APRIL 21 - 25, 2014


11:00 am: Optical and Infrared Astronomy Division Seminar. "The X-ray Emission From Young Supernovae as a Probe of their Progenitors," Vikram Dwarkadas, University of Chicago. Pratt Conferencen Room.

Abstract: Even after several decades of study, the progenitor stars of supernovae (SNe) have proven difficult to identify. The identification of progenitors has generally been the purview of optical astronomy, aided in part by stellar evolution models. But observations at other wavelengths can also provide several hints about the progenitors. We have aggregated together data available in the literature, or analysed by us, to compute the X-ray lightcurves of almost all young SNe. We use these, coupled with analytical and numerical simulations, to investigate the SN expansion, the characteristics of the medium into which they are expanding, and the implications for their progenitors. We explore all SN types, with emphasis on Type IIP and Type IIn SNe. IIPs have the lowest X-ray luminosities, which is surprising given the high mass-loss rate, and low velocity, winds expected from their red supergiant (RSG) progenitors, and therefore the high density medium into which IIP SNe are expected to expand into. We show that the low X-ray luminosity sets a limit on the mass-loss rate, and thereby initial mass of a RSG star which can become a Type IIP progenitor. This initial mass limit, of about 19 solar masses, is consistent with that obtained via direct optical progenitor identification. IIns are observed to have high X-ray luminosities in general, but their light curves are very diverse, with some of them tending to fall off very steeply. We explore the implications of this behaviour.

1:00 pm: ITC Pizza Lunch Talk on Time Domain Astronomy. "Probing the High-z Universe with Long GRBs and the New Class of Ultra-long GRBs: Reality or Curiosity?" Prof. Carole Mundell, Liverpool John Moores University, Dr. Ryan Chornock and Timothy Laskar, CfA. Phillips Auditorium.

4:00 pm: ITAMP/HQOC Joint Quantum Sciences Seminar. "Out-of-Equilibrium Dynamics of Strongly Interacting Rydberg Gases in a Dissipative Environment," Igor Lesanovsky, University of Nottingham. Jefferson 250, Department of Physics, Harvard University.


4:00 pm: Colloquium. Bok Prize Lecture: "Star Formation and Molecular Gas in the First Three Billion Years," Dr. Dan Marrone, Department of Astronomy, Steward Observatory, University of Arizona. Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: In the first few Gyr of cosmic history, the bulk of the stellar mass was assembled under conditions of higher density and lower metallicity than we observe locally. While the most advanced optical/IR facilities have provided very detailed studies of galaxies at z~2-5 and detections of rare galaxies at the epoch of reionization, it continues to be extremely difficult to study the cool phase of the ISM from which their stars arise. Understanding this cool phase, and the star formation that it obscures, is crucial to improving our picture of galaxy formation. I will report on two different views of the cool ISM in the early universe. First, millimeter and submillimeter facilities have provided new samples of gravitationally lensed starburst galaxies at z > 3 that are exceptional targets for detailed study with ALMA. I will present the central findings of early-science ALMA studies of lensed galaxies identifies in the South Pole Telescope survey. Second, star formation in the more common but less luminous galaxies that fill the early universe is much more challenging to observe, at least for individual galaxies. I will describe our efforts to study the development of the molecular ISM through intensity mapping, which measures fluctuations in the aggregate signal from distant galaxies. I will present preliminary results from a demonstration experiment targeting z~3, and describe the DACOTA experiment that will sample galaxies at z~3 and z~7 simultaneously.


12:30 pm: Radio and Geoastronomy Division Lunch Talk. "The Formation and Growth of Massive Stars and Star Clusters," Cara Battersby, CfA. Room M-340, 160 Concord Avenue.

Abstract: Massive stars and star clusters have a profound effect on the life cycle of matter in the universe, yet their complicated, short-lived, and deeply embedded early lives have hampered our understanding of their formation and early evolution. Understanding their formation requires a multi-faceted approach; detailed observations at high resolution and large sample sizes through systematic surveys. I discuss high-resolution observations within a cloud which probe the environment just prior to and after the onset of massive star formation. By observing different evolutionary stages within a single cloud, we are able to directly compare their physical properties (column density and temperature) and evolutionary state. I expand upon this analysis by going to large scales using Galactic plane surveys (Herschel, Bolocam, Spitzer), again comparing star formation tracers directly with their physical properties. This yields a basic evolutionary sequence for massive star forming regions and an estimate of their lifetimes. I present evidence for large-scale collapse in one massive star-forming filament and suggest that such phenomena might be common. Finally, I discuss the beginnings of a survey with the SMA toward the most extreme site of star formation in our Galaxy; the Central Molecular Zone of the Milky Way.