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Event
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Listing of Talk Abstracts
| Galaxy Formation and Evolution at z>3
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| Dr.
Rychard Bouwens (UC Santa Cruz) |
| Studying the formation and evolution at very high redshifts (z>3) is
compelling because of the extraordinarily dramatic changes occurring
in the universe at these early times. Not only were the halos of the
first L* and sub-L* galaxies just being assembled then, but the
universe was reionized and the properties of stars changed due to
infusion of the universe with metals. As a result of coordinated
efforts from both space and ground based observatories, great progress
has been made over the last few years to understand the early
formation and evolution of galaxies. Estimates of the luminosity
functions (LFs), star formation rate densities, stellar mass
densities, dust extinction, and surface brightnesses are now available
from these data all the way out to z~8 (700 million years after the
Big Bang). These findings give us clues as to what galaxies may look
like at even higher redshifts, at lower luminosities, and at higher
resolution -- and which provide a guide to future inquiries. In my
presentation, I provide a perspective on some of the most important
questions we will want to answer over the next 20 years and the
observational facilities we will require to address them.
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| The History of Star Formation in Galaxies |
| Dr.
Thomas Brown (STScI) |
| If we are to develop a comprehensive and predictive theory of galaxy formation and evolution, it is essential that we obtain an accurate assessment of how and when galaxies assemble their stellar populations, and how this assembly varies with environment. There is strong observational support for the hierarchical assembly of galaxies, but by definition the dwarf galaxies we see today are not the same as the dwarf galaxies and proto-galaxies that were disrupted during the assembly. Our only insight into those disrupted building blocks comes from sifting through the resolved field populations of the surviving giant galaxies to reconstruct the star formation history, chemical evolution, and kinematics of their various structures. To obtain the detailed distribution of stellar ages and metallicities over the entire life of a galaxy, one needs multi-band photometry reaching solar-luminosity main sequence stars. The Hubble Space Telescope can obtain such data in the outskirts of Local Group galaxies. To perform these essential studies for a fair sample of the Local Universe will require observational capabilities that allow us to extend the study of resolved stellar populations to much larger galaxy samples that span the full range of galaxy morphologies, while also enabling the study of the more crowded regions of relatively nearby galaxies. With such capabilities in hand, we will reveal the detailed history of star formation and chemical evolution in the universe. |
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| Stellar Imager (SI) - Observing the UV/Optical Universe in High Definition |
| Dr.
Kenneth Carpenter (NASA-GSFC) |
| Stellar Imager (SI) is a space-based, UV/Optical Interferometer
(UVOI) with over 200x the resolution of HST. It will enable 0.1
milli-arcsec spectral imaging of stellar surfaces and the
Universe in general and open an enormous new "discovery space"
for Astrophysics with its combination of high angular
resolution, dynamic imaging, and spectral energy resolution.
SI's goal is to study the role of magnetism in the Universe and
revolutionize our understanding of: 1) Solar/Stellar Magnetic
Activity and their impact on Space Weather, Planetary Climates,
and Life, 2) Magnetic and Accretion Processes and their roles
in the Origin & Evolution of Structure and in the Transport of
Matter throughout the Universe, 3) the close-in structure of
Active Galactic Nuclei and their winds, and 4) Exo-Solar Planet
Transits and Disks.
The SI mission is targeted for the mid 2020's - thus
significant technology development in the upcoming decade is
critical to enabling it and future space-based sparse aperture
telescope and distributed spacecraft missions. The key
technology needs include: 1) precision formation flying of many
spacecraft, 2) precision metrology over km-scales, 3)
closed-loop control of many-element, sparse optical arrays, 4)
staged-control systems with very high dynamic ranges (nm to
km-scale). It is critical that the importance of timely
development of these capabilities is called out in the upcoming
Astrophysics and Heliophysics Decadal Surveys, to enable the
flight of such missions in the following decade.
SI is an implementation of the UVOI in the 2006 Astrophysics Strategic
Plan and a "Landmark/Discovery Mission" in the 2005 Heliophysics
Roadmap. It is a NASA Vision Mission ("NASA Space Science Vision
Missions" (2008), ed. M. Allen) and has also been recommended
for further study in the 2008 NRC interim report on missions
potentially enabled/enhanced by an Ares V launch, although the
baseline mission design can be launched using the existing Delta IV
Heavy vehicle.
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| The New Worlds Observer: Direct Imaging and Spectroscopy of Planetary Systems |
| Prof.
