Dust in Historical Galactic Type Ia Supernova Remnants with Herschel

1.2 MB·English

by  H. L. Gomez

Mon.Not.R.Astron.Soc.000,??–??(2011) Printed4January2012 (MNLATEXstylefilev2.2)
Dust in Historical Galactic Type Ia Supernova Remnants with
⋆
Herschel
2 H.L. Gomez1, C.J.R.Clark1, T. Nozawa2, O. Krause3, E.L.Gomez1,4, M. Matsuura5,
1
0 M.J.Barlow5, M.-A. Besel3, L. Dunne6, W.K.Gear1, P. Hargrave1, Th. Henning3,
2
n R.J. Ivison 7,8, B. Sibthorpe7, B.M.Swinyard5,9, R. Wesson10
a
J 1SchoolofPhysics&Astronomy,CardiffUniversity,TheParade,Cardiff,CF243AA,UK

3 2InstituteforthePhysicsandMathematicsoftheUniverse,UniversityofTokyo,Kashiwa,Chiba277-8583,Japan
3Max-Planck-Institutfu¨rAstronomie,Ko¨nigstuhl17,69117Heidelberg,Germany

] 4LascumbresObsveratoryGlobalTelescopeNetwork,6740CortonaDriveSuite102,Goleta,CA93117
A 5Dept.ofPhysicsandAstronomy,UniversityCollegeLondon,GowerStreet,LondonWC1E6BT,UK
G 6SchoolofPhysics&Astronomy,UniversityofNottingham,UniversityPark,NottinghamNG72RD,UK
7UKAstronomyTechnologyCentre,RoyalObservatoryEdinburgh,BlackfordHill,EdinburghEH93HJ,UK
.
h 8InstituteforAstronomy,UniversityofEdinburgh,BlackfordHill,EdinburghEH93HJ,UK
p 9SpaceScienceandTechnologyDepartment,RutherfordAppletonLaboratory,Oxfordshire,OX110QX,UK
- 10EuropeanSouthernObservatory,AlonsodeCordova3107,Casilla19001,Vitacura,Santiago19,Chile
o
r
t
s
a
[

ABSTRACT
2
Theoriginofinterstellardustin galaxiesispoorlyunderstood,particularlytherelativecon-
v
tributions from supernovae and the cool stellar winds of low-intermediate mass stars. Re-
7
2 cently,largemassesofnewly-formeddusthavebeendiscoveredintheejectaofcore-collapse
6 supernovae. Here, we present Herschel PACS and SPIRE photometry at 70-500µm of the
6 historical, young supernova remnants: Kepler and Tycho; both thought to be the remnants
. of Type Ia explosion events. We detect a warm dust component in Kepler’s remnant with
11 Td = 82+−46K and mass ∼ (3.1+−00..86)×10−3M⊙; this is spatially coincident with thermal
X-rayemissionandopticalknotsandfilaments,consistentwiththewarmdustoriginatingin
1
1 the circumstellarmaterialsweptupbythe primaryblastwave ofthe remnant.Similarlyfor
v: Tycho’sremnant,wedetectwarmdustat90+−57Kwithmass(8.6+−21..38)×10−3M⊙.Comparing
thespatialdistributionofthewarmdustwithX-raysfromtheejectaandswept-upmedium,
i
X andHαemissionarisingfromthepost-shockedge,weshowthatthewarmdustissweptup
interstellarmaterial.We findnoevidenceof a cool(25-50K) componentofdustwith mass
r
a ≥0.07M⊙asobservedincore-collapseremnantsofmassivestars.Neitherthewarmorcold
dust components detected here are spatially coincident with supernova ejecta material. We
compare the lack of observed supernovadust with a theoreticalmodel of dust formation in
TypeIaremnantswhichpredictsdustmassesof88(17)×10−3M⊙forejectaexpandinginto
ambient surrounding densities of 1(5)cm−3. The model predicts that silicon- and carbon-
rich dust grains will encounter, at most, the interior edge of the observed dust emission at
∼400yearsconfirmingthatthemajorityofthewarmdustoriginatesfromsweptupcircum-
stellarorinterstellargrains(forKeplerandTychorespectively).Thelackofcolddustgrains
intheejectasuggeststhatTypeIaremnantsdonotproducesubstantialquantitiesofiron-rich
dust grains and has importantconsequencesfor the ‘missing’ iron mass observed in ejecta.
Finally, although,we cannotcompletely rule out a small mass of freshly-formedsupernova
dust,theHerschelobservationsconfirmthatsignificantlylessdustformsintheejectaofType
Iasupernovaethanintheremnantsofcore-collapseexplosions.
Keywords: Supernovae:individual:Kepler,Tycho–ISM:submillimetredust:ISM–Galax-
ies:abundances–submillimetre
⋆ HerschelisanESAspaceobservatorywithscienceinstrumentsprovided byEuropean-ledPrincipalInvestigatorconsortiaandwithimportantpartic-
ipationfromNASA.
2 H. Gomezet al.
1 INTRODUCTION Wilson & Batrla 2005). Recent observations with the Balloon-
borne Large Aperture Submillimeter Telescope, BLAST and the
Dustingalaxiesisthought tobeproducedbyinthestellarwinds HerschelSpaceObservatoryshoweditwasdifficulttodistinguish
of both low-intermediate mass (LIM) Asymptotic Giant Branch between colddust inthe remnant and cold dust fromintervening
(AGB)stars(e.g.Gehrz1989; Whittet2003; Sargentetal.2010) interstellarclouds usingphotometry alone (Sibthorpeet al.2010;
and,toanunknownextent,bymassivestars(Ho¨fner2009;Gomez Barlowetal.2010).Thesestudiesrevealedanewcoolcomponent
etal.2010;Andrewsetal.2011;Gall,Hjorth&Anderson2011a). of dust in Cas A with mass 0.08M⊙ at ∼ 35K, yet even if all
Massive stars may also produce dust in the expanding gas ejecta ofthedustsurvivedthepassagethroughtheshock,thedustmass
whentheyexplodeassupernovae(e.g.Claytonetal.2001;Todini isaboutoneorderofmagnitudelowerthannecessarytosolvethe
&Ferrara2001).IntheMilkyWay(seeZhukovska&Gail2008), dustbudgetproblem.
