The$3.5$keV$Line$in$the$Galac2c$Center$(and$a$way$to$test$the$GC$gamma=ray$excess)$

Tesla$Jeltema$Santa%Cruz%Ins,tute%for%Par,cle%Physics%University%of%California,%Santa%Cruz%

IAU$Symposium$322,$$July$2016$

Radio Observations of Clusters

  Synchrotron emission from e+ e- produced in DM annihilation/decay in cluster B-fields.

  Some clusters have detected diffuse radio emission, but many do not or only host weak emission

Colafrancesco et al. 2006

Storm et al. 2106, arXiv:1607.01049

Future Radio Observations

  Near-term LOFAR surveys can test a dark matter origin of the GC gamma-ray excess

Predicted limits for a massive cluster LOFAR Tier 1 LOFAR Tier 2

P8 Fermi dwarfs

* limits are not very B field or redshift dependent

X-ray Lines from Dark Matter

  Sterile neutrino: •  keV scale sterile neutrinos viable �warm� DM candidate •  would decay through mixing with active neutrinos producing photons at half the particle mass

  Other possibilities: axion-like particle conversions, eXciting Dark Matter (XDM), many more …

Detected, with mild significance (~4σ) with XMM and Chandra observations of Perseus, M31, stacked clusters

(Balbul et al. 2014, Boyarsky et al. 2014)

These papers argue that the line is not explained by astrophysical lines, and may stem from DM decay

The 3.5 keV Line

Bulbul%et%al.%2014%

Several atomic lines nearby, especially K XVIII (i.e. K ion with 18-1 electrons missing, i.e. “He-like”)

Determination of line intensity non-trivial: (1) solar abundances? (2) plasma temperature?

instrumental energy resolution

Bulbul%et%al.%2014%

The 3.5 keV Line in the GC

spectral analysis of the Galactic Center (and reanalysis of M31)

  morphology of 3.5 keV emission in the GC (and Perseus)

New analysis of XMM Galactic Center data

=> There is a line at 3.5 keV

Line is compatible with an atomic emission line from K XVIII; Line is also compatible with DM interpretation

Galactic Center Spectrum

Jeltema & Profumo 2015

Re-analysis of XMM M31 data

=> No significant line found

The 3.5 keV Line in M31

Jeltema & Profumo 2015

Are there plausible astrophysical origins?

 Potassium which is slightly overabundant compared to solar ratios (Jeltema & Profumo 2015)

-- In fact, solar flare spectra show potassium ~10x more abundant than solar photospheric (Phillips et al. 2015)

 Charge-exchange sulfur lines (Gu et al. 2015)

Galactic Center Morphology

Carlson, Jeltema and Profumo 2015

  The 3.5 keV emission is asymmetric with a distribution similar to nearby plasma lines

3.5 keV Line Morphology

Einasto$

NFW$Burkert$

  The 3.5 keV morphology in GC (asymmetric) and Perseus (cool-core) follows astrophysical plasma not DM

  Limits inconsistent with DM decay origin of Bulbul line

Carlson, Jeltema and Profumo 2015

Deep%Observa,ons%of%Draco%

  Non-detection inconsistent with flux observed from clusters and GC for DM decay origin

  Dark matter decay excluded at > 99%

Jeltema & Profumo 2016

  A simple DM decay picture is inconsistent with non-detection in Draco and Galactic Center morphology

Summary%

  There are plausible astrophysical explanations

Exclusion limits from Draco Jeltema & Profumo 2016

Thank you!