Dense gas and the nature of the outflows

1.5 MB·English

by  I. Sepúlveda

Astronomy&Astrophysicsmanuscriptno.12916 (cid:13)c ESO2011
January14,2011
⋆,⋆⋆
Dense gas and the nature of the outflows
I.Sepu´lveda1,G.Anglada2,R.Estalella1,R.Lo´pez1,J.M.Girart3,andJ.Yang4
1 Departamentd’AstronomiaiMeteorologia,InstitutdeCie`nciesdelCosmos,UniversitatdeBarcelona,Mart´ıiFranque`s1,08028
Barcelona,Catalunya,Spain.
2 InstitutodeAstrof´ısicadeAndaluc´ıa,CSIC,CaminoBajodeHue´tor50,18008Granada,Spain.
3 InstitutdeCie`nciesdel’Espai(CSIC-IEEC),CampusUAB,FacultatdeCie`ncies,TorreC5-parell2,08193Bellaterra,Catalunya,
Spain.
4 PurpleMountainObservatory,ChineseAcademyofSciences,Nanjing210008,PRChina.
1 Received17July2009;Accepted12October2010
1
0
ABSTRACT
2
n Wepresent the results of theobservations of the(J,K) = (1,1) and the (J,K) = (2,2) inversion transitionsof the NH3 molecule
a towardalargesampleof40regionswithmolecularoropticaloutflows,usingthe37mradiotelescopeoftheHaystackObservatory.
J WedetectedNH3emissionin27oftheobservedregions,whichwemappedin25ofthem.Additionally,wesearchedforthe616−523
H Omaserlinetowardsixregions,detectingH Omaseremissionintwoofthem,HH265andAFGL5173.Weestimatethephysical
3 2 2
parametersoftheregionsmappedinNH andanalyzeforeachparticularregionthedistributionofhighdensitygasanditsrelationship
1 3
withthepresenceofyoungstellarobjects.Inparticular,weidentifythedeflectinghigh-densityclumpoftheHH270/110jet.Wewere

able to separate the NH emission from the L1641-S3 region into two overlapping clouds, one with signs of strong perturbation,
] 3
R probablyassociatedwiththedrivingsourceoftheCOoutflow,andasecond,unperturbedclump,whichisprobablynotassociated
withstarformation.Wesystematicallyfoundthatthepositionofthebestcandidatefortheexcitingsourceofthemolecularoutflow
S
ineachregionisveryclosetoanNH emissionpeak.Fromtheglobalanalysisofourdatawefindthatingeneralthehighestvalues
. 3
h ofthelinewidthareobtainedfortheregionswiththehighestvaluesofmassandkinetictemperature.Wealsofoundacorrelation
p betweenthenonthermallinewidthandthebolometricluminosityofthesources,andbetweenthemassofthecoreandthebolometric
- luminosity.WeconfirmwithalargersampleofregionstheconclusionofAngladaetal.(1997)thattheNH lineemissionismore
3
o intense toward molecular outflow sources than toward sources withoptical outflow, suggesting a possible evolutionary scheme in
r which young stellar objects associated with molecular outflows progressively lose their neighboring high-density gas, weakening
t
s boththeNH emissionandthemolecularoutflowintheprocess,andmakingopticaljetsmoreeasilydetectableasthetotalamount
3
a ofgasdecreases.
[

Keywords.ISM:jetsandoutflows–ISM:molecules–stars:formation
1
v
2
3 1. Introduction bothphenomenastartandcoexistintheearlystagesofthestar-
6 formationprocess.
Overthelastdecades,agreatefforthasbeenmadetostudythe
2 These outflows emanating from protostars collide with the
1. processes that take place in the earliest stages of stellar evolu- remainingmolecular cloud and disperse the surroundingmate-
tion. It is now widely accepted that low-mass stars begin their
0 rial, and determine the evolution of the dense core where the
livesinthedensestcoresofmolecularcloudsandthattheearliest
1 star is born (Arce & Sargent 2006). In this sense, the study of
stagesofstellarevolutionareassociatedwithprocessesinvolv-
1 thesemass-lossprocessesandthemolecularenvironmentofthe
ing a strong mass loss, traced by molecular outflows, Herbig-
: embeddedobjectsfromwhichtheyemanatehasbecameanim-
v Haro objects, and optical jets, which emanate from the deeply
portant tool in order to better understand the earliest stages of
i embeddedyoungstellarobjects.Thesemass-lossprocesseshave
X stellarevolution.
been proposed as a way to eliminate the excess of material
r Ammoniaobservationshaveprovedtobeapowerfultoolfor
a andofangularmomentumaswellastoregulatetheIMF(Shu,
studyingthedensecoreswherethestarsareborn.Sincethefirst
Adams&Lizano1987).Themolecularoutflowphaseisknown
surveysof dense cores(Torrelles et al. 1983, Benson & Myers
asoneoftheearliestobservablephasesofthestellarevolution.
1989,Angladaetal.1989),aclearlinkwasestablishedbetween
Severalstudiesindicatethatmost, if notall, ofthe Class 0and
dense cores, star formation and outflows (see e.g., the review
ClassIsourcesdrivemolecularoutflows(e.g.Davisetal.1999)
ofAndre´ etal. 2000).Fromthesesurveys,itwasclearlyestab-
and that an important fraction of these sources are associated
lishedthatthedrivingsourcesofoutflowsareusuallyembedded
with Herbig-Haro objects, as well as with molecular outflows
in the high-density gas, which is traced by the NH emission,
(Eiroaetal.1994;Persietal. 1994).These resultssuggestthat 3
andarelocatedveryclosetotheemissionpeak(Torrellesetal.
1983;Angladaetal.1989).Followingtheseresults,Angladaet
⋆ The Appendix is only available in electronic form at
al.(1997)(hereafterPaperI)undertookasurveyofdensecores
http://www.edpsciences.org
⋆⋆ Haystack Observatory data as CLASS files are to investigate the relationship between the type of outflow and
available in electronic form at the CDS via anony- the dense gas associated with their exciting sources. A statis-
mous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via tical study of the sources observed in that survey reveals that
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/vol/page theammoniaemissionismoreintensetowardmolecularoutflow
1
I.Sepu´lvedaetal.:Densegasandthenatureoftheoutflows
sourcesthantowardsourceswithonlyopticaloutflows,indicat-
ingthatmolecularoutflowsareassociatedwithalargeramount
of high-density gas. From this result, a possible evolutionary
scheme was suggested in which young objects associated with
molecular outflows progressively lose their neighboring high-
densitygas,whileboththeNH emissionandthemolecularout-
3
flowbecomeweakerintheprocess,andtheopticaljetsbecome
moreeasilydetectableasthetotalamountofgasandextinction
decreases.Inthissense,theobservationsofhigh-densitytracers,
suchastheNH molecule,confirmthedecreaseofhigh-density
3
gasaroundthestars.
We presentherenew ammoniaobservations.Additionalre-
gions allow us to obtain a sample of outflow regions observed
in ammonia that doubles the number used in Paper I. We se-
lected a sampleof 40star-formingregions,takingintoaccount
the presence of molecular outflows, optical outflows, or both,
and mapped with the Haystack 37 m telescope the NH emis-
3
sionaroundthesuspectedoutflowexcitingsources.InSect.2we
describe the observationalprocedure,in Sect. 3 we presentthe
observationalresults(thediscussionofindividualsourcesispre-
sentedinAppendixA),inSect.4wediscusstheglobalresults,
inSect.5wedescribetherelationshipbetweenthehigh-density
gas and the nature of the outflow based on the sample, and in
Sect.6wegiveourconclusions.