themajor dust source ispresumed tobeLIMstars, but whenac-
Apossiblemethodtodistinguishbetweensupernovadustand
countingfordustdestructiontimescalesandtheobserveddustmass
contaminationfrominterstellarmaterialalongthelineofsightwas
intheGalaxy,thedustinjectionratefromstarsrequiredisanorder
proposedbyDunneetal.(2009) wheretheytracedthealignment
ofmagnitudehigherthanobserved.Analternativesourceofdustis
ofthedusttowardsCasAwiththeSNRmagneticfieldusingpo-
requiredtomakeupthedustbudget(e.g.Jones2001).Thisshortfall
larimetry at 850µm. They find that a significant fraction of the
inthedustmassestimatedfromthedustinjectionratesfromLIM
submmemissiontowardsCasAisstronglyalignedwiththemag-
starsisalsoobservedintheinterstellarmedium(ISM)oftheLarge
netic field of the remnant. The dust mass inferred from the po-
MagellanicCloud(Matsuuraetal.2009),ingalaxiesouttoz=0.4 larimetry study of Cas A agrees with the dust masses estimated
(Dunneetal.2011) andindustyhigh-redshiftgalaxies(seeMor-
fromHerschel photometry observations of the core-collapse SNe
gan&Edmunds2003;Dwek,Galliano&Jones 2007).Although
SN1987A (Matsuuraetal.2011); intheformer0.2−1.0M⊙ of
recentworkbyJones&Nuth(2011)suggest thatthedust-budget
dustwasdetecteddependingonthecomposition.Thelimitonthe
problemisnotasproblematicaspreviousworkssuggestgiventhe
ejectedheavyelementmassinthesesourcesplacesafurthercon-
uncertaintiesinmasslossratesandtheefficienciesofdustforma-
straintonthemaximumphysicaldustmass,finding0.2 < M <
d
tioninstellarwinds, itisclear that significant dust production in
0.5M⊙.
SNejectawould alleviatethisdust budgetary problem. Theaver-
Theevidencefordustformationincore-collapseSNRsisac-
agedustyieldperSNrequiredtoexplaindustygalaxiesatbothlow
cumulating,thoughitisnotyetunderstoodwhethertheamountof
andhighredshiftsisoforder0.5−1M⊙(Michałowski,Watson& SNdustcreatedisdependentontheprogenitormass,themetallic-
Hjorth2010;Gall,Anderson&Hjorth2011b).
ityorthetypeofexplosion.Neitherisitclearhowmuchdustwill
AlthoughSNehavelongbeenproposedasasourceofdustin survive,thoughtheoreticalstudiessuggestasignificantfractionof
theISM(Dwek&Scalo1980;Claytonetal.2001),observational dustgrainsformedinejectawillbedestroyedbeforeinjectioninto
evidencehasbeenscarceuntilrecently.Woodenetal.(1993)first the ISM (Jones 2001; Bianchi & Schneider 2007) particularly in
detected emission from 10−4M⊙ of dust in SN1987A using the theejectaofenvelope-poorcore-collapseSNeorTypeIaremnants
Kuiper Airborne Observatory. Subsequent Mid-far-infrared (FIR) (Nozawaetal.2010;Nozawaetal.2011).Asyet,thereisnoclear
observationsofGalacticandextra-galacticcore-collapseremnants evidenceforfreshlyformeddustintheremnantsofTypeIaexplo-
withtheSpitzer SpaceTelescopedetect small quantitiesof warm sions,thoughtheoreticalmodelsofdustformationintheremnants
dust(∼(1−50)×10−3M⊙)inyoung(t<1000days-Sugerman ofTypeIaeventssuggeststhatupto0.2M⊙dustcouldforminthe
etal.2006;Meikleetal.2007,2011;Kotaketal.2009;Andrewset ejecta(Nozawaetal.2011).
al.2010,2011;Fabbrietal2011;Szalaietal.2011)andoldrem- Historicalremnantsareuniqueprobesforunderstandingdust
nants(Williams,Chu&Gruendl2006;Rhoetal.2008).Theevi- productionandindeed,destructionfollowingcorecollapseTypeII
dencefordustproductioninTypeIaremnantsisscarce(Borkowski supernovaeaswellaslowmassbinaryTypeIevents.IntheHer-
et al. 2006; Seoket al. 2008): mid-IR observations of the Kepler schelera,wearefinallybeginningtoprobethecontributionofSNe
SNRwiththeInfraredSpaceObservatory(ISO;Douvion,Lagage tothedustbudget,yetgiventhesomewhatlargeuncertaintiesinour
& Pantin 2001) found thermal emission from warm dust (100K) understandingofthedustyieldfromstellarsourcesinothergalax-
withmass10−4M⊙.Morerecently,Ishiharaetal.(2010)detected iesandininterpretingstatisticaldescriptionsofthedustcontentin
10−3M⊙ofswept-up(warm)dustintheTychoSNRwithAKARI, galaxiesfromwide-areasurveys(e.g.Dunneetal.2011),itisim-
withatentativesuggestionthat10−4M⊙ofdustseeninthenorth- portanttoinvestigatedustproductioninthosenearest,youngestand
east of the remnant may have been formed inthe ejecta. Outside resolvedgalacticremnants.Onecanalsoarguethatunderstanding
of our Galaxy, Borkowski et al.(2006) obtained mid-IRobserva- dustformationinsupernovaeisimportantregardlessoftheexplo-
tions of four Ia remnants in the Large Magellanic Cloud, finding sionmechanism:dustformationfollowingType-IISNemightsug-
< 10−2M⊙ of swept-up interstellar dust. The dust masses from gestthatType-IaSNewouldalsobelikelydustproducers(Clayton
themid-farIRstudiesareordersofmagnitudelowerthanneeded etal.1997;Travaglioetal.1999).Alternatively,detectingdustfrom
tosolvethedustbudgetissues. circumstellarmaterialsweptupbytheblastwaveofaTypeIacan
Inordertoinvestigateifsupernovaremnants(SNRs)contain beausefulprobeoftheprogenitorandexplosionmechanism.
colddust missedbyprevious infrared(IR)observations, theSub- The resolution, wavelength coverage and sensitivity of Her-
millimetre Common User Bolometer Array (SCUBA) was used schel allows us to investigate the origin and quantity of dust in
to observe Cassiopeia A (Cas A), a remnant of a Galactic core- historicalsupernovaremnants.HerewepresentIRandsubmmob-
collapseSNe(Krauseetal.2008a).Thecolddustseenat450and servations (§2) of the Tycho and Kepler remnants. Wedetermine
850µmwasinterpretedasemissionfromdustassociatedwiththe thedustmassinandtowardstheremnantsin§3and§4andcom-
remnantduetothespatialcorrelationwiththeX-ray,radioandsub- paretheIRemissionwithmultiwavelengthtracersin§3.1and§4.1.
millimetre(submm)emission(Dunneetal.2003).Subsequently,a Theoriginofthedustisdiscussedin§5andweusethetheoretical
significantfractionofthesubmmemissionwasshowntooriginate modelofNozawaetal.(2011)tocomparetheexpecteddustmasses
frommolecularcloudsalongthelineofsight(Krauseetal.2004; withtheobservations.Theresultsaresummarisedin§6.
