Probing Dark Matter with
Cosmic Messengers
Andrea Albert
Los Alamos National Lab
3rd KMI International
Symposium
January 6, 2017

Outline• Indirect Detection Overview– evidence for dark matter– dark matter candidates– indirect detection messengers• Recent Dark Matter Results– unexplained anomalies– current constraints• Future Gamma Ray Prospects
Andrea Albert (LANL)

2DARK MATTER AND DARK MATTERPARTICLE CANDIDATESAndrea Albert (LANL)

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Dark Matter Primer•

Galaxies form in large Dark Matter halos,
which make up most of their mass
– Coma Cluster + Virial, F. Zwicky (1937)– Rotation Curves, V. Rubin et al 1980)• Dark Matter is virtually collisionless– The Bullet Cluster,D. Clowe et al (2006)
www4.nau.e•

Dark Matter is non-baryonic– CMB acoustic oscillations– Big Bang nucleosynthesis
Andrea Albert (LANL)

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Dark Matter Primer•

Galaxies for in large Dark Matter halos, whichmake up most of their mass
– Coma Cluster + Virial, F. Zwicky (1937)
simulationof a spiralgalaxy createdwith UniverseSandbox– Rotation
Curves,V. Rubin
et al 1980) 2• Dark Matter is virtually collisionless– The Bullet Cluster,D. Clowe et al (2006)
www4.nau.e•

Dark Matter is non-baryonic– CMB acoustic oscillations– Big Bang nucleosynthesis
Andrea Albert (LANL)

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Dark Matter Primer•

Galaxies for in large Dark Matter halos, whichmake up most of their mass
– Coma Cluster + Virial, F. Zwicky (1937)– Rotation Curves, V. Rubin et al 1980)• Dark Matter is virtually collisionless– The Bullet Cluster,D. Clowe et al (2006)
www4.nau.e•

Dark Matter is non-baryonic– CMB acoustic oscillations– Big Bang nucleosynthesis
Andrea Albert (LANL)

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Dark Matter Primer•

Galaxies No
for Darkin large
Dark Matter halos, which
Mattermake up most of their mass

ΛCDM

– Coma Cluster + Virial, F. Zwicky (1937)– Rotation Curves, V. Rubin et al 1980)

CMB temp fluctuations• Dark Matter is virtually collisionlesssimulated with CAMB
https://lambda.gsfc.nasa.gov/toolbox/
tb_camb_form.cfm– The Bullet Cluster,D. Clowe et al (2006)
www4.nau.e

Planck measurement

CAMB simulations•

Dark Matter is non-baryonic– CMB acoustic oscillations– Big Bang nucleosynthesis
Andrea Albert (LANL)

7DM Structures are Present
on Many Scales
Zoom Sequence of DM Structure on 100 Mpc Scales

Milky Way-like Halo and Several Sub-Halos• DM clumps :• On cosmological scales (left)• In the Milky Way virial radius(~300 kpc = ~1 MLY, right)(Visible size of MW = ~ 20 kpc)
(M31 is ~800 kpc away)
slide credit: Eric Charles (SLAC)

Left: Boylan-Kolchin+ 2009MNRAS.398.1150B
Right: Springel+ 2008MNRAS.391.1685S
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Dark Matter Candidates• Wide variety of particle DM
candidates in beyond SM
theories• Large scale structureand galactic formation
seem to require cold
(non-relativistic) DM• Tend to focus on 100 GeV
WIMPs– but lack of detection at e.g.
LHC and LUX motivatesneed for other candidates
with mDM >10 TeV
Andrea Albert (LANL)

Baer+ PR 555 (2015)9

Dark Matter Candidates• I will focus on WIMP results,
but other DM candidates canleave cosmic signatures– axion and axion-like-particles
couple to rays in B fields– x-ray lines from sterile– -ray lines from gravitinos• Recall all DM results arederived from firmmeasurements– DM limits from flux limits– Important for experiments topublish measured limits andfluxes that are not convolved
with DM model assumptions
Baer+ PR 555 (2015)
Andrea Albert (LANL)

