The XMM-Newton Slew SurveyThe XMM-Newton Slew Survey

Richard Saxton, M. Pilar Esquej Richard Saxton, M. Pilar Esquej

Michael Freyberg, Bruno Altieri Michael Freyberg, Bruno Altieri

Andrew ReadAndrew Read

OverviewOverview- 390 slew datasets in archive- 390 slew datasets in archive- PN, MOS-1/2 exposures in Medium filter with the observing mode set to that of - PN, MOS-1/2 exposures in Medium filter with the observing mode set to that of

previous pointed observationprevious pointed observation- Average slew length is 70 degrees- Average slew length is 70 degrees- Data available for slews > 30 mins- Data available for slews > 30 mins- Closed slew, open slew, closed slew. Open slew speed = 90 degrees / hour, i.e. - Closed slew, open slew, closed slew. Open slew speed = 90 degrees / hour, i.e.

on-source time <~14 secson-source time <~14 secs- Area covered to date ~8000 deg- Area covered to date ~8000 deg2 2 (~20% of sky)(~20% of sky)

Pilot study 1:Pilot study 1:

SAS worked fine after small OAL change.

Tangential projection not valid over whole slew. Long slews need to be subdivided to maintain astrometry.

Divide slew into 1 deg2 imagesand recalculate sky positions

Source search using near-standard pipeline eboxdetect/emldetect combination tuned for ~zero background.

Process 9 slews, source searching Process 9 slews, source searching single 0.2-15 keVsingle 0.2-15 keV image image (flag=0, pattern<=4), (flag=0, pattern<=4), flat exposure mapflat exposure map

To check if slew data scientifically usefulTo check if slew data scientifically useful

Initial impressionsInitial impressions

Source extended into a 4 arcmin streak due to 2.6 second frame time

Full frame (73ms) mode streak = 6 arcsecs – not a problem

Extra pn sensitivity + additional MOS background means little to be gained from analysing MOS slews

Epic-pn attitude reconstruction very good

MOS PN PN (eFF)

Extended full frame (200ms)streak of 18 arcsecs

Slew direction

Optical Loading AssessmentOptical Loading Assessment

~10% sources coincident with bright stars - Optical loading or genuine X-ray sources?- Could be an issue but not dominant

DSS images of 139 pilot#1 slew positions DSS on slew positions + 1hour RA

Spurious Sources…Spurious Sources…

… due to crab off-axis !Sources 1 & 3 of Pilot#1

Pilot Study 1: SummaryPilot Study 1: Summary

Source searched images from 9 pn slews and found 139 sources down to det_ml=10, ~0.5 source/deg2

IdentificationsIdentifications

Total sources = 139Total sources = 139ROSAT survey IDs = 63ROSAT survey IDs = 63Bright stars (optical loading?), detector flashes, Crab off-axis & Bright stars (optical loading?), detector flashes, Crab off-axis &

spurions + 1 source observed twice in separate slews leave…spurions + 1 source observed twice in separate slews leave…

~50 unidentified~50 unidentified

Extended source analysisExtended source analysisSource 2: 2x2 arcmin

FF mode point sources are fitted well by a PSF, e.g. source 4

Pilot#1 sources - 5x5 arcmin images

Enough counts to detect extension in brightest sources

Abell 3581Abell 3581

Easily detected as extended in <~14 second exposure

(EFF mode)

Slew direction

Conclusions from pilot 1Conclusions from pilot 1

- MOS slew data effectively useless- ~10% of sources coincident with bright stars - optical loading?- Expect to find ~ 4,000 sources from current data- Sensitive to extension in brighter sources

New operations strategy (now in place):New operations strategy (now in place):

MOS slews used for calibrationMOS slews used for calibration All PN slews larger than 15 minutes down-linked and All PN slews larger than 15 minutes down-linked and

processedprocessed Medium filter if FF,eFF,LW and Closed for other modesMedium filter if FF,eFF,LW and Closed for other modes

