Outflows, infall and evolution of a sample of embedded low-mass protostars. The William Herschel Line Legacy (WILL) survey

6.4 MB·

by  J. C. Mottram

Astronomy&Astrophysicsmanuscriptno.will˙overview (cid:13)c ESO2017
January20,2017
Outflows, infall and evolution of a sample of embedded low-mass
protostars
The William Herschel Line Legacy (WILL) survey(cid:63)
J.C.Mottram1,2,E.F.vanDishoeck1,3,L.E.Kristensen4,5,A.Karska3,6,I.SanJose´-Garc´ıa1,S.Khanna1,
G.J.Herczeg7,Ph.Andre´8,S.Bontemps9,10,S.Cabrit11,12,M.T.Carney1,M.N.Drozdovskaya1,M.M.Dunham4,
N.J.Evans13,D.Fedele2,14,J.D.Green13,15,D.Harsono1,16,D.Johnstone17,18,J.K.Jørgensen5,V.Ko¨nyves8,
B.Nisini19,M.V.Persson1,M.Tafalla20,R.Visser21,andU.A.Yıldız22
(Affiliationscanbefoundafterthereferences)
7
ReceivedXXXX;acceptedXXXX
1
0
2
ABSTRACT

n
a Context. Herschel observations of water and highly excited CO (J >9) have allowed the physical and chemical conditions in the more active
J partsofprotostellaroutflowstobequantifiedindetailforthefirsttime.However,todate,thestudiedsamplesofClass0/Iprotostarsinnearby

9 star-formingregionshavebeenselectedfrombright,well-knownsourcesandhavenotbeenlargeenoughforstatisticallysignificanttrendstobe
1 firmlyestablished.
Aims.Weaimtoexploretherelationshipsbetweentheoutflow,envelopeandphysicalpropertiesofaflux-limitedsampleofembeddedlow-mass
] Class0/Iprotostars.
R Methods.WepresentspectroscopicobservationsinH O,COandrelatedspecieswithHerschelHIFIandPACS,aswellasground-basedfollow-up
2
S withtheJCMTandAPEXinCO,HCO+andisotopologues,ofasampleof49nearby(d<500pc)candidateprotostarsselectedfromSpitzerand
. HerschelphotometricsurveysoftheGouldBelt.ThismorethandoublesthesampleofsourcesobservedbytheWISHandDIGITsurveys.These
h dataareusedtostudytheoutflowandenvelopepropertiesofthesesources.Wealsocompiletheircontinuumspectralenergydistributions(SEDs)
p fromthenear-IRtommwavelengthsinordertoconstraintheirphysicalproperties(e.g.L ,T andM ).
bol bol env
- Results.Wateremissionisdominatedbyshocksassociatedwiththeoutflow,ratherthanthecooler,slowerentrainedoutflowinggasprobedby
o
ground-basedCOobservations.TheseshocksbecomelessenergeticassourcesevolvefromClass0toClassI.Outflowforce,measuredfromlow-J
r
t CO,alsodecreaseswithsourceevolutionarystage,whilethefractionofmassintheoutflowrelativetothetotalenvelope(i.e.M /M )remains
s broadlyconstantbetweenClass0andI.Themedianvalueof∼1%isconsistentwithacoretostarformationefficiencyontheoourtdereonfv50%and
a
[ anoutflowdutycycleontheorderof5%.Entrainmentefficiency,asprobedbyFCO/M˙acc,isalsoinvariantwithsourcepropertiesandevolutionary
stage.Themedianvalueimpliesavelocityatthewindlaunchingradiusof6.3kms−1,whichinturnsuggestsanentrainmentefficiencyofbetween

2 30and60%ifthewindislaunchedat∼1AU,orcloseto100%iflaunchedfurtherout.L[Oi]isstronglycorrelatedwithL butnotwith M ,
bol env
v incontrasttolow-JCO,whichismorecloselycorrelatedwiththelatterthantheformer.Thissuggeststhat[Oi]tracesthepresent-dayaccretion
7 activityofthesourcewhileCOtracestime-averagedaccretionoverthedynamicaltimescaleoftheoutflow.H Oismorestronglycorrelatedwith
2
4 M thanL ,butthedifferenceissmallerthanlow-JCO,consistentwithwateremissionprimarilytracingactivelyshockedmaterialbetweenthe
env bol
6 wind,tracedby[Oi],andtheentrainedmolecularoutflow,tracedbylow-JCO.L[Oi]doesnotvaryfromClass0toClassI,unlikeCOandH O.
2
4 Thisislikelyduetotheratioofatomictomoleculargasinthewindincreasingasthesourceevolves,balancingoutthedecreaseinmassaccretion
0 rate.InfallsignaturesaredetectedinHCO+andH Oinafewsources,butstillremainsurprisinglyillusiveinsingle-dishobservations.
2
.
1 Keywords.Stars:formation,Stars:protostars,ISM:jetsandoutflows,Surveys
0
7
1
1. Introduction comeofthestar-formationprocessforindividualsources,stellar
:
v clustersandevenwholegalaxies.
i Thegeneral,cartoonpictureofhowstarsformhasbeenagreed
X The first step is improved quantification of the basic phys-
for some time: a dense core within a molecular cloud becomes ical properties (e.g. L , M ) and evolutionary state of low-
r gravitationallyunstable,causingmaterialtofallinwardstowards bol env
a massprotostars,onwhichconsiderableprogresshasbeenmade.
the centre; a protostar forms and launches a bi-polar molecular
Improvements in detectors and telescopes have lead to full-
outflow;overtimetheoutflowandinfallcombinetoremovethe
wavelength coverage from optical to radio wavelengths at bet-
envelope, eventually starving the protostar, which then slowly
ter sensitivity and resolution, while dedicated very long base-
settles to the main sequence (e.g. Shu et al. 1987). However, a
lineinterferometry(VLBI)campaignsintheradioareproviding
moredetailedunderstandingisstillrequired,particularlyonin-
much more accurate distances for nearby star-forming regions
fall and outflow, in order to quantitatively track the conversion
(e.g.Loinard2013,forarecentreview).
ofmatterintostarsandaccuratelypredicttheevolutionandout-
A framework for defining the evolutionary status of proto-
starshasalsobeendeveloped,dividingprotostellarsourcesinto
(cid:63) Herschel is an ESA space observatory with science instruments oneoffivecategories(Class0,ClassI,Flat,ClassIIandClass
providedbyEuropean-ledPrincipalInvestigatorconsortiaandwithim- III) using various ways of quantifying the shift in the spectral
portantparticipationfromNASA. energy distribution (SED) to shorter wavelengths as the source
1
J.C.Mottrametal.:Outflows,infallandevolutionofasampleofembeddedlow-massprotostars
evolves: the infrared spectral index (α , e.g. Lada & Wilking ditions (T,N,n) remain the same (Mottram et al. 2014; Manoj
IR
1984; Lada 1987; Greene et al. 1994); the submillimetre (λ > etal.2013;Karskaetal.2013;Greenetal.2013a;Karskaetal.
