A Radio Sky Surveys Project with the Allen Telescope Array Response to the Request for Information Part 2 Contact Author: Geoffrey C. Bower, UC Berkeley, [email protected] Individual Collaborators: Don Backer, Frank Bigiel, Steve Croft, Carl Heiles, Casey Law, Jack Welch (UC Berkeley Radio Astronomy Laboratory), Peter Backus, Samantha Blair, Jill Tarter (SETI Institute), Crystal Brogan (NRAO), Chris Carilli (NRAO), Ed Churchwell (Wisconsin), James Cordes (Cornell), Richard Crutcher (Illinois), Jeremy Darling (Colorado), Bryan Gaensler (Sydney), Paul Goldsmith (JPL), Patricia Henning (UNM), Richard Conn Henry (JHU), Day- ton Jones (JPL), Athol Kemball (Illinois), Michael Kramer (MPIfR), Steve Kilston (Ball), Glen Langston (NRAO), Joseph Lazio (NRL), Guillermo A. Lemarchand (Instituto Argentino de Ra- dioastronoma), Duncan Lorimer (WVU), Jean-Pierre Macquart (Curtin), Maura McLaughlin (WVU), Steve Myers (NRAO), D.J. Pisano (WVU), Mary Putman (Columbia), Snezana Stanimirovic (Wis- consin), Bart Wakker (Wisconsin), Fabian Walter (MPIA) The North American NanoHertz Observatory of Gravitational Waves (NANOGrav): Anne Archibald (McGill University), Zaven Arzoumanian (Goddard Space Flight Center), Paul Demorest (National Radio Astronomy Observatory), Rob Ferdman (CNRS, France), Paulo Freire (National Astronomy and Ionospheric Center), Marjorie Gonzalez (University of British Columbia), Fredrick Jenet (University of Texas, Brownsville, CGWA), Victoria Kaspi (McGill University), Vlad Kondratiev (West Virginia University), Andrea Lommen (Franklin and Marshall College), Ryan Lynch (University of Virginia), David Nice (Bryn Mawr College), Scott Ransom (National Radio Astronomy Observatory), Ryan Shannon (Cornell University), Ingrid Stairs (University of British Columbia), Dan Stinebring (Oberlin College) Radio Sky Surveys Project 1 1 Executive Summary We describe here the Radio Sky Surveys Project (RSSP): a set of surveys that will be conducted with an expanded Allen Telescope Array (ATA). The RSSP exploits unique ca- pabilities of the ATA, especially the world-leading survey speed of a 256-element array and the ability to conduct multiple science programs commensally. Key science areas are in the dynamic radio sky, SETI, star formation, galactic structure, galaxy evolution, cosmology and fundamental physics through pulsar observations. The planned surveys will be an im- portant complement to the significant capabilities of the existing radio facilities and will provide results complementary to the next generation of instruments across the spectrum. The RSSP surveys will be conducted by US and international science collaborations. The ATA is a radio interferometer, currently with 42-elements, that receives signals over the continuous frequency range of 0.5 to 11.2 GHz. The small diameter dishes of the ATA give it a very wide field of view, making the ATA an excellent instrument for surveys. The ATA employs flexible digital electronics that enable a wide range of science. Expansion of the ATA to 256 elements will dramatically expand the survey speed and sensitivity of the telescope. We calculate full RSSP costs at $44M for construction, $26M for operations, and $12M for analysis of surveys (2009 dollars). The ATA has been a scientific, technical, and finanical pioneer through the development of novel technologies. The ATA has been funded through a hybrid funding model by a public/private partnership that has invested $55M over the past decade. Three-quarters of these funds have been invested in non-recurring engineering costs. The RSSP is in a mature state given the years of development and operations of the ATA; the RSSP can be launched immediately with an accurately-costed model for construction, operations, and science. The RSSP is an important fore-runner to the Square Kilometer Array (SKA). The ATA strongly resembles the baseline design of the SKA. Construction, operation, maintenance, and scientific use of an array with hundreds of elements will be an important contribution to the international effort. The document is arranged as follows: 1. Executive Summary... 1 2. Key Science Goals... 2 3. Technical Implementation... 7 4. Enabling Technology... 17 5. Facility and Science Operations... 20 6. Programmatics and Schedule... 22 7. Cost Estimates... 28 8. Questions from the Panel... 30 9. Budget Summary... 33 10. RFI2 Tables... 