10WIMP Dark Matter• Weakly Interacting Massive Particle(WIMP, )– GeV - TeV mass scale– WIMPs may be thermal relics– e.g. neutralino (SUSY, electricallyneutral, stable)• Assuming a weak scale ann at freeze
yields observed relic abundancetime in early
Universe whenamount of DM
freezes outout– < v>ann ~ 3x10-26 cm3/s
E. Kolb and M. Turner, The Early
Universe, Westview Press (1994)

arXiv:1202.1170
arXiv:1405.1730• Sommerfeld enhancement– relevant for high DM masses (>~1 TeV)
– enhanced at low WIMP velocities•this effect was suppressed at timeof freeze out– high mass thermal relics have present< v>ann larger than 3x10-26 cm3/s insome models
Andrea Albert (LANL)

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Various Dark Matter Search Techniques
time

χ
time

DirectDetection(undergrounddetectors)

χSMProduction(collider)?
Indirect
DetectionSM
timeVarious Dark Matter Search Techniques
time

χ
time

DirectDetection(undergrounddetectors)

χSMProduction(collider)?
Indirect
DetectionSM
time

Indirect Dark Matter Detection
Spectral line

Broad spectrum• The Milky Way sits in a large haloof cold DM (vDM << c)–Expect additional DM overdensities (halos / subhalos)•e.g. Milky Way dwarf galaxies•e.g. Galaxy Clusters• WIMP annihilations (decays) may produce gamma rays
Andrea Albert (LANL)

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Indirect Dark Matter Detection
Spectral line

Broad spectrum

Pro: Gamma rays and neutrinos pointback to their source so we can look forexcesses from known DM targets.
Can bedifficult• Con:The MilkyWaysits intoadisentangle
large halo
from
non-DM(e.g. pulsars) fromof cold
DM (vsources<<c)DM
those targets–Expect additional DM overdensities (halos / subhalos)•e.g. Milky Way dwarf galaxies•e.g. Galaxy Clusters• WIMP annihilations (decays) may produce gamma rays
Andrea Albert (LANL)

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Indirect Dark Matter Detection
Spectral line

Broad spectrum

Pro: Positrons and antiprotons comefrom relatively nearby DM interactions,so are only subject to local DM density
uncertainties• The Milky Way sits in a large halo
Con:
Chargedmatter/antimatterlose
of cold
DM (vDM<< c)source direction information in Galactic–Expect additional DM overdensities (halos / subhalos)
magnetic
field. Difficult to disentangle•e.g. Milky Way dwarf galaxies
from non-DM sources•e.g. Galaxy Clusters• WIMP annihilations (decays) may produce gamma rays
Andrea Albert (LANL)

16OVERVIEW OF RECENT RESULTS

Andrea Albert (LANL)

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Local Positron Fraction

S.Schael (AMS Coll) TeVPA 2016

AMS Collaboration (2016)
http://www.ams02.org/wpcontent/uploads/2016/12/Fig2.png• AMS-02 on board the International Space Station observes local cosmic rays since 2011
– excellent charge resolution and particle species discrimination• TeV e-e+ lose energy quickly and therefore must be produced locally (d < ~100 pc)– secondaries produced by cosmic ray interactions with ISM (spallation)– primaries produced by local source• local cosmic accelerator (e.g. Geminga)? local dark matter interactions?

• Larger positron flux observed above ~10 GeV than expected from secondaries– First observed by Pamela in 2009, since confirmed by Fermi LAT and AMS-02– Are they from a local cosmic accelerator or dark matter?
• If they are from dark matter, other annihilation products should be producedLocal Positron Fraction

http://www.ams02.org/wpcontent/uploads/2016/12/Fig4.png

S.Schael (AMS Coll) TeVPA 2016

• AMS-02 on board the International Space Station observes local cosmic rays since 2011
– excellent charge resolution and particle species discrimination• TeV e-e+ lose energy quickly and therefore must be produced locally (d < ~100 pc)– secondaries produced by cosmic ray interactions with ISM (spallation)– primaries produced by local source• local cosmic accelerator (e.g. Geminga)? local dark matter interactions?

• Larger positron flux observed above ~10 GeV than expected from secondaries– First observed by Pamela in 2009, since confirmed by Fermi LAT and AMS-02– Are they from a local cosmic accelerator or dark matter?
• If they are from dark matter, other annihilation products should be producedCosmic Neutrinos“Bert”“Ernie”

Aartsen+ [IceCube Collab]
EJPC 76, 531 (2016)• With the detection of Bert and Ernie by IceCube in 2014, we entered the era of cosmic
neutrino astronomy– before the only extra-solar neutrinos came from SN1987a• Expect brightest neutrino signal from DM annihilations from the Galactic Center– no neutrino excess observed towards the GC• Recent limits from IceCube constrain DM models proposed to explain local positrons– gamma ray limits from dwarf galaxies (more later) are more constraining, but it’s
important to have multi-messenger constraints from various targets

