ASKAP Science Update

CSIRO Astronomy and Space Science May 2010

The ASKAP Science Update is a regular series dedicated to conveying the latest news about the Australian SKA Pathfinder (ASKAP) project to the international science community. It is also available online at www.atnf.csiro.au/projects/askap.

ASKAP Simulations Underway An automated source finder that almost 100 MHz were used. Two maximises completeness while minimising cubes were made centred at -45 and Creation of realistic simulated skies, the number of false detections is key. -3 declination to explore the effects of imaging of the simulations using For this reason, two sets of simulations the changing point spread function. ASKAP’s configuration and software have been provided to the project tools, and finding sources in the output The output images and cubes have teams: one of the continuum sky and images and cubes are important been made available to the members one of the extragalactic HI sky. aspects of planning for the science of the Survey Science Projects for that will be conducted with ASKAP. The source catalogue for the simulations testing their source-finding algorithms. came from the SKADS S3-SEX The next simulations will be ready in To achieve these goals CSIRO’s (continuum) and SKADS S3-SAX (HI) coming weeks. These will incorporate ASKAP team has been working closely work carried out at Oxford University full polarisation information and will with members of the ten Survey in the UK, while the simulations were contain transient sources so that the Science Projects that will use ASKAP made possible by the loan of a pre- Polarization Sky Survey of the Universe’s in its first five years of operation. production computer by Intel . Magnetism (POSSUM) and ASKAP “Source finding is critical for several The telescope simulation used the 2 km Survey for Variable and Fast Transients Survey Science Projects, particularly core of the ASKAP configuration (which (VAST) project teams can start to those projects that plan to observe a includes 30 of ASKAP’s 36 antennas) hone their source-finding algorithms. substantial fraction of the visible sky,” says along with 32 idealised beams spaced CSIRO’s ASKAP team will then look to ASKAP Project Scientist Simon Johnston. in a rectangular grid. include galactic continuum and spectral line information into the simulations. “The Widefield ASKAP L-Band Legacy For the continuum simulation the All-Sky Blind Survey (WALLABY) project, total bandwidth was 300 MHz “Plenty of work still lies ahead for the for example, aims to find up to 500,000 divided into 120 channels and, after ASKAP team and the project teams over in HI, and the Evolutionary Map an eight-hour integration, the image the coming year, but these initial of the Universe (EMU) project expects noise was 11 uJy/beam. For the HI simulations and images are a great start,” to see more than 10 million sources.” simulation, 1024 channels covering says Simon.

> Two images showing a simulation of an ASKAP observation of the broadband emission from the sky, with the centre at 1.37 GHz (the right image is a ‘zoomed in’ version of part of the left image). This simulation includes a number of effects including thermal noise from the receivers and wide field-of-view imaging corrections. Credit: Tim Cornwell, CSIRO. “WALLABY will provide the largest, most homogeneous HI sample of galaxies, complemented by similarly uniform multi-wavelength data, yet made.”

