Recent Chandra Observations of The Galactic Center

1. Recent Chandra Observations ofThe Galactic Center Observations: • Large-scale mapping • 360 ks (Wang, Gotthelf, & Lang 2002) • new 600 ks (Muno et al.) • Pointed • 100 ks each for Sgr B (Koyama et al.) and Sgr C • 50 ks for the Radio Arc (Yusef-Zadeh et al. 2002) • 100 ks for Arches cluster (Wang et al. 2006) • ~ 1 Ms for Sgr A (Baganoff et al. ) Qingde Daniel Wang

2. 0.8o 2o X-ray Sources Wang et al. (2002); Muno et al. (2006) Spatial resolution varies from subarcsecond on axis to a few arcseconds off-axis

3. Discrete X-ray sources: Summary of results • Discrete sources • ~ 1400 from the large-scale survey • ~ 2400 in the Sgr A* region alone. • LogN-LogS relation is flatter in massive SF regions • Nature of the sources • Bright ones (Lx > 1036 erg/s): X-ray binaries • Intermediate ones (1036 > Lx > 1033): transient LMXBs, colliding wind binaries, and young pulsars • Faint ones (1033 > Lx ): active low-mass stars (CVs) Consistent with existing radio and near-IR IDs or lack of them. Some sources have very hard intrinsic spectra (power law photon index < 1)

4. --- S XV K ---Ar XVII K ---Si XIII K ---Fe (neutral)K Diffuse X-ray emission: spectrum

5. SXV Line

6. Fe 6.7-keV line

7. Fe 6.4-keV Line

8. Diffuse X-ray emission: Summary of results • Diffuse X-ray Emission • Accounting for ~90% of the emission. • Showing strong He-like and H-like K lines from Si, S, Ar, Ca, and Fe  gas at T ~ 1 – 10 keV. • Global, but not detailed, correction between 6.4-keV Fe K line and cool dense clouds: reflection of past Sgr A* bursts, low-energy comic rays, and possible NEI plasma. • Probably largely due to coronally active binaries and CVs (Revnivtsev et al. 2005). • More quantitative modeling is needed!

9. Arches GC Quintuplet Massive star forming region: Composite Chandra map • Chandra Intensity: • 1-4 keV • 4-6 keV • 4-9 keV Wang, Hui, & Lang (2006)

10. Arches GC Quintuplet Massive star forming region:from radio to X-ray 20 cm (Yusef-Zadeh et al. 84) MSX 24 m (Price et al. 01) Chandra 1-9 keV (Wang et al. 06)

12. Arches Cluster: brightest X-ray sources in the core ACIS-I 1-9 keV NICMOS image (Figer et al. 99)

13. Arches Cluster: bright X-ray sources in the core • Remarkably similar thermal spectra • Metal abundance = 1.8 (1.6-2.6) solar • L(0.3-8 keV)=(0.5-11) x1033 erg/s • Late-type WN components • Likely to be extreme massive colliding wind binaries. Combined ACIS-I spectrum

14. Arches Cluster: diffuse X-ray emission

15. Arches Cluster: 6.7-keV line plume • Elongated and Size ~ 30” • Matches the region with an extinction deficit of Av~10 (Stolte et al. 02)

16. Fe Ka X-ray or electron Arches Cluster: the 6.4-keV line emission and a CS cloud • Not due to florescence: no spatial correlation with the CS cloud. • net too small to be due to a NEI plasma. • Likely due to low-energy cosmic-ray electrons interacting with the cloud (vr > 120 km/s). CS data: from OVRO+IRAM

17. Arches Cluster:Diffuse X-ray emission • In the core (r < 0.6 pc) • 6.7-keV line • Steep intensity decline • Probably due to the cluster wind • In the outer region • 6.4-keV line • Flat intensity profile • Probably due to the low-energy cosmic-ray electrons --- a result of the collision of the cluster wind with the CS cloud cluster wind (Rockefeller et al. 05) NICMOS Radial intensity profile

18. Arches cluster: Constraints on the IMF • YSOs (0.3-3 Msun) accounts for 75% of the Orion nebula Lx. • Each YSO has Lx ~ 1.2 x1030 erg/s per star (2-8 keV). • The observed total diffuse X-ray Lx ~ 2 x1034 erg/s (r < 2.5 pc)  an upper limit of 2x104 YSOs. • Miller & Scalo IMF overpredicts YSOs by > 10 • Power law with Γ~ -0.86 is consistent with the upper limit. X-ray limit Miller & Scalo IMF PL MF MF for r < 0.4 pc (Stolte et al. 05)

19. Quintuplet cluster: X-ray sources • Dimmer and diverse in spectral propertie • Some maybe embedded in dusty winds Wang et al. (2006) Law & Yusef-Zadeh (2004)

20. Quintuplet cluster: Diffuse X-ray emission • Very weak (Lx ~ 2 x1033 erg/s) • Cluster wind contribution is small • Follows approximately the stellar distribution • Probably mostly due to ~2x103 YSOs. cluster wind (Rockefeller et al. 2005) NICMOS

21. Galactic Center: inner pc region PWN? Sgr A* IRS 13 ACIS-I 1-9 keV (Wang, Lu, Gotthelf 06; see also Baganoff et al. 03) VLT SINFONI near-IR (Eisenharer et al. 05)

22. Comparison with other extended X-ray-emitting features Sgr A* PWN IRS 13 Diffuse The spectra of Sgr A*, IRS 13, and diffuse X-ray emission all show the Fe K line at ~6.6 keV  NEI emission from gas heated recently (net~103 cm-3 yr).

23. A PWN within 1 ly of Sgr A*? PWN? Sgr A* IRS 13 Red: radio (3.6 cm, Roberts & Goss 93) Green: near-IR (Eisenhauer et al. 05) Blue: X-ray (4-9 keV)

24. Evidence for the PWN Pulsar wind nebula • Nonthermal point-like source (putative pulsar) • Comet-like shape: ram-pressure confinement • Spectral steepening with off-source distance • Inverse-Compton scattering of the ambient radiation, a natural explanation of the TeV emission from the GC. Shock into SN ejecta • Does the pulsar origin in the GC cluster? • What effect on the GC environment?

25. Conclusions • About 4000 X-ray sources are detected within 0.8x2 deg2 GC region. • IDs have been difficult, but will be easier with improved source position accuracy (<1”). • Some of the X-ray sources are likely to be young pulsars and extreme colliding wind massive binaries. • Bulk of faint sources are due to low-mass old stars. • X-ray-inferred Fe abundance is ~ 2 x solar. • Limits on # of YSOs indicate top-heavy IMFs of young clusters. • Collisions between young clusters and molecular clouds may be important in star formation.

26. M31 28’x28’ FoV Red: 0.5-1 keV Green: 1-2 keV Blue: 2-4 keV) NASA/UMass/Z.Li & Q.D.Wang

27. M31 Bulge Red: Mid-IR (Spitzer) Green: 0.5-2 keV) Blue: 2-4 keV Red: 0.5-1 keV Green: 1-2 keV Blue: 2-4 keV)

28. M31 Nuclear Region 10 ly X-ray images: (NASA/SAO/CXC/M.Garcia et al.)Optical Contours: (NASA/GSFC/T.Brown et al.)