Shock-cloud interaction in the Vela SNR: the XMM-Newton view M. Miceli 1, F. Bocchino 2, A. Maggio 2, F. Reale 1 1.Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo 2. INAF-Osservatorio Astronomico G. S. Vaiana di Palermo

Interaction between the blast-wave shock of a middle- aged SNR and the inhomogeneities of the ISM. Low spatial resolution (> 5’). Low A eff. Low spectral resolution (E/  2) Low A eff. Geometry of the system? No detailed comparison between X-ray and optical emission. Difficulty in estimating the physical parameters of the plasma. Detecting NEI effects. The analysis of past X-ray observations left many open issues: Impossibility of unambiguously describing the physics of the shock-cloud interaction.

The data Guaranteed Time Observation. Coordinates:  (2000)=8 h 35 m 44 s ;  (2000) = -42º35’29’’. Exposure time: 26.8 ksec (PN); 31.1 ksec (MOS). Mode: Extended Full Frame (PN); Large Window (MOS). Filter: Medium.

Our aims: Describing the morphology of the ISM clouds (shape, dimension, spatial distribution…). Obtaining information about the physical properties and the internal structure of the clouds. Studying the dynamics and the evolution of the shock- cloud interaction. ROSAT All Sky Survey ( keV)

~ 2.4 pc EPIC count rate images  cnt/s FilD RegNE

Comparison between X-ray and optical emission in the FilD region Color coding: Green: H  emission Violet: OIII emission Red: X-ray contour levels ( keV) Maximum X-ray contour levels are just outside the optical filament: the optical emission follows a path that grazes, without crossing, the brightest X-ray FilD regions.

Regions selected for spectral analysis Color coding: Black: FilD Red: South-Western region Blue: RegNE In each region the mean photon energy E has low fluctuations:  E/E avg  keV

Spectral analysis Representative folded spectrum All spectra are well described by two MEKAL components O/O  = 1.0 ± 0.1 Ne/Ne  = 1.7 ± 0.2 Fe/Fe  = 0.39 ± 0.05

T II (10 6 K) T I (10 6 K) cnt/s The values of the temperature of both components don’t show significant variations in the field of view.

n I 2 L I (10 17 cm -5 ) n II 2 L II (10 17 cm -5 ) For both components the product n 2 L (where n is the particle density and L is the extension along the line of sight) presents huge inhomogeneities in the field of view. cnt/s

Evolution of the shocked clouds Corona: n = 0.5  1.9 cm -3 T  3.0  10 6 K Core: n = 1.4  5 cm -3 T  1.14  10 6 K Optical filament: n = 3.2  8.2 cm -3 T = 3  10  10 4 K Evaporation Collapse Intercloud medium: n < 0.07 cm -3 T = 4  8  10 6 K  rad >  cond  rad <  cond

Conclusions: We resolved different phases in ISM clouds. 3-D map of the observed clouds (FilD mass  g for a core particle density of 2 cm -3 ). Discriminate model (no reflected shocks). Evolution of the shocked clouds cores: radiative cooling collapse coronae: thermal conduction evaporation