Radio astronomy: Probing the  Cosmic Reionization
Download
1 / 30

Radio astronomy: Probing the Cosmic Reionization Manchester, Oct 2007 Chris Carilli (NRAO) - PowerPoint PPT Presentation


  • 110 Views
  • Uploaded on

Radio astronomy: Probing the Cosmic Reionization Manchester, Oct 2007 Chris Carilli (NRAO). Ionized. Neutral. Reionized. Chris Carilli (NRAO) Berlin June 29, 2005. WMAP – structure from the big bang. Hubble Space Telescope Realm of the Galaxies.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Radio astronomy: Probing the Cosmic Reionization Manchester, Oct 2007 Chris Carilli (NRAO)' - joben


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Radio astronomy: Probing the Cosmic Reionization

Manchester, Oct 2007

Chris Carilli (NRAO)

Ionized

Neutral

Reionized


Chris Carilli (NRAO)

Berlin June 29, 2005

WMAP – structure from the big bang



  • Last phase of cosmic evolution to be explored

  • Benchmark in cosmic structure formation indicating the formation of the first luminous objects.

  • HI 21cm line is most direct, incisive probe of structure formation during, and process of, reionization.

  • Radio(cm/mm) observations reveal the gas, dust, star formation, and AGN in the earliest galaxies

Dark Ages

Cosmic reionization


Constraint I: Gunn-Peterson Effect

End of reionization?

f(HI) > 1e-3 at z = 6.3

f(HI) < 1e-4 at z= 5.7

Fan et al 2006


Constraint II: CMB large scale polarization: Thompson scattering during reionization

  • Scattered CMBquad. => polarized

  • Horizon scale => 10’s deg

  •  = 0.09+/-0.03 => zreion = 11+/-3

TT

TE

EE

Fan et al 2003

Page + 06


OI

  • Not ‘event’ but complex process, large variance: zreion ~ 14 to 6

  • Good evidence for qualitative change in nature of IGM at z~6

ESO


3, integral measure?

Geometry, pre-reionization?

Local ionization?

OI

Abundance?

Saturates, HI distribution function, pre-ionization?

Local ioniz.?

  • Current probes are all fundamentally limited in diagnostic power

  • Need more direct probe of process of reionization = HI 21cm line

ESO


Studying the pristine IGM into the EOR using redshifted HI 21cm observations (100 – 200 MHz)

  • Large scale structure:

  • cosmic density, 

  • neutral fraction, f(HI)

  • Temp: TK, TCMB, Tspin

  • Heating: Ly, Xrays, shocks


Signal I: Global (‘all sky’) reionization signature in low frequency HI spectra

IGM heating: T_spin=T_K > T_CMB

Lya coupling: T_spin=T_K < T_CMB

Gnedin & Shaver 03

21cm ‘deviations’ < 1e-4 wrt foreground


Signal II: HI 21cm Tomography of IGM Zaldarriaga + 2003

z=12

9

7.6

  • T_B(2’) = 10’s mK

  • SKA rms(100hr) = 4mK

  • LOFAR rms (1000hr) = 80mK


Signal III: 3D Power spectrum analysis

d only

LOFAR

d + f(HI)

SKA

McQuinn + 06


Cosmic Webafter reionization

Ly alpha forest at z=3.6 (d < 10)

Womble 96

N(HI) = 1e13 – 1e15 cm^-2, f(HI/HII) = 1e-5 -- 1e-6

=> Before reionization N(HI) =1e18 – 1e21 cm^-2


Signal IV: Cosmic web before reionization: HI 21Forest

19mJy

z=12

z=8

130MHz

  • radio G-P (=1%)

  • 21 Forest (10%)

  • mini-halos (10%)

  • primordial disks (100%)

  • expect 0.05 to 0.5 deg^-2 at z> 6 with S_151 > 6 mJy


‘Pathfinders’: PAST, LOFAR, MWA, PAPER, …

MWA (MIT/ANU)

LOFAR (NL)

PAST (CMU/China)

PAPER Berk/NRAO


Challenge I: Low frequency foreground – hot, confused sky

Eberg 408 MHz Image (Haslam + 1982)

Coldest regions: T = 100 (n/200 MHz)^-2.6 K

Highly ‘confused’: 1 source/deg^2 with S_0.14 > 1 Jy


  • Solution: spectral decomposition (eg. Morales, Gnedin…)

  • Foreground = non-thermal = featureless over ~ 100’s MHz

  • Signal = fine scale structure on scales ~ few MHz

Signal/Sky ~ 2e-5

10’ FoV; SKA 1000hrs

Cygnus A

500MHz

5000MHz

Simply remove low order polynomial or other smooth function?


