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SED Director’s Seminar



Please join us for the SED Director’s Seminar hosted by the X-ray Astrophysics Laboratory, Code 662!

Major Mergers Do Not Trigger the Majority of Less Luminous AGN at Cosmic Noon
Erini Lambrides

Major mergers are commonly invoked as the dominant triggering mechanism of AGN across large spans of cosmic time; yet, observational and theoretical evidence supporting the ubiquity of this scenario is mixed. In particular, less luminous AGN, which make up the bulk of the AGN population across many epochs, have the most mixed results with regards to the major-merger paradigm. If the AGN-merger paradigm is true, we expect galaxy mergers to coincide with black hole accretion during a heavily obscured AGN phase (NH > 1e23 per cm^2). In this talk, I will discuss the uncovering of the largest, low-to-moderate luminosity heavily obscured AGN sample at cosmic noon. These objects were previously misclassified as un-obscured AGN, and I will justify why these classes of AGN are the ideal sources for testing the major-merger paradigm as a dominant AGN triggering method. I also discuss our results on the combination of deep color Hubble Space Telescope imaging and a novel method of human classification to test the merger-AGN paradigm prediction that heavily obscured AGN are strongly associated with galaxies undergoing a major merger. The results show that there is no statistically significant evidence that obscured AGN at cosmic noon are predominantly found in merging/post-merging systems. These findings indicate other triggering mechanisms must play a significant role in the AGN phenomenon and thus galaxy evolution at this cosmic epoch.

Probing the co-evolution of galaxies and their gaseous reservoirs
Erin Boettcher

Galaxies evolve through complex feeding and feedback processes that circulate baryons between their disks, halos, and surrounding environments. These processes regulate the cold gas reservoirs that fuel star formation. By understanding the galaxy populations that host these reservoirs, we can better understand the physical processes that lead to galaxy growth and quenching. I will present case studies of the galactic environments of two neutral gas reservoirs detected by their damped Lyman-alpha absorption against bright background QSOs in the Cosmic Ultraviolet Baryon Survey. These two systems - an intriguing instance of circumgalactic molecules around an early-type galaxy and a tidally disturbed gaseous envelope surrounding an interacting dwarf galaxy pair - illustrate the diverse galactic hosts of damped Lyman-alpha absorbers. I will conclude by discussing insights into the multi-phase nature of the baryon cycle provided by X-ray observations of the hot phase, including prospects for upcoming missions and probe concepts in development.

Introduction and application of a new blind source separation method for extended sources in X-ray astronomy
Adrien Picquenot

Some extended sources, among which we find the supernovae remnants or the galaxy clusters, present an outstanding diversity of morphologies that the current generation of spectro-imaging telescopes can detect with an unprecedented level of details. However, the data analysis tools currently in use in the high energy astrophysics community fail to take full advantage of these data: most of them only focus on the spectral information without using the many spatial specificities or the correlation between the spectral and spatial dimensions. For that reason, the physical parameters that are retrieved are often widely contaminated by other components. In this talk, we will explore a new blind source separation method exploiting fully both spatial and spectral information with X-ray data, and their correlations. We will introduce the mathematical concepts on which the algorithm relies, and present some current physical applications on SNRs and future studies that it could benefit.

Date May 13, 2022
Start/End Time 11:00 AM - 12:00 PM
Location Microsoft Teams
Event Type Seminars/Colloquia
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