September 25, meeting Tsunefumi Mizuno (Hiroshima Univ.)

Presentation on theme: "September 25, meeting Tsunefumi Mizuno (Hiroshima Univ.)"— Presentation transcript:

1 September 25, 2015@JPS meeting Tsunefumi Mizuno (Hiroshima Univ.)
「すざく」による広がったTeVガンマ線放射VER J のX線観測(2) Suzaku Observation of the extended TeV gamma-ray source VER J (2) September 25, meeting Tsunefumi Mizuno (Hiroshima Univ.) N. Tanaka, H. Takahashi, J. Katsuta (Hiroshima Univ.), K. Hayashi (ISAS/JAXA), R. Yamazaki (AGU)

2 Contents Introduction Past obs. in TeV g-rays and X-rays
Observations by Suzaku Data Analysis and Results Discussion Summary 白鳥座X方向、広がったTeVガンマ線放射のX線フォローアップ観測が主題 紹介、観測、解析、議論(Preliminary)

3 Past Obs. by Milagro & VERITAS
Milagro reported an extended TeV g-ray source MGRO J in Cygnus-X direction (s=0.7deg) It was resolved into multiple sources by VERITAS. The most luminous one, VER J , has the following properties smajor=0.34deg, positional coincidence with MGRO J , consistent spectrum in high energy => Main contributor Possible X-ray counterpart is PSR J & PWN G MGRO J E>1TeV E=0.6-1TeV まず最初にMilagroが報告 分解能に優れたVERITASによって分解。メインがVER J 諸元(morphology) 諸元(スペクトル) Milagroソースのメインとみなせる。 PSR J およびPWNが対応天体の最有力候補 VER J (G=1.75, F(1-10TeV)=6.7x10-12 erg/s/cm2) Aliu+14, ApJ 788, 78 Aliu+14, ApJ 788, 78

4 Past Obs. in X-Rays Possible X-ray counterpart is PSR J & PWN G PSR J : young and energetic (t=17 kyr, dE/dt=3.4x1036 erg/s) Chandra revealed a ~20”x10” pulsar wind nebula (PWN G ) XMM reported faint emission of 5’-10’ length in east and west 30” これまでのX線観測 PSR J はそもそも強力な電波パルサー Chandraにより、PWNが発見される(10-20”程度) XMMにより、数分角に広がったPWN放射が報告 10’ Hessels+04, ApJ 612, 389 Zabalza+10, J. of Mod. Phys. D. 19, 811

5 Problems of the PSR/PWN Scenario
Possible X-ray counterpart is PSR J & PWN G PSR J : t=17 kyr, dErot/dt=3.4x1036 erg/s PWN G : revealed by Chandra and found to extend out 5’-10’ in length in east and west by XMM Several issues of the PSR/PWN scenario have been pointed out (e.g., Abdo+09, ApJ 799, 1059; Parades+09, A&A507, 241) Large dispersion measure (370 pc/cm3) and rotation measure (524 rad/m2) indicate large distance to the source (d>10 kpc). g-ray luminosity of PSR too high compared to dErot/dt Source size (~90 pc for 0.5 deg at 10 kpc) too large for high-energy electrons to fill before cooling X-rays from only small portion of TeV emission Detailed study of the PWN properties (spectrum, morphology) and search for unknown extended emission by Suzaku-XIS PWN起源説には問題も指摘されている 距離が遠い ガンマ線高度が高い(spin down luminosityに比べて) Egamma(1-10TeV)=8x10^34 erg/s 領域が広い(電子の冷却時間) X線はTeV放射の一部からのみ 広がった放射に強い「すざく」による観測

6 Suzaku Obs. of VER J Two observations conducted in 2014 November. P2 covers region of the PSR/PWN and TeV centroid P3 covers the west part of VER J , in which no strong X-ray sources are reported Net exposure is ~35 ks each (COR>6 GV) Position RA (deg) DEC Net exp. (ks) P2 305.07 36.85 35.0 P3 304.80 36.80 35.7 P2 P3 「すざく」観測の諸元 時期、場所、積分時間 図を用いて説明

7 XIS Image (soft band) Soft band (0.7-2 keV) intensity map (XIS3, in unit of photos/s/cm2/sr, nxb subtracted) PWN clearly detected in P2 No obvious extended emission in P3 Soft bandイメージ、XIS3 P2からはPWNの放射 P3からは、はっきりした放射はない(定量的な解析はこれから) P2, keV P3, keV

