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Probing Dark Matter With Radio Observations Chorng-Yuan Hwang 黃黃黃

Probing Dark Matter With Radio Observations

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Probing Dark Matter With Radio Observations. C horng-Yuan Hwang 黃崇源. Why do we need Dark Matter (DM)?. Rotation curve of Milky Way and galaxies Mass of galaxy clusters Large scale structures of the Universe Cosmological model - PowerPoint PPT Presentation

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Page 1: Probing Dark Matter With Radio Observations

Probing Dark Matter With Radio Observations

Chorng-Yuan Hwang

黃崇源

Page 2: Probing Dark Matter With Radio Observations

Why do we need Dark Matter (DM)?

Rotation curve of Milky Way and galaxies

Mass of galaxy clusters Large scale structures of the Universe Cosmological model Modified Newtonian Dynamics (MOND)

might explain rotation curves but not large scale structures and CMB

Page 3: Probing Dark Matter With Radio Observations

Dark matter in galaxy

About 90% of the mass of galaxies is in the form of dark matter, which can not be observed.

The flat rotation curve of the Milky Way suggests that the dark halo of the Milky might distribute:

Total M r (r) r-2

Page 4: Probing Dark Matter With Radio Observations

Rotational Curve of Milky Way

Page 5: Probing Dark Matter With Radio Observations

Rotation Curves of Four Spirals

Page 6: Probing Dark Matter With Radio Observations

Clusters in Optical

Page 7: Probing Dark Matter With Radio Observations

Dark Matter In Galaxy Clusters

Page 8: Probing Dark Matter With Radio Observations

Dark Matter in Large-Scale Structures

Page 9: Probing Dark Matter With Radio Observations

Dark Matter in the Universe (Hinshaw et al 2009) (WMAP)

Page 10: Probing Dark Matter With Radio Observations

Fluctuations of CMB (Hinshaw et al 2009)

(WMAP)

Page 11: Probing Dark Matter With Radio Observations

Other Models/Theories

Modified Newtonian Dynamics (MOND) This might explain the rotation curves of

galaxies but is difficult to explain the large scale structures and CMB

It is not excluded that both dark matter and MOND are necessary.

Page 12: Probing Dark Matter With Radio Observations

Dark Matter Distribution

N-body simulation of dark matter halo structure:

NFW profile:

Cusp profile (Diemand 2007):

Page 13: Probing Dark Matter With Radio Observations

What is the Dark Matter (DM)? DM must be non-baryonic DM must be cold A viable candidate for the DM is the

Weakly Interacting Massive Particles (WIMPs).

The most favorable WIMPs are the neutralino predicated in the supersymmetric (SUSY) extension of the standard model and Kaluza-Klein particles.

Page 14: Probing Dark Matter With Radio Observations

Neutralino

A linear combination of two neutral higgsinos and two gauginos.

= B + W + H1 + H2

The most likely mass of is between ~ 50 GeV to 1 TeV

Self-annihilation of will decay into fermion pairs or gauge boson pairs and will finally become gamma ray, electrons and positrons.

Page 15: Probing Dark Matter With Radio Observations

Kaluza-Klein particles

Particles from compact extra dimension. the mass of the lightest Kaluza–Klein

particle is expected to be greater than 300 GeV

The annihilation of Kaluza–Klein particles can proceed through direct production of electron-positron pairs resulting in a source spectrum that is dominated by a delta function at the particle mass.

Page 16: Probing Dark Matter With Radio Observations

Prediction and Observations of DM: Difficult to detect directly

Page 17: Probing Dark Matter With Radio Observations

(CDMSII Collaboration 2010)

Page 18: Probing Dark Matter With Radio Observations

Relativistic electrons positrons decayed from DM If is the relic particle from the hot big bang

and constitute the DM, then the self-annihilating cross section is related to the abundance of dark matter

mh2 =h2 = 310-27 cm2 s-1/<v> From WMAP, mh2 =0.127, so the self-

annihilation cross section of is about <v> = 2.36 10-26 cm2 s-1

We might observe the resulting electrons and -rays that can be compared with models!

