Enhancement of the relic neutrino density in the Milky Way

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Enhancement of the relic neutrino density in the Milky Way

Pablo Fernández de Salas

IFIC – CSIC / Universitat de València

18/07/2017

PFdS, S. Gariazzo, J. Lesgourgues, S. Pastor, arXiv:1706.09850

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Neutrino oscillations

Neutrinos are massive and mixed

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Neutrino masses

●

Neutrinos oscillate in flavor → Δm² ≠ 0

●

Mass scale not known

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Neutrino masses

●

Neutrinos oscillate in flavor → Δm² ≠ 0

●

Mass scale not known

∑ mν <

0.34 eV (Planck TT,TE,EE)

0.17 eV (Planck TT,TE,EE)+BAO Planck collaboration,

Astron.Astrophys. 596 (2016) A107, [arXiv:1605.02985]

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Cosmic Neutrino Background (CNB)

T

^ɣ

= 2.73 K

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Cosmic Neutrino Background (CNB)

Despite their tiny mass T

^ɣ

= 2.73 K

T = 1.95 K

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PTOLEMY

(Princeton Tritium Observatory for Light, Early-Universe, Massive-Neutrino Yield)

●

β-decay of Tritium

●

ν capture on Tritium

S.Betts et al, [arXiv:1307.4738]

� ∝ n

^ν

= n

⁰

f

^clustering

(n

⁰

= 56 cm⁻³)

per neutrino and degree of freedom

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N-1-body simulations

●

The only interaction that matters is gravitational

●

Neutrinos will not affect other neutrinos or DM particles gravitationally

●

DM evolves independently, with no regard of neutrino evolution

●

Discretize neutrino phase-space (Fermi-Dirac statistics)

●

Trace back, rediscretize and resimulate those inside a given R

^cut

●

Repeat until wanted precission is reached

A. Ringwald and Y.Y.Y. Wong, JCAP 0412 (2004) 005, [arXiv:hep-ph/0408241]

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Matter density in the Milky Way (Dark Matter)

●

Dark Matter (DM)



NFW



Einasto

M. Pato, F. Iocco and G. Bertone JCAP 1512 (2015) no.12, 001, [arXiv:1504.06324]

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DM density profile

η = α η = γ

Data from M. Pato and F. Iocco, Astrophys.J. 803 (2015) no.1, L3, [arXiv:1504.03317]

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Matter density in the Milky Way (Baryonic Matter)

●

Baryonic Matter (BM)



dust (warm, cold)



gas (H2, HI)



stars (bulge, disk)

A. Misiriotis etal, Astron.Astrophys. 459 (2006) 113, [arXiv:astro-ph/0607638]

We spherically symmetrize the sum of densities to get ρ

^baryons

(r)

Fit to COBE/DIRBE and COBE/FIRA → ρ(r,z)

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BM density profile

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Local clustering of relic neutrinos

Minimal neutrino masses (60meV)

P.F. de Salas, S. Gariazzo, J. Lesgourgues and S. Pastor, arXiv:1706.09850

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Minimal neutrino masses (60meV)

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Minimal neutrino masses (60meV)

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Degenerate masses (150meV)

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Implications for a PTOLEMY-like experiment

A.J. Long etal, JCAP 1408 (2014) 038 [arXiv:1405.7654]

n

i

= 56 cm⁻³ f

i

Neutrino capture event rates

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A.J. Long etal, JCAP 1408 (2014) 038 [arXiv:1405.7654]

n

i

= 56 cm⁻³ f

i

Neutrino capture event rates

m

ⁱ

= 150meV

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PTOLEMY resolution Δ ~ 0.1eV

S.Betts et al, [arXiv:1307.4738]

A.J. Long, C. Lunardini and E. Sabancilar JCAP 1408 (2014) 038

[arXiv:1405.7654]

r

^SN

≳ 1 for Δ ≲ 0.7 m

^ν

Energy resolution

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Conclusions

●

Relic neutrino clustering for m

ⁱ

= 60 meV (150 meV) at most

~20% (200%)

●

Baryonic contribution is not negligible, but the clustering is more sensitive to the DM halo parametrization

●

Event rate of CNB capture in tritium more sensitive to neutrino mass nature (�

Majorana

= 2�

^Dirac

) than neutrino clustering.

●

A PTOLEMY-like experiment would need a resolution Δ ≲ m

^ν

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Redshift dependence (DM evolution)

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A.A. Dutton and A.V. Macciò, arXiv:1402.7073

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Posteriors MHMCMC

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Sterile neutrino (1.3 eV)

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Local clustering of relic neutrinos

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Neutrino capture event rates

|U

_e4

|

²

= 0.02

m

₄

= 1.3 eV

S. Gariazzo, C. Giunti, M. Lavender and Y.F.

Li, [arXiv:1703.00860]