# Presentation: 480895

## Dark matter physics  from 

- Dark matter physics  from
- gamma-ray all sky surveys

**Savvas M. Koushiappas**
- T-6 & ISR-1 Los Alamos National Laboratory

*EGRET*

*GLAST*

## What can be learned from something like this?

## What can be learned from something like this?

- A lot of ***high energy astrophysics***

## What can be learned from something like this?

- A lot of ***high energy astrophysics***

- Perhaps something about the  Dark matter

## What can be learned from something like this?

- A lot of ***high energy astrophysics***

- Perhaps something about the  Dark matter

- Look at resolved sources

## What can be learned from something like this?

- A lot of ***high energy astrophysics***

- Perhaps something about the  Dark matter

- Look at resolved sources

- Look at the diffuse background

## What can be learned from something like this?

- A lot of ***high energy astrophysics***

- Perhaps something about the  Dark matter

- Look at resolved sources: *Structure and substructure of dark matter halos*

- Look at the diffuse background: *The origin of the background->Angular fluctuations*

## What is the Universe made up of?

- <date/time>

- Inflation

- Cosmic microwave background

- Large scale structure

- Gravitational lensing

- Lyman-alpha forest

- Galaxy cluster abundance

- Big Bang nucleosynthesis

- Supernovae

- Rotation curves

- Weak lensing

## Gamma-ray friendly dark matter candidate: Lightest neutralino

- Gamma-ray friendly dark matter candidate: ***Lightest neutralino***

## <footer>

- <date/time>

## Constributing factors:

- The dwarf satellite “problem” and its disputable existance

- From Kravtsov, Gnedin & Klypin, ApJ, 609, 482 (2004), but see also Klypin et al. (1991),  Bullock, Kravtsov & Weinberg (2000), Benson et al.(2001), Somerville (2001)

- _Constributing factors:_

-  Changing the *properties* of dark matter
-  Modifying the *spectrum* of density fluctuations
-  *Feedback** *mechanisms

- More massive

- Klypin et al. (1999), Moore et al. (1999)

- Figure courtesy James Bullock

## The Milky Way substructure

- Cosmology sets the formation time, and therefore the distribution and properties of dark halo substructure:
**Uncertainties in cosmological parameters result in uncertainties in the modelling of dark substructure**

- More luminous in gamma rays

- Spread in radius

- Spread in luminosity

- From SMK, Zentner & Walker (2004)

- M(t)/M0

- R(t)/R0

## The Milky Way substructure

- Cosmology sets the formation time, and therefore the distribution and properties of dark halo substructure:
**Uncertainties in cosmological parameters result in uncertainties in the modelling of dark substructure**

- From Calcaneo-Roldan & Moore (1999)

## If                              a detection must rely on serendipitous discovery 

-  If *     *                         then                   detectable subhalo per *GLAST* field of view, need a *450 hour* exposure with ***VERITAS**** *to  detect the line emission.

- If                              a detection must rely on ***serendipitous*** discovery

***GLAST***

***GLAST***

***VERITAS***

***VERITAS***

## If                       then there will be              detectable subhalo per GLAST field of view-need a 450 hour  exposure with VERITAS to detect the line emission. 

- If                       then there will be              detectable subhalo per ***GLAST*** field of view-need a 450 hour  exposure with ***VERITAS*** to detect the line emission.

## Q: How can this be done better?

- If                       then there will be              detectable subhalo per ***GLAST*** field of view-need a 450 hour  exposure with ***VERITAS*** to detect the line emission.

## Q: How can this be done better?

- If                       then there will be              detectable subhalo per ***GLAST*** field of view-need a 450 hour  exposure with ***VERITAS*** to detect the line emission.

- Design an instrument like ***VERITAS***, but with an effective area of ***5(10) times larger***. Then the exposure needed to detect the line will be only ***90(45) hours***!!

