Interactions Between UHE Particles and Protogalaxy Environments

Interactions between UHE Particles and Protogalaxy Environments

Ellis Owen Mullard Space Science Laboratory University College London United Kingdom E-mail: [email protected]

Kinwah Wu, Idunn Jacobsen, Pooja Surajbali

Image Credit: NASA - Adolf Schaller Hubble gallery Artist’s impression of protogalaxies

HEPP/APP University of Sussex, Brighton, United Kingdom, March 2016 Outline

1. UHE Particles in Protogalaxies 2. Protogalaxy Environments 3. Interaction Mechanisms & Losses 4. Energy Deposition Lengths & ISM/IGM Heating

2 Ultra High-Energy Particles in Protogalaxies

• Cosmic Rays (CRs) accelerated in high energy astrophysical environments – Supernovae explosions / shocks – Accretion • Particle energy distribution follows power law, peaks around ~10 GeV for galactic (stellar) contribution • Expected to be present in young starburst galaxies (protogalaxies) – High star formation rate (SFR) ~1000 times more than cosmic average – Rate of supernovae roughly follows SFR – Cosmic ray flux attributed to stellar sources roughly follows supernova rate

3 102

2 101 10 Protogalaxy Environment 3 0 Density Fields 10 101 King radius

• King model 102 3

1 10 101 100

ParameterMatter Value Density/cm 3 rt 2kpc 100 r 1kpc2 K 10 1 10

3 Matter Density/cm 1 n0 10 cm 10

2 10 Matter Density/cm

3 • Red line at King radius,10 1kpc 3 10 3 2 1 0 1 3 2 1 0 1 10 1010 10 1010 10 1010 10 – Approximate radius of a Radius/kpc 2 Radius/kpc protogalaxy (e.g. from high z 10 LAE observations)

4 10 3 3 2 1 0 1 10 10 10 10 10 Radius/kpc 102

101 Protogalaxy Environment 3 0 r>rgal Radiation Fields 10 7

• Uniform spherical 67 distribution of stars1 within 6 10 1 5

protogalaxy 1 s

Matter Density/cm 5 2 s 2

• High mass, low metallicity 44 – O/B type, T~30,000K 2 10 3 – T Spectrally characterizes 3

radiation field (BB spectrum) Flux/erg cm 2

Flux/erg cm 2 • Field approximately uniform 1 3 within the protogalaxy10 radius, 3 10 2 1 0 1 then simple inverse 10square 100 2 4 10 6 8 1010 10 Radius/kpc law at r>r Radius/kpc gal 0 0 2 4 6 8 10 Radius/kpc 5 5 10

7 10

Protogalaxy Environment9 10

11 10 Efficiency of energy transfer Magnetic Fields 5 10 13 10 SNe à Turbulence à B field 7 10 15 • Two scale components:10 5 9 1010 17 -3 7 – Local viscous scale, 10~10 pc 1011 10 10 9 19 10 1113 – Turbulent forcing ~1kpc 1010 21 10 13 10 15 10 • SN driven, B follows density 15 10 23 17 Forcing Scale, ✏ =0.1 10 1010 17 profile 19 25 10 19 Viscous Scale, ✏ =0.1 10 10 -20 21 • Initial B field ~10 G 10 Forcing Scale, ✏ =1 21 27 23 Forcing Scale, ✏ =0.1 10 1010 Protogalaxy Magnetic Field Strength/G permeates protogalaxy Viscous Scale, ✏Viscous=0.1 Scale, ✏ =1 25 29 10 23 Forcing Scale, ✏ =0.1 10 10 Forcing Scale, ✏ =1 27 10 Forcing Scale, ✏ = 10 Protogalaxy Magnetic Field Strength/G • Stellar processes drive 25 Viscous Scale, ✏ =1 Viscous Scale, ✏ =0.1 31 29 1010 10 Forcing Scale, ✏ = 10 Viscous Scale, ✏ = 10 31 Forcing Scale, ✏ =1 turbulence, which drives B 10 27 Viscous Scale, ✏ = 10 33 10 10 Protogalaxy Magnetic Field Strength/G 33 4 3 10 2 1 0 1 2 3 Viscous4 Scale,5✏ =1 4 3 2 1 0 1 2 3 4 5 10 10 102910 10 1010 10 10 10 1010 10 1010 1010 10 10 10 field up to µG levels seen in 10 Age of Galaxy/Myr Forcing Scale, ✏ = 10 Age of Galaxy/Myr current epoch 31 10 Viscous Scale, ✏ = 10 10 33 – Exponential growth 4 3 2 1 0 1 2 3 4 5 10 10 10 10 10 10 10 10 10 10 – Then linear growth of the forcing scale Age of Galaxy/Myr field after local saturation Model follows J. Schober + 2013 6 5 10