350µm) to bolometric luminosity ratio (L /L used as a 2014a;Matuszaketal.2015).However,thesestudieshavetyp-
submm bol
proxyforM /L ,e.g.Andre´etal.1993);andbolometrictem- ically considered relatively small samples (N (cid:46)30) of bright,
env bol
perature(T ,e.g.Myers&Ladd1993;Chenetal.1995).For well-known sources and so the statistical significance of trends
bol
this latter measure, which is the intensity-weighted peak of the with evolution and other source parameters has, in some cases,
SED,theseclassificationsaredefinedas:Class0(T < 70K), beenlow.
bol
Class I (70≤ T <650K), Class II (650≤ T <2800K) and Two of the main surveys studying nearby Class 0/I proto-
bol bol
Class III (T ≥2800K). Flat-SED sources have T values in starswithHerschelwerethe“Waterinstar-formingregionswith
bol bol
the 350−950K range with a mean around 650K (Evans et al. Herschel”(WISH)guaranteedtimekeyprogram(vanDishoeck
2009). et al. 2011), which observed 29 Class 0/I protostars with HIFI
The Spitzer Space Telescope (Gallagher et al. 2003) and and PACS plus ground-based follow-up, and the “Dust, Ice,
more recently the Herschel Space Observatory (Pilbratt et al. and Gas in Time” (DIGIT) Herschel key program (Green et al.
2010)haveallowedthefullpotentialofthisevolutionaryframe- 2013a,2016),whichobservedafurther13Class0/Iprotostars,
worktobeexploitedinconstraininghowthepropertiesofpro- primarily with full-scan PACS spectroscopy. Both the WISH
tostars change as the source evolves through large-area, high andDIGITsurveysselectedtheirsamplestotargetwellknown,
spatialresolution,uniformphotometricsurveysofmanynearby archetypalsources,ensuringsuccessindetectingwater,COand
star-forming regions (e.g. Evans et al. 2003, 2009; Andre´ et al. other species and the availability of complementary data. As a
2010; Rebull et al. 2010; Megeath et al. 2012; Dunham et al. result, these samples favoured luminous sources with particu-
2014; Furlan et al. 2016). Furthermore, the statistics available larly prominent and extended outflows, which may not be rep-
from such large surveys have enabled estimates of the relative resentative of the general population of protostars. In addition,
lifetimesofthedifferentClassestobeobtained,showinginpar- both programs together only included a total of 42 low-mass
ticularthatthecombinedClass0andIphases,wherethemajor- sources split between Classes 0 and I, limiting the statistical
ityoftheprotostellarmassisaccretedandthefinalpropertiesof significance of trends with evolution that might otherwise have
the star and its accompanying disk are imprinted, last approxi- beenexpected,forexamplebetweenintegratedintensityinwater
mately 0.4−0.7Myr (Dunham et al. 2015; Heiderman & Evans emissionandT .
bol
2015;Carneyetal.2016). The motivation of the “William Herschel Line Legacy”
For a 1M star, such lifetimes imply typical time-averaged (WILL)surveywasthereforetofurtherexplorethephysics(pri-
(cid:12)
mass-accretion rates onto the protostar of approximately marilyinfallandoutflow)andchemistryofwater,COandother
10−6M yr−1. Since not all material in the core will end up on complementary species in Class 0/I protostars in nearby low-
(cid:12)
thestar,theinfallrateintheenvelopemustpresumablybehigher massstarformingregionsusingacombinationofHerscheland
thanthisbyatleastafactorof2or3.Searchestoquantifythein- ground-basedobservations,buildingonWISHandDIGIT.The
fallinprotostarshavepresentedcandidatesusingmolecularline aimwastoincreasethenumberofClass0/Iprotostarsobserved,
observations(e.g.Gregersenetal.1997;Mardonesetal.1997) thusimprovingthestatisticalsignificanceoftheexistingcorre-
based on the doppler-shift of infalling material causing asym- lationsfoundbyforexampleKristensenetal.(2012),andallow-
metries in the line profile (Myers et al. 2000). However, con- ingshallowercorrelationstobetested,aswellasimprovingthe
firmingandquantifyinginfallinprotostellarenvelopesremains samplingoffainterandcoldersources.
extremelychallenging,limitingourunderstandingoftherateat This paper is structured as follows. Section 2 discusses
which,androutebywhich,materialreachesthediskandproto- the selection of the WILL sample, the basic physical proper-
star, as well as how this changes with time and depends on the ties of the sources and evaluates the properties of the com-
massofthecore/star. bined WISH+DIGIT+WILL sample. Section 3 gives the de-
Bipolarmolecularoutflowsalsoplayanimportantroleinthe tails and basic results of both the Herschel observations and
evolution and outcome of star formation, as they remove mass a complementary ground-based follow-up campaign. More de-
fromandinjectenergyintotheenvelopeandsurroundingmate- tailed results and analysis are then presented thematically, cen-
rial. However, the driving mechanism for protostellar outflows tred around outflows (Sect. 4) and envelope emission (Sect. 5),
isstilluncertain(e.g.Arceetal.2007;Franketal.2014).Ade- followedbyadiscussiononthevariationofwaterwithevolution
creaseinthedrivingforcewasmeasuredbetweenClass0andI (Sect.6).Finally,wesummariseourmainconclusionsinSect.7.
sources,inadditiontorelationswithL andM ,byBontemps
bol env
et al. (1996) using ground-based observations of CO. They at-
tributedthedecreaseinoutflowdrivingforcewithClasstoade- 2. Sample
creaseintheaccretion/infallrateasthesourceevolves.However,
2.1. Selection
theirstudyonlyincludedtenClass0sources,asfewwereknown
atthetime. The starting point for selecting a flux-limited sample of low-
RecentobservationsofH Oandhighly-excitedCOusingthe mass protostars was the catalogue of Class 0/I protostars iden-
2
Heterodyne Instrument for the Far-Infrared (HIFI; de Graauw tified as part of photometric surveys with the Spitzer Space
etal.2010)andPhotodetectorArrayCameraandSpectrometer Telescopeoftheclosestmajorstar-formingcloudsthatmakeup
(PACS; Poglitsch et al. 2010) with Herschel have shown that the Gould Belt (Gould 1879). In particular, these were drawn
theseprimarilytraceactiveshocksrelatedtotheoutflowand/or from the Spitzer c2d (Evans et al. 2009), Spitzer Gould Belt
warmdiskwindsheatedbyambipolardiffusion,ratherthanthe (Dunham et al. 2015) and Taurus Spitzer (Rebull et al. 2010)
entrained outflow as is accessible with ground-based CO ob- surveys.
servations (Nisini et al. 2010; Kristensen et al. 2013; Tafalla The initial catalogue was compiled from individual cloud
et al. 2013; Santangelo et al. 2013, 2014; Mottram et al. 2014; catalogues for the Perseus, Taurus, Ophiuchus, Scorpius (also
Yvart et al. 2016). The line-width and intensity in these trac- known as Ophiuchus North), Corona Australis and Chameleon
ers decreases between Class 0 and I while the excitation con- star-formingregions(formoredetails,seeJørgensenetal.2007;
2
J.C.Mottrametal.:Outflows,infallandevolutionofasampleofembeddedlow-massprotostars
Rebull et al. 2007, 2010; Padgett et al. 2008; Jørgensen et al. 2.2. Propertiesandevaluation
2008; Hatchell et al. 2012; Peterson et al. 2011; Alcala´ et al.
