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VLA & SKA

Lee Clement PHYS 2070 1 February, 2011. VLA & SKA. The Very Large Array (VLA). VLA – General Information. Radio observatory Located in New Mexico Operated by the National Radio Astronomy Observatory (NRAO) Part of the National Science Foundation (NSF) Construction began in 1973

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VLA & SKA

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  1. Lee Clement PHYS 2070 1 February, 2011 VLA & SKA

  2. The Very Large Array(VLA)

  3. VLA – General Information • Radio observatory • Located in New Mexico • Operated by the National Radio Astronomy Observatory (NRAO) • Part of the National Science Foundation (NSF) • Construction began in 1973 • Completed in 1980 • Cost USD $78,578,000 (NRAO, 2008) • Fictionalized version used in 1997 film Contact • Also appears in various other films Contact, 1997 (Source: Wikimedia Commons)

  4. VLA – Design • Radio interferometer • 27 antennae on tracks in a Y-shaped configuration • Each antenna is 25 m in diameter • Data is combined electronically • Effective resolution of a single 36 km diameter dish • Effective sensitivity of a 130 m diameter dish(NRAO, 2008) Layout of the VLA (Source: NRAO) VLA Antenna (Source: Wikimedia Commons)

  5. VLA – Design • Aperture size • Four array configurations • Biggest: 36 km across • Smallest: 1 km across • Rotates between them every 4 months • Wavelengths • 400 cm – 7 mm • Short wave radio to Microwaves (NRAO, 2008) VLA VLA Observable Wavelengths (Adapted from Wikimedia Commons)

  6. VLA – Design VLA • Field of View (Chandler, 2009) • Depends on antenna configuration and wavelength • 1.3” at tightest configuration and shortest wavelength • 5.6° at loosest configuration and longest wavelength • Resolution (Chandler, 2009) • Also depends on antenna configuration and wavelength • 0.05” at tightest configuration and shortest wavelength • 14.2’ at loosest configuration and longest wavelength M1 (VLA) (Source: NRAO) M1 (GAO) (Source: PHYS 2070 Lecture Slides)

  7. VLA – Location • Located on the Plains of San Agustin in New Mexico, USA • West of Socorro • Why? • Minimal EM interference • In the middle of nowhere • Dry • Good seeing Location of the VLA (Source: Google Maps)

  8. VLA – Requesting Time • Available to everyone regardless of nationality or institution • Two options • (1) Web-based proposal submission tool • (2) Proposing to NASA missions • Proposals refereed by external experts • Competitive • Scheduled every 4 months(Chandler, 2009)

  9. VLA – Targets • Multipurpose • No specific mission • Occasionally used for atmospheric / weather studies or satellite tracking (NRAO, 2008) Saturn (Source: NRAO) Star Forming Regions in the Milky Way (Source: NRAO) The Milky Way’s Central Black Hole (Source: NRAO)

  10. VLA – Research • Gamma Ray Burst 13 billion l.y. from Earth • Detected in 2009 by NASA’s Swift satellite • Universe was only 630 million years old! • Information about the formation of the (relatively) early Universe and the first stars • Chandra et al., “Discovery of Radio Afterglow from the Most Distant Cosmic Explosion”, Oct. 2009 (Finley, 2009)

  11. VLA – Research • The HI Nearby Galaxy Survey (THINGS)(NRAO, 2008) • Combines data from VLA, Spitzer, & GALEX • Hydrogen-1 emits radio at a particular frequency • VLA measured Doppler shift to measure rotation of nearby galaxies • Never done before in radio • Provides information about dark matter (Finley, 2008) THINGS: NGC 2403 (Source: NRAO)

  12. VLA – Expansion • Upgraded / replaced by the Expanded Very Large Array (EVLA)(NRAO, 2009) • 5 - 20x improvement in sensitivity over VLA • Resolution improved to 0.004 - 0.2” • More streamlined scheduling process • Main transition period was 2009 - 2010

  13. The Square Kilometre Array (SKA)

  14. SKA – General Information • Radio observatory • Next step in radio astronomy • 2 orders of magnitude improvement in sensitivity over existing meter-centimetre facilities (SKA, 2010) • 50x more sensitive than VLA (SKA, 2010) • Intended to complement other observatories • ALMA, James Webb Space Telescope • Construction to begin in 2016 (SKA, 2010) • Complete by 2024 • Concept has been around since 1991! • Estimated cost: €1.5 billion (SKA, 2010) • Funding from various agencies, mostly American and European SKA Logo (Source: SKA)

