CTA as a γ-ray probe for dark matter structures: Searching for the smallest clumps & the largest clusters

Transcription

1 CTA as a γ-ray probe for dark matter structures: Searching for the smallest clumps & the largest clusters Moritz Hütten (MPP Munich) for the CTA consortium "The extreme Universe viewed in very-highenergy gamma rays 2018, La Palma, Introduction 2. Dark Galactic DM clumps 3. Galaxy clusters mhuetten@mpp.mpg.de

2 1. Introduction 2

3 Gravitational evidence for dark matter on all scales Reticulum II, Dwarf galaxies small scales (pc) baryonic matter Baryonic matter dark matter Dark Matter large scales (Mpc) 3

4 Gravitational evidence for dark matter on all scales Reticulum II, Dwarf galaxies Begemann (1991) small scales (pc) baryonic matter Baryonic matter Milky Way-like galaxies dark matter Dark Matter large scales (Mpc) 3

5 Gravitational evidence for dark matter on all scales Reticulum II, Dwarf galaxies Begemann (1991) small scales (pc) baryonic matter Baryonic matter Milky Way-like galaxies dark matter Dark Matter large scales (Mpc) Galaxy cluster substructure 3

6 Gravitational evidence for dark matter on all scales Reticulum II, Dwarf galaxies Begemann (1991) small scales (pc) baryonic matter Baryonic matter Galaxy clusters dark matter Milky Way-like galaxies Dark Matter large scales (Mpc) Chandra/HST image of Abell 1689 Galaxy cluster substructure 3

7 The dark matter γ-ray connection: indirect detection NASA/G. Dinderman (mass > GeV) 4

8 The dark matter γ-ray connection: indirect detection NASA/G. Dinderman (mass > GeV) 4

9 The dark matter γ-ray connection: indirect detection NASA/G. Dinderman typical astrophysical background γ-rays: (mass > GeV) m = 500 GeV + straight to observer + no absorption in the Galaxy - astrophysical background 4

10 Dark matter structures on all scales 140 Mpc x 100 Mpc 500 Mpc x 375 Mpc 0.8 Mpc x 0.6 Mpc DM d (sim ensity ulat ion) 0.4 Mpc x 0.3 Mpc Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 5

11 Dark matter structures on all scales 140 Mpc x 100 Mpc 500 Mpc x 375 Mpc DM d (sim ensity ulat ion) 0.8 Mpc x 0.6 Mpc Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 5

12 Dark matter structures on all scales 140 Mpc x 100 Mpc 500 Mpc x 375 Mpc DM d (sim ensity ulat ion) 0.8 Mpc x 0.6 Mpc Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 5

13 Dark matter structures on all scales 140 Mpc x 100 Mpc 500 Mpc x 375 Mpc DM d (sim ensity ulat ion) Satellite galaxies 0.8 Mpc x 0.6 Mpc Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 5

14 Dark matter structures on all scales 140 Mpc x 100 Mpc 500 Mpc x 375 Mpc DM d (sim ensity ulat ion) Satellite galaxies Segue I 0.8 Mpc x 0.6 Mpc LMC C Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 5

15 Dark matter structures on all scales 140 Mpc x 100 Mpc 500 Mpc x 375 Mpc Satellite galaxies Segue I Dark 0.8 Mpc x 0.6 Mpc clumps: too light to trigger star formation DM d (sim ensity ulat ion) LMC C Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 5

16 Dark matter structures on all scales 140 Mpc x 100 Mpc 500 Mpc x 375 Mpc 0.8 Mpc x 0.6 Mpc DM d (sim ensity ulat ion) 0.4 Mpc x 0.3 Mpc Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 6

17 Dark matter structures on all scales 500 Mpc x 375 Mpc 0.8 Mpc x 0.6 Mpc DM d (sim ensity ulat ion) 0.4 Mpc x 0.3 Mpc Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 6

18 Dark matter structures on all scales 500 Mpc x 375 Mpc DM d (sim ensity ulat ion) Assuming this was Perseus cluster (d = 80 Mpc) 0.8 Mpc x 0.6 Mpc 0.4 Mpc x 0.3 Mpc Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 6

