Science with SKA:
The SKA will provide continuous frequency coverage from 50 MHz
to 14 GHz in the first two phases of its construction.
A third phase will then extend the frequency range up to 30 GHz.
•Phase 1: Providing ~10% of the total collecting area at low and mid
frequencies
•Phase 2: Completion of the full array at low and mid frequencies
SKA-low array – a phased array of simple dipole antennas to
cover the frequency range from 50 to 350 MHz.
SKA-mid array –to cover the frequency range 350 MHz to 14 GHz.
SKA-survey array - a compact array of parabolic dishes of 12–15
meters diameter each for the medium-frequency range, each
equipped with a multi-beam, phased array feed with a huge field of
view
•
•
•
SKA1-low (Aus)
SKA1-mid (SA)
SKA1-survey (Aus)
SKA1-low
• Australia
• Main driver: highly redshifted 21 cm HI line from the
Epoch of Reionization and earlier
– pulsars, magnetized plasma, extrasolar planets
• ~250000 antennas
• 50-350 MHz
• 1 km radius core
• 45 km maximum baseline
• 20 deg2 field of view
SKA1-mid
• South Africa
• pulsars, nearby to mid-z
HI line, high sensitivity
continuum sources
• ~250 15m dishes
(Meerkat+SKA1 dishes)
• 0.35-3 GHz; ready for
additional receivers
• ~100 km maximum
baseline
SKA1-survey
• Australia
• survey large areas of sky in
line and continuum, transients
• ~100 15m dishes
(ASKAP+SKA1 dishes)
• 0.6-1.7 GHz
• ~25 km maximum baseline
• PAF (Phased Array Feed)
Sensitivity + Survey Speed: 3 days to do survey like NVSS
( ~ 10 months VLA over 3 years)
On 18 August 2014, Philip Diamond, Director General of the SKA
Organisation, visited the 54th Research Institute of China Electronics
Technology Group Corporation (CETC54) in Shijiazhuang, about
300km south west of Beijing to see a complete prototype SKA antenna
The Chinese antenna is an offset Gregorian dual reflector. The main
and sub reflectors were made of Carbon Fiber Reinforced Polymers
(CFRP), based on single piece
panel and surface metallizing
technology. The main
reflector size is 18m × 15m,
the sub reflector size is
5m × 4.7m.
Hubble Deep Field with the SKA
HST
SKA
SKA 8 hour integration (simulation by
Hopkins et al.) :  2200 sources
HDF simulation based on source counts : Starburst are blue, AGN are red.
A beam of 0.1” is needed to minimize confusion.
 Star formation history of the Universe
 Star formation vs nuclear activity
Key Science Projects
Origin of the Universe :
1. Formation of first objects/EoR
2. Evolution of galaxies/ Cosmology/ Dark energy
Fundamental Physics :
3. Pulsars/ General Relativity/ Gravitational Waves
4. Cosmic Magnetism
Origin of life :
5. Cradle of life and intelligent life
Probing the Dark Ages
COSMIC HISTORY OF THE UNIVERSE
The Dark Ages
Era of the Universe
300 000 - 1 000 000 000 yr
after the Big Bang during
which the first stars and
galaxies formed
Hague: 6 Feb
B.J.Boyle
13
Probing the Dark Ages
SKA Role
Detect and image hydrogen in the dark ages, provide 3D
maps of the early cosmic web, shed light on the physics of
the formation of the first objects in the Universe
HI @ z = 5 : ’ = 1.3 m, 240 MHz
z = 10 : ’ = 2.3 m, 130 MHz
z = 20 : ’ = 4.4 m, 68 MHz
10.4
11.2
12.1
13.2
14.5
16.1
18.3
7.2
7.5
7.9
8.3
8.7
9.2
9.8
CO @ z = 5 : ’ = 1.6 cm, 19 GHz
z = 10 : ’ = 2.7 cm, 11 GHz
z = 20 : ’ = 5.5 cm, 5.5 GHz
20 h exposure per pointing, 400 pointings
with 50o field of view (HI, conservative)
Hague: 6 Feb
B.J.Boyle
-> 1 yr
14
Galaxies/cosmology/dark matter/dark energy
The Nature of Dark
Energy
Distribution of galaxies in
the sky have a
characteristic lenght scale
which depends on models
of dark energy
(3.5% HYDROGEN)
Composition of the Universe
SKA Role
Locate and measure spatial
distribution of galaxies via
their hydrogen emission
Galaxies/cosmology/dark matter/dark energy
The Nature of Dark Energy
35.000 galaxies in 3D space to z ~ 1.5 in a 4 h pointing
All sky survey : 109 galaxies
X 1000 Volume improvement
Weak lensing
-- Planck
-- EUCLID
(3.5% HYDROGEN)
Fundamental Physics:
How Gravity works
Pulsars have extreme physical properties:
highest gravitational fields: 200000 x solar
most accurate known clocks : 10-9 s
Physics may be different in strong GR
SKA role:
Blind survey will find 20 000 pulsars
in our Galaxy
-many in binary systems and
exotic systems
1000 millisec pulsars
Fundamental Physics:
How Gravity works
Identify and time pulsars with
nano-second accuracy
• “Find them!”
