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From: age@astro.noa.gr
Subject: EPIC EEF calculation
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3 replies: 1 2 3
1 followups: 1

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Notification:


Date: Mon, 21 Oct 2002 07:28:29 GMT
From: age@astro.noa.gr
To: xmmhelp@xmm.vilspa.esa.es
CC: age@astro.noa.gr
Subject: EPIC EEF  calculation
Full_Name: Antonis Georgakakis
Submission from: (NULL) (195.251.202.48)


Dear Sir/Madame,

I am trying to apply corrections for the encircled energy fraction (EEF) for XMM
EPIC sources at different off-axis angles. 

According to the XMM-SOC-CAL-TN-0018 document an analytic formulation has been
developed for the EEF of both the PN and the MOS1/2 detectors using King
profiles (documents EPIC-MCT-TN-011 and  EPIC-MCT-TN-012).

To caclulate the EEF  I use the parameters under the KING_PARAMS keyword  in 
the XRT1/2_XPSF_0005.CCF (for MOS1/2) and XRT_XPSF_0004.CCF  (for PN). My
understanding is that  the params in these tables are the core radius R_C and
index ALPHA of the King profile at different energies and off-axis angles. These
can then be plugged in equation (10) of EPIC-MCT-TN-011 document to get the EEF.

  
However, using the relations and parameters above I find little or no variation
of the EEF with off-axis angle. For  example for PN:
 
Energy : E=1.5keV
angle     :THETA=0arcmin 
I find from the table XRT_XPSF_0004.CCF 
core radius R_C=6.1785arcsec
index           ALPHA=1.5025.
Assuming a 20arcsec radius I find EEF=0.72

Using the same energy E=1.5kev and off-axis angle  THETA=10arcmin I find from
XRT_XPSF_0004.CCF 
R_C=4.328arcsec
ALPHA=1.3675
and hence EEF=0.71 within 20'' radius. 

Such a  small difference in the EEF between THETA=0 and 10arcmin does not agree
with (for example) Figure 5 (page 5) of XMM-CCF-REL-84 where the EEF at 1.5kev
and 20'' radius varies from 0.75 at 0' to 0.64 at 10'. 

I wonder whether I am doing smth wrong in my calculation  
or whether there is smth wrong in the tabulated R_C, ALPHA values.

thank you very much for your help, looking forward to your reply, 

Antonis Georgakakis

Reply 1

Resend
From: Rosario Gonzalez Riestra <xmmhelp@xmm.vilspa.esa.es>
To: age@astro.noa.gr
Subject: Re: EPIC EEF  calculation (PR#7320)
Date: Mon Oct 21 10:25:40 2002

Dear Dr.  Georgakakis,

I have forwarded your question to the EPIC Calibration Scientist. I'll let you
know as soon as I get his answer.

Best regards,


		Rosario Gonzalez-Riestra
		XMM-SOC User Support Group



Reply 2

Resend
From: Rosario Gonzalez Riestra <xmmhelp@xmm.vilspa.esa.es>
To: age@astro.noa.gr
Subject: Re: EPIC EEF  calculation (PR#7320)
Date: Mon Oct 28 09:07:32 2002
Dear Dr.  Georgakakis,


Please find below the answer from our experts about your question on the 
encircled energy fraction computation:


###############################
Your calculations are correct. There appears to be surprisingly little
change in the encircled energy fraction as you move off axis for all
of the cameras. Although the shape does distort and elongate beyong ~7
arcmins, the encircled fraction stays roughly constant.

The plot you refer to in XMM-CCF-REL-84 was generated from an early
calculation of the MOS-1 off-axis angle PSF relationship which was
documented in EPIC-MCT-TN-0008. These early numbers were superceded
in EPIC-MCT-TN-0011 where more sources were used to calculate the
theta dependency.
###################################################################


Regards,


			Rosario Gonzalez-Riestra
			XMM-SOC User Support Group


Followup 1

Compose reply
From: Antonis Georgakakis <age@astro.noa.gr>
To: Rosario Gonzalez Riestra <xmmhelp@xmm.vilspa.esa.es>
Subject: Re: EPIC EEF  calculation (PR#7320)
Date: Tue, 29 Oct 2002 14:47:21 +0200
Dear Rosario,

thank you for your email. Could you also tell me if SAS 5.3.3 tasks 
(eg eboxdetect and emldetect) also apply  the analytic EEF corections 
described in EPIC-MCT-TN-0011 or  whether they use a different 
correction, (eg the one parametrised by CONV, COR1 and COR2 keywords 
in XRT1_XENCIREN_003.CCF table)?


Thank you very much for your help,

regards, 

Antonis Georgakakis

**************************************************************
Dr. Antonis Georgakakis			Research Associate
National Athens Observatory		tel: (++30) 10 8109165
Institute of Astronomy & Astrophysics		fax:(++30) 10 8040453
I.Metaxa & Vas.Pavlou str.,			email: age@astro.noa.gr
Athens 15236,
Greece
**************************************************************



Reply 3

Resend
From: Rosario Gonzalez Riestra <xmmhelp@xmm.vilspa.esa.es>
To: age@astro.noa.gr
Subject: Re: EPIC EEF  calculation (PR#7320)
Date: Wed Oct 30 11:31:21 2002

Dear Antonis,

Please find below the answer to your question about the EEF and ebox/emlselect,
as provided by the tasks author. Hope it helps you.

Regards,


	Rosario

####################################################################

 
The detection tasks eboxdetect and emldetect read the eef information
from CAL file XRT3_XPSF_0004. In both cases CAL accuracy_level medium is set, 
i.e., the PSF (ray tracing) maps are used. In task eboxdetect the eef values are

accumulated from the PSF images read with by CAL call CAL_psfImage. In
emldetect, 
the eefs are obtainded using CAL call CAL_psfEncircledenergy. For the actual
PSF
fitting again the CAL cal CAL_psfImage, as in eboxdetect, is used. So, no, the
analytic eef corrections are not used.

#####################################################################


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