The Galactic Center GeV Excess: Have We Started to See Dark Matter? - PowerPoint PPT Presentation

The Galactic Center GeV Excess: Have We Started to See Dark Matter? Sam McDermott Based on: various observational works (Daylan et al 1402.6703, Calore et al 1409.0042, …) SDM, I. Cholis, P. Fox, S. K. Lee (preliminary / in progress) GGI, 9/30/15

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Outline 1. Observational facts (“introduction”) - how many photons? from where? - what is it? 2. A new observational idea 3

Basics • Two kinds of analyses - Galactic center — below the Bubbles - Inner Galaxy — excludes disk, goes out > O(10˚) • “Excess” found both near and far from SgrA* • Appears to be spherical and smooth; radial fall-off compatible with (gNFW profile) 2 : ρ gNFW (x)~ ρ 0 /[x γ (1+x) 3- γ ] 4

Galactic Center excess with normalization ~ 30% of raw! point sources; isotropic; diffuse emission; map of 20 cm synchrotron ∫ los (gNFW profile) 2 fits excess well 1402.6703 5

Galactic Center excess with normalization ~ 30% of raw! point sources; isotropic; diffuse emission; map of 20 cm synchrotron ∫ los (gNFW profile) 2 “ π 0 ’s” = hadronic CRs interacting with dust fits excess well “bremsstrahlung” = leptonic CRs interacting with dust “ICS” = leptonic CRs interacting with background light 1402.6703 6

Galactic Center excess with normalization ~ 30% of raw! point sources; isotropic; diffuse emission; map of 20 cm synchrotron ∫ los (gNFW profile) 2 “ π 0 ’s” = hadronic CRs interacting with dust fits excess well cosmic rays interacting with “bremsstrahlung” = leptonic CRs interacting with dust previously mapped stuff “ICS” = leptonic CRs interacting with background light 1402.6703 7

Inner galaxy 90 0 0 -1 -1 45 diffuse map -2 -2 0 0 -3 -3 -45 -4 -4 -90 -5 -5 90 0 0 180 90 0 0 -90 -180 -1 -1 45 Fermi bubbles -2 -2 0 0 -3 -3 -45 -4 -4 -90 -5 -5 90 0 0 180 90 0 0 -90 -180 -1 -1 45 NFW -2 -2 0 0 -3 -3 -45 -4 -4 1402.6703 -90 -5 -5

Inner galaxy 0.5-1 GeV residual 1-3 GeV residual 20 20 20 20 12 12 15 15 10 10 10 -6 counts/cm 2 /s/sr 10 -6 counts/cm 2 /s/sr 10 10 8 8 10 10 6 6 0 0 0 0 4 4 5 5 2 2 -10 -10 0 0 0 0 -20 -20 -2 -2 20 10 0 0 -10 -20 20 10 0 0 -10 -20 3-10 GeV residual 10-50 GeV residual 20 20 1.5 1.5 4 4 10 -6 counts/cm 2 /s/sr 10 -6 counts/cm 2 /s/sr 10 10 3 3 1.0 1.0 0 0 2 2 0 0 0.5 0.5 1 1 -10 -10 0 0 0.0 0.0 -20 -20 20 10 0 0 -10 -20 20 10 0 0 -10 -20 1402.6703 9

Total Normalization × 10 6 1 . 2 − 2 . 0 ◦ < ℓ < 2 . 0 ◦ GCE 2.12-3.32 GeV PSCs 1 . 0 π 0 +Bremss ICS Count density [sr − 1 ] Isotropic 0 . 8 Bubbles at energies of interest, Sum 0 . 6 much brighter than Bubbles (~ O(30%) of total!) 0 . 4 0 . 2 0 . 0 − 20 − 15 − 10 − 5 0 5 10 15 20 b [deg] 1409.0042 10