The properties of the final sample of 49 sources that make up
2008).Atthetimeofselectionin2011,theHerschelGouldBelt
the WILL sample are presented in Table 1. For simplicity, we
(Andre´ etal.2010)surveyhadalsoproducedcataloguesofpro-
giveeachanamebasedontheregionandanumberorderedby
tostellarcandidatesintheAquilaRiftregion(Mauryetal.2011),
rightascension,butmanyarealreadywellknownandtherefore
sothesewerealsoconsideredinanattempttoextendthecover-
thetablealsogivesdetailsofcommonnamesusedbyprevious
ageoftheWILLsurveytoparticularlyyoung(cold)embedded
studiesforthesamesources.
youngstellarobjects(YSOs).
From this master catalogue of protostars in major star- Thefollowingdistancesareusedforthevariousregionscov-
formingregionswithin500pc,thefollowingcriteriawereused ered by our sample: 235pc for Perseus (Hirota et al. 2008),
toselectthefinalWILLsample: 140pc for Taurus (Kenyon et al. 2008), 125pc for Ophiuchus
andScorpius(deGeusetal.1989),130pcforCoronaAustralis
(i) infraredslope(2−24µm)αIR >0.3ornon-detection, (Knude & Høg 1998), 150pc for Chameleon I and 178pc
(ii) Tbol <350K, for Chameleon II (Whittet et al. 1997). For Aquila, W40 and
(iii) Lbol>0.4L(cid:12)forClass0(Tbol <70K), SerpensSouth,Ortiz-Leo´netal.(2016)recentlyfoundthatthese
Lbol ≥1L(cid:12)forClassI(70≤Tbol <350K), regions, as well as Serpens Main, are at a common distance of
(iv) δ<35◦. 436pc.
Thedeterminationofthesourcepropertiesandevolutionary
ThedistinctionbetweenClassIandIIsourcesisnormallymade
at T =650K (Chen et al. 1995), however Evans et al. (2009) classificationisdiscussedindetailinAppendixA.Tosummarise
bol
briefly,theSEDforeachsourceisconstructedfromthenear-IR
foundthatFlatSEDsourcescovertherange350−950Kwitha
to(sub-)mmandusedtocalculateL ,L /L ,T andα .
meanaround650Kandthereforelikelyconsistofmoreevolved bol submm bol bol IR
M isobtainedfromsub-mmormmphotometryassumingthat
Class I or younger Class II sources. An upper limit of 350K env
thedustisopticallythin,while(cid:51) iscalculatedfrommolecu-
wasthereforeimposedinordertoexcludemoreevolvedClassI LSR
larlineobservations.Finally,theclassificationofeachsourceis
sourcesfromthesample.Wateremissionistypicallyweakerfor
reachedbyconsideringthespatialandspectralpropertiesofboth
ClassIsourcesthanClass0sandisgenerallyhigherformorelu-
thegasanddustassociatedwitheachsource(seeAppendixA.7
minoussources(e.g.Kristensenetal.2012),soahigherL cut
bol
formoredetails).
wasusedforClassIsourcesinanattempttoensuredetections.
Criteria i−iii were therefore designed to ensure that the sample Thesamplecomprises23Class0,14ClassI,8ClassIIand4
uncertain,potentiallypre-stellarsources.Inthecaseofthislast
includesonlyyoung,deeplyembeddedprotostarsthatarebright
group of sources, all in W40, they are faint or not detected at
enough to be detected in H O and related species based on the
2
<160µm,showfewdetectionsinPACSandhavenoindications
experienceoftheWISHandDIGITsurveys.Criterionivensures
of outflow activity, but the presence of the W40 PDR, detected
that all WILL sources can be observed with ALMA to allow
insomeoftheHIFIandground-basedlines,leavessomeambi-
high spectral and spatial resolution ground-based interferomet-
guity.Theseandothercasesofnotearediscussedinmoredetail
ricfollow-upofinterestingsources.
inAppendixC.
Unfortunately,edge-ondisks,reddenedbackgroundsources
and evolved asymptotic giant-branch (AGB) stars all have the Figure 1 shows the Lbol, Tbol and Menv distribution of the
potentialtopresentsimilarinfraredcoloursandthuscontaminate WILL sample, along with the WISH and DIGIT samples for
any sample selected purely based on continuum properties. As comparison.ThepropertiesoftheWISHsamplearetakenfrom
first highlighted by van Kempen et al. (2009) for a sample of Kristensen et al. (2012) while those for the DIGIT sample are
sourcesinOphiuchus,molecularemissiontracingdensegascan takenfromGreenetal.(2013a)andLindbergetal.(2014).These
helptobreakthisdegeneracy.Morespecifically,thehighcritical are corrected to the distances for the various regions discussed
density of HCO+ J=4−3 or J=3−2 means it will not be strong abovewhereneeded.Itshouldbenotedthat Menv valuesarenot
inforegroundcloudmaterial,whiletherarityofC18Osimilarly availablefortheDIGITsample,leadingtothedifferenceinthe
meansthatthe J=3−2transitionisonlybrightandconcentrated number of sources between the upper-left and upper-right pan-
in protostellar sources. In addition, more evolved disk sources els.
will not present strong emission in single-dish HCO+ spectra The probability (p) that a given value of the Pearson corre-
due to beam-dilution. Such data, particularly for HCO+, have lationcoefficient(ρ)forsamplesizenrepresentsarealcorrela-
beencollectedandusedtoremovecontaminantsinanumberof tion(i.e.thelikelihoodthatatwo-tailedtestcanrejectthenull-
Gould Belt samples by Heiderman et al. (2010), Heiderman & hypothesisthatthetwovariablesareuncorrelatedwithρ=0)can
Evans(2015)andCarneyetal.(2016),whichhavesomeoverlap beexpressedintermsofthestandarddeviationofanormaldis-
with the initial candidate sample. Therefore, following the cuts tribution,σ,as:
detailedabove,non-detectioninHCO+ J=4−3or3−2wasused,
√
wheredatawereavailable,toexcludecontaminantsources. p=|ρ| n−1σ, (1)
MostofthesourcesobservedbytheWISHandDIGITsur-
veysalsoconformtotheabovecriteria,soanyinitialcandidates following (Marseille et al. 2010). We consider p =3σ (i.e.