Webster Cash (University of Colorado) |
| The New Worlds Observer is nearing the end of its ASMCS study. We primarily looked at a 50m diameter starshade flying about 80,000km from a 4m UVOIR observatory. This architecture will support observations of exoplanets to an Inner Working angle of .062 arcsec in the near IR and as low as .040 arcsec in the blue. This will allow for the discovery of dozens of Earth-like planets in a five year mission. Furthermore, high quality spectra will be taken of each planet at the time of discovery. These spectra will tell us their true natures. Over 70% of the observing time on the telescope will be available for general astrophysics while the starshade is in transit between targets.
We have shown that the starshade is an extendable technology, suitable for use with telescopes as small as 0.5m and as high as 16m. The starshade removes all special design constraints on the telescope, so it may be optimized for General Astronomy. The technology for starshades exists today and is in need of an aggressive program of demonstration and testing.
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| Extrasolar Planetary Imaging Coronagraph (EPIC) |
| Dr.
Mark Clampin (NASA/GSFC) |
| EPIC is an Exoplanet Probe class mission designed to provide insight into the physical nature of planets in other solar systems, and the architecture of the solar systems. EPIC will deliver images of planets and dust structures in nearby solar systems, and low resolution spectra of the gas giant planets in those systems. The Extrasolar Imaging Planetary Coronagraph (EPIC) is a 1.65-m telescope employing a visible nulling coronagraph (VNC) to deliver high-contrast images of extrasolar systems. The VNC features an inner working angle of 2lambda/D (125 mas), and offers a balance between performance and ease of implementation. The EPIC mission will be launched into a drift-away orbit with a five-year mission lifetime. |
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| Star Formation and Stellar Populations |
| Julianne Dalcanton (University of Washington - Department of Astronomy) |
| Astronomers have well-deserved confidence in their ability to predict
the properties of single stellar populations as a function of age and
metallicity. As a result, observations of complex stellar populations
can potentially be untangled to derive the past history of star
formation and metal enrichment, over megayear to gigayear timescales.
These analyses can be undertaken on any physical scale over which one
expects coherence of the underlying stars, for the timescale of
interest (i.e. spatial variations in recent star formation can be
analyzed on the scale of 10's of parsecs, while spatial variations in
ancient stellar populations can be analyzed on kiloparsec scales).
Thus, stellar populations offer a generic tool for tagging the ages and
metallicities of stellar structures. Among the many possible
applications are: (1) star formation and enrichment histories of
galaxies, as a function of position within the galaxy
(e.g. propagation of spiral arms, radial build-up of disks, vertical
heating of disks, etc); (2) direct measurement of the IMF as a
function of environment; (3) constraints on models of mass-loss in
evolving stars, which are critical for enrichment of galaxies and the
IGM; (4) derivation of past feedback into the ISM, from constraints on
the past SN energy input; and (5) identification of the sources of
transients identified with Pan-STARRS/LSST.
Such stellar population studies require that the PSFs of individual
stars are not completely blended together. This "crowding" currently
limits HST stellar population studies to structures fainter than the
Freeman disk surface brightness, at distances of less than ~4 Mpc.
These limits rule out studies within galaxy bulges, and preclude studies
of representative samples of L* galaxies. Reducing the effects of
crowding can be achieved (1) by using high angular resolution
observations; (2) by observing low surface brightness regions; (3) by
observing nearby galaxies; (4) by focusing on brighter stars. While
ample science is possible with options 2-4, option 1 opens the largest
scientific terrain. |
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| Galaxy Formation & Evolution between 1
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| Prof.
Mauro Giavalisco (University of Massachusetts Amherst) |
| ABSTRACT Galaxies undergo a period of profound evolution during the
cosmic epoch between redshift z~1 and z~3, when the star-formation
activity is at its peak, the mass in stars grows by over an order of
magnitude and the Hubble Sequence is established. This is a key epoch to
target if ones wants to understand the physics of galaxy evolution and
how modern galaxies came into place. We argue that ultra-sensitive
UV/Optical spectroscopy from space will give us the ability to
characterize the gravitational environment of galaxies
and the complex interplay between star formation and gas accretion and
feedback during this key cosmic epoch. By replacing QSO with distant
blue galaxies as light beacons, the next generation of UV/Optical
space-based spectrographs will allow us to exploit the exquisite
sensitivity of gaseous absorption systems in tracing the dynamics,
energetics and chemistry of the halo-galaxy-gas systems with high
spatial sampling and without the bias inherent in light-emitting
sources. This will provide one of the most powerful test of our
fundamental ideas on the structure of galaxies and their evolution.
