Abstracts
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"Constraining Gas Flows in the Circumgalactic Medium with the HI Lyman Alpha Line"
Deep narrowband imaging has revealed that star forming galaxies are
surrounded by large (radius ~ 100 kpc) Lyman Alpha halos. The origin
of these halos is still disputed, but they likely encode information
on the distribution of cold gas around galaxies. Understanding this
so-called "circum-galactic" medium is vital to our understanding
of galaxy formation and evolution. I will present radiative transfer
calculations of Lyman Alpha photons propagating through clumpy, dusty,
large scale outflows, and will explore whether we can quantitatively
explain the Lyman Alpha halos that have been observed around Lyman
Break Galaxies (LBGs). These calculations show that Lyman Alpha
emission line halos around LBGs-and star forming galaxies in general-
provide valuable constraints on the cold gas distribution & kinematics
in their circumgalactic medium, and that these constraints nicely
complement those obtained from absorption line studies alone. I will
also discuss why the propagation of Lyman Alpha photons through
*small* scale outflows can affect the large scale clustering of Lyman
alpha emitting galaxies. HETDEX is therefore expected to provide
unique constraints on gas flows in and around galaxies. |
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"Protoplanetary Migration in Gaseous Disks"
Forming planets experience a strong tidal interaction with the gaseous protoplanetary disk in which they are embedded.
This interaction drives in particular a radial migration of the planet, so that its orbit may shrink or expand by up to two
orders of magnitude over the disk lifetime. Migration is therefore a process of utter importance for the formation of planetary
systems. I will review the different types of migration studied thus far: the type I migration of low mass planets, the type II
migration of giant planets that carve a gap in the protoplanetary disk, the runaway or type III migration of subgiant planets
in massive protoplanetary disks, and the migration experienced by low and intermediate mass objects in disks invaded
by MHD turbulence. I will put special emphasis on the dynamics of the coorbital region and on the corotation torque, which
has been the subject of intense research in the last years, and I will show how the thermodynamics of the disk has a strong
impact on this torque, with important consequences for planetary migration scenarios. |
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"Cosmic Infrared Background and New Cosmological Populations"
Cosmic infrared background (CIB) is produced by emissions from luminous objects spanning the entire history of the Universe including from sources, such as first stars, which are inaccessible to individual telescopic studies. CIB fluctuations, in particular, can be more readily discerned than the actual mean level allowing to overcome the significant Galactic and Solar system foregrounds at NIR wavelengths. I will report on the recent measurements of the CIB fluctuations at near-IR using deep exposure data obtained by the Spitzer Space Telescope. Previous measurements by our group out to scales as large as ~5' had seen the first indication of excess fluctuations above those expected from ordinary galaxies. Recently, these have been extended to sub-degree scales using new data obtained in the course of the 2,000+ hour Spitzer Extended Deep Survey. I will report these new observations, the methods to robustly uncover CIB fluctuations there and the implications of the measurement in isolating new cosmological populations, such as residing during first stars epochs. |
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"Exploring New Worlds: Imaging and Phase Mapping of Exoplanets and Brown Dwarfs"
High-contrast imaging and follow-up spectroscopy enable the detection and characterization
of medium-to-large separation giant exoplanets that are inaccessible to other exoplanet detection
techniques. I will review our recent and ongoing surveys for giant planets and discuss the importance
of detections, including the constraints these place on the properties of ultracool atmospheres and on
planet formation models.
The outstanding challenge in interpreting ultracool atmospheres of exoplanets and brown dwarfs remains
the formation and properties of cloud layers. I will show an exciting new technique that can complement
photometry and spectroscopy by providing spatially resolved information on these atmospheres.
Phase-mapping can provide spatially and spectrally resolved (2D) maps of rotating ultra-cool objects. I will show results from ongoing HST, Spitzer, and VLT programs that apply this technique to brown dwarfs and exoplanets. |
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"Young Spectroscopic Binaries: the Ordinary, the New, and the Unusual" In his review of Alan Batten’s “Binary and Multiple Systems of Stars”, Ian Roxburgh wrote “The evolutionary career of a star depends primarily upon its mass and stellar masses are obtained from observations of double stars.” For stars <10 Myr old, only about a dozen have measured masses, and many of those are highly uncertain. T Tauri spectroscopic binaries (SBs) are invaluable targets not only for the determination of young star masses, but also as precise probes for understanding binary star formation, a process responsible for at least 50% of all stars. Yet for only a few dozen of these systems have even the most basic measurements been made. I will describe my long-term program to measure mass ratios and masses of young SBs and will show some recent results from new candidate SBs, run-of-the-mill SBs, and a few challenging and baffling systems. |
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"Constraining Dark Matter"
Astrophysical and cosmological observations provide
compelling evidence for the existence of dark matter in the universe,
but its particle physics nature remains mysterious. In this talk, I
will discuss how hardron colliders and neutron stars can help us
understand dark matter properties. Using an effective field theory
approach, we show that mono-jet+missing energy searches at the
Tevatron and LHC can provide a probe of dark matter, which is
complementary to direct detection experiments, and in some cases the
colliders provide an even stronger constraint. Stellar systems are
natural laboratories
for exploring dark matter. We show dark matter particles accumulated
in old neutron stars can form mini black holes and lead to the
destruction of host stars. The observation of old neutron stars
actually excludes a class of dark matter models. In this talk, I will
also talk about self-interacting dark matter. |
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"The First Billion Years of our Universe"
A number of key facts and physical processes that have
shaped the subsequent evolution of our Universe took place within
a billion years from the Big Bang. Among these the first stars,
galaxies and black holes are unanimously considered as cutting-edge
unsolved problems in Cosmology. I will review the present status
of the research and indicate a few possible ways to make progress. |
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