PoS(ICRC2017)690 http://pos.sissa.it/ † ∗ [email protected] [email protected] [email protected] Speaker. For a complete author list, see http://www.hawc-observatory.org/collaboration/icrc2017.php Nearby electron/ accelerators, mostlyposed as Pulsar potential origins of Nebulaetwo the (PWNe), positron very excess extended have above sources 10 been spatially GeV.and The coincident pro- PSR HAWC B0656+14, with Observatory suggesting reveals two ultra-relativistic nearby electrons/positronsMorphological middle-aged accelerated studies pulsars: in our on Geminga backyard. theseHAWC two energies. PWNe In this provide poster, a weies constraint will on present these on the PWNe, the model and the diffusion development and derived coefficient diffusion morphological at coefficient stud- that best fits the data. ∗ † Copyright owned by the author(s) under the terms of the Creative Commons c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). 35th International Conference —10–20 ICRC2017 July, 2017 Bexco, Busan, Korea For the HAWC Collaboration Los Alamos National Laboratory E-mail: Francisco Salesa Greus The Henryk Niewiadomski Institute of NuclearE-mail: Physics, Polish Academy of Sciences Hao Zhou Rubén López-Coto Max- Institute for Nuclear Physics E-mail: Constraining the Diffusion Coefficient with HAWC TeV -Ray Observations of Two NearbyWind Pulsar Nebulae PoS(ICRC2017)690 (2.1) ]. This around 1 ◦ Hao Zhou 8 . 0 ± ◦ 8 . ) of this large nebula σ 2 . ]. It was proposed that this over- 3 is the diffusion coefficient at 10 GeV. δ ) 0 D ], but IACT observations using standard 7 ]. Weak evidence (2 10GeV 6 / e E 2 ( is 1/3 and 0 δ D ) = e E ( D ]. At 250 pc and 288 pc, Geminga (PSR J0633+1746) and PSR 5 ][ 4 ] and Alpha Magnetic Spectrometer (AMS) [ 2 summarizes the diffusion coefficients as a function of energy from different measurements. 1 However, the diffusion coefficient measured from the Boron-Carbon ratio is the average value In this contribution, we will demonstrate the method of morphological analysis on the extended Both Geminga and PSR B0656+14 are middle-aged pulsars, with relatively low magnetic field, Ultra-relativistic electrons and cool down via inverse Compton scattering (ICS) and Launched into in 2006, the PAMELA detector discovered an excess in the positron frac- encountered over very longmuch lifetime of of that hadronic time cosmic in rays the which Galactic are halo. expected to The have local spent diffusion coefficient could be different. The TeV emission around Geminga and PSR B0656+14to in estimate the order contribution to from constraint these the sources particlenear to diffusion earth. the and local flux of electrons and positrons measured 2. Diffusion Coefficient and the modulation to theby surrounding these interstellar sources medium is (ISM) low.isotropically due Therefore into to the we the ISM. consider particle In the acceleration orderfrom scenario to these that constrain two the the pulsars, accelerated electron we anddiffusion particles need coefficient. positron diffuse flux It to is that know a reach how property the fast of Earth these a medium particles and diffuse depends in on the the ISM, energy of referred the as particles, emission was reported byanalysis the techniques Tibet have air only shower providedone array upper of [ the limits. brightest sources In inof Fermi-LAT the a data, GeV surrounding the sky nebula but Geminga at there GeV pulsar is energies. is no unambiguous evidence of the existence where the typical value of the diffusion index synchrotron. TeV gamma raye.g. can cosmic be microwave produced background through . IC The scattering extended off TeV lower PWN energy with photons, a size of 2 