MATs (Monday Afternoon Talks), 2/26/2024 — Speakers: Natasha Latouf And Martin Millon

Monday February 26, 2024 3:00 pm

MATs (Monday Afternoon Talks)

3:00pm – 3:30pm, Natasha Latouf
Bayesian Analysis for Remote Biosignature Identification on exoEarths (BARBIE): Using Grid-Based Nested Sampling in Coronagraphy Observation Simulations for Molecular Detection.
We have seen the discovery and confirmation of thousands of exoplanets since the first planet found orbiting a Sun-like star, and we are now on the verge of entering an exciting new era of planetary exploration: detection and characterization of terrestrial exoplanet atmospheres. Detecting H2O, O2, and O3 in exoplanet atmospheres is the first step on the path to determining planet habitability, and efficiency is key to maximizing the science output from limited observation time, especially in next-generation instrument design such as the upcoming Habitable Worlds Observatory (HWO). Knowing this, the optimal wavelength for the spectral bandpass used for observations is a crucial factor to consider.
Coronagraphic design currently limits the observing strategy used to detect H2O, O2, and O3, requiring the choice of specific bandpasses to optimize abundance constraints. We use a pre-constructed grid consisting of 1.4 million geometric albedo spectra across a range of abundance and pressure and interpolate to produce forward models for an efficient nested sampling routine, PSGnest, thus enabling wide ranges of parametric retrievals. By understanding the SNR requirements for detecting molecules of interest, and properly prioritizing the spectral bandpasses to optimize detectability of different atmospheric constituents, we can inform the best instrument designs and observing procedure as we look to the HWO.
HWO is a multi-generational Great Observatory telescope, encompassing many years of scientists being trained and recruited. By implementing effective and ethical mentorship techniques based on current research into the ground floor of HWO development, we can increase the rate of recruitment and retention of historically minoritized groups in astronomy and physics using HWO.

3:30pm – 4:00pm, Martin Millon
Strong gravitational lensing by AGNs as a probe of the quasar-host relations in the distant Universe
The tight correlations found between the mass of the supermassive black holes (SMBH) and their host galaxy luminosity, stellar mass, and velocity dispersion are often interpreted as a sign of their co-evolution. Studying these correlations across redshift provides a powerful insight into the evolutionary path followed by the quasar and its host galaxy. While the mass of the black hole is accessible from single-epoch spectra, measuring the mass of its host galaxy is challenging as the quasar often overshines its host.
In this talk, I will present a novel technique to probe quasar-host relations beyond the local universe with strong gravitational lensing, hence overcoming the use of stellar population models or velocity dispersion measurements, both prone to degeneracies. I will present the first case of strong lensing *by* a quasar, which allowed us to measure the mass of its host very precisely. I will show our mass models of this exceptional system, where the quasar and its host are seen as a substructure of a nearby more massive galaxy, but still produce a detectable lensing signal.
Finally, I will conclude with the prospects of this method in the era of large imaging and spectroscopic surveys. I will present our methods to find these systems in DESI, using Machine Learning. A sample of such quasar-galaxy or quasar-quasar lenses should reach a few hundred with DESI, Euclid, and Rubin-LSST, thus enabling the application of such a method with statistically significant sample sizes.
Hosts: Minghao Yue, Daniele Michilli


  • Natasha Latouf, George Mason University, NASA Goddard
  • Martin Millon, Stanford University