Pilot study 2:Pilot study 2:

Three long slews ~ 110 degrees, 1 each of FF, EFF and LW modesThree long slews ~ 110 degrees, 1 each of FF, EFF and LW modes 3 source-searching strategies investigated3 source-searching strategies investigated

A) 1XMM scheme - separate 0.2-0.5, 0.5-1.0, 1.0-2.0 and 2.0-12.0 keV A) 1XMM scheme - separate 0.2-0.5, 0.5-1.0, 1.0-2.0 and 2.0-12.0 keV images – images – 23 detections23 detections (mean of 14.4 counts) (mean of 14.4 counts)

B) Search single 0.2-12 keV, pattern<=4 image – B) Search single 0.2-12 keV, pattern<=4 image – 110 detections, 110 detections, many many spuriousspurious

C) Search 0.2-0.5 (pattern 0) + 0.5-12.0 (patt <=4), single image - C) Search 0.2-0.5 (pattern 0) + 0.5-12.0 (patt <=4), single image - 64 64 detectionsdetections (mean of 8.6 counts) (mean of 8.6 counts)

Best results from scheme C:Best results from scheme C: we lose band-specific count rates and hardness we lose band-specific count rates and hardness ratios but can calculate these ratios but can calculate these a posterioria posteriori with eregionanalyse on individual with eregionanalyse on individual images. images.

Also almost all spurious detector features removed (using only singles in very Also almost all spurious detector features removed (using only singles in very softest band)softest band)

To investigate optimum processing and source search strategy

Usage of Exposure MapsUsage of Exposure Maps

Slew searched using variable exposure maps and detector mask – no unusual effects.

Next to last degree of slew

Final degree of slew

Uneven exposure at end of slew due to closed-loop.

Conclusions from pilot 2Conclusions from pilot 2

- Source density again Source density again ~0.5 / deg²~0.5 / deg²

- Use full-band image: 0.2-0.5 (patt=0) + 0.5-12.0 keV (patt<=4) & soft-band (~ROSAT) image: 0.2-0.5 (patt=0) + 0.5-2.0 keV (patt<=4) & hard-band image: 2.0-12.0 keV (patt<=4) i.e. 3 Surveys

- Use exposure maps and detector masks- Find individual sub-band count rates after source search- Only use FF, EFF and LW mode data- For uniform survey can apply an exposure threshold

The XMM Slew Survey : The XMM Slew Survey : current processing schemecurrent processing scheme

- Processing of slew data (creation of event files) - Processing of slew data (creation of event files)

- Creation of images, exposure maps (full-, soft- and hard-band)- Creation of images, exposure maps (full-, soft- and hard-band)

- Source search full-, soft- and hard-band images using exposure maps - Source search full-, soft- and hard-band images using exposure maps

- Make catalogue of detections - Make catalogue of detections

- Make DSS images for each detection - Make DSS images for each detection

- Check for and flag spurious sources - Check for and flag spurious sources

- Check for and flag optical loading due to bright stars - Check for and flag optical loading due to bright stars

- Find hardness ratios from individual band images - Find hardness ratios from individual band images

- Make clean catalogue of sources - Make clean catalogue of sources

- Cross-correlate with Rosat - Cross-correlate with Rosat

- Cross-correlate with other catalogues- Cross-correlate with other catalogues

(In preparation…) (In preparation…)

- Analyse extensions - Analyse extensions

- Co-add slews and re-search - Co-add slews and re-search

- Optical follow-up…- Optical follow-up…

Current StatusCurrent Status- Initial processing and event file - Initial processing and event file

creation for all available Slewscreation for all available Slews- 374 Slews: 297 of which are - 374 Slews: 297 of which are FF (206), eFF (61) or LW (30)FF (206), eFF (61) or LW (30)

