First results from the CALYPSO IRAM-PdBI survey. II. Resolving the hot corino in the Class 0 protostar NGC 1333-IRAS2A

1.2 MB·

by  A. J. Maury

Astronomy&Astrophysicsmanuscriptno.ms (cid:13)cESO2014
January28,2014
LettertotheEditor
⋆
First results from the CALYPSO IRAM-PdBI survey
II. Resolving the hot corino in the Class 0 protostar NGC 1333-IRAS2A
A.J.Maury1,2,4,A.Belloche3,Ph. André4,S.Maret5,F.Gueth6,C.Codella7,S.Cabrit8,5,L.Testi2,7,9,andS.
Bontemps10,11
1 Harvard-SmithsonianCenterforAstrophysics,60Gardenstreet,Cambridge,MA02138,USA
2 ESO,KarlSchwarzschildStrasse2,85748GarchingbeiMünchen,Germany
4 3 Max-Planck-InstitutfürRadioastronomie,AufdemHügel69,53121Bonn,Germany
1 4 LaboratoireAIM-Paris-Saclay,CEA/DSM/Irfu-CNRS-UniversitéParisDiderot,CE-Saclay,F-91191Gif-sur-Yvette,France
0 5 UJF-Grenoble1/CNRS-INSU,InstitutdePlanétologieetd’AstrophysiquedeGrenoble,UMR5274,Grenoble38041,France
2 6 IRAM,300ruedelaPiscine,38406StMartind’Hères,France
n 7 INAF-OsservatorioAstrofisicodiArcetri,LargoE.Fermi5,I-50125Firenze,Italy
a 8 LERMA,CNRSUMR8112,ObservatoiredeParis,ENS,UPMC,UCP,PSL,F-75014Paris
J 9 ExcellenceClusterUniverse,Boltzmannstr.2,D-85748,Garching,Germany
10 UniversitédeBordeaux,LAB,UMR5804,F-33270Floirac,France
7
11 CNRS,LAB,UMR5804,F-33270Floirac,France
2

ReceivedNov.12,2013/AcceptedJan.22,2014
]
A
G ABSTRACT
.
h Aims. We investigate the origin of complex organic molecules (COMs) in the gas phase around the low-mass Class 0 protostar
p NGC1333-IRAS2A,todetermineiftheCOMemissionlinestraceanembeddeddisk,shocksfromtheprotostellarjet,orthewarm
- innerpartsoftheprotostellarenvelope.
o Methods.IntheframeworkoftheCALYPSO⋆⋆IRAMPlateaudeBuresurvey,weobtainedlargebandwidthspectraatsub-arcsecond
r resolution towards NGC 1333-IRAS2A. Weidentify theemission lines towards thecentral protostar and perform Gaussian fitsto
t
s constrainthesizeoftheemittingregionforeachoftheselines,tracingvariousphysicalconditionsandscales.
a Results. The emission of numerous COMs such as methanol, ethylene glycol, and methyl formate is spatially resolved by our
[
observations. Thisallowsustomeasure, forthefirsttime, thesizeof theCOMemissioninsidetheprotostellar envelope, finding
thatitoriginatesfromaregionofradius40–100 AU,centeredontheNGC1333-IRAS2A protostellarobject. Ouranalysisshows
1
nopreferentialelongationoftheCOMemissionalongthejetaxis,andthereforedoesnotsupportthehypothesisthatCOMemission
v
arisesfromshockedenvelopematerialatthebaseofthejet. Downtosimilarsizes,thedustcontinuumemissioniswellreproduced
8
withasingle power-law envelope model, and thereforedoes not favor the hypothesis that COMemission arisesfrom thethermal
9
sublimationofgrainsembeddedinacircumstellardisk. Finally,thetypicalscale∼60AUobservedforCOMemissionisconsistent
9
withthesizeoftheinnerenvelopewhereT >100Kisexpected.OurdatathereforestronglysuggestthattheCOMemissiontraces
6 dust
thehotcorinoinIRAS2A,i.e., thewarminner envelopematerial wheretheicymantlesofdust grainsevaporate because theyare
.
1 passivelyheatedbythecentralprotostellarobject.
0
4 Keywords. Stars:formation,circumstellarmatter–Complexmolecules–Interferometry–Individualobjects:NGC1333-IRAS2A
1
:
v
i1. COMemissioninClass0protostars (∼< 50–200AU)whereprotostellardisks(progenitorsofthepro-
X toplanetarydisksobservedatlaterstages)areassembledduring
rAlong the path leading to the formationof solar-typestars, the theembeddedphases,mostenvelopetracers(e.g.,12CO,N2H+)
aClass 0 phase is the main accretion phase during which most are optically thick or chemically destroyed, making it difficult
of the final stellar mass is accreted onto the central protostel-
toprobethephysicalpropertiesoftheinnerenvelopeonscales
lar object (Andréetal. 2000). It is therefore of paramountim-
whereaccretionactuallyproceeds.
