Panel Reports—New Worlds, New Horizons in Astronomy and Astrophysics (2011) / Chapter Skim
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9 Report of the Panel on Radio, Millimeter, and Submillimeter Astronomy from the Ground
9 Report of the Panel on Radio, Millimeter, and Submillimeter Astronomy from the Ground
Pages 439-500
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It is possible that gravitational waves will be detected by timing arrays of pulsars, with the Arecibo Observatory playing a crucial role. The University Radio Observatories (UROs)
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Upgrades of modest cost to existing RMS facilities may allow the first discovery of gravitational waves and imaging of the event horizon around a black hole. The steps taken during this decade can lead to the next great advance in future decades, a telescope capable of studying the atomic gas flows that fed galaxies back in cosmic time and capable of studying the inner parts of circumstellar disks, where Earth-like planets may be forming.
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CCAT is a 25-m-diameter telescope located on a very high, dry site and equipped with megapixel detector arrays; it will address many of the questions posed by the Science Frontiers Panels. CCAT is estimated to cost $110 million, with $33 million coming from NSF.
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that are needed to answer the science questions raised by the Science Frontiers Panels (SFPs) and summarizes them (as numbered below)
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The CFP report requires a suite of instruments that characterize the cosmic microwave background (CMB) to determine properties of the early universe.
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. A project focusing on this goal is discussed in the PAG report, and so only the consequences for RMS facilities are summarized here.
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RMS facilities can characterize the shapes and substructures of galactic halos using high-angular-resolution observations of gravitational lensing. The EVLA will find hundreds of lenses, but ultimately approximately 106 lenses will be needed, requiring a capability for very sensitive centimeter-wave imaging.
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universe. Detecting H I in galaxies at redshifts as high as z ~ 1 will require very sensitive centimeter-wave imaging, requiring a
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science frontier covers galaxy build-up and evolution back to z ~ 0.1. RMS facilities are well suited for GAN studies through their ability to probe cold flows, star formation, the environment of SgrA*
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By imaging radio synchrotron emission, H I, and molecular lines, one can assess the impact of feedback on the surrounding medium. Sensitive, low-resolution observations with radio facilities play a crucial role in studying feedback on large scales, but efficient, high-resolution, centimeter wave capabilities are needed to provide maps of energy deposition into the ISM.
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trace the gas, and synchrotron emission from supernovae traces star-formation rates. Very sensitive 2-cm imaging and fast surveys at submillimeter wavelengths and full wavelength coverage from meter to submillimeter will be required to achieve the goals.
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A dedicated solar radio telescope is needed for this synthesis. FIGURE 9.4 Models for magnetic fields on the Sun.
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Nearly 2,000 neutron stars are known today, the majority of which have been discovered and characterized through radio observations. The measurement of relativistic effects through binary pulsar timing yields accurate neutron-star and (likely compact-object)
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With transformative new RMS instruments coming on line early in the next decade, and key missing capabilities under development, we are poised to address fundamental questions about how, where, and under what physi cal conditions stars form across the whole spectrum of the stellar mass function. The capabilities required are a combination of fast-survey capabilities at millime ter/submillimeter wavelengths and fast, sensitive surveys at centimeter wavelengths to conduct wide-field surveys at 5- to 20-arcsecond resolution, coupled with more sensitive, sub-arcsecond resolution follow-up of selected regions.
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How do giant planets accrete from disks, and what are these young planets like? While current RMS facilities offer a glimpse of disk structure on scales >20 AU, imminently available new facilities are poised to resolve dust and gas tracers on scales down to 1 AU with high fidelity.
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Table 9.2 lists the RMS facilities open to U.S. investigators -- either currently operating or under construction -- excluding dedicated experiments, such as CMB or EoR ex periments.