2. Observations
Weobservedthe(J,K)=(1,1)andthe(J,K)=(2,2)inversiontran-
sitionsoftheammoniamoleculewiththe37mradiotelescope
atHaystackObservatory1in1993January,1996Mayand1997
December. At the frequenciesof these transitions (23.6944960
GHz and 23.7226320GHz, respectively),the half power beam
widthofthetelescopewas1.′4andthebeamefficiencyatanel-
evation of 40◦ was ∼ 0.41 for the observations made in 1993
and ∼ 0.33 for the observations made in 1996 and 1997. In
all the observingsessions, we used a cooled K-band maser re-
ceiver and a 5000-channelautocorrelationspectrometerwith a
full bandwidth of 17.8 MHz. The calibration was made with
the standard noise-tube method. All spectra were corrected for
elevation-dependentgainvariationsandforatmosphericattenu-
ation.Thermspointingerrorofthetelescopewas∼10′′.Typical Fig.1. Spectra of the (J,K) = (1,1) inversion transition of the
NH moleculetowardthepositionsgiveninTable2forthede-
systemtemperatureswere∼100K,∼140Kand∼90Kforthe 3
tected sources. The vertical axis is the main beam brightness
observations made in 1993, 1996, and 1997, respectively. The
temperatureandthehorizontalaxisisthevelocityrelativetothe
observationsweremadeinthepositionswitchingmodein1993
centerofthemainline(asgiveninTable2).ForM120.1+3.0-N,
and1997andinfrequencyswitchingmodein1996.Duringthe
L1641-S3,HH270/110andIRAS20050,spectraattwodifferent
datareductiontheobservedspectraweresmoothedtoavelocity
resolutionof∼ 0.11kms−1,achievinga1σsensitivityof0.2K positions are shown. The spectrum of V1057 Cyg corresponds
totheaverageofpositionswithdetectedemissioninafive-point
perspectralchannel.
grid.
Wesearchedforammoniaemissioninthe40regionslistedin
Table1.Inallcases,wefirstmademeasurementsonafive-point
gridcenteredonthepositiongiveninTable1,withafullbeam
km s−1 for the NH (1,1) line and from ∼ 0.5 km s−1 to ∼ 3.8
separationbetweenpoints.TheNH (1,1)linewasdetectedin27 3
3
for the NH (2,2)line. The valuesof opticaldepth obtainedare
sources.TheNH (2,2)linewasobservedin15sourcesandwas 3
3
intherange0.1-5fortheNH (1,1)and0.1-0.5fortheNH (2,2)
detectedin10ofthem.TheobservedspectraoftheNH (1,1)and 3 3
3
line. We also used a single Gaussian fit to the main line to ob-
NH (2,2)linesatthepositionoftheemissionpeakareshownin
3
tainthemainbeambrightnesstemperatureatthepositionofthe
Figs.1and2.
emission peak. The values obtained for the main beam bright-
In Tables 2 and 3 we give the NH (1,1) and NH (2,2) line
3 3 nesstemperatureforthedetectedsourcesrangefrom∼0.3Kto
parametersobtainedfromamulticomponentfittothemagnetic
∼ 3KfortheNH (1,1)lineandfrom∼ 0.2Kto∼ 1Kforthe
hyperfinestructureatthepositionoftheemissionpeak.Thein- 3
trinsic line widths obtained range from ∼ 0.3 km s−1 to ∼ 3.6 NH3(2,2)line.
Additionally,wesearchedforthe6 -5 H Omaserline(at
16 23 2
1 RadioAstronomyatHaystackObservatoryoftheNortheastRadio thefrequencyof22.235080GHz)towardthereferenceposition
Observatory Corporation was supported by the National Science ofthesixsourceslistedinTable4.TheH2Oobservationswere
Foundation carried out in 1996 May 16 and 17 with the same spectrome-
2
I.Sepu´lvedaetal.:Densegasandthenatureoftheoutflows
Table1.RegionsobservedinNH
3
Region ReferencePositiona Observation Outflowb Ref. Molecular Ref. D Ref. Alternative
α(1950) δ(1950) Epoch Type Observations (pc) Name
M120.1+3.0-Nc 00h21m22s.0 +65◦30′24′′ 1993Jan CO 1 - - 850 1 -
M120.1+3.0-Sd 00h25m59s.8 +65◦10′11′′ 1993Jan CO 1 - - 850 1 -
L1287 00h33m53s.3 +63◦12′32′′ 1993Jan CO 2 HCO+,HCN,CS,NH3 2,3,4,5 850 2 RNO1B/1C
L1293 00h37m57s.4 +62◦48′26′′ 1993Jan CO 6 HCN,HCO+ 6 850 6 -
NGC281A-W 00h49m27s.8 +56◦17′28′′ 1993Jan CO 7 CS,NH3,HCN,HCO+,C18O,C34S 8,9,10,80 3500 9 S184
HH156 04h15m34s.8 +28◦12′01′′ 1997Dec jet 11 - - 140 11 CoKuTau1
HH159 04h23m58s.4 +25◦59′00′′ 1996May jet,CO 12,13 - - 160 12 DGTauB
HH158 04h24m01s.0 +25◦59′35′′ 1996May jet 14 C18O,CS 15,16 160 14 DGTau
HH31 04h25m14s.4 +26◦11′04′′ 1996May jet,CO? 11,79 CS,C18O 17,18 160 23 -
HH265 04h28m21s.0 +18◦05′35′′ 1996May HH 19 CS,NH3,C18O 81 160 20 L1551MC
L1551NE 04h28m50s.5 +18◦02′10′′ 1996May CO,jet 21,22 - - 160 20 L1551
L1642 04h32m32s.0 −14◦19′18′′ 1993Jan CO,HH 23,24 HCO+,C18O 25 200 25 HH123
L1634 05h17m13s.8 −05◦54′45′′ 1996May,1997Dec CO,H2,jet 26,27 - - 460 28 HH240/241,RNO40
HH59 05h29m52s.0 −06◦31′09′′ 1996May HH 29 - 460 29 -
IRAS05358 05h35m48s.8 +35◦43′41′′ 1993Jan CO 7 HCN,HCO+,CS,NH3,C34S 30,31,81 1800 7 -
L1641-S3 05h37m31s.7 −07◦31′59′′ 1993Jan,1996May CO 32 NH3,CS 33,34 480 32 -
HH68 05h39m08s.7 −06◦27′20′′ 1996May HH 29 460 29 -
CB34 05h44m03s.0 +20◦59′07′′ 1993Jan CO,jet,H2 35,36 C18O,CS,NH3,HCN 37,38,39,40 1500 41 HH290
HH270/110 05h48m57s.4 +02◦56′03′′ 1997Dec jet 42 C18O 83 460 42 L1617
IRAS05490 05h49m05s.2 +26◦58′52′′ 1993Jan CO 7 CS 8 2100 43 S242
HH111 05h49m09s.1 +02◦47′48′′ 1993Jan CO,jet,H2 44,45,46 CS 47 460 44 L1617
HH113 05h50m58s.1 +02◦42′49′′ 1996May jet 44 - - 460 44 L1617
AFGL5173 05h55m20s.3 +16◦31′46′′ 1996May CO 7 CS 8 2500 7 -
CB54 07h02m06s.0 −16◦18′47′′ 1993Jan CO 35 C18O,CS,HCN 37,38,40 1500 41 LBN1042
L1709 16h28m33s.5 −23◦56′32′′ 1996May CO 48 - - 160 49 -
L379 18h26m32s.9 −15◦17′51′′ 1993Jan CO 32 C18O,NH3 50,51 2000 32 -
L588 18h33m07s.6 −00◦35′48′′ 1997Dec CO?,HH 48,52 - - 310 52 HH108/109
CB188 19h17m57s.0 +11◦30′18′′ 1993Jan CO 35 HCN,CS,C18O 40,38,37 300 41 -
L673e 19h18m30s.8 +11◦09′48′′ 1996May CO 53 NH3,CS,C34S,HCN 54,55,56 300 57 RNO109
HH221 19h26m37s.5 +09◦32′24′′ 1996May jet 58 - - 1800 58 Parsamyan21
L797 20h03m45s.0 +23◦18′25′′ 1993Jan CO 35 HCN,CS,C18O 59,38,37 700 41 CB216
IRAS20050 20h05m02s.5 +27◦20′09′′ 1996May CO 60 CS,HCO+,HCN,C18O 60,61,78,84 700 62 -
V1057Cyg 20h57m06s.2 +44◦03′47′′ 1996May CO 63 - - 700 49 -
CB232 21h35m14s.0 +43◦07′05′′ 1993Jan CO 35 C18O,CS 37,38 600 41 B158
IC1396E 21h39m10s.3 +58◦02′29′′ 1993Jan CO 32 C18O,CS,NH3,HCN,HCO+ 64,65,66,10 750 32 GRS14,IC1396N
L1165 22h05m09s.6 +58◦48′06′′ 1997Dec CO,HH 48,67 - - 750 67 HHL75,HH354
IRAS22134 22h13m24s.2 +58◦34′12′′ 1996May CO 68 CS,C18O 86,88 2600 87 S134
L1221 22h26m37s.2 +68◦45′52′′ 1996May CO,HH 69,70 CS,HCO+,HCN,C18O 69 200 69 HH363
L1251e 22h37m40s.8 +74◦58′38′′ 1996May CO,HH 71,72 NH3,CS,C18O 54,55,73 300 74 -
NGC7538 23h11m35s.2 +61◦10′37′′ 1993Jan CO 75 HCN,CS,C34S,HCO+ 76,77,85 2700 75 -
Notes. (a) Positionwheretheobservationswerecentered.(b)CO=Molecularoutflow;HH=IsolatedHerbig-Haroobject;jet=Opticaloutflow;
H =Molecularhydrogenoutflow.(c) SeePaperIforH OresultsonIRAS00213+6530inthisregion(d) SeePaperIforH OresultsonIRAS
2 2 2
00259+6510inthisregion(e)AdditionalNH datawereobtainedin1990February(seePaperI).
