MNRAS000,1–6(2016) Preprint6January2017 CompiledusingMNRASLATEXstylefilev3.0 Early Science with the Large Millimetre Telescope: Molecules in the Extreme Outflow of a proto-Planetary Nebula A.I. Go´mez-Ruiz,1⋆ L. Guzman-Ramirez,2,3, E. O. Serrano4, D. Sanchez-Arguelles4, 7 A. Luna4, F. P. Schloerb5, G. Narayanan5, M. S. Yun5, R. Sahai6, A. A. Zijlstra7, 1 0 M. Chavez-Dagostino4, A. Montan˜a1, D. H. Hughes4, M. Rodr´ıguez4 2 1 CONACYT–InstitutoNacional de Astrof´ısica, O´pticay Electro´nica, LuisE. Erro 1, 72840 Tonantzintla, Puebla, M´exico n 2 European Southern Observatory,Alonso de Co´rdova 3107, Casilla 19001, Santiago, Chile a 3 LeidenObservatory,Leiden University,Niels Bohrweg 2, 2333 CA Leiden, The Netherlands J 4 InstitutoNacional de Astrof´ısica, O´ptica y Electro´nica, LuisE. Erro 1, 72840 Tonantzintla, Puebla, M´exico 5 Department of Astronomy, Universityof Massachusetts, Amherst, MA 01003, USA 4 6 Jet Propulsion Laboratory, MS 183-900, California Instituteof Technology, Pasadena, CA 91109, USA 7 Jodrell Bank Centre forAstrophysics, School of Physics and Astronomy, Universityof Manchester, ManchesterM13 9PL, UK ] A G . h AcceptedXXX.ReceivedYYY;inoriginalformZZZ p - o ABSTRACT r t Extremelyhighvelocityemissionlikelyrelatedtojetsisknowntooccurinsomeproto- s Planetary Nebulae. However, the molecular complexity of this kinematic component a [ islargelyunknown.Weobservedtheknownextremeoutflowfromtheproto-Planetary NebulaIRAS16342-3814,aprototypewaterfountain,inthefullfrequencyrangefrom 1 73to 111GHz with the RSRreceiveronthe LargeMillimetre Telescope.We detected v themoleculesSiO,HCN,SO,and13CO.Allmoleculartransitions,withthe exception 9 ofthelatteraredetectedforthefirsttimeinthissource,andallpresentemissionwith 7 velocities up to a few hundred km s−1. IRAS 16342-3814is therefore the only source 1 ofthis kind presentingextreme outflow activity simultaneouslyin all these molecules, 1 0 with SO and SiO emission showing the highest velocities found of these species in . proto-Planetary Nebulae. To be confirmed is a tentative weak SO component with a 701 F10W5.7HcMm−∼3)7,0w0itkhmasm−1a.ssTlhaergeexrttrheamne∼ou0t.fl0o2w–0.g1a5sMco⊙n.sTisthseorfeldaetnivseelygahsig(hnHab2u>nd1a0n4c.8e–s of SiO and SO may be an indication of an oxygen-richextreme high velocity gas. 1 : v Key words: stars: late-type – ISM: molecules – ISM: abundances i X r a 1 INTRODUCTION jets,activeduringtheproto-planetarynebula(pPN)and/or verylate AGBphase,areresponsible forthedrasticchange One of the mysteries in planetary nebulae (PNe) is the in the mass-loss geometry and dynamics of the system in morphological changesthattransform thesphericalcircum- transition (Sahai& Trauger1998).Amongtheoutflowsob- stellar envelopes(CSEs) of asymptoticgiant branch(AGB) servedinpPNe,thereisacategory thatstandsoutbecause starsintohighlybipolar/multipolarPNe.Tounderstandthe of its peculiar kinematics. Sahai & Patel (2015) coined the mechanisms of such changes, the short transition phase in term“Extreme-outflow”to define those pPNe with molecu- betweenshouldbeexplored.Atsomepointinthelate-AGB laroutflowsshowinglineemissioninexcessof∼100kms−1, stage,aprocess(orprocesses)acceleratesandimposesbipo- with a few examples identified by these authors and a few larity upon theslow, spherical AGB winds. What produces others found in the literature fulfilling this definition. Such bipolarityintheseobjectsandatwhatstagedoesbipolarity spectral feature in pPNe outflows may be the equivalent of manifestitselfarekeyquestionsthatremaintobeanswered. the so-called extremely high velocity (EHV) emission ob- Ithasbeensuggestedthatfast collimated outflowsand served in protostellar outflows, which is thought to be an unambiguous jet signature (Bachiller 1996). Indeed, some studies in pPNe outflows support this similarity (see, e.g., ⋆ e-mail:[email protected] (cid:13)c 2016TheAuthors 2 A.I. G´omez-Ruiz et al. Balick et al. 2013). Star formation outflows presenting this peculiar spectral feature have been used as the perfect tool to study the kinematics of the