Colloquia Archives

Meredith Hughes (Wesleyan University)
Thursday, April 23, 2015
3:45 p.m.
LGRT 1033
Title:
Circumstellar disks and planet formation with ALMA
Abstract:
Circumstellar disks provide the raw material and initial conditions for planet formation. Millimeter-wavelength interferometry is a powerful tool for studying gas and dust in planet-forming regions, and it is undergoing an immense leap in sophistication with the advent of the ALMA interferometer. I will discuss some ways in which we are using millimeter-wavelength interferometry to study the process of planet formation in circumstellar disks, with particular emphasis on the kinematics of turbulence in protoplanetary disks and the surprising presence of gas in debris disks around main-sequence stars.
Tracy Webb (McGill University)
Thursday, April 16, 2015
3:45 p.m.
LGRT 1033
Title:
The Growth of the Most Massive Galaxies in the Highest Density R
Abstract:
The most massive galaxies in the local universe reside at the centres of galaxy clusters. Often called Brightest Cluster Galaxies (BCGs), they exhibit, as a class, highly uniform properties and are distinct from the general galaxy population. This suggests formation processes which are themselves distinct from those which dominate in massive galaxies outside of cluster cores. The mass growth of BCGs is likely linked to the overall physics of hierarchical structure formation on galaxy cluster scales, including the fundamental processes of gas cooling, star formation, energy feedback and galaxy mergers, at the centers of giant dark matter halos. In this talk I will present new results from the largest study of high-redshift BCGs conducted to date, drawn from the SpARCS optical/NIR cluster survey. Using archival infrared data we show the star formation rate within BCGs increases to z~2, and can add as much mass to the BCG population as the previous standard model of growth by dry mergers. At low redshifts, and in X-ray/SZ selected clusters, the rare examples of star forming BCGs appear to be fed by large-scale cooling flows. However, the first of the SpARCS systems we have studied in detail, SpARCS1049, has revealed a very different phenomenon - a train-wreck of a galaxy merger at the center of the cluster. This is the first example of such a process in high-redshift cluster cores and may represent a new phase of BCG evolution, previously unaccounted for.
Pieter van Dokkum (Yale University)
Thursday, April 9, 2015
3:45 p.m.
LGRT 1033
Title:
A history of the dense cores of massive galaxies over the past
Abstract:
Owing to several large surveys with new instruments on HST we are now able to measure the basic properties of galaxies over most of cosmic history. This talk will highlight one such survey, 3D-HST, which has obtained spectra and images of many thousands of faint galaxies. I will also discuss the next step, that is, how to reconstruct the histories of different kinds of galaxies from this wealth of data. This reconstruction has now been done for galaxies like the Milky Way, enabling us to look at "baby pictures" of galaxies like our own.
Katja Poppenhaeger (CfA)
Thursday, April 2, 2015
3:45 p.m.
LGRT 1033
Title:
A high-energy view of exoplanets and their host stars
Abstract:
Many exoplanets orbit their host stars at close distances, with orbital periods of only a few days. For such systems, the magnetic activity of the planet-hosting star determines the high-energy environment of its exoplanet and is an important factor in understanding the exoplanetary evolution. X-ray and UV observations allow us to determine the high-energy input into the exoplanetary atmosphere, which is the main driver of planetary evaporation. X-ray emission is also directly connected to the stellar rotation; without external input of angular momentum, the star spins down over time due to magnetic braking. However, if there is tidal interaction between a star and its Hot Jupiter, the spin-down of the host star may not follow the usual age/rotation/activity relations. I will discuss recent X-ray and UV observations which provide insights into both the evaporation of close-in exoplanets and a possibly altered age-activity relationship for host stars of such planets.
Rob Simcoe (MIT)
Thursday, March 26, 2015
3:45 p.m.
LGRT 1033
Title:
Heavy Element Enrichment in Early Intergalactic and Circumgalact
Abstract:
Infrared photometric surveys are discovering numerous quasars at z > 6.5, enabling absorption investigations of neutral Hydrogen and its associated heavy elements at the tail end of the reionization epoch. I will describe the status of my group's ongoing IR and optical spectroscopic surveys targeting metal pollution in the first few Gyr. Beginning with a systematic study of absorption candidates for "cold flows" at z~3, I will move on to describe a 100-sightline survey of circumgalactic MgII pollution with the Magellan/FIRE spectrometer, extending prior optical measurements (restricted to z<2) out to z~6.5. I will also describe our latest constraints on the CIV mass density and intergalactic carbon enrichment at z = 4.5-6.5. Finally, I will outline our first attempt at measuring actual chemical abundances in the z > 7 universe, and discuss their significance for reionization and the formation of the first stars.
