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Upcoming Seminar/Colloqium

Topic:

A comprehensive study of broad absorption line quasars

Speaker : Sapna Mishra
Affiliation : ARIES
Date & Time :
Venue : Auditorium & Online
Abstract :

The presence of a supermassive black hole (SMBH) at the core of an Active Galactic Nucleus (AGN) may predict the final evolution of its host galaxy. Energy generation via accretion in the form of outflows/jets, known as AGN feedback, can cause heating or compression of gases around the host galaxy. This occurs via two modes, (i) radiative and (ii) kinetic. The radiative mode occurs in highly luminous sources, delivering high radiation pressure and hence resulting in the ejection of gases in the form of strong outflows. The kinetic mode scenario is perhaps due to the radio jets mainly occurring in low luminous AGNs. In my thesis, I have studied these modes of the AGN feedback to understand the dynamics of the gases in CGM and the metal enrichment of the IGM via detailed photometric and spectroscopic analysis. The most spectacular manifestation of quasar outflows is the Broad Absorption Lines (BAL) seen in the blue wings of the prominent emission lines like CIV and MgII, in the rest-frame UV spectra of 15-20% of optically selected quasars. The extant models of these outflows tend to predict that they originate from the rotating accretion discs of AGN and are accelerated to high speeds via radiative and/or magneto-centrifugal forces. These BAL troughs showcase rapid variation over time scales ranging from hours to a few years. In addition, BAL quasars generally demonstrate soft X-ray weakness possibly due to a highly ionized absorber or “shielding gas” exists between the BAL outflows and source of ionizing radiation which prevents the BAL clouds from overionization. Although many studies have been conducted to examine the main cause for the extreme variability and the X-ray weakness in BAL quasars, answers to these enigmatic problems with novel and enlarged datasets would be a valuable addition to the current understanding. The related future prospects which I propose to carry out in ARIES: (i) On the nature of multi-phase outflows in IR-bright BAL quasars, (ii) The contemporaneous optical/UV and X-ray study of non-BAL to BAL transitions, and (iii) Intra-night monitoring of blazar counterparts of BAL quasars. In this talk, I will discuss the outcomes of my thesis work and the research projects that I wish to carry out during my post thesis period.

About Speaker :

Sapna Mishra has submitted her thesis to Delhi University. This is her post thesis submission talk in ARIES.