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National RMS Facilities National RMS facilities are funded primarily by NSF-AST (Table 9.2)
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(VLBA) NRAO Green Bank Telescope 0.3-100 100 m 7,850 2000 NSF 9′ (λ/21 cm)
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dipoles New Mexico, Array NRL, LANL, Virginia Tech, NRAO, USAF, University of Iowa NRAO Atacama Large Millimeter/ 0.3-0.035 50 x 12 m 5,700 2013 NSF, Canada, 0.02″ (λ/1 mm) 15″ (λ/870 submillimeter Array ESO, Japan, mm)
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The panel lists the national facilities below in order of decreasing age since commissioning. Arecibo Observatory The 305-m Arecibo Telescope is a facility of the National Astronomy and Iono sphere Center (NAIC)
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Those receiving NSF/AST operations funding are part of the URO program, and the fraction of their observing time funded by NSF is subject to an "open skies" policy. Capital funding for construction of university telescopes is a mix of NSF money and alternative sources such as endowments, gifts, and state funding.
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. The ATA currently devotes part of its observing time to the search for radio transients over wide fields of view (GAN Discovery; SSE Discovery)
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, the chemistry of evolved star envelopes, the supermassive black hole at the galactic center (including VLBI; GAN 4; GCT 3) , the cool interstellar medium in nearby galaxies (GAN 2)
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. Under construction in the Atacama Desert in northern Chile at an altitude of 5,000 meters, ALMA consists of a main array of 50 12-meter antennas, which are reconfigurable to allow a wide range of angular resolutions down to 4 milli arcseconds at submillimeter wavelengths.
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With ALMA, one can use diagnostics such as thermal dust continuum emission, molecular rotational lines, and atomic fine-structure lines to study sources as diverse as planetary atmospheres, cometary nuclei, molecular cloud cores, protostellar jets, circumstellar and protoplanetary disks, the immediate environment of the galactic center supermassive black hole, and star-forming galaxies from the present day to z > 10 (PSF 1, 2; SSE 1, 3; GAN 1, 2; GCT 2, 4)
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, with six 15-m telescopes in the French Alps, for observing in the millimeter atmospheric windows. PdBI has 40 percent more collecting area than CARMA but fewer baselines for imaging, with restricted access to southern sources such as the galactic center.
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The ability to determine celestial positions and proper motions with a high degree of precision is a key decadal science goal. The VLBA is unique in providing a platform for precision astrometry at centimeter wavelengths.
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Current Capabilities Within the RMS Observatory Suite The current suite of RMS facilities provides a broad set of functionalities that can address some of the science questions of the next decade. The panel briefly summarizes these capabilities below.
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• Pulsar timing. Pulsar-timing experiments provide a promising way to measure gravitational waves (CFP Discovery)
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The National Astronomy and Ionosphere Center and the National Radio Astronomy Observatory, which are heavily subscribed by other communities, should seek partners who will contribute personnel or financial support to the operation of Arecibo and the Very Long Baseline Array respectively by 2011 or else these facilities should be closed. In response to the senior review, NSF recommended a ramp-down in NSF funding of Arecibo from $10.5 million in 2007 to $4 million in 2011.
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SOURCE: Fredrick Jenet, University of Texas, Brownsville. TABLE 9.3 Capabilities Provided by Current Facilities Capability Current Facilities Needed Development Cosmic microwave background Existing program Continue successful program program Sensitive meter-wave array Demonstrators only Factor-of-10 more area Solar radio telescope Demonstrators only Full range, fast imager Fast millimeter/submillimeter CSO until 2016 Bigger, faster, southern skies surveys Fast centimeter surveys ATA-42, GBT, Arecibo Expand ATA, multibeam GBT, Arecibo Efficient high-resolution imaging at VLA, soon EVLA, ALMA, CARMA Enhance EVLA, ALMA, CARMA centimeter/millimeter Very sensitive centimeter imaging None About 1-square-kilometer area array Dedicated pulsar timing, transients Nothing dedicated, partial support Expand ATA, enhance and dedicate from Arecibo, GBT time on Arecibo, GBT Ultrahigh resolution VLBA Improve sensitivity, astrometric accuracy, develop millimeter/ submillimeter VLBI Complete wavelength coverage EVLA, ALMA Add missing bands
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FUTURE PROGRAM Introduction The panel presents a future program that is balanced: across scientific fields; across wavelength regions; between capabilities for fast, wide-field surveys -- en abled by large, single-dish telescopes equipped with new generations of large format detector arrays -- and for high-resolution, high-sensitivity studies of objects found in surveys. It is balanced among large national/international facilities, small university facilities, and PI-driven projects.
