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Origins Understanding the dramatic evolution of galaxies over cosmic time through observations is a key part of the committee’s recommended science program. Following the growth of cosmic structure and learning empirically how the dark and luminous matter are connected is a major science goal for GSMT, which, with its superb spectroscopic reach, would be able to measure redshifts and thus infer distances all the way from our local neighborhood to the epoch of reionization and monitor the build-up of mass and the rise and fall of star formation at visual wavelengths. Meanwhile CCAT would provide the submillimeter perspective on the history of star formation over cosmic time. (See Figure 7.2 for an illustration of the complementarity.) The “fossil record” of how our Milky Way galaxy was assembled can be traced by studying resolved stellar populations with LSST and JWST, and by using the adaptive optics capability on GSMT. GSMT would also be able to perform exquisite spectroscopy of the most ancient, nearby stars. In the next decade, large-scale numerical simulations of the formation and evolution of galaxies should achieve the spatial resolution and physical realism necessary to interpret these observations successfully and to tell the story of how our galaxy was born. Our understanding of star formation under a wide variety of physical conditions will benefit from extensive surveys of the giant molecular clouds within which stars form. ALMA will and CCAT would be major tools for this exploration. Complementary studies of the young stars spawned in these molecular regions will require infrared surveys with high angular resolution both in our galaxy and in the neighboring galaxies the Magellanic Clouds, using JWST in space and GSMT equipped with adaptive optics on the ground. Since solar flares create many cosmic rays that can cause mutations of genetic material, understanding these flares is important for understanding the chances of a planet being habitable. Flares on the more numerous low mass, cool stars may preclude some forms of life on orbiting planets—already known and to be discovered. Studying flares from the Sun using optical techniques with ATST and at radio frequencies—by using the proposed mid-scale innovations program candidate Frequency Agile Solar Radiotelescope (FASR)—as well as stellar flares in far-off planetary systems using the proposed IXO, could advance our understanding of planetary habitability. Understanding the Cosmic Order The critical constituents of galaxies—dark matter, stars, gas, dust, and super-massive black holes—are strongly coupled to one another. The program recommended here will allow major progress in our understanding of this cosmic order. Large multi-object spectroscopic surveys with new instruments would measure the stellar populations and the internal motions of thousands of distant galaxies in a single observation. High-angular-resolution optical and near-infrared integral-field-unit spectrographs on intermediate-class and large-aperture ground-based telescopes would trace in detail the internal velocity fields of galaxies. Meanwhile, while JWST will provide observations on the assembly of galaxies over cosmic time, IXO would obtain X-ray observations of the warm and hot gas in the dark matter halos that surround galaxies. High-mass stars embedded in dense gas within galaxies can be inventoried with CCAT and studied in detail with ALMA. These stars are thought to be the main agents for injecting mass and energy into the interstellar medium and for driving galactic outflows. They do this through powerful stellar winds and supernova explosions, both of which are also responsible for accelerating cosmic rays and amplifying magnetic fields. The proposed ACTA facility will advance understanding of the mechanisms involved. The cycling of gas from galaxies to the surrounding intergalactic medium and back again could also be studied with a GSMT telescope, using high-resolution optical spectra to study gas absorption lines highlighted by background quasars along many sight-lines, but a future UV space mission will be needed for a complete inventory. This program of observations will move the subject of galaxy evolution from one largely dominated by surveys to one of integrated measurements of the buildup of dark matter, gas, PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION 7-14
FIGURE 7.2 Multiwavelength images of high‐redshift source GOODS 850‐5 showing the complementarity of multiwavelength data and the promise of a future GSMT/JWST/CCAT/ALMA combination for studies of early galaxies. (Credit W.‐H. Wang, A.J. Barger, and L.L. Cowie 2009, ApJ 690, 319). stars, metals, and structure over cosmic time. These observations will lay the foundation for the ultimate aim of a complete ab initio theory of galaxy formation and evolution. Understanding of the structure and evolution of stars is the foundation on which the knowledge of galaxies and the rest of the universe is built. ATST will provide tools for the study of solar (and hence stellar) rotation and magnetic fields. The time-domain information obtained from LSST would provide an unprecedented view of magnetic activity in other stars. LSST would also yield a large sample of Type Ia supernovas that could be followed up immediately by a GSMT in order to identify the progenitor stars and better understand the physical processes involved in their explosions. Likewise LSST would detect many Type II supernovas and find new types of rare or faint outcomes of massive-star evolution that have never been seen before. Key properties of compact stellar remnants such as neutron stars will be measured in new radio pulsar surveys that are less biased against detecting the fastest-rotating pulsars. The study of the circumstellar disks out of which planets form will benefit greatly from the high spatial resolution of GSMT, fitted with high-contrast instrumentation so that the faint disks do not get lost in the glare of their parent stars, and there is complementary coverage of wavelengths with JWST and ALMA. Resonant structures and gaps within a disk that may be caused by gravitational perturbations due to planets will be imaged in optical, infrared, and submillimeter radiation, allowing a complete picture of the structure and composition of these disks to be derived. Frontiers of Knowledge The hunt is on to elucidate the nature of dark matter first identified by astronomers more than 70 years ago. If it comprises supersymmetric particles, then there are hopes that they will be seen directly at PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION 7-15
