Imaging HII Regions During Reionizaion with SKA1-low

Imaging HII Regions During
Reionizaion with SKA1-low
Stuart Wyithe
with thanks to
Paul Geil
Hansik Kim
Greg Poole
Image: Paul Geil
SKA science, June 2014
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Galaxies at high redshift
HUDF, Rogier Windhorst
Bouwens et al. (2012)
• How do galaxy properties connect to the structure of reionization?
SKA science, June 2014
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Galaxy bias and patchy reionization
Evolution in ionization given
by the difference between
ionization and recombination
QHII
SKA science, June 2014
3
Wyithe & Loeb (2007)
Galaxy bias and patchy reionization
Evolution in ionization given
by the difference between
ionization and recombination
Star formation follows structure
formation, which is subject to galaxy
bias, and so sensitive to environment
C=2
C=10
C=20
QHII
• Overdense regions of IGM are reionized first
SKA science, June 2014
3
Wyithe & Loeb (2007)
The largest observable HII regions
Variance in formation redshift
δz
2 1/ 2
σR
=
(1+ z)
δc (z)
Redshift corresponding to light travel time
δz
€
2 1/ 2
dz R
=
dt c
light travel time = variance in formation time
•
There is a surface on the sky corresponding to the redshifts along different
lines of sight where the IGM was most recently neutral
•
HII regions at the End of Reionization had a characteristic scale of ~0.5-1 degree
€
SKA science, June 2014
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Wyithe & Loeb (2004)
“Structure” of reionization is sensitive
to the source population
Barkana et al. (2007)
•
Formation of biased HII regions means that reionization should leave a distinct
mark on the power-spectrum of spatial fluctuations in 21cm emission
• How do galaxy properties connect to the structure of reionization?
SKA science, June 2014
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GALFORM semi-analytic galaxy formation
& semi-numerical reionization modeling
(1) The gravitationally driven assembly of dark matter haloes;
(2) The density and angular momentum profiles of dark matter and hot gas in haloes;
(3) The radiative cooling of gas and its collapse to form centrifugally supported disks;
(4) Star formation in disks;
(5) Feedback processes, from injection of energy from Supernovae (SNe) and AGN;
(6) Chemical enrichment of the ISM and hot halo gas;
(7) The dynamical friction on orbits of satellite
galaxies and their possible merger;
(8) The formation of galactic spheroids;
(9) The spectrophotometric evolution of stellar
populations;
(10) The effect of dust extinction on galaxy
luminosities and colours;
SKA science, June 2014
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Often assumed relation
GALFORM semi-analytic galaxy formation
& semi-numerical reionization modeling
Hansik Kim (2012, 2014)
Model without SNe feedback
•
Model with SNe feedback
The ionized structure is sensitive to galaxy formation properties, including
SNe or radiative feedback
SKA science, June 2014
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Imaging reionization with SKA1-low:
Galaxy formation with SNe feedback
base-line
SKA science, June 2014
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1/2 base-line
Imaging reionization with SKA1-low:
Galaxy formation with SNe feedback
base-line
SKA science, June 2014
8
1/2 base-line
Imaging reionization with SKA1-low:
Galaxy formation with no SNe feedback
base-line
SKA science, June 2014
9
1/2 base-line
Imaging reionization with SKA1-low:
Galaxy formation with no SNe feedback
base-line
SKA science, June 2014
9
1/2 base-line
Imaging reionization with SKA2
SKA science, June 2014
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Summary
• Studying reionization by imaging the ionisation structure of the neutral intergalactic medium is a realistic goal for SKA1-low
• The properties of HII regions are sensitive to galaxy formation physics, and
imaging of the ionisation structure will provide a clear discriminate between
different galaxy formation scenarios
• SKA1-low will image HII regions expected from galaxy formation models
which include strong feedback on low mass galaxy formation, while imaging
the smaller HII regions that result from galaxy formation in the absence of
SNe feedback may be more challenging
• The field of view for SKA1-low should be at least several degrees in order to
image the largest HI structures towards the end of reionization
SKA science, June 2014
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