Dust intheKeplerand TychoRemnants 3
2 OBSERVATIONSANDDATAREDUCTION (Bonnareletal.2000).ForKepler’sremnantweusedobservations
inthe filters658, 660 and 502nm where the emission originates
2.1 HerschelPhotometry
fromHα+[NII],[NII]and[OIII]respectively(e.g.Sankritetal.
TheKeplerandTychosupernovaremnantswereobservedwiththe 2008). Badpixelsweremasked by hand. ForTycho, weuse data
Herschel (Pilbratt et al. 2010) Photodetector Array Camera and observed at 656nm (Lee et al. 2010), tracing Hα in the eastern
Spectrometer(PACS;Poglitschetal.2010)andSpectralandPho- limboftheremnant.
tometricImagingReceiver(SPIRE;Griffinetal.2010)at70,100, Spitzer Multiband Imaging Photometer (MIPS; Rieke et al.
160,250,350and500µmaspartoftheMassLossfromEvolved 2004)Level2calibrateddatawereobtainedviathearchive3 (Ke-
StarS survey (MESS: Groenewegen et al. 2011). Kepler was ob- pler: PI W.Blair;Tycho: PI J.Rho) at 24 and 70µm. For 100µm
servedon10thSeptand11thMarch2010; Tychoon20thMarch data,weusetheImprovedReprocessingoftheIRASSurvey(IRIS;
2010 and 18th Jan 2010 for PACS and SPIRE respectively. The Milville-Deschenes&Lagache2005) whichhavebeencalibrated
PACSdatawereobtainedin‘scan-map’modewithspeed20′′/sin- with respect to data taken with the Diffuse Infrared Background
cludingapairoforthogonalcross-scansoveranarea∼22′×22′. Experiment(DIRBE).WidefieldInfraredSurveyExplorer(WISE;
TheSPIREmaps wereobserved in‘LargeMap’ mode withscan Wrightetal.2010)datawerealsoobtainedat22µm.
lengthof30′ over∼ 32′×32′;across-scanlengthisalsotaken, Theradiodata at18cmfor Tychowas obtained through the
witharepetitionfactorofthree.Thedatawereprocessedfollowing Very Large Array (VLA) archive. The Kepler data at 6cm was
thedetaileddescriptiongiveninGroenewegenetal.(2011). kindlyprovidedbyT.DeLaney(DeLaneyetal.2002).TheChan-
The PACSmaps werereduced withthe Herschel Interactive draX-raydataforKepler (PIS.Reynolds; Reynolds etal.2008)
ProcessingEnvironment(HIPE;Ott2010)applyingalllow-levelre- and Tycho (PI J.Hughes; see Badenes et al. 2006; Katsuda et al.
ductionsteps(includingdeglitching)toLevel1.TheSCANAMOR- 2010) were available online as calibrated files extracted into soft
PHOSsoftware (Roussel 2011) wasthenused remove effectsdue andhardregionsoftheX-rayspectrum4.ForKepler’sremnant,the
tothethermaldriftsandtheuncorrelated1/f noiseoftheindivid- X-ray data used here range from 0.30− 0.72, 0.72 −0.90 and
ualbolometers.FinalLevel2mapcreationthroughdataprojection 1.7−2.1keV,andforTycho,wehave0.95−1.26,1.63−2.26
onto a changeable spatial grid was performed with SCANAMOR- and4.1−6.1keV.Theserangesshowlineemissionfromsilicon
PHOS.SincetheHIPEreductionwasbasedonthecalibrationfile andironorginatingfromtheejectaaswellassoftandhard(with
versionv5,interimcalibrationfactorsof1.12,1.15and1.17were thermalandnon-thermal contributions) X-raycontinuum orginat-
appliedtothePACSdataattherespectivewavelengthstobeconsis- ingfromtheblastwave.
tentwiththecurrentcalibrationfilev6.TheFullWidthHalfMax- To compare the submm data with the molecular emission
imum(FWHM)at70,100and160µmis6,8and12′′respectively. towards and surrounding the remnants, we use high resolution
ThefluxcalibrationuncertaintyforPACSiscurrentlyestimatedas 12CO(J = 2−1) and13CO(J = 2−1) observations for Ke-
10percentforthe70and100µmbandsand20percentat160µm pler (seeGomezet al.2009 forfull details).Wealsoinclude our
(Poglitschetal.2010).ColourcorrectionsforPACSareexpected SCUBAimageofKeplerat850µm(Morganetal.2003;Gomezet
tobesmallcomparedtothecalibrationerrors.Tocorrectforcolour al.2009).Lowresolutioncarbonmonoxide12CO(J =1−0)maps
withdustspectrumν1.0andtemperaturesof100K,wedividedby forTycho’sremnantweretakenfromtheCanadianGalacticPlane
1.00and1.031at70and100µm.The20Kinterstellardustcompo- Survey(CGPS;Tayloretal.2003).Thedatawereintegratedover
nentdominatesthe160µmimage,andassuchthecorrectionfactor −68 to −53kms−1 to compare the remnant with molecular gas
is0.957. thoughttobeinteractingwiththesupernovaremnant(see§3.1).
ForSPIRE,thestandardphotometerpipeline(HIPEv.5.0)was
used (Griffinet al. 2010) with an additional iterativebaseline re-
moval step (e.g. Bendo et al. 2010). The SPIRE maps were cre- 2.3 ZeroLevels
ated with the standard pipeline NA¨IVE mapper. We multiply the Due to the difficulty in finding a suitable baseline with which to
350µmdataproductby1.0067tobeinlinewithmostrecentcali-
subtractthebackgroundintheHerschelSPIREmaps,wecorrelate
brationpipeline(equivalenttoHIPEv7reduction).Sincethebeam thepixelintensityfromHerschelwiththearchivalIRASIRISmaps
areas increase as a function of pixel scale2, the FWHM is 18.1, (calibratedwithrespecttoDIRBE)toestimatethezerolevel(see
24.9 and 36.4′′ for pixel sizes of 6, 10 and 14′′, at 250, 350 and
Fig. 1, Table 1). The Herschel data were convolved to the same
500µmrespectively. TheSPIREcalibrationmethodsandaccura- angularresolutionastheIRIS100-µmmap(258′′)andregridded
cies are outlined by Swinyard et al. (2010) and are estimated to to 90′′ pixels. A least squares fit analysis was performed on the
beapprox10percent.Thepipelineproduces monochromaticflux
Herschel vs. IRIS data (whilst masking out the remnant) to de-
densities for point sources with νSν ∝ ν1.0 but at the longer termine the flux offsets; this sets the zero level of the PACS and
wavelengths,colourcorrectionsbecomesignificant.Wemultiplied
SPIREdataassumingthattheIRISdataisatruerepresentationof
by thecolour corrections 0.999,1.0045,1.0302 as defined inthe
thesky.Afurther scalingfactor needstobeaccounted fordueto
Herschel SPIREmanual2, appropriate for β = 1.5 and extended
the expected colour correction between the bands when compar-
sources.
