PowerPoint PresentationXRT Point Spread Function
Andy Read (amr30@star.le.ac.uk) EPIC BOC meeting Mallorca, 08/04/08
2-D PSFs – ‘MEDIUM’ mode – Images – fn(instr, E, theta, phi) – used in SAS source-searching (generated from SCISIM)
1-D PSFs –
‘EXTENDED’ mode – King profile (r0, alpha) – fn(instr, E, theta) – used in ARF generation/spectral fitting for circular, annular or box regions
also…
‘HIGH’ mode – 3-gaussian parametrisation of MEDIUM mode maps. Used in arfgen for irregular shapes or ellipses, etc. Problems with energy dependency
‘LOW’ mode – 1 gaussian, not used anywhere
CCF PSFs that are used in SAS:
XMM EPIC MOS
Andy Read (amr30@star.le.ac.uk) EPIC BOC meeting Mallorca, 08/04/08
2-D PSFs – ‘MEDIUM’ mode – Images – fn(instr, E, theta, phi) – used in SAS source-searching (generated from SCISIM)
CCF PSFs that are used in SAS:
Images for each instrument at various E and Off-axis angle – presently all SCISIM-generated, simple, and all the same for each instrument
XMM EPIC MOS
Andy Read (amr30@star.le.ac.uk) EPIC BOC meeting Mallorca, 08/04/08
2XMMp 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 (~200 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 (3) E-band (8) off-axis angle (6) - clean, BG-subtract stacked images, re-normalize, create CCF-like files
EPIC PSF : Determining the on- and off-axis 2-D PSF (last meeting)
Improvements in source-detection for bright on- and off-axis sources
Blue: current CCFs Green: New 2-D PSFs
Energy
XMM EPIC MOS
‘H’
Energy
‘H’
Energy
‘H’
Energy
H
Current CCF/AMR CCF
(i.e. if both CCF and AMR correct [or both equally wrong], should be ~1)
AMR values larger
Current CCF/AMR CCF
AMR values larger
GL says that AMR images working well/better than current CCF
H
Shape non-rotation is not just M2!
(just more obvious in M2)
All EPIC instruments behave in a similar way!
More later….
XMM EPIC MOS
XMM EPIC MOS
Use AMR-created azimuthally-stacked 2-D PSF real-data images (for each instrument, energy, off-axis angle)
Use CIAO-Sherpa to fit elliptical profile (beta2d) to images
Elliptical parameters (core radius, alpha, ellipticity), obtained for each instrument, energy, off-axis angle
CCF files produced (RDS) with new ELLBETA PSF CCF extension
Numbers/trends/problems currently being reviewed (improvements made… [see later])
To be used in arfgen…
New CCF PSF – ELLBETA – Elliptical parametrization of the 2-D PSF
XMM EPIC MOS
XMM EPIC MOS
New ELLBETA PSF in CCF
R0 α ell.
XMM EPIC MOS
Properties of ELLBETA elliptical parameters:
Variation of r0, alpha, ellipticity with energy and off-axis angle
MOS1 AMR-H PSF (2-D, real data)
(last meeting)
Properties of ELLBETA elliptical parameters:
Variation of r0, alpha, ellipticity with energy and off-axis angle
MOS2 AMR-G PSF (2-D, real data, [stretch-stacked])
(last meeting)
Properties of ELLBETA elliptical parameters:
Variation of r0, alpha, ellipticity with energy and off-axis angle
PN AMR-H PSF (2-D, real data)
(last meeting)
Re-stacking, cleaning and re-fitting leads to improvements and smoother functions at high-E, high-theta
Low- & medium-energy EE values look very sensible/consistent e.g.
EE at medium/high E should (theoretically) be higher than at low E
Still more refinements needed? EE too high at v.high E? Looking into this
Status
XMM EPIC MOS
The 2-D PSF
GX 339-4 (0204730301)
XMM EPIC MOS
The 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
XMM EPIC MOS
EPIC PSF : Determining the on- and off-axis 2-D PSF
Spokes in stacked images have been lost …
Energy
Andy Read (amr30@star.le.ac.uk) EPIC BOC meeting Mallorca, 08/04/08
In PA-corrected DET space, the spokes are not rotated, and keep the same orientation for all EPIC
16 main spokes 22.5° apart (360/16)
Offset of 11.25° (22.5/2)
i.e. Same effect as MOS2 ‘triangle’ – ‘shape’ is not rotated
XMM EPIC MOS
Andy Read (amr30@star.le.ac.uk) EPIC BOC meeting Mallorca, 08/04/08
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.
Also, some strange, very small misalignments…?
XMM EPIC MOS
Andy Read (amr30@star.le.ac.uk) EPIC BOC meeting Mallorca, 08/04/08
Dark lanes? Shadowing must be due to the electron deflector arms which mirror the spider and are mounted after the rear aperture.
Secondary spokes? Due to scattering at a small level from the sides of the spider legs.
XMM EPIC MOS
Meridional and Sagittal Plane
Sagittal plane:
Optical Axis
Field Point
Axis Point
Object Plane
Pupil Plane
Axis Ray
As you go off-axis the spokes in the tangential direction remain but those in the radial direction get fainter or disappear. As you go off-axis the X-rays are not coming from the full annular aperture of the mirrors. They are confined to the sagittal plane (tangential) rather than the meridional plane (radial). The spokes in the radial direction will disappear at a lower off-axis angle for the higher photon energies (because of the grazing angles).
