Constraining Galactic dark matter in the Fermi-LAT sky with photon counts statistics Moriond Cosmology 2018 Silvia Manconi (University of Turin & INFN) March 20, 2018 In collaboration with: Hannes Zechlin, Fiorenza Donato (University of Turin)
Outline 1 Indirect DM detection with γ-rays 2 Photon counts statistics of Fermi-LAT data 3 Results for Galactic Dark Matter 4 Summary manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 2
Indirect dark matter (DM) detection with γ-rays Energy distribution into final state particles, b b annihilation channel: Inner (outer): DM mass 200 GeV (5TeV) [Cirelli+2010] Prompt γ-rays emission: Production, decay of π 0 Hadronization Internal bremsstrahlung Monocromatic lines S.Camera talk this morning Focus on Weakly Interacting Massive Particles, benchmark other candidates: axions, ALPs,.. manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 3
Indirect DM detection with γ-rays Photon counts statistics of Fermi-LAT data Results for Galactic Dark Matter Summary The γ-ray sky seen from Fermi-LAT [Fermi-LAT 5 years, energy > 1 GeV] Fermi-Large Area Telescope: high-energy gamma-ray telescope, data from E = 20 MeV to more than 300 GeV, 10 years of operation manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 4
Indirect DM detection with γ-rays Photon counts statistics of Fermi-LAT data Results for Galactic Dark Matter Summary The γ-ray sky seen from Fermi-LAT [Fermi-LAT 5 years, energy > 1 GeV] + isotropic emission from unresolved sources and truly diffuse processes manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 5
Indirect DM detection with γ-rays Photon counts statistics of Fermi-LAT data Results for Galactic Dark Matter Summary The γ-ray sky seen from Fermi-LAT [Fermi-LAT 5 years, energy > 1 GeV] + isotropic emission from unresolved sources and truly diffuse processes... DM? manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 6
Targets for dark matter searches Constraints from different targets, see [Charles+PhysRep2016] [Conrad+Nature2017] This talk: Galactic DM halo, high latitudes manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 7
Decomposing the γ-ray sky γ-ray sky = Galactic diffuse + Extragalactic γ-ray Background (EGB) emissions. EGB= detected sources + unresolved faint sources (individual, truly diffuse) limits: detection threshold, backgrounds Unresolved sources measured using statistical properties of observed counts [Zechlin+ApjS2016, 1-10 GeV] Source count distribution dn/ds Red points: catalog Gray points: detection efficiency < 1 Bands: statistical analysis results (1pPDF): 1 order of magn. improvement in flux S from 15% (3FGL) to 25% (1pPDF) of total γ ray flux explained with point sources flux decomposition EGB composition constrains: origin of IceCUBE neutrinos [Ahlers+ApJ2017] ultra-high energy cosmic rays [Taylor+PRD15] room for DM contributions [DiMauro+PRD15, Ackermann+ApJ15] *catalogs: AGN, magn, star-forming galaxies,... manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 8
Decomposing the γ-ray sky γ-ray sky = Galactic diffuse + Extragalactic γ-ray Background (EGB) emissions. EGB= detected sources + unresolved faint sources (individual, truly diffuse) limits: detection threshold, backgrounds Unresolved sources measured using statistical properties of observed counts [Zechlin+ApjS2016, 1-10 GeV] Source count distribution dn/ds Red points: catalog Gray points: detection efficiency < 1 Bands: statistical analysis results (1pPDF): 1 order of magn. improvement in flux S from 15% (3FGL) to 25% (1pPDF) of total γ ray flux explained with point sources flux decomposition EGB composition constrains: origin of IceCUBE neutrinos [Ahlers+ApJ2017] ultra-high energy cosmic rays [Taylor+PRD15] room for DM contributions [DiMauro+PRD15, Ackermann+ApJ15] *catalogs: AGN, magn, star-forming galaxies,... manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 8
Pixel count statistics with the 1-point Probability Distribution Function (1pPDF) Statistical analysis of intensity to decompose the γ-ray sky courtesy of H. Zechlin Details in [Malyshev+ApJ2011], [Zechlin+ApjS2016]. Similar methods used also in radio [Vernstrom+MNRAS2015] and X-ray [Soltan+A&A2011] manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 9
The 1pPDF analysis Separate sources based on statistical properties of their photon counts Modeling: probability generating functions P (p) (t): p (p) k = probability to find k photons in pixel (p) p (p) k = 1 k! d k P (p) (t) dt k t=0 OBSERVED Probability distribution of photon counts in pixels p (p) k AIM Decompose γ-ray sky in: -Point sources dn/ds -Diffuse contributions P (p) (t) = k=0 ( ) p (p) k tk = exp x m (p) (t m 1) m=1 x (p) m = expected number of sources contributing m photons per pixel p: - point sources (dn/ds) - Galactid diffuse emission - Diffuse isotropic background - Dark matter manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 10