within 5(cid:48)(cid:48) of a WISH or DIGIT source were also excluded to 99.7%)tobethethresholdforstatisticalsignificance.Thus,fora
avoid repeat observations. However, two sources, PER03 and samplesizeof30,valuesof|ρ|>0.56indicatereal,statistically
PER11, have enough overlap with the WISH observations of significantcorrelationswhileforasamplesizeof50,thisistrue
L1448-MM (offset by 7.7(cid:48)(cid:48)) and NGC1333-IRAS4B (offset by for | ρ |> 0.43. While one might expect correlations between
6.4(cid:48)(cid:48)), respectively, particularly in the H O 1 −1 (557GHz) someoftheobservedpropertiesofembeddedprotostarsdueto
2 10 01
ground-statelineobtainedina39(cid:48)(cid:48) beam,thattheyareremoved the related nature of their different components (e.g. envelope,
fromtheWILLsampleaspresentedhere.Finally,sourceTAU05 outflowanddrivingsource),suchtestsareasimplewayofascer-
wasremovedasitistheyoungandactiveClassIIsourceDGTau tainingwhetherornotthedataareabletosupportsuchlinks.As
B,whichhasanedge-ondisk(Podioetal.2013). mentionedabove,theextensionofthesampleofsourcesstudied
3
J.C.Mottrametal.:Outflows,infallandevolutionofasampleofembeddedlow-massprotostars
n=78 n=63
102
ρ=0.02 ρ=0.54
p=0.2σ p=4.2σ
8M
) 101 ⊙
⊙
L
(
ol
b
L 2M
100 ⊙
WILL Class0
WISH ClassI
0.6M
DIGIT ⊙ ClassII
10 1 SGB 0.08M 0.2M PS?
− ⊙ ⊙
102 101 10 1 100 101 102
−
T (K) M (M )
bol env
⊙
25
ALL
WILL
20
WISH&DIGIT
s
e SGB
c
ur15
o
s
of10
.
o
N
5
0
10 1 100 101 102 0 100 200 300 400 0 1 2 3 4 5
−
L (L ) T (K) M (M )
bol bol env
⊙ ⊙
Fig.1.Top:ThedistributionofL vs.T andM fortheWILL(filledcircles),WISH(opensquares)andDIGIT(opendiamonds)
bol bol env
surveys.Intheleft-handpanel,theSpitzerGouldBelt(SGB)determinationsfromDunhametal.(2015)areshownforcomparison
(blackdots).Thedifferentcoloursareusedtodistinguishbetweendifferentsourceclassifications:Class0(red),ClassI(blue)Class
II(green)andpre-stellar(PS,magenta).Thenumberofsources(n),Pearsoncorrelationcoefficient(ρ),andtheprobability(p)that
thecorrelationisnotjustduetorandomdistributionsinthevariablesareshownintheupper-leftofeachpanelincludingonlyClass
0/Isources.EvolutionarytracksbetweenL andM fromDuarte-Cabraletal.(2013)areshownintheright-handpanel(seetext
bol env
fordetails),withthefinalstellarmassindicatedforeachtrack.Bottom:histogramsshowingthedistributionofL ,T and M
bol bol env
fortheWILL(blue),combinedWISHandDIGIT(magentahatched),andtotalWILL,WISHandDIGIT(black)samples.Thegrey
shadedregionindicatesthedistributionoftheSpitzerGouldBeltdeterminationsforsourceswithT ≤350K.
bol
inspectrallineswithPACSandHIFIenabledbytheWILLsur- sourcesabove∼1L .Belowthisluminosity,thesamplerapidly
(cid:12)
veyandpresentedhereallowsustostudythesemorecompletely becomes incomplete, and thus the combined sample is still bi-
forthefirsttime. ased towards higher mean L compared with the general dis-
bol
TheevolutionarytracksbetweenL andM showninthe tribution, but the addition of the WILL sources shifts the com-
bol env
top-right panel of Figure 1 are taken from Duarte-Cabral et al. pleteness limit approximately a factor of three lower. In terms
(2013).TheyassumeanexponentialdecreaseofM andacore- of T , the sample is biased towards lower values, but judging
env bol
to-star formation efficiency of 50%, such that the net accretion from upper-left panel of Fig. 1, the higher T sources in the
bol
rateisgivenby: SGB data are primarily those below our L limit, that is, the
bol
meanL decreasesasT increasesforSGBsources.Thedif-
bol bol
M (t)
M˙ (t) = 0.5 env , (2) ferencesbetweenthevaluesofDunhametal.(2015)andthose
acc τ givenhereforindividualsourcesarelikelyduetoourinclusion
whereτisthee-foldingtime,whichisassumedtobe3×105yrs. offar-IRdatainthesedeterminations.
The WILL sample doubles the number of low-mass YSOs Itisworthmentioningacoupleofcaveats.Firstly,thesam-
observed,whichhaveslightlylowervaluesof L and M ,as ple of Class 0 sources is dominated by sources in the Perseus
bol env
wellaslowerT forClass0sources,thantheWISHandDIGIT molecular cloud, while the Class I sources are drawn from a
bol
samples. Comparing to Spitzer Gould Belt (SGB) sources with number of regions that vary in the concentration and activity
T ≤350K,takenfromDunhametal.(2015),itcanbeseenin of their star formation (e.g. Taurus vs. Ophiuchus). There may
bol
Fig.1thatthecombinedWILL+DIGIT+WISHsampleisrepre- wellberegionaldifferencesduetoenvironmentaleffects,which
sentative of the overall Class 0/I population and contains most we cannot test due to the overall small sample size for a given
4
J.C.Mottrametal.:Outflows,infallandevolutionofasampleofembeddedlow-massprotostars
Table1.TheWILLsurveysourcesample.
