Glycolaldehyde in Perseus young solar analogs

0.8 MB·

by  M. De Simone

Astronomy&Astrophysicsmanuscriptno.desimone (cid:13)cESO2017
January4,2017
⋆
Glycolaldehyde in Perseus young solar analogs
M.DeSimone1,C.Codella1,L.Testi1,2,3,4,A.Belloche5,A.J.Maury6,S.Anderl7,8,Ph.André6,S.Maret7,8,andL.
Podio1
1 INAF,OsservatorioAstrofisicodiArcetri,LargoE.Fermi5,50125Firenze,Italy
2 ESO,KarlSchwarzchildStr.2,85748GarchingbeiMünchen,Germany
3 ExcellenceCluster‘Universe’,Boltzmannstr.2,D-85748GarchingbeiMuenchen,Germany
4 GothenburgCenterforAdvanceStudiesinScienceandTechnology,DepartmentofMathematicalSciences,ChalmersUniversity
ofTechnologyandUniversityofGothenburg,SE-41296Gothenburg,Sweden
7 5 Max-Planck-InstitutfürRadioastronomie,AufdemHügel69,53121Bonn,Germany
1 6 LaboratoireAIM-Paris-Saclay,CEA/DSM/Irfu-CNRS-UniversitéParisDiderot,CESaclay,91191Gif-sur-YvetteCedex,France
0 7 Univ.GrenobleAlpes,CNRS,IPAG,38000,Grenoble,France
2 8 CNRS,IPAG,38000,Grenoble,France

n Receiveddate;accepteddate
a
J
ABSTRACT
3

Context.Theearliestevolutionarystagesoflow-massprotostarsarecharacterisedbytheso-calledhot-corinostage,whenthenewly
]
R bornstarheatsthesurroundingmaterialandenrichthegaschemically.Studyingthisevolutionaryphaseofsolarprotostarsmayhelp
understandtheevolutionofprebioticcomplexmoleculesinthedevelopmentofplanetarysystems.
S
Aims.In this paper we focus on the occurrence of glycolaldehyde (HCOCH OH) in young solar analogs by performing the first
2
h. homogeneousandunbiasedstudyofthismoleculeintheClass0protostarsofthenearbyPerseusstarformingregion.
p Methods.Weobtainedsub-arcsecangularresolutionmapsat1.3mmand1.4mmofglycolaldehydeemissionlinesusingtheIRAM
- PlateaudeBure(PdB)interferometerintheframeworkoftheCALYPSOIRAMlargeprogram.
o Results.Glycolaldehydehasbeendetectedtowards3Class0and1ClassIprotostarsoutofthe13continuumsourcestargetedin
r Perseus:NGC1333-IRAS2A1,NGC1333-IRAS4A2,NGC1333-IRAS4B1,andSVS13-A.TheNGC1333starformingregionlooks
t
s particularly glycolaldehyde rich, with a rate of occurrence up to 60%. The glycolaldehyde spatial distribution overlaps with the
a continuumone,tracingtheinner100auaroundtheprotostar.Alargenumberoflines(upto18),withupper-levelenergiesE from
u
[ 37Kupto375Khasbeendetected.Wederivedcolumndensities≥1015 cm−2 androtationaltemperaturesT between115Kand
rot
236K,imagingforthefirsttimehot-corinosaroundNGC1333-IRAS4B1andSVS13-A.
1
Conclusions.In multiple systems glycolaldehyde emission is detected only in one component. The case of the SVS13-A+B and
v
IRAS4-A1+A2systemssupportthatthedetectionofglycolaldehyde(atleastinthepresentPerseussample)indicatesolderprotostars
4
(i.e.SVS13-AandIRAS4-A2),evolvedenoughtodevelopthehot-corinoregion(i.e.100Kintheinner100au).However,onlytwo
2
systems do not allow us to firmlyconclude whether the primary factor leading to the detection of glycolaldehyde emission isthe
7
environmentshostingtheprotostars,evolution(e.g.lowvalueofL /L ),oraccretionluminosity(highL ).
0 submm int int
0 Key words. Stars: formation – ISM: jets and outflows – ISM: molecules – individual objects: NGC1333-IRAS2A, –IRAS4A,
. –IRAS4B,andSVS13-A
1
0
7
11. Introduction in the chemical processes leading to ribose (e.g. Weber 1998;
: Jalboutetal.2007),inturnthebackboneofterrestrialRNA.
vThe gas surrounding a new born star can reach temperatures
i The first detection of interstellar glycolaldehydewas made
Xhigherthan100K,dueto thermalheatingbythe protostar(the
in the hot core Sagittarius B2(N) located in the high-mass star
so called hot-corinossee e.g. Ceccarelli et al. 2007) as well as
r formingregionSagittariusB2closetotheGalacticCentre(Hol-
ashocksproducedby both accretionand ejectionprocesses (e.g.
lis et al. 2000, 2004; Halfen et al. 2006; Requena-Torreset al.
Codellaetal.2009;Sakaietal.2014).Inturn,suchtemperatures
2008). Later on, Beltrán et al. (2009) imaged glycolaldehyde
favourarichcomplexorganicchemistry,withaconsequentdra-
emissionforthefirsttimetowardsastarformingregion,namely
matic increase of the abundance of the so-called Complex Or-
the massive hot core (the scaled-up version of a hot-corino)
ganic Molecules (COMs; i.e. organicmoleculeswith at least 6
G31.41+0.31, while Calcutt et al. (2014) reported glycolalde-
atoms detected in space, Herbst & van Dishoeck 2009), which
hyde towards further hot cores. However, the large distance of
can be considered the first bricks to build biologically relevant
theobservedhigh-massstarformingregions(≥1kpc)hampers
molecules.AmongtheCOMs,glycolaldehyde(HCOCH OH)is
2 (i)toassessareliableassociationwithoneormoreyoungstellar
thesimplestsugar-likemoleculeanditisexpectedtobeinvolved
objectsduetomultiplicity,and(ii)ananalysisonspatialscales
comparable to that of a protoplanetary disk (i.e. ∼ 100 au). In
Send offprint requests to: C. Codella, e-mail:
[email protected] addition, the study of the formation and evolution of complex
⋆ BasedonobservationscarriedoutwiththeIRAMPlateaudeBure organic molecules (including glycolaldehyde) in young Solar
interferometer. IRAM is supported by INSU/CNRS (France), MPG analogsisessentialtounderstandthepotentialofformationand
(Germany),andIGN(Spain) evolutionofpre-bioticmaterialinthesesystems.