Beth Willman (Haverford)
Thursday, March 12, 2015
3:45 p.m.
LGRT 1033
Title:
Triumphs and tribulations of near-field cosmology with wide-fiel
Abstract:
Over the last decade, wide-field surveys have revolutionized our view of the Milky Way’s stellar halo and dwarf galaxy population. Much of this observational progress has been motivated by a series of apparent “crises” for our cosmological model: the missing satellites problem, too big to fail, and the apparent planar distribution of dwarf satellite galaxies. These challenges have effectively functioned as flashlights pointing us to interesting galaxy formation physics. I will highlight related observational progress in our understanding of galaxy formation using near-field observations. I will then focus on the limiting impacts of observational bias and ways that current and future surveys will be used to tackle these biases. In particular, I will present new predictions for the number of Milky Way dwarf galaxies expected to be discovered in DES and LSST, RR Lyrae stars as a tool to discover dwarf galaxies in previously unexplored territory, and the use of M giant stars to map the Milky Way’s halo beyond its virial radius.
Elizabeth Blanton (Boston University)
Thursday, March 5, 2015
3:45 p.m.
LGRT 1033
Title:
Extragalactic Jets as Probes of Clusters of Galaxies
Abstract:
I will present multi-wavelength (X-ray, optical, infrared, and radio) observations of clusters of galaxies, including in-depth study of nearby objects and a survey of distant systems. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes in the cores of the dominant cluster galaxies leading to AGN outbursts. This AGN feedback can reheat the gas, stopping cooling and large amounts of star formation. Most relaxed, cool core clusters host powerful AGN in their central galaxies and these AGN can significantly affect the distribution of e.g., temperature and abundance on cluster scales. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio jets and lobes, and sound wave propogation. Sloshing of the cluster gas, related to minor, off-center interactions with galaxy sub-clusters or groups also affects the distribution of temperature and abundance on large scales. This sloshing gas can interact with the AGN's radio-emitting jets and lobes causing them to bend. This bending is also found in AGN jets and lobes embedded in clusters undergoing major, head-on cluster, cluster mergers. Since this bending is a signature of interaction within clusters, bent, double-lobed AGN observed in the radio can be used as beacons for clusters of galaxies at high redshifts. I will describe our large sample of high-redshift, bent-double radio sources that were observed in the infrared with Spitzer and that have yielded approximately 200 new, distant clusters of galaxies with z > 0.7. These clusters will serve as important laboratories for studying galaxy evolution and cosmology.
Andrey Kravtsov (University of Chicago)
Thursday, February 26, 2015
3:45 p.m.
LGRT 1033
Title:
Order out of chaos: formation of galaxies in hierarchical univer
Abstract:
Galaxy formation is a complex, hierarchical, highly non-linear process, which involves gravitational collapse of dark matter and baryons, supersonic, highly compressible and turbulent flows of gas, star formation, stellar feedback, as well as heating, cooling, and chemical processes. All of these processes appear to be critically important in shaping properties of galaxies. At the same time, despite the apparent complexity of these processes and the ways they interact, observed properties of galaxies exhibit a number of striking regularities, such as tight correlations between galaxy sizes, masses, luminosities, and internal velocities and surprisingly tight correlations between properties of stars and gas in galaxies and the mass and extent of their parent halos dominated by dark matter. Existence of such correlations indicates that powerful processes operate to bring order out of chaos. In this talk I will discuss some insights based on the recent work aimed to understand this aspect of galaxy formation, focusing on some specific issues in how mass of galaxies and their host dark matter halos is assembled and in how thermodynamics processes of diffuse gas, star formation, and stellar feedback conspire to produce galaxies quite close to observed systems.
Jill Naiman (CfA)
Thursday, February 19, 2015
3:45 p.m.
LGRT 1033
Title:
Gas Retention and Accumulation in Dwarf Galaxies: Implications
Abstract:
The effective supply and retention of gas in shallow gravitational potentials is a problem with implications in a diverse set of astrophysical systems. In particular, the magnitude of gas flows into mature dwarf galaxies can have large impacts on the star formation histories in these systems. In this talk, computational techniques will be used to show how such such weakly bound gravitational structures might be able to accumulate gas effectively. The implications for star formation in dwarf galaxies after their incorporation into a larger host halo will be presented.