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| Pupil Mapping Exoplanet Coronagraphic Observer |
| Olivier Guyon (University of Arizona / Subaru Telescope) |
| The Pupil-mapping Exoplanet Coronagraphic Observer (PECO) mission concept is a probe scale 1.4-m off-axis space-based coronagraphic telescope to both image and characterize extra-solar planetary systems at optical wavelengths. PECO delivers 1e-10 contrast at 2l/D separation (0.15") using a high-performance Phase-Induced Amplitude Apodization coronagraph (PIAA). The PIAA coronagraph remaps the telescope pupil and uses nearly all of the light coming into the aperture to achieve the full diffraction-limited resolution of the unvignetted aperture. This new coronagraphic approach offers optimal science return for the aperture size. PECO can therefore address some of the key science goals of previous mission designs that had planned to use larger telescopes but with less efficient coronagraphs (e.g., TPF-FB1). Most importantly, our study shows that detection and characterization (low resolution spectroscopy) of planets as small as Earth in the habitable zones of nearby stars is possible even with PECO’s small 1.4-m aperture. In addition to the use of the high performance PIAA coronagraph, PECO achieves its high sensitivity by simultaneously collecting all photons from 400nm to 900 nm wavelength in 16 science bands and devoting a large amount of exposure time and many revisits to a select number of high-priority targets. |
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| Future Scientific Directions for UVOIR Studies within the Solar System |
| Dr.
Heidi Hammel (Space Science Institute) |
| Within our Solar System, UVOIR observations from ground- and space-based telescopes provide unique data that complement planetary missions. In this talk, I will outline the Big Questions we are exploring in planetary astronomy, and briefly review some of the more stunning and surprising telescopic results from the past decade. This will set the stage for the future scientific directions of UVOIR studies. I will end with a summary of the anticipated requirements for UVOIR Solar System observations in the future. |
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| Technology for Future UVOIR Space-based Observatories |
| Dr.
T. Tupper Hyde (NASA) |
| Technologies to be developed in the coming decade support many proposed mission concepts for UVOIR space-based observatories. The Advanced Technology Large Aperture Space Telescope (ATLAST) is a 8-16 meter UVIOR observatory at L2 for general astrophysics and exoplanet imaging. Other concepts (ACCESS, EPIC, PECO, DAVINCI, NWO, THEIA, USO, SI) benefit from the same technology needed for ATLAST. This presentation outlines a 6 to 9 year roadmap for development of UVOIR telescopes, instruments, and starlight suppression. |
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| Unraveling the dark side of the Universe: probing dark matter and dark energy |
| Priya Natarajan (Yale) |
| The energy budget of our Universe is dominated by dark energy and dark matter. While we have tantalizing observational evidence for both dark matter and dark energy, their essential nature remains elusive. Several powerful techniques are currently available to probe dark matter and dark energy. While I will focus primarily on gravitational lensing techniques that utilize observations in the strong and weak lensing regimes over a range of physical scales: from galaxy scales to cluster to cosmic scales to constrain dark matter and dark energy models. I will also discuss baryon acoustic oscillations as a cosmological probe. A brief summary of the current status of constraints from these methods and their limitations will be presented. The significant advantages of space based observations for exploiting gravitational lensing combining the UV, optical and NIR will be discussed with a view to defining optimal design specifications for future space facilities. |
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| Advanced Technology Large-Aperture Space Telescope |
| Dr.
Marc Postman (STScI) |
| Modern observational astrophysics is a photon-limited field. We know paradigm-shifting discoveries are waiting to be made in the 2010 – 2030 era but these will require ever more capable instruments and facilities. In particular, in the fields of exosolar planet characterization, star and galaxy formation and evolution, the next
big steps require making observations at high angular resolution of sources with flux densities from a few to tens of anoJanskys. The key photometric and spectroscopic signatures that will, for example, enable the search for life in the universe or provide the foundation for a comprehensive theory of star formation or enable direct
measurements of interactions between galaxies and the cosmic web of baryonic and dark matter lie in the wavelength range 0.1 – 2.5 microns. The Advanced Technology Large-Aperture Space Telescope (ATLAST) is the next generation UVOIR space observatory with a primary mirror diameter in the 8-m to 16-m range that will allow us to perform all of these challenging observations. |
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| The Future of Galactic Stellar and Interstellar Astrophysics in the UV
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| Seth Redfield (Wesleyan University) |
| The previous generation of high-resolution UV spectrographs provided new and exciting glimpses into the nature of stars and gas in our local galactic neighborhood. This is the same volume of space which is home to almost all known exoplanets, resolved circumstellar disks at the final stages of planet formation, and the nearest low-mass star forming regions. It is also the same volume of space in which long term future missions (e.g., SIM and TPF) will be observing Earth-like exoplanets around nearby stars. In the near term future, significant progress in this volume will be made in understanding star and planet formation (e.g., Herschel, ALMA, JWST), finding and characterizing exoplanets (e.g., Kepler, JWST), and examining our planetary relationship with our local star and interstellar medium (e.g., IBEX, SDO). This work will focus attention onto the direct immediate and historical relationship between specific exoplanets and their parent stars (e.g., how dynamic stellar processes may influence habitability) and their nearest interstellar environment (e.g., how transitioning from a dense interstellar cloud and/or crowded stellar field influences exoplanetary properties). I will summarize the necessity of high-resolution UV spectra to address these and other key questions that are likely to arise in future work on stars and gas in our local galactic vicinity. |
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| Galaxy Evolution since z ~ 1 |
| Prof.
