Lee Clement PHYS February, 2011

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)

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)

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)

VLA – Design  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) VLA

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)

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)

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)

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 (Finley, 2009)

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)

VLA – Expansion  Upgraded / replaced by the Expanded Very Large Array (EVLA) (NRAO, 2009) x improvement in sensitivity over VLA Resolution improved to ” More streamlined scheduling process Main transition period was

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)

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)

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 & VLA Observable Wavelengths (Source: Wikimedia Commons) SKA

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)

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)

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)

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)

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)

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)

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)

Literature Cited  Chandler C Obtaining observing time on the VLA.  Chandler C Resolution.  Chandra P, Frail DA, Fox D, Kulkarni S, Berger E, et al Discovery of radio afterglow from the most distant cosmic explosion. ApJL. 712 : L31-5  Cole J The expanded very large array project: A radio telescope to resolve cosmic evolution.  Finley D Blast from the past gives clues about early universe.  Finley D New VLA images unlocking galactic mysteries.  NRAO An overview of the very large array.  SKA Home page.