Blakesley Burkhart (CfA)
Thursday, February 12, 2015
3:45 p.m.
LGRT 1033
Title:
New Frontiers of Magnetized Turbulence in the Multiphase Interst
Abstract:
The current paradigm of the ISM is that it is a multiphase turbulent environment, with turbulence affecting many important processes. For the ISM this includes star formation, cosmic ray acceleration, and the evolution of structure in the diffuse ISM. This makes it important to study interstellar turbulence using the strengths of numerical studies combined with observational studies. I shall discuss progress that has been made in the development of new techniques for comparing observational data with numerical MHD simulations in the star forming molecular medium and in neutral gas as traced by 21 cm emission.
Brice Menard (JHU)
Thursday, February 5, 2015
3:45 p.m.
LGRT 1033
Title:
De-projecting astronomical surveys
Abstract:
Observations of the sky are inherently a 2-dimensional measurement of flux density on the sphere of the sky. For astrophysical studies, however, one usually needs the knowledge of 3d positions, for example to convert an angle into a physical scale or a brightness into a luminosity. In the context of extragalactic surveys, distance or redshift information is usually done with "photometric redshifts", which rely on strong assumptions and often lead to problematic estimates. In this talk I will how it is possible to instead use clustering measurements and infer redshifts for any type of extragalactic sources. I will show applications of this "clustering-redshift" technique to various datasets at UV, optical, IR and radio wavelengths, and show a number of surprises.
Anne Jaskot (Smith/UMass/Five College Astronomy Department)
Thursday, January 29, 2015
3:45 p.m.
LGRT 1033
Title:
HI, Stars, and Ionizing Photons: Gas Cycles and LyC Escape in Lo
Abstract:
Neutral hydrogen gas plays a key role in galaxy evolution, by both providing the raw material for star formation and responding to the resulting stellar feedback. Two samples of low-redshift starburst galaxies, ALFALFA H-alpha and the Green Peas, give new insights into the relationship between HI gas, star formation, and UV radiation. Using 565 starburst and non-starburst galaxies from the HI-selected ALFALFA H-alpha survey, I will analyze the role of the HI gas supply in driving high levels of star formation and discuss factors that may promote efficient HI to H2 conversion. With both ground-based and HST observations of the Green Pea galaxies, some of the most extreme low-mass starbursts in the nearby universe, I will focus on the propagation of ionizing radiation through the neutral gas. In particular, the Green Peas may be leaking ionizing radiation into the intergalactic medium and are therefore potential analogs of the galaxies responsible for cosmic reionization.
Josh Shiode, John N. Bahcall Public Policy Fellow (American Astronomical Society)
Thursday, January 22, 2015
3:45 p.m.
LGRT 1033
Title:
There's Government in Your Science
Abstract:
The majority of basic science research in the United States — including that in the astronomical sciences — is funded by the federal government. This is both good and bad. Good because there are a lot of resources available, though basic research funding is but a small fraction of the total federal budget. Bad because individual scientific projects, and the careers of the scientists involved, can be affected by political winds they would otherwise never feel. In this talk, I’ll try to convey a sense of those winds. I’ll focus on the process of policymaking and long-term trends relevant to the scientific enterprise, and we’ll explore how individual scientists and science advocates can play a role in the political and policymaking process.
Kaitlin Kratter (University of Arizona)
Thursday, December 11, 2014
3:45 p.m.
LGRT 1033
Title:
What can we learn from planets in binary systems?
Abstract:
Exoplanet surveys have revealed a surprising array of planetary systems hosted by binary stars. The diversity and architecture of these systems provide insight into the fundamentals of planet formation for a wide range of systems. Moreover, these planets provide an important final boundary condition for our models of star formation, and especially binary formation. I will review the statistics of these surprisingly un-exotic systems, describe the theoretical implications, and discuss the prospects for progress with observational facilities of the future.
Stephanie LaMassa (Yale University)
Thursday, December 4, 2014
3:45 p.m.
