Events Archive

Using Protoplanetary Disks to Weigh the Youngest Stars and Constrain The Earliest Stages of Stellar Evolution

Wed, Nov 4, 2015 at 3:00 pm

131A Campbell Hall

Ian Czekala (CfA)

Mass is the fundamental property that determines the evolutionary path of a star. In particular, the masses of young stars are of great relevance to many astrophysical problems, including star and planet formation. We have developed a novel approach that combines spatially resolved sub-millimeter spectral line imaging and optical/near-infrared high resolution spectroscopy to derive the …

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Subhalos in the real Universe: satellite galaxy-galaxy lensing

Tue, Nov 3, 2015 at 1:00 pm

131A Campbell Hall

Cristobal Sifon (Leiden)

I present galaxy-galaxy lensing measurements of the total masses of satellite galaxies in galaxy groups and clusters, obtained by combining high-quality imaging data with large spectroscopic galaxy catalogs. I focus on the overlap between the Kilo-Degree Survey (KiDS) and the Galaxy And Mass Assembly (GAMA) survey and present preliminary results on massive clusters from the Canadian Cluster …

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Collapse and Star Formation in Self-gravitating Turbulent Fluids

Mon, Nov 2, 2015 at 3:00 pm

131A Campbell Hall

Norm Murray (Toronto)

Observations of star forming regions in the Milky Way have established that stars form in large molecular clouds or GMCs. The spectral lines of these GMCs are usually interpreted as the signature of turbulent motion. The kinetic energy in the turbulence is similar to the gravitational binding energy of the GMC. Work over the last decade suggests that stars form in converging flows in this …

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Rotation and angular momentum transport in stars - hydrodynamic processes

Mon, Nov 2, 2015 at 12:00 pm

131A Campbell Hall

Andrea Caleo (Oxford)

The recent wealth of information on the internal rotation of the Sun (and other stars) has made the problem of understanding rotation profiles and angular momentum transport inside these structures prominent in stellar physics. I will review the observational data and explain which challenges are presented to the theorist. Among these is the problem of the spreading of the tachocline, the …

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Astrophysics of Molten Salt Breeder Reactors: Building a Nuclear Reactor Better than the Sun

Thu, Oct 29, 2015 at 4:00 pm

1 LeConte Hall

Frank Shu (UCSD)

Climate change is real, here, and potentially catastrophic in its effect. We argue that the scale of the transformation needed to mitigate climate change requires breakthroughs in current technologies, most importantly, in new forms of fission reactors that are:   (1) safe in their inherent design, (2) sustainable in terms of meeting future energy demand for several centuries as …

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Department Lunch Talk 10-29

Thu, Oct 29, 2015 at 12:30 pm

131A Campbell Hall

Jonathan Seising (UCSC)
Pete Williams (CfA)
Frank Shu (UCSD, [colloq. spkr.)

The Department Lunch Talk series is a weekly event that features three 20 minute talks presented mainly by local scientists of any level to present their work to a broad spectrum of the department and usually includes one short talk by the astronomy colloquium speaker of the day. Subjects can include personal scientific research, reporting on other work appearing in journals, education and public outreach efforts, science policy, and professional development issues. Continue reading for this week's talk titles.

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Galaxy Proto-clusters as an Interface Between Structure, Cluster, and Galaxy Formation

Tue, Oct 27, 2015 at 1:00 pm

131A Campbell Hall

Yi-Kuan Chiang (Austin)

Proto-clusters, the ancestor large-scale structures of present-day galaxy clusters, are ideal laboratories to study dark matter assembly, cosmic baryon cycle, galaxy growth, and environmental impact on galaxy evolution. We extract LCDM predictions for the physical properties and observational signatures of galaxy proto-clusters as a function of time and cluster mass. I will talk about …

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Cosmic-ray ionization and heating in molecular clouds

Mon, Oct 26, 2015 at 3:00 pm

131A Campbell Hall

Daniele Galli (INAF)

Low-energy cosmic rays are an important source of ionization for the interstellar medium, influencing its chemical, thermal and dynamical evolution. Available observational determinations of the cosmic-ray ionization rate in diffuse clouds and recent data from the Voyager I spacecraft support the existence of a significant flux of cosmic-ray nuclei and electrons below ~100 MeV. However, the …

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Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites.

Mon, Oct 26, 2015 at 12:00 pm

131A Campbell Hall

Coral Wheeler (UCI)

If LCDM is correct, then all dark matter halos hosting galaxies, from those hosting dwarfs to those hosting giant clusters, are filled with abundant substructure down to very low mass scales (<< 10^9 Msun). Specifically, even the dark matter halos of Local Group field dwarfs should be filled with subhalos, many of which should be fairly massive (~ 10^8 Msun), and thus are potential …

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Numerical Simulations of Black Hole Accretion

Thu, Oct 22, 2015 at 4:00 pm

1 LeConte Hall

Ramesh Narayan (CfA Harvard)

Accreting black holes are observed in a large variety of systems in astronomy: active galactic nuclei, X-ray binaries, tidal disruption events, gamma-ray bursts. While analytical one-dimensional models have been enormously useful for understanding several aspects of accretion physics, other aspects such as the formation of jets and winds are beyond the scope of …

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Department Lunch 10-22

Thu, Oct 22, 2015 at 12:30 pm

131A Campbell Hall

Jon Mauerhan (UCB)
Davide Martizzi (UCB)
Ramesh Narayan (Harvard)

The Department Lunch Talk series is a weekly event that features three 20 minute talks presented mainly by local scientists of any level to present their work to a broad spectrum of the department and usually includes one short talk by the astronomy colloquium speaker of the day. Subjects can include personal scientific research, reporting on other work appearing in journals, education and public outreach efforts, science policy, and professional development issues. Continue reading for this week's talk titles.

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CIPS Seminar 10-21

Wed, Oct 21, 2015 at 3:00 pm

131A Campbell Hall

Eric Nielsen (SETI/Stanford)
Michael Manga (UC Berkeley)

This weeks CIPS Seminar will feature two speakers (please continuing reading for complete abstracts and titles).

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Constraining Gravity at the Largest Scales through CMB Lensing and Galaxy Velocities

Tue, Oct 20, 2015 at 1:00 pm

131A Campbell Hall

Anthony Pullen, CMU

We discuss recent work exploring the use of CMB lensing to probe E_G, the ratio between curvature and velocity perturbations. This quantity is distinct for various gravity models, breaking the degeneracy in current cosmological probes of gravity and dark energy. While the lensing signal within E_G has traditionally been probed with galaxy-galaxy lensing, galaxy-CMB lensing is a more robust …

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The streams, disks, and jets from tidal disruption events

Mon, Oct 19, 2015 at 12:00 pm

131A Campbell Hall

Eric Coughlin (U of Colorado, Boulder)

When a star comes within a critical distance of a supermassive black hole, the tidal force exerted by the hole overwhelms the stellar self-gravity, which subsequently tears the star apart and creates a stream of tidally-shredded debris. Approximately half of this debris eventually returns to the black hole, forms an accretion disk and generates a highly luminous …

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Stardust: Analyses of cometary and interstellar dust in the laboratory

Sat, Oct 17, 2015 at 11:00 am

100 Genetics & Plant Biology Building

Andrew Westphal (UC Berkeley)

Stardust was the first spacecraft ever to bring back to Earth extraterrestrial materials from beyond the Moon. It was two missions in one spacecraft. Stardust returned the first samples from a known primitive solar system body, the Jupiter-family comet Wild 2. Stardust also carried a separate collector that was exposed the interstellar dust stream for 200 days before the encounter with the …

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