SKA Pathfinders: A Bright Radio Future
by Barb Sanford | Development Specialist, UW-Madison Department of Astronomy
Posted Oct 21, 2013
The SKA will span over an area of approximately one square kilometer in Africa, Australia and New Zealand (artist's impression). Image courtesy of SKA / Swinburne Astronomy Productions.
“It’s a great time to be a radio astronomer. The Square Kilometer Array (SKA) and its precursors are opening up a whole new way to do radio astronomy. It’s an exciting new era,” says Professor Eric Wilcots. The UW Astronomy Department is an integral partner to a number of collaborations preparing the science programs for these pathfinder missions.
SKA. At the center of a new generation of astronomical facilities will be a revolutionary new radio telescope, the SKA. Radio telescopes can study the Universe in ways not possible at other wavelengths, because both the emission processes of radio light and the techniques used to observe it are fundamentally different from all other parts of the spectrum. The SKA will answer questions about the link of gravity to other fundamental forces, the origin of dark energy, and the role played by magnetic fields in the formation and evolution of stars, galaxies, and galaxy clusters. It will allow astronomers to search for planets, watch stars form, trace the evolution of galaxies, and piece together the structure of the Milky Way Galaxy.
With a collecting area of around a square kilometer, the SKA will be the world’s premier imaging and surveying telescope. It will observe vast fields of view with enormous sensitivity and cover almost the whole accessible radio spectrum at the same time. Fifty times more sensitive than any other radio telescope, it will survey the sky at least 10,000 times faster than the best current-day telescopes—truly a quantum leap in performance. Part of the SKA is being built in Australia and part in South Africa. The construction of the first elements of the SKA is expected to start in 2016, with the array to be completed by 2024. The first science is expected to commence in 2019.
On the way towards the SKA, South Africa and Australia are building two new pathfinder telescopes—almost like scale models of the full array—to enable early science and iron out the kinks.
MeerKAT. South Africa is currently building the radio telescope MeerKAT (“meer” being the Afrikaans word for “more,” and KAT standing for the Karoo Array Telescope, sharing the name with an adorable small species of mammals native to South Africa). It will be the largest array in the southern hemisphere until the SKA is completed within the next decade. It will consist of 64 dishes of 13.5 meters in diameter each.
ASKAP. The Australian SKA Pathfinder (ASKAP) is a next-generation radio interferometer being built by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Western Australia. It will consist of 36 radio dishes with 12 meter diameter each. Because the telescope has a very large field of view (in other words, it can observe a large area of the sky at once) and covers a very wide part of the radio spectrum, ASKAP will be an excellent survey telescope, well positioned to make substantial advances in the area of galaxy formation and gas evolution in the Universe, and well suited to study the transient radio sky.
JVLA. While the US National Radio Astronomical Observatory (representing the National Science Foundation) is not an active participant in the SKA consortium, technological advances have made breakthroughs in radio astronomy possible right here at home, too: The 2011 upgrade to the Jansky Very Large Array in New Mexico (named after famous UW alum Karl Jansky) has brought this 40-year-old workhorse of radio astronomy into the 21st century, making it up to 8,000 times more efficient, in large part by going from analog to digital technology. In radio astronomy, it really is possible to teach an old dog new tricks.
LADUMA. Professors Eric Wilcots and Matt Bershady are members of the LADUMA (Looking at the Distant Universe with the MeerKAT Array) project, an ultra-deep survey looking for neutral hydrogen in the early Universe. With 5,000 hours of observations with MeerKAT, they will study the evolution of hydrogen gas in galaxies over the last 9 billion years. The survey is based on fields where galaxies have already been identified by other means. Wilcots and Bershady are particularly interested in the internal motions of galaxies, in small galaxies without much gas, and in clouds of neutral hydrogen that are seemingly not associated with an individual galaxy. To complement LADUMA, Wilcots and Bershady are using SALT (Southern African Large Telescope) for optical spectra to help in stacking the radio data from hundreds of galaxies to determine the average gas content of faint objects that would otherwise be unobservable. The LADUMA team consists of 67 astronomers from nine countries on five different continents. Preliminary observations will begin with the completion of the first seven MeerKAT dishes and fully ramp up when the array is completed.
GASKAP. Professor Snezana Stanimirovic and Scientist Bart Wakker are part of the GASKAP (Galactic ASKAP) survey to study the so-called 21-cm neutral hydrogen “spin flip” emission line and the 18-cm lines of hydroxyl in the Galactic plane and Magellanic Clouds. The project will be done with the ASKAP and is one of the ten survey science projects selected as top priorities for the first five years of ASKAP operations. Several additional department members (Professors Jay Gallagher, Alex Lazarian and Ellen Zweibel, and Scientist Matt Haffner) plan to join GASKAP science exploration once the data start flowing.
21-SPONGE. Stanimorovic, with graduate student Claire Murray, postdoctoral fellow Robert Lindner and several undergraduate students (Nick Pingel and Al Lawrence) is undertaking a large pathfinder project with the JVLA called 21-SPONGE (21-cm SPectral line Observations of Neutral Gas with the Enhanced JVLA). It is the most sensitive HI absorption line survey, measuring the temperature distribution of the neutral interstellar gas. In the future, 21-SPONGE will be complemented by GASKAP. While GASKAP will focus on the Galactic plane, mapping about 1,650 square degrees and covering about 5,000 radio continuum sources, the 21-SPONGE survey is focusing on high-latitude Galactic regions with much higher sensitivity.
CHILES. Professors Eric Wilcots and Matt Bershady; former Badgers D. J. Pisano (West Virginia University), Laura Chomiuk (Michigan State University), and Kelley Hess (University of Cape Town); and new grad student Charee Peters are involved in CHILES (COSMOS HI Large Extragalactic Survey). Measurements of neutral hydrogen are essential to our understanding of the universe. Unfortunately, our observational information on HI is mostly limited to the nearby universe. CHILES will use the JVLA to image neutral hydrogen in at least 300 galaxies with a wide range of stellar mass. The deep field will be able to probe the gas reservoirs around small galaxies. CHILES will provide hydrogen gas masses, morphology and kinematics for galaxies spanning a wide range of masses and environments.
Our department has a long-standing research emphasis on gas phase physical processes, ranging from stars to galaxy clusters. The SKA pathfinders will allow observational studies directly aligned with this expertise that will offer us a unique opportunity for discovery. “A coordinated observational-theoretical-numerical approach will enable us to take full advantage of upcoming observing facilities in the next decade and make a big stride forward in understanding galaxy and star formation and evolution,” says Wilcots.