The 1pPDF analysis Separate sources based on statistical properties of their photon counts Modeling: probability generating functions P (p) (t): p (p) k = probability to find k photons in pixel (p) p (p) k = 1 k! d k P (p) (t) dt k t=0 OBSERVED Probability distribution of photon counts in pixels p (p) k AIM Decompose γ-ray sky in: -Point sources dn/ds -Diffuse contributions P (p) (t) = k=0 ( ) p (p) k tk = exp x m (p) (t m 1) m=1 x (p) m = expected number of sources contributing m photons per pixel p: - point sources (dn/ds) - Galactid diffuse emission - Diffuse isotropic background - Dark matter manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 10
1pPDF results: source count distribution dn/ds Successfully applied in [Zechlin+ApjS2016, ApjL2016], [DiMauro+Apj2018], [Lisanti+Apj2016] (dn/ds of high latitude sources), [Lee+PRL2015] (Galactic Center) Point sources resolved below catalog detection threshold γ-ray sky decomposed (ex. [1,2] GeV) Point sources: 0.27 +0.002 0.04 Galactic diffuse: 0.74 +0.003 0.05 Isotropic: 0.02 +0.004 0.01 manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 11
Indirect DM detection with γ-rays Photon counts statistics of Fermi-LAT data Results for Galactic Dark Matter Summary 1pPDF applied to Galactic DM searches see preprint arxiv:1710.01506, submitted to PRD Analysis objective: investigate sensitivity reach of 1-point statistics for constraining a diffuse DM component at high latitudes Data: Fermi-LAT 8yrs, 3 energy bins from 1 GeV to 10 GeV DM model: Smooth galactic DM halo Main systematics: Galactic diffuse emission high latitudes b > 30 deg testing different benchmarck templates Simulations: validate analysis framework manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 12
Galactic DM halo modeling Flux per unit energy and solid angle: dφ DM dedω = 1 σv 4π 2 r ρ 2 ( ) dnf mdm 2 de B f J (ψ). f Spatial : - Smooth DM halo: Einasto, ρ = 0.4 GeV cm 3 [Catena+JCAP2010] - Extragalactic: subdominant - possible DM suhalos absorbed by dn/ds Energy: - WIMP self-annihilations into pure b b, τ + τ final states - dn f /de from [Cirelli+JCAP2010] dn/de 10 2 10 1 10 0 10-1 0.38 2698.61 J (ψ) b b τ + τ Galactic 10-2 10-2 10-1 10 0 10 1 E [GeV] manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 13
Region Of Interest (ROI) optimization Mask galactic plane: b > 30 40 deg Mask stuctures: Fermi Bubbles, Loop I Small ROI: over-subtraction of background Simulations w/o DM to test null hyphotesis Found optimal ROI at high latitudes where: 0.0 0.5 1 counts/px 934 [2,5] GeV PRELIMINARY Real sky results consistent with simulations in all energy bins lnl 1.0 1.5 real sky 2.0 1.0 0.5 0.0 0.5 1.0 1.5 2.0 log 10 A dm Profile likelihood for A dm, rescaling parameter for σv 0 = 10 26 cm 3 s 1 for m dm = 15 GeV manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 14
Results: upper limits on σv 10-22 10-22 σv UL [cm 3 s 1 ] 10-23 10-24 10-25 10-26 10-27 10-28 PRELIMINARY τ + τ channel [1,2] GeV, 1pPDF [2,5] GeV, τ + τ 1pPDF [5,10] GeV, channel 1pPDF 10 1 10 2 10 3 m DM [GeV] σv UL [cm 3 s 1 ] 10-23 10-24 10-25 10-26 10-27 10-28 b b channel PRELIMINARY [1,2] GeV, 1pPDF [2,5] GeV, 1pPDF [5,10] GeV Dwarfs, Ackermann et al.(2015) MW halo, Ackermann et al.(2013) Isotropic, Ajello et b b al.(2015) channel 10 1 10 2 10 3 m DM [GeV] Sensitivity of 1pPDF for DM searches at high latitudes is comparable with other methods and targets manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 15
Main systematics: Galactic diffuse emission Complex modeling, e.g. possible degeneracy Inverse Compton DM halo Testing different benchmark templates: 1 Official released with Fermi-LAT data 2 models A,B,C from [Ackermann+ApJ2015] Galactic 0.04 0.4 PRELIMINARY Up to 40% relative difference between Galactic diffuse emission from mod A and mod B, integrated in the energy bin [2,5] GeV for b > 30 deg Scatter between models: factor 2 5 in σv model B higher inverse Compton >less room for DM manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 16
Indirect DM detection with γ-rays Photon counts statistics of Fermi-LAT data Results for Galactic Dark Matter Summary Galactic DM with photon counts statistics at high latitudes- Summary - The 1-point Probability Distribution Function analysis is a powerful statistical method to:? resolve faint point sources? dissect γ-ray sky components - We investigated the 1pPDF sensitivity to constrain the Galactic DM halo at high latitudes (8 yrs of Fermi-LAT data, 3 energy bins from 1 GeV to 10 GeV) 10-23 10-24 10-25 UL [cm3 s 1 ] PRELIMINARY σv - Analysis limited by systematics from Galactic emission modeling 2698.61 10-26 - 1pPDF sensitivity is demonstrated to be comparable with other Fermi-LAT searches using other targets and method Galactic 0.38 10-22 10-27 b b channel 10-28 101 [1,2] GeV, 1pPDF [2,5] GeV, 1pPDF [5,10] GeV Dwarfs, Ackermann et al.(2015) MW halo, Ackermann et al.(2013) bb al.(2015) channel Isotropic, Ajello et 102 mdm [GeV] 103 Constraining Galactic dark matter with gamma-ray pixel counts statistics H.Zechlin, S.M., F.Donato preprint arxiv:1710.01506, submitted to PRD manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 17
Backup manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 18
The 1-point Probability Distribution Function analysis Pixel-dependent likelihood: L(Θ) = N pix p=1 P(k p) Parameter estimation: profile likelihood from Bayesian posterior, MCMC sampling (MultiNest) Details in [Zechlin+ApjS2016]. manconi@to.infn.it Constraining Galactic DM with photon count statistics Moriond Cosmology 2018 19