Search Results and Prospects from Atmospheric Cherenkov

Telescopes

Andrew W Smith University of Marland, College Park / NASA GSFC

From P5 report (Cosmic Frontier) Arrenberg et al.

Indirect Detection probes a wide range of theory space in DM

In an ideal situation, DM

should produce a

very recognizable

signal in gamma rays

Imaging Atmospheric Cherenkov Technique:

Primary gamma rays initiate EM showers w

particle v>c: Cherenkov pulses

HESS (Prague WG) Arrenberg et al.

Current TeV Experiments

VERITAS Southern AZ, USA 4x12m

MAGIC-II Canary Islands 2 x 17m

HESS-II Namibia

4x12.5, 1x 28

* Energy range: ~80 GeV to >30 TeV

* Energy resolution: 15% at 1 TeV * observation time per year: ~1200

hours * point source sensitivity: 1% Crab

in <30h, 10% in <30 min

Rough Performance Valuesfor Current Generation IACTs

Instrumental PSF

= ~600 ɣ/hr (0.1-50 TeV) in footprint of array

Current IACTs can detect (5σ) sources producing 6 ɣ/hr in 25 hrs

Indirect Detection of DM w/IACTs

Assume all the 𝛾s you didnt see is

this:Constrain this

Choose some ppp model to tell

you what you should have seen

Find an real astronomer to model this for

you

M𝜒

σv

Constraint s= Discrete SUSY parameter scan results.

Above curve = disallowed model

Indirect Detection of DM w/IACTs

This term is very sensitive to

fluctuations in methods progress?

Significant progress

M𝜒

σv

Constraint s= Discrete SUSY parameter scan results.

Above curve = disallowed model

What have we learned about this

equation?

Target Advantages Disadvantages

Galactic Center Close by, lots of DM Large 𝛾 BG

Galactic Substructure

Possibly local, Fermi-LAT sources Unknown distance, nature

Galaxy Clusters-Largest DM

concentrations in universe

-very distant (weak signal) -very extended -possible 𝛾 BG

Dwarf Galaxies -High Mass/Light -No likely 𝛾 BG

DM distribution can be very uncertain

IACT DM Targets

Target Advantages Disadvantages

Galactic Center Close by, lots of DM Large 𝛾 BG

Galactic Substructure

Possibly local, Fermi-LAT sources Unknown distance, nature

Galaxy Clusters-Largest DM

concentrations in universe

-very distant (weak signal) -very extended -possible 𝛾 BG

Dwarf Galaxies -High Mass/Light -No likely 𝛾 BG

DM distribution can be very uncertain

IACT DM Targets

Galactic Center

HESS >300 GeV

Peak of DM profile

2011 Abramowski et al. 112 Hours of H.E.S.S. Data

254 Hours of H.E.S.S. data 2015 Le Franc et al (ICRC)

HESS II

VERITAS Galactic Center (> 2 TeV)

VERITAS Observations will constrain multi-Tev

parameter space

VERITAS 100 hr estimate

Dwarf Spheroidal Searches

from Drlica-Wagner 2014/Ackermann et al 2015 and

source therein

J ~ (DM density profile)2 along line of sight

NFW Profile, 0.50 integration radiusSagittarius

from Drlica-Wagner 2014/Ackermann et al 2015 and

source therein

Sagittarius

HESSMAGIC

VERITAS

Dwarf Spheroidal Searches

Dwarf Spheroidal Searches

from Drlica-Wagner 2014/Ackermann et al 2015 and

source therein

Sagittarius

All 3 IACTs have accrued ~150-200 hrs

on dSphs.

MAGIC (165 hrs on Segue I) (Aleksic et al 2015)

VERITAS 215 hours on 4 dSphs Zitzer et al 2015)

HESS Combined Limits: 140 hours on 5 targets

(Abramowski et al 2014)

MAGIC (165 hrs on Segue I) (Aleksic et al 2015)

VERITAS 215 hours on 4 dSphs Zitzer et al 2015)

HESS Combined Limits: 140 hours on 5 targets

(Abramowski et al 2014)

Aleksic et al 2014

Likelihood methods improve limits by 2-3

MAGIC (Einasto)

VERITAS HESS

NATURAL CROSS SECTION

IACT Dwarf Spheroidal Limits

𝝌 𝝌 -> 𝜏+ 𝜏-

NFW

MAGIC (EInasto)

VERITASHESS dSph

NATURAL CROSS SECTION

HESS GC

𝝌 𝝌 -> 𝜏+ 𝜏-

NFW

IACT Dwarf Spheroidal Limits

Limits on 𝞆 𝞆 -> ɣ ɣ

HESS GC

VERITAS dSPHs

MAGIC Segue I

Where can we go from here?

MOU in preparation between IACTs

to combine data, joint likelihood methods may

improve limits on full data set

Where can we go from here?

CTA Design (S array)

Low energies Energy threshold 20-30 GeV 23 m diameter 4 telescopes (LST’s)

Medium energies 100 GeV – 10 TeV

9.5 to 12 m diameter 25 single-mirror telescopes

up to 24 dual-mirror telescopes (MST’s/SCTs)

High energies 10 km2 area at few TeV

3 to 4m diameter 70 telescopes

(SST’s)

Science Optimization under budget constraints

Hinton & Funk arXiv:1205.0832

HESS / VERITAS 100 hrs

Hinton & Funk arXiv:1205.0832

HESS / VERITAS 100 hrs

300 h

Galactic Plane Survey

525 h

300 h Fermi bubbles

Galactic PlaneSurvey

In the first 3 years of

observations, CTA will

observe the GC for >500

hours

Thermal DM

CTA

con

sorti

um, i

n pr

epar

atio

n

CTA GC Limits

CTA will probe deep into natural cross section within 3 years of operation

Silverwood, et al., JCAP 03, 055 (2015) Lefranc, et al., PRD 91, 12 (2015)

Summary-Current Generation of IACTs have developed and executed a multi-year DM search program (still in

progress)

-These programs (significant) have set deep limits, although still mostly separate from the natural cross section. Progress on combining limits.

-These programs have paved the way for upcoming searches with CTA, this search will

probe deep into the natural cross section within the first few years of operation