3
References.(1)Yangetal.1990;(2)Yangetal.1991;(3)Yangetal.1995;(4)Estalellaetal.1993;(5)Carpenter,Snell&Schloerb1990;(6)
Yang1990;(7)Snelletal.1990;(8)Carpenteretal.1993;(9)Henningetal.1994;(10)Cesaronietal.1991;(11)Strometal.1986;(12)Mundt
etal.1991;(13)Mitchelletal.1994;(14)Mundtetal.1987;(15)Hayashietal.1994;(16)Ohashietal.1991;(17)Ohashietal.1996;(18)Onishi
etal.1998;(19)Garnavichetal.1992;(20)Snell1981;(21)Moriarty-Schievenetal.1995;(22)Devine,Reipurth&Bally1999;(23)Liljestro¨m
etal.1989;(24)Reipurth&Heathcote1990;(25)Liljestro¨m1991;(26)Davisetal.1997;(27)Hoddap&Ladd1995;(28)Reipurthetal.1993;
(29) Reipurth &Graham1988; (30) Cesaroni, Felli&Walmsley1999; (31) Zinchenko etal. 1997; (32) Wilkinget al. 1990; (33) Harjuet al.
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Codella&Scappini1998;(40)Afonso,Yun&Clemens1998;(41)Launhardt&Henning1997;(42)Reipurthetal.1996;(43)Blitzetal.1982;
(44)Reipurth&Oldberg1991;(45)Reipurth1989;(46)Gredel&Reipurth1993;(47)Yangetal.1997;(48)Parkeretal.1991;(49)Fukui1989;
(50)Kelly&Macdonald1996;(51)Kelly&Macdonald1995;(52)Reipurth&Eiroa1992;(53)Armstrong&Winnewisser1989;(54)seePaper
1;(55)Morataetal.1997;(56)Sandell,Ho¨glund&Kislyakov1983;(57)Herbig&Jones1983;(58)Staude&Neckel1992;(59)Scappinietal.
1998;(60)Bachiller,Fuente&Tafalla1995;(61)Gregersenetal.1997;(62)Wilkingetal.1989;(63)Levreault1988;(64)Wilkingetal.1993;
(65)Serabynetal.1993;(66)Weikardetal.1996;(67)Reipurthetal.1997;(68)Dobashietal.1994;(69)Umemotoetal.1991;(70)Altenet
al.1997;(71)Sato&Fukui1989;(72)Eiroaetal.1994b;(73)Satoetal.1994;(74)Kun&Prusti1993;(75)Kameyaetal.1989;(76)Caoetal.
1993;(77)Kameyaetal.1986;(78)Choi,Panis&EvansII1999;(79)Moriarty-Schievenetal.1992;(80)Megeath&Wilson1997;(81)Swift,
Welch&DiFrancesco2005;(82)Leurinietal.2007;(83)Choi&Tang2006;(84)Beltra´netal.2008;(85)Sandelletal.2005;(86)Beutheret
al.2002;(87)Sridharanetal.2002;(88)Dobashi&Uehara2001
terandbandwidthusedfortheNH observations.Wereacheda 3. Results
3
typical(1σ) sensitivity of 1 Jy per spectral channel.Of the six
sources observed in H2O, we only detected significant (> 3σ) In Table 5 we list the physical parameters of the molecular
H2O emission in two of them, HH 265 and AFGL 5173. The condensations, derived from the NH3 data given in Tables 2
spectraoftheseH2OmasersareshowninFig.3.InTable4we and 3, following the procedures explained in the footnotes of
givethemaserlineparametersobtainedfromaGaussianfit. Table 5. We mapped the NH (1,1) emission in all the detected
3
regions, except in V1057Cyg and L1551NE. Maps are shown
in Figs. A.1, A.3 to A.10, A.12 to A.23 and A.25 to A.30. In
V1057Cygtheemissionisveryweakinallpositions.Thespec-
3
I.Sepu´lvedaetal.:Densegasandthenatureoftheoutflows
Table2.NH (1,1)lineparameters
3
Region Positiona V b T (m)c ∆Vd τ e Aτ f N(1,1)g
LSR MB m m
(arcmin) (kms−1) (K) (kms−1) (K) (1013cm−2)
M120.1+3.0-N (2.8,1.4) −18.78±0.02 0.89±0.07 0.90±0.05 1.7±0.3 1.9±0.1 4.7–16.4
(0,0) −20.23±0.01 0.65±0.04 1.18±0.04 1.0±0.1 1.06±0.05 3.5–12.2
M120.1+3.0-S (0,0) −17.41±0.02 0.57±0.05 1.10±0.05 0.8±0.2 0.83±0.07 2.5–9.0
L1287 (0,0) −17.63±0.05 2.51±0.05 1.77±0.01 0.90±0.03 3.80±0.04 18.7–30.9
L1293 (0,0) −17.67±0.01 1.06±0.05 0.79±0.03 0.7±0.2 1.7±0.1 3.6–7.7
NGC281A-W (0,0) −30.32±0.04 0.54±0.07 2.2±0.1 1.3±0.3 0.93±0.07 5.6–27.0
HH156 (0,0) - ≤0.2 - - - -
HH159 (0,0) - ≤0.4 - - - -
HH158 (0,0) - ≤0.3 - - - -
HH31 (−7,0) +6.86±0.01 2.2±0.1 0.42±0.01 2.6±0.2 6.7±0.3 7.7–16.1
HH265 (−1.4,1.4) +6.68±0.01 1.9±0.1 0.40±0.02 2.5±0.3 5.7±0.4 6.3–14.0
L1551NE (0,0) +6.64±0.02 0.79±0.09 0.47±0.03 5.0±0.8 3.5±0.4 4.6–22.6
L1642 (0,0) - ≤0.1 - - - -
L1634 (1.4,0) +8.00±0.01 1.4±0.1 0.81±0.04 0.6±0.2 2.0±0.2 4.6–8.5
HH59 (0,0) - ≤0.3 - - - -
IRAS05358 (0,0) −16.89±0.01 1.44±0.05 2.32±0.03 0.67±0.07 1.95±0.05 12.6–24.6
L1641-S3 (0,0) +4.96±0.01 2.0±0.1 0.68±0.04 1.3±0.3 3.9±0.3 7.4–14.4
(−2.8,0) +3.76±0.01 1.8±0.2 0.30±0.02 3.3±0.5 7.0±0.3 5.8–13.2
HH68 (0,0) - ≤0.3 - - - -
CB34 (0,0) +0.72±0.02 0.77±0.06 1.37±0.06 0.4±0.2 0.99±0.07 3.8–8.3
HH270/110 (0,0) +8.86±0.02 0.67±0.06 0.65±0.04 1.3±0.3 1.3±0.1 2.4–8.9
(−2.8,0) +8.70±0.03 0.8±0.1 0.8±0.1 0.4±0.5 1.1±0.2 2.6–4.8
IRAS05490 (0,0) +0.78±0.03 0.41±0.05 1.5±0.1 0.1±0.4 0.45±0.02 1.9–3.0
HH111 (0,0) +8.72±0.02 0.56±0.06 0.78±0.08 0.4±0.3 0.7±0.1 1.6–3.9
HH113 (0,0) - ≤0.4 - - - -
AFGL5173 (0,0) - ≤0.2 - - - -
CB54 (0,0) +19.55±0.01 0.73±0.04 1.14±0.04 0.8±0.2 1.11±0.06 3.5–10.8
L1709 (0,0) - ≤0.4 - - - -