Articlenumber,page1of24
A&Aproofs:manuscriptno.desimone
Jørgensenetal.(2026)reportedthefirstdetectionofglyco- lines2 wereobservedusingtheWideXbackendtocovertwo4-
laldehydeemissionwithALMAtowardstheyoungSolaranalog GHz spectralwindows (one at 1.3mm and one at 1.4mm)with
low-mass Class 0 protostellar system IRAS 16293-2422.They a spectral resolution of 2 MHz (∼ 2.6 km s−1 at 1.4 mm). The
detected13emissionlinesindicatingthepresenceofglycolalde- observed spectral ranges are the following: 217.0–220.5 GHz
hyde in the warm gas (200–300 K) in the inner regions of the (1.4mmhereafter),and229.0–233.0GHz(1.3mm).Calibration
system,within∼50aufromeachprotostar.Thisstudypavedthe wascarriedoutfollowingstandardprocedures,usingGILDAS-
waytothestudyofglycolaldehydearoundSun-likestarforming CLIC3. The phase rms was ≤ 65◦, the precipitablewater vapor
regions(see also therecentworkbyJørgensenetal. 2016).In- (PWV) was typically less than 2mm, the system temperatures
deed, Coutens et al. (2015) and Taquet et al. (2015) detected, lessthan200K.Thefinaluncertaintyontheabsolutefluxscale
usingtheIRAMPdBarray,upto8glycolaldehydelinestowards is ≤ 15%. The continuumemission was removedfromthe vis-
twootherswellknowhot-corinosassociatedwiththeNCC1333- ibilitytablestoproducecontinuum-freelinetables.Thetypical
IRAS2A and NGC1333-IRAS4A protostars, finding tempera- rmsnoiseinthe2-MHzchannelswas3–9mJybeam−1.Images
tureshigherthan100K. Goingbeyondthese initialfindings,it wereproducedusingnaturalweighting,andrestoredwithaclean
is important to perform a more systematic study to understand beamof≤1′′,reported,foreachsourceandforeachwavelength,
howcommonistheoccurrenceofglycolaldehydearoundsolar- inTable1.
typeprotostars,andwhetherthepresenceofrelativelyabundant
gas-phaseglycolaldehydecanbelinkedtoa specific evolution-
aryphase.Auniformsensitivityandhighangularresolutionsur- 3. Thesample
veyofprotostarsisthebestapproachtoattempttoanswerthese
Thesampleofsourcesisbasedonallthe peaksdetectedinthe
questions.
1.3mm and 1.4mm continuum images of CALYPSO targets in
TheCALYPSO1surveyofClass0protostars(i.e.104–105yr
Perseus (see Codella et al. 2014; Santangelo et al. 2015; An-
solaranalogprotostars;Andréetal.1993,2000),whichwascar-
derl et al. 2016; Maury et al., in preparation). We selected the
ried out with the IRAM-PdB interferometer (see Maury et al.
sourcesinthePerseuscomplex,whichisaclassicallaboratoryto
2014,formoredetails),offersauniquedatasetforstudyinggly-
studylow-massstarformation;inparticular,theselectedsources
colaldehyde.ThesourcesaremainlyClass0protostarswiththe
belong to the most active sites of current star formation in the
exceptionofSVS13-AwhichhasapparentlyenteredintheClass
Perseuscloud:theNGC-1333andL1448clusters.Weobserved
I stage (Lada 1987). CALYPSO includes all Solar-mass proto-
4multiplesystemsinNGC-1333(IRAS2A,IRAS4A,IRAS4B,
stellarsystemsinthePerseusL1448(d =232±18pc;Hirotaet
andSVS13)aswellas4protostarsinL1448(2A,NB,NA,and
al. 2011) and NGC-1333 (d = 235±18 pc; Hirota et al. 2008)
C objects), for a total number of 13 objects to be analysed to
regions.The dataset(see Sect. 2) includeshigh angularresolu-
search for glycolaldehyde emission. In Table 1 we report the
tion(≤1′′)spectralmapsat1.3and1.4mm,whichcoverabroad
continuumpeaks detected at 1.4 mm in Perseus using the CA-
rangeofglycolaldehydelinesandupper-levelenergyandaread-
LYPSOdatabase;foreverysourcearereportedthepositionsof
equateforaninitialstatisticalstudy.Inthispaperwepresentan
the peaks and the systemic velocities (V ) extracted from the
sys
analysis of these data, limited to the glycolaldehydemolecule,
CALYPSOdataset,the1.4mmpeakflux,theinternalluminos-
a detailed analysis of the continuum data will be presented in
ity(L ),andthecleanbeams(HBPW )foreachwavelength.
int syn
Maury et al. (in preparation), and the analysis of all complex
Theinternalluminositiesarederivedusingthe70µmmeasure-
organic molecules detected in the survey in Belloche et al. (in
mentsprovidedbytheHerschelGouldBeltsurvey(Andréetal.
preparation).