different components of the outflowprocess, butinparticular allowing amorecomplete studyofthejet (EHV)component,otherwisecontaminated by the other outflow components, such as the cavity and the bow shocks (see, e.g., Lefloch et al. 2015). The identifi- cation of extreme-outflows from pPNeis therefore relevant, sincetheirstudyhavethepotentialtoputconstrainstothe- oretical models that includejets. Water fountain pPNe are a particularly interesting subclass of pPNe whose original distinguishing character- istic is the presence of very high-velocity red and blue- shifted H2O and OH maser features. The velocity separa- tions of the water fountains can be as high as 500km s−1 Figure1.LMT/RSRobservationsofthepPNIRAS16342-3814. WepresentthefullbandwidthcoveredbyRSR.Thespeciesiden- (G´omez et al.2011).Thisvelocityspreadofthemasersmay tifiedareSiO,HCN,SO,and13CO. suggestarelationbetweenwaterfountainsandtheextreme- outflows traced by thermal molecular lines (Yunget al. 2016). IRAS16342-3814 is the nearest (∼2 kpc; Sahai et al. resolution, which correspond to ∼ 100 km s−1 at 90 GHz 1999) and best studied water-fountain. Its morphology has (Erickson et al. 2007). In its early science phase, the LMT beenresolvedintheoptical,near-infrared,andmid-infrared. operates with a 32m active surface, which then results in a Radio observations show water masers spread over a wide Half-Power Beam Width (HPBW) ∼ 26′′ at the centre of rangeofradialvelocities(>100kms−1)(Chong et al.2015). the band (RSR data has been reported in a number of pa- CO (2-1)andCO(3-2) observationsrevealamassive,high- pers, for an example see Cybulskiet al. 2016). Autocorre- velocity molecular outflow (Heet al. 2008;Imai et al. 2009, lations,spectraco-adding,calibration,andbaselineremoval 2012). The CO line profiles exhibit both, a narrow com- wasmadewiththeDREAMPY(DataREductionandAnal- ponent with an expansion velocity of 40km s−1, and wide ysisMethodsinPYTHON)software.Acarefulinspectionof wings with an expansion velocity of 100kms−1 (Imai et al. eachscanshowsreasonableflatbaselinesandthereforeonly 2012). alinearfitinDREAMPYwasusedtoremovethebaselineto ThemolecularcomplexityofpPNewithoutflowsiswell each5min spectrum.However,theaverage90min spectrum known(e.g.SanchezContreras et al.1997),howeverinmost showedasubtlelow-frequencycontinuouswavesignalalong of the cases the molecular emission can not be unambigu- thefullRSRband.Indeep(σ<1mK)RSRspectra,theat- ouslyrelated tothejet component.Waterfountains,onthe mospherefluctuationshaveanon-negligible contributionto otherhand,havebeen poorly covered bymolecular line ob- thebaseline,whichisreflectedintoastructurednoisespan- servations.TheEHVemissionfrompPNeoutflowshasbeen ningacross eachboard.Wethenconstructedatemplatefor little explored in other molecular species than CO. Recent thisstructuredsignalusingathirdorderSavitsky-Golayfil- studies in star formation outflows with EHV emission have terwithawindowsizeof1GHz,whichissignificantlygreater unveiled a velocity-dependent shock chemistry and a pecu- than the width of the lines in our spectrum (see sect. 3). liar composition of theEHVgas (Tafalla et al. 2010). With Our approach is slightly different from the technique used this background, we started a project to study the molecu- inCybulskiet al.(2016),sincewecalculateandsubtractthe larcompositionofpPNeoutflowswithknownEHVemission templateforeachindividualspectrumratherthanapplying from CO lines. Inthis letterwe present wide bandobserva- thefilterfor thefinalspectrum only.Atmosphericresiduals tions towards the pPN IRAS16342-3814, with the double can be very different from scan to scan, therefore our final aim of providing a molecular census in this prototype wa- averagespectrumislessaffectedbyartifactsignalsproduced ter fountain and to study the molecular composition of the bysubtractioneffectsthatmaybeproducedifonlythefinal EHV gas. spectrumispassedthroughthefilter.Thefilteredspectrum has an average r.m.s noise of 0.29 mK. Note, however, that thenoiseisnotuniformalongtheband,andsomepartsare 2 OBSERVATIONS