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Astro Lunch Talks

Astro Lunch Talks
Wednesdays, 11:45am-1:00pm, 76-1275 Carlson Learning Center.
Topics will be emailed prior to the talk. Please contact Ben Sargent for more information. 
Upcoming Talk Details
Date/Time: May 20,  12:00pm 76-1275
 
Speaker: David Merritt
TITLE: Recent results on the final-parsec problem
ABSTRACT: A binary supermassive black hole loses energy via ejection of stars in a galactic nucleus, until emission of gravitational waves becomes strong enough to induce rapid  coalescence.
Evolution via the gravitational slingshot requires that stars be continuously supplied to the binary, and it is known that in spherical galaxies the reservoir of such stars is quickly depleted, leading to stalling of the binary at parsec-scale separations. Recent N-body simulations of galaxy mergers suggest that this stalling may not occur. However, it remains unclear to what degree these conclusions are affected by collisional relaxation, which is much stronger in the N-body simulations than in real galaxies. I will describe a novel Monte-Carlo  method that can efficiently deal with both collisional and collisionless dynamics, and with galaxy models having arbitrary shapes. I show that without relaxation, the final-parsec problem may be overcome only in triaxial galaxies. Axisymmetry is not enough, but even a moderate departure from axisymmetry is sufficient to keep the binary shrinking. The binary hardening rate is always substantially lower than the maximum possible, "full-loss-cone'' rate, and it decreases with time, but stellar-dynamical interactions are nevertheless able to drive the binary to coalescence on a timescale less than about one Gyr in any triaxial galaxy. I also discuss the evolution of the binary’s eccentricity.
 


2014-2015 Academic Year Scheduled Dates
Date Speaker Title
8/20/2014
Yasaman Yazdi
Firewall Phenomenology with Astrophysical Neutrinos
9/3/2014
Adrian Hamers
Secular dynamics of hierarchical quadruple systems
9/17/2014
Andy Lipnicky
Exploring the Effects of Dwarf Galaxies on HI Disks
9/19/2014
Dennis Bowen
Simulating Binary Black Holes in their Astrophysical Environment
9/24/2014
Triana Almeyda
Modeling the Reverberation Response of the Dusty Torus Emission from AGN
10/1/2014
Kristina Punzi
An Unbiased Radio Emission Line Survey of the Protoplanetary Disk Orbiting LkCa 15
10/29/2014
Michael Barbosu & Anthony Hennig
RIT Space Exploration (SPEX) Group and the Cubesat proposal
11/5/2014
Richard O'Shaughnessy
Understanding the precession and inspiral of binary black holes
11/21/2014
Laura Parker
Galaxy Evolution in the Group Environment 
12/3/2014
Sukanya Chakrabarti
Clustered Cepheid variables in Norma:  a distant dwarf galaxy in the plane of the Milky Way
1/28/2015
David Merritt
Gravitational Encounters in the Relativistic Regime
2/25/2015
Davide Lena
Gas kinematics within 400 pc from the nucleus of the Seyfert galaxy NGC 1386
3/4/2015
Joel Kastner
Young Stars Near the Sun: Investigating the Early Evolution of Stars & Planetary Systems
3/18/2015
Alan Parry
Wave Dark Matter and Galactic Dynamics
4/1/2015
Michael Richmond
What have we learned from the Rosetta mission so far?
4/15/2015
Kevin Cooke
Space Exploration After The Space Shuttle
4/29/2015 Marcel Pawlowski The ubiquity of co-orbiting satellite galaxy planes: ΛCDM's most severe small-scale problem?
5/20/2015 David Merritt Recent results on the final-parsec problem
TBD Manuela Campanelli Merging Black Holes in Astrophysics
 
Past Talks
2013-2014 Academic Year Astro Lunch Talks