Shock-cloud interaction in the Vela SNR: the XMM-Newton view

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