shock-cloud interaction in the vela snr: the xmm-newton view
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Shock-cloud interaction in the Vela SNR:Shock-cloud interaction in the Vela SNR: the the XMM-NewtonXMM-Newton view view
M. Miceli1, F. Bocchino2, A. Maggio2, F. Reale1
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 Aeff.
• Low spectral resolution (E/ 2)
• Low Aeff.
• 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 Impossibility of unambiguously unambiguously describing the physics describing the physics of the shock-cloud of the shock-cloud interactioninteraction..
The data
• Guaranteed Time Observation.
• Coordinates: (2000)=8h35m44s ; (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 (0.2-2.4 keV)
~ 2.4 pc
EPIC count rate images
0 7.210-5cnt/s 0
cnt/s 10-4
FilD
RegNE
Comparison between X-ray and optical emission in the FilD region
Color coding:
Green: Hemission
Violet: OIII emission
Red: X-ray contour levels (0.3-0.5 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/Eavg 0.04
0.3-2 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
TII (
106 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 I2 LI (
1017
cm
-5)
n II2 L
II (
1017
cm
-5)
For both components the product n2L (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 3.0 106 K
Core: n = 1.4 5 cm-3
T 1.14 106 K
Optical filament: n = 3.2 8.2 cm-3
T = 3 10 104 K
Evaporation
Collapse
Intercloud medium: n < 0.07 cm-3
T = 4 8 106 Krad> cond
rad> cond
rad< cond
Conclusions:
• We resolved different phases in ISM clouds.
• 3-D map of the observed clouds
(FilD mass 1031g 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
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