2010).Inparticular,Dunhametal.(2008),inthecontextofthe
The goal of the present paper is: (i) to perform a first sta- SpitzerSpaceTelescopeLegacyProject"FromMolecularCores
tistical analysis of the occurrence of glycolaldehyde emission toPlanetFormingDisks",showedhowthe70µmfluxandinter-
towards Class 0 protostellar sources, and (ii) to take advantage nalluminosityofaprotostararetightlycorrelated.Astheformer
ofthecombinationofhighsensitivityandhighspatialresolution isadirectlyobservablequantitybutthelatterisnot,thiscorrela-
provided by the CALYPSO database to detect a large number tiongivesapowerfulmethodforestimatingprotostellarinternal
oflinescoveringawiderangeofupper-levelenergy,leadingto luminosities. L isexpectedto be a morereliable probeofac-
int
reliableestimatesoftherotational(excitation)temperaturesand cretionluminositythanthebolometricluminosityL (seealso
bol
glycolaldehydecolumndensities.Theobservationsarereported Ladjelateetal.,inpreparation),whichrequiresafullcoverageof
inSect.2,whileinSect.3wedescribetheselectedsample.The theSpectralEnergyDistribution(SED)athigh-spatialresolution
obtained images, the derived physical conditions, and the esti- (8′′).
mate of the glycolaldehydeabundancesare reportedin Sect. 4. ThecontinuummapofNGC1333-IRAS2Arevealsthemain
OurconclusionsaresummarizedinSect.5. protostar IRAS2-A1, plus two weaker peaks, IRAS2-A2 and
IRAS2-A3 (see Codella et al. 2014).The nature of A2 and A3
is still debated, being possibly dust fragments associated with
the molecular cloud and swept up by the outflows driven by
2. Observations the nearbyIRAS2-A1protostar(see Codella et al. 2014;Tobin
et al. 2016). For the purpose of the analysis presented in this
ThePerseussources(listedinTable1)wereobservedat1.3mm paper, we have considered these as genuine protostars, except
and1.4mmwiththeIRAMPdBsix-elementarrayduringseveral where explicitly mentioned otherwise. The NGC-1333-IRAS4
tracks between November 2010 and February 2012 using both system has two main objects: IRAS4A and IRAS4B. In turn,
the A and C configurations.The shortest and longest baselines IRAS4AisabinarycomposedbytwoClass0objects,separated
are 19mand762m, respectively,allowingusto recoveremis-
sion at scales from ∼ 8′′ down to ∼ 0′.′4. The glycolaldehyde 2 Spectroscopic parameters havebeen extracted fromtheJet Propul-
sionLaboratorymolecular database(Pickettetal.1998),seeTables2
to5.
1 http://irfu.cea.fr/Projects/Calypso 3 http://www.iram.fr/IRAMFR/GILDAS
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Table1.Continuumpeakemissionat1.4mm,detectedinPerseususingtheCALYPSOsurvey,whereglycolaldehydeemissionhasbeensearched
for.
Source α(J2000)a δ(J2000)a V a db F L c HPBW
sys 1.4mm int syn
(hm s) (◦′′′) (kms−1) (pc) (mJy/beam) (L ) ′′×′′(◦)
⊙
1.4mm 1.3mm
L1448-2A 03:25:22.406 +304513.28 +4.2 232 31 2.7 0′.′99×0′.′71(28◦) 1′.′03×0′.′81(39◦)
L1448-NB 03:25:36.364 +304514.84 +4.7 232 25 4.1 0′.′81×0′.′67(67◦) 0′.′65×0′.′48(48◦)
L1448-NA 032536.503 +304521.87 +4.7 232 139 - 0′.′81×0′.′67(67◦) 0′.′65×0′.′48(48◦)
L1448-C 032538.878 +304405.32 +5.2 232 102 6.8 0′.′77×0′.′63(22◦) 0′.′61×0′.′38(33◦)
IRAS2A3 032855.514 +311434.84 +7.3 235 16 - 0′.′82×0′.′80(32◦) 0′.′75×0′.′74(168◦)
IRAS2A1 032855.575 +311437.05 +7.3 235 99 26.7 0′.′82×0′.′80(32◦) 0′.′75×0′.′74(168◦)
IRAS2A2 032855.677 +311435.56 +7.3 235 12 - 0′.′82×0′.′80(32◦) 0′.′75×0′.′74(168◦)
SVS13-B 032903.075 +311551.71 +8.4 235 122 1–2c 1′.′06×0′.′80(20◦) 0′.′70×0′.′42(20◦)
SVS13-A 032903.759 +311603.74 +8.4 235 123 24.5 1′.′06×0′.′80(20◦) 0′.′70×0′.′42(20◦)
IRAS4A2 032910.429 +311332.10 +7.2 235 284 - 1′.′10×0′.′81(20◦) 0′.′70×0′.′42(20◦)
IRAS4A1 032910.531 +311330.96 +7.2 235 795 2.8 1′.′10×0′.′81(20◦) 0′.′70×0′.′42(20◦)
IRAS4B1 032912.012 +311308.07 +6.7 235 449 1.0 1′.′08×0′.′83(20◦) 0′.′70×0′.′42(20◦)
IRAS4B2 032912.840 +311306.98 +6.7 235 53 - 1′.′08×0′.′83(20◦) 0′.′70×0′.′42(20◦)
aPositionsofthe1.3mmcontinuumpeakemissionandsystemicvelocitiesareextractedfromtheCALYPSOdataset(Codellaet
al.2014;Santangeloetal.2015;Anderletal.2016;Mauryetal.,inpreparation).bFromHirotaetal.(2008,2011).c Internal
luminositieswerederivedfromtheobservedfluxat70µm(Dunhametal.2008),awavelengthatwhichHerschelGouldBelt
surveyobservations(Andréetal.2010)providedataat8′′spatialresolution(seealsoLadjelateetal.,inpreparation).Theinternal
luminosityofSVS13-BismoreuncertainduetotheproximitytoSVS13-A.
by 1′.′8: IRAS4-A1 and IRAS4-A2 (e.g. Looney et al. 2000). Table2.NumberofglycolaldehydelinesandresultsoftheLTEanalysis
forthedetectedsources.