8 XIS Image (hard band) Hard band (2-10 keV) intensity map (nxb subtracted) PWN clearly detected in P2 No obvious extended emission in P3 Size of PWN similar to that in soft band (see slide #11 for details) hard bandイメージ、XIS3 P2からはPWNの放射 P3からは、はっきりした放射はない PWNのサイズ・形状はsoft bandと似ている(定量的な解析はこれから) P2, 2-10 keV P3, 2-10 keV

9 PWN-West Morphology (1)
Source regions: 25 rectangles of 1’ x 5’ or 1’ x 4’ (unusable area of XIS0 and cal-source emitted regions avoided) BG region: 4’ x 10’ BG sources (excluded) PSR J USNO-B1.0 PWN (0-17’) PWN (14-25’) P2, keV P3, keV Soft bandイメージ、XIS3 P2からはPWNの放射 P3からは、はっきりした放射はない(定量的な解析はこれから) background AGN? P2, 2-10 keV P3, 2-10 keV

10 PWN-West Morphology (2)
Source regions: 25 rectangles of 1’ x 5’ or 1’ x 4’ (unusable area of XIS0 and cal-source emitted regions avoided) BG region: 4’ x 10’ sources (excluded) PWN (0-17’) BG P2, keV P3, keV (14-25’) PWN emission is detected at least up to 15’, roughly reaches to the TeV centroid No obvious emission beyond the TeV centroid In spectral analysis (arf calculation), we assume linear decrease of intensity (like dotted line below) Count rate profiles, vignetting corrected Soft bandイメージ、XIS3 P2からはPWNの放射 P3からは、はっきりした放射はない(定量的な解析はこれから)

11 PWN-West Spectrum (1) Procedure of the spectral analysis: XIS0 XIS1 BG
1) subtract the NXB 2) apply vignetting correction in subtracting the BG (GRXE and CXB) 3) calculate the response (arf) assuming linear decrease of the intensity in 0-15’ XIS0 XIS1 XIS3 BG sources (excluded) PWN (0-15’) P2, keV chi2/dof=211/188 N(H)=0.83(+/-0.12)x1022 G=2.05(+/-0.12) Soft bandイメージ、XIS3 P2からはPWNの放射 P3からは、はっきりした放射はない(定量的な解析はこれから) f(0.5-2 keV)=6.04x10-13 erg/s/cm2 f(2-10 keV)=20.0x10-13 erg/s/cm2 Unabsorbed spectrum: E2F(E)=906x10-6 (E/keV)-0.05 keV2/s/cm2/keV

12 PWN-West Spectrum (2) Procedure of the spectral analysis: BG A B C D E
1) subtract the NXB 2) apply vignetting correction in subtracting the BG (GRXE and CXB) 3) calculate the response (arf) assuming linear decrease of the intensity in 0-15’ Reg. N(H) G F(0.5-2keV) (10-13 erg/s/cm2) F(2-10keV) A (0’-3’) 0.82 (+/-0.21) 2.07 1.96 8.27 B (3’-6’) 0.63 (+/-0.16) (+/-0.18) 1.67 6.52 C (6’-9’) 0.72 (+/-0.17) 2.06 1.24 4.70 D (9’-12’) 1.28 (+/-0.36) 2.30 (+/-0.32) 0.57 2.77 E (12’-15’) 1.44 (+/-0.51) 2.29 (+/-0.42) 0.30 1.68 BG sources (excluded) A B C D E PWN (0-15’) P2, keV No significant spectral change observed From the obtained absorption of ~0.8x1022 cm-2, d~3 kpc (instead of >10 kpc) indicated Soft bandイメージ、XIS3 P2からはPWNの放射 P3からは、はっきりした放射はない(定量的な解析はこれから)

13 MW Spectrum (+ example of model)
Data: Radio upper limit at 610 MHz, GeV PSR and PWN upper limit, VER J and Suzaku PWN-West*2 Model: E-2 electron spectrum with exponential cutoff at 0.1 PeV assumed Synchrotron (B=3 mG) and IC (CMB, IR(T=20K, 0.4 eV/cm3)) calculated Integrated spectrum is compatible with standard scenario (synchrotron by interstellar mag. field and IC by ISRF), although the details (cooling, morphology etc.) is yet to be investigated

14 Thank you for your Attention
Summary & Future Plan VER J is an extended (smajor=0.34deg) and hard (G=1.75) TeV g-ray source in Cyg-X direction PSR J /PWN G is a possible counterpart, but several issues are pointed out (distance, morphology) We analyzed Suzaku-XIS data in detail PWN detected up to 15’ to the west (N(H)=8.2x1021 cm-2, G=2.05, f(2-10 keV)=2.0x10-12 erg/s/cm2) No significant spectral change found Next Step: Discuss the scenario to explain X-rays and TeV g-rays まとめと今後 ご静聴有難うございました。 Thank you for your Attention