LGRT 1033
Title:
Discovering Rare AGN with the Stripe 82X X-ray Survey
Abstract:
Supermassive black holes (SMBHs) grow by accreting matter in a phase where they are observed as active galactic nuclei (AGN). In order to track the evolution of rare objects, such as AGN at high luminosity, which signal when the majority of black hole growth occurred, a large volume of the Universe has to be explored through wide area surveys. Until recently, no large area X-ray survey has existed, meaning that a key phase in SMBH growth and SMBH/galaxy co-evolution is missing: luminous obscured SMBH growth. To rectify this gap, I have begun a wide area X-ray survey in the Sloan Digital Sky Survey region Stripe 82 which contains a veritable treasure trove of multi-wavelength coverage, expediting follow-up of identified X-ray sources. In this talk, I will review the highlights of our first release of "Stripe 82X" which covers ~16.5 deg^2 with ~3300 X-ray sources identified. I will discuss our current ground-based follow-up campaigns to target interesting classes of AGN and will comment on what we expect to learn with the addition of 20 deg^2 awarded to our team in the current XMM-Newton observing cycle.
Mike Dunham (CfA)
Thursday, November 20, 2014
3:45 p.m.
LGRT 1033
Title:
The Evolution of Protostars: Assembling Stars from Dense Cores
Abstract:
Stars form from the gravitational collapse of dense molecular cloud cores. In the protostellar phase, mass accretes from the core onto a protostar, likely through an accretion disk, and it is during this phase that the initial masses of stars and the initial conditions for planet formation are set. Over the past decade, new observational capabilities have provided wide-field infrared and (sub)millimeter surveys of entire star-forming clouds along with interferometric images at very high angular resolution, giving an unprecedented view of the star formation process. In this talk I will review resulting advances in the field of protostellar evolution, focusing on observational constraints on the problem of how mass is transferred from dense cores to stars.
Nick Cowan (Amherst College)
Thursday, November 13, 2014
3:45 p.m.
LGRT 1033
Title:
Balancing the Radiation Budget of Short-Period Planets
Abstract:
What started as a trickle in the mid 1990’s is now a torrent, with over one thousand extrasolar planets currently known, and thousands of candidates awaiting confirmation. The study of exoplanets has already revolutionized our view of planet formation, and will soon do the same to our understanding of planetary atmospheres and interiors. Since we view them from the top-down, one of the first aspects of exoplanet atmospheres to be constrained is their thermal emission. By combining infrared emission measurements at a variety of orbital phases, we can infer a planet's Bond albedo, the efficiency of its day-night heat transport, and, in the case of planets subject to eccentricity seasons, its thermal inertia. Multi-wavelength emission measurements can also constrain a planetary atmosphere's composition and vertical temperature structure. Such inferences are particularly sensitive to the uncertainty in emission measurements, however, and the accuracy of eclipse measurements has typically been over-stated. Fortunately, improved analysis techniques and next-generation instruments should allow us to resolve outstanding questions about hot Jupiters, and to extend our methods to temperate terrestrial planets.
Houjun Mo (UMass)
Friday, November 7, 2014
3:45 p.m.
LGRT 1033
Title:
Star formation and stellar mass assembly histories in dark matte
Abstract:
TBA
Erik Tollerud (Yale University)
Thursday, November 6, 2014
3:45 p.m.
LGRT 1033
Title:
Local Dwarf Galaxies and Near-Field Cosmology in ΛCDM
Abstract:
Dwarf galaxies are a frontier for new discoveries in both galaxy formation and cosmology. I discuss work centered around connecting LCDM and its predictions to observations of dwarf galaxies at three different scales of "dwarf". I will discuss the Milky Way's satellites and both solutions and lingering troubles with their abundances and scalings. The strangest of these puzzles manifest in the bright dSphs, which seem to be under-dense relative to LCDM expectations. With this in mind, I describe results from a large spectroscopic survey of M31's dSph satellites searching for signs of similar puzzles. Finally, I describe searches for comparable satellites beyond the Local Group, and compare their abundances and properties to straightforward LCDM expectations.
Scott Chapman (Dalhousie University)
Thursday, October 30, 2014
3:45 p.m.
LGRT 1033
Title:
The role of ultra-luminous galaxies in galaxy formation and evol
Abstract:
I will provide an overview of ultra-luminous galaxies (L_IR>1012 Lsun) at high redshift, and the different roles and properties they appear to exhibit as a function of their luminosity. I will focus on the molecular gas properties of the galaxies as the crucial fuel available for star formation, emphasizing our recent work with ALMA and the IRAM Plateau-de-Bure, where we have studied galaxies preselected at various wavelengths, and conducted blind surveys for CO gas. I will conclude with very wide field surveys (SPT) that are uncovering the most extreme specimens of star forming galaxies in the universe, and point to future facilities like CCAT which will push the field to a new level of understanding.