- 54 Slews: Images & exposure maps - 54 Slews: Images & exposure maps created & source-searched created & source-searched (31 FF, 19 eFF, 4 LW)(31 FF, 19 eFF, 4 LW)

- Slew catalogue frozen (01/04/05)- Slew catalogue frozen (01/04/05)

- 780 sources in total (0.2-12.0 keV) band- 780 sources in total (0.2-12.0 keV) band- 645 sources in soft (0.2-2.0 keV) band- 645 sources in soft (0.2-2.0 keV) band- 96 sources in hard (2.0-12.0 keV) band- 96 sources in hard (2.0-12.0 keV) band

- At faint end, - 68 soft-band sources, not detected in the total band- At faint end, - 68 soft-band sources, not detected in the total band - 20 hard-band sources, not detected in the total band- 20 hard-band sources, not detected in the total band

- Total of 868 sources in ~1800 deg- Total of 868 sources in ~1800 deg² ² ~0.5 sources per square degree~0.5 sources per square degree

Currentlysearched

slews

Current Problems Current Problems

- Processing problems affect ~40% of slews – Concentrating at present on - Processing problems affect ~40% of slews – Concentrating at present on slews which process correctly first time – Finding solutions to particular slews which process correctly first time – Finding solutions to particular problems as we progressproblems as we progress

- Some slews contain sections with high exposure, related to the closed-- Some slews contain sections with high exposure, related to the closed-loop slew phase. Sub-Images with large exposures are excluded at loop slew phase. Sub-Images with large exposures are excluded at present present

- High background slews (~25%) are excluded at present- High background slews (~25%) are excluded at present - from 297 FF, eFF, LW slews, we are initially processing 219 and expect - from 297 FF, eFF, LW slews, we are initially processing 219 and expect

to find ~3600 sources to find ~3600 sources - but, we can probably recover a lot of the high background - but, we can probably recover a lot of the high background slews by subsetting the data using GTIsslews by subsetting the data using GTIs

UY VirUY VirDSS Image 2’×2’ Total band (0.2-12 keV)

Hard band (2-12 keV)Soft band (0.2-2 keV) (RASS src)

Blue circle in X-ray image indicates a detection

Four GalaxiesFour Galaxies

ESO443-IG005Mrk 352

MCG 04-53-021 NGC5899

Non-RASS

Two Merging Two Merging Galaxy PairsGalaxy Pairs

NGC 4748

II Zw 742

Soft source not detected in full energy band

Hard source not detected in full energy band

Extra background in full-energy band (sometimes just 1 photon!) can flip statistics below the threshold (DET_ML=10)

Faint sources detected in soft/hard-Faint sources detected in soft/hard-band but not in full-bandband but not in full-band

Sources detected in separate slewsSources detected in separate slews

- Source detected in 3 separate slews: Rev 0570, Rev 0573, Rev 0574

- Known ROSAT source (+faint galaxy)

- Evidence for variability (factor ~2)

Well Known SourcesWell Known Sources

N132D

(4.1″ pixels)

1RXS J134143.6-165736

LMXRBRASS~145 ct/s

Pseudo-MIPs (e.g. 2 ~9keV Photons/pixel in a frame)

LW mode

Extremely Bright SourcesExtremely Bright Sources

… … and other oddities…and other oddities…

Southern source - RASSNorthern source – non-RASS

Optical Loading – A Problem?Optical Loading – A Problem?0

.2-2

.0 k

eV

counts

V Magnitude

CD 36-1289 : X-ray emission from this V=10.5 star, but none from neighbours at V=6.5 and V=7.6

Several examples like this

- No correlation between source counts and Vmag for bright stars- Consistent with optical loading predictions: 5 counts expected above 200eV only for stars brighter than V=3.75

No optical loading problems – Genuine X-ray sources

Mediu

mFilt

er

Stars in Slew

Correlations with 2MASSCorrelations with 2MASSBlue squares:Number of 2MASS sourcesvs. distance to slew source

Green diamonds:Equivalent distribution for random sky positions(same number of sources)

Red triangles:Difference in distributionsi.e. Blue minus Green

Pointing accuracy of Slew survey ~6″

… but long tail…?