David Schiminovich (Columbia University) |
| The past two decades have seen tremendous advances in our understanding of galaxy evolution from the end of the dark ages through to the present day. Furthermore, galaxies continue to be useful as cosmological probes and as tracers of dark matter. In this talk I briefly describe many observational and theoretical successes---and a few surprises---that have resulted in a detailed framework for understanding the build-up and growth of structure and stellar mass in galaxies over nearly half of the age of the universe. I'll devote the rest of the talk to several of the essential (especially "gastrophysical") questions facing us over the next twenty years and our prospects for answering them.
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| The Baryonic Structure Probe |
| Dr.
Ken Sembach (STScI) |
| Our understanding of the physics behind the evolution of the cosmic
web is becoming more refined as numerical simulations and
measurements of the distribution of galaxies mature. Almost half of
the "normal" (non-dark) matter within large-scale structures in the
present-day Universe is believed to be composed of material that has
been shock heated to 5 < log T(K) < 7 during gravitational collapse.
Observations to determine the amount and organization of this
material in space are still primitive, owing to the extreme faintness
of the emission fluxes and the limited sensitivity of current
observatories. The Baryonic Structure Probe will advance our
understanding of the cosmic web, the processes that produce and
influence its structure, its effects on the formation and evolution
of galaxies, and its relationship to dark matter by obtaining
spectral images of the cosmic web emission.
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| Evolution of the IGM and Chemical Abundances |
| Dr.
Michael Shull (University of Colorado) |
| One of the most important legacies of space-based UV spectrographs
(FUSE, HST/STIS) is a large catalog of high-resolution spectra of AGN
sight lines. I will present results from a survey (Danforth & Shull
2008, 2009) of 650 H I absorption systems in the intergalactic medium
(IGM) at redshifts z < 0.4. These absorbers lie along 30 sight lines
spanning a total redshift pathlength Delta z = 5.27, the largest survey to date until the installation of the Cosmic Origins Spectrograph (COS), which will increase these numbers ten-fold. We also detect numerous metal-line systems, including 100 highly-ionized systems (O VI, N V) thought to trace warm-hot material (T > 10^5 K) and 70 lower-ionization absorbers (C III, C IV, Si III, Si IV, Fe III) that probe metal-enriched photoionized gas associated kinematically with the H I (Ly-alpha) systems.
The unprecedented size and breadth of this survey, and a much larger
QSO Absorption-Line Legacy Survey planned with COS, will enable us to
conduct several astrophysical experiments:
(1) Derive statistical metallicities for the low-z IGM, a baseline
for comparison with O VI, C IV, Si IV measurements at z = 2-6 and
a test of metallicity and ionization evolution over cosmic time.
(2) Use adjacent ions (Si III/IV, C III/IV) to constrain the ionizing
radiation field, independent of metallicity assumptions;
(3) Investigate the multiphase nature of absorption systems, to test
predictions of large-scale structure formation and galactic outflows;
(4) Constrain absorber sizes, metal-transport distances, and volume
filling fractions by comparison to galaxy-redshift surveys;
(5) Study Galactic halo gas and cooling infall rates in high-velocity
clouds seen in O VI, Si III, and many other ions.
I will conclude by previewing the capabilities and planned
investigations with COS and possible future UVO telescopes in space.
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| ACCESS -- science and engineering assessment of space coronagraph concepts for the direct imaging and spectroscopy of exoplanetary systems
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| Dr.
John Trauger (JPL / Caltech) |
| ACCESS explores the science potential and engineering readiness of a space mission for the direct coronagraphic imaging and spectroscopy of exoplanetary systems at visible wavelengths. ACCESS is a science and engineering study carried out as one of NASA's Astrophysics Strategic Mission Concept Studies. ACCESS compares four major coronagraph architectures in the context of a conceptual space observatory platform of high technology maturity, thereby to provide reliable estimates of science performance, cost, and risk. The study also compares recent laboratory demonstrations with JPL's High Contrast Imaging Testbed (HCIT) as a measure of technology readiness. We describe the unique science enabled by a NASA medium-class coronagraph mission that could be built in the coming decade with proven technologies.
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