Greg Stinson (MPIA)
Thursday, October 23, 2014
3:45 p.m.
LGRT 1033
Title:
A Critical Phase in Galaxy Formation
Abstract:
As galaxies grow and evolve, they go through a violent phase of their evolution where intense star formation drives outflows. I will examine this phase using cosmological galaxy formation simulations. The simulations show that starbursts and outflows have implications for many observed properties of galaxies including their gaseous halos, morphology, potential, and star formation history.
Laura Lopez (MIT)
Thursday, October 16, 2014
3:45 p.m.
LGRT 1033
Title:
Observational Assessment of Stellar Feedback in Star-Forming Reg
Abstract:
Stellar feedback has a profound influence in many astrophysical phenomena, yet it is often cited as one of the biggest uncertainties in star and galaxy formation models today. This uncertainty stems from a dearth of observational constraints as well as the great dynamic range between the small scales (<1 pc) over which feedback occurs and the large scales (>1 kpc) on which galaxies are shaped by that feedback. In this talk, I will show how multiwavelength observations can be used to overcome these challenges to assess the role of many stellar feedback mechanisms, including radiation, stellar winds, supernovae, and cosmic rays. I will present results from the application of these approaches to a variety of sources and discuss the implications regarding the dynamics of star-forming regions and the launching of galactic winds. Finally, I will highlight the exciting prospects of using current and upcoming facilities to explore feedback in diverse conditions.
Mario Livio (STScl)
Thursday, October 9, 2014
3:45 p.m.
LGRT 1033
Title:
Brilliant Blunders
Abstract:
Even the greatest scientists have made some serious blunders. "Brilliant Blunders" concerns the evolution of life on Earth, of the Earth itself, of stars, and of the universe as a whole. In this talk, I shall concentrate on and analyze major errors committed by such luminaries as Charles Darwin, Linus Pauling, and Albert Einstein. I will also scrutinize the various types of blunders and attempt to identify their causes. Most importantly, however, I'll argue that blunders are not only inevitable, ­but rather part and parcel of progress in science and other creative enterprises.
Andrew West (Boston University)
Thursday, October 2, 2014
3:45 p.m.
LGRT 1033
Title:
Stellar Underdogs: the Comeback of Low-mass Stars in the Era of
Abstract:
My primary goal of this colloquium is to demonstrate that we can do big science with little stars. M and L dwarfs are the smallest, coolest and least massive (main sequence) stars in the Galaxy. Yet despite their diminutive physical properties, low-mass stars make up ~70% of all of the stars in the Milky Way galaxy and have lifetimes that exceed trillions of years. Their dominance in the Galaxy make low-mass stars excellent tracers of both the structure and evolution of the local Milky Way. In addition, low-mass stars have intense stellar flares and strong magnetic fields that allow us to probe their interiors and may have important consequences for their space weather environments and the habitability of planets that orbit them. I will present results from the largest samples of low-mass stars ever assembled. The advent of large surveys such as the Sloan Digital Sky Survey (SDSS) has yielded photometric and spectroscopic catalogs of more than 100 million and 70,000 stars respectively. Specifically, I will highlight work that has used the unprecedented statistical power of surveys to examine the nature of stellar magnetic fields (and subsequent "magnetic activity") and stellar age, and how large samples of wide low-mass binaries can help us constrain evolutionary models of stars. In addition, I will highlight the confirmation of an age-rotation-activity relation that has come from a collaboration with the MEarth planet hunting team, show how IR excesses around low-mass dwarfs may give us insights into planet formation/evolution, and demonstrate how a large sample of M dwarfs has helped us map the three-dimensional distribution of dust in the local Galaxy.
Debra Fischer (Yale University)
Thursday, September 25, 2014
3:45 p.m.
LGRT 1033
Title:
The Search for 100 Earths
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.
Jeff Wagg (SKA)
Thursday, September 11, 2014
3:45 p.m.
LGRT 1033
Title:
From Exoplanets to Cosmic Dawn with the Square Kilometre Array
Abstract:
Building on the major scientific advances made by the current generation of cm and metre-wavelength telescopes, phase 1 of the Square Kilometre Array (SKA) will be the next global radio astronomy observatory. The SKA is being designed by more than 350 engineers and scientists from around the world, with the aim to begin early science operations in 2020. The SKA will answer fundamental questions related to the evolution of atomic Hydrogen in the Universe, from the present day back to the Cosmic Dawn, when the first galaxies began to form less than 200 Myr after the Big Bang. It will also conduct key tests of general relativity through surveys and timing of pulsars in our galaxy, and beyond. I will give an overview of some of the science drivers for the SKA, along with a description of the planned SKA telescopes and the sites that will host them.