36 Radio Sky Surveys Project 2 2 Key Science Goals of the Radio Sky Surveys Project This is a revolutionary period for astronomy. New detector and computing technologies are enabling telescopes and surveys that have not been previously possible. Astronomy is being transformed from a data-starved to a data-rich science. The Sloan Digital Sky Survey represents the current peak achievement of survey science: a focused science collab- oration has produced a systematic view of the optical sky that has impacted all areas of astrophysics. And much is yet to come: the newly commissioned and proposed synoptic telescopes (Palomar Transient Factory, PanStarrs, LSST) offer the potential to expand the envelope of knowledge of the optical sky dramatically. Wide area surveys at meter and centimeter wavelengths – from the venerable 3C catalog, to the atomic Hydrogen surveys (HCRO, Dwingeloo, HiPASS, GPS, GALFA), and the VLA surveys (NVSS,FIRST,VLSS) – have been integral to progress in many fields. The Dynamic Radio Sky: The time domain is ripe for exploration, as observations over the past decade have emphasized that the sky is in fact quite dynamic. Known sources have been seen to behave in new ways and what may be entirely new classes of sources have been discovered. Radio observations triggered by high-energy observations (e.g., observations of gamma-ray burst [GRB] afterglows), monitoring programs of known high-energy transients (e.g., X-ray binaries), giant pulses from the Crab pulsar, a small number of dedicated radio transient surveys, and the serendipitous discovery of transient radio sources (e.g., near the Galactic center, brown dwarfs) all suggest that the radio sky is likely to be quite active on timescales from nanoseconds to years and at wavelengths from meters to millimeters. Imaging and fast transient surveys are underway with the current ATA-42 (Fig. 1). As an example of an RSSP transient survey, we consider the goal of routine detection of orphan gamma-ray burst afterglows. OGRBAs correspond to GRB afterglows in which the gamma-ray emission is beamed away from the Earth and, therefore, undetectable but the optical and radio afterglow is emitted more isotropically. Thus, OGRBAs will resemble ordinary afterglows but will outnumber them by factors of 10 to 1000, providing a sky density of ∼ 0.01 to 1 per square degree per day, assuming a 10 day lifetime. But ordinary afterglows require the significant sensitivity of an instrument like the VLA or EVLA (∼ 0.1 mJy) to detect even a fraction of them; the current ATA-42 will only detect the most extreme of these objects. Thus, a high sensitivity instrument with large field of view (FOV), sensitivity at high frequency, and high cadence over ∼ 104 square degrees is necessary to detect a significant population of these objects within a one-year survey. An ATA-256 survey for OGRBAs would also have considerable sensitivity to radio supernovae as well as the capability to build up static sky models that are an order of magnitude deeper than existing catalogs. Simultaneous searches for high time resolution signals such as pulsar giant pulses can also be conducted. Detection of Gravitational Waves through Pulsar Timing: One of the most fun- damental ingredients for our understanding of gravitation is the existence of gravitational waves (GWs). This theoretical prediction can be tested by the first direct detection of gravitational waves whose existence are indirectly inferred from binary pulsar observations. Direct detection is the goal of a number of special-purpose, ground-based GW detectors, but Radio Sky Surveys Project 3 Time Sample of Crab Pulsar (sample = 4311976, sigma = 15.75) 240 1501 1483 200 1465 1448 160 1430 1412 120 Frequency (MHz) 1395 80 1377 1359 40 1342 6 13 19 25 31 38 44 Time (ms) 2 2 Figure 1: (left) A 30 deg map that is a subset of the full 800 deg map made with 350 ATA-42 pointings in 10 h of observing at 1.4 GHz. Several thousand sources are detected in the full image. Circles indicate known NVSS sources. Repeated observations can identify transient and variable sources. (right) A burst from the Crab pulsar detected by the ATA Fly’s Eye experiment, which simultaneously searched 200 square degrees for millisecond-duration pulses. is also achievable by an astrophysical GW detector constructed from a network of millisec- ond radio pulsars. This is possible as the Universe is expected to be filled with a stochastic background of gravitational radiation that originates from the manifold of coalescing massive binary black holes formed by galaxy mergers. The measurement of such a background would be the first direct detection of a GW signal, as well as a rich source of new astrophysics. This experiment requires the repeated timing of a large sample of millisecond pulsars and the accurate determination of their pulse time-of-arrival (TOA). While this experiment, known as a pulsar timing array is conceptually simple, one needs to combine a large sensitivity with mitigation for the time-varying effects of the interstellar medium. The ATA can observe 3 to 4 bands simultaneously, located across the frequency range that is optimal for pulsar studies and for the separation