ing to the 100µm band (the so-called ‘gain’ factor). These were
estimatedbyinterpolatingamodifiedblackbodycurveν2B(ν,T )
d
(after a preliminary correction of the zero levels). The zero level
2.2 MultiwavelengthDatasets
of the PACS and SPIRE maps are negative except for the PACS
Optical data for the Tycho and Kepler remnants were obtained 70µmmapofKepler.Theleastsquaresfitwasthenrepeated(see
from the Hubble Space Telescope (HST) archive via ALADIN e.g. Bracco et al. 2011). The errors on the fitting were estimated
1 http://herschel.esac.esa.int/twiki/pub/Public/PacsCalibrationWeb/ 3 http://irsa.ipac.caltech.edu/data/SPITZER/docs/spitzerdataarchives/
2 http://herschel.esac.esa.int/Docs/SPIRE 4 http://chandra.harvard.edu/pwarmo/openFITS/
4 H. Gomezet al.
Wavelength Zerolevel(MJy/sr)
(µm) Kepler Tycho
70 4.7±0.4 −0.9±0.1
100 −3.1±0.2 −2.5±0.3
160 −4.8±0.3 −2.6±0.2
250 −37.4±3.8 −30.8±4.8
350 −30.5±2.0 −20.4±2.1
500 −25.2±1.4 −7.7±1.3
Table1.ZerolevelonthePACSandSPIREmapscalculated usingleast
squaresfittoHerscheldataandIRASIRISdata.Errorsarethe1σestimated
frombootstrappingthedata1000timesandrefittingeachset.
Figure1.TheHerschelSPIREintensitiesfortheKeplerobservationsver-
susIRASIRIS100-µminMJy/sr.TheSPIREmapsareconvolvedtothe
sameresolutionastheIRISmapsandregriddedontothesamepixelscale. Figure2.Three-colourFIR-submmimageofKepler’sSNRwithPACSat
Theredlineistheleastsquaresfunction,thegreycirclesaretheHerschel 70(blue),100(green)and160µm(red).Theimagehasbeensmoothed.
datadividedbythegainfactor(duetothecolourcorrectionbetweenIRIS Theareashownis16.5′×16.6′.
at100µmandtheSPIREwavelengths).Thedataaremaskedatthelocation
oftheremnant.Thegreyshadedregionsindicatetheresultsfromthe1000
bootstrapfitstothesamedataset. themostlikelyclassificationusingbothironabundanceconstraints
andthelackofaneutronstar.ThedeepX-rayimagesalsoprovide
evidenceoftheblast-waveinteractingwithdensecircumstellarma-
using the confidence intervals from the bootstrap method, where terial(CSM).Thisisunexpected for TypeIaevents although ob-
1000fitsweremadetothebootstappeddata,Table1.Thiserroris servationsofCSMarebecomingmorewidespread;thepresenceof
addedinquadraturealongwiththecalibrationerrorslistedabove suchadenseCSMsurroundingKeplerledReynoldstosuggestthe
andintroduces(atmost)anerrorof∼ 17%(wellwithinthe20% thermonuclear explosion of a single massive star (M∗ ∼ 8M⊙)
calibrationerrorusedforPACSat160µm);notethatthisdoesnot asan alternative to thecanonical White-Dwarf (WD) binary sce-
accountforanysystematicerrors. narioof Iaexplosions. Whether Kepler was theresult of a single
progenitor or WD-AGB-binarysystem explosion, the mechanism
was likely to be a deflagration explosion (Yang et al. 2009; see
Woosley,Taam&Weaver1986forareviewonexplosionmodels).
3 KEPLER’SSUPERNOVAREMNANT
Inthisscenario, theheating of theejectabyradioactive elements
TheKeplersupernova event wasfirstseenbyJohannes Keplerin ishigher than in core-collapse remnants, the ejecta densities will
1604andtheremnanthasashell-likestructure∼3arcminindiam- alsodecreaserapidly,thoughtheejectaiswellmixedsincethere-
eter.Estimatesofitsdistance,usingHIabsorptionfeatures,range verseshockprogressesquicklythroughthelayersinadeflagration
from3.9to6kpc(Reynoso&Goss1999;Sankritetal.2008).Its explosion(see§5.1).
classification has been controversial (see the excellent reviews in The warm dust emission detected in Kepler with ISO (Dou-
Blair et al. 2007; Reynolds et al. 2008; Sankrit et al. 2008) with vionetal.2001),followsthewell-knownnorth-southshellasym-
evidencepointingtowardsbothType-Ia–thethermonuclearexplo- metryseenalsoatoptical,X-rayandradiowavelengths.Thecor-
sionofalow-massaccretingstarinabinarysystem–orType-Ib– relation of the dust with the optical Hα suggested the dust was
thecorecollapseofamassivestar.ThedeepestX-rayanalysiswith shock-heatedcircumstellardust,sweptupbytheshockwaveofthe
Chandra(Reynoldsetal.2008),however,suggeststhataType-Iais blast. Blair et al. (2007) used Spitzer to revise the dust mass to
Dust intheKeplerand TychoRemnants 5
5.4×10−4M⊙. They also found that emission at 70µm arises inKepler:continuumX-raysfromtheblastwavesweepingupsur-
onlyinthebrightestknotsoftheshellseenat24µm.The160µm rounding circumstellar and interstellar material, X-ray line emis-
Spitzerdatawaspoor-qualityduetoitslowresolutionandstrong sion fromthe warmejecta, and continuum emission arising from
background gradient. Morgan et al. (2003) originally interpreted thenon-thermalsynchrotronemissioninthenorth,southandeast-
theirlongerwavelength450and850-µmSCUBAdataasevidence ernlimbs.Thewarm dust emissionintheFIR isconfined within
for0.3–1M⊙ofcolddustassociatedwiththeremnant.Theycom- theradiusoftheouterblast-waveandisseenonlyatthebrightest
pared the emission from interstellar material towards Kepler us- points in the optical, radio and X-ray (Fig. 4 - as noted in Blair
ingsubmmcontinuumimagingandspectroscopicobservationsof etal.2007)withpeaksat70µmseenwherethesoftandhardther-
atomic and molecular gas, via HI, 12CO and 13CO and detected malX-raysoverlap.Therefore,thewarmdustisassociatedwiththe
weakCOemissionfromdiffuse,opticallythingasatthelocations densest gasbehind theforward shock rather thantheinner ejecta
of some of the submm clumps. The contribution to the submm material; thisconfirms the dust originates fromthe outermost re-
emissionfromforegroundmolecularandatomiccloudsusingthese gionsoftheremnanti.e.fromthesweptupshockedcircumstellar
COtracerswasfoundtobenegligible,buttheseemissionlinesmay and/orinterstellarmedium(§5.2).
notbetracingallofthegasintheISM.