15 Reference Abdo+12, ApJ 753, 159 Aliu+14, ApJ 788, 78
Hessels+04, ApJ 612, 389 Zabalza+10, J. of Mod. Phys. D. 19, 811 Parades+09, A&A 507, 241 Yoshida+11, PASJ 63, S717 Mizuno+15, ApJ 803, 74 Abdo+09, ApJ 700, 1059 Etten+08, ApJ 680, 1417 Watters+09, ApJ 695, 1289

16 Appendix

17 Past Obs. by Milagro & VERITAS
Milagro reported an extended TeV g-ray source MGRO J in Cygnus-X direction (s=0.7deg) It was resolved into multiple sources by VERITAS. The most luminous one, VER J , has the following properties smajor=0.34deg, positional coincidence with MGRO J , consistent spectrum in high energy => Main contributor E>1TeV E=0.6-1TeV まず最初にMilagroが報告 分解能に優れたVERITASによって分解。メインがVER J 諸元(morphology)。同じ大きさ・位置の円(座標系は異なる) Abdo+12, ApJ 753, 159 Aliu+14, ApJ 788, 78 Aliu+14, ApJ 788, 78

18 Properties and Implications
N(H) of the PWN ~0.8x1022 cm-2, similar to that of the PSR (Hessels+04) Sources in Cygnus-X (d~1.4 kpc) shows absorption of ( )x1022 cm-2 (Yoshida+11), whereas Galactic total absorption is estimated to be (2-3)x1022 cm-2 (Mizuno+15). => d~3 kpc is indicated. Then the g-ray luminosity of the PSR ~ 4.6x1035 erg/s < dErot/dt=3.4x1036 erg/s. F(2-10 keV)~2.0x10-12 erg/s/cm2 for the west part of the PWN F(1-10 TeV)/F(2-10 keV) ~3. It will be further reduced if we include the whole emission of the PWN PWN extends up to 15’ to the west, roughly reaches to the TeV centroid No significant spectral change observed. No significant diffuse emission in P3 (beyond TeV centroid) found If all these properties can be explained simultaneously or not (=PWN scenario) in under investigation 議論 吸収は8x10^21程度、距離は3kpc程度(Cygnus-Xよりは遠いかも)。サイズが小さくなるので、電子coolingの面では楽になる TeV/X線比は6程度。PWN全体を積分すればさらに2倍くらい小さくなると思われる。極端にX線darkではない。 VERITAS論文で議論されているようなoffset PWNが一つの可能性 X線の広がりの詳細、TeV中心より西側からの放射の制限が重要 XMMデータの解析も重要 これらが今後の課題。解析方法・議論について是非コメント頂きたい

19 XMM View of the VER J2019+368 Region
Advantages of XMM for the study of VER J Good spatial resolution => reduction/estimation of the point-source contaminations Large FOV => overall property of the PWN observation region No. of obs. Exposure [ks] PSRJ 1 127 WR142 2 61 , 20 MGROJ 48 IGRJ 16 G 34 , 30 PWN起源説には問題も指摘されている 距離が遠い ガンマ線高度が高い(spin down luminosityに比べて) Egamma(1-10TeV)=8x10^34 erg/s 領域が広い(電子の冷却時間) X線はTeV放射の一部からのみ 広がった放射に強い「すざく」による観測 (Analysis done by N. Tanaka)

20 PSR J2021+3651 Region Seen by XMM (1)
Main sources of contamination to PWN-west are PSR J and a bright start USNO-B (see also Etten+08) PWN起源説には問題も指摘されている 距離が遠い ガンマ線高度が高い(spin down luminosityに比べて) Egamma(1-10TeV)=8x10^34 erg/s 領域が広い(電子の冷却時間) X線はTeV放射の一部からのみ 広がった放射に強い「すざく」による観測 soft band (0.2-2 keV) hard band (2-10 keV) (Analysis done by N. Tanaka)

21 PSR J2021+3651 Region Seen by XMM (2)
Main sources of contamination to PWN-west are PSR J and a bright start USNO-B (see also Etten+08) PWN起源説には問題も指摘されている 距離が遠い ガンマ線高度が高い(spin down luminosityに比べて) Egamma(1-10TeV)=8x10^34 erg/s 領域が広い(電子の冷却時間) X線はTeV放射の一部からのみ 広がった放射に強い「すざく」による観測 Very soft spectrum (G>5), contribution to PWN-west is estimated to be ~10% and ~2% below and above 2 keV, respectively, even if we do not exclude the source. Contribution from less-bright sources is negligible. (Analysis done by N. Tanaka)