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Cosmology and Future Radio Telescopes
Steve Furlanetto Yale University August 3, 2006


What is Cosmology?
Fundamental Cosmology
Measuring global parameters (, w, H0, etc.)

Astrophysical Cosmology
The history of structure formation (galaxy evolution, reionization, etc.)


Fundamental Cosmology I: The Hubble Constant
Underpins many of improvements over Current state of the project the CMB art: HST key

Systematic-limited at ~10% level

The future: geometric distances from masers (Greenhill 2004)
Measure accelerations and proper motions in accretion disks Hundreds of sources reduce to ~1% errors Requires high frequencies (23 GHz) and long baselines (mapping structure)

Spergel et al. 2006


Fundamental Cosmology II: HI Surveys
Advantages of SKA
Rapid survey speed Spectroscopic redshifts

Half-sky survey to z=1.5
109 galaxies 500 times volume of 2dF

Also weak lensing
Requires 0.1" resolution

Blake et al. 2004

SKA surveys could provide <5% errors on (w0,w1) Can be done in other ways, but not over such large volumes


Astrophysical Cosmology
Big Bang Last Scattering

First Galaxies Reionization Galaxies, Clusters, etc.

Last scattering: z=1089, t=379,000 yr Today: z=0, t=13.7 Gyr Reionization: z=6-20, t=0.2-1 Gyr First galaxies: ?

G. Djorgovski


High-Redshift Galaxies
Arp 220, at z=2, 5, and 8 (LIR~1012 Lsun) Assumes 1 hr integrations Understanding sources will require multiwavelength campaigns
Carilli et al. (2004)


High-Redshift Quasars
1 yr SKA survey at 150 MHz, half-sky, with model luminosity function RLQs above break detected at >1 mJy Also detects all RQQs above break in X-ray luminosity function Other models predict even longer tail to high-z (Haiman et al. 2004)

Carilli et al. (2004)


Beyond Galaxy Surveys
Another key component is the intergalactic medium (IGM)
Contains nearly all of the baryons (More) directly traces matter distribution First galaxies form out of it Influenced by ALL galaxies Affected by feedback from galaxies (radiative, mechanical, chemical) Hallmark event: reionization


Reionization: Observational Constraints
Quasars/GRBs CMB optical depth Ly-selected galaxies

Furlanetto, Oh, & Briggs (2006)


Reionization: Observational Constraints
Quasars/GRBs CMB optical depth Ly-selected galaxies

Furlanetto, Oh, & Briggs (2006)


SDSS Quasars: Line of Sight Variations
SDSS J1030 (z=6.28) SDSS J1148 (z=6.42)
Transmission spikes residual flux! Ly trough: =7-11 Furlanetto 2005) and (Oh & No flux for z=6.2-5.98 >10

White et al. (2003)

Attributed (Wyithe & Fan et al.

to reionization Loeb 2005, 2006)


SDSS Quasars: Line of Sight Variations
But complications!
Aliasing (Kaiser & Peacock 1991) High-k mode

Line of sight High-k mode


SDSS Quasars: Line of Sight Variations
But complications!
Aliasing (Kaiser & Peacock 1991)

Transmission bias because only see through rare voids


SDSS Quasars: Line of Sight Variations
But complications!
Aliasing (Kaiser & Peacock 1991) Transmission bias because only see through rare voids
Smoothing length=40 Mpc/h

Observed variance slightly more than expected from uniform ionizing background
Structure in intrinsic quasar spectra is likely another significant contributor
Lidz, Oh, & Furlanetto (2006)


Reionization: Observational Constraints
Quasars/GRBs CMB optical depth Ly-selected galaxies

Furlanetto, Oh, & Briggs (2006)


Ly Emitters at High Redshifts
Narrowband searches for Ly lines are efficient way to target high-z galaxies
Already effective at z~6.5 Current efforts at z~8-10

HII region around small galaxy HII region around clustered sources

Also teaches us about reionization (Miralda-Escude & Rees 1998, Haiman 2002)
Damping wing absorption from IGM causes galaxy lines to vanish

IGM HI


Ly Emitters
Compare luminosity functions at z=5.7 and z=6.5 Expect difference if substantially neutral IGM
In reality, statistically identical

What are the implications for reionization? Depends sensitively galaxy properties (Santos 2004) Also on clustering (SF, LH, MZ 2004; Gnedin & Prada 2004, Wyithe & Loeb 2005, SF, MZ, LH 2006)