While IRAS4-A1 is more than three times brighterin the mm-
fluxthanitscompanion,onlyIRAS4-A2showsahighmolecular
Source N E T N
trans u rot tot
complexity(seeTaquetetal.2015;Coutensetal.2015;Santan- (K) (K) (1014cm−2)
geloetal.2015).IRAS4Bislocated∼30′′southeastofIRAS4A,
IRAS2A1 13 37–318 159(24) 46(20)
anditisassociatedwithtwocompactcontinuumsources,B1and
IRAS4A2 18 37–375 236(74) 88(70)
B2,withanangularseparationof11′′ (e.g.Looneyetal.2000;
IRAS4B1 13 37–271 152(35) 15(9)
Choi et al. 2011). NGC1333-SVS13 is a cluster dominated at
SVS13-A 11 37–375 115(13) 21(8)
millimeterwavelengthsbytwosources:SVS13-A,andSVS13-
aInseveralcases(3forIRAS2A1,1forIRAS4A2,IRAS4B1,
B.SVS13AisaprotostaralreadyintheClassIstageanddrives
andSVS13-A;seeTablesA1toA4),thedetectedlinesaredue
an extended outflow associated with the well-known HH7-11
totwoglycolaldehydetransitionsatfrequenciesblendedatthe
chain (e.g.Lefloch et al. 1998;Chen et al. 2009).On the other
presentspectralresolution.
hand,SVS13-BisanearlierprotostarlyingsouthwestofSVS13-
A ata distanceof15′′ (e.g.Bachilleretal. 1998;Looneyetal.
2000).Finally,theL1448-NA,L1448-NB,andL1448-2Aproto-
starsarelocatedinthenorthernportionoftheL1448complex,at
about∼1◦southwestofNGC1333,whileL1448-Cislocatedat
ofatleast3.Wethenselectedonlythosetransitionswithacor-
thecenteroftheL1148complex(seeLooneyetal.2000;Tobin
respondingsyntheticline(derivedusingtherotationdiagramso-
etal.2016,andreferencestherein).
lutions, see below) that reproduces at least 50% of a detected
peaktemperature.ThelineswereidentifiedusingtheJetPropul-
sionLaboratory(JPL)moleculardatabase(Marstokk&Møllen-
4. Resultsanddiscussion
dal1970,1973;Pickettetal. 1998;Butleret al. 2001;Widicus
Theresultsofthepresentsearchtowardsthecoordinateslistedin Weaveretal.2005;Carrolletal.2010).Figure1showsexamples
Table 1 indicatesthe presence ofglycolaldehydetowards4 out of glycolaldehydeemission lines (in TB scale) observed in the
ofthe13observedcontinuumpeaks.Ifweconsiderthattheclas- 1.3mmand1.4mmspectral windowstowardsthe fourdetected
sificationoftheIRAS2-A3andIRAS2-A2continuumpeaksas sources.FiguresA.1,A.3,A.5,andA.7showallthelinesused
genuineprotostarsisdebated(seetherecentpaperbyTobinetal. for the following analysis. Tables A.1-A.4 report the observed
2016),thedetectionrateis∼36%.Interestingly,glycolaldehyde line parameters; we list both peak line intensities (Tpeak) and
hasonlybeendetectedtowardstheNGC1333sources,wherethe velocities (Vpeak, consistent with the LSR velocities of the ob-
detectionrateisashighas∼60%. jects),linewidth(FWHM),andtheintegratedemission( Tdv).
Figures A.1 to A.9 report the spectra at the frequencies of All the values are in T scale and are derived from GRaussian
B
theglycolaldehydelinesobservedtowardsIRAS2A1,SVS13-A, fits.Awideupper-levelenergyrangeisobserved(seeTable2),
IRAS4A2,andIRAS4B1.Thespectralresolutiondoesnotallow withE from37Kupto375K:thisallowsus(i)toimproveon
u
us to probe the profiles of the emission lines and the observed the results of Coutenset al. (2015)and Taquet et al. (2015)on
spectraareaffectedbylineblending.Nevertheless,thereislittle IRAS2A1andIRAS4A2,byincreasingthenumberofdetected
doubtthatthelargeWideXbandwidths(8GHzintotal)allowed linesandexpandingtherangeofupper-levelenergyprobed,and
us to detecttowardsthe foursourcesa considerablenumberof (ii)tofirmlyassess,forthefirsttime,theglycolaldehydeoccur-
glycolaldehydelines(upto18)withasignal-to-noiseratio(S/N) rencetowardsIRAS4B1andSVS13-A.
Articlenumber,page3of24
A&Aproofs:manuscriptno.desimone
Fig. 1. Examples of glycolaldehyde emission lines (inT scale) observed inthe 1.3mm and 1.4mm spectral windows (and at different upper-
B
level energy, E from 37 K to 135 K) towards NGC1333-IRAS2A1 (Upper-left panel), NGC1333-IRAS4A2 (Upper-right panel), NGC1333-
u
IRAS4B1(Lower-leftpanel),andNGC1333-SVS13A(Lower-rightpanel).Thehorizontalgreendottedlinesshowthe3σlevel.Inbluewemark
theglycolaldehydelinesextractedfromTablesA1-A4.Thebrightlineat∼220190MHzisduetoCH OCHO(17 –16 )A(Mauryetal.2014;
3 4,13 4,12
Belloche et al.inpreparation). Thered lineshows thesynthetic spectrum obtained withtheGILDAS–Weedspackage (Maret et al.2011) and
assumingtherotationdiagramsolutions(seeFig.3).
4.1.HCOCHOHspatialdistributions natedby emission dueto the SO17O(13 –13 ) transition at
2 2,12 1,13
220196.75MHz(E =93K,log(A /s−1)=-3.8).Weinspected
u ij
Figure 2 compares the spatial distribution of the glycolalde- the CALYPSO datasetsearchingfor emission lines due to SO
2
hyde emission (colour scale and green contours) with that isotopologues.Wehaveonlyaweak(lessthan3σ)34SO (4 –
2 2,2
of the 1.4mm continuum (white contours; see Codella et al. 3 ) emission at 229.9 GHz (E = 19 K, log (A /s−1) = -4.1),
1,3 u ij
2014; Maury et al., in preparation) towards (from top to butonlyaroundtheNGC1333-IRAS4A2protostar.Inaddition,
bottom) NGC1333-IRAS2A1, NGC1333-IRAS4A, NGC1333- againonlyIRAS4A2,wehaveatentative(≥3sigma)detection
IRAS4B1,andNGC1333SVS13-A.Theglycolaldehydedistri- of the SO (11 –12 ) line (E = 122 K) at 229.3 GHz, and,
2 5,7 4,8 u
bution refers to emission lines in both the 1.3mm and 1.4mm not surprisingly, no detection of the SO (22 –23 ) line at
2 7,15 6,18
spectralwindows,i.e.thesumofthe76,2-65,1 and76,1-65,2 lines 219.3GHz(Eu=352K).Inanycase,thespectralresolutionand
(220.2GHz, Eu =37K),andthe222,21-211,20 line(232.3GHz, sensitivityofthepresentdatasetisnothighenoughtoproperly
Eu =135K).ConsistentwiththeresultsofTaquetetal.(2015), investigatethisintriguingpossibility,callingforfurtherinterfer-
our images indicate that the glycolaldehyde emission is only ometricobservations.The analysispresentedin thispaperonly
marginally resolved. For each source, we derived the emission referstothecompactcomponent.