ThethreecolourHerschelPACSimageofKeplerisdisplayed
3.2 Thespectralenergydistribution
inFig.2.Theremnantisclearlyseeninblueandfollowsthesame
asymmetric structure as seen in the X-ray and radio (§3.1): the TheIR-submmspectralenergydistribution(SED)towardsKepler’s
emissionisbrightestinthenorthalonganarc-likeshellandsome SNR isshown inFig. 5. Thefluxes estimated from Spitzer, Her-
emissionisseentowardsthecentreoftheremnant.Thelowlevel schelandSCUBAinthisworkwithinanapertureofradius120′′
redstructuresseenacrossthemap(outsideoftheremnant)origi- centredontheremnant,areplottedwiththeirerrors(estimatedfrom
natefromdustyinterstellarcloudswithtemperatures∼13−20K. thecalibrationerror,theerrorinthezerolevelestimatedin§2.3and
fromthevariationsinthepixelRMSwithintheaperture).Allthe
data were smoothed to the resolution of the SPIRE 500µm data
3.1 Themultiwavelengthview
usingaGaussiankernel.Theapertureissomewhatlargerthanthe
InFig.3,wepresentamultiwavelengthviewcentredonKepler’s SNR boundary defined by the edge of the radio (103′′) but was
SNR,comparingtheHerschelPACSandSPIREphotometricdata chosen to encompass the SNR emission in the images smoothed
with synchrotron emission from the remnant at 6cm, unrelated tothe500µmbeam.TheSpitzerfluxeswerecolourcorrectedus-
molecular gas(tracedbytheCOemission) and850µm emission ingalgorithmsdetailedintheMIPShandbook5.Wealsocompare
fromcolddust.Thecompleteshell-likestructureofSNmaterialis ourfluxeswithpreviouslypublishedfluxesintheliterature(Arendt
clearlyseenatradiowavelengths,tracingtheforwardandreverse 1989,Braun1987,Douvionetal.2001,Morganetal.2003,Blairet
shocks (DeLaney et al. 2002). In Fig. 4 we compare the optical al.2007)althoughthesewereobtainedusingapertureswithradius
and X-ray emission with the warm dust from Herschel-PACS at rangingfrom100−120′′andthereforedifferfromthefluxesinTa-
70µm.Thewell-knownnorth-southasymmetryseenatoptical,ra- ble2accordingly.Notealsothatwemeasurethefluxencompassed
dio and X-ray wavelengths with the enhanced northern emission intheaperturearoundKepler,andthereforeincludesemissionfrom
(thought to originate from the motion of Kepler through the sur- theforegroundcloud.
rounding interstellarmaterial)isalsoseeninthePACSdata.The The contribution to the IR/submm fluxes from synchrotron
‘arm’structureacrossthemiddle(clearlyseenintheradio,Fig.3) emissionisobtainedbyscalingtheVLAradiomapofKeplerus-
originatesfromaprojectioneffectofmaterialinthefrontandback ingaconstant spectral index, Sν ∝ να wherethemean valueof
oftheshell(Blairetal.2007).HerscheldetectsfaintIRemission αis−0.71butrangesfrom-0.6−-0.85(DeLaneyetal.2002).The
arisingfromthiscomponentat70µm.Thefaint‘ear’-likefeatures synchrotronemissionat500µmis0.20±0.06Jy(∼ 15percent
seenalongtheoutermostmidsectionoftheexpanding shellatra- of thetotal flux). Wefitatwo-component modified blackbody to
dio and X-ray wavelengths (Figs. 3 & 4) are not seen in the in- thedustSEDafterthesynchrotroncomponenthasbeensubtracted;
frared.Atthelonger(160µm)PACSandtheSPIREwavelengths, themodelisthesumoftwomodifiedPlanckfunctionseachwitha
itisdifficulttodisentangleanySNRemissionfromthelarge-scale characteristictemperature,TwandTc(Eq.1):
interstellarstructuresextendingacrosstheregion;themapsarein- Sν =Nw×νβB(ν,Tw)+Nc×νβB(ν,Tc) (1)
creasinglydominated by unrelateddust cloudsat temperaturesof
∼16−20K.Thesoutherncloudofdustwhichisoutsidethearea whereNw andNc representtherelativemassesinthewarm
oftheblastwaveandejectaregionsisthesamecloudorginallyde- andcoldcomponent, B(ν,T)isthePlanckfunction andβ isthe
tectedinmolecularemissionbyGomezetal.(2009)at5kms−1. dustemissivityindex.ThemodelwasfittedtotheSED(constrained
The cold dust cloud in the north-east is coincident with the CO bythe12µmflux)andtheresultingparameters(Nw,Nc,Tw,Tc,
structureat10kms−1(see§5.3formorediscussion). β) which gave the minimal chi-squared were found. We also ap-
Opticalemissionarisingfromdense,knottyregionsinthecir- pliedabootstrapanalysistoourSED-fittingtodeterminetheerrors
cumstellar medium overrun by the blast wave, is traced in [NII] ontheSEDmodel.Thephotometrymeasurementswereperturbed
andHα.Interestingly,the70µmemissioncorrelateswiththeHα accordingtotheerrorsateachwavelength,thenewfluxeswerefit-
+[NII]features(Fig.4)inboththenorthernlimb(particularlyin ted in the same way, and the SED parameters recorded, with the
thenorth-westregion)andacrosstheprojectedshellalongthemid- procedurerepeated1000times.
dle.SincetheHαemissionoriginatesfromcollisional heatingof ThetotaldustmassiscalculatedusingEq.2:
trhoeuntdhiinngremgiaotenribael)h,inthdetshpeaStiNalashgorecekmfreonnttw(ii.eth.ftrhoemPAswCeSpet-mupisssiuorn- Md = S500D2 × Nw + Nc (2)
κ500 (cid:20)B(500µm,Tw) B(500µm,Tc)(cid:21)
and the ionised features suggest this dust component arises from
theswept up medium. Thisisfurther supported when comparing
the FIR with X-ray emission. There are three X-ray components 5 http://irsa.ipac.caltech.edu/data/SPITZER/docs/mips/
6 H. Gomezet al.
Figure3.Multiwavelength montageofKepler’s supernovaremnantanditsenvirons.Top:PACSandmiddle:SPIREbandscentredatRA = 262.671◦,
Dec=−21.4914◦(J2000.0;yellowcross);theregionshowis7.2′×7.2′.Thelocationoftheforwardshock(radius103′′)isindicatedwiththewhitecircle
(DeLaneyetal.2002).Alsoshownarebottom:theSCUBA850µm(Morganetal.2003);theCO(J =2−1)mapintegratedfrom−200<v<200kms−1
(Gomezetal.2009)andthe6cmVLAmap(DeLaneyetal.2002).