Malhotra & Rhoads (2004)


Reionization: Observational Constraints
Quasars/GRBs
Nearly saturated absorption Sparse background lights

CMB optical depth
Essentially integral constraint

Ly-selected galaxies
Uncertain source populations Small volumes
Furlanetto, Oh, & Briggs (2006)


The 21 cm Transition
Map emission (or absorption) from IGM gas
Spectral line: measure entire history Direct measurement of IGM properties No saturation!
1 + z 1/ 2 TS - Tbkgd H ( z)/(1 + z) Tb 23x HI (1 + ) mK 10 TS v r /r

SF, AS, LH (2004)


21 cm Observations
Challenges
Terrestrial Interference Ionosphere Astronomical Foregrounds
Tb~200-2000 K Galactic synchrotron Extragalactic sources Smooth spectra!

Experiments
Global Signal: CoRE-ATNF Fluctuations: 21CMA, LOFAR, MWA, PAPER, SKA Imaging: SKA

MWA (from C. Lonsdale)


21 cm Observations: Reionization
z=18.3
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=16.1
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=14.5
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=13.2
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=12.1
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=11.2
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=10.4
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=9.8
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=9.2
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=8.7
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=8.3
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=7.9
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=7.5
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


21 cm Observations: Reionization
z=9.2
13 Mpc comoving =0.1 MHz

SF, AS, LH (2004)


Bubble Sizes
Typical galaxy bubble

Bubbles are BIG!!!
xH=0.96

=40

2 Mpc = 1 arcmin

xH=0.70 xH=0.25

Well-defined characteristic size Robust to uncertainties in reionization redshift

SF, MZ, LH (2004a)


Imaging Power
Figure shows fraction of Fourier-space pixels with S/N>1 (1000 hr observation, z=8)
Blue: MWA Red: LOFAR Black: SKA
McQuinn et al. (2006)


The Power Spectrum
Model allows us to compute statistical properties of signal Rich set of information from bubble distribution:
Timing: growth of structure Underlying source population (SF, MM, LH 2005) Uniform ionizing component (SF, MZ, LH 2004b) Feedback (SF, MZ, LH 2004b) Correlation with density field (SF, MZ, LH 2004b)

xi=0.59 xi=0.78 xi=0.48 xi=0.36 xi=0.69

xi=0.13

z=10

Also must consider higherorder statistics!


Error Estimates: z=8
Foreground limit

Survey parameters
MWA

z=8 Tsys=440 K tint=1000 hr B=6 MHz No systematics!

SKA

MWA (solid black)
Aeff=7000 m2 1.5 km core

SKA (dotted blue)
Aeff=1 km2 5 km core


Error Estimates: z=12
Foreground limit

Survey parameters
MWA

z=12 Tsys=1000 K tint=1000 hr B=6 MHz No systematics!

MWA (solid black)
SKA

Aeff=9000 m2 1.5 km core

SKA (dotted blue)
Aeff=1 km2 5 km core


Before Reionization

Pop II Stars

SF (2006)


The Heating Era
X-rays seed fluctuations in TS (and hence Tb)
Discrete (biased) sources and 1/r2 flux Soft X-rays have shorter mean free paths Rapid structure formation

Also imprints features on power spectrum

Pritchard & Furlanetto (2006)


The 21 cm Fundamental

Line and Cosmology

Matter power spectrum at z<20
Additional information on small-scale power spectrum (McQuinn et al. 2006, Bowman et al. 2006)

The REAL "dark ages" (z>50)
Clean power spectrum (Loeb & Zaldarriaga 2004) Sensitive to exotic physics (Furlanetto, Oh, & Pierpaoli 2006)

Weak Lensing
Multiple source screens! (Mandel & Zaldarriaga 2006, Zahn & Zaldarriaga 2006) Small-scale structure


Conclusions
Fundamental Cosmology
True precision measurements of H0 (high frequency, long baselines) HI surveys and weak lensing: dark energy (large field of view) 21 cm tomography as well, but need huge collecting area

Astrophysical Cosmology
High-redshift galaxy surveys 21 cm tomography (low frequencies, large field of view)

See our Physics Reports review (Furlanetto, Oh, & Briggs 2006, astro-ph/0608032) for more information on 21 cm possibilities!