Forum Schedule: Fridays 3:45pm - 4:45pm
|Title & Abstract
|Dr. Monika Moscibrodzka
|"Simulations of gas dynamics around supermassive black holes"
Actively accreting black holes, residing in centers of Active Galactic Nuclei (AGN), produce powerful outflows with speeds ranging from hundreds km/s to near the speed of light. The origin and mechanism of these outflows is not yet fully understood. A better theoretical understanding of a black hole accretion and outflow production would help to get insights into how important their role in the evolution of galaxies is. In the first part of my talk I will present highlights of multi-dimensional, hydrodynamic, computer simulations of gas dynamics under influence of strong gravitational and radiation field present in a galaxy center. Our robust model accounts for many of the common features observed in AGN, in particular the outflows and clouds. In the second part of the talk I will discuss a coming opportunity to directly observe the dynamics of gas falling towards the supermassive black hole in the center of the Milky Way. This unique opportunity might be a chance for a first, direct detection of a black hole horizon and tests of General Relativity Theory in a strong gravitational field.
|Prof. Jenny Greene
|"Galaxy Nuclei, Galaxy Outskirts"
I will talk about two different aspects of massive galaxy evolution. First, I will discuss the mass assembly of massive galaxies based on high signal to noise spectra beyond the effective radius for eight elliptical galaxies. The stars in the outskirts of these galaxies are enriched in alpha elements but have low metallicity, similar to thick disk stars in our We suggest that these stars were accreted from small galaxies that formed early and had a truncated star formation Second, I will discuss supermassive black hole scaling relations, and what they may tell us about the coevolution of black holes and I will end with tantalizing new clues about the lifetimes of tight supermassive black hole binaries.
|Dr. Shane Davis
|"Radiation Pressure in Star Forming Galaxies and Accretng Black Holes: Can Radiation Push Gas Around?"
Increases in computing power and improvements in algorithms are facilitating major advances in our ability to model the transport of radiation in numerical simulations of astrophysical plasmas. First, I will briefly describe new simulation tools that we have developed to solve the equations of radiation magnetohydrodynamics. I will then discuss applications of these tools to astrophysical environments where radiation forces are so strong that they are the dominant support against gravity: rapidly star forming galaxies and the inner regions of black hole accretion disks. I will focus on their dynamic and thermodynamic (in)stability and its implications for observable phenomenon from these systems.
|Dr. Kyoung-soo Lee
|"The Varied Fates of High-Redshift Galaxies"
Recently, significant progress has been made in characterizing key statistics of high-redshift galaxies; their UV luminosity function, stellar mass function, and clustering. However, a more detailed understanding of the star-formation, assembly and chemical histories of the galaxies has been more difficult to obtain. We are still unable to translate measures into a comprehensive physical picture and to address fundamental questions on the physical processes driving galaxy evolution: What drives star formation? What is the typical star formation history (SFH) of a galaxy, does it depend on luminosity/mass? Do more UV-luminous galaxies have different physical properties (ages, metallicity, SFH, kinematics) than their less-luminous counterparts? In this talk, I will review recent progress in our understanding of high-redshift galaxy formation, and show a series of observational evidence that strongly suggest that galaxies have very different evolutionary paths, which depend primarily on where they are born.
|Dr. James Owen
|"Evaporation of discs and planets"
Planet formation and evolution remain unsolved problems. In the first part I will discuss how the protoplanetary disc evolves - the reservoir of gas and dust from which planets are expected to form - where heating of the upper disc by X-rays removes material in a disc wind which ultimately leads to the disc's destruction, setting the time-scale for planets to form. In the second part I will discuss how the similar physics of disc winds can be applied to highly irradiated planets. Where the X-rays and EUV may entirely remove a gaseous planet's envelope in Gyr time-scales, leaving behind a rocky core.
|Dr. Kristian Finlator
|"Galaxy Formation and Feedback During the Cosmic Dark Ages"
The study of structure formation during the first billion years is advancing rapidly, driven by pathfinding discoveries with the Hubble Space Telescope and motivated by anticipated studies that will wield next-generation facilities including ALMA, JWST, and I will review our current understanding of the typical growth history of the young galaxies that are now being observed well into the cosmic dark ages. I will discuss observational and theoretical arguments that constrain how these galaxies ionized and heated the intergalactic medium. I will also describe how the intergalactic medium's structure regulated the progress of cosmological reionization. Finally, I will use a new class of cosmological radiation hydrodynamic simulations to ask how existing observations of low-ionization metal absorbers constrain the earliest stages of structure formation.
|Prof. Sukanya Chakrabarti
(Florida Atlantic Univ.)
|"A New Probe of Dark Matter in Spiral Galaxies"
The cold dark matter paradigm of structure formation is successful at recovering the basic skeletal structure of the universe -- the large-scale distribution of galaxies. However, the agreement between theory and observation is less secure when this model is applied to galactic (and sub-galactic) Problems such as the missing satellites problem, the lack of massive dark satellites, and the unexpected distribution of galactic satellites in the Milky Way, suggest that the current paradigm is not complete in its description of galaxy The extended atomic hydrogen disks of galaxies provide an unique probe of galaxy evolution. They are ideal tracers of tidal interactions with satellites and the galactic gravitational potential well. We have recently developed a method whereby one can infer the mass, and relative position (in radius and azimuth) of satellites from analysis of observed disturbances in outer gas disks, without requiring knowledge of their optical light. I will present the proof of principle of this method by applying it to galaxies with known optical I will end by presenting recent work that extends our earlier results to constrain the density profile of dark matter in local spiral galaxies. I will also compare and contrast this method to gravitational lensing as a means of probing dark matter in galaxies.companions. evolution. scales.