less noisy. To convert antenna temperature units (T∗A) to Jy, we used a conversion factor (Jy/K) of 6.4 for ν < 92 Using the Large Millimetre Telescope Alfonso Serrano in GHz and 7.6 for ν > 92 GHz. Finally, for consistency, the its early science phase, we observed the known EHV out- line parameters were obtained from a spectrum re-sampled flow pPN IRAS16342-3814 with the Redshift Search Re- totheworsespectralresolution correspondingtothelowest ceiver (RSR). Observations were performed on March 19th frequencytransition detected (SiO 2–1; i.e. 108km s−1). and 24th, 2016, with a sky opacity, τ225GHz, ranging from 0.16 to 0.20, and an instrumental Tsys from 109 to 116 K. Observations were centred on the coordinates RA (J2000) 3 RESULTS = 16:37:39.91, DEC (J2000) = -38:20:17.3; with the OFF beam 39′′ apart. Pointing accuracy was found to be better In Figure 1 we present the 3 millimetre spectrum of IRAS than 2′′. Thetotal ON time integration was 1.5 hrs. 16342-3814. The frequency displayed is topocentric; how- The RSR is an autocorrelator spectrometer that cov- ever, the difference with respect to the rest frame is much ers thefrequency rangeof 73–111 GHz, at 31 MHzspectral smaller than a channel width, and therefore equal to rest MNRAS000,1–6(2016) Molecules in the Extreme Outflow of a pPN 3 frequency within theuncertainties. Table 1 summarizes the molecular lines detected and their parameters. The follow- ingfivemoleculartransitionsweredetected:SiO(2–1),HCN (1–0),SO(32–21)andSO(23–12),and13CO(1–0). Allbut 13CO are first detections in this source. All these lines can be fitted by Gaussian profiles centred close to the systemic velocity (within the uncertainties). Figure 2 shows the SiO (2–1), HCN (1–0), and the 13CO (1–0) lines with their re- spective Gaussian fits. In the case of SO (32–21), a two- component Gaussian fit seems to be needed to account for theemission(seebelow).Inpeakintensity,thestrongestline is 13CO (1–0), while the weakest is SO (23–12). SiO (2–1) and HCN (1–0) are approximately similar in peak inten- sity.Regardingthelinewidth,SiO(2–1)isabout40%wider (Full Width Half Maximum (FWHM) of 322±47 km s−1) than HCN (1–0), while the narrowest lines are SO (23–12) and 13CO (1–0) with FWHMbetween 108–120 km s−1. In Fig. 3 we show Gaussian fits to the SO (32–21) and SO (23–12) profiles. In a first attempt, we tried to fit a sin- gleGaussiancomponenttotheSO(32–21)lineprofile(black line in the upper panel of Fig. 3). The resulting FWHM is 241±42 km s−1. However, we notice a substantial residual coming from the blue-shifted part of the spectrum. Such a Figure 2. Line profiles of the molecules SiO (2–1), HCN (1–0), residualmaysuggestthepresenceofaveryfastblue-shifted and13CO(1–0),theyhaveallbeenfittedwithaonecomponent wing, with a maximum radial velocity (above a 3σ level) of Gaussian. Velocity axis is with respect to LSR and the spectral ∼−700kms−1.Atwo-componentGaussian fitreducesthe resolution 108 km s−1. Using the Gaussian fits we measure the line width, SiO and HCN have a FWHM > 200 km s−1, while residual byafactor of 3 (redline in theupperpanelofFig. the13COlinehasaFWHMof120kms−1. 3),resultinginanarrowcomponentatthesystemicvelocity with a FWHM of 139±74 km s−1 and a wide component with a FWHM of 748±157 km s−1 shifted to negative ve- 4 DISCUSSION locities (peakvelocity−315±100 kms−1).Inthesearch for 4.1 Molecular composition and physical other contaminants that may broaden the SO (32–21) line, properties we checked for line transitions inside the range of frequen- ciesthatfallintothesamerangeofthelineemission(defined Before our observations, molecular line data of IRAS within a 3σ level). The HCCNC (J=10–9) line lies at 99.40 16342−3814 revealed the presence of a fast bipolar outflow GHz, however this molecule is more common in C-rich ob- and a slowly expanding torus/CSE (Imaiet al. 2012). The jects and IRAS16342−3814, on the otherhand,is a O-rich COoutflowhaveaFWHM∼150kms−1 (Imai et al.2009), object (as proven by the simultaneous detection of SO and whiletheH2Omasersshowatotalvelocityspreadof270km