MIT Astrophysics Colloquia - Fall 2014

Tuesdays at 4:00 PM in the Marlar Lounge, Room 37-252
MIT Kavli Institute for Astrophysics and Space Research
70 Vassar Street, Cambridge, MA
(unless location otherwise noted)
Refreshments are served at 3:45 PM.

Sponsored by
the Astrophysics Division of the MIT Department of Physics and
the MIT Kavli Institute for Astrophysics and Space Research.

Tuesday Sep 9:
The Search for 100 Earths
Debra Fischer
Host: Amaury Triaud

Abstract: The search for exoplanets is motivated by the question of whether life exists elsewhere. This drives our interest in the detection of planets that are similar to our own world: rocky planets with the potential for liquid surface water and plate tectonics; worlds that might harbor life that we can recognize. Importantly, we will need to discover not just a few, but hundreds of these worlds to eventually gain a statistical understanding of whether life is rare, common, or ubiquitous and ground-based telescopes offer an ideal platform for carrying out decade-long surveys. It is critical for follow-up studies (imaging, atmospheric studies) that these planets orbit nearby stars. In this talk, I will discuss how we plan to take what we've learned and push on to the next frontier: our plans for a next generation spectrograph, EXPRES, to carry out a search 100 Earths with the Discovery Channel Telescope.

Tuesday Sep 16:
LSST: Entering the Era of Petascale Optical Astronomy
Mario Juric
LSST/University of Washington
Host: TBD

Abstract: The Large Synoptic Survey Telescope (LSST; is a planned, large-aperture, wide-field, ground-based telescope that will survey half the sky every few nights in six optical bands from 320 to 1050 nm. It will explore a wide range of astrophysical questions, ranging from discovering “killer” asteroids, to examining the nature of dark energy. The LSST will produce on average 15 terabytes of data per night, yielding an (uncompressed) data set of over 100 petabytes at the end of its 10-year mission. Dedicated HPC facilities will process the image data in near real time, with full-dataset reprocessings on annual scale. A sophisticated data management system will enable database queries from individual users, as well as computationally intensive scientific investigations that utilize the entire data set. In this talk, I will review the science case for LSST and what LSST will deliver once operational. I will focus on the data products and management system, highlighting a number of differences and novel approaches compared to previous surveys. More generally, I will discuss implications of petascale data sets on astronomy in the 2020s and ways in which the community, both theorists and observers, can prepare to make the best use of them.

Tuesday Sep 23:
Galaxies on FIRE: Stellar Feedback and Galaxy Evolution
Dusan Keres
UC San Diego
Host: Paul Torrey

Abstract: Galaxies grow through accretion of gas and mergers in their complex cosmological environment. However, this growth needs to be regulated. Without additional "feedback” processes modeled galaxies end up too massive when compared to observed galaxies. I will present new cosmological simulations in FIRE project in which we have implemented physical feedback model from massive stars in the form of radiation pressure, stellar winds, supernovae and photo-ionization on local scales within the resolved interstellar medium. Non-linear interaction of these mechanisms regulates the structure of the inster-stellar medium and galactic star formation and drives large scale galactic outflows. With the energy and momentum input from the standard population synthesis models our simulations produce galaxies with realistic stellar masses and star formation histories. During their evolution galaxies undergo episodic star formation and blow powerful galactic winds that remove galactic gas, interact with the circum-galactic medium and change properties of dark matter halos. I will discuss recent results from FIRE simulations, advantages of our physical feedback model with respect to previous sub-grid implementations and current limitations and future improvements in models of galaxy formation.

Tuesday Sep 30:
Rattle & Shine: Compact Binary Coalescences and Their Multiple Signals
Luis Lehner
Perimeter Institute
Host: Scott Hughes

Abstract: The coalescence of a compact binary system produces among strongest gravitational wave signals and represents a key source for the near future detection of gravitational waves. Such systems should also produce powerful electromagnetic emissions as well as neutrinos. This talk with discuss theoretical efforts towards predicting different signatures from these systems and their connection with current and near future observations.