IRFluxesTowardsKeplerSNR(Jy)
24µm 70µm 100µm 160µm 250µm 350µm 500µm 850µm
Published 9.5±1.0a 5.6±1.4b 2.9±1.1b <0.9a .. .. 3.0±0.2c,d 1.0±0.2c
Thiswork 9.5±1.0e 12.3±2.7 11.2±2.4 16.5±2.9 13.0±2.8 5.8±1.2 2.7±0.6 0.7±0.1
Nonthermal 0.02 0.05 0.06 0.09 0.12 0.16 0.20 0.29
Table2.FluxesinJymeasuredforKepler’sremnantwithinthe120′′aperture.Notethatthepreviouspublishedintegratedfluxesusedifferentaperturesizes
tothiswork.References:a-Blairetal.(2007);b-averagevaluesfromDouvionetal.(2001),Arendt(1989)andSaken,Fesen&Shull(1992)IRASdata;c-
Gomezetal.(2009);d-450µm.e-MeasuredonSpitzerMIPSarchivedata.
whereκ500 isthedustabsorptioncoefficientandDisthedistance followBlairetal.(2007)inadoptingadistanceof4kpc.Todeter-
(wechoosethe500µmfluxsincethisislesssensitivetothetemper- minethedustmass,weuseκ500 = 0.1m2kg−1 withκ ∝ λ−β,
ature).Thedistancetotheremnantisuncertain,withmeasurements appropriate for grains inthe MilkyWay and β ∼ 1−2(Draine
ofHIabsorptionplacingKeplerat∼ 5kpc(seeReynoso&Goss &Lee1984). Thebest-fitdust masswithintheaperture obtained
1999 for a full discussion). Sankrit et al. (2008) have revised the fromtheSEDmodel(Eqs.1&2)isthereforeMw = 0.0035M⊙
measurement to 3.9+−11..94kpc using HST proper motion data. We andMc =2.2M⊙,withtemperaturesTw =84K,Tc =19Kand
Dust intheKeplerand TychoRemnants 7
Figure4.ComparisonofthewarmdustemissiontracedbyPACS70-µmdata(whitecontours)withopticalandX-ray.Left:ThreecolourimageofKepler’s
supernovaremnantwiththeHSTat658nm(red),660nm(green)and502nm(blue)indicatingemissionatHα+[NII],[NII]and[OIII]respectively. The
opticalemissionmostlyarisesfromshockedcircumstellar/interstellarmaterialinteractingwiththeprimaryblastwave.Thenorthcomponentindicatedwith
thefiducialisthoughttobeejectamaterial(Sanrkitetal.2008)whichhasoverruntheprimaryshockboundaryduetothecontactdiscontinuityintheblastwave.
Right:ThreecolourX-rayimageusingChandraarchivedatashowingsoft(0.3−0.72keV:red),(0.72−0.9keV:green)andhardX-rays(1.7−2.1keV:
blue).TheimagesarecenteredonαJ2000=262.663◦andδJ2000 =−21.485◦andare3′×3′across.
β = 1.5. The temperature of the warm component is consistent
withcollisional heating of dust intheshocked gaswithtempera-
tureandelectrondensityof1.2keVandne ∼ 20cm−3 (Bouchet
etal.2006,theirFig.15).
The median parameters and confidence intervals from the
bootstrap method are listed in Table 4. The dust mass depends
strongly on thechoice of κ, for example, typical interstellar dust
grains are described well with κ = 6.7m2kg−1 at 70µm (e.g.
Draine&Li2001).Inthiscase,thewarmdustmasswouldbere-
ducedtoMw = 1×10−3M⊙.Wenotethattheuncertaintyinκ
couldbeanorderofmagnitude.
TemperaturemapsofthedustemissiontowardsKeplerwere
createdusingtheconvolvedIR-submmmapsfrom24-500µm,and
fittinga two-temperature modified blackbody SED to each pixel.
Weextractedthewarmandcoldcomponentsforeachpixel,shown
inFig.6(a)and(b).Inordertoaccountforthenon-thermalcompo-
Figure5.TheIR-radioSEDtowardsKepler’s SNR.Thepreviouslypub-
nent,thefluxduetosynchrotronradiationwassubtractedfromthe
lished fluxes from the literature (Table 2) are shown with errors as ver-
tical bars (Spitzer = purple triangles; IRAS = blue diamonds; SCUBA = dustmapsonapixel-by-pixelbasisbeforethegreybodyfitswere
orange squares). The solid black line is the sum of the two-temperature made. The synchrotron contribution in each pixel was estimated
thermal dustcomponents fittedtotheIR(Tw = 86KandTc = 20K) usingaspectralindexmapcreatedfromthe6cmand23cmVLA
andsubmmfluxes(dot-dashedanddashedlinesrespectively).Thedot-dot- observationsconvolvedtothesamebeam(seealsoDeLaneyetal.
dot-dashedlineshowsthenon-thermalSEDexpectedfromthesynchrotron, 2002). The somewhat flatterspectral index inthe northern bright
Sν ∝ν−0.71scaledbythe6cmfluxes.TheredlineshowsthetotalSED ring(α∼−0.68comparedtotheaveragevalueof-0.71)resulted
fromthenon-thermalandthermalcomponents.Notethatthepreviouspub-
in removing most of the cold dust in this region, though there is
lishedintegratedfluxesusedifferentaperturesizestothiswork.
residualemissionassociatedwiththiscomponent withintheSNR
shell (Fig. 6(b)). This cold dust feature appears tobe coincident
withasimilarstructureseeninthewarmdust component butthe
colddustisfurtheroutfromthecentreby∼ 10′′ comparedtothe
8 H. Gomezet al.
Kepler, the interstellar dust structures are associated with atomic
ratherthanmoleculargas.