portance to study the properties of the infalling envelope ma-
The origin of complex organic molecule (COM) emission
terial on all scales during the Class 0 phase. Ultimately, this
in low-mass Class 0 protostars is still debated (Bottinellietal.
willallowustoconstraintheefficiencyoftheaccretion/ejection
2007). First, it has been suggested that the emission of COMs
process to build solar-type stars and to shed light on the initial
comesfromhotcorinoregionsdeeplyembeddedinClass0pro-
conditions for the formation of protoplanetary disks and plan-
tostars, analogousto the hotcoresobservedtowardshigh-mass
ets around stars like our own. However, on the small scales
protostars (e.g., vanDishoeck&Blake 1998; Ceccarelli 2004;
Bottinellietal. 2004a). In its early stages, the central proto-
⋆ BasedonobservationscarriedoutwiththeIRAMPlateaudeBure
stellar object radiatively heats the surrounding inner envelope.
Interferometer. IRAM is supported by INSU/CNRS (France), MPG
When the temperature of the envelope material becomes high
(Germany),andIGN(Spain).
⋆⋆ CALYPSOistheContinuumAndLinesinYoungProtoStellarOb- enough(∼100K),theicymantlesofdustgrainsevaporate,lead-
jectssurvey. ingtohighgas-phaseabundancesofcomplexorganicmolecules
Articlenumber,page1of10
that are formed on dust grains (Cazauxetal. 2003; Ceccarelli usedinouranalysisofthespatialdistributionoftheCOMemis-
2007; Garrodetal. 2008). Because of the low luminosities sionpresentedinSect. 3becausetheirspatialresolutionislower
of the central protostars, the region where these molecules thanthespectraanalyzedhere(setupS2).Thesedatasetswillbe
are released is expected to be small (typically ∼< 200 AU in describedinaforthcomingpaperthatanalyzesthechemistryin
diameter;Bottinellietal. 2004b). If the COM emission indeed theIRAS2Aenvelope.
tracesthewarminnerenvelopeheatedbythecentralprotostellar
object, COM lines couldbegoodcandidatesto study the infall
3. Lineidentification
andaccretionofcircumstellarmaterialdowntotheveryvicinity
of the protostellar object itself. However, it has also been pro- We extracted the WideX spectrum at the continuum emission
posedthatCOMemissioncouldoriginatefromthewarmsurface peak (α = 03h28m55.575s, δ = 31◦14′37.05′′). The
J2000 J2000
ofembeddeddisks(Jørgensenetal.2005b),orshockedmaterial spectrum,presentedinFig.A.1,showsawealthofemissionlines
alongprotostellarjets,sincespeciessuchasCH3OHareknown whose properties are analyzed in the following. The method
to be greatly enhanced in shocks (Bachiller&PerezGutierrez used to identify the detected lines is described in Appendix A.
1997; Chandleretal. 2005) as a result of grain mantle sputter- Wereportthefirsttentativedetectionofthevibrationallyexcited
ing. state3 =1ofHNCOinalow-massprotostar(2linesdetectedin
5
TheCALYPSOsurvey1,carriedoutwiththeIRAMPlateau setupS2,seeTable1). Thesmallnumberofdetectedlinespre-
deBure(PdBI)interferometer,isprovidinguswithdetailed,ex- ventsusfromclaimingafirmdetection,buttheseidentifications
tensive observations of 17 Class 0 protostars between 92GHz are very plausible since the intensities of the lines are consis-
and232GHz. Oneofthemaingoalsofthisambitiousobserving tent with the model that fits the vibrational ground state emis-
programistounderstandhowthecircumstellarenvelopeisbeing sion of HNCO. Moreover, our data providesthe first interfero-
accreted onto the central protostellar object during the Class 0 metricdetection,in a Class 0 protostar,of deuteratedmethanol
phase. Here,weshowthatourbroadbandCALYPSOobserva- (CH DOH: 4 lines detected in setup S2 and 14 lines detected
2
tionsoftheClass0protostarNGC1333-IRAS2A(d ∼ 235pc; insetupsS1/S3),ethyleneglycol(aGg′-(CH OH) : 5linesde-
2 2
Hirotaetal.2008)providedirectimagingofnumerousemission tectedinsetupS2and11linesdetectedinsetupsS1/S3),anda
lines,spatiallyresolvingtheCOMemissionstructureandthere- tentativedetectionforformamide(NH CHO:1lineinsetupS1
2
foreputtingstrongconstraintsonitsorigin. and1lineinsetupS2).