7 10

Protogalaxy Environment9 10

11 10 Efficiency of energy transfer Magnetic Fields 5 10 13 10 SNe à Turbulence à B field 7 10 15 • Two scale components:10 5 9 1010 17 -3 7 – Local viscous scale, 10~10 pc 1011 10 10 9 19 10 1113 – Turbulent forcing ~1kpc 1010 21 10 13 10 15 10 • SN driven, B follows density 15 10 23 17 Forcing Scale, ✏ =0.1 10 1010 17 profile 19 25 10 19 Viscous Scale, ✏ =0.1 10 10 -20 21 • Initial B field ~10 G 10 Forcing Scale, ✏ =1 21 27 23 Forcing Scale, ✏ =0.1 10 1010 Protogalaxy Magnetic Field Strength/G permeates protogalaxy Viscous Scale, ✏Viscous=0.1 Scale, ✏ =1 25 29 10 23 Forcing Scale, ✏ =0.1 10 10 Forcing Scale, ✏ =1 27 10 Forcing Scale, ✏ = 10 Protogalaxy Magnetic Field Strength/G • Stellar processes drive 25 Viscous Scale, ✏ =1 Viscous Scale, ✏ =0.1 31 29 1010 10 Forcing Scale, ✏ = 10 Viscous Scale, ✏ = 10 31 Forcing Scale, ✏ =1 turbulence, which drives B 10 27 Viscous Scale, ✏ = 10 33 10 10 Protogalaxy Magnetic Field Strength/G 33 4 3 10 2 1 0 1 2 3 Viscous4 Scale,5✏ =1 4 3 2 1 0 1 2 3 4 5 10 10 102910 10 1010 10 10 10 1010 10 1010 1010 10 10 10 field up to µG levels seen in 10 Age of Galaxy/Myr Forcing Scale, ✏ = 10 Age of Galaxy/Myr current epoch Exponential31 growth 10 Linear growth Viscous Scale, ✏ = 10 10 33 – Exponential growth 4 3 2 1 0 1 2 3 4 5 10 10 Local10 saturation10 10 10 10 10 10 10 – Then linear growth of the forcing scale Age of Galaxy/Myr field after local saturation Model follows J. Schober + 2013 6 Interaction Mechanisms & Losses

• Low energy particles – Collisions • Direct ionization • Heating • High energy particles – Proton-photon (p�) • Pion production (Photopion) • Pair production (Photopair) – Proton-proton (pp) • Pion production (Hadronuclear)

7 Interaction Mechanisms & Losses Photopion (��) Interaction

0 + p + ⇡ p +2 + pion multiplicities at p + ! higher energies ! ! n + ⇡+ n + µ+ + ⌫ ( ! µ + Photopair (�e) Interaction n + e + ⌫e +¯⌫µ + ⌫µ

+ p + p + e + e . !

8 Interaction Mechanisms & Losses Hadronuclear (pp) Interaction

p + p + ⇡0 p + + p + p + ⇡+ 8 ! 8 p + p > <>p + n + ⇡+ + pion multiplicities ! > at higher energies > + < ++ >n + p + ⇡ n + : + > ! (n + n + 2(⇡ ) > > :>

9 Interaction Mechanisms & Losses Hadronuclear (pp) Interaction

p + p + ⇡0 p + + p + p + ⇡+ 8 ! 8 p + p > <>p + n + ⇡+ + pion multiplicities ! > at higher energies > + < ++ >n + p + ⇡ n + : + > ! (n + n + 2(⇡ ) > > :> Interactions of neutrons and photons à pion production n + ⇡’s ! 9 Interaction Mechanisms & Losses Hadronuclear (pp) Interaction

p + p + ⇡0 p + + p + p + ⇡+ 8 ! 8 p + p > <>p + n + ⇡+ + pion multiplicities ! > at higher energies > + < ++ >n + p + ⇡ n + : + ! (n + n + 2(⇡ ) > > > : Pions decay to photons, muons, Interactions of neutrons and neutrinos, electrons, positrons, photons à pion production antineutrinos n + ⇡’s ! ⇡ ,µ,e,⌫ ... ! 9 Cross Section/Mean Free Path � Interactions

• Pair production, Bethe-Heitler 7 ✏ (✏ ) ↵ ln r process e r ⇡ 6⇡ f T k ✓ e ◆ – Cross Section by fitting function

10 Cross Section/Mean Free Path � Interactions

• Pair production, Bethe-Heitler 7 ✏ (✏ ) ↵ ln r process e r ⇡ 6⇡ f T k ✓ e ◆ – Cross Section by fitting function • Photopion production – Cross section by fitting step function to data (Dermer & Menon 2009/Reimer 2007)

10 Cross Section/Mean Free Path � Interactions

• Hadronuclear production – Cross section by fitting to data (Kafexhiu+ 2014)