B0656+14 are two of the nearestadvanced pulsars to age earth, make and them this proximity importantpositron combined candidates flux. with contributing their relatively to the locally measured electron and tion at energies above 10 GeV as compared to theoretical models of positron production [ Constraining the Diffusion Coefficient with HAWC 1. Introduction anomalous observation has been(Fermi-LAT) confirmed [ with high precisionabundance by of Fermi positrons Large could be Area aalternative Telescope consequence explanation of is the that the orPulsar positron decay wind of excess nebulae dark (PWNe), is known matter, due as butsources efficient to an of electron/positron nearby the accelerators, electron/positron positron were excess postulated accelerators. [ as Geminga was reported by the Milagro experiment [ The diffuse coefficient has beenFigure measured from the Boron-Carbon ratio in hadronic cosmic rays. PoS(ICRC2017)690 Hao Zhou ], and yellow 4 ], [ 10 2 0 1 ], black [ 9 1 0 1 ], green [ 8 0 0 1 3 1 - Energy [GeV] shows the significance map in the region around these 0 1 2 2 - ]. Figure 0 1 12 3 - 0 0 9 8 7 6 3 2 1 1 3 2 2 2 2 3 3 3 0 0 0 0 0 0 0 0

, there is clearly extended emission beyond the point spread function of HAWC 1 1 1 1 1 1 1 1 D [cm^2/s] D 2 Diffusion coefficients from different measurements: blue [ The TeV gamma-ray morphology is determined assuming a model where electrons and positrons The High Altitude Water Cherenkov (HAWC) Observatory, located in central Mexico at 4100 From Figure ]. 11 around both pulsars, showing evidence of electronsthe and ISM. positrons We diffuse can away from use the the sourcestudies size into of of extended the sources, the extended sources commonly tomodels. used constrain morphological However, the models with diffusion are these coefficient. disk models, and Onthe Gaussian there the physical is parameters. no direct In connectionHAWC this data. from work, the model we parameters develop to a particle diffusion model and apply it4. to Diffusion the Model diffuse isotropically away from theICS source off into low the energy ISM. photons They in produce the TeV ISM, gamma i.e. rays cosmic through microwave background (CMB), infrared, and m above sea level, is sensitivefield to of view gamma of rays 2 between steradians, 100 HAWCnebulae. has GeV a With and good 17 sensitivity 100 month to TeV. of Thanks extendedGeminga data, sources to and such two its PSR as very large B0656+14 pulsar extended [ wind sources are detected spatially coincident with measurement on the source sizelocal around diffusion these coefficient in two the nearby ISM. pulsars will provide a constraint on the 3. HAWC Observations two pulsars convolved with point spread function. Figure 1: Constraining the Diffusion Coefficient with HAWC [ PoS(ICRC2017)690 (4.3) (4.1) (4.2) is the π Hao Zhou 8 , which is / 2 B cool t is the diffusion = d B r µ and e E E at an instant t and distance r 2 t / ) e 3 e is the smaller of two timescales: ) E E 0 ( E ) t d D γε r r 4 ( p + 2 1 1 ( = er f c / d r r ) ph Γ e δ µ − ) e E ( E + 0 4 D is the energy density of target photon field with B Q GeV π takes into the account the energy loss of electrons µ ], 4 ph · 10 is the Lorentz factor of electrons, µ 13 γ / 4.3 e γ T ) = 2 E e σ c ( e c E 0 3 , m r / D , 4 t ( f = ) = e E is 1/3 and is fixed in this analysis. ( cool t δ D per photon. Equation 0 ε is the diffusion coefficient as a function of electron energy ) , the radial distribution of the electrons with energy e is the Thomson cross section, Γ The significance map convolved with point spread function in the region around Geminga and E − e ( T E σ D 0 In case of continuous injection of