If the cold dust inthe north of the remnant islocated at the
distanceoftheremnant,thelocationoftheemissionissuggestive
ofdustsweptupbytheblastwave,thoughthemassofdustinthe
northern shell is rather substantial at ∼ 1.0M⊙ for T ∼ 20K.
Elsewhere, the cold dust component does not spatially coincide
with any of the SNR tracers including X-ray, radio and optical
emissionandisunlikelytoberelatedtotheSNitself.Wediscuss
theoriginofthecolddustfurtherin§5.3.
Finally,wealsotestedforthepresenceofcooldustwithtem-
peraturesintherange30-40KasfoundinCasA(Sibthorpeetal.
2010;Barlowetal.2010):thefluxcontributionofthewarmcom-
ponent(visibleat24µm)wassubtractedfromthe70and100µm
maps,however,wefindnoevidenceofacooldustcomponent.
4 TYCHO’SSUPERNOVAREMNANT
(a) TheTychosupernovaeventwasobservedbyTychoBrahein1572.
Itliesatadistanceof1.5−3.8kpc(Reynosoetal.1997;Krause
et al. 2008b) and has a thin shell-like morphology with diameter
∼ 8′ across. Here,weusethedistance giveninD = 3.8kpcas
this is consistent with the historical records of the explosion, the
non-detectionoftheremnantandthedistancetotheproposedbi-
narycompanion(Luetal.2011)(seeKrauseetal.2008bformore
details). The outer blast wave extends to an average distance of
251′′ from thecentre, withthe contact discontinuity between the
reverse shock material and swept up ISMat angular distances of
183,241and260′′ dependingonthepositionangle(Warrenetal.
2005).Tycho’slightechospectrumhasrevealedittohavebeena
TypeIaevent(Krauseetal.2008b);itistheremnantofacanoni-
calsingle-degeneratebinaryexplosion(Luetal.2011) asevident
fromX-rayejecta abundances (Decourchelle et al.2001). Thisis
furthersupportedbythelackofsimilarityinTycho’sopticallight
curve withtypical sub-luminous (van den Bergh1993) and over-
luminous(Ruiz-Lapuente2004)TypeIaexplosions(Krauseetal.
2008b). Badenesetal.(2006) performeddetailedcomparison be-
tweentheX-rayspectraandtheresultsfromhydrodynamicalmod-
elingofthesupernovashocks,andfoundthatthedelayeddetona-
(b) tionexplosionmodelwasthebestfittothedata.Inthisscenario,
theSNRisexpandingintoanambientdensityof∼0.6−3cm−3,
Figure6.Dusttemperaturemapsderivedfromfittingamodifiedgreybody
withanejectamassof1.3M⊙.
to the 24-500µm maps towards Kepler’s supernova remnant showing(a)
Many authors have suggested that Tycho is interacting with
warmdustand(b)colddust.ThecolourbarshowsthetemperatureinK.The
solidblackcircleindicatesthephotometryapertureusedwithradius120′′ molecular clouds (Reynoso & Goss 1999; Lee, Koo & Tatenatsu
2004; Cai, Yang & Lu 2009; Xu, Wang & Miller 2011) partic-
andtheblack dashedcircle isthe average radius ofthe outershockfront
103′′. ularly with a large CO structure seen in the north and north-east
atvelocitiesbetween-63.5and-61.5kms−1;thisstructureisbe-
lievedtoberesponsible for theasymmetryseenintheX-rayand
warm dust emission which is spatially coincident with the radio radio (see Fig. 8). Cai et al. (2009) showed that interaction with
(Fig.6(a)). theISMoccursalongtheentireboundaryoftheremnantwithin-
Thecoldduststructuresinthenortharealsocoincidentwith terstellar structures detected at velocities -69 − -58kms−1; the
thestructuresseenat850µmwiththeSCUBAcamera(Gomezet totalgasmassofcloudsinteractingwithTychois103M⊙ (Xuet
al.2009,Fig.3)originallyattributedtosupernovadustduetothe al. 2010). Conversley, Tian & Leahy (2011) propose that theCO
lackofcorrespondancebetweentheCOgasfrommolecularinter- clouds are not interacting withtheremnant sincethe densities of
stellar clouds towards Kepler (Fig. 3) and the 850µm emission. themoleculargascloudsinthenorthare∼200cm−3,comparedto
ThelargerHerschelmapclearlyshowslarge-scaleandexendedin- theX-rayejectaparameterswhichsuggesttheremnantisplough-
terstellarduststructuresrightacrosstheentireregiontowardsKe- ingintomaterialofdensity0.2−3cm−3(Decourchelleetal.2001,
plerandimpliesthatthattheargumentinGomezetal.wasflawed. Badenesetal.2006).Thedifferenceinthedensityestimatedforthe
Thiscouldsimplybeduetoanon-constantratioofmoleculargas- surroundingmaterialfromCO/X-rayabundancesisafactorof60
to-dust, or that the12COand 13COlinesarenot effectivetracers (ratherthanthethreeordersofmagnitudequotedinTian&Leahy
ofthegasinthisregion.Alternatively,itispossiblethat,towards (2011)).However,thedensityoftheHIcloudtheydetectat-43−
Dust intheKeplerand TychoRemnants 9
remnant.InFig.9,wecomparethePACS70µmemissionwitha
three-colour X-ray image (0.95-1.26, 1.63-2.26 and 4.1-6.2keV).
Theemissionfromwarmdustat70µmisboundedwithinthefor-
wardandreverseshocksoftheSNRat251′′and183′′respectively
(Warrenetal.2005) andwedonotseeFIRemissiontowardsthe
interioroftheremnant.The250µmemission(Fig.8),however,ex-
tendsfaroutsidetheshockboundaryandspatiallycorrelateswith
thelow-levelstructuresandthepeaksseenintheCOmap(Fig.10).
Theredoesn’tappeartobeanyagreementbetweenthepeaksat70
and250µmthoughweseeemissionatbothFIRwavelengthswhere
thereisalsoCOemission.ComparingwiththeCOmoleculargas,
theinterstellarcloudsseenbyHerschelclosetotheremnantinthe
north(labeledNWandNE)andtotheeast,matchstructuresseen
at−61and−65kms−1.Inthesoutheastandsouthwest,twofaint
COcloudsareseeninthesamerangeofvelocity,bothwithassoci-
ated70µmand250µmemission.