size of the brightest line at 1.3 mm shown in Fig. 2 by fit-
ting an elliptical Gaussian in the uv domain: we obtain about
0′.′5 (IRAS2A1),0′.′4 (IRAS4A2, IRAS4B1), and0′.′3 (SVS13- 4.2.HCOCH2OHrotationdiagrams
A), whichimpliesthattheglycolaldehydeemission isconfined Giventhattheglycolaldehydecollisionalratesarenotavailable
in the inner 100 au around each protostar. The glycolaldehyde in the literature,we derivedexcitationtemperatureandcolumn
emission peak is consistent, considered the angular resolution, densities by using a crude approach such as the classical rota-
with the continuum peaks. Our results confirm the hot-corino tional diagram, assuming a unique temperature, optically thin
natureofNGC1333-IRAS2A1andNGC1333-IRAS4A2,previ- emission,andLocalThermodynamicEquilibrium(LTE)condi-
ouslynotedbyMauryetal.(2014)andTaquetetal.(2015),and tions.Weappliedacorrectionduetothebeamfillingfactorus-
inadditionsupportsthesamenatureforIRAS4B1andSVS13-A ingthesizesreportedinSect.4.1.Undertheseassumptions,for
(seeSect.4.2forthetemperaturemeasurements). agiventransitionthecolumndensityoftheupperlevel, N ,is
up
Finally,the image of the brightestglycolaldehydeemission relatedtotherotationaltemperatureTrot,asfollows:
(at 220.2 GHz) of the IRAS4-A1+A2 system, shows, in addi-
tion to the A2 compact core, a tentative detection at 5σ of a 8πkν2
more extended emission. If significant, either this could trace Nup = hc3A ff Z Tdv (1)
part of the extended envelope hosting the two protostars; or it ul
could be associated with the swept-upmaterialassociated with
N E
up up
thetwoN-SoutflowsdrivenbytheA1andA2protostars(San- ln =lnN −lnQ(T )− (2)
tot rot
g kT
tangeloetal.2015).Inthelattercase,thiswouldbethefirstsig- up rot
nature of glycolaldehyde emission from a protostellar outflow. where:handk arethePlanckandBoltzmannconstants,re-
However, note that this feature could be potentially contami- spectively, ff isthebeamfillingfactor(derivedusingthesizes
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DeSimoneetal.:GlycolaldehydeinPerseusyoungsolaranalogs
Fig.2.Comparisonbetweenthe1.4mmcontinuum(whitecontours)andtheglycolaldehydespatialdistributions(colourscaleandgreencontours)
towards(fromtoptobottom)NGC1333-IRAS2A1,NGC1333-IRAS4A,NGC1333-IRAS4B1,andNGC1333SVS13-A.Forcontinuum,firstcon-
toursandstepscorrespondto5σ(14mJybeam−1)and10σ,respectively.TheellipsesshowthePdBIsynthesisedbeam(HPBW)forthecontinuum
(white,seeTable1)andglycolaldehydeimages.TheHPBWsfortheglycolaldehydeimagesat1.4mmare:0′.′82×0′.′70,32◦(NGC1333-IRAS2A1),
1′.′08×0′.′81,19◦ (NGC1333-IRAS4A),1′.′08×0′.′83,20◦ (NGC1333-IRAS4B1),and1′.′06×0′.′80,20◦ (NGC1333SVS13-A).TheHPBWsforthe
glycolaldehydeimagesat1.3mmare:0′.′82×0′.′70,32◦(NGC1333-IRAS2A1),0′.′72×0′.′44,21◦(NGC1333-IRAS4A),0′.′72×0′.′44,21◦(NGC1333-
IRAS4B1),and0′.′71×0′.′43,21◦(NGC1333SVS13-A).Leftpanels:Theglycolaldehydedistributionreferstothesumofthe7 -6 and7 -6
6,2 5,1 6,1 5,2
emissionwith(220.2GHz, E =37K;seeTablesA1-A4).Firstcontours andstepscorrespond to5σ (90,90, 75,and55mJybeam−1 kms−1
u
respectively forNGC1333-IRAS2A1, NGC1333-IRAS4A,NGC1333-IRAS4B1, andNGC1333 SVS13-A)and3σ, respectively. Right panels:
Theglycolaldehydedistributionreferstothe22 -21 emission(232.3GHz,E =135K;seeTables2-5).Firstcontoursandstepscorrespond
2,21 1,20 u
to5σ(100,110,50,and60mJybeam−1kms−1respectivelyforNGC1333-IRAS2A1,NGC1333–IRAS4A,NGC1333-IRAS4B1,andNGC1333
SVS13-A)and3σ,respectively.
