S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/20071 Studying the Galactic Ridge Emission with SIMBOL-X Sandro Mereghetti IASF - Milano

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/20072 Galactic Ridge X-ray Emission X-ray emission extending along the Galactic plane Longitude extent ~ +/- 40 deg  Inner Galaxy R ~ 4 kpc Latitude extent ~ few deg  small scale height ~100 pc High peak at GC Luminosity ~ 2 10^38 erg/s Intense emission lines

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/20073

4 Double T NEI model Soft component kT~0.8 keV Hard component kT~7 keV

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/20075 Valinia et al. 2000

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/20076 Lebrun et al Nature GRXE resolved by IBIS above 40 keV keV keV 60 – 120 keV keV

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/20077

8 Ebisawa et al. 2005

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/20079 NO IMAGING DISCRETE SOURCES ? IMAGING DIFFUSE EMISSION SIMBOL-X

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ Simbol-X contribution: 1.Population studies in hard X-rays 2.Mapping of emission lines 3.Imaging-spectroscopy at >10 keV with point sources removed

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ Several hundreds of pointings at low Galactic latitude FoV =  (0.1)^2 ~ 0.03 square deg  Sky coverage ~ several square deg  Sensitivity tens of  Crabs (100 x better than IBIS)  ~ 10 sources/square deg (2-10 keV) 1 ) Population studies Highly absorbed HMRXB discovered by INTEGRAL Tip of the iceberg ?  ~100 serendipitous sources..but how many in the keV ?

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ ) Mapping of emission lines Compare with XMM / EPIC :  Effective area larger than EPIC pn at E >~4-5 keV  similar energy resolution  similar angular resolution  much lower instrumental background Anticoincidence system Soft protons magnetic diverter  better modelling of continuum emission thanks to extended energy range

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ ) Spectroscopy above 10 keV Done up to now only with collimated instruments Difficult to correctly estimate point sources contribution Deep pointings of selected regions in Galactic Plane can for the first time properly measure the GRXE spectrum Also the spatial distribution, e.g. latitude dependence, can be directly measured

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ Simulation of 500 ks pointing with Simbol-X spectrum of diffuse emission from 6 arcmin radius extraction region

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/200715

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ ) Spectroscopy above 10 keV Done up to now only with collimated instruments Difficult to correctly estimate point sources contribution Deep pointings of selected regions in Galactic Plane can for the first time properly measure the GRXE spectrum Also the spatial distribution, e.g. latitude dependence, can be directly measured CAVEAT: Accuracy depends ultimately on good knowledge of instrumental background It is essential to control the systematics uncertainties

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ Formation flight can help: Mirror field of view detector

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ Formation flight can help: detector

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ Formation flight can help: detector

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ Formation flight can help: detector

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ Formation flight can help: Mirror field of view detector The external parts of the detection plane can monitor the instrumental background

S.Mereghetti - Simbol-X: The hard X-ray Universe in focus - Bologna -15/5/ Conclusions The spectral/imaging capabilities of SX will allow for the first time detailed studies of the GRXE above 10 keV It will be possible to determine the contribution of hard X- ray sources and verify if a hot plasma is really needed These studies have obvious implications on our understanding of the X-ray emission from the Galactic Center region Several dedicated long (~500 ks) pointings required in addition to results from “serendipitous” sources A small background level is not enough: It is essential to be able to reproduce its spatial and temporal variations