Name RA(J2000) Dec(J2000) d (cid:51) a L b Lsubmmb T b α b M b Classc Othernamesd
(hms) (◦(cid:48)(cid:48)(cid:48)) (pc) (kmLSRs−1) (Lbol) L(b%ol) (bKol) IR (Menv)
(cid:12) (cid:12)
AQU01e 18:29:03.82 −01:39:01.5 436 +7.4 2.6 11.8 24 − 3.15 0 Aqu-MM2
AQU02e 18:29:08.60 −01:30:42.8 436 +7.5 9.0 7.8 33 − 2.17 0 Aqu-MM4,IRAS18265-0132
AQU03e 18:30:25.10 −01:54:13.4 436 +7.1 3.5 5.3 246 0.7 0.79 II Aqu-MM6,IRAS18278-0156
AQU04e 18:30:28.63 −01:56:47.7 436 +7.6 6.5 4.5 320 0.5 1.21 I Aqu-MM7,IRAS18278-0158
AQU05 18:30:29.03 −01:56:05.4 436 +7.3 2.4 9.2 37 1.4 0.68 0 Aqu-MM10
AQU06 18:30:49.94 −01:56:06.1 436 +8.3 1.3 8.2 40 1.9 0.59 0 Aqu-MM14
CHA01 11:09:28.51 −76:33:28.4 150 +4.9 1.6 − 189 1.6 − II GMCha,ISO-ChaI192,CaINa2
CHA02 12:59:06.58 −77:07:39.9 178 +3.0 1.8 0.6 236 1.3 − I ISO-ChaII28,IRAS12553-7651
CRA01 19:02:58.67 −37:07:35.9 130 +5.6 2.4 2.2 55 1.7 0.49 0 ISO-CrA182,IRAS18595-3712
OPH01 16:26:59.10 −24:35:03.3 125 +3.8 4.3 − 69 2.0 0.17 II+PDR? ISO-Oph90,WL22
OPH02 16:32:00.99 −24:56:42.6 125 +4.2 8.6 0.1 80 1.8 0.09 I ISO-Oph209,Oph-emb10
PER01 03:25:22.32 +30:45:13.9 235 +4.1 4.5 2.7 44 2.3 0.89 0 L1448IRS2,Per-emb22
PER02 03:25:36.49 +30:45:22.2 235 +4.5 9.2 1.7 54 2.6 3.48 0 L1448N(A),L1448IRS3,Per-emb33
PER04 03:26:37.47 +30:15:28.1 235 +5.2 1.2 4.2 60 1.2 0.29 0 IRAS03235+3004,Per-emb25
PER05 03:28:37.09 +31:13:30.8 235 +7.3 11.1 0.6 84 2.2 0.36 I NGC1333IRAS1,Per-emb35
PER06 03:28:57.36 +31:14:15.9 235 +7.3 7.1 − 82 1.5 0.34 I NGC1333IRAS2B,Per-emb36
PER07 03:29:00.55 +31:12:00.8 235 +7.4 0.7 3.9 37 2.1 0.32 0 Per-emb3
PER08 03:29:01.56 +31:20:20.6 235 +7.7 16.9 1.3 129 2.5 0.83 I Per-emb54,NGC1333IRAS6
PER09 03:29:07.78 +31:21:57.3 235 +7.5 22.7 − 129 2.6 0.26 I IRAS03260+3111(W),Per-emb50
PER10 03:29:10.68 +31:18:20.6 235 +8.7 6.0 2.2 47 1.9 1.10 0 NGC1333IRAS7,Per-emb21
PER12 03:29:13.54 +31:13:58.2 235 +7.8 1.1 8.7 31 2.4 1.20 0 NGC1333IRAS4C,Per-emb14
PER13 03:29:51.82 +31:39:06.0 235 +8.0 0.7 5.0 40 3.5 0.49 0 IRAS03267+3128,Per-emb9
PER14 03:30:15.14 +30:23:49.4 235 +6.2 1.8 1.6 88 1.8 0.15 I IRAS03271+3013,Per-emb34
PER15 03:31:20.98 +30:45:30.1 235 +6.9 1.6 5.8 36 1.2 1.16 0 IRAS03282+3035,Per-emb5
PER16 03:32:17.96 +30:49:47.5 235 +7.0 1.1 13.3 29 1.0 2.88 0 IRAS03292+3039,Per-emb2
PER17 03:33:14.38 +31:07:10.9 235 +6.6 0.2 − 71 2.4 1.94 I B1SMM3,Per-emb6
PER18 03:33:16.44 +31:06:52.5 235 +6.6 0.5 − 38 1.6 1.59 0 B1d,Per-emb10
PER19 03:33:27.29 +31:07:10.2 235 +6.8 1.1 1.7 93 1.9 0.29 I B1SMM11,Per-emb30
PER20 03:43:56.52 +32:00:52.8 235 +8.9 2.2 6.3 27 0.7 1.93 0 IRAS03407+3152,HH211,Per-emb1
PER21 03:43:56.84 +32:03:04.7 235 +8.8 1.9 3.8 35 1.5 1.54 0 IC348MMS,Per-emb11
PER22 03:44:43.96 +32:01:36.2 235 +9.8 2.4 3.4 45 0.9 0.70 0 IRAS03415+3152,Per-emb8
SCO01 16:46:58.27 −09:35:19.8 125 +3.6f 0.5 0.6 201 0.9 0.10 II IRAS16442-0930,L260SMM1
SERS01 18:29:37.70 −01:50:57.8 436 +8.2 17.4 3.9 46 1.3 1.10 0 IRAS18270-0153,SerpS-MM1
SERS02 18:30:04.13 −02:03:02.1 436 +7.8 73.2 4.6 34 2.5 8.44 0 SerpS-MM18
TAU01 04:19:58.40 +27:09:57.0 140 +6.8 1.5 3.3 136 1.4 0.27 I IRAS04169+2702
TAU02 04:21:11.40 +27:01:09.0 140 +6.6 0.5 0.8 282 0.5 − I IRAS04181+2654A
TAU03 04:22:00.60 +26:57:32.0 140 +7.4f 0.4 0.2 196 1.0 − II IRAS04189+2650(W)
TAU04 04:27:02.60 +26:05:30.0 140 +6.3 1.4 1.5 161 0.8 0.64 I DGTAUB
TAU06 04:27:57.30 +26:19:18.0 140 +7.2 0.6 2.7 80 0.8 0.09 I HH31IRS2,IRAS04248+2612
TAU07 04:29:30.00 +24:39:55.0 140 +6.3f 0.6 0.2 169 0.9 − II HH414,IRAS04264+2433
TAU08 04:32:32.00 +22:57:26.0 140 +5.5g 0.5 1.2 300 0.5 0.18 II L1536IRS,IRAS04295+2251
TAU09 04:35:35.30 +24:08:19.0 140 +5.5 1.0 1.7 82 1.4 0.06 II L1535IRS,IRAS04325+2402
W4001 18:31:09.42 −02:06:24.5 436 +4.9 13.3 7.4 40 2.3 1.97 0+PDR W40-MM3
W4002 18:31:10.36 −02:03:50.4 436 +4.8 32.6 3.7 46 4.6 2.25 0 W40-MM5
W4003 18:31:46.54 −02:04:22.5 436 +6.4 8.3 20.6 15 − 3.37 PS?+PDR W40-MM26
W4004 18:31:46.78 −02:02:19.9 436 +6.7 6.1 9.4 16 − 1.69 PS?+PDR W40-MM27
W4005 18:31:47.90 −02:01:37.2 436 +6.5 5.9 27.3 14 − 1.97 PS?+PDR W40-MM28
W4006 18:31:57.24 −02:00:27.7 436 +6.6 4.1 2.2 33 − 0.31 PS?+PDR W40-MM34
W4007 18:32:13.36 −01:57:29.6 436 +7.4 3.6 3.3 36 0.9 0.25 0 W40-MM36
Notes.(a) FromGaussianfitstotheC18O J=3−2observations(seeTableA.9).(b) CalculatedasdiscussedinSect.A.7.(c) Evolutionaryclassi-
fication, see Sect. A.7 for details of the determination. PS=pre-stellar, PDR=narrow, bright 12CO J=10−9 emission consistent with a photon-
dominated region. (d) First additional names for Aquila, Serpens South and W40 are from Maury et al. (2011), ‘-emb’ names from Enoch
et al. (2009). (e) Sources off-centre in beam. Peak coordinates in PACS maps used for extraction of ground-based data: AQU01 18:29:03.61
−01:39:05.6;AQU0218:29:08.20−01:30:46.6;AQU0318:30:24.69−01:54:11.0;AQU0418:30:29.32−01:56:42.4.(f) FromGaussianfitsto
the13CO(J=3−2)observationsasC18Oisnotdetected.(g)TakenfromCasellietal.(2002).