Thaisa Storchi-Bergmann (Universidade Federal do Rio Grando do Sul)
Thursday, September 4, 2014
3:45 p.m.
LGRT 1033
Title:
Feeding & Feedback of Supermassive Black Holes tracing Co-evolut
Abstract:
A fundamental role is attributed to supermassive black holes (SMBH) and the feedback they generate in the evolution of galaxies. Cosmologial models that do not consider these feedback effects end up producing over-massive galaxies. I will present and discuss astronomical observations of feeding and feedback processes around SMBHs that occur when the SMBH is being fed in Active Galactic Nuclei (AGN). These observations comprise optical and near-infrared Integral Field Spectroscopy of the inner few hundred parsecs of nearby AGN host galaxies, and are intended to provide constraints to the feeding and feedback processes. I will discuss in particular results obtained by my group that reveal gas inflows along nuclear spirals and disks. The inflow rates are much larger than the AGN accretion rate, suggesting that the excess gas is depleted via formation of new stars that are indeed observed in many casas and can be interpreted as signatures of co-evolution of the host galaxy and its AGN. Gas outflows are prevalent among the highest luminosity AGN, with velocities ranging from a few up to ~1000 km/s and mass outflow rates of a few solar masses per year.
Andy Fruchter (STScI)
Thursday, May 1, 2014
3:45 p.m.
LGRT 1033
Title:
Refusing to Go Quietly: Gamma-Ray Bursts and their Progenitors
Abstract:
Gamma-ray bursts (GRBs) are the most brilliant objects in the universe. Some are initially bright enough to be seen by the unaided eye across a distance of billions of light years. Yet the majority of GRBs which are detected, the so-called long-soft GRBs (LGRBs) are, like most supernovae, produced by the collapse of a massive star. I will discuss the environmental conditions that appear to produce LGRBs, and what this tells us about their progenitor stars. I will also speak about the less frequently detected and even more poorly understood, "short-hard" GRBs (SGRBs), and present recent observations which appear to show a "kilonova" associated with SGRB 130603B. If this interpretation of the data is also supported by observations of future bursts, it will provide direct evidence that SGRBs are formed by the merger of compact objects, and give us an electromagnetic signature that could help locate sources of gravitational waves in the advanced-LIGO era.
Claudia Scarlata (Univ. of Minnesota)
Thursday, April 17, 2014
3:45 p.m.
LGRT 1033
Title:
The WISP survey: overview of recent results for galaxies in the
Abstract:
The WFC3 Infrared Spectroscopic Parallel Survey (WISP) is a large ( ~1000 orbits) HST program that uses WFC3 slitless spectroscopy to detect thousands of galaxies across a wide redshift range 0.3 < z < 2.3. I will present an overview of recent results on emission line galaxies, including a statistical determination of their dust extinction properties, the discovery of a new population of extremely strong emission-line dwarf galaxies, and the implication of the observed number counts for the EUCLID mission. I will also discuss the properties of passive galaxies at z∼1.5 derived from the combination of the WISP spectra with broad-band photometry from HST-UVIS and Spitzer images.
Arjun Dey (NOAO)
Thursday, April 10, 2014
3:45 p.m.
LGRT 1033
Title:
Lyman Alpha Emission and Galaxy Formation: An Observer's Perspec
Abstract:
Lyman alpha has long been used as a signpost of young galaxies in the distant Universe. My collaborators and I are engaged in ongoing searches for Lyman alpha emission at a range of redshifts (z~2-4), discovering both Lyman alpha "blobs" (giant, 100-kpc clouds of glowing, galaxy-forming gas) and much lower mass Lyman alpha emitters, which may be the building blocks of larger galaxies. I will also discuss some of the properties of the new blobs (one of which is a good candidate for an extremely low-metallicity galaxy forming environment) and report on using Lyman alpha as a tracer of protocluster environments at high redshift.I will also talk briefly about the DESI project planned for the Mayall telescope, a cost-effective dark energy project for this decade. I will describe the main scientific goals, the technical plan and the current status of this project.

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