L379 (0,0) +18.89±0.01 2.87±0.05 2.84±0.02 1.86±0.03 5.98±0.05 47.2–87.9
L588 (0,0) +10.86±0.02 1.3±0.1 0.58±0.04 2.4±0.4 3.5±0.3 5.6–16.4
CB188 (0,0) - ≤0.2 - - - -
L673 (0,−1.4) +7.11±0.01 2.5±0.1 0.41±0.1 2.5±0.3 7.5±0.4 8.4–16.3
HH221 (0,0) - ≤0.2 - - - -
L797 (0,0) - ≤0.2 - - - -
IRAS20050 (0,−1.4) +6.86±0.02 1.7±0.2 0.93±0.04 3.4±0.3 5.6±0.4 14.4–38.7
(−1.4,1.4) +5.06±0.02 1.8±0.2 0.96±0.04 0.8±0.2 2.6±0.2 7.1–13.1
V1057Cygh (0,0) +4.30±0.04 0.3±0.1 0.58±0.09 ≤3i 0.3−0.7j 0.5–14.5
CB232 (0,0) +12.32±0.02 0.58±0.05 0.68±0.04 1.8±0.3 1.3±0.1 2.5–11.8
IC1396E (0,0) +0.53±0.02 0.86±0.05 1.89±0.04 0.8±0.1 1.22±0.05 6.1–16.6
L1165 (0,0) −1.64±0.04 0.35±0.08 0.6±0.1 3±1 0.9±0.2 1.6–13.4
IRAS22134 (0,0) −18.62±0.04 0.55±0.09 1.2±0.1 0.4±0.4 0.7±0.1 2.3–6.0
L1221 (0,0) −4.36±0.01 2.5±0.1 0.71±0.01 2.1±0.1 6.1±0.2 12.1–23.4
L1251k (0,0) - ≤0.2 - - - -
NGC7538 (0,−1.4) −56.22±0.02 1.9±0.1 3.57±0.05 0.35±0.06 2.32±0.06 23.1–32.8
Notes. (a) Position of the emission peak, where line parameters were obtained (inoffsets from the position given in Table 1). (b) Velocity of
theline peak withrespect tothe local standard of rest. (c) Main beam brightness temperature of themain lineof thetransition, obtained from
asingle Gaussian fit. For undetected sources a3σ upper limit isgiven. (d) Intrinsiclinewidth, obtained taking into account optical depth and
hyperfinebroadening,butnotthespectralresolutionofthespectrometer.(e)Opticaldepthofthemainlinederivedfromtherelativeintensitiesof
themagnetichyperfinecomponents.(f)Derivedfromthetransferequation,whereA= f[J(T )−J(T )]isthe“amplitude”(Paulsetal.1983), f
ex bg
isthefillingfactor,T istheexcitationtemperatureofthetransition,T isthebackgroundradiationtemperatureandJ(T)istheintensityinunits
ex bg
oftemperature.NotethatA≃ fT ,forT ≫T (g)Beam-averagedcolumndensityfortherotationallevel(1,1).Upperlimitisobtainedfrom
ex ex bg
N(1,1) e(1.14/Tex)+1 ∆V
=1.5821013 τ ,
" cm−2 # e(1.14/Tex)−1 m"kms−1#
whereT isderivedfromthetransferequationassumingafillingfactor f =1.IfT ≫T thebeamaveragedcolumndensityisproportionalto
ex ex bg
the“amplitude”A,andtheexplicitdependenceonT disappears,reducingto
ex
N(1,1) Aτ ∆V
=2.7821013 m ,
" cm−2 # (cid:20) K (cid:21)"kms−1#
providingthelowerlimitforthebeam-averagedcolumndensity(e.g.,Ungerechtsetal.1986). (h) Lineparameterswereobtainedbyaveraging
several positions of a five-point map. (i) Obtained by adopting a 3σ upper limit for the intensity of the satellite lines. (j) The highest value is
obtainedfromtheupperlimitofτ andthelowestvalueisobtainedassumingopticallythinemission.(k)Thisregionwasobservedandmappedin
m
PaperI.Theundetectionreferstothenewobservedpositions.
4
I.Sepu´lvedaetal.:Densegasandthenatureoftheoutflows
Table3.NH (2,2)lineparameters
3
Region Positiona V b T (m)c ∆Vd τ e Aτ f N(2,2)g
LSR MB m m
(arcmin) (kms−1) (K) (kms−1) (K) (1013cm−2)
M120.1+3.0-N (2.8,1.4) −18.4±0.1 0.15±0.06 0.9±0.2 0.2±0.1 0.17±0.03 0.2–0.7
(0,0) - ≤0.2 - - - -
L1287 (0,0) −17.57±0.02 0.98±0.05 1.93±0.04 0.27±0.04 1.13±0.02 2.9–4.8
L1293 (0,0) - ≤0.2 - - - -
HH31 (−7,0) 6.94±0.04 0.24±0.06 0.51±0.08 0.1 0.27±0.04 0.2–0.4
HH265 (−1.4,1.4) - ≤0.2 - - - -
IRAS05358 (0,0) −16.79±0.04 0.7±0.1 2.6±0.1 0.28±0.05 0.83±0.02 2.8–5.5
L1641-S3 (0,0) +5.1±0.1 0.3±0.1 1.2±0.1 0.1±0.1 0.30±0.03 0.5–1.0
CB34 (0,0) - ≤0.1 - - - -
CB54 (0,0) - ≤0.2 - - - -
L379 (0,0) +18.80±0.02 1.3±0.1 3.45±0.05 0.53±0.02 1.7±0.02 7.7–14.3
IRAS20050 (0,0) +6.46±0.05 0.7±0.1 1.9±0.1 0.5±0.1 0.93±0.04 2.3–5.5
CB232 (0,0) - ≤0.1 - - - -
IC1396E (0,0) +0.42±0.06 0.33±0.06 2.4±0.2 0.23±0.06 0.37±0.02 1.2–3.2
L1221 (0,0) −4.49±0.03 0.5±0.1 1.0±0.1 0.19±0.03 0.55±0.03 0.7–1.4
NGC7538 (0,0) −56.91±0.03 0.76±0.05 3.8±0.1 0.13±0.07 0.81±0.01 4.0–5.9
Notes. (a−d,f) SeefootnotesofTable2.(e) Opticaldepthofthe(2,2)mainlinederivedfromtheratioofthe(1,1)to(2,2)antennatemperatures
andtheopticaldepthofthe(1,1)line,assumingthesameexcitationtemperatureforbothtransitions.(g) Beam-averagedcolumndensityforthe
rotationallevel(2,2).Upperlimitisderivedfrom
N(2,2) e(1.14/Tex)+1 ∆V
=7.4691012 τ ,
" cm−2 # e(1.14/Tex)−1 m"kms−1#
assumingthatbothfillingfactorandexcitationtemperaturearethesameforthe(1,1)and(2,2)transitions.IfT ≫T ,thebeam-averagedcolumn
ex bg
densityisproportionaltothe“amplitude”A,andtheexplicitdependenceonT disappears,reducingto
ex
N(2,2) Aτ ∆V
=1.3121013 m ,
" cm−2 # (cid:20) K (cid:21)"kms−1#
providingthelowerlimitforthebeam-averagedcolumndensity(e.g.,Ungerechtsetal.1986).
