1. 1 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. X-ray Investigation of  -ray Excess in Cygnus Region “Cygnus Cocoon” by Suzaku ( 「すざく」による白鳥座に発見さ れたガンマ線超過の X 線探査 ) T. Tanabe, H. Takahashi (Hiroshima Univ.), K. Hayashi (ISAS/JAXA), R. Yamazaki (AGU), I. Grenier (CEA Saclay), L. Tibaldo (SLAC) March 29 th, 2014 Tsunefumi Mizuno (Hiroshima Univ.)

2. 2 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Contents Introduction (  -ray excess “Cygnus Cocoon”) Observations by Suzaku Data Analysis Discussion Summary & Future Plan

3. 3 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Cygnus Cocoon (Morphology) GeV  -ray excess revealed by Fermi in star-forming region Cygnus-X Morphology follows the regions bounded by ionization fronts. No apparent spectral variations in different parts. Efficient confinement and/or acceleration of cosmic-rays (CRs) in the interstellar space Excess  -ray map (E>10 GeV) Cygnus OB2 NGC6910 Ackermann+11  -Cygni

4. 4 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Cygnus Cocoon (  -ray Spectrum) “Cygnus Cocoon” = GeV  -ray excess revealed by Fermi in star-forming region Cygnus-X Hard and Intense CRs are required to explain  -ray spectrum H II x local CR-p Inverse Compton from local CR-e Milagro LAT Their origin and properties to be studied by multiwavelength obs. including X-rays Ackermann+11

5. 5 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Observation We performed Suzaku- XIS observations to investigate properties of CRs responsible for Cocoon (particle type, spectrum, etc.) Excess  -ray map (E>10 GeV) regionobs. dateexposure [ksec] (COR > 6 GV) Source12012/Nov.43.3 Source22013/Nov.46.4 BG12012/Nov.19.9 BG22012/Nov.25.6

6. 6 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. XIS Image (Source1) Count map of XIS0+3, smoothed with  =0.2 arcmin A few sources and/or small structures were identified and excluded to investigate the (possible) extended emission from Cygnus Cocoon 0.4-2 keV 2-10 keV Cal Source

7. 7 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Modeling of Extended Emission (1) Point sources and/or small structures removed Non X-ray Background (NXB) subtracted (xisnxbgen) The remain = Cosmic X-ray background (CXB) +Galactic Ridge X-ray Emission (GRXE) +possible emission from Cocoon –CXB is fixed to PL of (  =1.41, N=9.6x10 -4 [c/s/cm 2 /keV]) based on Kushino+02. N(H)=2x10 22 [cm 2 ] assumed –GRXE is modeled by three-temperature plasma (apec) based on Uchiyama+09 –Then examine residuals in spectrum to see if there are any excess (=possible emission from Cocoon)

8. 8 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Modeling of Extended Emission (2) Point sources and NXB subtracted The remain = CXB+GRXE(+possible emission from Cocoon) –CXB is fixed to PL of Kushino+02. –GRXE is modeled with three-temperature plasma (Uchiyama+09) count/s/keV Energy [keV]  Source1 Spectrum (XIS0) apec: Soft (~0.05 keV) apec: Medium (~0.7 keV) PL (CXB) apec: Hard (~5 keV)

9. 9 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Latitude Dependence of Extended Emission Point sources and NXB subtracted The remain = CXB+GRXE(+possible emission from Cocoon) CXB-subtracted brightness shows monotonous decrease as latitude increases (as GRXE does) brightness [10 -7 erg/s/cm^2/sr] Galactic Latitude [deg] BG1 BG2 Source1 Source2 CXB-subtracted brightness (2-10 keV) Most of (CXB-subtracted) emission comes from GRXE region CXB-subtracted brightness @2-10 keV [erg/s/cm 2 /sr] Source1 Source2 BG1 BG2

10. 10 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. CRs to explain Cygnus Cocoon in X-ray and  -ray Most of CXB-subtracted emission comes from GRXE Conservative upper limit of X-rays from Cocoon is obtained by subtracting brightness of BG2 (=lower limit of GRXE at source positions) regionupper limit of X-rays from Cygnus Cocoon Source1 Source2 Upper limit of X-ray emission (av. of S1 and S2) <= 40% of the expectation of electron scenario  -ray excess is due to (1) CR protons or (2) CR electrons with cutoff at <= 50 TeV

11. 11 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Summary & Future Plan We observed Cygnus Cocoon (  -ray excess in Cygnus-X found by Fermi) by Suzaku-XIS Most of extended emission comes from CXB+GRXE Conservative upper limit of X-rays from Cocoon is <=40% of electron scenario expectation, suggesting –(1)  -ray excess is due to protons, or –(2) electrons with cutoff at <= 50 TeV Detailed discussion based on multiwavelength spectrum is underway

12. 12 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Reference Ackermann+11, Science 334, 1103 Kushino+02, PASJ 54, 327 Uchiyama+09, PASJ 61, S189 Kaneda+97, ApJ 491, 638

13. 13 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Backup Slides

14. 14 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Latitude Dependence of Extended Emission regionScale height Cygnus Cocoon Source & BG 1.26±0.29 [deg] Scutum arm (Kaneda+97) 0.64±0.10 [deg] Scale height of extended emission in Cygnus Cocoon region is ~2 larger than that of Scutum arm (l=28deg; Kaneda+97), probably due to the proximity of Cygnus-X BG1 BG2 Source1 Source2 Galactic Latitude [deg] brightness [10 -7 erg/s/cm 2 /sr] CXB-subtracted brightness Most of extended emission can be interpreted to be from GRXE

15. 15 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Conservative upper limit of X-ray emission is <=40% of the expectation, requiring cutoff of CR electron (in electron scenario) Simple Argument of CR Electron Cutoff Synchrotron X-ray For B=20 μG, E e of 50 TeV required to produce 1 keV X- ray In electron scenario, cutoff in <= 50 TeV is required to explain (non-detection of) X-rays

16. 16 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al.  -ray emission = diffuse emission (ISM x Galactic CR)+point sources Excess is a signature of unknown high-energy objects/phenomena  -ray Count Map Count Map (E>10 GeV) Galactic diffuse and known sources subtracted  -Cygni subtracted

17. 17 2014-03_CygCocoon_Suzaku_JPS.ppt T. Mizuno et al. Optical from Cygnus OB2 and NGC 6910 Infrared (dust emission) measured by IRAS Radiation Field inside Cocoon 1 meV 1 eV