2. Observationsanddatareduction 4. Modelingofthevisibilities
The Class 0 protostar NGC 1333-IRAS2A(hereafter IRAS2A, The PdBI 1.4 mm dust continuum emission map is shown as
seealsoJenningsetal.1987;Looneyetal.2000)wasobserved contoursin Fig.1(a). The present analysis only focuses on the
withtheIRAM-PdBI,at218.5GHz,usingtheWideXbackends emission associated with IRAS2A (MM1); the two secondary
to coverthe full 3.8GHz spectralwindowat low spectralreso- continuumsourcesseenat[1′.′53,−1′.′49](MM2,15mJy/beam)
lution. Higher resolutionbackendswere placed ontoa handful and [−0′.′92,−2′.′21] (MM3, 21 mJy/beam) were fitted as com-
of molecularemission lines: two letters presentthe analysis of pactsourcesandremovedfromthecontinuumvisibilitytable.
thesedata,usedtoexplorethekinematicsintheinnerenvelope Theresultingrealpartofthecontinuumvisibilityofthecen-
(with methanol lines, Maret et al.) and the jet properties from tralsourceisplottedinFig.1(b)asafunctionofuvradius. The
molecularlineemission(withSOandSiOlines,Codellaetal.). flux on baselines ∼ 200kλ is only half that predicted by inter-
A-array observations were obtained during two observing ses- polationof previousdata on the same baselinesat90 GHz and
sions,respectivelyinJanuaryandFebruary2011,whileC-array 345GHz (Looneyetal. 2003; Jørgensenetal. 2005a); this dif-
observationswerecarriedoutinDecember2010. Thebaselines ferencecouldbeduetosecondarysourcesoffsetfromthephase
sampledin ourobservationsrangefrom19m to 762m, allow- center, which were not removed (or well resolved) in earlier
ing us to recoveremission on scales from ∼ 8′′ down to 0′.′35. studiesandintroducedapositivebiasinthevisibilityamplitudes
Calibrationwascarriedoutfollowingstandardprocedures,using usedbytheseauthors. Figure1(b)alsorevealsthattherealpart
CLICwhichispartoftheGILDAS2software.ForbothAtracks, of the continuum visibility of the central IRAS2A source ex-
phasewas stable (rms<50◦) andpwvwas 0.5–1mmwith sys- hibits a smooth decline all the way out to our longest baseline
temtemperatures∼100-160K,leadingtolessthan30%flagging of ≃ 550kλ, with no sign of residual positive flux on resolved
in the dataset. For the C track, phase rms was <80◦, pwv was scales. We therefore performed a simple power-law fit to the
1–2mm,andsystemtemperatureswere∼150-250K,leadingto continuumvisibilities of the centralsource, shown in Fig.1(b).
lessthan10%flaggingintheresultinguv-table. IntheRayleigh-Jeansapproximationandforoptically-thindust
emission, if the temperature and density in the envelope fol-
Wemergedthedatasetstocreatethefinalvisibilitytablefor
low simple radial power laws ρ ∝ r−p and T ∝ r−q, the emer-
the spectra towards IRAS2A. The continuum was built by us-
gentdustcontinuumemissionalsohasasimplepower-lawform
ingtheline-freechannels,thencontinuumvisibilitiesweresub-
I(r) ∝ r−(p+q−1). Forinterferometricobservations,thevisibility
tracted fromthe datasetto create a purespectralcubecovering
distributionisV(b) ∝ b(p+q−3),solelydeterminedbythepower-
frequenciesbetween216.85GHzand220.45GHzwithaspec-
tralresolutionof3.9Mhz(∼2.7 kms−1). Usingnaturalweight- law indices of the temperature and density profiles in the en-
ing,thesynthesizedFWHMbeamis∼ 0′.′8×0′.′7, withanrms velope. We find that a power-law functionV(b) ∝ b(−0.45±0.05),
noiseof∼3mJy/beamintheline-freechannelsofthespectra. shownasagreenlineinFig.1(b),reproduceswellboththecon-
tinuum emission visibility profile obtained from PdBI and the
The line identification also used two additional CALYPSO
single-dish flux (0.85 Jy; Motte&André 2001). The contin-
PdBIdatasets, consistingofwidebandspectraaround231GHz
uumemissiondowntor∼35AUcanthereforebereproducedby
(setup S1) and 93 GHz (setup S3). These observationsare not
aprotostellarenvelopemodelwithouttheneedforanadditional
1 Seehttp://irfu.cea.fr/Projets/Calypso/ large (200–300AU diameter) disk component, previously sug-
2 http://www.iram.fr/IRAMFR/GILDAS gested by Jørgensenetal. (2005a). The residuals map shown
Articlenumber,page2of10
A.J.Mauryetal.:ResolvingthehotcorinointheClass0protostarNGC1333-IRAS2A
Fig.1. (a)CH OCHOat216.966GHz(backgroundimage)andcontinuumaround219GHz(contours)emissionmapstowardsIRAS2A.The
3
rmsnoiselevelisσ=1.5mJy/beaminthecontinuum,andσ=2.8mJy/beamintheCH OCHOmap(emissionfromone2.7kms−1-channel).