Fig.2. Same as Fig. 1, for the (J,K)=(2,2) inversion transition
towardthepositionsgiveninTable3
Fig.3. Spectra of the H O masers detected in 1996 May 16 in
trumofthisregionshowninFig.1andthephysicalparameters 2
theregionsHH 265(bottom)andAFGL 5173(top)towardthe
listed in Table 5 were obtained by averaging several points of
positionsgiveninTable4
a five-point map. In L1551NE, we detected strong NH emis-
3
sion in four positions, but we were not able to map the region
(see§A.8).Asummaryoftherelevantinformation,takenfrom
5
I.Sepu´lvedaetal.:Densegasandthenatureoftheoutflows
Table4.H Omaserlineparameters Forthe sourcesof oursample thatare onlyassociated with
2
optical signs of outflow the NH emission is generally weak.
3
Among the nine proposed exciting sources of optical outflow
Region Positiona V b S c ∆Vd thatweobserved,onlyHH270andHH290IRSarefoundclose
LSR ν
(arcmin) (kms−1) (Jy) (kms−1) to an ammonia emission peak. In all the other cases, ammonia
emission is not detected or there is no known object near the
M120.1+3.0-N (2.8,1.4) - ≤1 -
HH265 (0,0) −9.13±0.07 2.2±0.6 1.1±0.2 ammoniamaximumthatcouldbeagoodcandidatetodrivethe
(0,0) −7.14±0.07 2.1±0.6 0.9±0.2 opticaloutflow.
L1634 (1.4,0) - ≤1.5 -
L1641-S3 (0,0) - ≤1 -
4.2.Physicalparametersofthedensecores
AFGL5137 (0,0) +6.92±0.02 11±1 0.61±0.06
L1221 (0,0) - ≤1.8 -
ThesizesofthecondensationsmappedinNH generallyrange
3
from ∼ 0.1 pc to ∼ 1 pc. A somewhat higher value of 2 pc is
obtainedfortheregionsNGC281A-W,IRAS22134+5834and
Notes. Obtained from a Gaussian fit to the line profiles observed on
NGC 7538, the most distant sources of our sample. We found
May1996.
evidence that several of the condensations mapped are elon-
(a)Positionobservedwherelineparametershavebeenobtained(inoff-
sets from the position given in Table 1). (b) Velocity of the line peak gated (as was noted by Myers et al. 1991). However, in many
with respect to the local standard of rest. (c) Flux density of the line regions our angular resolution is not good enough to allow us
peak.Forundetectedsourcesa3σupperlimitisgiven.(d)Fullwidthat to further discuss the morphology of the sources. A high an-
halfmaximum. gular resolution interferometric study may be relevant for the
sourcesofoursamplethatappearcompactinourpresentsingle-
dishstudy.Nevertheless,inseveralofthemappedregions(L673,
M120.1+3.0-N,IRAS20050+2720andL1293),wecandistin-
theliterature,aboutthesourcesassociatedwiththeseregionsis
guishseveralclumpsintheobservedNH structure.Inparticu-
giveninTable6. 3
lar, in the regions M120.1+3.0-Nand IRAS 20050+2720,two
We detected maser emission in the regions HH265 and
clumps with differentvelocities, but gravitationallybound,can
AFGL 5173(see Table 4). The positionof the maser in AFGL
beidentified.
5173coincideswiththatofIRAS05553+1631,sothatthemaser
Forthevaluesofthe kinetictemperatureobtainedforthese
could be excited by the IRAS source. We detected significant
maser emission in the velocity range from 6.5 to 7.2 km s−1. regions(seeTable5),theexpectedthermallinewidthsare≤0.2
km s−1. This value is significantly lower than the intrinsic line
Brand et al. (1994) detected highly variable H O emission to-
2 widthswehaveobtained,whichrangefrom0.3to3.8kms−1(see
wardthissourcebetween1989Marchand1991Januaryin the
velocityrangefrom−7.6to13.1kms−1.HowevernoNH emis- Table 2). This result suggests that the star formation process
3 probably introduces a significant perturbationin the molecular
sionwasdetectedtowardthesourceAFGL 5173(seeTable2).
environment.Thelowervaluefortheintrinsiclinewidthisfound
TheresultsforindividualsourcesarepresentedinAppendixA.
inthecomponentatV = 3.8kms−1 oftheL1641-S3region,
LSR
whoselinewidthsarealmostthermal.Althoughtowardtheposi-
tionofthesourceIRAS05375-0731boththe3.8kms−1and4.9
4. Generaldiscussion
kms−1 ammoniacomponentsareobserved,wearguein§A.11
thatonlythebroadlineemissionat4.9kms−1 islikelyassoci-
4.1.Locationoftheexcitingsourcesoftheoutflows
atedwiththisYSO,whilenoembeddedsourcesareknowntobe
Throughthe(J,K)=(1,1)and(2,2)inversiontransitionsofthe associatedwiththenarrowlineemissionat3.8kms−1.
ammoniamoleculewe studiedthe dense gasin a sample of 40 The highest value of the line width is obtained for NGC
regionswithsignsofstarformation,asindicatedbythepresence 7538,whichisalsotheregionwiththehighestvalueofthemass
ofoutflowactivity.Wedetectedammoniaemissionin27regions andkinetictemperatureofoursample.Ingeneral,wefoundthat
and mapped 25 of them. This high ratio of detections(67,5%) themoremassiveregionspresenthighervaluesofthelinewidth
is a clear indication of the strong association between outflow (see Tables 2 and 5). Also, higher values of the line width are
activityandNH3 emission.Thisresultalsoconfirmstheyoung foundforthemostluminoussources(seeTable6).InFig.4we
nature of the poweringsources of the outflows included in our plottheluminosityofthesourcesasafunctionofthenonthermal
sample,becausetheyappeartobestillassociatedwith(andmost linewidth(subtractingthethermalcomponentusingthederived
ofthemembeddedin)thedensegasfromwhichtheyhavebeen rotational temperature of the region), for the sources observed
formed. inthispaperandinPaperI.Butbecauseoursampleofsources
Inalmostallthemolecularoutflowregionsthatwemapped islimitedbythesensitivityofthetelescope,themostluminous
in NH , the emission peaks close (< 0.1 pc) to the position of sources are located mainly at larger distances than the less lu-
3
an object that was previously proposed as an outflow driving minous.Inorderto avoidthisbiasofluminositywith distance,
source candidate. The association with the ammonia emission we limitedouranalysistosourcescloserthan1 kpc.We found
peaksgivesfurthersupportto the identification of these candi- thattheluminosityandthenonthermallinewidtharerelatedby
datesastheoutflowdrivingsources,followingthecriterionpro- log(Lbol/L⊙)=(3.6±0.9) log(∆Vnth/kms−1)+(1.8±0.2)with
posedbyAngladaetal. (1989).TheregionIRAS05490+2658 acorrelationcoefficientof0.7.Asimilarcorrelationwasfound
istheonlyregionassociatedwithamolecularoutflowwherethe byJijinaetal.(1999).Thiscorrelationindicatesthatthemostlu-
NH emissionmaximumisfar(∼0.7pc)fromthepositionofthe minoussourcesproducealargeperturbationinthesurrounding
3
proposedexcitingsource;sincetheNH emissionpeakscloseto material.
3
thecenterofsymmetryoftheoutflow,forthisregionwesuggest WealsonotethatregionsassociatedwithCOmolecularout-
thattheexcitingsourcecouldbeanundetectedembeddedobject flow have mostly higher values of the line width than regions
locatedclosetotheNH emissionmaximum. withopticaloutflowonly.