Page 19: Probing Dark Matter With Radio Observations

Where to Observe the DM

Simulations suggest that DM is clumped into sub-halos down to the Earth mass with a size of the solar system.

DM mass in clumps ~ 50% of total mass in halos

dN/dM ~ M-2

The source function is proportional to n2

Even small DM sub-halos can produce significant relativistic electrons and -rays!

Page 20: Probing Dark Matter With Radio Observations

Diemand et al 2007

Missing Subhalos?

Page 21: Probing Dark Matter With Radio Observations

Dark halo mass distribution (Diemand et al 2005)

Page 22: Probing Dark Matter With Radio Observations

Illuminating Dark Halos?

Page 23: Probing Dark Matter With Radio Observations

Electron/positron spectra

Source function:

Evolution of electrons:

Stationary spectra:

Page 24: Probing Dark Matter With Radio Observations

Equilibrium positron spectra in Milky Way from the annihilation of 100GeV using clumpy model of Diemand et al 2005

Page 25: Probing Dark Matter With Radio Observations

Equilibrium positron spectra in Milky Way from the annihilation of 1TeV using clumpy model of Diemand et al 2005

Page 26: Probing Dark Matter With Radio Observations

Spectrum of cosmic-ray electrons

Page 27: Probing Dark Matter With Radio Observations

ATIC results (2008): Kaluza-Klein particles?

Page 28: Probing Dark Matter With Radio Observations

Kaluza-Klein particles with mass of 620 GeV? (Chang et al 2008; ATIC)

Page 29: Probing Dark Matter With Radio Observations

FERMI Results (Abdo et al 2009)

Page 30: Probing Dark Matter With Radio Observations

Radio emission of electrons and positrons from decayed DM

Most of the astronomical objects have magnetic fields.

Relativistic electrons in magnetic fields can produce radio emission.

We can estimate the resulting radio emission and compare with radio observations of galaxies and galaxy clusters.

Page 31: Probing Dark Matter With Radio Observations

Radio Halos

Some clusters show radio halos from synchrotron radiation of relativistic electrons of unknown origins.

large scale and steep spectrum. 1/3 of clusters with mass > 1015 solar mass

show radio halos Magnetic fields in all clusters are ~ 5-

10G

Page 32: Probing Dark Matter With Radio Observations

A2163

Feretti (2003)

Page 33: Probing Dark Matter With Radio Observations

Models for Emission of DM Halo from Nearby galaxy Clusters and galaxies

Select several nearby rich clusters with measured X-ray profile and mass

Assume B=5 G and steady state NFW profile <v> = 2.36 10-26 cm2 s-1

n = mass density/m

m =100GeV – several TeV

subhalo mass: ~ 1012-10-4 M

Page 34: Probing Dark Matter With Radio Observations

Source functions of Coma main halo for 2TeV , solid line for fermion channels and dashed line for boson channels

Page 35: Probing Dark Matter With Radio Observations

Source functions of Coma halo for 100GeV , solid line for fermion channels and dashed line for boson channels

Page 36: Probing Dark Matter With Radio Observations

Self-Annihilation flux from CDM of Coma cluster

Page 37: Probing Dark Matter With Radio Observations

Self-Annihilation flux from CDM of A754 cluster

Page 38: Probing Dark Matter With Radio Observations

Self-Annihilation flux from CDM of A85 cluster

Page 39: Probing Dark Matter With Radio Observations

Self-Annihilation flux from a 1011 M DM halos at z=0.02

Page 40: Probing Dark Matter With Radio Observations

Conclusion and Summary

The predicted radio halo emission from the self-annihilation of DM neutralinos could be detectable.

The non-detection of radio halos for some massive clusters with high magnetic fields might be used to constrain the properties of the DM neutralinos or/and to constrain the structure formation models of the universe.

Page 41: Probing Dark Matter With Radio Observations

The End