19 Dark matter structures on all scales 500 Mpc x 375 Mpc DM d (sim ensity ulat ion) Assuming this was Perseus cluster (d = 80 Mpc) CTA field of view 0.8 Mpc x 0.6 Mpc (6 diameter) 0.4 Mpc x 0.3 Mpc Central 1 Mpc of the Perseus cluster (0.7 x 0.7 ) Springel et al. (2005) Diemand, Kuhlen, Madau (2006) color code: brighter = denser 6

20 The dark matter sky seen from Earth (annihilation) log (γ-ray intensity from DM annihilation), Galactic coordinates synthetic map calculated with CLUMPY

21 The dark matter sky seen from Earth (annihilation) Galactic center + strong signal γ-ray backgrounds (Silk and Bloemen, 1987, ) log (γ-ray intensity from DM annihilation), Galactic coordinates synthetic map calculated with CLUMPY

22 The dark matter sky seen from Earth (annihilation) Galactic center Milky Way satellite galaxies + no background lower fluxes , , + strong signal γ-ray backgrounds (Silk and Bloemen, 1987, ) log (γ-ray intensity from DM annihilation), Galactic coordinates synthetic map calculated with CLUMPY

23 The dark matter sky seen from Earth (annihilation) Dark clumps + no background? brighter than satellites unknown position Galactic center Milky Way satellite galaxies + no background lower fluxes , , + strong signal γ-ray backgrounds (Silk and Bloemen, 1987, ) log (γ-ray intensity from DM annihilation), Galactic coordinates synthetic map calculated with CLUMPY

24 The dark matter sky seen from Earth (annihilation) Galaxy clusters + massive DM targets far away γ-ray backgrounds Dark clumps + no background? brighter than satellites unknown position Galactic center Milky Way satellite galaxies + no background lower fluxes , , + strong signal γ-ray backgrounds (Silk and Bloemen, 1987, ) log (γ-ray intensity from DM annihilation), Galactic coordinates synthetic map calculated with CLUMPY

25 The dark matter sky seen from Earth (annihilation) Galaxy clusters + massive DM targets far away γ-ray backgrounds Dark clumps + no background? brighter than satellites unknown position Galactic center Milky Way satellite galaxies + no background lower fluxes , , + strong signal γ-ray backgrounds (Silk and Bloemen, 1987, ) log (γ-ray intensity from DM annihilation), Galactic coordinates synthetic map calculated with CLUMPY

26 Dark matter clumpiness matters! Annihilation Decay 8

27 Dark matter clumpiness matters! Flux searched for with γ-ray telescope Annihilation Decay 8

28 Dark matter clumpiness matters! Annihilation Secondary γ-rays after annihilation/decay Decay 8

29 Dark matter clumpiness matters! Annihilation Decay Unknown DM particle mass: parameter 8

30 Dark matter clumpiness matters! Annihilation Annihilation cross section Decay Particle lifetime 8

31 Dark matter clumpiness matters! Annihilation Decay Density distribution 8

32 Dark matter clumpiness matters! Annihilation Decay Density distribution What density targets do we need for CTA? 1. Bright: close and/or massive DM budget 2. Localized ( point-like ) 3. no astrophysical back-/foregrounds 8

33 2. Dark Galactic DM clumps 9

34 Dark clumps annihilation brightness Brightness in γ-rays (J-factor): conservative 10 4 counting all objects flux from annihilation ~ Hütten, Combet, Maier, Maurin (2016) 10 3 optimistic N X( J) Estimated J-factors of known satellite galaxies counting all objects many faint objects J-factor [GeV 2 cm 5 ] few bright objects 10

35 Dark clumps annihilation brightness Brightness in γ-rays (J-factor): conservative 10 4 counting all objects flux from annihilation ~ Close-by dark clumps bright DM targets Hütten, Combet, Maier, Maurin (2016) 10 3 optimistic N X( J) Estimated J-factors of known satellite galaxies counting all objects many faint objects J-factor [GeV 2 cm 5 ] few bright objects 10

36 Dark clumps annihilation profiles half-light radius ~ 0.14 log Intensity conservative l [deg] clumpy code, b [deg] Take advantage of CTA s excellent angular resolution 11

37 Dark clumps annihilation profiles half-light radius ~ 0.14 Point-like emission from dark clumps log Intensity conservative l [deg] clumpy code, b [deg] Take advantage of CTA s excellent angular resolution 11