Tangential
(Meridional)
Plane
Model :
XMM EPIC MOS
Model : (Ellipse plus spokes)
XMM EPIC MOS
List of variable parameters in ’07 model
Main ellipse [PA-rotated, PA-stretched]
Spokes [non-rotated, non-stretched, strength-filtered (PA-dependent)]
Ro, alpha, width (ellipticity), strength wrt main ellipse
Secondary spokes – same considerations, plus strength wrt primary spokes
Phi-dependence of strength (e.g. cosine-filtering? Plus S-M asymmetry)
But some/all of these parameters may vary w.r.t. e.g. Instr (e.g. M2), Energy, Theta, (Phi)… (plus also Source strength?...)
Is there constant spoke-to-main behaviour (and constant secondary spoke-to-primary spoke behaviour)?... Yes (last talk)
Some ‘fixed’ parameters?
However, no single specific example(s?) to fit model to…?
XMM EPIC MOS
Spoke-to-Core behaviour:
Source strength (Main peak intensity)?
Energy?
XMM EPIC MOS
Andy Read (amr30@star.le.ac.uk) EPIC BOC meeting Mallorca, 08/04/08
How to move forward? – I (older – last talk)
Can’t fill CCF with images for each Instr, Energy, Theta & Phi
Don’t have the images/stats to create all image PSFs (need several good, clean, bright, broad-E, non-piled-up sources at all detector positions)
CCF files would be Nphi (several 10’s) times larger than at present (& PSF CCF files are already very large indeed)
Could have CCF libraries of the 2 components: i.e. Main & Spokes
Main - Ro, alpha, ellipticity (fn: Instr, Energy, Theta, … Phi?)
Present MEDIUM CCF images, or better still, images created from new ELLBETA?
Spokes - Ro, alpha, width (ellipticity), strength wrt main ellipse (fn: ??)
New images (non-filtered?)
Retrieve (or create?) relevant Main & Spokes images
Need to PA-rotate Main and strength-filter Spokes (PA-dependant, plus asymmetric S-M), scale each, and combine.
XMM EPIC MOS
How to move forward? – II (simpler, newer – not best)
Stacked images in general work well in emldetect (GL)
Can model these images (and have done - ELLBETA)
Can create idealized images from these models (ellimage)
These however have a smeared azimuthal dependence (created from several sources at different azimuths) [sums to ~elllimage]
Need to (in CAL/CCF/emldetect):
choose the correct ellimage (instrument, off-axis angle, energy)
rotate the ellimage for the detector position of the source (and PA)
‘add in’ the azimuthal (spoke etc.) dependence (PA-dependant)
e.g. 1) add in a sum-to-zero spoke image
XMM EPIC MOS
Andy Read (amr30@star.le.ac.uk) EPIC BOC meeting Mallorca, 08/04/08
Procedure created to take an image (e.g. spokes, left) and convert this to an image such that the radial profile is zero – In each radial bin, the average value is subtracted from each individual pixel value
XMM EPIC MOS
Radial profiles:
XMM EPIC MOS
Stacked images in general work well in emldetect (GL)
Can model these images (and have done - ELLBETA)
Can create idealized images from these models (ellimage)
These however have a smeared azimuthal dependence (created from several sources at different azimuths) [sums to ~elllimage]
Need to (in CAL/CCF/emldetect):
choose the correct ellimage (instrument, off-axis angle, energy)
rotate the ellimage for the detector position of the source (and PA)
‘add in’ the azimuthal (spoke etc.) dependence (PA-dependant)
e.g. Filter the ellimage azimuthally, retaining overall profile, and including correct angles, offsets etc!
XMM EPIC MOS
XMM EPIC MOS
Filtering: cosine
Filtering: top hat
XMM EPIC MOS
Filtering: part top hat, part no filtering
XMM EPIC MOS
Filtering: Part triangular, part no filtering
XMM EPIC MOS
Flat-Topped Triangular Function
Estimated (from the data) widths of various components
Profile needs to be such that no change is introduced to the full (360°) radial profile – i.e. areas need to cancel out
This azimuthal function is now used
XMM EPIC MOS
General Azimuthal Dependency
Certain (sets of) MOS2 mirror shells are not perfectly circular?
XMM EPIC MOS
PN
MOS1
MOS2
MOS2
Θ = 0
45% of mean
XMM EPIC MOS
MOS2
Θ = 3
MOS2
Θ = 6
MOS2
Θ = 9
MOS2
Θ = 12
Effect still visible/constant, even though random off-axis stretching is present
XMM EPIC MOS
MOS2
Θ = 15
XMM EPIC MOS
MOS1
Θ = 0
MOS1
Θ = 3
MOS1
Θ = 6
Peaks coming in at 90° & 270°, due to stacked stretch effect. (MOS2 cosine effect shown for comparison)
XMM EPIC MOS
MOS1
Θ = 9
MOS1
Θ = 12
MOS1
Θ = 15
Very strong peaks at 90° & 270°, due to stacked stretch effect.
XMM EPIC MOS
PN
Θ = 15
Very strong peaks at 90° & 270°, due to stacked stretch effect.
XMM EPIC MOS
Energy
Example final PSFs : ‘Vela PSR’
Individual E-band (8) images formed from ELLBETA parameters – (rotated to correct source angle on detector) – azimuthally spoke-filtered using flat-topped triangular function (0.18/0.18) – images stacked, weighted by counts in particular E-bands – MOS2 image further cosine-filtered (45%, 50/170/290). (Something essentially the same would take place within emldetect/CAL)
MOS1
MOS2
Example final PSFs : ‘Vela PSR’
Relative normalizations by counts in particular E-bands :
Energy (keV)
Elliptical image created from ELLBETA parameters
Another example :
MOS2: image further cosine-filtered