Astronomy & Astrophysics

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$\begin{figure} \par\includegraphics[angle=90,width=13.5cm,clip]{Hh172_f1CMJN.eps} \end{figure}$ Figure 1: The left panel shows the EPIC/MOS image of the inner Geminga field. Data from MOS1 and MOS2 cameras have been combined. The presence of two Tails of diffuse emission, aligned with the pulsar proper motion direction (marked by the arrow), is apparent. The right panel shows the unfolded spectrum of the diffuse Tails ( lower plot) compared to the Geminga pulsar unfolded spectrum ( upper plot). To describe the pulsar spectrum we used a double-component model (Caraveo et al. 2004), encompassing a blackbody ( $T\sim 5\times 10^5$ K, green curve), representing thermal emission from the star surface, as well as a power law (photon index $1.7\pm 0.1$ , blue curve), representing non-thermal emission originating in the pulsar magnetosphere. The tails' spectrum is well described by a hard power law (see text).
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In the text

$\begin{figure} \par { \includegraphics[width=8cm,angle=90]{Hh172_f2a.eps}\includegraphics[height=8cm,angle=0]{Hh172_f2b.eps} } \end{figure}$ Figure 2: The ACIS image (0.45-7 keV, 0.492'' pixel size), zoomed on the Geminga pulsar position, is shown in the left panel. In the middle panel, the same image, rebinned to a pixel size of 2'', has been superimposed on the XMM-Newton/MOS smoothed image. Surface brightness contours for the XMM image have been also plotted. The pulsar proper motion direction is marked by an arrow. The ACIS field of view is marked by the white rectangular box. The black box identifies an identical $1'\times 1'$ region in all panels. In the right panel, the ACIS images in the 0.45-0.8 keV and 0.8-7 keV ranges are shown. While the Chandra Trail is virtually invisible in the softer band, it appears very clearly at higher energy, pointing towards a hard spectral shape.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.3cm,clip]{Hh172_f3.eps} \end{figure}$ Figure 3: Brightness profile of the diffuse Chandra Trail, computed along the pulsar proper motion direction. Each bin contains the counts detected in a $7''\times 3''$ rectangular box, as shown in the inset. The region represented in the inset is the same marked by the black box in Fig. 2.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.3cm,clip]{Hh172_f3.eps} \end{figure}$	Figure 3: Brightness profile of the diffuse Chandra Trail, computed along the pulsar proper motion direction. Each bin contains the counts detected in a $7''\times 3''$ rectangular box, as shown in the inset. The region represented in the inset is the same marked by the black box in Fig. 2.
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