The need for AGN feedback in the cores of galaxy clusters has been long established- without the energy injection by jetted AGN in the central galaxy, we believe that the intracluster medium (ICM) would undergo a cooling catastrophe, leading to prodigious star formation and galaxy building in contravention with observations.  However, the actual physical mechanisms that govern the AGN feedback cycle remain elusive.  In this talk, I will discuss the possible physical process by which the central AGN can heat the ICM.  I will present a series of studies that, step-by-step, move us away from a simple hydrodynamic picture and force us to treat the ICM as a weakly collisional plasma with important properties governed by non-trivial kinetic physics.

Zoom Recording: https://uky.zoom.us/rec/share/KJ27-i3LbcWzxliPLFwhB2tPE-xMj43IbtwwGZkRP7IuIjzXhGwsk4wcHuNH0sde.byF_p5cyNdvVl9EG

The classical cooling-flow model of galaxy clusters fails in the absence of a non-gravitational heating mechanism needed to compensate for radiative cooling in the hot intra-cluster medium (ICM). Feedback from an active galactic nucleus (AGN) offset the cooling via the energy released from the bubbles inflated by radio jets launched from supermassive black holes (SMBH). However, it cannot completely offset the cooling as central cluster galaxies (BCGs) harbor a complex multiphase medium of extended warm and cold gas reservoirs, whose physical origin remains unknown. In the first part of this talk, I will present Atacama Large Millimeter Array (ALMA) and new Multi-Unit Spectroscopic Explorer (MUSE) observations of 15 central cluster galaxies to unveil the origin and life-cycle of these filamentary networks. In the second part of this talk, by extending the sample, including new MUSE observations of 15 central group galaxies (BGGs), I will explore the origin of the gas and the effect of AGN-feedback in the intermediate-mass range between individual galaxies and massive clusters.

Zoom Recording: https://uky.zoom.us/rec/share/dajH7CuefLj_6dRqFEzD7_mWq2TFff7m5JIfWEdY3B9yBR_pnVcG2csgG2-veIin.C2Vqlat9ui9roNhJ

The classical cooling-flow model of galaxy clusters fails in the absence of a non-gravitational heating mechanism needed to compensate for radiative cooling in the hot intra-cluster medium (ICM). Feedback from an active galactic nucleus (AGN) offset the cooling via the energy released from the bubbles inflated by radio jets launched from supermassive black holes (SMBH). However, it cannot completely offset the cooling as central cluster galaxies (BCGs) harbor a complex multiphase medium of extended warm and cold gas reservoirs, whose physical origin remains unknown. In the first part of this talk, I will present Atacama Large Millimeter Array (ALMA) and new Multi-Unit Spectroscopic Explorer (MUSE) observations of 15 central cluster galaxies to unveil the origin and life-cycle of these filamentary networks. In the second part of this talk, by extending the sample, including new MUSE observations of 15 central group galaxies (BGGs), I will explore the origin of the gas and the effect of AGN-feedback in the intermediate-mass range between individual galaxies and massive clusters.

Zoom Recording: https://uky.zoom.us/rec/share/dajH7CuefLj_6dRqFEzD7_mWq2TFff7m5JIfWEdY3B9yBR_pnVcG2csgG2-veIin.C2Vqlat9ui9roNhJ

Both stellar mass and supermassive black holes can vary in brightness extremely rapidly, changing by orders of magnitude within hours. This variability gives us a powerful tool to understand the accretion disks around black holes, and the relativistic winds that they can launch. Because the X-ray spectra are made up of multiple complex variable components, the observed variability can be strongly energy dependent. By calculating the variance of X-ray lightcurves as a function of energy, we can build a variance spectrum. These spectra have been used to qualitatively study black hole variability for many years, but are rarely used quantitatively. I will present recent results from an ongoing research program to model variance spectra of compact objects, including a new method for detecting ultra-fast outflows, implications for accretion disk physics and new constraints on AGN feedback.

Zoom recording:  https://uky.zoom.us/rec/share/z8MTXvJhSmbuS3lYhUsiczW67IPyTDUGMYHrCWXbESp8kCbnmy53RMeJyPfQ66oL.H0J1IJ9f7C5H-iS2

Both stellar mass and supermassive black holes can vary in brightness extremely rapidly, changing by orders of magnitude within hours. This variability gives us a powerful tool to understand the accretion disks around black holes, and the relativistic winds that they can launch. Because the X-ray spectra are made up of multiple complex variable components, the observed variability can be strongly energy dependent. By calculating the variance of X-ray lightcurves as a function of energy, we can build a variance spectrum. These spectra have been used to qualitatively study black hole variability for many years, but are rarely used quantitatively. I will present recent results from an ongoing research program to model variance spectra of compact objects, including a new method for detecting ultra-fast outflows, implications for accretion disk physics and new constraints on AGN feedback.