electrons (and positrons) from a point source at a constant Q energy density in theaverage magnetic energy field, and where where radius, up to which the electron efficiently diffuse to. They are defined as, due to both synchrotron in magnetic field and ICS off low energy photons. For the elections that from the source is given by equation 21 of [ The typical diffusion index optical photons. We hereafter obtaindiffusion an electron approximated positron formula cloud for which the we gamma-ray will emission use of to the constrain the sizerate of both HAWC sources. Figure 2: PSR B0656+14 with 17 months of HAWC data. the injection time t (in thisa function case of the election age energy of and the target pulsar) photon and energy, the electron cooling time Constraining the Diffusion Coefficient with HAWC PoS(ICRC2017)690 e E (4.4) (4.6) (4.7) (4.5) ], the ]. 20 TeV 14 Hao Zhou 18 ∼ ][ 17 is the diffusion angle. 2 2 / π / 3 3 / ) ) ◦ 2 2 c c ) e e 180 m m · / TeV ) / ) 0 e 2 2 e d 2 >/ 2 d E γ θ θ E r d 0 E 0 source ε − ε < r − . 4 ( ( 4 ( / 10 d + + r cool exp 1 log t exp 1 0. The relation between the mean electron ( ) = ( ) e d / d / 046 d E . θ r ph 0 θ ph + µ 06 06 µ . . 54 0 0 . 5 + + 0 π + + π > 8 2154 2154 8 d θ . . γ / becomes, / ( ( 1 1 2 E 2 d d , the diffusion angle is a function of electron energy B r B θ 2 < 4.5 2 / using the Multi-Mission Maximum Likelihood framework 4.3 / 3 ], s 3 1 can be replaced by π 17 π 2 − 15 4.6 δ ≈ = ) = 4.2 , and 0 d > e θ e f f e and E E 4.2 . An analytical approximation is found on this numerical , E , equation ( , d 0 src 4.5 < θ d 4.5 = d is chosen to be 100 TeV in this analysis, which corresponds to compares the radial profile as a function of the distance from the pulsar from in equation θ 0 3 e E t E is the diffusion angle at the pivot energy of is the angular distance from the pulsar and 0 θ θ HAWC observations reveal two very extended TeV gamma-ray sources spatially coincident We then fit the gamma-ray emission around Geminga and PSR B0656+14 with the diffusion Integrating the energy distribution of electrons and positrons along the observer’s line of sight, ], and calculate the diffusion coefficient of 100 TeV electrons based on the obtained diffusion 16 with Geminga and PSR 0656+14,in suggesting our ultra-relativistic neighborhood. electrons and The positronscoefficient results accelerated will of be the presented analysis at onsources ICRC2017. these to two the The sources local implication flux and on can the the be obtained found positron diffusion in contribution other of two these proceedings for this conference [ With a source distance of where The pivot energy 5. Results and Discussion model defined in equation angle from the likelihood fit. and gamma ray energy is given by [ three morphological models. [ and considering the gamma rays producedas through a ICS, function we of obtain the the distance morphology of gamma rays ICS off infrared and opticalas photons important in targets. the At ISM these ispulsars. energies, highly Therefore the suppressed, cooling leaving time only is CMB much photons shorter than the age of these two and the target field, gamma rays. Figure Constraining the Diffusion Coefficient with HAWC produce TeV gamma rays through ICS, where the Klein-Nishina effects are important [ where Combined with equation PoS(ICRC2017)690 Hao Zhou , Nature , Phys. Rev. 45 40 Disk Gaussian Diffusion 35 Spectrum from 20 GeV to 1 TeV with the 30 − e + 25 + (2009) 181101 [0905.0025] 6 102 20 Distance from Pulsar [pc] 15 10 , Phys. Rev. Lett. 5 Measurement of the Cosmic Ray e 0

