1. Internal Irradiation of the Sgr B2 Molecular Cloud Casey Law Northwestern University, USA A reanalysis of archived X-ray and radio observations to understand the cause of fluorescent iron line emission in Sgr B2. Collaborators: F. Yusef-Zadeh, M. Fromerth, and F. Melia Outline: 1) Fluorescent iron emission in the GC 2) X-ray observations of diffuse and compact sources 3) Is a Sgr A* flare needed? 5 th APC – High Energy Phenomena in the GC, Paris

2. - Sgr B2 shows strong fluorescent iron emission at 6.4 keV (Koyama et al. 1996). - Line emission can be explained by Sgr A* flare 10 6 times its current luminosity. - Sgr A* flare ended in the past 300 years and lasted dozens of years. Sgr B2 Fluorescent Iron and Sgr A* Could there be an alternate explanation? 5 th APC – High Energy Phenomena in the GC, Paris (Left) 20cm radio continuum and (Right) Chandra smoothed fluorescent iron line flux of Sgr B on the same scale.

3. Other Fluorescent Sources in the GC 5 th APC – High Energy Phenomena in the GC, Paris G0.13 – 0.13 - EW ~ 0.9 keV - GC absorption, no iron absorption edge - brightest emission at edges, near NRFs Sgr C - EW ~ 0.5, 1.5 keV - GC absorption - one source near NRF Arches Cluster - EW ~ 0.8 keV - GC absorption - X-ray luminous cluster 6.4 keV with molecular gas contours Radio gray with X-ray continuum contours X-ray continuum in color and contours

4. 5 th APC – High Energy Phenomena in the GC, Paris Morphology of Line Emission - “Tilemap” method fits spectra and maps spectral parameters. - Significant fluorescent emission throughout Sgr B. (Left) Sgr B fluorescent iron flux according to tilemap and (Right) adaptive smoothing.

5. Spectral Modeling of Diffuse X-ray Emission Continuum Properties: - Highly absorbed: N H ~ 4-6 x 10 23 cm -2 - Continuum can be modeled as 1) power law:  ~ 0.6 2) power law + thermal bremsstrahlung: kT ~ 1 keV,  ~ 0, with similar 2-10 keV fluxes Line Properties: - Iron K α line Equivalent Width ~ 1.5 keV - Iron K α luminosity: 1.5e34 ergs s -1 Fluorescence likely caused by irradiation. Hard spectrum required, but thermal not - Strong iron edge at 7.1 keV excluded. 5 th APC – High Energy Phenomena in the GC, Paris Sgr B2 diffuse X-ray spectrum

6. Embedded Compact X-Ray Sources X-rays with radio continuum contours from Takagi et al. (2002) 5 th APC – High Energy Phenomena in the GC, Paris Source 13: - Thermal bremss with kT ~ 1 keV - N H ~ 4 x 10 23 cm -2 L(2-10 keV) ~ 5 x 10 33 ergs s -1 X-ray emission fills faint radio- continuum shell. Source 10: - Power law with  ~ 0-1 - N H ~ 2-4 x 10 23 cm -2 - 6.5 keV line with EW ~ 2-3 keV L(2-10 keV) ~ 5 x 10 32 ergs s -1 “Warm” fluorescent iron.

7. Is a Sgr A* Flare Needed? Morphology (Above) Fluorescent iron with HII regions, masers and hot cores. (Below) CH 3 CN from de Vicente et al. (1997) 5 th APC – High Energy Phenomena in the GC, Paris or does shape show intrinsic structure? Does the shape require external irradiation? Fluorescent iron with molecular line contours from Murakami et al. (2001)

8. Can Internal Sources Cause Fluorescence? Required hard X-ray flux: I 8 req = 7x10 33 (4  T ) (6.6x10 -5 /∞  Fe ) ergs s -1 keV -1 (Sunyaev & Churazov 1998) Observed sources: For  =4  and  T =0.25 ==> I 8 obs = 0.005 I 8 req In total, the two X-ray point sources can explain at least 0.5-1% of fluorescent emission. Scaling by radio continuum ==> all 50 UCHII regions can explain 5-10% of emission. Consistent with wind/ISM shocks, where 1% of wind luminosity ==> ~1 keV gas: I 8 ws = 7x10 32 (M/2x10 -6 M ◦ yr -1 ) (v ∞ /2800 km s -1 ) 2 (N UCHII /50) ( Smith et al. 2005) What more might be expected from internal sources? - Colliding wind binaries? I 8 cwb ~ 10 32-34 ergs s -1 keV -1 (Portegies-Zwart et al. 2002) - Scaling diffuse X-ray continuum by radio diffuse-to-compact flux ratio: L 2-10 keV ~ 7x10 34 ergs s -1 must be hidden by cloud. The Sgr B2 molecular cloud can easily hide these sources from detection with N H ~ 10 24-25 cm -2. 5 th APC – High Energy Phenomena in the GC, Paris

9. Conclusions 1) Some, but not necessarily all, irradiation flux is nonthermal. 2) Sgr B2 fluorescent morphology seems to follow intrinsic gas conditions. 3) Observed X-ray sources cause 0.5-1% of Sgr B2 fluorescence. 4) Colliding-wind binaries and wind-ISM shocks can account for significant amounts of fluorescence and may remain undetected. Possible test: Check for morphological variability in fluorescent emission. 5 th APC – High Energy Phenomena in the GC, Paris

11. - Sgr B2 shows strong fluorescent iron emission at 6.4 keV (Koyama et al. 1996). - Line emission can be explained by Sgr A* flare 10 6 times its current luminosity. - Sgr A* flare ended in the past 300 years and may have lasted >70 years. Sgr B2 Fluorescent Iron and Sgr A* Could there be an alternate explanation? 5 th APC – High Energy Phenomena in the GC, Paris (Left) Adaptively smoothed and (Right) “Tilemap” of fluorescent iron line flux.

12. Can Internal Sources Cause Fluorescence? Required hard X-ray flux: I 8 req = 7x10 33 4  T 6.6x10 -5 /∞  Fe ergs s -1 keV -1 (Sunyaev & Churazov 1998) For  =4  and  T =0.25 ==> I 8 obs = 0.005 I 8 req In total, the two X-ray point sources can explain at least 0.5-1% of fluorescent emission. What more might be expected from internal sources? - Colliding wind binaries? I 8 cwb ~ 10 32-34 ergs s -1 keV -1 (Portegies-Zwart et al. 2002) - Scale by radio continuum ==> all UCHII regions have I 8 uchii = 5-10x10 32 ergs s -1 keV -1 (5-10%) - Young stellar wind shocks? 1% of wind luminosity ==> ~1 keV gas: ( Smith et al. 2005) I 8 ws = 7x10 32 (M/2x10 -6 M ⊙ yr -1 ) (v ∞ /2800 km s -1 ) 2 (N UCHII /50) - Early-type stars? I 8 es ~ 5x10 30 ergs s -1 keV -1 (  1 Ori C, Schulz et al. 2003) The Sgr B2 molecular cloud can easily hide these fluxes from detection with N H ~ 10 24- 25 cm -2. 5 th APC – High Energy Phenomena in the GC, Paris