Articlenumber,page5of24
A&Aproofs:manuscriptno.desimone
27
IRAS2A1 1.4mm IRAS4A2 1.4mm
26.5 1.3mm 1.3mm
26
25.5
) )
a a
g g
/ /25
a24.5 a
N N
( (
n n
l l24
23.5
22.5 N=46(20) 1014cm−2 23 N=88(70) 1014cm−2
T=159(24) K T=236(74) K
50 100 150 200 250 300 50 100 150 200 250 300 350
E /K (K) E /K (K)
u b u b
27
26 IRAS4B1 1.4mm SVS13-A 1.4mm
1.3mm 1.3mm
26
)a25 )a25
g g
/ /
a a
N N
24
( (
n24 n
l l
23
N=15(9) 1014cm−2 N=21(8) 1014cm−2
23 T=152(35) K 22 T=115(13) K
50 100 150 200 250 300 50 100 150 200 250 300 350
E /K (K) E /K (K)
u b u b
Fig.3.RotationdiagramfortheglycolaldehydetransitionsreportedinTable2forNGC1333-IRAS2A(Upper-leftpanel),NGC1333-IRAS4A2
(Upper-rightpanel),NGC1333-IRAS4B1(Lower-leftpanel),andNGC133-SVS13A(Lower-rightpanel).Thelineintensitieshavebeencorrected
forbeamdilutionusingthesizesderivedinSect.4.1.TheparametersN ,g ,andE arerespectivelythecolumndensity,thedegeneracy,andthe
up up up
energyoftheupperlevel.Theerrorbarsonln(N /g )aregivenbytheverticalbarofthesymbols.Redandbluepointsrefertothelinesdetected
up up
inthe1.3mmand1.4mmspectralbands,respectively.Thedashedlinesrepresentthebestfits.
reportedin Sect. 4.1), g is the degeneracyof the upper level, ofthepresentlineidentification.Ontheotherhand,thederived
up
N isthetotalcolumndensity,Q(T )isthepartitionfunction, N are lower than what Jørgensenet al. (2012, 2016) towards
tot rot tot
andE istheupperlevelenergy.Figure3showstherotationdi- theIRAS16293-2422binary(3–4×1016 cm−2)found,inOphi-
up
agramsobtainedusingboththe1.3mm(redpoints)and1.4mm uchus,onsmaller(≤60au)spatialscales.Thesourceswherewe
(blue points) lines, while Table 2 reports the results, i.e. high reporta detection of glycolaldehydeare those with the highest
temperatures,T between115K and236K,and N ≃ 1–9× numberofspectrallinesofcomplexorganicmoleculesdetected
rot tot
1015cm−2.Thepresentdataimage,forthefirsttime,ahotcorino above 6 sigma in the 1.3 mm and 1.4 mm WIDEX spectra of
aroundSVS13-AandNGC1333-IRAS4B1.Thesefindingscon- theCALYPSOsubsampleofPerseussources(Bellocheetal.,in
firm thatthe glycolaldehydegasis presentin the regionwith a prep.).
radius less than 100 au where the temperature is high enough Therotationdiagramsolutionshavebeenusedtocreatesyn-
to sublimate the dust mantles. Thus, either glycolaldehyde is thetic spectra (see the red lines in Fig. 1 and Figs. A.1 to A.9)
directly released from mantle sublimation or formed through to strengthen the detection using the GILDAS–Weeds package
gas-phase reactions using simpler species directly formed on (Maret et al. 2011). We assumed a backgroundtemperature of
the mantles and successively evaporated due to thermal heat- 2.73 K. In principle, for sources with a strong continuumsuch
ing. Note that the sources where we report a detection of gly- as NGC1333-IRAS4B1,the columndensity obtainedusing the
colaldehydeare thosewith thehighestnumberofspectrallines rotational diagram method can be underestimated, converting
ofCOMs(e.g.HCOOCH3)detectedabove6σinthe1.3mmand the measurementin a lower limit. The synthetic intensities are
1.4mmWideX spectra of the CALYPSO subsampleof Perseus notsystematicallyover-orunder-estimatingtheobservedlines,
sources(Bellocheetal.,inpreparation).InthecaseofIRAS2A1 confirmingthat the temperaturesderivedfrom the rotationdia-
and IRAS4A2, the estimated rotational temperatures and col- gramsaregoodapproximations.Notethatallthedetectedlines
umndensitiesarewellinagreement(afterapplyingcorrectlythe areopticallythin.However,eventhoughtherotationaldiagrams
beam filling factor scaling) with what was previously reported showreasonableagreementbetweenmeasurementsandthesin-
byTaquetetal.(2015)andCoutensetal.(2015)usingdifferent gletemperaturemodel,itisworthtopointoutheresomeshort-
datasetsonsimilar spatialscales, thusconfirmingthegoodness comings of our models in reproducing the observed spectra.
Articlenumber,page6of24
DeSimoneetal.:GlycolaldehydeinPerseusyoungsolaranalogs
4.3.HCOCHOHoccurrencearoundprotostars
2
16.0 Figure 4 compares the column densities measured towards the
foursourcesdetectedinglycolaldehydewiththeupperlimitson
15.5
2) Ntot derived for the 9 objects in Perseus where glycolaldehyde
− hasnotbeenrevealed.Assumingatypicaltemperatureof150K,
m 15.0
c a size of 0′.′4 (see Sect. 4.1), and considering the 3σ values of
/
g14.5 the spectra where no glycolaldehydeemission has been found,
N thetypicalupperlimit is ≤ 1015 cm−2, i.e. oneorderofmagni-
(
0
114.0 tude less than what found in IRAS2A1, IRAS4A2, IRAS4B1,
g
lo 1133..05 IRAS2A1 IRAS4A2 IRAS4B1 SVS13-A IRAS2A2 IRAS2A3 IRAS4A1 SVS13-B L1448-2A L1448-C L1448-NA L1448-NB IRAS4B2 athdonyisrddetaecSrtmsVlysSoha1loed3wci-uffAalee.srsTeiginhnnceiestfiheicenmagngeatlalysyscuphorhilegaamlhsdeeee.rnhHctysoodlswueumepavbpneuordnr,tedtnthahsniaiscttyemt.hoaefysgenlyfooctourlreaflpldreoec--t
Source To estimate the possible enhancement (or deficit) of gas
phaseglycolaldehydeabundanceinthesourcesinoursamplewe
needtocomparewithanestimateofthetotalgascolumndensity
Fig.4.Distributionoftheglycolaldehydecolumndensity(Ntot)derived ineachsource.Asaproxyforthetotalcolumndensitytowards
towards the selected sample (see Table 1). Red arrows are for upper
eachsourceweusethepeakcontinuumfluxat1.4mm.Themil-
limits.