ASKAP Survey Science Projects ASKAP Science Update February 2010), And the sensitive HI observations to WALLABY is one of the largest surveys be made by WALLABY will benefit In this edition of ASKAP Science Update that will be undertaken by ASKAP in from the exceptional interference- we take a detailed look at two of the its first five years of operation with a free environment at the Murchison projects that will make use of ASKAP request for one year of observing time. Radio-astronomy Observatory. during its first five years of operation. The project aims to examine the HI “The quality of data obtained with WALLABY Success a Team Effort properties and large-scale distribution ASKAP should be fantastic,“ says Bärbel. of up to 500,000 galaxies to a “I’m excited by the opportunity to make The results generated will also redshift of 0.26, in order to study: discoveries with ASKAP,” says CSIRO’s provide an important insight into what Bärbel Koribalski, one of the Widefield • formation and the missing could be achieved with the Square ASKAP L-Band Legacy All-Sky Blind satellite problem in the Local Group; Kilometre Array, which will conduct Survey (WALLABY) Principal Investigators. more sensitive HI surveys for galaxies • Evolution and star formation in galaxies; “These might be new galaxies, large at higher redshifts than WALLABY. • Mergers and interactions in galaxies; gas disks around known galaxies, or gas The two Principal Investigators clouds such as tidal tails and plumes.” • Physical processes governing certainly won’t be working alone to the distribution and evolution Bärbel, co-Principal Investigator Lister meet WALLABY’s science goals – the Staveley-Smith (International Centre for of cool gas at low redshift; WALLABY team consists of nearly 100 people from around the world. Radio Astronomy Research) and a team • Cosmological parameters of international collaborators will build relating to gas-rich galaxies; “While many team members are on the 60-year legacy of other research based in Australia, there are key • The nature of the cosmic web. that has used the 21-cm line of neutral groups at many institutions spread hydrogen, or HI line, to investigate the By comparison, only about 22,000 galaxies over different continents,” says Lister. evolution and dynamics of galaxies. with HI emission are currently known. “Our collaboration with team WALLABY will conduct an extragalactic “WALLABY will provide the largest, most members in The Netherlands is neutral hydrogen survey over 75% of the homogeneous HI sample of galaxies, particularly important with respect to entire sky. Along with the Evolutionary complemented by similarly uniform multi- achieving a true all-sky survey, which Map of the Universe (EMU) project (see wavelength data, yet made,” says Bärbel. can best be delivered by ASKAP and the new fully funded APERTIF upgrade to the Westerbork Synthesis Radio Telescope.” “Similarly, we are collaborating closely with team members in South Africa who are keen to carry out deep HI observations of galaxies with MeerKAT.” “All the team members are contributing to the breadth of science that we will be doing from hydro-dynamical simulations, exploring optimal source- finding algorithms, the study of cross- correlation functions and large-scale structure as well as complementary multi-wavelength observations of each detected galaxy,” continues Lister. > The international WALLABY team, led by Lister Staveley-Smith and Bärbel Koribalski, will use ASKAP to conduct an extragalactic neutral hydrogen survey over 75% of the entire sky. Credit: Gabby Russell, CSIRO. Science Goals Align for POSSUM How are large-scale cosmic magnetic fields generated and maintained? That’s the central question that the team behind the Polarization Sky Survey of the Universe’s Magnetism (POSSUM) project is looking to answer. The polarisation angle of light emitted by > A NRAO Very Large Array cosmic objects can be altered as the light research interest in POSSUM is the Sky Survey image of the sky in passes through a region of magnetised use of rotation measures as probes of polarisation. Credit: Russ Taylor. gas, an effect known as ‘Faraday rotation’. the Galactic and intergalactic fields, and to study the intrinsic rotation measure Led by Bryan Gaensler (University of properties of active galactic nuclei. “We will also make the first significant , Australia), Russ Taylor (University steps before the SKA to explore the “It will revolutionise our understanding of Calgary, Canada) and Tom Landecker magnetic properties of galaxies, the role of magnetic fields in the , (Dominion Radio Astrophysical of magnetism in star formation, and the other galaxies and clusters, and Observatory, Canada), POSSUM will use evolution of fields with cosmic time.” ASKAP to explore cosmic magnetism in the intergalactic medium.” POSSUM will allow Tom Landecker by measuring the polarisation of radio Russ Taylor is also interested in to study the polarised emission that signals reaching the telescope. learning more about the intrinsic is generated by the Milky Way itself properties of active galactic nuclei and From Earth the dominant ‘foreground’ in order to shed light on the role of galaxies as probes of the evolution of magnetised object is the Milky Way, magnetic fields in processes that take magnetic fields with cosmic history. which fills the entire sky. POSSUM will place in the interstellar medium. probe the magnetic field of the Milky “ASKAP will provide a huge step beyond “Stars in the Milky Way form from Way with over a million lines of sight to the capability of existing telescopes for interstellar gas enriched by the traces polarised background sources. Beyond this work through its wide field-of-view of older generations of stars. New stars the Milky Way, ASKAP will allow the and its great sensitivity,” says Russ. impact their surroundings through stellar POSSUM team to explore the magnetic “We will be able to detect polarised winds and explosions. We properties of the extragalactic Universe. radio emission to most radio-loud know that magnetic fields play important “POSSUM will yield a densely packed active galactic nuclei and radio roles in this Milky Way ‘ecosystem’ at all grid of millions of Faraday rotation galaxies in the Universe, as well as stages of these processes, but we know measures over a substantial fraction of from large numbers of galaxy disks very little about the details. POSSUM the sky,” says Bryan Gaensler, whose main out to intermediate redshifts.” will advance us in this quest,” says Tom.

> The POSSUM team is made up of Bryan Gaensler, Russ Taylor and Tom Landecker (above left to right), and 52 co-investigators spread across 14 countries. Several postdoctoral fellows and a new PhD student have also recently joined the team. Credits: Mark Sims/Anglo-Australian Observatory, University of Calgary and Dominion Radio Astrophysical Observatory. Awards Boost SKA Effort for WALLABY and the other Forthcoming Meetings for EMU-related research. CSIRO has been awarded three of Members of the ASKAP team the Australian Research Council’s new “These Fellowships will help ensure will be attending a number of Super Science Fellowships, worth a total Australia’s readiness for the SKA, boosting upcoming scientific meetings: of A$835,000 over three years. The essential research and development • Cosmic Magnetism: From Stellar to Fellowships are designed to give early- at the interface between engineering Intergalactic Scales career researchers the opportunity to and astronomy within CSIRO and in Kiama, Australia work in areas of national significance. University groups in Australia and around 7–11 June 2010 One of the Fellows will work to the world,” says Lewis Ball, Acting Chief refine a device CSIRO has pioneered of CSIRO Astronomy and Space Science. • A New Golden Age for Radio Astronomy for ASKAP – an innovative phased In total, 21 of the 100 awards (valued Assen, The Netherlands array feed that sits at the focal centre at almost A$5 million over the next 10–14 June 2010 of each of ASKAP’s 36 dishes. five years) are for developing SKA The other two Fellowships are pathfinder instruments and SKA- • International SKA Forum 2010 for science with ASKAP: one is related research in Australia. Assen, The Netherlands 15 June 2010 • Astronomical Society of Australia Annual Science Meeting 2010 Hobart, Australia 5–8 July 2010 If you would like to find out more or have questions about ASKAP please don’t hesitate to find us, we look forward to meeting you.

For further information: Gabby Russell Communication Officer CSIRO Astronomy and Space Science Phone: +61 2 9372 4339 > A prototype of ASKAP’s innovative phased array feed receiver, which will be Email: [email protected] refined by CSIRO for possible use in the SKA. Credit: David McClenaghan, CSIRO. Web: www.atnf.csiro.au/projects/askap