  15. SKA – Design • Physical Construction • Will have 1 sq. km (1,000,000 sq. m.) of collecting area • Possible configurations being considered (SKA, 2010) • 50 stations with 90 m antennae • 30 stations with 200 m antennae • Will be highly concentrated in the centre of the array with remote stations in a pinwheel arrangement (SKA, 2010) • Three types of antennae for various wavelengths • Aperture • Synthesized aperture diameter of several 1000 km(SKA, 2010) SKA Station Arrangement (Source: SKA) SKA Receivers (Source: SKA)

  16. SKA – Design • Wavelengths • 3 m to 12 mm (SKA, 2010) • Narrower band than VLA • Field of View • More than one! • Can observe up to 10 objects simultaneously (SKA, 2010) • > 200 sq. deg. at wavelengths > 30 cm (SKA, 2010) • 1000 full moons • ~ 1 sq. deg. at shorter wavelengths (SKA, 2010) • 5 full moons VLA SKA SKA & VLA Observable Wavelengths (Source: Wikimedia Commons)

  17. SKA – Design • Resolution • Depends on FOV • 0.1” for 1 sq. deg. observing area (SKA, 2010) • VLA gets 0.05” with tightest configuration • 0.2” for 200 sq. deg. observing area (SKA, 2010) • VLA gets 14.2’ with loosest configuration SKA Sensitivity Map (Source: SKA)

  18. SKA – Location Candidates • Two location candidates • Australia & New Zealand (SKA, 2010) • Low population density areas • Large areas with minimal EM interference • Can develop across two countries • High bandwidth fibre-optic infrastructure • View of the southern sky overlaps that of ALMA and gives a good view of the centre of the galaxy Potential Station Placement in Australia & New Zealand (Source: SKA)

  19. SKA – Location Candidates • South Africa (SKA, 2010) • Low EM interference and low population density • Can spread out • Dry climate • Good seeing • Low land prices and operating costs • Good existing infrastructure Potential Station Placement in Africa (Source: SKA)

  20. SKA – Research • Five main research projects • Cradle of Life (SKA, 2010) • Examining how Earth-like planets are formed • Observing accretion discs • Also able to pick up radio transmissions of the same strength as a TV signal • Could check for signs of intelligent life! Protoplanetary Disc (Source: SKA) Detecting Organic Molecules (Source: SKA)

  21. SKA – Research • Probing the Dark Ages (SKA, 2010) • Will probe the gaseous component of the early Universe • Observe some of the earliest luminous objects • Look at red-shifted radio emissions from Hydrogen-1 • Similar to THINGS The Epoch of Reionization (Source: SKA)

  22. SKA – Research • Strong Field Tests of Gravity Using Pulsars and Black Holes (SKA, 2010) • Will test general relativity in very strong gravitational fields • Pulsars orbiting black holes • Only possible in radio with the required precision • Also looking for gravitational waves • Different wavelengths than LIGO and LISA Pulsar Orbiting a Black Hole (Source: SKA)

  23. SKA – Research • Origins and Evolution of Cosmic Magnetism (SKA, 2010) • Galaxy Evolution, Cosmology, and Dark Energy (SKA, 2010) • Clustering patterns • Growth • Structure Cosmic Magnetism (Source: SKA) Galaxy Group HCG 87 (Source: NASA)

  24. Literature Cited • Chandler C. 2009. Obtaining observing time on the VLA. http://www.vla.nrao.edu/astro/guides/vlas/current/node45.html • Chandler C. 2009. Resolution.http://www.vla.nrao.edu/astro/guides/vlas/current/node10.html • Chandra P, Frail DA, Fox D, Kulkarni S, Berger E, et al. 2010. Discovery of radio afterglow from the most distant cosmic explosion. ApJL. 712 : L31-5 • Cole J. 2009. The expanded very large array project: A radio telescope to resolve cosmic evolution. http://www.aoc.nrao.edu/evla/ • Finley D. 2009. Blast from the past gives clues about early universe. http://www.nrao.edu/pr/2009/grbz8/ • Finley D. 2008. New VLA images unlocking galactic mysteries. http://www.nrao.edu/pr/2008/things/ • NRAO. 2008. An overview of the very large array. http://www.vla.nrao.edu/genpub/overview/ • SKA. 2010. Home page. http://www.skatelescope.org/pages/page_student.htm

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