lyman series photons (+ x-rays) and the 21 cm signal
DESCRIPTION
Lyman series photons (+ X-rays) and the 21 cm signal. Jonathan Pritchard (CfA). Collaborators: Steve Furlanetto (UCLA) Avi Loeb (Harvard). Mario Santos ( CENTRA - IST) Alex Amblard (UCI) Hy Trac (CfA) Renyue Cen (Princeton) Asantha Cooray (UCI). Overview. - PowerPoint PPT PresentationTRANSCRIPT
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Lyman series photons (+ X-rays)
and the 21 cm signal
Jonathan Pritchard (CfA)
Collaborators: Steve Furlanetto (UCLA) Avi Loeb (Harvard)
Mario Santos (CENTRA - IST) Alex Amblard (UCI) Hy Trac (CfA)
Renyue Cen (Princeton) Asantha Cooray (UCI)
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2STSc
IMAR
2009
Overview
1. 21 cm basics2. What effect do Lya and X-rays have on the 21cm signal?3. How well do analytic models of the 21 cm signal match
simulations?
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3STSc
IMAR
2009
21 cm basics
•21 cm brightness temperature
•21 cm spin temperature
•Use CMB backlight to probe 21cm transition
z=13fobs=100 MHzf21cm=1.4 GHz
z=0
TS TbT
HITK
•3D mapping of HI possible - angles + frequency
•Coupling mechanisms: Radiative transitions (CMB) Collisions Wouthuysen-Field
10S1/2
11S1/2
n0
n1
n1/n0=3 exp(-h21cm/kTs)
•HI hyperfine structure
=21cm
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4STSc
IMAR
2009
Wouthuysen-Field effect
Lyman
Effective for J>10-21erg/s/cm2/Hz/sr
Ts~T~Tk
W-F recoils 20P1/2
21P1/2
21P1/2
22P1/2
10S1/2
11S1/2 Selection rules: F= 0,1 (Not F=0F=0)
Hyperfine structure of HI
Field 1959
nFLJ
~21 cm
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5STSc
IMAR
2009
Thermal History
e.g. Furlanetto 2006
Measure withEDGESBowman+ 2008
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6STSc
IMAR
2009
21 cm fluctuationsBaryonDensity
Gas Temperature
W-FCoupling
Neutralfraction
Velocitygradient
X-raysources
Lysources
ReionizationCosmology Cosmology
Dark AgesTwilight
Brightnesstemperature
b
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7STSc
IMAR
2009
Sources of radiation
dV
Barkana & Loeb 2005, Pritchard & Furlanetto 2006Hirata 2006
Three contributions to Ly flux: continuum & injected from stars + x-rayLya:
X-ray: Chen & Miralde-Escude 2006, Pritchard & Furlanetto 2007, Zaroubi+ (2007)Pritchard & Loeb 2008
• Source properties very uncertain
X-rays from mini-quasars, starburst galaxies, IC
Lya heating typically small than that of X-rays
Mpc
X-ray photoionization leads to 2ry ionization, heating, Lya
Fluctuations: • Despite long mfp significant fluctuations due to 1/r2 flux dependence and clustering of sources
Chen & Miralde-Escude 2006 Chuzhoy & Shapiro 2006
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8STSc
IMAR
2009
Power spectrabias source properties density
Barkana & Loeb 2004Chuzhoy, Alvarez, & Shapiro 2006Pritchard & Furlanetto 2007
• Fluctuations in Lya or X-rays both add power on large scales• Largest scales gives bias of sources• Intermediate scales says something about sources e.g. stellar spectrum vs power law• T fluctuations say something about thermal history
Lya
TK<T
TK>T
X-rays
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9STSc
IMAR
2009
Signal decomposition
FullLya
T
xi
density
Peculiar velocities
Barkana & Loeb 2005
Bharadwaj & Ali 2004Angular separation by
Pritchard & Loeb 2008
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10STSc
IMAR
2009
Reionization simulation
L=100 Mpc/hNDM=28803
Mhalo=108 Msol/hRT on 3603 grid
Shin+ 2007Trac & Cen 2007Santos+ 2008
Resolves halos capableof atomic cooling
• Simulation techniques for reionization well developed• Boxes well matched to typical bubble sizes ~1-10Mpc• Including Lya and X-rays complicated by long mfp & need to track multiple frequencies and redshifting -> numerically expensive
(Baek+ 2009 - Included Lya radiative transfer into course 100 Mpc box, no X-rays)
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11STSc
IMAR
2009•Approach:
Implement semi-analytic procedure for fluxes using SFR from N-body simulation Extract sources on time slices and integrate to get Lya & X-ray flux
Convolution can be evaluated relatively quicklySource parameters extrapolated from low z sources - Pop II + III stars -> reionization at z=6 - X-ray emission from galaxies Get coupling and heating from fluxes
Including other radiation fields
Santos, Amblard, Pritchard, Trac, Cen, Cooray 2008
t
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12STSc
IMAR
2009
Simplifications• Propagate in mean density IGM