The correlation between the 70µm emission and the X-rays
emittedattheouteredgesoftheSNRisstriking.ThehardX-ray
emission(4.1-6.2keV)isfilamentaryinstructurewiththinrimsex-
tendingoutsideofthecircularedgebothinthenorthandsouth-east
sideoftheremnant.Thepeaksinthewarmdusttracethepeaksin
Figure7.Three-colourFIRimageofTycho’sSNRwithPACSdataat70,
100and160µm.Theareashownis23.2′×27.2′. thehardX-rays.TheFIRemissiondoesnotspatiallycoincidewith
thesoftX-rays(Fig.9)withpeaksinthesoftX-raylaggingbehind
the70µmpeaksby27′′inthenorthwest,thoughthesoftemission
57kms−1 is comparable to the density obtained from X-ray ob- attheedgesoftheouterblastwavedocorrelatewiththeFIR(re-
servations and could thereforebe tracing gasinteracting withthe gions‘A’and‘B’inFig.9).Thepeaksintheradioemissionalsolag
remnant. Usinga flatgalactic rotationmodel (withstandard con- by∼16′′.Theejectamaterialdoesnotspatiallycorrelatewiththe
stants)placesthisHIcloudatd=3.4kpcwhichisconsistentwith IRemission,withthepeakinthenorthwestlaggingbehindtheFIR
thedistanceofTycho’sSNR. by23′′.ThecorrelationofwarmdustwiththehardX-rayemission
Ishihara et al. (2010) detect warm dust features in the north at theedges of the remnant isslightlysurprising due tothelarge
oftheremnantwithAKARIandsuggestthesearelinkedtotheCO fractionofnon-thermalemissionexpectedfromshocksinthisen-
structuresinthenortheast.Theyalsofindenhanceddustemission ergyregime.However,dustisseenwheresoftX-rays(fromthermal
in thenorthwest region of the shell and since they find no corre- emission due tothe blast wave sweeping up interstellar material)
spondingCOfeature,theysuggestthiscomponentcouldoriginate and hard X-rays overlap. Lee et al. (2010) showed that the hard
from SN dust. Without the long wavelength data, they were un- X-raysalsocontainasignificantfractionofthermalemission,we
abletoconstraintheamountofcolddustarisingfromSNmaterial thereforeconclude that thewarmdust isspatiallycorrelatedwith
withintheblastwave. thesweptupmaterial.Thelackof70µmemissionintheSWre-
ThethreecolourHerschelPACSimageispresentedinFig.7. gionoftheremnant,wherethehardX-raysarebright,maysuggest
AsinKepler,theremnantisclearlyvisibleinblue,andtheinterstel- thattheCO(Fig.10)and250-µmstructureinthisregionorginates
larstructuresbecomecleareratthelongerPACSandSPIREwave- fromaforegroundcloudwhichisnotassociatedwiththeremnant;
lengths(Fig.8).Cold,dustycloudspeakingat250µmareseento this would mean very littleinterstellar dust is being swept up on
theimmediateeastandwestoftheremnantandhavetemperatures thisside(inagreement withthefasterexpansion rateoftheSNR
typical of the ISM. Thebright SPIREinterstellar structure to the observedinthisregion).ThehardX-raysinthewest-southwestre-
immediatenorth of theremnant inFig. 8, ishighly suggestive of gion are produced by non-thermal synchrotron emission revealed
emissionoriginatingfromgasanddustsweptupbytheexpanding by the presence of X-ray ‘stripes’ due to tangled magentic fields
SNR.Thestructureissimilarinappearancetothesubmmcavities on small scales (Eriksen et al. 2011). Here then the hard X-rays
blownoutbythewindsfromwarmOBstars(e.g.Schneideretal. aredominatedbynon-thermalprocessesandthelackofwarmdust
2010)withfilamentaryfingerspointinginwardstothecentreofthe inthisregionfurthersupportsthehypothesisthatweonlyseedust
ionisingradiation(inthiscasetheSNR).Inthehigher resolution in the shocked, swept-up ISM where we find thermal continuum
PACSdata (Fig. 7), we seethree small, warm sources embedded X-raysandHαemission-thisishighlightedinFig.11.
withintheSPIREclouds(see§4.2forfurtherdiscussion).Thecom- There is no correlation between the FIR and X-rays for the
pactbluesourcetothenorth(Fig.7)istheCepheidVariablestar, outermost ejecta material which has broken through the reverse
V∗ASCas. shockregionouttotheveryedgeoftheSNR(aslabeledinFig.9).
Weconcludethatthereisnoevidencetosuggestthatthewarmdust
isassociatedwiththeejecta.
4.1 Themultiwavelengthview
Theemissionfromwarmdustat70µminthenorthhastwobright
4.2 Thespectralenergydistribution
componentsintheNEandNW(Fig.8);seenalsointheAKARIdata
atwavelengthsoutto160µm.Thiscorrespondsspatiallytopeaks The IR-submm SED towards Tycho’s SNR is shown in Fig. 12.
in24µmemissionaswellastheX-raycontinuumwhichtracesthe ThefluxesestimatedfromSpitzerandHerschelwithinanaperture
forward blastwave. Thelonger wavelength Herschel-SPIREdata ofradius251′′centredontheremnant,areplottedwiththeirerrors
do not spatially correlate with radio or X-ray emission from the (Table 3; the zero-level offsets were applied to the maps before
10 H. Gomezet al.
Figure8.MultiwavelengthmontageofTycho’ssupernovaremnant.Fromlefttoright:top:12CO(J =1−0)dataintegratedfrom−68<v<−53kms−1),
18cmradiodataandSpitzerMIPS24µm.Middle:HerschelPACSandbottom:SPIRE.TheimagesarecentredatRA=6.3308◦,Dec=64.1372◦(J2000.0;
yellowcross)withsize9′×9′.Thelocationoftheforwardshock(radius251′′)isindicatedwiththewhitecircle.
IRFluxestowardsTychoSNR(Jy)
12µm 24µm 70µm 100µm 140µm 160µm 250µm 350µm 500µm
Published 1.8±0.8a .. 38.6±7.7b,c .. 46.7±14.0b 44.5±13.4b .. .. ..
.. 28.3±3.2b,d .. 40.6±8.1b,e .. .. .. .. ..
Thiswork .. 20.1±3.0 44.8±10.8 41.1±8.8 .. 59.0±14.1 42.7±8.6 32.8±6.5 17.6±3.5
.. 18.9±3.8f
Nonthermal .. 0.65 1.28 1.58 1.98 2.09 2.73 3.34 4.14
Table3.FluxesinJymeasuredtowardsTycho’sremnantwithinthe251′′aperturedefinedinFig.8.Referencesa-Douvionetal.2001;b-Ishiharaetal.
2010;AKARIfluxesmeasuredatwavelengths:c-65µm;d-22.9µm;e-90µm.f MeasuredonWISEdataat22µm.