3
Contoursarelevelsat3σ,5σ,8σandthenfrom10σto100σin10σincrement. Thesynthesizedbeamis0′.′8×0′.′68(P.A.32◦). Theredand
blue arrows show the direction of the main bipolar jet axis (Jørgensenetal. 2007). (b) Continuum (real part of the visibilities, black points)
andcorrespondingbest-fitpower-lawmodel(greendashedline)averagedoverbaselinebinsof10m,asafunctionofbaselinelength. Residuals
areshownasaredline. Thezero-spacingfluxisextrapolatedfromthesingle-dishfluxat850µmbyMotte&André(2001). (c): Realpartof
the visibilities (black points) from the CH OCHO (20 0 20 2 - 19 1 19 1) emission line and corresponding best-fit Gaussian model (FWHM
3
0′.′47×0′.′40,P.A41◦,greenline).Residualsareshownasaredline.
inelectronicFig.1(a)indeedshowsthatonlytheasymmetryon tostar. However, Jørgensenetal. (2007) used the Submillime-
the eastern side of the envelope was not fitted properly by our ter Array(SMA)to observethe IRAS4A protostarandshowed
power-lawmodel. Wenotethatour(p+q)value(∼ 2.55)isin that CH OH and H CO emission is extended along the out-
3 2
agreementwiththeprotostellarenvelopeprofileofIRAS2Aon flow axis; and SMA observations of I16293 detected a wealth
largerscales(p+q ∼ 2.6)proposedfromBIMA2.7mmobser- of COM emission lines (Bisschopetal. 2008; Jørgensenetal.
vations(Looneyetal.2003). 2011),mostlyunresolved. Pinedaetal.(2012)andZapataetal.
Table1liststhespatialextentoftheemissionofeachiden- (2013) used ALMA observationsofI16293to analyzethe spa-
tifiedlinethatisdetectedwithamediumorhighsignal-to-noise tial and velocity distribution of 3 COM lines, and trace the in-
ratiotowardsIRAS2A.Owingtoexcitationandabundancevari- fall on small scales aroundsource B. Observationsof IRAS2A
ations, theline emission is unlikelyto followa power-lawpro- withanangularresolutionof∼2′′ detectedemissionlinesfrom
filesimilartothedustcontinuumemission. Thereforewemod- five COMs, all spatially unresolved (Jørgensenetal. 2005a).
eled the visibilities with elliptical Gaussians and point sources Perssonetal. (2012) and Kristensenetal. (2012) detected wa-
to determinethe emittingsize ofeachof thesemolecularlines. ter emission in the IRAS2A envelope and outflow, both at the
We note that most of the lines are not spectrally resolved: the systemicandblue-shiftedvelocities.
fit was performed on the emission in the channel showing the Thankstothebandwidth,sensitivity,andresolutionofPdBI,
greatestflux to avoid possible contaminationfrom neighboring emission from large samples of COMs can now be mapped in
lines; in most cases this is the channelat the systemic velocity theveryinnerprotostellarenvelope:ouranalysisshowsthattens
ofthecore. AnexampleofthismodelingisshowninFig.1(c). ofhighexcitation(Eup ∼> 100K)emissionlinesaredetectedand
Thebestfitwaskeptwhenachi-squareminimizationconverged, spatiallyresolvedinourPdBIdata. Theyprobevariousphysical
complementedbyavisualinspectionoftheresidualsmaps(see conditions(excitationtemperaturesrangefrom∼30Kto250K
electronicFig.1(b)foranexample)toensurethatnosignificant for CH OH and HNCO) and a wide range of upper-level en-
3
emissionwasleftaroundtheIRAS2Asource.Theparametersof ergies, therefore allowing us to spatially resolve the hotcorino
thebest-fitmodelforeachidentifiedmolecularlinearegivenin emissioninIRAS2A,forthefirsttime.Theemittingsizesofthe
Table2. Forthelineswhoseemissionmorphologyisdominated molecules detected towards IRAS2A are shown in Fig.2. All
byoutflow-orjet-likestructures(SiOandSOmainly),nosatis- COMs are observed in the inner envelope at radii ∼< 100AU.
factoryfitoftheircomplexspatialdistributionswasfoundwith The best fit reproducingthe dependencyof emitting sizes with
ellipticalGaussianmodels,andvaluesarenotreported. upper-levelenergiesofthemoleculartransitionsisapowerlaw
FWHM ∝ E−0.25±0.05. However,theexactslopeofthiscorrela-
up
tionisnotverytightlyconstrainedbecauseofthelimitednum-
5. Discussion: originoftheCOMemission
berofhighsignal-to-noiselines,andafitwithaconstantradius
of 55 AU yields a only marginally higher χ2. The exact de-
ItisstillbeingdebatedwhetherCOMemissionlinesobservedin
pendenceoftheemittingregionradiuswith E willhavetobe
low-massClass0protostarsaretracingembeddeddisks,shocks up
exploredwithmoreCOMlinesdetectedwithahighersignal-to-
from protostellar jets, or the warm inner parts of protostellar
noise ratio. However, we note that the highest excitation lines
envelopes. Bottinellietal. (2004a) observedthe Class 0 proto-
that we spatially resolve are all located inside a region of ra-
star IRAS16293 (I16293 in the following) with the PdBI and
dius r ∼40 AU (average FWHM∼ 0.34′′ for transitions with
found that the emission of CH CN and CH OCHO was unre-
3 3
300K< E <800K).