Tuesday Oct 7:
Flavor-Mixed Dark Matter
Mikhail Medvedev
University of Kansas
Host: TBD

Abstract: The nature of dark matter is unknown. A number of dark matter candidates are quantum flavor-mixed particles but this property has never been accounted for in cosmology. In this talk, we first discuss an interesting and rather counter-intuitive property of non-relativistic flavor-mixed particles called "quantum evaporation" -- a quantum effect, which is not related to flavor oscillations, particle decay, tunneling or other well-known processes. Particularly, we will show that a mixed particle confined in a gravitational potential and scattering off other particles from time to time, can gradually and irreversibly escape from it without extra energy supply. Furthermore, we discuss how this effect alters the structure formation in cosmology with multi-component mixed dark matter. We demonstrate, from the first principles via extensive N-body cosmological simulations, that such a dark matter model agrees with observational data at all scales, in contrast to the conventional LambdaCDM. Substantial reduction of substructure and flattening of density profiles in the centers of dark matter halos found in simulations can simultaneously resolve several outstanding puzzles of modern cosmology. Finally, we discuss the predictions of the model for direct and indirect detection dark matter experiments.

Tuesday Oct 14:
Astrophysical Feedback: Where Do Galaxies End and the IGM Begins?
Michael Shull
University of Colorado at Boulder
Host: TBD

Abstract: Our current view of galaxies considers them as systems of stars and gas embedded in extended halos of dark matter, much of it formed by the infall of smaller systems at earlier times. Star formation within galaxies affects the surrounding gas through primary forms of astrophysical feedback (mass, energy, radiation, metals). Both semantic and physical issues remain. Are the edges of galaxies defined by gravity or by gas outflows? When does gas cease to be the circumgalactic medium (CGM) and become part of the intergalactic medium (IGM)? I will discuss observational and theoretical work relevant to galaxy halos, IGM metallicity evolution, and CGM/IGM studies with the Cosmic Origins Spectrograph on the Hubble Space Telescope. As cosmological simulations become more advanced, their prescriptions for feedback from quasars and star-forming galaxies will need more sophistication in how they treat the injection of mass, heavy elements, ionizing radiation, and energy.

Tuesday Oct 21:
Gaspar Bakos
Host: Joshua Winn


Tuesday Oct 28:
Planetary Systems in 4D
Rebekah Dawson
UC Berkeley
Host: Joshua Winn


Tuesday Nov 4:
Dan Hooper
Fermilab / University of Chicago


Tuesday Nov 11:

Tuesday Nov 18:
The Local Universe as a Cosmology Laboratory
Mike Boylan-Kolchin
University of Maryland
Host: TBD


Tuesday Nov 25:
Observational Cosmology in the Milky Way's Backyard
Beth Willman
Haverford College
Host: TBD

Abstract: The ultra-faint dwarf galaxies discovered around the Milky Way and M31 include objects with less than one millionth of the Milky Way's own luminosity. The detailed properties of these puny satellites, as well as the remnants thereof, are being used to test dark matter+galaxy formation models. To fully exploit the Milky Way's halo to test such models requires a stellar halo map that is as complete and unbiased as possible. I will discuss how wide-field surveys (such as UKIDSS, DES, and LSST) will contribute to mapping the Milky Way out to its virial radius. I will focus on efforts to learn about ultra-faint dwarf galaxies and their relationship with dark matter halos, and early results from a program to map the Milky Way to its outermost regions using M giant stars.

Tuesday Dec 2:
Self-regulated Star Formation: From Radiation-dominated Clouds to Supernova-dominated Galaxies
Eve Ostriker
Host: TBD


Tuesday Dec 9:
Binary and Planetary Systems
Kaitlin Kratter
University of Arizona
Host: TBD


This page is maintained by Mark Vogelsberger