Productdecisiontrees
AnexplanationofthePACSspectroscopy
productstousefordifferenttypesof
sciencecase
HERSCHEL-HSC-DOC-2166
v1(March2017), KatrinaExter(HSC)
Introduction
Inthissetofproductdecisiontrees,weshowwhichofthevariousproductsofPACSspectroscopytousewhenworking
withdifferentsciencecases.TheinformationhereisacondensedversionoftheQuickStartGuide(QSG),whichitselfis
acondensedversionofthePACSHandbook(PH);thesetwodocumentsshouldbeconsultedformoreinformation,
particularlyon:thedifferenttypesofcubes,howthedataareorganised inthespectrumtables,howtoidentifythetype
ofobservationyouareworkingwith,whattheFITSfilesarecalledandwheretheycanbefoundinadownloaded
observation,andhowtousethevarioustasksorpipelinesmentionedhere.
Inthefollowingpages,RED boxesarequestionstheuserhastoaskhis or herself,BLUE boxesareexplanations,actions,
oroptions,andGREEN boxesaretheproductstouse.(Notethatoftenmorethanonetypeofproductissuitablefor
anyparticulartypeofobservation,target,orscience.)
Inthenextpagesare:
• Pages2-4:anintroductiontotheterminologyofPACSspectroscopy:thenamesofthedifferenttypesof
observation,cube,andtable(forlongerexplanationswereferyoutotheQSGand PH).
• Page5:alistofthethesciencecasesthatareconsideredinthedecisiontrees.
• Pages6-8:asketchofthethetypesofcubesandtablestousefordifferentsortsofobservations.
• Page9:whatinformationyouneedtogatherbeforereadingthedecisiontrees.
• Pages10-13:thedecisiontrees
1
Terminology
AOT
AstronomerObservationTemplate,shorthandfortheobservingmodeoftheobservation.
ForPACSspectroscopy,themodeswere:chop-nodorunchopped (referstothewaythetelescopebackgroundwas
sampledduringanobservation),line-scan,range-scan,orSED (referstothespectralcoverage),mapping (Nyquist,
oversampled,ortiling)orpointed (referstothetypeofpointing).
Notethatwhilethepointedmodewasrecommendedforpointsources,manyextendedsourceswere in factalso
observedinthismode.Donotconfusedthe“pointed”AOTwith“pointsource”.
Level2,3,orLevel2.5?
TheLevelsofanobservationindicatehowfarthepipelineprocessinghasreached.FormostAOTs,theLevel2isthelevel
withthescience-useproducts,andoneextraspectraltable(createdfromtheLevel2tablesfrommultipleobservations)
canbefoundinLevel3 forchop-nodSEDAOTs.Forunchopped range-scanAOTs,thescience-useproductsareinLevel
2.5.ThesamerangeofcubesandspectraltablesarefoundatLevel2and2.5,butthosefromLevel2.5areacombination
oftheLevel2fromtwoseparate,butlinkedobservations(oneofthetarget,oneofthebackground)andare
“backgroundsubtracted”(witha“BS”inthefilename).Formoreinformation,includingtheFITSfilenamesofall
productsinanobservation,seetheQSG.
Spaxel
Aspatialpixel,i.e.onesmallpatchofskywithafullspectrum.Usually“spaxel”referstothenativespaxel ofthe
instrument(9.4”),and“spatialpixel”moreoftenreferstothespectral—spatialunitofamosaiccube.
2
Terminology
Rebinned cubes
Therearevarioustypesofcubesproducedbythepipeline.Rebinned cubesareprovidedforeverytypeofobservation,
andtheyarethefirstscience-usecubesofthepipeline.(Thenamecomesfromthefactthattheyarethespectrallyrebinned versionofthepreviousclassofcubeinthepipeline.)ThesecubeshavethespatialgridofthePACSIFU,i.e.a
slightlyirregular5x5spaxel grid.
Mosaiccubes
Mosaiccubesarecreatedfromtherebinned cubes.
Formappingobservations:theyarethecombinationoftheindividualpointings intheraster.Threetypesofmosaic
cubesarecreated– interpolated,projected,ordrizzled– dependingonthemappingmode.Theirspatialgridisregular,
withspatialpixelsof1.5”to3”.