38 But how to find the dark clumps? In a survey: Observing 25% of the sky with 500 hours (extragalactic survey benchmark): 25% of sky γ-ray brightest subhalo in the field (assume it is a dark clump)

39 But how to find the dark clumps? In a survey: Observing 25% of the sky with 500 hours (extragalactic survey benchmark): Chance detection 22 approximate CTA 236 diameter FOV 24 12

40 Survey sensitivity based on CTA South (prod2-3) 500h, 95% C.L. (Hütten, Combet, Maier, Maurin, 2016) CTA dark subhalos, model HIGH CTA dark subhalos,! b b Di erent targets,! b b h vi [cm 3 s 1 ] %! b b 68% LOW (post-trial) HIGH LOW (post-trial) HIGH (pre-trial) (post-trial) Cosmic variance VERITAS, stacked dsph MAGIC, Segue 1 (158h) H.E.S.S., Gal. halo (254h) Fermi-LAT, stacked dsph CTA dark subhalos (HIGH) thermal relic cross section WIMP mass m [GeV] WIMP mass m [GeV] WIMP mass m [GeV] 13

41 Survey sensitivity based on CTA South (prod2-3) 500h, 95% C.L. (Hütten, Combet, Maier, Maurin, 2016) CTA dark subhalos, model HIGH CTA dark subhalos,! b b Di erent targets,! b b h vi [cm 3 s 1 ] ! b b! b b [cm 2 s 1 sr 1 GeV 1 ] conservative model LOW (post-trial) optimistic HIGH (post-trial) model [cm 2 s 1 sr 1 GeV 1 ] VERITAS, stacked dsph MAGIC, Segue 1 (158h) H.E.S.S., Gal. halo (254h) Fermi-LAT, stacked dsph CTA dark subhalos (HIGH) [cm 2 s 1 sr 1 GeV 1 ] Modeling systematics thermal relic cross section WIMP mass m [GeV] WIMP mass m [GeV] [cm 2 s 1 sr 1 GeV 1 ] WIMP mass m [GeV]

42 Survey sensitivity based on CTA South (prod2-3) 500h, 95% C.L. (Hütten, Combet, Maier, Maurin, 2016) CTA dark subhalos, model HIGH CTA dark subhalos,! b b Di erent targets,! b b h vi [cm 3 s 1 ] ! b b! b b + conservative model LOW (post-trial) optimistic HIGH (post-trial) model VERITAS, stacked dsph MAGIC, Segue 1 (158h) H.E.S.S., Gal. halo (254h) Fermi-LAT, stacked dsph CTA dark subhalos (HIGH) thermal relic cross section WIMP mass m [GeV] WIMP mass m [GeV] WIMP mass m [GeV] 15

43 Survey sensitivity based on CTA South (prod2-3) 500h, 95% C.L. (Hütten, Combet, Maier, Maurin, 2016) h vi [cm 3 s 1 ] CTA dark subhalos, model HIGH! b b! b b + CTA dark subhalos, LOW (post-trial) conservative model LOW HIGH (post-trial) optimistic HIGH (post-trial) (pre-trial) model! b b Di erent targets,! b b CTA Segue 1 (500h) CTA Gal. halo (500h, Einasto) VERITAS, stacked dsph MAGIC, Segue 1 (158h) H.E.S.S., Gal. halo (254h) Fermi-LAT, stacked dsph CTA dark subhalos (HIGH) thermal relic cross section WIMP mass m [GeV] WIMP mass m [GeV] WIMP mass m [GeV] 16

44 Chance detection probability: Subhalo algebra 1. Number of detectable objects rises linearly with ΔΩ : geometry + isotropy 2. Number of detectable objects rises with sqrt(t obs ): instrument background 3. Number of detectable objects rises inversely with sensitivity threshold N objects ( F sens ) ~ 1/F sens : subhalo source count distribution See Hütten et al. (2016), App. E, for details ΔΩ N FOV T obs /FOV <σv> N spots ( 2σ) π min cm 3 s min cm 3 s min cm 3 s min cm 3 s

45 3. Galaxy clusters 18

46 The case of galaxy clusters: DM annihilation Recall: All Galactic clumps N X( J) dwarf galaxies J-factor [GeV 2 cm 5 ] 19