limetrecontinuumfluxinthesesourcesisdominatedbythether-
malemissionfromdustgrains.Theexactconversionofthemil-
limeterfluxintototalgascolumndensitydependsonthreevery
uncertainfactors: the dust properties(definingthe dust opacity
per gram of dust), the dust density and temperature structure,
and the gas to dust ratio. Comparing the observed glycolalde-
hydecolumndensitieswiththecontinuumpeakfluxwillallow
While we do not find large discrepancies, the spectral resolu-
tosearchforsystematicabundancevariationsinoursampleonly
tion of our observations is relatively low and the spectra very
under the assumption that the sources in our sample have uni-
rich of emission lines (especiallyof the foursourceswherewe
formproperties.Whilethisisexpected,sinceoursourcesarean
do detectglycolaldehydeline). Thisimplies thatin some cases
homogeneoussetofprotostarsin thesame starformingregion,
thelinesmaybecontaminedbyemissionfromothermolecules.
inthefuturethisanalysiswillhavetoberefinedusingmoreex-
FiguresA.1,A.3,A.5, andA.7showsthelinesselected forthe
tensiveobservationsandmoreaccurateestimatesofthetotalgas
analysis.Tobethorough,Figs.A.2,A.4,A.6,andA.8showall
columndensityineachsource.
the lines excluded from the present analysis because, although
theyareconsistentwiththeobservedspectrum,theblendswith Figure5showstheratiobetweentheglycolaldehydecolumn
otherspeciespreventsafirmidentificationoftheline.Notethat, density, Ntot, and the continuum peak flux at 1.4 mm (F1.4mm,
in a few cases, our simple LTE model predicts higher fluxes fromMauryetal.inpreparation)againstthevalueofthe1.4mm
thanobserved;a specialcase isrepresentedbythe 20 -19 peak flux itself. As mentioned above, if we assume that the
2,18 3,17
line at 220463 MHz observed towards NGC1333-IRAS4B1, - molecular hydrogen column density scales with the dust peak
IRAS2A1, IRAS4A2, and -SVS13A (see Fig. A.9), and con- flux density, then the plot in Fig. 5 shows that the gas phase
servatively excluded from the LTE analysis falling at the edge abundanceofglycolaldehyderelativetomolecularhydrogenhas
of the observed WideX band. Beside this line, only in 2 cases aspreadofa factorofabout10amongthe sourceswithglyco-
(overagrandtotalofabout90lines,countingalsothosenotused laldehydedetections.Evenif thenon-detectionof sourceswith
herebecauseofblending)thediscrepancyreachesafactor3:the F1.4mmlessthan100mJymightsuggestthatadetectionrequires
22 −21 lineat∼232286MHzinIRAS2A1(seeFig.A.2), brightcontinuumemission,abrightcontinuumsourceisnotnec-
1,21 2,20
andthe9 −8 lineat∼217626MHzinSVS13-A(seeFig. essarilyassociatedwithglycolaldehydeemission.A typicalex-
5,5 4,4
A.8).Thedifferenceisevenlessonceconsideredboththeerrors ample is given by the IRAS4-A1+A2 system, where it is only
associatedwiththeLTEfit(seeTable2)andtheerrorsontheob- theobjectshowingweakercontinuumemissionthatisdetected
servedlinepeakintensity.Indeed,forlinesclosetothedetection in glycolaldehyde(see Fig. 2). If we consider the sources with
limitthesystematicdiscrepancycouldbeunderstoodintermsof continuum peak flux above ∼100 mJy/beam, then the average
thenoisefluctuationsandtheuncertaintyofthecontinuumsub- ratios for sources with detected glycolaldehyde are a factor of
traction in a region of the spectrum very rich of lines. We also ∼10higherthanthesourceswithupperlimits.Thissuggeststhat
notethatdeviationsfromthesimplifyingassumptionsofsingle the detected sources may have a significantly higher gas phase
temperatureLTE,nonthermalexcitationandabsorptionmaybe abundance of glycolaldehyde compared with the non-detected
the cause of some of the discrepancies. Obtaining higher sen- sources.
sitivity and higher spectral and spatial resolution observations Theglycolaldehydedetectionindicatesthatthegasreached
over a broader frequency range, together with a full spectrum a temperature of at least 100 K; at these high temperaturesthe
modeling,willhelpderivingmoreaccurateestimatesofthegas gasis enrichedchemicallyby the release of moleculesdirectly
parameters. Nonetheless, eventually the intrinsic linewidth, the fromthe dustmantlesand/orbytheovercomeof theactivation
sourcechemicalcomplexityandrichnessofthespectraandthe barrierofgasphasereactionsusingwhatwasreleasedfromthe
sourcephysicalcomplexitywillalwayslimittheabilitytoaccu- icydustmantles.Itisreasonabletoassumethatthetemperature
ratelyidentifyandmeasureindividuallines.Overall,oursimple increaseswiththesourceluminosity,whichdependsonthepro-
LTEanalysisandcomparisonwiththespectrashowthat,while tostellarmassandonthesourceaccretionrate,whichinturnis
notperfect,itispossible toestimate a temperatureandcolumn related to the evolutionary stage. However, only three sources
densityrepresentativeofthebulkofthemolecularemission. whereglycolaldehydehasbeendetectedcanbeassociatedwith
Articlenumber,page7of24
A&Aproofs:manuscriptno.desimone
formingregionisparticularlyrichinglycolaldehyde,witha
14 definitelyhigherrateofoccurrence:upto60%.