Forpointedobservations:interpolatedandprojectedcubesarealsocreated– heretheyarenotamosaic,butrathera
spatially-resampledsinglepointingturnedfroma5x5irregulargridof9.4”spaxels toaregularspatialgridof0.5”
(projected)or3”(interpolated)spatialpixels.
TheQSGandthePHshouldbeconsultedtounderstandtheuse-caseforthesedifferenttypesofcubesandthe
differencesbetweenthealgorithmsthatcreatethem:notalltypesofcubearesuitableforalltypesofobservingmode.
Equidistantcubes
Allmosaiccubesarealsoofferedinan“equidistant”version. Thespatialgridisthesameasitsparentmosaiccube,but
thespectralgridhasbeenresampledtohaveequal-sizedbinsacrossthespectralrangeofthecube,ratherthanbins
thatscalewiththespectralresolution.Werecommendusingtheequidistantcubesforscienceonlyafterconsulting
theQSG andPH toknowhowtheequidistantspatialgridismade.
3
Terminology
Mappingmodekey
Threetypesofmappingmodewereoffered:oversampled,Nyquist,andtiling.Akeytoidentifyingthemappingmodefor
anycubefromitsFITSheaderkeywordscanbefoundinthePH tables8.6,8.7.AnAOT-keywordsspreadsheetforall
PACSspectroscopyobservationscanbefoundon:
http://herschel.esac.esa.int/twiki/bin/view/Public/PacsCalibrationWeb?template=viewprint#AOT_table_for_PACS_spect
roscopy.
Cubenames
ThecubesarecalledHPS (HerschelPACSSpectroscopy)3D (3dimensions)[P|I|D](projected,interpolated,ordrizzled
algorithm)[BS]ifLevel2.5(backgroundsubtracted)andthen[R|B](redorbluecamera).Thedirectoryandfilenames
willincludethiscombinationofletters.Hereweexcludethe[BS][R|B]fromthecubenames.
Spectraltables
Twotypesofspectraltableareoffered:point-sourcetablesandrebinned cubetables.Thefirstcontainpoint-source
calibratedspectraforpointedobservations.Thesecondareprovidedforallobservations,andeachtablecontainsthe
spectrumofeachspaxel ofeachrasterposition(wavelength,flux,error,coordinates…),foronerequestedwavelength
rangeintheobservation:multipletablesareprovidedwheremultiplewavelengthrangesexist.Theorganisation ofthe
datainthetablesinexplainedinthePH chp.8.
SlicesandcamerasintheFITSfilenames
Forobservationswithmultiplewavelengthranges,aseparatecubeortableofeachclassiscreatedforeachrange:these
arecalledseparate“slices”.FormappingAOTs,therebinned cubesagainhavemultipleslices– oneperrasterposition
(forthemosaiccubestherewillbeonlyonepointingslice,asthemosaicsarethecombinationofalltherebinned cubes
fromeachpointing).SlicenumbersareintheFITSfilenameas“_s##.Eachcubeandtablealsohasared(R)andablue
(B)cameraversion.
4
Information:Typesofsourcesconsideredinthedecisiontree
PointSource
Anyunresolvedsource.(TheFWHMofthePACSbeamis9”intheblueand14”in
thered.)
Smallsource
Anysourcethathasafullsizeofabout<15”,i.e.thatfitsfullywithinthecentral
3x3spaxels ofthenativePACSfootprint.
Extendedsource
Anysourceislargerthanapointandwhichisnotfullyflatovertheobserved
field.Thisincludesanythingfromsmallsourcestosourceslargerthanthe
mappedfield.
Flatsource
Anysourcethathasatmostashallowgradientovertheobservedfield(<20%).
5
Information:TypesofmosaiccubesforthemappingAOTs
Tiling
Interpolatedcube(HPS3DI…).
Nyqist
Projectedcube(HPS3DP…)forrangescanAOTs;projectedordrizzled(HPS3DD…)cubeforlinescanAOTs.
Oversampled
Projectedcube(HPS3DP…)forrangescanAOTs;projectedordrizzled(HPS3DD…)cubeforlinescan
AOTs.
Alternativefor
allthreeabove
Alloftheabovecubesarealsoofferedinanequidistantversion(EQ);foreachobservation,one
equidistantcubetypeisprovidedasastandalonebrowseproduct.