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aims at detailed characterization of the power spectrum of the fluctuations and other statistical measures of the signal. The HERA-II experiment will require approximately a factor-of-10 increase in the collecting area (to about 0.1 square kilometers)
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Frequency-Agile Solar Radiotelescope (FASR) The study of stellar magnetism is the first question raised by the Panel on Stars and Stellar Evolution.
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. Existing solar radio facilities such as NRAO's Green Bank Solar Radio Burst Spectrometer (BSRBS)
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These observations will be unprecedented and will address the question of how magnetic fields power a star's chromosphere and co rona. Their full-Sun, continuous nature will enable FASR to act as a solar survey instrument.
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survey young embedded submillimeter sources in dense molecular clouds and assess their relationship with the stellar initial mass function; (4) map thermal dust emission from nearby galaxies; (5)
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These risks are correlated with image qual ity, which impacts sensitivity and the confusion limit of data. Detector development is progressing rapidly, however, as discussed below in the subsection "Technology Development." The project expects first-light in 2017, but an independent estimate suggested 2024.
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What remaining needs could be satisfied by continuing successful programs or with upgrades and development on these telescopes? The remaining capabilities that are needed to address the science questions are the following: a vigorous program of ground-based CMB studies; an instrument dedicated to transients and pulsar timing; fast-survey capability at centimeter wavelengths; improved sensitivity and wavelength coverage on high-resolution (0.1″ to 1″ resolution)
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Panel rePorts -- new worlds, new HorIzons 478 FIGURE 9.12 The WMAP full-sky map of temperature fluctuations of the cosmic microwave background. The galactic signal has been subtracted.
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The panel strongly endorses continuation of funding by NASA, DOE, NIST, and NSF's Office of Polar Programs at least at current levels. Allen Telescope Array Expansion (ATA-256)
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NRAO Development An ongoing program of moderate, cost-effective, science-driven enhancements to NRAO telescopes can provide missing capabilities (see Table 9.1) that are essen tial to confront many of the key Science Frontiers Panel questions.
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, radio relics and radio lobes (GCT 3) , and atomic hydrogen and magnetic fields across cosmic time (GCT 1, 2)
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These new instruments will enhance searches for gravitational waves using millisecond pulsars (CFP Discovery) , studies of atomic and molecular gas content and evolu tion and astrochemistry throughout the Milky Way (PSF 1)
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While the upgrades will be determined by agreement of the international consortium, there are some obvious examples. Some receiver bands are not included in the first-light complement; adding these is important for obtaining complete wavelength coverage within atmospheric windows, which is especially needed for line studies of galaxies over the full range of redshifts.
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The panel looked among these for those that satisfied needs that were unmet by the larger projects. The remaining capabilities that are needed to address the SFP science questions are the following: improved sensitivity at millimeter wavelengths for ultrahigh resolution (micro-arcsecond)
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These upgrades will yield fast mosaicing speeds with a unique combination of high angular resolution and good surfacebrightness sensitivity. The fast speeds will enable surveys of statistically large samples of molecular clouds for studies of star formation from the solar neighborhood (PSF 1)
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Aside from the needed new capabilities discussed above, the major gaps in the RMS system are adequate funding for individual investigators and adequate support for the UROs. Archives and User Support for RMS Facilities With the data flow from ALMA, RMS science will enter a new era.
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There are efforts underway to provide an improved aperture-synthesis reduction-and-mapping package, CASA, for both the EVLA and ALMA, as well as for URO synthesis telescopes, and to provide a more user-friendly image archive. Unlike the situation at the NASA great observatories, observing time on RMS facilities is not generally accompanied by funding for analysis and publication.