y) A1 2. Theglycolaldehydeemissioniscompactandcoincidentwith
2N/F/cm/mJ−g1.4mm1132 IRAS2A2 IRAS2A3 L1448-NBL1448-2A IRAS4B2 IRAS2L1448-CVS13-BSVS13-AL1448-NA IRAS4A2 IRAS4B1 A1 tllpcb3hiaore7nleovtdewtKesecorheosiieyntnunandgtpdrie.in1actuWoea0lumt0aeem3rig7Kstdye5speipetoraKeiaanncckn,adtgielaosde2nsfti0doarze0afeaiclscnuaiKhdnrpog.igpfdceeWaet0rht(t-′ieu.e′len4cepgvtciesnetodhhonlnioeegfis1wronhr8muei1)nrtr0eggcn0amyeunt,.mhpadwTuaebthrieetaaexhtrtrhutobeeoErurnefuingdsgldl,fhiyrneTtcoteaehormsrsoe--t,t
( S S4 lierresultstowardsIRAS2A1andIRAS4A2,andrevealfor
g10 RA thefirsttimethepresenceofhotcorinosaroundNGC1333-
lo I IRAS4B1andSVS13-A.Thetotalcolumndensitiesofgly-
11 colaldehydeinthedetectedsourcesare≃1–9×1015cm−2.
1.0 1.5 2.0 2.5 3.0
3. We suggest that the four hot corinos imaged in glycolalde-
log (F /mJy)
10 1.4mm hydeinNGC1333areassociatedwithasignificantlyhigher
gas phase abundance of glycolaldehydewith respect to the
Fig.5.Ratiobetweentheglycolaldehydecolumndensity(N )andthe
tot restofthesample.TheSVS13-A+BandIRAS4-A1+A2sys-
peak flux of the1.4mm continuum emission (F ; Maury et al., in
1.4mm temssuggestthatthedetectionofglycolaldehydeemissionis
preparation) versus the 1.4mm peak flux. Red arrows are for sources
duetothesourceevolution:thechemicalrichnesshighlights
whereglycolaldehydehasnotbeendetected.
those protostarsevolvedenoughto warma brightregionof
∼100 au at temperatures larger than 100 K. However, the
presentsampledoesnotallowustoreachafirmconclusion
a measurement of the internal luminosity hampering a reliable whethertheglycolaldehydedetectionisalwaysaquestionof
checkforatrend(seeTable1).Inaddition,our1.4mmfluxesdo evolutionoraccretionluminosityand/orifitdependsonthe
not allow us to derive a direct measurement of the protostellar environmenthostingtheprotostars.
mass.Tryingtoshedlightonthisaspect,wenotethatinthecase
oftheSVS13-A+Bsystem,glycolaldehydeisonlydetectedto- Ourinitialresultscanbeconfirmedandextendedwithmore
wards the more evolved SVS13-A source, with L = 24.5 L , sensitiveobservationsofalargersampleofobjects.Inparticular,
int ⊙
whereastheyoungerobjectSVS13-B,with L =1–2L .does more accurate determinationsof the possible variationsof gly-
int ⊙
notshowevidenceofanenrichedchemistry.Therefore,atleast colaldehydeabundanceingasphasewillbeapowerfulprobeof
in this case, the lack of a detectedhot-corinoin SVS13-Bsug- thechemicalevolutionofprotostarsandmayconfirmthepresent
gests that the protostarhad notenoughtime to warm a portion results.
of gas large/brightenough to be detectable. Interestingly, San-
Acknowledgements. WeareverygratefultoalltheIRAMstaff,whosededication
tangelo et al. (2015), using the SiO and CO jet properties im- allowedustocarryouttheCALYPSOproject.Thisworkwaspartlysupported
agedinIRAS4-A1+A2system,proposedthatthechemicalrich- bythe PRIN INAF2012–JEDIandbythe Italian Ministero dell’Istruzione,
nessobservedtowardsIRAS4-A2(andnottowardsIRAS4-A1), UniversitàeRicercathroughthegrantProgettiPremiali2012–iALMA(CUP
C52I13000140001). AMissupportedbytheMagneticYSOs, grantagreement
is due to a later evolutionary stage, inferred from the jet prop-
n.679937. CC, LT,and AMhave been partially supported bythe Gothenburg
erties driven by the two objects. Nevertheless, it is clear that a
Centre for Advanced Studies in Science and Technology as part of the Go-
more systematic comparativestudy of sources in differentevo- CASprogramOriginsofHabitablePlanets.Theresearchleadingtotheseresults
lutionary phases is required to reach a firm conclusion: based hasreceivedfundingfromtheEuropeanCommunity’sSeventhFrameworkPro-
only on a few sources (e.g. SVS13-A+B),it is verydifficultto gramme(FP7/2007-2013/)undergrantagreementsNo229517(ESOCOFUND)
andNo291294(ERCORISTARS),andfromtheFrenchAgenceNationaledela
tellwhethertheprimaryfactorleadingtothedetectionofglyco-
Recherche(ANR),underreferenceANR-12-JS05-0005.
laldehydeemissionisevolution(e.g.lowvalueofL /L )or
submm int
accretionluminosity(high L ) orenvironment(e.g.NGC1333
int
vs.L1448).Thesefindingscallforfurtheranalysisofthechem-
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A&Aproofs:manuscriptno.desimone
AppendixA: ObservedHCOCH OHemissionlines
2
TablesA.1toA.4report,forthe4sourceswhereglycolaldehyde
emissionhasbeendetected(IRAS2A,SVS13-A,IRAS4A2,and
IRAS4B),theresultsoftheGaussianfitforallthedetectedlines.
In particular,we first list the spectralparameters(frequency,ν,
upperlevelenergy,E , andtheSµ2 product,alltakenfromthe
u
Jet Propulsion Laboratory database; Pickett et al. 1998), fol-
lowed by the line parameters (in T scale), namely: the inte-
MB
grated emission ( Tdv), both peak line velocities (V ) and
peak
intensities(T ),Rlinewidth(FWHM),andr.m.s.noise.Figures
peak
A.1,A.3,A.5,andA.7showthelinesdetectedandusedforthe
analysis, Figs. A.2, A.4, A.6, and A.8 show the lines excluded
fromtheanalysisgiventhesevereblendingwithotheremission
lines, while Fig. A.9 is for a line which has not been used be-
causeitislocatedattheedgeoftheWideXbandwidth.
Articlenumber,page10of24