Alternative
(foranyAOT)
IfworkinginHIPEandusingoneoftheUsefulscriptstocreatefittedlineintensityorvelocitymaps,
thiscanbedonewiththemosaiccubesand alsowiththerebinned cubes(HPS3DR…).
6
Information:TypesofcubesforthepointedAOT
Rebinned cube(HPS3DR...)
Thesecubesarethescienceproducttobeusedforobservationsofpointorsmallsources.
However,theyhaveanirregularspatialgrid(5x5of9.4”spaxels)andcanbedifficultto
properlyvisualiseinsoftwareotherthanHIPE.
Interpolatedcube(HPS3DI...)
ortheequidistantversion
(HPS3DIEQ...)
Interpolatedcubesarealsoprovidedforpointedobservations.Theyhavearegular
spatialgrid,withspatialpixelsof3”size.Theyarethereforeeasiertoloadintosoftware
otherthanHIPE,andforextendedsourcesitiseasiertovisualisethemorphologyof
thesetarget.
7
Information:TypeoftablesforanyAOT
Pointsources
Point-sourcetable:HPSSPEC… (Level3forchop-nodSEDs,Level2or2.5
otherwise).
Anysource
Rebinned cubetable:HPSTBR…
PointedAOT
Mapping
AOTs
Rebinned cubetable:HPSTBR...(eachtableconains theentireraster)
8
Preliminarystep:Informationtogatherabouttheobservation
Chopnod orUnchopped
Step1: determinetheAOToftheobservation
LineScan orRangeScan (fullSEDorshorterrange?)
PointedorMapping(Tiling,Nyquist,Oversampled)
UseLevel2.5(thebackground-subtracted
on-sourceobservationfromanunchopped
rangescanon/offpair)
Step2: determinewhichLeveltoworkfrom
Step3: whichcameraandwhich
“slice”coversthewavelengthrange
youareinterestedin?
IsaLevel2.5present?
Findyourobsid rowintheAOTkeywordsspreadsheet♱,orcheck
thekeywordsdirectlyfromthecube
Hereyouarelookingforthewavelengthrangesandtheslice
numberofthecubes.Thisinformationtakenfromprojected
cubeswillalsoapplytotheothermosaiccubesinthe
observation.
UseLevel2(however,iftheAOTis
unchopped rangescan,notethatthedata
willnotbebackgroundsubtracted)
Rebinned cubes(HPS3DR[BS][R|B])
Projectedcubes (HPS3DP[BS][R|B])
9
Decisiontreeforpointsources
Mapping
Pointed
AOT
LookattheHPS3DR... cubeto
estimatetheoffsetofthe
pointsourcefromthecentral
spaxel.PH sec.9.2.1.1
Yes
No
Canyoulocatedthe
HPS3DR… cubeinwhich
thepointsourceisnicely
centred?
InputtotheFMTisamodel
ofthesource(inthiscasea
narrowGaussian)andthe
source’sspectrum
Yes
No
Issourcefullycentred ina
spaxel (butoutsidethe
centralone)?
Usetwosimpletasksin
HIPEtoextractthe
calibratedspectrum
fromtheHPS3DR…
cube.PH sec.9.2.1.4
Chop-nodAOT
RuntheForward
ModellingToolinHIPE
toestimatethepointsourcecorrectionto
applytothespectra
fromtheHPS3DR…
cube(pointed)orthe
HPS3D[IPD]… mosaic
cube(mapping).
PH sec.9.2.1.5
0“-5”
0“-10”
Entireobservationandrun
thePointingOffset
Correctionpipelinescript
inHIPE.PH sec.9.2.1.3
Forsourcesoffsetfromthe
centre ofthecube,orobserved
duringaperiodofbad
telescopepointingjitter,the
spectrumresultingfromthis
scriptcanhaveabetter
continuumshapeandsmoother
broad-bandfeaturesthan
HPSSPEC.
HPSSPEC…
Unchopped AOT
>=10”
Chop-nodAOT
HPSSPEC…[‘PointSourceScaledFlux’]or
HPSSPEC…[‘PointSourceCen3x3Flux’]for
sources>5Jy.