- 407 Slew source matches with ROSAT BSC & FSC out to 120″ - Distribution of distance offsets shown- Small error (includes RASS error), but long tail…?

Correlations with ROSATCorrelations with ROSAT

Attitude ProblemAttitude ProblemTwo types of positional error

(1) Real error of ~6″

(2) Error of 0-60″ (mean 30″) but only in slew direction Likely due to the current ATS attitude file having only 1sec time resolution

Slew direction

AB Dor

Also may be cause of patterns in exposure maps

‘Error ellipse’ around source (slew-oriented)

Optimistic we can remove error (2) by re-processing the attitude data (RAF?)

Error (1) remains, but easily small enough to allow good optical follow-up

Correlations with ROSATCorrelations with ROSAT- RASS count rate versus XMM Slew count rate for 407 matches

- Line shows 10:1 factor

- ~45% of Slew sources with <5cts are RASS sources - comparable with whole sample

Correlations with ROSATCorrelations with ROSATAll Slew sources:Hardness ratio vs Galactic latitude

Green circles:No RASS counterpart

Red crosses:RASS counterpart

Hard sources not seen by ROSAT

RASS sources on average softer than non-RASS sources

Hard

ness

Correlations with ROSATCorrelations with ROSATAll Slew sources inGalactic coordinates

Green circles:RASS counterpart

Red crosses:No RASS counterpart

No obvious trend

Survey Survey CharacteristicsCharacteristicsSource Count Distribution Exposure Time Distribution

Minimum @ ~ 4 counts Maximum @ ~ 10 seconds

- Can calculate flux limits for the XMM-Slew survey

RASS 5.0x10-13 (92% of sky) EMSS 3.0x10-12 (2% 0f sky) HEAO-1 3.6x10-11 (all-sky)Exosat 5.0x10-11 (?% of sky)RXTE 1.0x10-11 (all-sky), but with only 1° positional accuracy

Flux limitsFlux limits

ScheduleSchedule

- Initial processing of slew data- Initial processing of slew data (finished)(finished)- Creation of images, source searching, rejection of spurious sources- Creation of images, source searching, rejection of spurious sources (Feb to May)(Feb to May)- Cross correlation with ROSAT, other catalogues, DSS, SDSS etc.- Cross correlation with ROSAT, other catalogues, DSS, SDSS etc. (Apr to July) (Apr to July)- Creation of final catalogue for ingestion into XSA- Creation of final catalogue for ingestion into XSA (Aug to Sep) (Aug to Sep)- Ingestion into XSA- Ingestion into XSA (end of September) (end of September)

- Investigate extended sources - Investigate extended sources (begin May)(begin May)- Search co-added slews - Search co-added slews (TBD)(TBD)

- 2 new (ESAC) trainees, Diego Bermejo, Veronica Lazaro, recently started on project- 2 new (ESAC) trainees, Diego Bermejo, Veronica Lazaro, recently started on project

Now

Conclusions from current Slew analysisConclusions from current Slew analysis

- All available (374) Slews processed (~20% of sky)(Revs 314-785, → 100% of sky by mid-2014)

- 54 Slews source-searched to date (using best strategies):868 sources found in 1800 deg² (~4.5% of sky)~0.5 sources per square degree

- Soft X-ray band detection limit close to ROSAT All-Sky Survey

- Hard X-ray band detection limit deepest ever:> 10× deeper than EXOSAT, HEAO-1~ 2.5× deeper than RXTE (only has 1° positional accuracy)

- XMM-Slew positional accuracy ~6″Additional ‘attitude-error’ (30″ mean), but only along slewConfident that this attitude-error can be drastically reduced

- Aim to recover science from high-background slews

- Encountering & solving problems en route – Still on schedule…