solved on 180AU scales, while observationsof the NGC1333- up
IRAS4AprotostarshowedthattheCH CNemissioncomesfrom Modeling the PdBI continuum data, we find that the dust
3
aregion∼175AU(FWHM)indiameter(Bottinellietal.2008). continuum emission is well described by a protostellar enve-
These observations also showed that emission from CH CN lope with a single power-law profile I(r) ∝ r−1.55 (see Sect.3
3
and CH OCHO is not detected on large scales along the out- andFig.1b),downtophysicalsizes(r ∼ 35AU)probedbyour
3
flow axis but only on small scales around the embedded pro- longestbaselines.Thissuggeststhat,onscaleswheretheCOMs
Articlenumber,page3of10
fore it is very unlikely that these molecules are formed from
non-thermaldesorptionmechanismsdue to the interaction of a
collimatedhigh-velocityjetwith the surroundingenvelopema-
terial,assuggestedbyÖbergetal.(2011). Insteadthekinemat-
ical and spatial distribution information from our data draw a
picturewheretheCOMemissionoriginatesfromwarmmaterial
surroundingtheprotostaranddynamicallyassociatedtothepro-
tostellar envelope: the so-called hot corino region. This opens
uptheperspectiveofusingcomplexmoleculesastracersofthe
innerenvelopekinematics, downto the ∼< 100AU sizes where
rotationally-supported protostellar disks may form, and accre-
tionproceedsontheprotostaritself. Inarelatedpaper,wemake
useofthehighspectralresolutionobservationsoftwomethanol
emissionlinestoassesstheirkinematicalproperties(Maretetal.
2014).
To conclude, our results strongly support a scenario where
the COM emission in IRAS2A originates from a hot corino,
Fig.2. Emissionsize(averageradiusofthebest-fitellipticalGaussian) i.e., the release of complex molecules in the gas phase of the
ofthemolecularlineslistedinTable2asafunctionoftheirupper-level inner(∼< 100AU) envelope,whena criticaltemperatureallow-
energy.Onlythespatiallyresolved,unblendedlinesforwhichagoodfit ing sublimation of icy grain mantles is reached, and not from
couldbeachievedarerepresented. Blacksymbolsshowthemolecules
shocks at the base of the jet. Analysis of the CALYPSO ob-
forwhichonlyoneemissionlineisobserved and/or resolvedinsetup
servationstowardtheremaining16Class0 objectsin oursam-
S2,whilecoloredsymbolsshowmoleculesforwhichseverallinesare
plewillenhancethestatistics ontheoccurrenceofCOM emis-
detected andresolved. Theerror barsarethelargest error bar (minor
sionin Class 0 protostars, anddetermineif theyalways trace a
or major axis) produced by the fit with an elliptical Gaussian model.
Thepinklineshowsthebestpower-lawfittothedata,asdescribedin hot corino in the warm inner envelopeof these objects. If this
the text. All COM lines that are resolved emit in a region of radius is the case, the analysis of spectral emission lines from com-
∼< 100AU. plexmoleculeswillbeapowerfultoolfortracingtheprotostel-
larkinematicsduringthediskformationepoch,onscaleswhere
protoplanetarydisksareobservedatlater(e.g.,T-Tauri)stages.
emit, the dust emission is still predominantlyassociated to the
Acknowledgements. WethankHolgerMüllerforthespectroscopicpredictions
envelopeandnottoaprotostellardisk.SincemostCOMsarere- ofHNCO,35=1. WeareverythankfultotheIRAMstaff,whosededicational-
leasedfromdustgrains,itsuggeststhattheCOMsarereleased lowedustocarryouttheCALYPSOproject.Thisresearchhasreceivedfunding
in the warm inner envelope around the central protostellar ob- fromtheEuropeanCommunity’sSeventhFrameworkProgramme(/FP7/2007-
ject. Moreover,theobservedsizeofr 40-100AUfortheCOM 2013/) under grant agreements No 229517 (ESO COFUND) and No 291294
(ORISTARS).S.M.acknowledgesthesupportoftheFrenchAgenceNationale
emissioninIRAS2Aisingoodagreementwithpredictionsfrom
delaRecherche(ANR),underreferenceANR-12-JS05-0005.
simple analytical models computing the size of the hot corino
regionatT ∼> 100K:ifweassumeadensityprofileρ∝r−1.5for
theenvelope,andwith(p+q−1)=1.55(seeSect.3),theradius
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AppendixA: Lineidentification
We extracted the WideX spectrum at the continuum emission
peak (α = 03h28m55.575s, δ = 31◦14′37.05′′) shown
J2000 J2000
in Fig.A.1. The line identification was performed with the
XCLASS software3 under the assumption of local thermody-
namicequilibrium. Ourspectroscopicdatabasecontainsallen-
tries of the CDMS (Mülleretal. 2005) and JPL (Pickettetal.