HPSSPEC…[‘PointSourceFlux’]forfainter
sources.
(i.e.usethatwiththemostfluxandbest
SNR). PH sec.9.2.1.2
HPSSPEC…[PointSourceCen3x3Flux’]for
sources>5Jy.HPSSPEC…[‘PointSourceFlux’]
forfaintersources.
(i.e.usethatwiththemostfluxandbestSNR).
PH sec.9.2.1.2
10
Decisiontreeforsmallsources
Mapping
Pointed
AOT
LookattheHPS3DR... cubeto
estimatetheoffsetofthe
sourcefromthecentral
spaxel.PH sec.9.2.2
Yes
No
Canyoulocatedthe
HPS3DR… cubeinwhich
thesourceisnicely
centred?
0“-5”
>=10”
RuntheForwardModellingToolinHIPE
toestimatethetruesourcespectrum,
startingfromtheHPS3DR… cube,which
formappingAOTSarethenrunthrough
oneofthemosaictasks(HPS3D[IPD]...).
PH sec.9.2.2,9.2.3
InputtotheFMTisamodelofthesource
morphologyandthesource’sspectrum
No
Doyouhaveamodelofthe
morphologyofthesource?
No
Youcandoaperturephotometry
ontheHPS3DI… cube,butbe
awareofthehigherassociated
uncertainties.PH sec.9.2.2,9.2.3
Yes
Yes
Doyouhaveamodelofthe
morphologyofthesourceanda
representativespectrum?
Chop-nodAOT
UsetwotasksinHIPEtoextract
thecalibratedspectrumfromthe
HPS3DR… cube.PH sec.9.2.2
ThefirsttaskisextractCentralSpectrum,fromwhich
youshouldadopt‘c129’or‘c9’(whicheverhasthe
betterSNR)forsources>5Jy,‘c1’forfainter(i.e.use
thatwiththegreaterfluxandbetterSNR).Forthe
secondtaskyouneedamodelofthemorphologyof
thesource.
Unchopped AOT
ThefirsttaskisextractCentralSpectrum,fromwhichyoushouldadopt‘c9’for
sources>5Jy,‘c1’forfainter(i.e.usethatwiththegreaterfluxandbetterSNR).
Forthesecondtaskyouneedamodelofthemorphologyofthesource.
11
Decisiontreeforextendedsources
Seetherelevantpageofthisguideto
knowwhichmosaiccubeisbesttowork
with(dependsonthemappingmode)
Youcandoaperture
photometryonthe
HPS3D[IPD]… cube,but
beawareofthehigher
associateduncertainties.
PH sec.9.2.3
Pointed
InspectionandscienceviatheHPS3DI...
cube,sciencecanalsobedonewiththe
HPS3DR.. cubeortheHPSTBR... table
Doyouhaveamodelofthe
morphologyofthesourceanda
representativespectrum?
No
Yes
No
Doyouhaveamodelofthe
morphologyofthesourceanda
representativespectrum?
AOT
RuntheForwardModelling
ToolinHIPEtoestimatethe
truesourcespectrumoverthe
fieldfromtheHPS3DR… cubes,
whichshouldthenbe
processedthroughtherelevant
cubemosaictask
(HPS3D[IPD]…).PH sec.9.2.3
Youcandoaperturephotometry
ontheHPS3DI… cube,butbe
awareofthehigherassociated
uncertainties.PH sec.9.2.3
Yes
Mapping
RuntheForwardModelling
ToolinHIPEtoestimatethe
truesourcespectrumoverthe
fieldfromtheHPS3DR… cube,
whichcanthenberunthrough
oneofthemosaictasks
(HPS3DI…).PH sec.9.2.3
12
Decisiontreeforflatsources
Mapping
Seetherelevantpageofthisguideto
knowwhichmosaiccubeisbesttowork
with(dependsonthemappingmode)
AOT
Pointed
Inspectionandaperturephotometry(or
entirecubeextraction)canbedonewith
theHPS3DI... cubeandwiththeHPS3DR..
cubeortheHPSTBR... table(althoughfor
inspectiontheHPS3DI…cubesarethe
easiest)
Youcandoaperture
photometry(orentire
cubeextraction)onthe
HPS3D[IPD]… cube
13