region. Secondly, by excluding older Class I and flat-spectrum DIGIT are designed to probe, the addition of the WILL survey
sources,weintroduceabiastowardsyoungerClassIsources,so leavesthecombinedsamplebroadlycomplete.
thepropertiesofanaverageClassIsourcemaywellbeslightly
different from those determined with this sample. However, in
general for the part of parameter space that WILL, WISH and
5
J.C.Mottrametal.:Outflows,infallandevolutionofasampleofembeddedlow-massprotostars
3. Observationsandresults Few differences have been found in line-shape or gain be-
tween the H and V polarisations (e.g. Kristensen et al. 2012;
TheprimaryobservationsfortheWILLsurveyweretakenwith
Yıldız et al. 2013; Mottram et al. 2014), so after visual inspec-
Herschel1 usingtheHeterodyneInstrumentfortheFar-Infrared
tion the two polarisations were co-added to improve signal-to-
(HIFI,deGraauwetal.2010)andPhotodetectorArrayCamera
noise.Thevelocitycalibrationisbetterthan100kHz,whilethe
and Spectrometer (PACS, Poglitsch et al. 2010) detectors be- pointing uncertainty is better than 2(cid:48)(cid:48) and the intensity calibra-
tween the 31st October 2012 and 27th March 2013. The ob- tionuncertaintyis(cid:46)10%(Mottrametal.2014).
servingmodes,observationalproperties,datareductionandde-
tection statistics are described for each instrument separately
in Sections 3.1 and 3.2. Complementary spectroscopic maps 3.1.2. Results
obtained through follow-up observations of the sample with
Figures 2 and 3 present the observed HIFI ortho-H O 1 −1
ground-basedfacilitiesarethendescribedinSection3.3. 2 10 01
(557GHz) ground-state transition and 12CO J=10−9, respec-
tively, for all WILL sources. The water spectra are complex,
3.1. HIFI containingmultiplecomponents,someabsorption,whichisusu-
allynarrow,andemissionupto± ∼100kms−1 fromthesource
3.1.1. Observationaldetails
velocity, similar to other Herschel HIFI observations of water
HIFI was a set of seven single-pixel dual-sideband hetero- towards Class 0/I sources (e.g. Kristensen et al. 2012). 12CO
dyne receivers that combined to cover the frequency ranges J=10−9 typically shows two gaussian emission components
480−1250GHzand1410−1910GHzwithasidebandratioofap- withalowertotalvelocityextentthanH2O.Strong,narrowab-
proximatelyunity.Spectraweresimultaneouslyobservedintwo sorption in 12CO J=10−9 for W40 sources 01, 03 and 06 (see
polarisations, H andV,whichpointedatslightlydifferentposi- Fig. 3) indicates that contamination in at least one of the refer-
tions on the sky (∼6.5(cid:48)(cid:48) apart at 557GHz decreasing to ∼2.8(cid:48)(cid:48) ence positions affects these spectra and also likely affects most
at 1153GHz), with two spectrometers simultaneously provid- oftheH2Otransitionsforthesesourcesaswell.Thenarrowyet
ing both wideband (WBS, 4GHz bandwidth at 1.1MHz reso- brightnatureofthe12CO J=10−9seeninsixsources(OPH01,
lution)andhigh-resolution(HRS,typically230MHzbandwidth W4001andW4003−06,seeFig.3),combinedwiththenarrow
at250kHzresolution)frequencycoverage. andlow-intensitynatureoftheH2Oemission,suggeststhatthey
The HIFI component of the WILL Herschel observations arerelatedtophoton-dominatedregions(PDRs,c.f.forexample
consistsofsinglepointedspectraatfourfrequencysettings,prin- COobservationsoftheOrionBarPDR,Hogerheijdeetal.1995;
cipally targeting the H O 1 −1 , 1 −0 and 2 −1 tran- Jansenetal.1996;Nagyetal.2013).
2 10 01 11 00 02 11
sitions at 557, 1113 and 988GHz respectively and the 12CO Thedetectionstatisticsforalltransitionsaregiveninthelast
J=10−9 transition at 1152GHz, which also includes the H O column of Table 2, excluding W40 sources 01, 03 and 06 due
2
3b1e2a−m2-2s1wtirtacnhsmitioodne. Awlilthobasenrovdatoiofn3s(cid:48)wuseirnegcfaarsritecdhoopuptiinng.duTahle- ttoionthiescdoentetacmteidnatotiwonarodfst3h9e/s4e6sspoeucrtcrae.sTinhetoHta2lO, in1c10lu−d1i0n1gtr3a3n/s3i6-
specificcentralfrequenciesofthesettingswerechosentomax- confirmed Class 0/I sources (not detected in CHA02, PER04
imisethenumberofobservableH O,COandH18Otransitions, and W4007, see Fig. 2), while 12CO J=10−9 is detected to-
the details of which are given in2Table 2 along2 with the cor- wards40/46sourcesintotalincluding32/36Class0/Is(notde-
responding instrumental properties, spectral and spatial resolu- tectedinCHA02,PER07,PER15andW4007).H128O110−101
tion, and observing time. The main difference compared to the isonlydetectedtowardsthesourcewiththestrongestH2Oemis-
WISH HIFI observations of low-mass sources (see Kristensen sion,SERS02,whileC18OJ=9−8isonlydetectedtowardsfour
et al. 2012; Mottram et al. 2014) was that the frequency of the sources(PER02,SERS02,W4004and 05).
WILL observations for the H O 1 −1 and 1 −0 settings AmoredetailedanalysisofthekinematicsoftheHIFIlines
2 10 01 11 00
wassetsothatthecorrespondingH18Otransitionwasobserved is presented and discussed in San Jose´-Garc´ıa (2015), includ-
2
simultaneously, and longer observing times were used for the ingtheresultsofGaussiandecompositionofthelinesusingthe
H O1 −1 setting.TheobservationIDnumbersforallWILL methodsoutlinedfortheWISHsamplebyMottrametal.(2014)
2 10 01
HIFIobservationsaregiveninTableB.1. andSanJose´-Garc´ıaetal.(2013)forH2OandCO,respectively.
