The XRT Point Spread Function Andy Read

1. The XRT Point Spread Function Andy Read

2. The XRT Point Spread Function Andy Read Updates from previous BOC meeting New developments, remodellings, central peaks, EBG, triangles & pentagons Migrating into CAL & SAS: CCF, arfgen et al, - The Full 2-D PSF First tests in SAS & CAL

3. EPIC PSF : Determining the on- and off-axis 2-D PSF • 2XMM source list - select M1, M2, PN point sources that have large numbers of counts, are below pile-up limit, cover full range in off-axis angle (>250 obs) – create calibrated event lists • Clean event files (high-BG, out-FOV etc.), extract source, reject bad fields, create source images (all E-bands, all instruments), subtract other sources, detector-rotate, Gaussian re-centre • Stack good images together for each instrument (pn, M1, M2), E-band, off-axis angle - clean, BG-subtract stacked images, re-normalize, create CCF-like files PN Energy Off-axis angle Improvements in source-detection for bright on- and off-axis sources Blue: current CCFs Green: New 2-D PSFs

4. EPIC PSF : Determining the on- and off-axis 2-D PSF PN Energy Off-axis angle Spoke non-rotation means that spokes in theta-phi-corrected stacked images are smeared out and averaged. These images can be used to parametrize the average PSF model.

5. New CCF PSF – ‘EBG - EllBetaGauss’ – Elliptical (Beta) plus central Gaussian parametrization of the 2-D PSF • Use AMR-created azimuthally-stacked 2-D PSF real-data images (for each instrument, energy, off-axis angle)‏ • Use CIAO-Sherpa to fit elliptical + Gaussian profile (beta2d + gauss2d) to images (central Gaussian to model core)‏ • Elliptical (core radius, alpha, ellipticity [tied]) and Gaussian (FWHM, ellipticity [tied]), plus relative (G/E) normalization, obtained for each instrument, energy, off-axis angle • CCF files have been produced (RDS) with new EBG PSF CCF extension • Numbers/trends/problems currently being reviewed (improvements have been [and will be] made…)‏ • Can be used in arfgen...

6. Central Gaussian needed to model just the very centre Example : MOS2 - Rev 301 (MCG-06-30-15)‏ 0.225 keV King fit

7. Central Gaussian needed to model just the very centre Example : MOS2 - Rev 301 (MCG-06-30-15)‏ 0.225 keV King + Gaussian fit Note normalization ratio ~20% Note Gaussian is narrow

8. Central Gaussian needed only for MOS and at low & medium energies PSF King+Gaussian 1-D Fitting • Ratio of normalizations [Gauss/King] versus Energy • M1/M2 : Significant Gauss component required, at low/medium-E – [no Gauss component required at high-E] • PN : No significant Gauss component required

9. ‘EBG’ Elliptical (Beta) + central Gaussian

10. Calculated Enclosed Energies at various energies and off-axis angles for 20´´ and 40´´ circles from the EBG CCF parameters • MOS1 20´´ 40´´

11. Calculated Enclosed Energies at various energies and off-axis angles for 20´´ and 40´´ circles from the EBG CCF parameters • MOS2 20´´ 40´´

12. Calculated Enclosed Energies at various energies and off-axis angles for 20´´ and 40´´ circles from the EBG CCF parameters • PN 20´´ 40´´

13. Status – EBG Parametrization • First good set of model parameters (core radius [E], slope [E], ellipticity [E&G], FWHM [G], normalization ratio [G/E]) estimated for each EPIC instrument (3), off-axis angle (6) and energy (8)‏ • First CCFs (M1, M2, pn) have been created (AMR -> RDS)‏ • CAL software/calls essentially completed – calls need to be included in SAS tasks • arfgen able to work with optimally-selected elliptical regions, and with EBG parameterization (RDS)‏ • First tests of arfgen usage, enclosed energies obtained, fluxes obtained - all in progress • Hopefully full EBG system by next major SAS release

14. EBG Parameters in CCF Files

15. 1st study of 24 off-axis point sources (M. Guainazzi, R. Saxton, M. Stuhlinger)‏ Comparing flux ratios in several energy bands: New/Old New: via (optimum) elliptical spectral extraction (new eregionanlyse), using new arfgen and new EBG PSF Old: via circular spectral extraction, using arfgen and old EXTENDED PSF MOS1

16. Both MOSs show zero to very small flux decreases over soft to medium-hard energy ranges. 7-9% decreases are seen in the hardest energy range (4-10 keV)‏ MOS2

17. pn shows very small flux increases over soft to medium-hard energy ranges. 5% decrease is seen in the hardest energy range (4-10 keV)‏ pn

18. Consistent improvements in the MOS2/pn flux ratio, with some evidence for similar improvements for MOS1/pn Large scatter, low stats at very lowest energy so far (See RDS BOC talk for details on M09 paper)‏

19. The Full 2-D PSF The star-like pattern – the ‘spokes’ – is created by the spider which supports the 58 co-axial Wolter I mirrors of the telescope

20. Observed spokes are actually due to the gaps between the spider legs, not the legs themselves, which are coincident with the secondary spikes and the dark lanes. Without the spider you would see uniform scattering wings without the radial gaps.