1998)catalogs,aswellasafewprivateentries(formoredetails,
seeBellocheetal.2013). Thespectraweremodeledspeciesby
species. For most species, an excitation temperature of 100K
wasassumedfortheLTEmodeling,whileforafewspeciesthe
detectionofseveraltransitionswithsignificantlydifferentupper-
levelenergiesallowedus to leave the temperatureas a free pa-
rameterofourmodeling(findingtemperaturesupto∼250Kfor
CH OH and HNCO, for example). For each species, the spec-
3
tra in all three frequency setups were modeled at once, using
five parameters: source size, temperature, column density, line
width, and velocity offset with respectto the systemic velocity
of the source. The emission of all transitions was assumed to
come from a source of size 0′.′6 (average FWHM, see Sect.3).
The fit optimization was performed by eye. For a few species
(SO,SiO,CO),itwasnecessarytoincludeseveralvelocitycom-
ponentstoaccountfortheshapeofthedetectedlines. Atotalof
86emissionlineswithpeaksignal-to-noiseratioshigherthan3
weredetectedatthepositionofthecontinuumemissionpeak,in
setupS2,amongwhich55areidentified,seeTable1.
3 Seehttp://www.astro.uni-koeln.de/projects/schilke/XCLASS.
Articlenumber,page5of10
Fig.A.1. Continuum-subtractedWideXspectrumaround218.5GHz(setupS2),atthepositionofthemaximumof1.4mmcontinuumemission
towardsIRAS2A(showninFig.1a).
Articlenumber,page6of10
A&A–ms,OnlineMaterialp7
Table1.Listofemissionlinesdetectedatthepeakofthedustcontinuumemissionat219GHztowardsIRAS2A
Frequencya S/Nb Identificationc Quantumnumbers
(MHz)
216879 low ?
216947 high CH OH 5140-4220
3
+?
216966 high CH OCHO 200202-191191
3
200200-191190
201201-191191
201200-191190
200202-190192
200200-190190
201201-190192
201200-190190
217045 high ?
217108 high SiO 50-40
217118 high SiO 50-40
217123 high SiO 50-40
217133 high SiO 50-40
+aGg′-(CH OH) 214170-204161
2 2
217192 high CH OCH 224193-223203
3 3
224195-223205
224191-223201
224190-223200
217238 high DCN 3-2
217263 low ?
217300 high CH OH,3 =1 615-1-726-1
3 t
217359 medium CH DOH 174142-165121
2
217400 high ?
217450 high CH DOH 181172-182170
2
+aGg′-(CH OH) 241240-231231
2 2
240240-230231
217492 high ?
217588 low aGg′-(CH OH) 212191-202180
2 2
217643 high CH OH,3 =1 15610-1-16511-1
3 t
15691-165121
217804 low ?
217887 high CH OH 201190-200200
3
218022 low ?
218067 high ?
218127 high ?
218156 high ?
218181 high ?
218199 medium ?
218222 high H CO 303-202
2
218281 high CH OCHO 173142-163132
3
218298 high CH OCHO 173140-163130
3
218317 high CH DOH 5241-5151
2
218325 high HC N 24-23
3
218389 high ?
218441 high CH OH 4220-3120
3
218459 high NH CHO 1019-918
2
218469 low ?
+aGg′-(CH OH) 221480-211471
2 2
221490-211481
218476 high H CO 322-221
2
218482 high ?
218498 low ?
218554 low ?
218575 high aGg′-(CH OH) 221390-211381
2 2
2213100-211391
218708 high ?
+aGg′-(CH OH) 2212100-211291
2 2
2212110-2112101
218760 high H CO 321-220
2
218861 low HC N,3 =1 24-1-231
3 7
218903 high OCS 18-17
218981 high HNCO 10110-919
A&A–ms,OnlineMaterialp8
Table1.Continued
Frequencya S/Nb Identificationc Quantumnumbers
(MHz)
219089 medium aGg′-(CH OH) 2210130-2110121
2 2
2210120-2110111
219174 medium HC N,3 =1 241-23-1
3 7
219242 medium ?
219263 low ?
219276 low SO 22715-23618
2
219385 medium aGg′-(CH OH) 229140-219131
2 2
229130-219121
219398 low ?
219410 low ?
219441 low ?
219474 low ?