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A diversity of approaches in the power-detection, RF coupling, and readout technologies has been a strength and should be supported, along with the continued development of total-power coherent detector arrays. Ongoing support is needed to continue the growth in detector elements shown in Figure 9.16.
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9-16.eps bitmap Laboratory Astrophysics A wide range of new RMS facilities that are currently operating (e.g., spectrometers on the Herschel Space Observatory) or coming on line in the next decade will provide unprecedented access to diagnostic astrophysical spectral lines at sensitivities that may be 10 to 100 times better than those of current instruments (Figure 9.17)
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provided some directed funding for laboratory astrophysics in support of a few missions, for example the Herschel Space Observatory, but that funding has been limited and of relatively short duration. In the coming decade, it is critically im portant that the astronomical community find a way to provide sustained support for laboratory astrophysics, potentially through cross-divisional NSF funding ini tiatives or directed funding lines within the astronomy division.
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• Theoretical studies and numerical modeling of MHD processes on a wide range of scales, from the small-scale physics of reconnection and particle acceleration to the effects of magnetic fields on galactic and extragalactic scales.
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• Theoretical studies and numerical modeling of planet formation, evolution, and dynamics in a range of environments. • Modeling of radiative and dynamical processes in planetary atmospheres.
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Looking to the Future The Square Kilometer Array is seen as the next-generation centimeter-wave and meter-wave telescope, which would address many fundamental science questions. This project has already garnered significant international support, with 55 institutions in 19 countries participating.
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The panel identifies a need for technology development in four main areas and an interdisciplinary laboratory astrophysics program, along with theory and algorithm development relevant to RMS science. The panel's recom mendations are made in the context of the following assumptions: a 7 percent per year increase in the NSF-AST budget and the augmentation of a funding line for mid-scale construction projects of at least $20 million per year.
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The first phase, HERA-I, is underway with two parallel efforts engaged in testing techniques. The panel strongly recommends continued funding for both these efforts at a combined rate of approximately $5 million per year to about 2015, at which time a review would be needed.
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The panel assumes no operations funding this decade. Sustaining and Upgrading Current and Imminent Facilities The panel's top priority in the facilities area is continued funding of a vigorous, diverse program of ground-based research on the cosmic microwave background.
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Strategic theory and algorithm development should be supported to maximize the return on investments in facilities. Summary With a combination of new facilities and the sustenance and invigoration of existing programs and facilities, almost all the RMS capabilities needed to answer the science questions posed by the Astro2010 Science Frontiers Panels can be realized (Table 9.4, Figure 9.18)
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Panel rePorts -- new worlds, new HorIzons 498 TABLE 9.4 Needed RMS Capabilities and the Panel's Recommended Actions Capability Recommended Action Cosmic microwave background program Continue successful program Sensitive meter-wave array Continue HERA-I, fund HERA-II mid-decade Solar radio telescope Construct FASR Fast millimeter/submillimeter surveys Participate in construction, operations of CCAT Fast centimeter surveys Enhance ATA, GBT, Arecibo Efficient high-resolution imaging at centimeter/millimeter Enhance EVLA, ALMA, CARMA Very sensitive centimeter imaging Cannot meet this decade, technology development Dedicated pulsar timing, transients Enhance ATA, Arecibo, GBT Ultrahigh resolution Enhance VLBA, millimeter-wave VLBI Complete wavelength coverage Enhance ALMA FIGURE 9.18 Mapping of re quired capabilities to new ini tiatives, upgrades of existing facilities, and continuation of successful programs. Dashed arrow indicates that need can not be met this decade.
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2, tie 2, starting 2015 33a Participate in construction, operations of CCAT 2, tie 5, starting 2017 44b Enhance ATA if possible 4 3, increasing to 6 in 2015 90c Enhance GBT, EVLA, VLBA 5, tie 1 30c Enhance ALMA 5, tie 25c Enhance CARMA, EHT Enhance UROs support 2 Enhance Arecibo support, if possible 2, starting in 2012 Enhance ATI 1 Laboratory astrophysics 2 Total over decade 357 131 aMid-scalefunding. bMid-scaleor other funds for upgrades.
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