10 105 105

102 102

10 1 10 1 UHE Proton Loss Lengths Energy104 Deposition & IGM/ISM Heating 4 4 10 10 Mean Free Path of UHE Protons 103 10 7 10 7 Contributions Magnetic Field UHE Proton Loss Lengths 104 10 2 10 5 10 10 10 10102 103 1010-22 2 13 10 2 13 1 10 10 1 10 10 10 10-8 4 10 101 16 16 7 10 10 10 100 0 Energy Loss Mean Free Path/Mpc 10 Energy Loss Mean Free Path/Mpc 10 10 19 Hadronuclear (p⇡) 19 1 20 13 20 10 10 10 10 Seed Magnetic Field,Galactic 10 Radiation HadronuclearG Photopion (⇡) (p⇡) Seed Magnetic10-22 Field, 10 G 1 Galactic Radiation Photopair (e) 10 16 102 5 5 10-2 SaturationEnergy10 Loss Mean Free Path/Mpc Magnetic Field, 10 G Saturation Magnetic Field, 10 G 22 CMB RadiationGalactic Photopion (⇡) Radiation Photopion22 (⇡) Energy Loss Mean Free Path/Mpc 10 10 19 10 20 CMB Radiation Photopair (e) Seed Magnetic Field, 10 G 3 No Magnetic10 Field Galactic Radiation Photopair (e) No Magnetic Field 5 CMB Radiation Cosmological Expansion 22 Saturation Magnetic Field, 10 G 2 10 25 10 Total 25 No Magnetic Field 10 Energy Loss Mean Free Path/Mpc CMB Radiation Photopion10 (⇡) 4 25 9 10 1110 12 13 14 15 9 16 10 17 111018 12 19 13 20 14 15 16 17 18 19 20 10 10 10 109 101010 1011 101012 1013 101014 1015101016 10101710 101810101019 102010 10 109101010 101110 101012 101013 1014 101015 1016 1017 1018 101019 1020 10 10 10 CMBProton RadiationProton Energy/eV Energy/eV Photopair (e) ProtonProton Energy/eV Energy/eV 3 Owen+(in prep) 10 CMB Radiation Cosmological Expansion

• AssumeTotal products decay quickly at interaction point 4 •10 Energy of CR deposited ~at point of interaction 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 11 Proton Energy/eV 23 23 10 10 25 25 10 10 27 27 10 10

29 29 10 10

19 1 19 1 31 31 10 10 10 10 s s 3 3 33 Energy21 Deposition33 & IGM/ISM21 Heating 10 10 10 10 23 10 35 35 Preliminary Estimated23 Heating Impact10 25 23 10 10 10 10

Local Scales 27 Large Scales 10 37 37 19 10 23 10 10 10 25 29 25

1 10 10 1 1025 10 21 10 1 Heating/erg cm s Heating/erg cm 31 s 39 10 27 0Myr 39 s 10 3

10 3 10 23 3 10 27 33 10 29 27 1Myr 10 10 25 10 1 1 10 31 10 Myr 10 s 41 s 41 35 3 3 10 10 10 27 33 100 Myr 10 10 29 37 29 29 10 35 1000 Myr 10 10 43 43

10 10 Heating/erg cm 37 UV Comparison 31 39 10 10 10 Heating/erg cm Heating/erg cm 39 10 33 31 41 31 45 10 10 45 1041 10 10 10 35

Heating/erg cm 43 10 Heating/erg cm 10 43 10

37 10 45 47 33 47 45 10 33 10 10 10 10 10 1 39 2 1 47 3 2 3 10 10 10 1 100 10 47 1 1 10 102 3 10 10 10 10 10 10 10 10 1 2 3 Radius/kpcRadius/kpc 10 10 Radius/kpc 10 10 35 35 Radius/kpcRadius/kpc • CR energy density 10-3 x radiation 10

37 37 • Impact10 of magnetic fields 10 – Determines whether the CRs are able to escape or not 39 39 10 10 1 0 1 1 0 1 10• Escape: heat IGM (possible implications10 for10 cosmic reionization) 10 10 10 • No escape: heat ISM (possibleRadius/kpc implications for star formation in galaxy) Radius/kpc 12 – There is a window of a few Myr for the CRs to escape Summary

• Cosmic ray protons thought to be accelerated in protogalaxy environments – Supernova shocks, ISM turbulence… • Energy spectrum peaks ~few x 10 GeV • CRs can interact collisionally, or by pp, p� interactions (pair production & pion production) • Drives energy deposition & heating • CRs shown to have non-negligible heating impact on their medium • Effect increasingly trapped within protogalaxy as magnetic field evolves – But a window of a few Myr allows initial escape into the Intergalactic medium causing heating over larger scales

13 References

• Dermer & Menon (2009) – High Energy Radiation from Black Holes: Gamma-Rays, Cosmic Rays and Neutrinos, Princeton Series in Astrophysics • A. Reimer (2007) - The Redshift Dependence of Gamma-Ray Absorption in the Environments of Strong-Line AGNs, ApJ, 665, 1023 • Kafexhiu+ (2014) - Parametrization of gamma-ray production cross sections for pp interactions in a broad proton energy range from the kinematic threshold to PeV energies, Phys. Rev. D 90, 123014 • Schober+ (2013) - Magnetic field amplification in young galaxies, A&A 560, A87 • Owen+ (in prep) – Interactions between Ultra High Energy Particles and Protogalaxy Environments, MNRAS