219540 medium HNCO,3 =1 10110210-91929
5
+aGg′-(CH OH) 222211-212200
2 2
219551 high HNCO 1047-946
1046-945
+CH DOH 5151-4141
2
219560 high C18O 2-1
219580 low aGg′-(CH OH) 221211-211200
2 2
219656 high HNCO 1038-937
1037-936
219719 low ?
219735 high HNCO 1029-928
1028-927
219765 medium aGg′-(CH OH) 204161-194150
2 2
219798 high HNCO 10010-909
219803 high ?
+aGg′-(CH OH) 228150-218141
2 2
219825 low ?
+CH OCHO,3 =1 181083-171073
3 t
181093-171083
219892 low ?
219908 high H 13CO 312-211
2
219950 high SO 56-45
219965 medium SO 56-45
219984 high CH OH 253220-244200
3
219994 high CH OH 235190-226170
3
220030 low ?
+CH OCHO,3 =1 18993-17983
3 t
189103-17993
220038 high t-HCOOH 10010-909
220072 high CH DOH 5150-4140
2
220079 high CH OH 8080-7160
3
220126 medium ?
220153 low HNCO,3 =1 10010210-90929
5
220167 high CH OCHO 174132-164122
3
+HNCO,3 =1 1037210-93629
5
1038210-93729
220178 high CH CO 11111-10110
2
220191 high CH OCHO 174130-164120
3
220195 medium ?
+HNCO,3 =1 1029210-92829
5
220296 low ?
220332 high ?
220343 low ?
220363 medium ?
220369 low ?
220402 high 13CO 2-1
+CH OH 10-550-11-480
3
+aGg′-(CH OH) 227160-217151
2 2
Notes.aObservedfrequencyoftheemissionline.bPeaksignal-to-noiseratioofthe(tentatively)detectedline.Highmeans>9,mediumbetween
9and6,andlowbetween6and3. cAquestionmarkmeansanunidentifiedline. Amoleculenameaccompaniedbyaquestionmarkreferstoa
partiallyunidentifiedline:anidentifiedmoleculeemitsatthefrequencyofthedetectedline;howeveritspredictedlineintensityisweakerthanthe
observedoneandthustheremustbecontributionfromanother(unidentified)species. Alllinesseparatedby ∼< 4MHzareblendedinourWideX
data.
A&A–ms,OnlineMaterialp9
Table2.PropertiesofidentifiedemissionlinesdetectedtowardthecontinuumpeakemissionofIRAS2Aaround219GHz
Restfrequency Moleculea E b Size(FWHM)c P.A.d Fluxe n f
up crit,100K
(MHz) (K) (arcsec) (◦) (Jy/beam) (cm−3)
216945.60 CH OH(+?) 56 0.7×0.4(±0.03) 30 0.51 7.1e6
3
216966.65 CH OCHO 111 0.47×0.40(±0.05)⋆ 41 0.25
3
217104.98 SiO 31 - - - 4.7e6
217193.17 CH OCH 253 0.48×0.15(±0.1) 33 0.04
3 3
217238.53 DCN 21 1.13×0.56(±0.07)⋆ 34 0.37
217299.20 CH OH,3 =1 374 0.5×0.3(±0.03)⋆ 41 0.40
3 t
217359.28 CH DOH 277 0.9×0.3(±0.3) −45 0.04
2
217447.90 CH DOH(+aGg′-(CH OH) ) 265 point 0.043
2 2 2
217642.86 CH OH,3 =1 746 0.46×0.23(±0.05) 62 0.14
3 t
217886.39 CH OH 508 0.51×0.33(±0.04)⋆ 48 0.30
3
218222.19 H CO 20 1.4×0.8(±0.05)⋆⋆ 25 0.83 5.0e6
2
218280.90 CH OCHO 100 0.45×0.35(±0.1) −31 0.07
3
218297.89 CH OCHO 100 0.41×0.20(±0.09) 21 0.09
3
218316.39 CH DOH 33 0.64×0.29(±0.1) −36 0.09
2
218324.71 HC N 131 0.75×0.45(±0.05)⋆ 21 0.19
3
218440.05 CH OH 45 0.79×0.50(±0.03)⋆ 27 0.81 7.8e7
3
218459.65 NH CHO 61 0.34×0.20(±0.07)⋆⋆ 72 0.1
2
218475.63 H CO 68 1.0×0.60(±0.03)⋆⋆ 22 1.0 5.6e6
2
218574.68 aGg′-(CH OH) 207 0.88×0.25(±0.3) 40 0.05
2 2
218705.81 (?+)aGg′-(CH OH) 195 point 0.04
2 2
218760.07 H CO 68 1.0×0.70(±0.03)⋆⋆ 21 0.96 6.1e6
2
218903.35 OCS 100 0.9×0.6(±0.02)⋆ 25 0.89 4.0e5
218981.17 HNCO 101 0.45×0.26(±0.05)⋆ 35 0.21 8.2e7
219089.73 aGg′-(CH OH) 173 point 0.04
2 2
219173.75 HC N,3 =1 452 point 0.03
3 7
219385.18 aGg′-(CH OH) 164 point 0.03
2 2
219540.33 HNCO,3 =1(+aGg′-(CH OH) ) 902 point 0.04