Seen out to > 10˚ γ =1.3 1402.6703 11

Highly spherical… 1402.6703 12

… robust to diffuse map × 10 − 5 × 10 − 5 1 . 2 I II 1 . 0 0 . 8 0 . 6 0 . 4 0 . 2 Presence of a signal with 0 . 0 − 0 . 2 × 10 − 6 × 10 − 6 4 dE [GeV / (cm 2 s sr)] energy peak ~ 2 GeV is III IV 3 2 1 robust to changes in E 2 dN 0 − 1 × 10 − 6 × 10 − 6 diffuse template V VI 1 . 5 1 . 0 0 . 5 0 . 0 − 0 . 5 × 10 − 6 × 10 − 6 3 . 0 dE [GeV / (cm 2 s sr)] 2 . 5 VII VIII 1409.0042 2 . 0 1 . 5 1 . 0 0 . 5 20 0 . 0 E 2 dN X 15 XI − 0 . 5 V − 1 . 0 10 1 . 5 × 10 − 6 × 10 − 6 III 5 VII VIII I IX X b [deg] 1 . 0 0 0 . 5 II − 5 IV 0 . 0 − 10 VI − 0 . 5 − 15 − 1 . 0 − 20 10 0 10 1 10 2 10 0 10 1 10 2 20 15 10 5 0 − 5 − 10 − 15 − 20 E [GeV] E [GeV] ℓ [deg] 13

The existence of an excess is pretty well agreed upon (independent methods by independent groups* agree something is there) *also see work by: Abazajian and collaborators (1207.6047, 1402.4090, Qualitative thing we 1410.6168); Gordon, Macias, and collaborators are not yet sure of: (1306.5725, 1312.6671, 1410.1678, 1410.7840); Murgia’s Fermi symposium slides Is the excess from astrophysics or dark matter? 14

Qualitative thing we are not yet sure of: Is the excess from astrophysics or dark matter? If DM, we need to confront other issues: are there other indirect detection signals? bounds? • what are its interactions with the SM? • what is the UV theory? • 15

“Secondaries” basic statements: no positron “bump” found, understanding of anti-baryons is murky 1410.1527 Bergstr¨ om et al. (2013) 10 − 23 dashed: Fermi LAT WMAP7 solid: AMS-02 (this work) 10 − 24 10 − 25 ⟨ σ v ⟩ [cm 3 s − 1 ] 10 − 26 τ + τ − 10 − 27 µ + µ − e + e − γ 10 − 28 e + e − 10 − 29 10 1 10 2 m χ [GeV] 1306.3983 16

Cosmic Ray Constraints 10 - 24 10 - 24 Thin propagation models Benchmark propagation models 10 - 25 10 - 25 different colors: X s v \ @ cm 3 s - 1 D X s v \ @ cm 3 s - 1 D 10 - 26 10 - 26 different choices THN THN CON THN2 KOL THN3 KRA 10 - 27 10 - 27 of diffusion zone THK 20 40 60 80 100 20 40 60 80 100 M DM @ GeV D M DM @ GeV D parameters 10 - 24 10 - 24 Thin propagation models Benchmark propagation models 10 - 25 10 - 25 X s v \ @ cm 3 s - 1 D X s v \ @ cm 3 s - 1 D 10 - 26 10 - 26 different rows: THN THN CON THN2 KRA THN3 KOL 10 - 27 10 - 27 THK different choices 20 40 60 80 100 20 40 60 80 100 M DM @ GeV D M DM @ GeV D 10 - 24 10 - 24 Thin propagation models Benchmark propagation models of relation b/w 10 - 25 10 - 25 X s v \ @ cm 3 s - 1 D X s v \ @ cm 3 s - 1 D φ Fp and φ Fp local 10 - 26 10 - 26 and Galactic THN THN CON THN2 KRA THN3 KOL 10 - 27 10 - 27 THK 1407.2173 17 20 40 60 80 100 20 40 60 80 100 M DM @ GeV D M DM @ GeV D

Dwarf Galaxies 3 σ 10 − 5 1 Ret2 E 2 dF/dE [GeV cm − 2 s − 1 sr − 1 ] 10 6 2 σ Seg1 13390 51 33 22 18 11 1 1 σ Significance 10 − 6 0 σ − 1 σ − 2 σ τ + τ − 10 − 7 − 3 σ 10 1 10 2 10 3 10 0 10 1 10 2 Mass [GeV] Energy [GeV] Geringer-Sameth et al, 1503.02320 18