3
6
I.Sepu´lvedaetal.:Densegasandthenatureoftheoutflows
Table5.PhysicalparametersoftheNH condensations
3
Region Sizea T b N(H )c Md M e n(H )f
rot 2 vir 2
(arcmin) (pc) (K) (1022cm−2) (M⊙) (M⊙) (103cm−3)
M120.1+3.0-N(2.′8,1.′4) 3.9×2.7 0.96×0.67 11.2 1.7−6.1 142−500 68 3.4
M120.1+3.0-N(0,0) 3.0×2.0 0.75×0.50 ≤15 ≥0.9 ≥45 89 ∼2.6
M120.1+3.0-S 3.7×2.4 0.91×0.59 ∼13.5 0.7−2.7 51−181 92 ∼2.8
L1287 3.8×1.9 0.93×0.48 17.4 4.6−7.6 259−429 220 11.3
L1293 2.7×2.0 1.26×0.94 ≤13 ≥1.1 ≥168 71 ∼7.7
NGC281A-W 1.9×1.6 1.88×1.62 ∼20 1.3−6.2 505−2413 871 ∼1.3
HH31 2.8×2.0 0.11×0.08 9.7 3.7−7.6 4−9 2 12.4
HH265 4.2×2.3 0.20×0.11 ≤9 ≥3.3 ≥9 2 ∼11.3
L1551NE 1.4×1.4 0.07×0.07 ∼25 1.0−5.1 0.6−3 1.6 ∼1.1
L1634 2.6×2.1 0.34×0.28 ∼12 1.6−2.9 19−35 21 ∼13.1
IRAS05358 3.1×1.9 1.60×0.98 20.6 2.9−5.6 575−1121 707 5.9
L1641-S3(V ∼4.9km/s) 3.8×2.2 0.53×0.31 12.6 2.4−4.6 49−96 20 10.1
L1641-S3(V ∼3.8km/s) 5.8×2.8 0.81×0.39 13.5 1.7−3.9 68−157 5 6.2
CB34 2.0×1.7 0.89×0.76 ≤12 ≥1.3 ≥111 162 ∼7.8
HH270/110(0,0) 1.4×1.6 0.19×0.21 ∼13.6 0.7−2.6 3.5−13.3 9 ∼2.5
HH270/110(−2.′8,0) 2.8×1.7 0.37×0.23 ∼13.6 0.8−1.4 8−15 22 ∼10.0
IRAS05490 2.6×1.7 1.59×1.05 ∼15.5 0.5−0.8 104−168 304 ∼14.3
HH111 1.6×1.8 0.22×0.23 ∼13 0.5−1.2 3−8 14 ∼5.6
CB54 1.7×1.6 0.74×0.68 ≤15 ≥1.0 ≥62 96 ∼3.3
L379 2.0×2.0 1.16×1.16 17.8 11.4−21.2 1948−3628 982 7.6
L588 4.1×1.9 0.37×0.17 ∼8 4.1−11.8 32−94 9 ∼7.5
L673(SE)g 2.2×2.0 0.19×0.17 ≤12 ≥2.8 ≥12 3 ∼10.9
IRAS20050(0,−1.′4) 3.1×2.0 0.63×0.41 16.8 3.6−9.7 117−315 46 3.6
IRAS20050(−1.′4,1.′4) 3.0×2.0 0.61×0.41 16.8 1.8−3.3 56−103 49 8.2
V1057Cyg 1.4×1.4 0.29×0.29 ∼10 0.2−6.5 2−67 10 0.3−0.7
CB232 2.6×2.5 0.45×0.43 ≤11 ≥0.9 ≥23 21 ∼2.2
IC1396E 3.2×1.9 0.70×0.42 19.1 1.4−3.9 54−145 191 3.2
L1165 3.5×2.3 0.76×0.49 ∼9 0.9−7.3 41−347 23 ∼1.3
IRAS22134 3.1×2.3 2.34×1.74 ∼15.8 0.6−1.5 310−787 283 ∼4.3
L1221 2.1×2.0 0.12×0.11 12.5 3.9−7.6 7−13 6 10.5
NGC7538 2.5×2.4 1.96×1.92 28.3 5.3−7.5 2514−3571 2599 12.2
Notes. (a) Major andminoraxesofthehalf-power contour oftheNH emission.ForsourcesL1551NEandV1057Cygthesizeofthebeam
3
has been adopted. (b) Rotational temperature, derived from the ratio of column densities in the (1,1) and (2,2) levels (given in Tables 1 and
2, respectively), for the sources where the (2,2) line was detected. For the sources undetected in the (2,2) line, an upper limit was obtained
assuming optically thin emission. For sources not observed in the (2,2) line, we assumed that T (CO) = T (22−11) = T , where the CO
ex rot k
dataarefromYangetal.1990(M120.1+3.0-S),Henningetal.1994(NGC281A-W),Moriarty-Schievenetal.1995(L1551NE),Reipurth&
Oldberg1991(HH270/110 andHH111),Snelletal.1990(IRAS05490), Parkeretal.1991(L588andL1165),Levreault1988(V1057Cyg)
andDobashietal.1994(IRAS22134).ForL1634,T =12Khasbeenadopted.(c)Beam-averagedH columndensity,obtainedfromtheNH
rot 2 3
columndensityadoptinganNH abundanceof[NH /H ]=10−8(seeAngladaetal.1995foradiscussiononNH abundances).TheNH column
3 3 2 3 3
densityisobtainedassumingthatonlytherotationalmetastablelevelsoftheNH aresignificantlypopulatedattheirLTEratioscorrespondingto
3
T =T (22−11).(d)Massofthecondensation,derivedfromthebeam-averagedH columndensityandtheobservedarea.(e)Virialmassobtained
k R 2
from[Mvir/M⊙]=210[R/pc][∆V/kms−1]2,whereRistheradiusoftheclump,takenashalfthegeometricalmeanofthemajorandminoraxes,and
∆V istheintrinsiclinewidthgiveninTable2.(f) Volumedensity,derivedfromthetwo-levelmodel(Ho&Townes1983).(g) Parametersofthe
southeasternclump.ParametersofthenorthwesternclumparegiveninPaperI.
Partlybecauseofourlackofangularresolution,wearenot density (∼ 1023 cm−2, corresponding to a visual extinction of
able to measure the velocity gradient in our regions in detail. ∼ 100 mag), suggesting that this object is very deeply embed-
However,itisremarkablethatinL1287ourresultsshowastrong ded.
velocitygradientwithsuddenvelocityshiftsofupto∼1kms−1
between contiguous positions. A high angular resolution VLA The masses we obtained for the observed regions cover a
studyofthisregion(Sepu´lvedaetal.inpreparation)showsthat wide range of values, from 1 to 3000 M⊙ (the highest value
this region also exhibits a complex kinematics at small scale. corresponds to the NGC 7538 region). Most of the sources of
Moreover,intwocases(M120.1+3.0-NandIRAS20050+2720) oursamplearelow-massobjects,andthevaluesofthemassob-
theobservedvelocitydistributioniscompatiblewithtwoclumps tained for their associated high-density cores are smaller than
thataregravitationallybound.TheregionL1641-S3exhibitstwo 100 M⊙. In general, the values derived for the mass coincide
velocitycomponentsseparatedby∼1kms−1thatweinterpreted withthevirialmasswithinafactorof3.Thisoveralltrendsug-
astwodistinctclumpsofemission. geststhatmostoftheobservedcondensationsarenearthevirial
The H columndensities we obtainedare generally ∼ 1022 equilibrium and that the assumed NH abundance is adequate.
2 3
cm−2(assuming[NH /H ]=10−8),implyingmeanvisualextinc- However, we found four sources (HH 265, L588, L673, IRAS
3 2
tionsof∼10mag.ForL379weobtainedthehighestH column 20050+2720)forwhichthederivedmassexceedsthevirialmass
2
7
I.Sepu´lvedaetal.:Densegasandthenatureoftheoutflows
Table6.SummaryofpropertiesofrelevantsourcesintheregionsdetectedinNH
3
Region IRAS L Ref. Evolutionary Ref. Detectionat Ref. HO Ref. Outflow Ref.
bol 2
(L⊙) status otherwavelengths maser? source?