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THE NATIONAL ACADEMIES PRESS 500 Fi
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COMMITTEE FOR A DECADAL SURVEY OF A
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Panel on Stars and Stellar Evolutio
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DOUGLAS FINKBEINER, Harvard Univers
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SPACE STUDIES BOARD CHARLES F. KENN
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activities 2 that have emerged from
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In addition to the 27 panel meeting
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Acknowledgment of Reviewers This re
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The Accelerating Universe 2-26 The
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APPENDIXES A Summary of Science Fro
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light up the universe, marking the
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RECOMMENDED PROGRAM Maintaining a b
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TABLE ES.4 Space: Recommended Activ
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Cosmic Dawn: Searching for the Firs
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this imprint would both probe funda
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important outcome will be to open u
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estimated to be on the order of $20
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observatories. For NASA an annual b
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surveys of large fields, enabling s
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RECOMMENDATION: U.S. investors in a
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departments and the community as a
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dominate spending; (2) private-publ
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us was certainly evident during the
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BOX 2-1 Other Worlds Around Other S
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FIGURE 2‐2 The source 3C 75, show
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FIGURE 2‐3 Numerical simulation o
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FIGURE 2‐4 Left panel: Image of t
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FIGURE 2‐6 Top: Schematic of the
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Most stars with masses smaller than
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BOX 2-2 The Origin of Planets After
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send material raining into the cent
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BOX 2-4 Lifecycles in Galaxies One
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Stars Stars are the most observable
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ubiquitous high-energy charged-part
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The Nature of Inflation As describe
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FIGURE 2‐11 Pie chart showing the
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An important clue to the nature of
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Studying the properties of neutron
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FIGURE 2‐14 A possible pathway is
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partners and makes recommendations
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As astronomy research has blossomed
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are increasingly relevant. The Euro
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TABLE 3-1 Currently Operating OIR F
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29% 1990 44% US Priv US Fed Other E
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CONCLUSION: Complex and high-cost f
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Space Observatories The Laser Inter
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Physics Division (PHY); the Mathema
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4 Astronomy in Society Astronomy of
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FIGURE 4‐2 The dust sculptures of
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FIGURE 4‐5 President Obama takes
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Astronomy Inspires in the Classroom
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teaching the scientific method. The
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where the fraction of astronomers h
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Percentage of AAS Membership by Fie
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0.4 0.3 0.2 0.1 PL SO IM AG SF IN S
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FIGURE 4‐12 Number (top panel) an
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Professional training needs to acco
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assistant and associate professor p
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NRC NSB NSF NSF-AGS NSF-ARC NSF-AST
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