5 2 2
219547.09 HNCO(+CH DOH) 709 point 0.03
2
219551.48 CH DOH(+HNCO) 26 0.57×0.26(±0.09) 61 0.12
2
219560.35 C18O 16 5.0×4.0(±0.15) −80 3.0 9.6e3
219580.67 aGg′-(CH OH) 122 point 0.03
2 2
219656.71 HNCO 448 0.38×0.10(±0.09)⋆ 23 0.08
219733.85 HNCO 228 0.59×0.14(±0.07) 39 0.15
219764.92 aGg′-(CH OH) 113 point 0.03
2 2
219798.32 HNCO 58 0.60×0.27(±0.05)⋆ 37 0.24 7.6e6
219803.67 (?+)aGg′-(CH OH) 156 point 0.05
2 2
219908.48 H 13CO 33 0.93×0.57(±0.05) 19 0.34
2
219949.44 SO 35 - - - 3.7e6
219983.99 CH OH 802 0.31×0.18(±0.1) 53 0.08
3
219993.94 CH OH 776 0.31×0.11(±0.1) 63 0.07
3
220038.07 t-HCOOH 58 0.39×0.07(±0.11)⋆ 33 0.10
220071.80 CH DOH 17 0.65×0.44(±0.05) 42 0.31
2
220078.49 CH OH 97 0.63×0.43(±0.03)⋆ 25 0.65 2.9e7
3
220166.88 CH OCHO(+HNCO,3 =1) 103 0.71×0.20(±0.08) 55 0.08
3 5
220178.19 CH CO 46 0.60×0.53(±0.07) 85 0.16
2
220190.28 CH OCHO 103 0.72×0.27(±0.11) 55 0.08
3
220193.86 (?+)HNCO,3 =1 967 0.60×0.39(±0.16) −5 0.07
5
220398.68 13CO(+CH OH) 16 9.5×5.4(±0.30) 47 3.6 9.7e3
3
220401.37 CH OH(+13CO) 252 0.45×0.25(±0.04) 48 0.28 9.3e6
3
Notes. aMoleculeidentifiedtobethesourceofthelineemission. WhentwolinesaretoocloseinfrequenciestobeseparatedwiththeWideX
channelwidth,thesecondaryspectrallineisindicatedinparentheses.
bUpper-levelenergyofthetransition.
cSizeofthebestfitofanellipticalGaussiantothevisibilities,seetextforfurtherdetails.Gaussianfitswereperformedonthechannelshowingthe
maximumemission(ourdatahasaspectralresolutionof3.9MHz∼2.7 kms−1). MostlinesaredetectedatthesystemicvelocityV ∼7(±0.5)
sys
kms−1.Twonotablelinesshowseveralblue-shiftedvelocitycomponents:SiOshowsemissionat7,3,-14.5,and-32.5kms−1,whileSOisdetected
atvelocities6.5,-0.5,and-14.0kms−1.NoFWHMisindicatedwhenthemolecularemissionisdominatedbyanoutflow-orjet-likestructure,as
determinedbyapreliminaryinspectionoftheemissionmapslineperline. The⋆symbolindicatesthepresenceofasecondarycomponenttobe
fittedatadifferentpositioninthemap. The⋆⋆ symbolindicatesthat,inadditiontothecomponenttowardsIRAS2Athelinealsotracesoutflow
and/orcomplexstructuresatotherlocationsinourmaps.
dPositionangleoftheellipticalGaussian,whenanellipticalGaussianfitcouldbeperformedsuccessfully.
eFluxattributedtothebestfitwithaGaussiancomponentlocatedatthecenteroftheprotostellarenvelope.
fCritical density of the transition, computed at 100K, using the collision rates compiled in the LAMDA database when available.
http://home.strw.leidenuniv.nl/~moldata/
A&A–ms,OnlineMaterialp10
Fig. 1. Emission and residual maps of the continuum emission and CH OCHO line emission at 217GHz. (a) The left and right panels,
3
respectively,showthePdBIcontinuumemissionmapandresidualsmap.Theresidualsmapwasobtainedbyremovingthetwosecondarysources
aspointsources,thenremovingthebest-fitpower-lawmodelvisibilitiesfromthedatavisibilities,andimagingtheresidualstable.Contoursshow
thelevelsof3σ,5σ,and8σ,andthen10σto100σin10σsteps. Thecrossshowsthephasecenterofourobservations,coincidingwiththepeak
ofthecontinuumemissionat1.4mm. (b)Theleftandrightpanels,respectively,showtheCH OCHOemissionandresidualmaps. Inthemaps,
3
thermsnoiselevelisσ=2.8mJy/beam.Contoursshowthe3σ,5σ,and8σ,andthen10σto60σin10σsteps.