M120.1+3.0-N 00213+6530 12.9 1 - - mm,cm 109 Yes 2 Yes 1
00217+6533 12.0 1 - - - - - - ? 3
M120.1+3.0-S 00259+6510 9.9 1 - - - - No 4 Yes 1
00256+6511 20.3 1 - - - - - - ? 3
L1287 00338+6312 1800 5 ClassI?a 6 NIR,MIR,smm,mm,cm 7,95,8,9,10 Yes 6 ? 11
L1293 00379+6248 <21 12 - - - - Yes 13 Yes 12
NGC281A-W 00494+5617 8790 14 -a - NIR,FIR,mm 7,15,14 Yes 16 Yes 11
HH31 04248+2612 0.36 17 ClassI 17 NIR,FIR,smm,mm 17,18,19,20 No 13 Yes 21
L1551NE 04288−1802 3.9 22 Class0 23 NIR,smm,mm,cm 24,19,20,25 - - Yes 23
L1634 05173−0555 17 26 Class0 27 NIR,FIR,smm,mm,cm 28,18,29,24,27 No 30 Yes 28
IRS7b 0.03c 27 ClassI/0 27 NIR,smm 28,27 - - Yes 28
IRAS05358 05358+3543 6300 31 HerbigAe/Be?a 32 NIR,MIR,smm,mm 33,32,104,96,31 Yes 34 Yes 11
L1641-S3 05375−0731 100 35 ClassI 36 NIR,FIR,smm,mm,cm 36,37,29,35,38, Yes 39 Yes 40
CB34 05440+2059 130 41 ClassI 42 NIR,smm,mm,cm 42,43,41,44 Yes 58 Yes 45
HH270/110 05487+0255 7 46 ClassI 46 NIR,FIR,cm 47,46,48 No 49 Yes 46
05489+0256 5.3 50 ClassI 50 NIR,mm,cm 50,97,48 - - Yes 51
IRAS05490 05490+2658 4200 11 ClassI?a 7 NIR,FIR,cm 7,15 No 16 Yes 11
HH111 05491+0247 25 46 Class0 52 NIR,smm,mm,cm 53,26,54,55 No 30 Yes 46
CB54 07020−1618 400 43 ClassI 41 NIR,MIR,smm,mm,cm 56,105,42,43,57 Yes 58 Yes 45
L379 18265−1517 16000 59 -a - smm,mm,cm 59,8 Yes 60 Yes 40
L588 18331−0035 3.7 26 ClassI 61 NIR,mm 103,61 - - ? 61
IRAS20050 20050+2720 206 62 Class0 63 NIR,FIR,mm,cm 64,65,66,67 Yes 68 Yes 63
20049+2721 236d - - - NIR,cm 64,67 - - ? -
V1057Cyg 20571+4403 200 69 FUOr 70 NIR,IR,FIR,cm,mm,smm 71,72,73,74 Yes 75 Yes 76
CB232 21352+4307 14 41 ClassI 42 NIR,mm,smm 42,41,77 Yes 58 Yes 45
IC1396E 21391+5802 440 78 Class0 78 NIR,FIR,mm,smm,cm,X-ray 79,80,78,98,106 Yes 34 Yes 40
L1165 22051+5848 120 81 ClassI/FUOr 81 NIR 81,82 No 83 Yes 84,85
IRAS22134 22134+5834 7943 111 -a - NIR,FIR,mm 107,86,108 No 110 Yes 86
L1221 22266+6845 2.7 87 ClassI 102 NIR,mm 103,99 No 88 Yes 87
NGC7538 IRS1-3b ∼250000 89 -a - NIR,FIR,mm 89,90 Yes 91,92 Yes 93
IRS9b ∼60000 89 -a - NIR,FIR,mm,cm,smm 89,100,101 Yes 92 Yes 93
IRS11b 10000 67 -a - FIR,mm,smm 89,90 Yes 92 Yes 93
Notes. (a)Probablyyoungmassivestar/stars.(b)NIRsource.NoIRASsourceatthisposition.(c)Submillimeterluminosity.(d)IRASluminosity.
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Launhardt,Ward-Thompson&Henning1997;(44)Yunetal.1996;(45)Yun&Clemens1994a;(46)Reipurth&Olberg1991;(47)Garnavichet
al.1997;(48)Rodr´ıguezetal.1998;(49)Pallaetal.1993;(50)Reipurth,Raga&Heathcote1996;(51)Reipurthetal.1996;(52)Cernicharo,Neri
&Reipurth1997;(53)Gredel&Reipurth1993;(54)Stapelfeldt&Scoville1993;(55)Rodr´ıguez&Reipurth1994;(56)Yun&Clemens1994b;
(57)Moreiraetal.1997;(58)Go´mezetal.2006;(59)Kelly&Macdonald1996;(60)Codella,Felli&Natale1996;(61)Chinietal.1997;(62)
Gregersenetal.1997;(63)Bachiller,Fuente&Tafalla1995;(64)Chenetal.1997;(65)DiFrancescoetal.1998;(66)Choi,Panis&EvansII
1999;(67)Anglada,Rodr´ıguez&Torrelles1998a;(68)Brandetal.1994;(69)Kenyon1999;(70)Herbig1977;(71)Greene&Lada1977;(72)
Kenyon&Hartmann1991;(73)Rodr´ıguez&Hartmann1992;(74)Weintraub,Sandell&Duncan1991;(75)Rodr´ıguezetal.1987;(76)Evans
IIetal.1994;(77)Huardetal.1999;(78)Sugitanietal.2000;(79)Wilkingetal.1993;(80)Saracenoetal.1996;(81)Reipurth&Aspin1997;
(82)Tapiaetal.1997;(83)Persi,Palagi&Felli1994;(84)Parkeretal.1991;(85)Reipurthetal.1997;(86)Dobashietal.1994;(87)Umemoto
etal.1991;(88)Claussenetal.1996;(89)Werneretal.1979;(90)Akabaneetal.1992;(91)Genzel&Downes1977;(92)Kameyaetal.1990;
(93)Kameyaetal.1989;(94)Minchin&Murray1994;(95)Quanzetal.2007;(96)Leurinietal.2007;(97)Choi&Tang2006;(98)Beltra´net
al.2002b;(99)Lee&Ho2005;(100)Sa´nchez-Mongeetal.2008;(101)Sandelletal.2005;(102)Leeetal.2002;(103)Connelley,Reipurth&
Tokunaga2007;(104)Longmoreetal.2006;(105)Ciardi&Go´mez-Mart´ın2007;(106)Getmanetal.2007;(107)Kumaretal.2006;(108)Wu
etal.2007;(109)Busquetetal.2009;(110)Sridharanetal.2002;(111)Williamsetal.2005
byalargefactor(>5).Thisresultcouldimplythattheseclouds paper and in Paper I, using only sources with D ≤ 1 kpc.
arestillintheprocessofgravitationalcollapse. We found that both parameters are related by log(Lbol/L⊙) =
Recently,Wuetal.(2010)findastrongcorrelationbetween (0.8±0.2) log(Mcore/M⊙)+(0.2±0.3)withacorrelationcoef-
the luminosity of a sample of high-mass sources and the mass ficientof0.6.Thecorrelationwefoundforthissampleislower
of the cores, traced by several high-density tracers. Although thanthevaluewewouldobtainforthecompletesample,includ-
their sample spans a wide range of distances, they assume that ingthemoredistantsources.Althoughforthecompletesample
there is no distance effect on the clump masses. In order to the correlation can be caused by the distance bias of the sam-
check this correlation, and to ensure that there is no distance ple (more luminous sources are, in general, more distant), for
biasinoursample(seeabove),weselectedsourcescloserthan1 the sources closer than 1 kpc there is still a significant corre-
kpc. In Fig. 5 we plot the luminosity of the source as a func- lation between luminosity and core mass, and this correlation
tion of the mass of the core for the sources observed in this isnotcausedbyanydistancebias.Thisresultindicatesthatthe
8
I.Sepu´lvedaetal.:Densegasandthenatureoftheoutflows
Fig.4.Bolometricluminosityvs. nonthermallinewidthforthe
observedregionswith D ≤ 1 kpc (regionsobservedin Paper I
arealsoincluded).
Fig.6. Distributionof the NH mainbeam brightnesstempera-
3
ture (left) and the NH columndensity (right)for sourceswith
3
only molecular outflow (top), sources with both molecular and
opticaloutflow(middle),andsourceswithonlyopticaloutflow
(bottom).
