Lee Clement

PHYS 2070

1 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

Wavelengths400 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)

VLAVLA

VLA – Location

Located on the Plains of San Agustin in New Mexico, USAWest of Socorro

Why?Minimal EM interference

○ In the middle of nowhereDry

○ 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 expertsCompetitive

Scheduled every 4 months(Chandler, 2009)

VLA – Targets

MultipurposeNo specific missionOccasionally 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 EarthDetected in 2009 by NASA’s Swift satelliteUniverse was only 630 million years old!Information about the formation of the

(relatively) early Universe and the first starsChandra et al., “Discovery of Radio

Afterglow from the Most Distant Cosmic Explosion”, Oct. 2009

(Finley, 2009)

VLA – Research The HI Nearby Galaxy

Survey (THINGS)(NRAO, 2008)Combines data from

VLA, Spitzer, & GALEXHydrogen-1 emits radio

at a particular frequency○ VLA measured Doppler

shift to measure rotation of nearby galaxiesNever done before in radioProvides information about

dark matter(Finley, 2008)

THINGS: NGC 2403(Source: NRAO)

VLA – Expansion

Upgraded / replaced by the Expanded Very Large Array (EVLA)(NRAO, 2009)

5 - 20x improvement in sensitivity over VLAResolution improved to 0.004 - 0.2”More streamlined scheduling processMain transition period was 2009 - 2010

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 ViewMore 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

ResolutionDepends 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

interferenceCan develop across two countriesHigh bandwidth fibre-optic

infrastructureView 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 discsAlso 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

holesOnly possible in radio with

the required precisionAlso 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 patternsGrowthStructure

Cosmic Magnetism(Source: SKA)

Galaxy Group HCG 87(Source: NASA)

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