Very Wide Field Surveys

Conference Report

Massimo Robberto,, & Andy Ptak,

bannerThe conference “Very Wide Field Surveys in the Light of Astro2010” was cohosted by the Institute and the Johns Hopkins University on June 13–16, 2011. Over 120 participants came to discuss the future of astronomical surveys. The scientific prospects of large surveys are enormous, as reflected in the top facilities recommended by Astro2010—the space-based Wide-Field Infrared Survey Telescope (WFIRST) and the ground-based Large Synoptic Survey Telescope (LSST). Are we ready? How must we prepare? The goal of this conference was to promote awareness of the issues and opportunities of the coming era of very wide-area surveys.

LSST and WFIRST will look deeper and wider than any previous surveys in the optical and near-infrared, respectively. They will open vast regions of observational parameter space. It is a safe bet that no endeavor in astronomy will be untouched by the technology and science of these surveys. They will explore, discover, and gather detailed statistics, on vast scales.

As capable as the new surveys will be, their ultimate scientific success will rely in part on other capabilities. New facilities will be needed to follow up discoveries and to provide crucial information—from spectroscopy, multi-band imaging, and temporal data—to clarify the nature of objects and phenomena. In most cases, these supporting capabilities are not yet available, at least at the scales needed for these surveys; some are only in the conceptual planning phase. The conference provided an opportunity for interested parties—project staff, prospective users, and government decision-makers—to think about possible approaches and solutions.

Spectroscopic follow up will be essential for many investigations, beginning with dark energy. Spectroscopic instruments with more fibers and larger fields will be needed to keep up. Currently, the state of the art is being advanced on several fronts, by the Big Baryon Oscillation Sky Survey (BigBOSS), the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), the Hobby-Eberly Telescope Deep Energy Experiment (HETDEX) and the ESO concept for the 4-meter Multi-Object Spectroscopic Telescope (4MOST). BigBOSS, for example, plans 5,000 fibers on a focal plane of seven square degrees, using the four-meter Mayall telescope at KPNO. Another example is the Galaxy and Mass Assembly (GAMA) survey, which brings together the unique spectroscopic capabilities of the Anglo-Australian Telescope and multi-wavelength data from other facilities, such as the X-ray Multi-Mirror Mission–Newton, Galaxy Evolution Explorer, Herschel Space Observatory, and the Square Kilometer Array. However, none of these endeavors approaches the scale of follow-up spectroscopy that WFIRST and LSST will call for.  The option of constructing new facilities or re-developing old facilities to be spectroscopic survey telescopes was also discussed (e.g., the Next Generation Canada-France-Hawaii Telescope).

Multi-band imaging reveals the physics of the sources. The value of wide-field surveys across the full electromagnetic spectrum, from radio wavelengths to X-rays, is illustrated by the recently completed Wide-field Infrared Survey Explorer (WISE) mission, as well as by the prospects of missions soon to be launched, such as Gaia and the Extended Roentgen Survey with an Imaging Telescope Array (eROSITA)—which is an instrument soon to fly on the Russian Spectrum Roentgen Gamma spacecraft. Will these and other facilities be available for multi-wavelength follow-up observations and be sufficiently matched in sensitivity to surveys such as LSST? In the mid-to-far infrared, neither the old data from the Infrared Astronomical Satellite nor new data from AKARI will suffice in a support role for LSST and WFIRST.

In time-domain astronomy—important for supernovae, active galactic nuclei (AGN), and other transient sources in the Galaxy and beyond—the need for new capabilities and institutional arrangements will be particularly acute. Opportunities to follow up transient events are fleeting, which puts a premium on rapid data analysis and adroit telescope scheduling, when the circumstances merit. Classifying transients is an operational challenge. LSST may issue up to one hundred thousand alerts every day—how to decide which ones are interesting? The ultimate scientific success of transient studies will depend on improvements in algorithms and computer codes that sift the flood of data with accuracy and efficiency. It will also depend on the availability of facilities to follow up interesting events, especially by spectroscopy. Work has begun on this challenge for LSST, and useful lessons are available from the Palomar Transit Factory and the Catalina Real-Time Transit Survey.

Astronomy is no longer a data-poor field. Astronomers already have an abundance of data to work with, and the new wide-field surveys will greatly expand this volume. Increasingly, advances in astronomical research challenge the human and technical capacities to curate, extract, and analyze massive quantities of data—and, of course, to think about the results and draw conclusions. When we think how our field and we, ourselves, have evolved in the recent decades, there is no doubt we will adapt and succeed.

All conference talks were webcast and archived. The abstracts of the talks are available here. The symposium page includes a link to a wiki page, which you can use to provide input to the team drafting a white paper based on the conference.