Fig.5. Diagram of bolometric luminosity vs. mass of the core Inordertosubstantiatetherelationshipbetweenthetypeof
for the observed regions with D ≤ 1 kpc (regions observed in outflowandtheintensityoftheammoniaemission,herewecon-
PaperIarealsoincluded) tinuethestudywebeganinPaperI,withamorecompletesam-
pleofregions.Thesampleincludestheregionsobservedinthe
present paper, the sources reported in Paper I, and also the re-
sults of other Haystack NH observationsreported in the liter-
sourcesformedinmassiveclumpscanaccretemorematerialand 3
ature. We studied the distribution of the intensity of the NH
formmoremassivestarsthatarealsomoreluminous. 3
emission,asmeasuredbythemainbeambrightnesstemperature
toward the outflow exciting source in this large sample of re-
gions.Asthemainbeambrightnesstemperatureisagoodmea-
5. Evolutivedifferencesintheoutflowsources
sure of the intensity of the NH emission only for sources that
3
We detectedand mappedthe NH emission in 24 outof 30re- fillthebeamofthetelescope,weincludedinthesampleonlythe
3
gions associated with molecular outflow in our sample (80%). sources whose angular size of the ammonia emission is higher
In four of the six regions where we failed in detecting ammo- thanthetelescopebeam.Thus,weusedonlysourceswithD≤1
nia emission, the evidence for CO outflow is weak. In the 24 kpc.
regionsassociatedwithmolecularoutflow,theNH emissionis Our final sample is presented in Table 7. It containsa total
3
usuallystrong;theammoniaemissionisfaint(T ≤0.5K;see of 79 sources, with 30 sources associated with only molecular
MB
Table2)onlyinthreeregions(IRAS05490+2658,V1057Cyg outflow,40 sourcesassociated with both molecularand optical
and L1165). On the other hand, in the regions without molec- outflowsand9sourceswithonlyopticaloutflow.
ular outflow, the ammonia emission is usually undetectable or InFig. 6 (left)we presentthe distributionof the NH main
3
veryfaint.Theseresultsagreewellwiththeresultsweobtained beambrightnesstemperaturetowardthepositionoftheproposed
in Paper I, where we studied the relationship between the type outflowexcitingsource(Table7)forthethreegroupsofsources.
of outflow and the intensity of the NH emission from a small ThemeanvaluesoftheNH brightnesstemperaturearehT i=
3 3 MB
sampleofsources. 0.42Kforregionswithonlyopticaloutflow,hT i=1.35Kfor
MB
9
I.Sepu´lvedaetal.:Densegasandthenatureoftheoutflows
regionswithopticalandmolecularoutflow,andhT i=1.34K theexcitingsource).On the otherhand,the sourcesassoci-
MB
forsourceswithmolecularoutflowonly. atedwith opticaloutflow(exceptHH 270IRSand HH 290
Clearlythesourceswithonlyopticaloutflowtendtopresent IRS)arenotassociatedwithanammoniaemissionpeak.
lower valuesof the NH brightnesstemperature,while the dis- 2. Fourregions(HH265,L588,L673andIRAS20050+2720)
3
tributionforsourceswithmolecularoutflowisshiftedtohigher couldbe inthe processofgravitationalcollapseatscales ≥
valuesofthebrightnesstemperature.Thedisplacementtohigher 0.2 pc, as their derived masses exceed the virial mass by a
valuesofT issimilarforsourceswithonlymolecularoutflow factor> 5.Therestofammoniacondensationsappeartobe
MB
asforsourceswithbothopticalandmolecularoutflow.Thiswas closetothevirialequilibrium.
an expected result, because recentstudies with high sensitivity 3. Inseveralregionstheammoniastructurepresentsmorethan
detectorsarerevealingweakHHobjectstowardregionsofhigh oneclump.IntheM120.1+3.0-NandIRAS20050+2720re-
visualextinction,where previousobservationsfailed in the de- gions,twoclumpswithdifferentvelocities,whicharegravi-
tection. In our study, we did not take into account differences tationallyboundthoughwereidentified.
inthebrightnessoftheHerbig-Haroobjectsorinthestrengthof 4. We identified a high-densityclump where the HH 270/110
themolecularoutflow.Weconclude,therefore,thattheammonia jet can suffer the collision responsible for the deflection of
emissionisingeneralmoreintenseinmolecularoutflowsources thejet.
thaninsourceswithoutmolecularoutflow. 5. WewereabletoseparatetheNH emissionfromtheL1641-
3
Asimilarresultisobtainedforthederivedammoniacolumn S3 region into two overlapping clouds, one with signs of
densities. In Fig. 6 (right) we show the distribution of the de- strong perturbation, probably associated with the driving
rived ammonia column density (Table 7) for the three groups source of the CO outflow, and a second, quiescent clump,
of sources. We note that the distribution for sources with CO whichprobablyisnotassociatedwithstarformation.
outflow is shifted to higher values of the NH3 column density, 6. In general, the observed NH3 condensations are very cold,
whileforsourceswithonlyHHoutflowthedistributiontendsto with line widths dominated by nonthermal (turbulent) mo-
lowervalues.ThemeanvaluesfortheNH columndensityare tions. Among the observed sources, the more massive re-
3
hN(NH )i = 5.2× 1013 cm−2 for regions with optical outflow gionsappeartoproducealargerperturbationintheirmolec-
3
only, hN(NH )i = 1.94×1014 cm−2 for sources with molecu- ularhighdensityenvironment.
3
lar and optical outflow and hN(NH )i = 2.49×1014 cm−2 for 7. Wefoundthatgenerallythemoreluminousobjectsareasso-
3
sourceswithmolecularoutflowonly. ciated with broader ammonia lines. A correlation between
Recently, Davis et al. (2010) find from a study of outflows the nonthermal component of the line width and the lu-
andtheirexcitingsourcesintheTaurusregionthatsourcesdriv- minosity of the associated object, log(Lbol/L⊙) = (3.6 ±
ingCOoutflowshavereddernear-IRcoloursthansourcesdriv- 0.9) log(∆Vnth/kms−1)+(1.8±0.2)was foundforsources
ingHHjets,andtheyconcludethatCOoutflowsourcesaremore withD≤1kpc.
embedded in the high-density gas than the HH optical outflow 8. We found that there is a significant correlation between
sources.Thisresultagreeswellwithours. the luminosity of the source and the mass of the core and
All these results can be interpreted as an indication that that this correlation is not caused by any distance bias in
molecularoutflowsourcesareyounger,sincetheyareassociated the sample. Both parametersare related by log(Lbol/L⊙) =
withalargeramountofhigh-densitygas.Asthestarevolves,the (0.8±0.2) log(Mcore/M⊙)+(0.2±0.3).
surroundingmaterialbecomeslessdense,decreasingtheammo- 9. Theammoniabrightnesstemperatureandcolumndensityof
nia column density, and at the same time making the Herbig- thesourcesdecreaseastheoutflowactivitybecomespromi-
Haroobjectsdetectable.Atthetimewhenthemolecularoutflow nent in the optical. These results give an evolutive scheme
hasdisruptedandsweptoutthemolecularmaterialsurrounding inwhichyoungobjectsprogressivelylosetheirsurrounding
theYSO,boththeCOoutflowandtheNH columndensityare high-density gas. The ammonia emission and the observa-
3
expectedtobeweak,andonlytheHerbig-Haroobjectswouldbe tionalappearanceofoutflowstraceanevolutivesequenceof
observable. sources.
Theammoniaemissionandtheobservationalappearanceof
Acknowledgements. I.S.acknowledgestheInstitutodeAstrof´ısicadeAndaluc´ıa
outflowstraceanevolutivesequenceofsources.Molecularand forthehospitalityduringpartofthepreparationofthispaper.G.A.,R.E.,R.L.
opticaloutflowwouldbephenomenathatdominateobservation- andJ.M.G.acknowledgesupportfromMCYTgrantAYA2008-06189-C03(in-
allyatdifferentstagesoftheYSOevolution.Inyoungerobjects, cludingFEDERfunds).G.A.acknowledges supportfromJuntadeAndaluc´ıa,
Spain.
molecular outflows will be prominent, while optical outflows
willprogressivelyshowupastheYSOevolves.
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