Diagnostics of the origin of X-ray emission in Cygnus Loop

Xin Zhou, INAF – Osservatorio Astronomico di Palermo, Italy & Nanjing University, China

Collaborators: Collaborators:

Fabrizio Bocchino, INAF – Osservatorio Astronomico di Palermo, Italy Marco Miceli, Università di Palermo, Italy & INAF – Osservatorio

Astronomico di Palermo, Italy Salvatore Orlando, INAF – Osservatorio Astronomico di Palermo, Italy

Yang Chen, Nanjing University, China

ROSAT HRI

•Numerical models

•Diagnostic tools

•Observation

•The role of TC

Numerical Models:

Orlando et al, 2005, A&A, 444, 505; Orlando et al. 2010, A&A, 514, 29

Case table

nISM=0.1 cm-3

TISM=104 K

Results of models — fluid structure:

Orlando et al. 2005

Stronger transmitted shock;

Weaker reflected shock;

Depress the HY instabilities;

Reducing the mixing of the cloud;

Evaporating the cloud material.

Without TC With TC

Results of models — X-ray emission:

Orlando et al. 2006, A&A, 457, 545

Two seperate high-emission regions in pure HY model;

HY instabilities are not clearly visible from X-ray emission.

What affects the efficiency of TC:

Orlando et al. 2008, ApJ, 678, 274; Orlando et al. 2010

Density contrast (between the cloud and surrounding medium);

Velocity of shock;

Magnetic field.

Analytic tools to know when TC is efficient:

Orlando et al. 2010; Miceli et al. 2006, A&A, 458, 213

When TC is efficient:

Tlow[DR]/Tlow[knot] > 1; emlow[DR]/emlow[knot] < 0.5.

the MPE vs CR plot is flatter.

ROSAT HRI

XA region, observed by XMM

the Cygnus Loop:

Zhou et al. 2010

Hard band emission gives the information of the distribution of ejecta;

The shock front is curved;

Central low MPE region indicates a “dense finger”;

The long strip indicates a large extension of the central “dense finger”;

Clumpy features in soft band map and the diffuse emission behind them in the medium band map;

Zhou et al. 2010

Spectral analysis:Abundance of shocked ISM is low;

Hot component in regions 4 and 9 mainly originate from ejecta;

Tejecta>TISM.

Fig.3

Zhou et al. 2010

The slope is flatter then the model without TC (~-0.45);

TC is less efficient in region 7&8;

The ascending trend in region 3&4 may caused by the presence of ejecta.

TC is predominant in all of the shock-cloud interaction regions.

Summary:

TC is important to understand the evolution of shock-cloud interaction;

In the XA region:

• The surrounding ISM is dense and clumpy;

• TC is prominent in all the shock-cloud interaction regions;

In addition:

• The abundances of the surrounding ISM are found to be lower than the solar value;

• A long bent “finger” protruding from the cavity wall is present in this region, which was not known before.

The End.

Thanks for your attention!!