First Result from the Alpha Magnetic Spectrometer on the International Space Station: An anomalous positron abundance in cosmic rays with energies 1.5-100 GeV 0.0 1.0 0.8 0.6 0.4 0.2 Surface Brightness [Arbitrary Unit] [Arbitrary Brightness Surface Radial profiles of three morphological models: disk, Gaussian, and diffusion model. (2013) 141102 110 (2009) 607 Figure 3: Fermi Large Area Telescope 458 Precision Measurement of the Positron Fraction inLett. Primary Cosmic Rays of 0.5-350 GeV We acknowledge the support from: the US National Science Foundation (NSF); the US De- [2] Abdo, A. A. et al., [1] Adriani et al., [3] Aguilar et al., Acknowledgments partment of Energy Office of High-Energyopment (LDRD) Physics; program the of Laboratory Los Directed Alamos National Researchnología Laboratory; and (CONACyT), Consejo México Devel- Nacional (grants de 271051, Ciencia 232656, y 260378,258865, Tec- 179588, 243290, 239762, 254964, 132197), 271737, Laboratorio Nacionalfor HAWC Women de in rayos Science 2014; gamma; Red L’OREAL HAWC,IN111716-3, Fellowship México; IA102715, DGAPA-UNAM (grants 109916, IG100317, IN111315, IA102917);2015;the VIEP-BUAP; University PIFI of Wisconsin 2012, Alumni 2013, Researchetary Foundation; PROFOCIE the 2014, Physics, Institute of and Geophysics, Signatures Plan- DEC-2014/13/B/ST9/945; at Coordinación Los de la Alamos Investigación National Científicacana. Laboratory; de Thanks la to Polish Universidad Luciano Science Michoa- Díaz and Centre Eduardo grant Murrieta for technical support. References Constraining the Diffusion Coefficient with HAWC PoS(ICRC2017)690 , , , Hao Zhou , Astrophys. J Proceedings of (2017) , in (2013) 023001 [1304.4128] 88 (2005) 1488 [astro-ph/0504388] , Phys. Rev. D The 2HWC HAWC Observatory Gamma-Ray 364 Proceedings of ICRC2017 (2010) 6 (2017) , in Electrons and positrons in the galactic cosmic rays 7 709 Pulsars as the sources of high energy cosmic ray positrons TeV Gamma Rays from Geminga and the Origin of the GeV (2009) 051101 [0810.2784] Propagation of cosmic-ray nucleons in the Galaxy 103 (2008) 063527 [0712.2312] (2014) 93 [1407.1657] (2009) 025 [0810.1527] 1 , Abeysekara, A. U. et al., 77 (2017) 40 [1702.02992] , Astrophys. J. Lett. 791 Proceedings of ICRC2017 , Mon. Not. Roy. . Soc. Klein-Nishina effects in the spectra of non-thermal sources immersed in 843 Observation of TeV Gamma Rays from the Fermi Bright Galactic Sources with Constraining the Origin of Local Positrons with HAWC TeV Gamma-Ray Positrons from annihilation in the galactic halo: Theoretical TeV Gamma-Ray Sources from a Survey of the Galactic Plane with Milagro The Multi-Mission Maximum Likelihood framework (3ML) (2007) 91 Very high energy cosmic gamma radiation : A crucial window on the extreme Measurement of Boron and Carbon Fluxes in Cosmic Rays with the PAMELA (1995) 3265 , Phys. Rev. Lett. 664 52 Pulsar interpretation for the AMS-02 result , Phys. Rev. D , Astrophys. J. (2015) [1507.08343] , World Scientific Publishing Co. Pte. Ltd. (2004) ISBN 9789812561732 , Astrophys. J. (1998) 228 [astro-ph/9807150] Observations of Two Nearby Pulsar Wind Nebulae Experiment external radiation fields The HAWC Collaboration Catalog Phys. Rev. D ICRC2015 Universe Astrophys. J. 212 uncertainties the Tibet Air Shower Array Positron Excess Cosmology Astropart. Phys. [8] Strong, A. W. & Moskalenko, I. V., [4] Yüksel, H., Kistler, M. D., & Stanev, T., [9] Delahaye, T. et al., [7] Amenomori, M. et al., [6] Abdo, A. A. et al., [5] Hooper, D., Blasi, P., & Dario Serpico, P. , [18] Lopez-Coto, R. et al, in [11] Adriani, O. et al, [12] [13] Atoyan, A. M., Aharonian, F. A. & Völk, H. J., [14] Moderksi, R. M. et al., [15] Aharonian, F. A., [17] Salesa Greus, F. et al, [16] Vianello, G. et al., Constraining the Diffusion Coefficient with HAWC [10] Yin, P. et al.,