Underestimates heating close to source & overestimates far away
Semelin, Combes, Baek 2007Chuzhoy & Zheng 2007Naoz & Barkana 2007
• Both will tend to increase power on small scales important for details, but not overall picture
Scattering in wings tends tosteepen radial dependenceof flux
• Propagate Lyman photons until redshift to line center
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13STSc
IMAR
2009
Full simulation
Movie courtesy of Mario Santos
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14STSc
IMAR
2009
Evolution of signal
• T fluctuations significantly shift mean TB at moderate z• Different fluctuations important at different times• On smallest scales evolution mostly modulated by Tb
Mean signal Power spectrum
Tcmb TK
TS
w/ T
onlyTB
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15STSc
IMAR
2009
Lya
• Analytic model underestimates SFR slightly -> less Lya -> weaker signal
• In both cases Lya fluctuations flatten P(k)
Dotted = +xi
Dashed = +X-rayDot-dashed = +LyaSolid= All
theory simulation
z=20.60 xi=0.0002 z=15.24 xi=0.03
z=10 xi=0.35 z=7.4 xi=0.84
Dotted = +xi Dot-dashed = +LyaDashed = +X-ray Solid= All
z=20.60 xi=0.0002 theory
simulation
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16STSc
IMAR
2009
Lya/T
• Lya fluctuations match well• T fluctuations disagree somewhat
-> cross correlation between T and density too strong on small scales in analytic model
• Modeling needs improvement
theory simulation
z=20.60 xi=0.0002 z=15.24 xi=0.03
z=10 xi=0.35 z=7.4 xi=0.84
Dotted = +xi Dot-dashed = +LyaDashed = +X-ray Solid= All
theory
simulation
z=15.24 xi=0.03
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17STSc
IMAR
2009
Temperature
• Ionization fluctuations agree very well with FZH model • Temperature fluctuations more important in simulation -> large scales still close to CMB temperature -> contributes with opposite sign to ionization so power reduced
(hottest regions ionized)
z=10 xi=0.35 theory
simulation
Dotted = +xi Dot-dashed = +LyaDashed = +X-ray Solid= All
Furlanetto, Zaldarriaga, Hernquist 2004
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18STSc
IMAR
2009
Ionization
•Good agreement except on largest scales •Bubble size comparable to box size -> problems•Echoes previous comparisons of FZH model for ionization
theory
simulation
z=7.4 xi=0.84
Dotted = +xi Dot-dashed = +LyaDashed = +X-ray Solid= All
Zahn+ 2007
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19STSc
IMAR
2009
Conclusions• Have told a simple story, but large uncertainties with sources
•Learn about sources during/preceding reionization from fluctuations in Lya and X-ray flux from details of power spectra
-> constrain faint population of early sources-> thermal history
• Results suggest weak separation of different fluctuations -> details parameter dependant
• Temperature fluctuations can be important at even low neutral fractions-> may need both Lya heating & X-ray heating
• Theory and simulation agrees reasonably well-> fast method for including relevant physics in simple way-> need for RT of Lya and X-rays in cosmological simulations-> analytic calculations valuable for fast exploration of
parameters
• Using 21 cm fluctuations to understand early stages of reionization requires understanding contribution of Lya and X-rays
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20STSc
IMAR
2009
Transition redshiftsLya Temperature
• Onset of Lya fluctuations less parameter dependent• Lya coupling precedes heating same for fluctuations • X-rays couple & Lya photons heat (if no X-rays)
= =T
Pritchard & Loeb 2008
X-rays
Lya
Lya
X-rays
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21STSc
IMAR
2009
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22STSc
IMAR
2009
Comparison of Fluctuations
uniform Lya X-ray
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23STSc
IMAR
2009
Higher order terms• Ionization fluctuations are not small XH~1• Higher order (in X) terms modify P21 on all scales
- important to include in modeling
Lidz+ 2007Santos+ 2008
Green=fullDashed = h.o.t.Solid=standard
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24STSc
IMAR
2009
Temporal evolutionDark agesReionizationPost-reionization
Signal from denseneutral clumps at low z
Pritchard & Loeb 2008
Chang et al. 2007Wyithe & Loeb 2007
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25STSc
IMAR
2009
Simulation + Lya +X-rays
Santos, Amblard, JRP, Trac, Cen, Cooray 2008
Lya & T fluctuationscan be important