XMM-Newton 1 D Lumb -- SCI-ST. EPIC TTD Nov01 EPIC Background Template Files Why we need them -...
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Transcript of XMM-Newton 1 D Lumb -- SCI-ST. EPIC TTD Nov01 EPIC Background Template Files Why we need them -...
![Page 1: XMM-Newton 1 D Lumb -- SCI-ST. EPIC TTD Nov01 EPIC Background Template Files Why we need them - previous attempts insufficient Adding together high galactic.](https://reader031.fdocuments.net/reader031/viewer/2022033101/56649d805503460f94a63c2c/html5/thumbnails/1.jpg)
XMM-Newton
1
D Lumb -- SCI-ST. EPIC TTD Nov01
EPIC Background Template Files
• Why we need them - previous attempts insufficient
• Adding together high galactic latitude files - choices & screening
• Comments on the internal background in MOS
• Using the files astrophysically - seem consistent with ROSAT/ASCA and other historic data
• Future developments - SAS task needed ?
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XMM-Newton
2
D Lumb -- SCI-ST. EPIC TTD Nov01
Context
• Extended objects are an important field of XMM science
• Background surface brightness relatively high and variable need a good estimate of background which does not rely on the in-field subtraction
• “Band-aid” background files provided for A&A special issue analysis (using Lockman Hole and selected calibration fields)
• S:N too low, heterogeneous field selection (NH, filters), also the exposure corrections uncertain for use
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XMM-Newton
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D Lumb -- SCI-ST. EPIC TTD Nov01
Field Choice & Locations
• Chose all THIN filter (most extended objects use THIN & easier to make a change for other filters if homogeneous data set has been employed)
• High galactic latitude away from any obvious features in the halo or near bright point sources
• Low proton background, low NH, long observations from calibration, PV or SOC data sets where possible to minimise data rights issues
• If a typical GO observation is ~30ksecs, then aim for 10 times this for a reasonable signal:noise
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XMM-Newton
4
D Lumb -- SCI-ST. EPIC TTD Nov01
Field Locations (contd.)RA Dec Date Time N_H L II BII
2000 (ks) (1020)
02:18:00 -05:00:00 2000-07-31 60 2.5 169.7 -59.8
02:19:36 -05:00:00 2000-08-04 60 2.55 170.35 -59.5
02:25:20 -05:10:00 2001-07-03 25 2.7 172.3 -58.6
02:28:00 -05:10:00 2001-07-06 25 2.7 173.5 -58.2
10:52:44 +57:28:59 2000-04-29 70 0.56 149.3 53.1
12:36:57 +62:13:30 2001-06-01 90 1.5 125.9 54.8
13:34:37 +37:54:44 2001-06-23 80 0.83 85.6 75.9
22:15:31 -17:44:05 2000-11-18 55 2.3 39.3 -52.9
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XMM-Newton
5
D Lumb -- SCI-ST. EPIC TTD Nov01
Source Extraction
• Need to remove bright sources, but as lots of the XMM background normally gets resolved, we cannot remove ALL or it is not representative for the observer’s field!
• By co-adding several fields there is some dilution effect, and as long as it is OK on ~arcminute levels and << 10-14 ergs source level, it will probably cover most eventualities
• Avoid arbitrary manual removal, so used EBOXDETECT (0.5-2keV, local mode only), noting ~ 10 brightest locations and excise from 50 arcsec diameter (>~80% flux each)
• Based on LogN-LogS this cut must be ~1.5 x 10-14 ergs, which after dilution >5 means only very faint effective residual (confirm by manual inspection) point source content
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XMM-Newton
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D Lumb -- SCI-ST. EPIC TTD Nov01
File Creation
• Screening of proton flares (PI>10000&&PATTERN==0) at 4in 100 sec time bins (if screening is too tight may not match observers’ cuts)
• Concatenate the event list in time, apply exposure extensions from original files (also concatenated), badpix, offset, GTI extensions left in
• Hide identity of original fields , modify keywords to be homogenous and consistent (START, STOP, FRACEXP, LIVETIME etc.)
• Basic duration now >400ksec, but observer might consider further screening to match own data set which now should be possible as extensions are coherent (I think that 350ksec is closer to usable quiet duration)
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XMM-Newton
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D Lumb -- SCI-ST. EPIC TTD Nov01
What does it look like?
• DETX,DETY coords, MOS1 & PN (E>250eV)
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XMM-Newton
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D Lumb -- SCI-ST. EPIC TTD Nov01
MOS Al & Si
• Al weaker around edge of centre CCD, Si is reverse
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XMM-Newton
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D Lumb -- SCI-ST. EPIC TTD Nov01
PN Cu & Soft band
• Metal emission lines with central hole
• Soft band dominated by streaks
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XMM-Newton
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D Lumb -- SCI-ST. EPIC TTD Nov01
MOS Internal Background
• Can use the substantial area outside filter to determine the true internal background component
• Flat spectrum above 1keV, count rate consistent with CR rate and 99.5% rejection
• Steeply rising low energy background – worse in MOS2 than MOS1 – correlated with the bad and flickering pixels?
• Al and Si emission lines variable so cannot use as simple subtraction for an IN-FIELD. Choose a model of several Gaussians and broken power law
• Use this as a “background” component for in-field but change normalisations according to surface area, but allow emission line intensities to be free parameter
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XMM-Newton
11
D Lumb -- SCI-ST. EPIC TTD Nov01
MOS Internal Background
Al
Si & AuCr, Mn Fe
Au
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XMM-Newton
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D Lumb -- SCI-ST. EPIC TTD Nov01
Astrophysical Analysis
• With a high signal:noise and reasonable internal background characterisation we can attempt astrophysical analysis.
• Produce focal plane vignetting averaged response file and fit MOS1 & MOS2 simultaneously
• Extragalactic power law seems consistent (harder than 1.4 unless the bright sources put back in) – but careful analysis of the out of field scattered component and the cosmic variance to brighter sources may allow a resolution to the long-standing background normalisation problem
• Soft component temperature models are consistent with Kuntz&Snowden analysis, but the LHB components poorly constrained (calibration problems)
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XMM-Newton
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D Lumb -- SCI-ST. EPIC TTD Nov01
Future Development
• Could produce further additions for deeper fields?
• Need to fix for filters and galactic location, possibly even CR variations:
• A task can be envisaged
1) Takes the model for internal component scaled by CR rate proxy
2) Produce soft component based on ROSAT multi-band analysis for the appropriate LII & BII (Steve Snowden working on tool)
3) Filter choice then added through the appropriate response matrix
4) Proton screening still a problem?