Astronomy & Astrophysics

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$\begin{figure} \par\includegraphics[angle=270,width=8.5cm,clip]{10534f1.ps}\end{figure}$ Figure 1: Hammer-Aitoff equal area projection in Galactic coordinates of the 3491 2XMM fields.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{10534f2.ps}\end{figure}$ Figure 2: Distribution of total good exposure time (after event filtering) for the observations included in the 2XMM catalogue (for each observation the maximum time of all three cameras per observation was used).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{10534f3.ps} \end{figure}$ Figure 3: Typical sky footprints of the different observing modes (the FOV is $\sim$ $30\hbox {$^\prime $ }$ ). Noticeable are the CCD gaps as well as columns and rows excluded in the filtering process. Top row: MOS full window mode; MOS partial window W3 or W5 mode; MOS partial window W2 or W4 mode. Bottom row: MOS fast uncompressed, fast compressed, or RFS mode; pn full window mode; pn large window mode.
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In the text

$\begin{figure} \par\includegraphics[width=17.5cm,clip]{10534f4a.ps} \end{figure}$ Figure 4: a) Examples of typical 2XMM EPIC images (north is up). From left to right: (i) medium bright point source; (ii) deep field observation; (iii) shallow field observation with small extended sources; (iv) distant galaxy cluster.
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In the text

$\begin{figure} \addtocounter{figure}{-1} \par\includegraphics[width=17.5cm,clip]{10534f4b.ps} \end{figure}$ Figure 4: b) Examples of variation in astrophysical content of 2XMM observations ( north is up); in most of these extreme cases the source detection is problematic. Top row, from left to right: (i) bright extended emission from a galaxy cluster; (ii) emission from a spiral galaxy which includes point sources and extended emission; (iii) very bright extended emission from a SNR; (iv) filamentary diffuse emission. Second row: (v) complex field near the Galactic Centre with diffuse and compact extended emission; (vi) two medium-sized galaxy clusters; (vii) complex field of a star cluster; (viii) bright point source, off-centre.
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In the text