Dwarf Galaxies 3 σ 10 − 5 1 Ret2 E 2 dF/dE [GeV cm − 2 s − 1 sr − 1 ] 10 6 2 σ Seg1 13390 51 33 22 18 11 1 1 σ Significance 10 − 6 0 σ − 1 σ − 2 σ τ + τ − 10 − 7 − 3 σ Mass [GeV] 10 1 10 2 10 3 10 0 10 1 10 2 10 1 10 2 10 3 Mass [GeV] − 3 σ Energy [GeV] τ + τ − Geringer-Sameth − 2 σ et al, 1503.02320 − 1 σ Significance 0 σ 1 σ Seg1 2 σ Ret2 19 3 σ

Dwarf Galaxies 10 − 21 DES J0222.7-5217 DES J2108.8-5109 DES J0255.4-5406 DES J2339.9-5424 10 − 22 DES J0335.6-5403 DES J2251.2-5836 DES J0344.3-4331 Combined DES Candidate dSphs DES J0443.8-5017 Combined Known dSphs 10 − 23 h σ v i (cm 3 s � 1 ) 10 − 24 10 − 25 Thermal Relic Cross Section 10 − 26 (Steigman et al. 2012) b ¯ b 10 − 27 10 1 10 2 10 3 10 4 DM Mass (GeV/c 2 ) Drlica-Wagner et al, 1503.02632 20

Dwarf Galaxies 10 − 22 Pass 8 Combined dSphs Fermi-LAT MW Halo 10 − 23 H.E.S.S. GC Halo MAGIC Segue 1 Abazajian et al. 2014 (1 σ ) h σ v i (cm 3 s � 1 ) 10 − 24 Gordon & Macias 2013 (2 σ ) Daylan et al. 2014 (2 σ ) Calore et al. 2014 (2 σ ) 10 − 25 Thermal Relic Cross Section 10 − 26 (Steigman et al. 2012) b ¯ b 10 − 27 10 1 10 2 10 3 10 4 DM Mass (GeV/c 2 ) B. Anderson et al, 1503.02632 21

How Bright? DM DM → b b 10 - 21 Isothermal solid: data dashed: average MC limit NFW 10 - 22 shading: population st. dev. Einasto of the 10 MC limits NFW c 10 - 23 〈σ v 〉 [ cm 3 s - 1 ] 10 - 24 10 - 25 thermal WIMP 10 - 26 10 - 27 10 1 10 2 10 3 10 4 1 m DM [ GeV ] Essig, Massari, et al 1503.07169 22

Qualitative thing we are not yet sure of: Is the excess from astrophysics or dark matter? If SM, we need a consistent explanation: existence of the Fermi bubbles is suggestive; but hard • to get smooth structure from this kind of burst millisecond pulsars show up over the correct scales • range with plausibly correct morphology; but… 23

Point Sources 1412.6099 n~r - δ δ ~2.5 observed in Andromeda (cf. ρ 2 ~r -2 γ ) 24

Point Source Fits 0 3 5 0 18 9 2 2 0 based on non-Poissonian template fit, 1506.05124 point sources can account for excess 25

Millisecond Pulsars • Spectra are “significantly” different • Should have resolved many more MSPs in inner 1.8 kpc (~few˚) given “reasonable” luminosity function: N(L>10 34 erg/s) ~ 200, 1407.5625 N(L>10 35 erg/s) ~ 60 26

Globular Clusters • globular clusters are dense stellar environments (=> star- star encounters are common) • Some star-star encounters create X-ray binaries, some create MSPs • X-ray binaries fizzle out sooner than MSPs 27

1507.05616 DISRUPTED GLOBULAR CLUSTERS CAN EXPLAIN THE GALACTIC CENTER GAMMA RAY EXCESS Timothy D. Brandt 1,3 and Bence Kocsis 1,2 (with zero free parameters) 28

1507.05616 DISRUPTED GLOBULAR CLUSTERS CAN EXPLAIN THE GALACTIC CENTER GAMMA RAY EXCESS Timothy D. Brandt 1,3 and Bence Kocsis 1,2 (with zero free parameters) some concerns, still 29

Point Sources, II 0 3 5 0 18 9 2 2 0 1506.05124 still some missing point sources? 30