Introduction to 21cm cosmology

1
Constraining cosmological and gravitational
parameters with upcoming astrophysical data
Yi Mao, MIT
Collaborators Max Tegmark, Alan Guth, Matias
Zaldarriaga, Matt McQuinn, Oliver Zahn, Tom
Faulkner, Ted Bunn, Serkan Cabi
2
Outline

• Overview cosmological probes
• 21cm-tomography
• Overview testing gravity
• Testing f(R) gravity
• Testing torsion gravity
• Outlook

Yi Mao Fermilab seminar January 23, 2008
3
What do we learn in cosmology?
Yi Mao Fermilab seminar January 23, 2008
4
0th order Expansion
H(z)
a(t) k
Yi Mao Fermilab seminar January 23, 2008
5
dimmed
Distant light is
distance Vs. z
H(z)
redshifted
6
1st order Clustering
Cl, P(k),
Yi Mao Fermilab seminar January 23, 2008
7
(No Transcript)
8
But the best is yet to come
Precision CMB (polarization, small scales),
precision lensing
and 21cm tomography
Yi Mao Fermilab seminar January 23, 2008
9
21cm tomography
10

• Murchison Widefield Array (MWA)
• Located in western Australia
• 500 antennas array diameters 1500m
• Measures z612

Yi Mao Fermilab seminar January 23, 2008
11
Other arrays

• Square Kilometre Array (SKA)
• Low Frequency Array (LOFAR)
• 21cm Array (21CMA)

Yi Mao Fermilab seminar January 23, 2008
12
21cm line from the Epoch of Reionization
Yi Mao Fermilab seminar January 23, 2008
13
(No Transcript)
14
21cm Power spectrum

• 21cm power spectrum is not isotropic because of
  redshift space distortion!

Yi Mao Fermilab seminar January 23, 2008
15
How accurately can 21cm tomography constrain
cosmological parameters?
Yi Mao Fermilab seminar January 23, 2008
16
Yi Mao Fermilab seminar January 23, 2008
17
K
Yi Mao Fermilab seminar January 23, 2008
YM, Tegmark, McQuinn, Zaldarriaga Zahn (2008)
18
K
Yi Mao Fermilab seminar January 23, 2008
YM, Tegmark, McQuinn, Zaldarriaga Zahn (2008)
19
Ionization power spectrum modeling
Yi Mao Fermilab seminar January 23, 2008
20
OPT
Yi Mao Fermilab seminar January 23, 2008
21
PESS
Yi Mao Fermilab seminar January 23, 2008
22
MID
Yi Mao Fermilab seminar January 23, 2008
YM, Tegmark, McQuinn, Zaldarriaga Zahn (2008)
23
K
Yi Mao Fermilab seminar January 23, 2008
YM, Tegmark, McQuinn, Zaldarriaga Zahn (2008)
24
Optimal array configuration
Yi Mao Fermilab seminar January 23, 2008
25
LOFAR
MWA
SKA
OPT
Size of total inner core
MID
Size of compact core
Yi Mao Fermilab seminar January 23, 2008
YM, Tegmark, McQuinn, Zaldarriaga Zahn (2008)
26
MWA in OPT model
Size of total inner core
Size of compact core
Yi Mao Fermilab seminar January 23, 2008
YM, Tegmark, McQuinn, Zaldarriaga Zahn (2008)
27
Future 3D neutral hydrogen maps?
Yi Mao Fermilab seminar January 23, 2008
28
Testing gravity in a general framework
Yi Mao Fermilab seminar January 23, 2008
29
Generalize PPN

• A general geometry is determined by metric (g)
  and connection (?), both independent of each
  other.
• Three quantities characterize the departure from
  Minkowski spacetime

Yi Mao Fermilab seminar January 23, 2008
30
Generalized geometry family tree
31
Constraining torsion
Yi Mao Fermilab seminar January 23, 2008
32
Parametrization of torsion around Earth
33
Constraining torsion with GPB
34
Constraining torsion with GPB
YM, Tegmark, Guth, Cabi (2006)
35
Constraining f(R) gravity
Yi Mao Fermilab seminar January 23, 2008
36
Solar system constraints on f(R) Chameleon
Faulkner, Tegmark, Bunn and YM (2007)
Yi Mao Fermilab seminar January 23, 2008
37
Constraints on cubic f(R) model
Faulkner, Tegmark, Bunn and YM (2007)
Yi Mao Fermilab seminar January 23, 2008
38
Outlook

• 3D HI mapping direct view into the dark ages,
  precision constraints on cosmological parameters
• Better understanding of the Epoch of Reionization
• New tests of Einstein gravity on scales from the
  solar system to the cosmos
• Common question for cosmology and gravitation
• Dark energy cosmological constant or
  modified gravity?
• Dark matter new particles or TeVeS/MOND?
• Can GR (and standard cosmological model)
  be further tested?

Yi Mao Fermilab seminar January 23, 2008
39
(No Transcript)
40
Yi Mao Fermilab seminar January 23, 2008
Tegmark Zaldarridaga, astro-ph/0207047updates
41
21cm line

• Spin temperature
  , where
• Emission if Ts gt Tcmb absorption if Ts lt Tcmb
• Saturated when Ts gtgt Tcmb arbitrarily large when
  Ts ltlt Tcmb
• The last factor makes the anisotropy!

Yi Mao Fermilab seminar January 23, 2008
42
Ts couplings

• Absorption of CMB photons and stimulated emission
• Collisions with H, e, p Ts ? Tk
• Scattering of UV photons( the Wouthuysen-Field
  Effect) Ts ? TLya

Furlanetto, Oh Briggs 2006
Yi Mao Fermilab seminar January 23, 2008
43
Thermal histroy of IGM

• zdec150 compton heating.
• Tk Tcmb before zdec
  Tk(1z)2 after.
• Z1 Ts Tk before z1 Ts ? Tcmb after.
• Zh IGM Tk gt Tcmb.
• Zc Wouthuysen-Field Effect couples Ts Tk
  again.
• Zr reionization.

Yi Mao Fermilab seminar January 23, 2008