Cosmic Neutrinos“Bert”

Aartsen+ [IceCube Collab]
EJPC 76, 531 (2016)“Ernie”

Albert+ [ANTARES Collab]
submitted to Phys B Lett
arXiv:1612.04595• With the detection of Bert and Ernie by IceCube in 2014, we entered the era of cosmic
neutrino astronomy– before the only extra-solar neutrinos came from SN1987a• Expect brightest neutrino signal from DM annihilations from the Galactic Center– no neutrino excess observed towards the GC• Recent limits from IceCube constrain DM models proposed to explain local positrons– gamma ray limits from dwarf galaxies (more later) are more constraining, but it’s
important to have multi-messenger constraints from various targets

“GeV Excess” in the Galactic Center?
Via Lactea II, Kuhlen et al.,Science 325:970-973,2009

Fermi LAT >1 GeV, 6 years, Pass 8 data

Excess emission spectrum peaks around 3 GeV

Goodenough &HooperPhys.Lett. B697
(2011)

Abazajian &Kaplinghat
PRD 87 129902(2012)

Calore et al.
Gordon & Macias
JCAP 1503
PRD 88, 083521(2015)(2013)
Hooper & Slatyer
Daylan et al.
Phys.Dark Univ. 2
Phys. Dark Univ.
(2013)
12 (2016)

Ajello et al.
(The Fermi-LAT
Collaboration)
ApJ 819 1 44 (2016)

Dark matter annihilation, unresolved sources, CR electrons?
– Mirabal (MNRAS 436 (2013) 2461), Petrovic et al. (JCAP 1502 (2015) 02,023), Cholis et al. (JCAP
1512 (2015) 12, 005), Lee et al. (PRL 116 051103 (2016)), Bartels et al. (PRL 116 051102 (2016)),
Brandt & Kocsis (ApJ 812 (2015) 1, 15), Carlson et al. (arXiv:1510.04698) etc.
Andrea Albert (LANL)

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“GeV Excess” in the Galactic Center
Spectra averaged over entire sky

A.Albert+ [Fermi LAT Collab] IAU GC 2016
galacticcentre.space/index.php/programme/

Calore+ PRD 91 063003 (2015)• Excess of GeV gamma rays from the GC above standard models first detected byGoodenough & Hooper in 2009 in the Fermi Large Area Telescope data
– If interpreted as DM annihilation, mDM ~ 50 GeV with ‘WIMP miracle’ cross section value• Currently not clear if it is from DM or non-DM sources– Complicated region of the sky and the community is working hard to disentangle a
potential DM component• ~85% of the gamma rays at 1 GeV are from fore/backgrounds– DM is a small component of the gamma-ray sky, so precision modeling of the non-DM
components is necessary to tease out DM component in the Galactic Center

Milky Way Dwarf Spheroidal Galaxies

Optical Luminosities
from 103L⍟ to 107L⍟

A.Drlica-Wagner
DPF 2013
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6 year Fermi LAT dSphs Results
The Fermi LAT Collab
PRL 115, 23 (2015)• Joint likelihood analysis of 15 well characterized dwarf galaxies• Limits exclude thermal relic < v>ann in bƃ channel for
5 GeV < m < 100 GeV

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TeV Gamma-ray DM Constraints

uncertainty on DM
density in the GC

Abdallah+ [H.E.S.S. Collab] PRL 117 11 (2016)• For gamma-rays from 500 GeV to 5 TeV, best sensitivity comes from Air
Cherenkov Telescopes (ACTs, e.g. H.E.S.S.)• H.E.S.S. located in the southern hemisphere can observe the Galactic Center– No DM-like excess observed, strong constraints placed– Limits for DM annihilation to tau leptons now constrain ‘WIMP miracle’ models(assuming Einasto profile)TeV Gamma-ray DM Constraints

uncertainty on DM
density in the GC

Abdallah+ [H.E.S.S. Collab] PRL 117 11 (2016)• For gamma-rays from 500 GeV to 5 TeV, best sensitivity comes from Air
Cherenkov Telescopes (ACTs, e.g. H.E.S.S.)• H.E.S.S. located in the southern hemisphere can observe the Galactic Center– No DM-like excess observed, strong constraints placed– Limits for DM annihilation to tau leptons now constrain ‘WIMP miracle’ models(assuming Einasto profile)