$\begin{figure} \addtocounter{figure}{-1} \par\includegraphics[width=17.5cm,clip]{10534f4c.ps} \end{figure}$ Figure 4: c) Examples of instrumental artefacts causing spurious source detection ( north is up). From left to right: (i) bright source with pileup and OOT events; (ii) very bright point source showing obvious pileup, shadows from the mirror spider, and scattered light from the RGA; (iii) the PSF wings of a bright source spread beyond the unused central CCD causing a brightening of the edges on the surrounding CCDs (which may not be well represented in the background map); (iv) obvious noisy CCDs for MOS1 (CCD#4) and for MOS2 (CCD#5) to the top right; (v) numerous and bright single reflections from a bright point source outside the FOV, with a star cluster to the left. See Appendix A for terminology.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{10534f5.eps}\end{figure}$ Figure 5: A simplified schematic of the processing flow for EPIC image data. Early processing steps treat the data from each instrument and exposure separately. Source detection and parameterisation are performed simultaneously on one image from each energy band from each instrument. Source-specific products can be made, subsequently, from any suitable exposures in the observation. Observation-level, exposure-level and source-specific products are screened before archiving and use in making the catalogue.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{10534f6.ps} \end{figure}$ Figure 6: Examples of auto-extracted 2XMM spectra. Sources are serendipitous objects and spectra are taken from the EPIC pn unless otherwise stated. Panels: a) a typical extragalactic source (Seyfert I galaxy); b) line-rich spectrum of a localised region in the Tycho supernova remnant (target); c) MOS2 spectrum of a stellar coronal source (target; H II 1384, Briggs & Pye 2003), described by two-component thermal spectrum; d) spectrum of the hot intra-cluster gas in a galaxy cluster at z=0.29(Kotov et al. 2006); e) heavily absorbed, hard X-ray spectrum of the Galactic binary IGR J16318-4848 (target; Ibarra et al. 2007); f) spectrum of a super-soft source with oxygen line emission at $\sim$ 0.57 keV; g) a relatively faint source showing a two-component spectrum; h) source with power-law spectrum strongly attenuated at low energies and with a notable red-shifted iron line feature around 6 keV.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{10534f7.ps} \end{figure}$ Figure 7: Example auto-extracted 2XMM time-series. Sources are serendipitous objects and the data are taken from the pn unless otherwise stated. Panels: a) MOS1 data for Markarian 335 (Seyfert I - target); b) MOS1 data showing the decay curve of GRB 050326 (target); c) X-ray flares from a previously unknown coronally active star; d) time-series of the emission from a relatively faint cluster of galaxies, showing no significant variability (target); e) time-series of the obscured Galactic binary IGR 16318-4848 (target; Ibarra et al. 2007); f) previously unknown AM Her binary showing several phase-stable periodic features (Vogel et al. 2007); g) highly variable AND periodic object, likely to be a cataclysmic or X-ray binary (Farrell et al. 2008) - the binning results in poor sampling of the intrinsic periodic behaviour; h) source showing clear variability but not flagged as variable in the catalogue (the probability of variability falls below the threshold of 10^-5). These last two cases highlight the sensitivity of the variability characterisation on the time bin size.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{10534f8.ps} \end{figure}$ Figure 8: Sky area as a function of flux limit for the 2XMM catalogue computed for sources with a detection likelihood limit $L\ge 10$ in the respective energy band. Red curves are for MOS2; blue curves are for pn. (MOS1 is not shown but is very similar to MOS 2). Top panel: energy bands 1, 2, 3, 4, and 5 for each camera are shown with solid, long-dash, dash-dot, dotted, and dot-dot-dot-dashed line styles, respectively. Bottom panel: energy bands 6 and 7 for each camera are shown with solid and long-dash styles, respectively.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{10534f9.eps} \end{figure}$ Figure 9: Top: distribution of point source fluxes for the 2XMM catalogue in the soft (red), hard (blue), and total band (green) energy bands. The targets of the individual XMM-Newton observations are excluded from these distributions (see Sect. C.1). Detections selected for these distributions have likelihood $L\ge 10$ in the relevant bands. Only sources with summary flag 0 are included. Bottom: distribution of total EPIC counts for the same sample of 2XMM detections.The red histogram shows the distribution if the XMM-Newton targets are included.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=8.5cm,clip]{10534f10.ps} \end{figure}$ Figure 10: The number of false detections per field estimated via simulations for typical high Galactic latitude fields as a function of $L_{\rm min}$ for various exposure times. The red circles show the results for exposures of 12 ks for MOS and 8 ks for pn ( $\sim$ 70% of the median values), whereas the green squares and blue triangles show those with the exposures of 3 and 10 times higher respectively. The dotted line represents the theoretical false detection number assuming 5000 independent detection cells per field (see text).
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=7cm,clip]{10534f11a.ps}\par\... ...ace*{2mm} \includegraphics[angle=270,width=7cm,clip]{10534f11c.ps} \end{figure}$ Figure 11: Top: X-ray/optical position separation for each match for the corrected (solid histogram) and uncorrected (dashed histogram) XMM-Newton coordinates. Centre: distribution of separation sigma (x) for $\sigma _{\rm sys}=0$ . Bottom: distribution of separation sigma (x) for $\sigma_{\rm sys}=0\hbox{$.\!\!^{\prime\prime}$ }35$ . For the centre and bottom plots - histogram: separation sigmas; filled histogram: outliers with x >3.7 (and $\Delta r<10\hbox {$^{\prime \prime }$ }$ ); smooth curve: expected distribution N(x)normalised to fit the peak of the distribution.
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In the text

$\begin{figure} \par\includegraphics[width=6cm,angle=270]{10534f12a.ps}\includegr... ...0]{10534f12e.ps}\includegraphics[width=6cm,angle=270]{10534f12f.ps} \end{figure}$ Figure 12: Top row: EPIC pn X-ray hardness ratio density plots for high Galactic latitude ( $\vert b\vert>10^\circ$ ) 2XMM sample. Bottom row: X-ray hardness ratio density plots for low Galactic latitude ( $\vert b\vert<10^\circ$ ) 2XMM sample. Density is displayed on a logarithmic scale with a dynamic range of 100. The spectral tracks overlaid are for (i) power-law spectra with $\Gamma =1.9, 1.7, 1.4$ (blue) for the left, middle, and right panels, respectively; (ii) thermal spectrum (APEC model) with kT=0.3 keV (cyan; HR1-HR2 plot only); (iii) a composite thermal model with three components with kT=[0.3, 1, 3] keV (green). In each case hardness values are shown for $N_{\rm H}=[0.03, 0.4, 1, 5, 10, 50]\times 10^{22}\rm\ cm^{-2}$ (power-law model) and $N_{\rm H}=[0.01, 0.05, 0.1, 0.5, 1 ]\times 10^{22}\rm\ cm^{-2}$ (thermal models). For each spectral track the left-most point marked corresponds to the lowest $N_{\rm H}$ value, i.e. $N_{\rm H}$ increases towards the top right.
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In the text