• “Time them!”
• “VLBI them!”
Test GR
around Black
Holes
-- LIGO
-- LISA
Sensitive
gravity wave
detector
The Origin of Cosmic Magnetism
Magnetism is one of the 4 fundamental forces
Magnetic fields are crucial in:
– Star, galaxy & large scale structure formation
– turbulence & gas motions
– acceleration & propagation of cosmic rays
Fundamental & unsolved problem:
– Exotic origin (phase transitions, strings)
– Seed fields (turbulence, instabilities)
–
Amplification
Magnetic Fields role in star
formation?
The Origin of Cosmic Magnetism
SKA role
Very powerful in the detection of total intensity and
polarized emission and in RM measurements
First detailed 3D picture of cosmic magnetic field:
– Polarization studies of 100 000 000 sources
– 10000 x improvement
•SKA: “instant” RMs and position , σP 0.1 microJy, 100 h obs
 = 1.4 GHz,  = 400 MHz
- for P = 1 μJy :   2.5o, RM  2 rad/m2,
- for P = 10 μJy :   0.3o, RM  0.2 rad/m2
The Cradle of Life
Test conditions for life
elsewhere in the Universe
- Image proto-planetary
disks in formation, movies,
composition
- Probe the ‘Habitable zone’
in disks (mas resolution)
- Detect complex molecules
- Search for Extraterrestial Intelligence:
Airport radars @ 50 l.y.  500 stars
Ionospheric radar @5000 l.y.  600 000 000 stars
Exploration of the unknown
:
Pathfinders
LOFAR : EoR, magnetism, survey
eMERLIN : galaxy evolution (eMERGE)
Precursors
ASKAP : galaxy and BH evolution, LSS,
stars and stellar systems, magnetism
(EMU, POSSUM)
MeerKAT : Pulsar Timing, HI survey,
SFG and AGN
Murchison Widefield Array (MWA)
Jetted AGN studies have been considered a prominent science case for
SKA, and were included in several different chapters of the previous
SKA Science Book (Carilli & Rawlings 2004).
SKA1 will enable such studies for large samples of jets, while VLBI
observations involving SKA1 will provide the sensitivity for pc-scale
imaging, and the full SKA (with its extraordinary sensitivity and
dynamic range) will allow us for the first time to resolve and model the
weakest radio structures in the most powerful radio-loud AGN.
in particular Band 5 receivers in VLBI mode (Paragi et al. 2014) will
provide ∼ milliarcsecond resolution, which corresponds to ∼ parsec
scales for a broad redshift range. The polarization capabilities will be
particularly relevant
Very Long Baseline Interferometry with the SKA
Zsolt Paragi, Leith Godfrey, Cormac Reynolds, Maria Rioja, et al.
Adding VLBI capability to the SKA arrays will immensely broaden the
science of the SKA, and it is entirely feasible. SKA-VLBI can be
initially implemented by providing phased-array outputs for SKA1MID and SKA1-SUR, and using these extremely sensitive stations
with other radio telescopes, and in the full SKA by realising a
distributed configuration providing baselines up to thousands of km,
merging it with existing VLBI networks. The motivation for and the
possible realization of SKA-VLBI is described in this paper.
Flight Cagliari-Bologna, after the EVN symposium