>TeV Gamma-ray Constraints
1 year HAWC limits

excluded• For gamma-rays >5 TeV, best sensitivity comes from the High Altitude Water
Cherenkov Observatory (HAWC)– HAWC has a wide field of view making it sensitive to extended objects– HAWC surveys ⅔ of the sky every day, including several DM targets• No excesses observed, limits extend out to the highest DM masses– will be able to test DM decay models proposed to explain the IceCube neutrinos• Typically PeV mass DM with lifetime ~ 1e27 s
e.g. A. Esmaili+ (2013) arXiv:1308.1105, K. Murase+ (2015) 1503.04663v2

FUTURE GAMMA RAY PROSPECTS

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Upgrade to HAWC Observatory
A. Sandolval arXiv:1509.04269~60 TeV gamma ray eventfrom the Crab Nebula• Upgrade to HAWC array is underway–increase collection area with sparse array of small tanks• Provide better measure of highest energy air showers–expected gain in sensitivity above 10 TeV of 3-4–will allow HAWC to search for the highest energy gamma-ray ever observed

The Cherenkov Telescope Array• CTA is a next-generation gamma-ray observatory• International Consortium combines existing ACT expertise• Plan for Northern and Southern array -> full sky coverage– sites will be La Palma, Spain and Paranal, Chile• Will increase TeV point source sensitivity by ~10x relative tocurrent instruments

Growing Number of Known
Dwarf Galaxies

DECam

SDSS

Dark Energy Survey Year 2 Data: Drlica-Wagner+, 2015ApJ...813..109D
Dark Energy Survey Year 1 Data: Bechtol+, 2015ApJ...807...50B
Koposov+,
2015ApJ...805..130K• Deep photometric surveys in optical astronomy have led to thediscovery of numerous new Milky Way-satellites–Spectroscopic follow up necessary to determine if they are DM-dominateddwarf galaxies. Many new dwarf galaxies have already been
spectroscopically confirmed• LSST & other surveys will continue to find new dwarf galaxies–Wide field of view survey instruments (e.g. Fermi LAT, HAWC) will havealready observed these new DM targets

Expected Future Sensitivity

Charles+ [LAT Clb] PR 636 (2016)
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Summary• Evidence for DM exists on all cosmic scales–all observational evidence for dark matter comes from space; we must
continue investigating dark matter in its cosmic setting• Dark matter annihilations (decay) are predicted to produce a
cascade of secondary standard model particles–We can search for these cosmic messengers with a network of groundbased and space-based observatories• Some intriguing anomalies exist that require extensive follow up
work from all experiments to complete the picture–The fundamental particle properties of DM (e.g. mass) must be the samefrom all messengers and targets• The future is bright and full of exciting questions!
–We need to continue our multimessenger indirect detection quest tocomplement terrestrial experiments and gain a complete picture of theDM puzzle

Andrea Albert (LANL)

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EXTRA SLIDESGamma rays from DM Annihilation

Andrea Albert (SLAC)

rsun36= 8.5 kpc

Gamma rays from DM Annihilation

Charles+ [LAT Collab]
PR 636 (2016)

Andrea Albert (SLAC)

rsun37= 8.5 kpc

Expected Gamma rays from Dark Matter
Galactic Center● Large statistics● Complex astrophysicalfore/backgrounds

DM clumps in Halo
● Few backgrounds● Unknown location

Extragalactic● All galaxies● Isotropic

Galactic latitude(looking above
Galactic plane)

Galactic Halo
● Large statistics● Complex astrophysicalfore/backgrounds

Galactic longitude(looking away from
Galactic center)

Galaxies Clusters● e.g. Virgo● DM enriched● likely astrophysicalfore/backgrounds
Aquarius (A1) simulation

Spectral Lines● Smoking gun● Small signal

Satellite Galaxies● dSph DM enriched● Known location● Smoking gun
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Characterization of the GeV Excess•

Preliminary results from new Fermi GC analysis
have been shown– A. Albert, D. Malyshev, A. Franckowiak,
L. Tibaldo, E. Charles, et al•

Fractional residual, 1.1 – 6.5 GeV

Goal: study the effects of varying diffuse
emission modeling on the GeV excess– see backup slides for modeling details•

Results: Excess persists, large spectral
uncertainties at low and high energies

Spectra arenormalized to
4π sr

Fractional residual, 1.1 -- 6.5 GeV
no excess template included in fit

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