21. Secondary spokes? Due to scattering at a small level from the sides of the spider legs. Dark lanes? Shadowing must be due to the electron deflector arms which mirror the spider and are mounted after the rear aperture.

22. In (PA-corrected) space, the spokes are not rotated, as the source moves about on the detector i.e. anywhere on the detector(s), the source spokes keep the same orientations for all EPIC 16 main spokes 22.5° apart (360/16)‏ Offset of 11.25° (22.5/2)‏ General well-known tangential ‘sagittal-plane’ stretching rotates with the source around the detector Spokes and other (to be seen later) components do not rotate around the detector The PSF of a source at a particular azimuth is not merely a simple rotation of the same source at a different azimuth – Each point on each EPIC detector has a unique PSF

23. In an observation, though all the sources are tangentially distorted at different angles, the spokes from all the bright sources line up

24. From EBG to the Full 2-D PSF • Stacked images in general work well in emldetect • Can model these images (and have done - EBG)‏ • Can create idealized images from these models (EBG image, example shown right) • These however have a smeared azimuthal dependence (created from several sources at different azimuths)‏ • Need to (in CAL/CCF/emldetect): • choose/create the correct EBG image (instrument, off-axis angle, energy)‏ • rotate the EBG image for the detector position of the source • ‘factor in’ the known azimuthal (spokes etc.) dependence i.e. filter the EBG image azimuthally, retaining overall profile, and including correct angles, offsets, spoke sizes etc • Finally, filter in (via similar method) any gross azimuthal filtering (e.g. the MOS2 ‘triangle’)

25. Flat-Topped Triangular Function 22.5° spoke spoke 2 H = – 1 2X + Y X 0.18 H Y 1.00 Profile needs to be such that no change is introduced to the full (360°) radial profile – i.e. areas need to cancel out 0.18 1.00 Estimated (from the data) widths of various components

27. Look at the gross azimuthal properties... e.g. The MOS2 ‘triangle’ Certain (sets of) MOS2 mirror shells are not perfectly circular It is a ‘mirror effect’, like the spokes, and does not rotate with position on the detector

28. MOS2 Θ = 0´ 45% of mean Strong effect! (45%)‏ 3-peaked cosine function fits well (peaks at 50°, 170°, 290°)

29. MOS1 13% of mean Much weaker (~13%) 5-peaked pentagon function (cosine)‏ (62°, 134°, 206°, 278°, 350°)

30. PN Nothing seen (yet) in pn

31. Point Spread Function: Six stages towards a full 2-D PSF EBG MOS1 MOS2 [1] Ell. PSF at given off-ax angle/energy [2] Central Gauss peak (off-ax/en) [3] Combine 1+2 [4] Rotate to correct source PA [5] Az-filter spoke structure [6] Az-filter gross azimuthals

32. Energy M1 Off-axis angle

33. Energy M2 Off-axis angle

34. Energy PN Off-axis angle

35. Status – Full 2-D PSF • Uses EBG parameterization as seed – hence needs EBG system & CAL to be already in place – it is • Requires very large software migration and updates to CAL (completed) & SAS/emldetect (first stages)‏ • First pieces of software (IDL) sent (late 08) to RDS – First full set of code sent early 09 – First SAS/CCF version appearing ~now (e.g. calview/psfgen can create full 2-D PSF)‏ • Only when in place can any sensible testing be started (source-detection, source parameterization etc. – SSC/SOC to perform testing)‏ • If no major problems, may have a first beta version in place by next major SAS release – but, some problems...

36. Full 2-D PSF – some initial problems...

37. Full 2-D PSF – ...now looking good AMR CAL AMR/CAL

38. Full 2-D PSF – ...now looking good AMR CAL AMR/CAL • Moiré-like interference pattern actually in AMR image

39. Full 2-D PSF – ...now looking good • Full 2-D PSF now in CAL – accessible via e.g. calview

41. Full 2-D PSF – Testing... • Georg/AIP to incorporate into emldetect and perform testing – idea is to make ELLBETA (EBG) PSF an option in emldetect, with the default still set to MEDIUM • SSC to test emldetect with ELLBETA over many fields (all types – normal, crowded, problem fields) – compare results • Continuing spectral tests (ESAC) of bright off-axis (and on-axis) sources with arfgen and ELLBETA • Rigorous spectral analysis of bright sources using complex models and various extraction 'radii' • (Future) Re-stacking, re-modelling of more data to obtain better EBG parameters – update CCFs – especially at high-energies...

42. Full 2-D PSF – The Far Future... • MOS events spread across the RGS dispersion axis – Is this a PSF issue? • Out-of-time events? Is this a PSF issue? • Some proper handling of the Sagittal-Meridional effect (off-axis and energy dependent)‏ • Azimuthal phi-dependence of the EBG parameters? e.g. RGA obscuration, individual chip-to-chip height variations • Pentagon in pn? • Dark lanes – electron deflector? • ...

43. End