47 The case of galaxy clusters: DM annihilation Recall: All Galactic clumps N X( J) dwarf galaxies J-factor [GeV 2 cm 5 ] DM-annihilation brightness comparable to satellite galaxies 19

48 The case of galaxy clusters: DM annihilation DM-annihilation brightness comparable to satellite galaxies Emission profiles more extended (typical half-light radii > 0.5 ) 19

49 The case of galaxy clusters: DM annihilation DM-annihilation brightness comparable to satellite galaxies Emission profiles more extended (typical half-light radii > 0.5 ) Astrophysical backgrounds: γ-ray emitting galaxies (AGN, star-forming galaxies, CR interaction) Also expect diffuse emission from the inter-cluster medium (ICM) 19

50 DM annihilation profile of the Perseus cluster 3 orders of magnitude 0.5 Intensity proportional to without substructure random triaxiality 20

51 DM annihilation profile of the Perseus cluster 3 orders of magnitude 0.5 NCG 1275 MAGIC, E > 250 GeV IC 310 Intensity proportional to without substructure random triaxiality 20

52 DM decay profile of the Perseus cluster 3 orders of magnitude 0.5 NCG 1275 MAGIC, E > 250 GeV See MAGIC result : τ DM s IC 310 Intensity proportional to random triaxiality (substructure irrelevant) 21

53 Cosmic-ray induced emission in the inter-cluster medium Spatial profile Spectral profile Expectation Expectation CTA s excellent angular resolution and energy range: disentangle the signals DM substructure extends annihilation profile 22

54 The CTA galaxy cluster working group (wg-phys-clusters) CTA galaxy cluster key science project: 300 hours allocated for CTA North Coordination: Moritz Hütten (MPP Munich) Judit Pérez-Romero, Miguel Sánchez-Conde (UAM Madrid) The team: R. Alfaro, G. Brunetti, S. Colafrancesco, C. Delgado, M. Doro, E. Fedorova, E. de Gouveia Dal Pino, S. Hernandez Cadena, M. Hütten, M. Lallena, S. Nuza, J. Pérez, O. Reimer, M. Sánchez-Conde, S. Zimmer Updated performance study on galaxy clusters in progress 23

55 Conclusions Hierarchical DM clustering: γ-ray clumps from annihilation/decay at various scales and distances Search for the smallest clumps in a TeV γ-ray survey with CTA (extragalactic key science project by-catch) Watch out for unidentified sources in the FOV: may be a Galactic DM clump Study the closest galaxy clusters: Perseus and Coma: Excellent observation conditions with CTA North Clusters: Constrain DM particle life times beyond τ DM > s = t Universe CTA excellent probe for TeV dark matter particle physics in various complementary targets 24

56 BACK UP 25

57 Perseus cluster also optimal target for DM decay Perseus = Perseus region already extensively studied by MAGIC telescopes: , , , , , : τ DM s 26

58 Astrophysical merits of Perseus cluster observations

59 Brightest Galactic DM clumps: Properties Average mass and distance (from 10 4 runs): Fermi-LAT scenario CTA scenario Median properties of (f sky = 82.6%) (f sky = 25%) brightest subhalo within int =0.1 int =0.8 int =0.05 int =0.1  ÂD ı obs [kpc]  1 2  log 10 ( Âm ı vir /M ) log  10 J ı /GeV 2 cm optimistic Fermi-LAT scenario CTA scenario Median properties of (f sky = 82.6%) (f sky = 25%) brightest subhalo within int =0.1 int =0.8 int =0.05 int =0.1 ÂD ı obs [kpc] log 10 ( Âm ı vir /M ) log  10 J ı /GeV 2 cm conservative 28

60 Dark clumps decay brightness Number of subhalos brighter than a given flux/ J-factor: # of subhalos brighter than J Nsub( D) flux > 100 GeV in Crab units for! b b, =10 26 s, m = 500 GeV % of the sky, dwarf-like objects included Sculptor dsphg Astrophysical D-factor in log 10 (D/GeV cm 2 ) CTA survey sensitivity model 1 model 2 model 3 model 4 model 5 model 6 model 4 parameters 7 model 168 models model dashed 9 lines: model higher 10 c(m) model 11 model 12 model 13 model 14 model 15 model 16 work done by Rungployphan Kieokaew, 2015!29