been carrying out a series of ALMA observations ([CII] line and FIR continuum emission) toward a sample of ~20 HSC quasars. We found that their host galaxies are basically FIR-faint with LIRG-class luminosities (or SFR < 100 Msun/yr). Using the [CII]-based dynamical mass as a surrogate for bulge stellar mass, we found that a significant fraction of these low-luminosity quasars are located on or even below the local co-evolution relation, indicating the BH-galaxy co-evolution is indeed taking place at z > 6. I also talk about a particular case of a z = 7.1 HSC quasar, where we found a vigorous starburst and, surprisingly, fast [CII] outflows. Given also its broad absorption line = BAL feature (indication of nuclear outflow), quasar-driven feedback that affects the host galaxy occurred already at this reionization era.
Tues February 2nd, 11am, Zoom: Ilse Cleeves (U. of Virginia) Recording
The key role of astrochemistry in driving planet formation and habitability: Historically, our perspective on how planets form and obtain their compositions has been motivated by our Solar System. However, we are just one system, and missions like Kepler and TESS have revealed a variety of planetary types and architectures. How do we fit in? In the last five years, the Atacama Large Millimeter Array has revolutionized our understanding of planet formation by observing the process at high spatial resolution (reaching in some cases ~AU scales) matched with unprecedented sensitivity at radio wavelengths. In this presentation, I will review recent highlights from the TW Hya as a Chemical Rosetta Stone ALMA project and discuss how these findings both confirm and, in some ways, challenge our current picture of the chemistry of planet formation.
Tues February 16th, 11am, Zoom: Genaro Suarez (Western U.) Recording
An Accurate Look at the L-to-T Spectral Type Transition: I will present the most comprehensive spectral energy distribution (SED) of a young brown dwarf at the L/T transition by combining new Spitzer mid-infrared spectra and photometry with previous observations of HN Peg B. We use this SED to evaluate the performance of various atmospheric models and found that models with condensates and using non-equilibrium chemistry reproduce better the data. However, these models face challenges in reproducing the observed methane and carbon monoxide absorption strengths mainly over the 3–5 um region. By using the assembled SED and the Gaia EDR3 parallax of the host star, we derive accurate fundamental parameters of HN Peg B. We find that, in comparison to older early T dwarfs in the field, HN Peg B is ≈100 K cooler, has a ≈ 13% larger radius, and has a consistent bolometric luminosity. A comparison among moderate-dispersion near-infrared spectra of HN Peg B and other young and old dwarfs with similar spectra types shows that the 1.25-micron potassium line strengths are mostly insensitive to surface gravity in early-T dwarfs.
Tues February 23rd, 3pm***, Zoom: Emily Wisnioski (ANU) Recording
The resolved dynamics and metallicity of galaxies across cosmic time: I will discuss the formation and evolutionary paths of star-forming galaxies. Kinematics and chemical properties have revealed that the majority of star-forming galaxies at ‘comic noon’ host thick disk-like structure and a turbulent less enriched interstellar medium. I will present results utilising synergies with multi-wavelength ground and space-based surveys to trace the evolution of spatially-resolved dynamics and star formation from a homogeneous sample over 5 billion years of cosmic history. These results when combined with local galactic archeology studies and new analytic models provide insights into how the structures of local galaxies including the Milky Way were formed. I will discuss the observational results within the framework of theoretical models for the formation of gas phase metallicity gradients and the local stellar age-velocity dispersion relation.
Tues March 9th, 11am, Zoom: Laura Keating (AIP)
Tues March 16th, 1pm***, Zoom: JJ Eldridge (U. Auckland)
Some of the things binary stars do…. Most of the stars in the Universe are not single like our Sun but in binary stars systems. A binary star is composed of two stars in orbit around each other, as they age they can “get-in-each-others” way and experience very different evolution to that our stars like our Sun. Only over the last decade it has become clear that to accurately understand the Universe we need to take account of these interacting binary stars. In my talk I will go over a few examples showing how understanding binary stars allows us to understand the appearance of galaxies, the diversity of supernovae, the production of the most abundant and rarest elements and discuss the latest LIGO/VIRGO O3a results and their implications for binary evolution.
Tues March 23rd, 11am, Zoom: Meredith Macgregor (U. of Colorado Boulder)
Tues March 30th, 11am, Zoom: Hanno Rein (U. of T)
Tues April 6th, 11am, Zoom: Tuan Do (UCLA)
Tues April 13th, 11am, Zoom: Deep Anand (U. of Hawaii)
Tues April 20th, 11am, Zoom: Auriane Egal (Western U.)
Tues April 27th, 11am, Zoom: Oliver Müller (U. of Strasbourg)
Tues May 4th, 11am, Zoom: Judit Prat (DES/U. of Chicago)
Tues May 25th, 11am, Zoom: Carl Fields (MSU/Arizona/LANL)
Tues June 1st, 11am, Zoom: Yamila Miguel (Leiden)
Tues June 8th, 11am, Zoom: Shany Danieli (IAS)
Tues June 22nd, 11am, Zoom: Jane Huang (U. of Michigan)