## Why not the LMC or the galactic center?

- Wilkinson et al. (2006)

- Fainter

- More dark matter dominated

- Radius from the center

- Circular velocity

**Why not the LMC or the galactic center?**

- There is a disc
- There is potentially a bar
- Baryons dominate, hence not clear as to what the dark matter distribution is

- Disk

- Disk

**LMC**

- From Alves & Nelson (2000)

## Local group dwarf spheroidal systems 

- From Strigari et al., astro-ph/0603775

- Local group dwarf spheroidal systems

- _Line-of-sight projection_

- L.O.S. velocity

- Increasing radius away from the center

- Line of sight velocity dispersion

- Dwarf spheroidals are easier to study because they are dark matter dominated

- Fornax

## Draco dSph

- Strigari, SMK, Bullock & Kaplinghat, in preparation (2006)

**Draco dSph**

- Increasing mass

- Increasing luminosity

- Large degeneracy between cusped and cored profiles

- Core? But where?

- From Strigari et al., astro-ph/0603775

## Improved angular resolution can map the dark matter profile

- Profumo & Kamionkowski, astro-ph/0601249

- CACTUS measurement 1 deg angular res.

- Dark matter halos are predicted to be described by Universal profiles.

- Test this picture using a suite of local group dwarf galaxies

- If gamma-rays originate from WIMP annihilation, profiles must be cusped!!!!!

## Draco dSph

- From Strigari, SMK, Bullock & Kaplinghat, in preparation (2006)

**Draco dSph**

- Increasing mass

- Increasing luminosity

- Large degeneracy between cusped and cored profiles

- Core? But where?

- From Strigari et al., astro-ph/0603775

## Current GLAST prospects call for a 0.1-0.5 sigma detections from within the inner 0.3deg of Draco

## Q: How can this be done better?

- Current GLAST prospects call for a 0.1-0.5 sigma detections from within the inner 0.3deg of Draco

## Q: How can this be done better?

- Current GLAST prospects call for a 0.1-0.5 sigma detections from within the inner 0.3deg of Draco

- Design an instrument like ***GLAST***, with an effective area of ***10******3****** times larger ***and an angular resolution of ~5’. Then observe many local dwarves to determine the universality of the central dark matter distribution.

## Gamma-ray background fluctuations

- Z=3

- Z=1

- Z=0.5

- Z=0

- Scale-dependent bias

- Larger scales

- More strongly clustered

- Comoving emissivity

- Correlation function

- From Ciardi, Miniati & Di Matteo (2004)

## GLAST ~ few x 1000

- Gamma-ray luminosity function-model dependent

- Use correlations between X-ray (e.g. Hasinjer et al. (2005)) and radio (e.g. Salamon & Stecker (1996)) properties of blazars, or fit the redshift distribution (e.g. Chung & Mukherjee (1998))of EGRET blazars

## Gamma-ray background fluctuations

- Z=3

- Z=1

- Z=0.5

- Z=0

- Scale-dependent bias

- Larger scales

- More strongly clustered

- Comoving emissivity

- Correlation function

- From Ciardi, Miniati & Di Matteo (2004)

## Fluctuations in the gamma-ray background provide 

- Fluctuations in the gamma-ray background provide
- information about the source of the background

- From Ando & Komatsu, astro-ph/0512217

- Smaller scales

- More power

- Fluctuations ~ 20%

- From Miniati, SMK & Di Matteo, in preparation, 2006

## It may be impossible to identify the source of the gamma-ray background if the dark matter is the neutralino

## Q: How can this be done better?

- It may be impossible to identify the source of the gamma-ray background if the dark matter is the neutralino

## Q: How can this be done better?

- Design an instrument like ***GLAST***, with a reasonably high angular (~5’) and frequency (<10%) resolution and with 106 times (Aefftexp) in order to identify the background through the line emission of SUSY dark matter background angular fluctuations

- It may be impossible to identify the source of the gamma-ray background if the dark matter is the neutralino

## Summary

- Probing the Milky Way dark substructure
- Dark matter distribution in halos
- Source of the gamma-ray background

- Not promising, but not impossible

- Worst, but perhaps not impossible

- Perhaps identified, difficult if it is the dark matter distribution

- Based on current experiments

- What is needed

- Survey to identify the sources (***GLAST***) + a ***VERITAS*** class instrument with ***A******eff ******x 10***

- A ***GLAST*** instrument with an ***A******eff ******x 10******3 ***and with an angular resolution of ***~ 5 arcmin***

- A ***GLAST*** instrument with an ***A******eff******x10******6***!!