Initial data reduction was conducted using the Herschel In summary, the minimum number of Gaussian components is
Interactive Processing Environment (hipe v. 10.0, Ott 2010). found that results in no residuals above 3σ, with these com-
After initial spectrum formation, any instrumental standing ponentsthencategorisedbetweentheenvelopeandCorJ-type
waves were removed. Next, a low-order (≤2) polynomial base- outflow-relatedshocksdependingontheirwidthandoffsetfrom
line was subtracted from each sub-band. The fit to the baseline the source velocity. A global fit is used for the H2O transitions
wasthenusedtocalculatethecontinuumlevel,compensatingfor with the component peak velocity and line-widths constrained
the dual-sideband nature of the HIFI detectors (the initial con- byalllinesandtheintensityallowedtovarybetweentransitions
tinuumlevelisthecombinationofemissionfromboththeupper because the lines all have a consistent shape. The different CO
and lower sideband, which we assume to be equal). Following transitionsarefitindependentlyastheirlineprofileshapesvary
this the WBS sub-bands were stitched into a continuous spec- betweendifferenttransitions.
trumandalldatawereconvertedtotheT scaleusingthelat-
MB
est beam efficiencies (see Table 2). Finally, for ease of analy-
3.2. PACS
sis, all data were converted to FITS format and resampled to
0.3kms−1 spectral resolution on the same velocity grid using 3.2.1. Observationaldetails
bespokepythonroutines.
PACS consisted of four detectors, two photoconductor arrays
1 Herschel is an ESA space observatory with science instruments with16×25pixelsforintegralfieldunit(IFU)spectroscopyand
providedbyEuropean-ledPrincipalInvestigatorconsortiaandwithim- two bolometer arrays with 16×32 and 32×64 pixels for broad-
portantparticipationfromNASA. band imaging photometry. In IFU spectroscopy mode, obser-
6
J.C.Mottrametal.:Outflows,infallandevolutionofasampleofembeddedlow-massprotostars
1.0
AQU01 4 AQU02 6 AQU03 10 AQU04 9 AQU05 9
× × × × ×
0.5
0.0
1.0
AQU06 10 CHA01 10 CHA02 10 CRA01 10 OPH01 8 OPH02 8
× × × × × ×
0.5
0.0
1.0
PER01 10 PER02 6 PER04 10 PER05 7 PER06 3
× × × × ×
0.5
0.0
1.0
PER07 2 PER08 2 PER09 4 PER10 8 PER12 3 PER13 9
× × × × × ×
0.5
0.0
1.0
PER14 10 PER15 10 PER16 5 PER17 7 PER18 8
× × × × ×
0.5
0.0
1.0
PER19 10 PER20 3 PER21 7 PER22 6 SCO01 10 SERS01 5
× × × × × ×
0.5
0.0
1.0
SERS02 TAU01 10 TAU02 10 TAU03 10 TAU04 10
× × × ×
0.5
0.0
1.0
TAU06 10 TAU07 9 TAU08 10 TAU09 10 W4001 W4002 3
× × × × ×
0.5
0.0
1.0
W4003 W4004 6 W4005 4 W4006 10 W4007 10
) × × × ×
K
( 0.5
B
M
T 0.0
75 0 75 75 0 75 75 0 75 75 0 75 75 0 75
− 1 − − − −
v(km s )
−
Fig.2.H O1 −1 (557GHz)continuum-subtractedspectraforthefinalWILLsample.Allhavebeenrecentredsothatthesource
2 10 01
velocityisatzero.Thenumberintheupper-rightcornerofeachpanelindicateswhatfactorthespectrahavebeenmultipliedbyin
ordertoshowthemonacommonscale.
7
J.C.Mottrametal.:Outflows,infallandevolutionofasampleofembeddedlow-massprotostars
8 AQU01 5 AQU02 6 AQU03 5 AQU04 6 AQU05 5
× × × × ×
6
4
2
0
8 AQU06 6 CHA01 5 CHA02 5 CRA01 3 OPH01 0.5 OPH02 3
× × × × × ×
6
4
2
0
8 PER01 3 PER02 PER04 5 PER05 5 PER06 5
× × × ×
6
4
2
0
8 PER07 5 PER08 PER09 0.6 PER10 6 PER12 6 PER13 5
× × × × ×
6
4
2
0
8 PER14 7 PER15 6 PER16 6 PER17 6 PER18 4
× × × × ×
6
4
2
0
8 PER19 5 PER20 5 PER21 4 PER22 2 SCO01 5 SERS01 5
× × × × × ×
6
4
2
0
8 SERS02 TAU01 5 TAU02 5 TAU03 5 TAU04 5
× × × ×
6
4
2
0
8 TAU06 5 TAU07 6 TAU08 5 TAU09 5 W4001 0.1 W4002
× × × × ×
6
4
2
0
8 W4003 0.2 W4004 0.8 W4005 W4006 2 W4007 5
) × × × ×
K 6
( 4
B
M 2
T 0
25 0 25 25 0 25 25 0 25 25 0 25 25 0 25
− 1 − − − −
v (km s )
−
Fig.3.CO J=10−9continuum-subtractedspectraforthefinalWILLsample.Allhavebeenrecentredsothatthesourcevelocityis
at zero. The number in the upper-right corner of each panel indicates what factor the spectra have been multiplied by in order to
s8howthemonacommonscale.
J.C.Mottrametal.:Outflows,infallandevolutionofasampleofembeddedlow-massprotostars
Table2.PrinciplelinesobservedwithHIFI.