Challenge II: Ionospheric phase errors: varying e- content

TID

100”

-100”

74MHz Lane 03

  • ‘Isoplanatic patch’ = few deg = few km

  • Phase variation proportional to wavelength^2

  • Solution: Wide field ‘rubber screen’ phase self-calibration


Solution – RFI mitigation: location, location location

100 people km^-2

1 km^-2

0.01 km^-2


First galaxies: ALMA/EVLA CO redshift coverage

Epoch of Reionization:

First galaxies: standard molecular transitions redshift to cm regime

  • Total gas mass

  • Gas dynamics

  • Gas excitation

  • High density gas tracers


First galaxies -- Radio astronomy into cosmic reionization

z ~ 6 QSO host galaxies: molecular gas and dust

VLA

z=6.42

50K

PdBI

FWHM=350 km/s

Radio-FIR correlation

  • Mdust ~ 1e8 Mo

  • Dust heating: star formation or AGN?

  • Follows Radio-FIR correlation: SFR ~ 3000 Mo/yr

  • Giant reservoirs of molecular gas ~2e10 Mo = fuel for star formation.

  • Currently: 2 solid detections, 2 likely at z~6


J1148+52: VLA imaging of CO3-2

VLA imaging of gas at subkpc resolution

0.4”res

rms=50uJy at 47GHz

1” 5.5kpc

0.15” res

  • Not just circumnuclear disk.

  • Mdyn~ 4e10Mo ~ Mgas>> Mbulge ~1e12 Mo predicted by M-

  • Separation = 0.3” = 1.7 kpc

  • TB = 20K => Typical of starburst nuclei


[CII] 158um ISM gas cooling line at z=6.4

30m 256GHz Maiolino etal

  • C+ = workhorse line for z>6 galaxies with ALMA

  • Structure identical to CO 3-2” (~ 5 kpc) => distributed gas heating = star formation?

  • SFR ~ 6.5e-6 L[CII] ~ 3000 Mo/yr

CII PdBI Walter et al.

CII + CO 3-2

1”


Higher Density (>1e4 cm^-3) Tracers: HCN, CN, & HCO+,

HCN 1-0

HCO+ 1-0

Riechers

  • Linearly correlated with FIR => dense gas directly associated with star forming clouds

  • Lines 5-10x fainter than CO

  • ncr > 1e7cm^-3 for higher orders => higher order not (generally) excited?

  • Dense gas tracers best studied with cm telescopes

200uJy


The need for collecting area: pushing to normal galaxies at high redshift -- spectral lines

cm telescopes: low order molecular transitions

(sub)mm: high order molecular lines + fine structure lines


The need for collecting area: continuum high redshift -- spectral lines

A Panchromatic view of galaxy formation

Arp 220 vs z

cm: Star formation, AGN

(sub)mm Dust, molecular gas

Near-IR: Stars, ionized gas, AGN


Radio astronomy – Reionization and 1st galaxies high redshift -- spectral lines

  • ‘Twilight zone’: study of first light limited to near-IR to radio wavelengths

  • First constraints: GP, CMBpol => reionization is complex and extended: z_reion = 6 to 14

  • HI 21cm: most direct probe of reionization

  • Low freq pathfinders: All-sky, PS, CSS, Abs

  • SKA: imaging of IGM

  • First galaxies: cm/mm -- gas, dust, star formation, AGN


Signal VI: high redshift -- spectral lines pre-reionization HI signal: ‘richest of all cosmological data sets’ eg. Baryon Oscillations (Barkana & Loeb)

  • Very difficult to detect !

  • z=50 => n = 30 MHz

  • Signal: 30 arcmin, 50 mk =>S_30MHz= 0.1 mJy

  • SKA sens in 1000hrs:

  • T_fg = 20000K =>

  • rms = 0.2 mJy

z=50

z=150


Destination: Moon! high redshift -- spectral lines

  • No interference (ITU protected zone)

  • No ionosphere (?)

  • Easy to deploy and maintain (high tolerance electronics + no moving parts)

10MHz

Needed for probing ‘Dark ages’:

z>30 => freq < 50 MHz

RAE2 1973


ad