$\begin{figure} \par\includegraphics[width=4.5cm,angle=270]{10534f13a.ps}\include... ...{10534f13b.ps}\includegraphics[width=4.5cm,angle=270]{10534f13c.ps} \end{figure}$ Figure 13: a) Frequency distribution of $P(\chi ^2)_{\rm EPIC}$ , with log scales on both axes: solid line - observed; dotted line - simulation for random noise, taking into account that there is not always a complete set of 3 camera values for each detection. b) Frequency distribution of $P(\chi ^2)_{\rm pn}$ , with log scales on both axes: solid line - observed; dotted line - simulation for random noise. c) As b) but with linear scales on both axes.
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In the text

$\begin{figure} \par\includegraphics[width=17.5cm,clip]{10534f14.ps} \end{figure}$ Figure 14: Examples of extended source detections. Green circles mark point source detections. In panels (i)-(vi) the magenta and yellow circles mark real and spurious extended detections respectively, plotted with their fitted extent (i.e., core radius, see Sect. 4.4.4). In panels (vii) and (viii) the yellow ellipses indicate the position of spurious extended source detections. Top row: (i) a compact extended source with a small core radius; (ii) a large, low surface brightness extended source at the edge of the FOV with low likelihood but high flux (see Fig. 15); (iii) an object with a point-like core detected both as a point source as well as an extended source; (iv) a clearly extended source with a spurious detection nearby (yellow circle) which is smaller and fainter (by a factor of 45) and which therefore does not significantly affect the parameters of the real source. Bottom row: (v) a SNR in the LMC where intrinsic structure is detected as point sources (note that the core radius is not representative as the extended emission does not follow the $\beta$ -model fitted); (vi) a bright extended source with multiple spurious detections around the centre: the core radii of these spurious detections are comparable to or greater than the extent of the real source and will thus significantly affect the parameters of the real source (note that the maximum core radius allowed in the fitting is $80\hbox {$^{\prime \prime }$ }$ ); (vii) a faint filamentary structure broken up into several extended detections where the parameters have little meaning (due to the circularly symmetric nature of the fit); (viii) a crowded region where several point sources are detected as extended due to source confusion (the algorithm is restricted to fitting at most two confused sources simultaneously).
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=8.5cm,clip]{10534f15.ps} \end{figure}$ Figure 15: Distribution of extent likelihood as a function of total-band EPIC flux for the extended source detections in the 2XMM catalogue. Red dots are potentially spurious detections with Flag 7 = T, yellow dots are detections with Flag 7 = F, black dots are the ``best'' sample detections with summary flag <2. Green stars mark the targets of the XMM-Newton observations classified as extended object types and blue squares targets which are object types classified as point-like. The vertical concentrations of target points at flux $\sim$ $3\times 10^{-11}$ and $\sim$ $2\times 10^{-10}\rm~erg~cm^{-2}~s^{-1}$ are real, being due to multiple detections of two different SNRs used as XMM-Newton calibration targets.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=8.5cm,clip]{10534f1.ps}\end{figure}$	Figure 1: Hammer-Aitoff equal area projection in Galactic coordinates of the 3491 2XMM fields.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{10534f2.ps}\end{figure}$	Figure 2: Distribution of total good exposure time (after event filtering) for the observations included in the 2XMM catalogue (for each observation the maximum time of all three cameras per observation was used).
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$\begin{figure} \par\includegraphics[width=17.5cm,clip]{10534f4a.ps} \end{figure}$	Figure 4: a) Examples of typical 2XMM EPIC images (north is up). From left to right: (i) medium bright point source; (ii) deep field observation; (iii) shallow field observation with small extended sources; (iv) distant galaxy cluster.
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