Species Transition RestFrequencya E /k A b n c η d θ e WBSresolution HRSresolution Obs.Timef Det.g
u b ul cr mb mb
(GHz) (K) (s−1) (cm−3) (H/V) ((cid:48)(cid:48)) (kms−1) (kms−1) (min)
o-H O 1 -1 556.93599 61.0 3.46×10−3 1×107 0.62/0.62 38.1 0.27 0.03 38 39/46
2 10 01
3 -2 1153.12682 249.4 2.63×10−3 8×106 0.59/0.59 18.4 0.13 0.06 13 7/46
12 21
p-H O 1 -0 1113.34301 53.4 1.84×10−2 1×108 0.63/0.64 19.0 0.13 0.06 28 28/46
2 11 00
2 -1 987.92676 100.8 5.84×10−3 4×107 0.63/0.64 21.5 0.15 0.07 36 25/46
02 11
o-H18O 1 -1 547.67644 60.5 3.29×10−3 1×107 0.62/0.62 38.7 0.27 0.07 38 1/46
2 10 01
p-H18O 1 -0 1101.69826 52.9 1.79×10−2 1×108 0.63/0.64 19.0 0.13 0.06 28 0/46
2 11 00
C18O 9−8 987.56038 237.0 6.38×10−5 2×105 0.63/0.64 21.5 0.15 0.07 36 4/46
CO 10−9 1151.98545 304.2 1.01×10−4 3×105 0.59/0.59 18.4 0.13 0.06 13 40/46
13CO 10−9 1101.34966 290.8 8.86×10−5 3×105 0.63/0.64 19.3 0.13 0.06 28 20/46
Notes. (a) Taken from the JPL database (Pickett et al. 2010). (b) Taken from Daniel et al. (2011) and Dubernet et al. (2009) for H O, the JPL
2
database (Pickett et al. 2010) for H18O and CO isotopologues. (c) Calculated for T=300K. (d) Taken from the latest HIFI calibration docu-
2
mentathttp://herschel.esac.esa.int/twiki/pub/Public/HifiCalibrationWeb/HifiBeamReleaseNote Sep2014.pdf.(e)Calculatedusingequation3from
Roelfsemaetal.(2012).(f) Totaltimeincludingon+offsourceandoverheads.(g) Numberofdetections.Duetocontaminationofthereference
positions,thestatusforobservationsofW40sources01,03and06cannotbedetermined.
Table 3. Wavelength ranges covered by WILL PACS line-scan solved line profiles in a few sources. All observations used a
settings. chopping/nodding observing mode with off-positions within 6(cid:48)
of the target coordinates. The obsids for WILL PACS observa-
Setting Wavelengths PrimaryTransitions
tionsaregiveninTableB.1.Foronesource,TAU08,PACSdata
(µm)
were not obtained because the coolant on Herschel ran out be-
78.6− 79.5 H2O423−312,615−524,CO33−32,OH foretheycouldbesuccessfullyobserved.
81.3− 82.2 H O6 −5 ,CO32−31
2 16 05 Data reduction was performed with hipe v.10 with
84.2− 85.0 H O7 −7 ,CO31−30,OH
2 16 07
89.5− 90.4 H O3 −2 ,CO29−28 CalibrationTree45,includingspectralflat-fielding(seeHerczeg
1 123.7−126.1 H2O422−311,CO21−20 etal.2012;Greenetal.2013a,formoredetails).Thefluxden-
2 04 13
157.0−158.0 [Cii] sitywasnormalisedtothetelescopicbackgroundandcalibrated
162.5−164.5 CO16−15,OH usingobservationsofNeptune,resultinginanoverallcalibration
168.3−170.0 uncertaintyinfluxdensitiesofapproximately20%(Karskaetal.
179.0−180.8 H2O212−101,221−212 2014b).1Dspectrawereobtainedbysummingoveranumberof
53.6− 55.0 spaxelschosenafterinspectionofthe2Dspectralmaps(Karska
63.0− 63.5 H O8 −7 ,[Oi] et al. 2013), with only the central spaxel used for point-like
2 2 18 07
107.3−109.7 H2O221−110,CO24−23 emission multiplied by the wavelength-dependent instrumental
189.0−190.5 correction factors to account for the PSF (see PACS Observers
Manual2).
vations were taken simultaneously in the red 1st order grating 3.2.2. Results
(102−210µm) and one of the 2nd or 3rd order blue gratings
(51−73µm or 71−105µm) over 5×5 spatial pixels (spaxels), An overview of the PACS spectra for all sources is shown in
which covered a 47(cid:48)(cid:48)×47(cid:48)(cid:48) field of view. For details of the 70, Fig. 4, while an overview of the detection of all transitions is
100and160µmPACS(and250,350and500µmSPIRE,Griffin giveninTableA.4.AnextensiveanalysisofthePACSdatafor
etal.2010)photometricmapsusedtodeterminethecontinuum WILL sources in the Perseus molecular cloud was published
fluxdensitiesfortheSEDs(discussedinSectionA.1)seeAndre´ in Karska et al. (2014b), while a global study of PACS spec-
etal.(2010). troscopy towards all WILL, DIGIT and WISH sources will be
WILL PACS observations were carried out using the IFU presentedinKarskaetal.(inprep.).Linefluxdensitieswereex-
in line-scan mode where deep observations were obtained for tractedfromthePACSdataasdescribedinKarskaetal.(2013).
targetedwavelengthregions(bandwidth∆λ/λ=0.01)aroundse- Thedetectionstatisticsforthemaintransitionsarealsogiven
lected transitions. Two wavelength settings were used, each in- in Table A.4. The most frequently detected line is [Oi], which
cluding observations in both the blue and red gratings, as sum- is detected in 42 out of 48 sources. Those sources not showing
marisedinTable3.Theprincipletransitionswithintheseregions [Oi] detections (AQU03−06, PER13 and W4006) are gener-
arefromH2O,OH,[Oi],COand[Cii],thepropertiesofwhich allynotdetectedinotherPACSlines.Thesesourceshaveweak
are given in Table A.3. While WILL targeted the key lines ob- and/or narrow lines, where detected, in the HIFI observations
served by WISH, some of the wavelength ranges were shifted (c.f.Fig.2).Thereare30sourcesdetectedinatleastonePACS
slightly in order to allow for better baseline subtraction or ad- water transition, while 27 are detected in at least one OH line
ditional line detections (e.g. those around 82 and 90µm were and 32 in at least one CO line, with a detection more likely in
shifted to slightly longer wavelengths) while others were omit- thelower-energytransitions.
tedtosavetime(e.g.aroundCOJ=14-13).Thevelocityresolu-
tion of PACS ranges from 75kms−1 at the shortest wavelength
to 300kms−1, with only [Oi] sometimes showing velocity re- 2 http://herschel.esac.esa.int/Docs/PACS/html/pacs om.html
9
J.C.Mottrametal.:Outflows,infallandevolutionofasampleofembeddedlow-massprotostars
Fig.4.Overviewofcontinuum-subtractedPACSspectraforselectedlines.ThesearenotcorrectedforthePSF.H O,COandOH
2
linesaremarkedinblue,redandcyan,respectively,withthe[Oi]markedingreen.They-axisofeachspectrumforalllinesexcept
[Oi] goes from 0 to 5Jy, with the brightest sources scaled down by the factor indicated in red below the source name. The [Oi]
spectraarescaledseparatelybyafactorbetween0.05and1.
3.3. Ground-basedfollow-up andregionsalreadyobservedinHCO+ J=4−3byCarneyetal.
(2016),sosuchobservationswereundertakentoconfirmtheem-
Follow-up ground-based observations were conducted towards
bedded protostellar nature of the sample (see Appendix A.7).
the WILL sample, where not already available, to complement Thefollow-upobservationsalsoincludedmapsof12CO J=3−2
the Herschel spectral line information. Approximately half of tocharacterisetheentrainedmolecularoutflowandC18OJ=3−2
the sources in the final catalogue were not part of the samples
10