Evaluation of the EPIC flux cross-calibration from 2XMM sources

1
Evaluation of the EPIC flux cross-calibrationfro
m 2XMM sources

• R. Saxton, S. Mateos, A. Read,
• S. Sembay

Mateos et al., 2009, AA, arXiv.0901.4026
2
2XMM sources
3
pn vs MOS1 energy dependence
Distributions of flux ratios fitted with Gaussian
profiles
MOS1 vs MOS2 energy dependence
4
pn vs MOS1energy dependence
pn / MOS agreement better than 3 in 0.2-0.5
keV band
10.2-0.5 keV 20.5-1 keV 31-2 keV 42-4.5
keV 54.5-12 keV
constant offset from MOS cameras of 7-9 from
0.5-4.5 keV
pn / MOS agreement worse above 4.5 keV (12.5)
5
MOS1 vs MOS2energy dependence
10.2-0.5 keV 20.5-1 keV 31-2 keV 42-4.5
keV 54.5-12 keV
MOS cameras agree to better than 4 at all
energies
6
pn vs MOS1time dependence
MOS to pn flux cross-calibration constant gt0.5
keV strong dependence on time lt0.5
keV evolution of the MOS RMF with time
7
MOS1 vs MOS2 time dependence
MOS flux cross-calibration constant at all
energies
8
pn vs MOS1offaxis dependence
10.2-0.5 keV 20.5-1 keV 31-2 keV 42-4.5
keV 54.5-12 keV

• Variations of MOS vs pn relative flux calibration
  vs offaxis
• ARF effect
• QE spatial variation in QE offaxis (MOS and pn)
• Vignetting General vignetting function
• PSF Uncertainties in offaxis PSF

9
MOS1 vs MOS2offaxis dependence
10.2-0.5 keV 20.5-1 keV 31-2 keV 42-4.5
keV 54.5-12 keV

• Variations of MOS relative flux calibration vs
  offaxis
• ARF effect
• QE spatial variation in QE offaxis (MOS and pn)
• Vignetting General vignetting function
• PSF Uncertainties in offaxis PSF

10
Azimuthal dependence - PN v MOS-2
1
4
2
4
1
3
10.2-0.5 keV 20.5-1 keV 31-2 keV 42-4.5
keV 54.5-12 keV
3
2
Strong azimuthal-angle dependence at high
energies
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RGA obscuration Azimuthal dependence
Excluded sources at offaxislt2 arcmin
B-4
B-4
1
4
B-4
B-4
B-4
2
4
1
3
B-5
B-5
10.2-0.5 keV 20.5-1 keV 31-2 keV 42-4.5
keV 54.5-12 keV
Sources divided in 4 azimuthal angle bins based
on DETX/DETY coordinates
3
2
Strong azimuthal angle dependence at high
energies Sources lying along the RGA dispersion
axis show a large gradient in relative flux
Calibration of RGA blocking factor incorrect at
high energies?
12
RGA obscuration Azimuthal depencence
Excluded sources at offaxis lt2 arcmin
1
4
B-5
B-4
B-4
B-4
2
4
1
3
B-5
B-4
B-5
10.2-0.5 keV 20.5-1 keV 31-2 keV 42-4.5
keV 54.5-12 keV
Sources divided in 4 azimuthal angle bins based
on DETX/DETY coordinates
3
2
Strong azimuthal angle dependence at high
energies Sources lying along the RGA dispersion
axis show a large gradient in relative flux
Calibration of RGA blocking factor incorrect at
high energies?
13
Current azimuthal vignetting factor for MOS-1
1.5 keV _at_ 9 amin offax
9 keV _at_ 9 amin offax
14
Low-energy azimuthal dependence MOS-1
Excluded sources at offaxislt 2arcmin
1
4
B-5
B-4
B-4
B-4
2
4
1
3
B-5
B-4
B-5
10.2-0.5 keV 20.5-1 keV 31-2 keV 42-4.5
keV 54.5-12 keV
Sources divided in 4 azimuthal angle bins based
on DETX/DETY coordinates
3
2
Strong azimuthal angle dependence at low
energies Sources lying on CCDs from different
batches show a large gradient in relative flux

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Low-energy azimuthal dependence MOS-2
Excluded sources at offaxislt2 arcmin
B-4
B-4
1
4
B-4
B-4
B-4
2
4
1
3
B-5
B-5
10.2-0.5 keV 20.5-1 keV 31-2 keV 42-4.5
keV 54.5-12 keV
Sources divided in 4 azimuthal angle bins based
on DETX/DETY coordinates
3
2
Smallish azimuthal angle dependence at low
energies. Batch effect not so strong here ?
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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
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Conclusions

• Excellent agreement of the two MOS cameras (lt4)
  at all energies
• MOS cameras register
• 7-9 higher flux than pn below 4.5 keV
• 10-13 flux excess at the highest energies
• No evolution of flux ratios with time except in
  the 0.2-0.5 keV band
• Gradual degrading of the MOS redistribution
  function
• MOS to pn excess increases with offaxis ARF
  effect
• Strong dependency of MOS to pn excess 4.5-12 keV
  flux on azimuthal-angle

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TO DO

• Fudge RGA obscuration to give larger azimuthal
  effect for MOSs at high energies ? Use SCISIM
  to justify physical parameters ?
• Put in a batch-specific, low-energy QE
  contribution for MOS-CCDs ?
• 2XMM could benefit from
• - MOS RMFs made spatially, temporally
  dependent.
• - EBG PSF ?
• - Spectral dependence in flux calculation
• Strong dependency of MOS to pn excess 4.5-12 keV
  flux on azimuthal-angle
• Calibration of RGA blocking factor (RGA
  absorption) incorrect at high energies?