Zoom recording:  https://uky.zoom.us/rec/share/z8MTXvJhSmbuS3lYhUsiczW67IPyTDUGMYHrCWXbESp8kCbnmy53RMeJyPfQ66oL.H0J1IJ9f7C5H-iS2

Interstellar dust is still a dominant uncertainty in Astronomy, limiting precision in e.g., cosmological distance estimates and models of how light is re-processed within a galaxy. When a foreground galaxy serendipitously overlaps a more distant one, the latter backlights the dusty structures in the nearer foreground galaxy. Such an overlapping or occulting galaxy pair can be used to measure the distribution of dust in the closest galaxy with great accuracy. The STARSMOG program uses Hubble to map the distribution of dust in foreground galaxies in fine (<100 pc) detail. Integral Field Unit (IFU) observations will map the effective extinction curve, disentangling the role of fine-scale geometry and grain composition on the path of light through a galaxy. The overlapping galaxy technique promises to deliver a clear understanding of the dust in galaxies: geometry, a probability function of dimming as a function of galaxy mass and radius, and its dependence on wavelength.

Zoom recording: https://uky.zoom.us/rec/share/ApA_YxbNmZhyvRh6jOJV2-1oZh-8L1zw9O_kKivxWqPvTl1eiVTbv07if7cFx0bO.v9GsO7V4klwdB90p

Interstellar dust is still a dominant uncertainty in Astronomy, limiting precision in e.g., cosmological distance estimates and models of how light is re-processed within a galaxy. When a foreground galaxy serendipitously overlaps a more distant one, the latter backlights the dusty structures in the nearer foreground galaxy. Such an overlapping or occulting galaxy pair can be used to measure the distribution of dust in the closest galaxy with great accuracy. The STARSMOG program uses Hubble to map the distribution of dust in foreground galaxies in fine (<100 pc) detail. Integral Field Unit (IFU) observations will map the effective extinction curve, disentangling the role of fine-scale geometry and grain composition on the path of light through a galaxy. The overlapping galaxy technique promises to deliver a clear understanding of the dust in galaxies: geometry, a probability function of dimming as a function of galaxy mass and radius, and its dependence on wavelength.

Zoom recording: https://uky.zoom.us/rec/share/ApA_YxbNmZhyvRh6jOJV2-1oZh-8L1zw9O_kKivxWqPvTl1eiVTbv07if7cFx0bO.v9GsO7V4klwdB90p

The 7 Ms Chandra X-ray Observatory exposure on the Chandra

Deep Field-South (CDF-S) has provided the most sensitive

extragalactic X-ray survey by a wide margin. About 1050

X-ray sources have been detected, primarily distant active

galactic nuclei (AGNs) and starburst/normal galaxies. The

unmatched deep multiwavelength coverage for these sources

allows superb follow-up investigations, revealing the

details of supermassive black hole growth over most of

cosmic time. I will briefly describe the sources in the

7 Ms CDF-S and highlight some exciting science results.

The latter will include (1) evidence for black-hole vs.

bulge co-evolution in the distant universe; (2) constraints

on supermassive black hole growth in the first galaxies as

revealed by direct detection and stacking; and (3) the

discovery of representatives of a new population of faint,

fast X-ray transient sources. Finally, I will discuss some

future prospects for X-ray surveys of AGNs in the distant

universe, including the ongoing 5 Ms XMM-SERVS survey of

the LSST Deep Drilling Fields and new X-ray missions.

The 7 Ms Chandra X-ray Observatory exposure on the Chandra

Deep Field-South (CDF-S) has provided the most sensitive

extragalactic X-ray survey by a wide margin. About 1050

X-ray sources have been detected, primarily distant active

galactic nuclei (AGNs) and starburst/normal galaxies. The

unmatched deep multiwavelength coverage for these sources

allows superb follow-up investigations, revealing the

details of supermassive black hole growth over most of

cosmic time. I will briefly describe the sources in the

7 Ms CDF-S and highlight some exciting science results.

The latter will include (1) evidence for black-hole vs.

bulge co-evolution in the distant universe; (2) constraints

on supermassive black hole growth in the first galaxies as

revealed by direct detection and stacking; and (3) the

discovery of representatives of a new population of faint,

fast X-ray transient sources. Finally, I will discuss some

future prospects for X-ray surveys of AGNs in the distant

universe, including the ongoing 5 Ms XMM-SERVS survey of

the LSST Deep Drilling Fields and new X-ray missions.