the square kilometre array department of astronomy and atmospheric sciences, kyungpook national...

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The Square Kilometre Array

Department of Astronomy and Atmospheric Sciences, Kyungpook National University

김경묵 , 박진태 , 방태양 , 신지혜 , 조창현 , 정수진 , 현화수

Survey Science Group 3rd Workshop

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Outline

< Section 1 >


Introduction What is the SKA? The SKA Timeline

Phase Development

The SKA Telescopes Aperture Array

The Properties of the SKA Sky coverage & Resolution Sensitivity & Depth Data access

The Science Extreme tests of general relativity How do Galaxies Evolve? What is Dark Energy? Around the re-ionization epoch! Understanding Cosmic Magnetism Cradle of Life : Searching for life and

planets

< Section 2 >

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Introduction : What is the SKA? The Square Kilometre Array

The largest, most sensitive radio telescope with an aim to provide fundamental an-swers to questions about the origin and evolution of the universe.

Telescopes will be co-located in Africa and in Australia. South Africa(Karoo desert) : the high and mid frequencies. Australia(Murchison region) : the low frequency and survey instrument.


South Africa

Australia(Image from the SKA official webpage) (Image from the SKA official webpage)

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The SKA Telescopes


High FrequencyMid FrequencyLow Frequency

Telescope Freq.

Freq. Range Collector Number & Size Distribution

Low 70 MHz ~ 450 MHz Aperture array 250 arrays, D = 180 m 66% within 5 km diameter core33% on 5 spiral arms to 180 km

Mid 400 MHz ~ 1.4 GHz Aperture array 250 arrays, D = 56 m 66% within 5 km diameter core33% on 5 spiral arms to 180 km

High 1.2 GHz ~ 10 GHz Dishes 2,500 dishes, D = 15 m50% 5 km diameter core25% - core to 180 km,

25% - 180km ~ 3,000km

Information from “https://connect.innovateuk.org/web/ska/overview”

(Image from the SKA official webpage)

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Aperture Array (AA)


AA is key feature of the SKA. AA is a large number of small, fixed antenna elements

coupled to appropriate receiver systems.

Mid Frequency AA

Low Frequency AA

Advantages of AA Unblocked aperture with full view of the entire sky! Ultimate flexibility and reliability - no moving parts! Beams are formed and controlled electronically! Multiple beams (or FOV) permits concurrent, independent (or associated) observations

→ huge FOV!

(http://ska-ptafrica.org)


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The SKA Timeline



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Phased Development


SKA Phase 1 (2018~)South Africa Australia


HIGH

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Phased Development


SKA Phase 2 (mid 2020s)

South Africa Australia


HIGH

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The Telescope Scale comparison



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The Properties of Instruments


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Sky coverage The SKA Phase 1 shall be able to provide access to at least 2π sr of the sky.

Resolution Angular resolution is about to < 0.1 arcsecond at 1.4 GHz

~3000 km base line

Sky coverage & Resolution


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Sensitivity & Depth


The typical survey’s depth is z 0.2 with massive galaxies detected out to z 0.7.∼ ∼ SKA will have sufficient sensitivity to detect all QSOs and starforming galaxies to

z~20. ~ 50 times more sensitive than the currently most powerful interferometer.

The structure of the universe would be sampled over scales of 10’s of Mpc to several Gpc.

(Taylor, A.R. et al. 1999)(https://connect.innovateuk.org/web/ska/overview)

DepthSensitivity

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Data access


Optical fibres will be essential to trans-port the huge amount of data to the cen-tral SKA processor.

(Image from The Aperture Arrays for the SKA: the SKADS White Paper 4.2010.)

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Data access


Optical fibres will be essential to trans-port the huge amount of data to the cen-tral SKA processor.

(Image from The Aperture Arrays for the SKA: the SKADS White Paper 4.2010.)

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The Science


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The Key Projects


Extreme tests of general relativity How do Galaxies Evolve? What is Dark Energy? Around the re-ionization epoch! Understanding Cosmic Magnetism Cradle of Life : Searching for life and planets


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Extreme tests of general relativity


Was Einstein right or will general relativity eventually fail? What are the properties of black holes? Are there still ripples in space-time from the early Universe?

The SKA will test general relativity extremely with pulsars and black holes.

Pulsars orbiting black holes will test Ein-stein’s description of these enigmatic ob-jects to the extreme.

The best test so far of Einstein’s theory in strong gravita-tional fields is pro-vided by the only known double pulsar system, where two pulsars orbit each other in 145 min.

Pulsars discovered and monitored with the SKA will act like a cosmic gravitational wave de-tector, allowing the study of ripples in the fabric of space-time that propagate at ultra-low frequencies. (Image from the SKA Brochure)

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How do Galaxies Evolve?


Radio telescopes’ ability to “see” regions beyond the optical view of a galaxy, have brought significant insights into how galaxies form and develop.

The SKA’s sensitivity and resolution will be able to track young, newly forming galaxies at cosmological distances, and, through mapping the distribution of H.


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What is Dark Energy?


Mysterious force appears to counteract and even surpass the mutual gravitational attraction causing acceleration in the expansion.

cosmology and dark energy is to observe the gravitational effects of galaxies and clusters of galaxies on the path of radio waves through the Universe.


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Around the re-ionization epoch!


Take snapshots of the 21 cm emission at many different epochs, before, during and after reionisation, yielding detailed information about the formation of the first structures in the universe.

But! these objects are exceptionally faint and much of their light is absorbed by inter-vening matter as it travels toward us.

SKA can resolve this problem thanks to it’s very high sensitivity!

Through multifrequency observations, we can therefore construct fully three-dimen-sional maps of neutral gas in the universe.

Such maps are crucial for studying the time dependence of reionisation.

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Around the re-ionization epoch!


(Furlanetto et al. 2003)

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Understanding Cosmic Magnetism


What is the shape and strength of the magnetic field in our Milky Way?

How does this compare to the magnetism in other gal-axies?

What role has this had on the formation of individual stars and galaxies?

Where and how do the magnetic fields originate?

(Image from Philipp P. Kronberg, Physics Today, 12. 2002, p.30)



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Cradle of Life : Searching for life and planets


The SKA will detect the thermal emission from dust in the habitable zone. In particular, the SKA will show where dust evolves from micron-sized insterstellar particles to cen-timetre-sized and larger “pebbles”.

Astrobiologists will use the SKA to search for amino acids, the building blocks of life, by identifying their spectral signatures at specific frequencies.

The SKA will be able to detect extremely weak extraterrestrial radio signals if they were to exist.


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Reference


Papers Furlanetto, S. R., & Loeb, A. 2003, AJ, 588, 18 Nadin, Maureen et al. 2011, JRASC, 105, 15 Kronberg, P. P., Physics Today, 12. 2002, p.30 Taylor, A.R. 1999, in M.P. van Haarlam (ed.), Perspectives on Radio Astronomy : Science with

Large Antenna Arrays, ASTRON, p. 1 The Aperture Arrays for the SKA: the SKADS White Paper (2010.4)

Webpages The SKA official Webpage (https://www.skatelescope.org)

The SKA Technology subgroup (https://connect.innovateuk.org/web/ska/)

Workshop webpage The Square Kilometre Array: a large Scale ESFRI Infrastructure, From the Cosmos to the Cities of the future (http://

ska-ptafrica.org/index.html)

https://www.skatelescope.org/



https://connect.innovateuk.org/web/ska/

http://ska-ptafrica.org/index.html

http://ska-ptafrica.org/index.html

25Survey Science Group 3rd Workshop

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