SiO), suggesting such an identification to be unlikely. Fur- s−1,withtheirpropermotionsindicatingthree-dimensional thermore,thefrequencyoftheHCCNClinefallsatthehigh- velocities of approximately ± 180 km s−1 (Claussen et al. frequencyedgeofthebroadcomponent.Theimplicationsof 2009).OurobservationsshowtheHCN(1–0) emission with thewidecomponentisimportant,sincethiswouldrepresent aFWHMsimilar tothevelocity spread of theH2O masers, thehighest velocity everobserved in a molecular outflow of while the SO emission shows slightly lower values. On the a pPN. Although the careful reduction we have performed other hand, the SiO emission seems to present higher ve- gives confidence that such a feature is real, given its weak- locities than the water masers. The 13 CO (1–0) FWHM is ness we prefer to be cautious and defer the confirmation of similar the12CO measurements. thisfeaturetofuturedeeperobservations(unfortunatelyno OH 231.8+4.2 is theother pPNeshowing high-velocity further observations on this object could be taken during SOemissionwithalinewidth∼100kms−1 (withanotably the early science season). The SO (23–12) line is detected asymmetric profile: Claude et al. 2000). Therefore, our de- at ∼4σ in onlyonechannel(note,however,afeatureat ∼ tection is thehighest velocity SO emission found in a pPN. +400kms−1thatweignorebecauseitbarelyreaches∼3σ, HCN has been detected at extreme velocities only in CRL and is located in the noisiest part of the band), hence only 618, with a totalvelocity range similar tooursource (∼250 oneGaussiancomponentisrequiredtofittheemission.This km s−1 S´anchezContreras & Sahai 2004). The SiO emis- component has a FWHM of 108±61 km s−1 and is centred sion,ontheotherhand,hasbeenpreviouslydetectedatex- at thesystemic velocity. tremevelocities of ≤150kms−1 onlyin IRAS08005−2356 MNRAS000,1–6(2016) 4 A.I. G´omez-Ruiz et al. Table 1.Molecular linesdetected inIRAS 16342−3814 withthe LMT/RSR and their parametersa Transition Frequency(GHz) HPBW(′′) Eu (K) LinePeak(mJy) Vpeak (kms−1) FWHM(kms−1) RSdv(mJykms−1) SiO(2–1) 86.847 27.1 6.2 10.4 −5(8) 332(47) 3677(427) HCN(1–0) 88.623 26.6 12.8 10.3 −7(18) 276(58) 3023(460) SO(32–21) 99.296 23.8 9.2 15.6 +3(12) 239(39) 3988(453) SO(23–12) 109.252 21.6 21.1 10.3 +17(11) 108(61) 1217(395) 13CO(1–0) 110.201 21.4 5.3 66.8 +2(7) 120(20) 8572(359) a:LineparametersfromGaussianfits;errorsindicatedinbrackets. applied beam filling corrections to the line brightness tem- peratures, assuming a Gaussian source with a size of 0.5′′× 2′′ (e.g., Imai et al. 2012). We found a Trot in the range of 5-11 K, and N(SO) in the range of 7.0×1016 to 4.1×1018 cm−2. For the other species we also assumed LTE, an ex- citation temperature of 11 K (i.e. maximum Trot we found forthenarrowSOcomponent),andthesamesourcesizefor beamfillingcorrections.TheresultsarereportedinTable2. Using the SO lines ratio, we constrained the physi- cal conditions of the extreme high velocity gas. We have employed the offline version of RADEX (van derTak et al. 2007)togenerateagridoflinesratios,kinetictemperatures, andH2volumedensities.Amorecompletedescriptionofthe RADEXcalculationsisprovidedinAppendixA.Weassume 2.73 K as the background temperature and a line width of 170 km s−1 (average FWHM of the two SO lines). We find thattheSOlineratioisnotverysensitivetocolumndensity within 1011 cm−2 to ∼ 1018 cm−2. We point out that with onlyonelineratioit isonlypossible toprovidelowerlimits Figure3.SpectraoftheSOlinesdetectedtowardthepPNIRAS tothekinetictemperatureandvolumedensity.Theobserved 16342-3814andGaussianfitstotheirprofiles(redline).Velocity SO intensity ratio (from Table 1: 3988±453/1217±395 = axis is with respect to LSR and the spectral resolution 108 km s−1. The upper panel shows two different fits, ablack one using 3.3±1.1) constrains a lower limit to the H2 volume density, only one Gaussian fit, and a red fit using two Gaussian compo- nH2 > 104.8–105.7 cm−3, and kinetic temperature, Tkin > nents.The2fitscomponentshowsacomponentintheSO(32–21) 15–55 K. line with a FWHM of > 600km s−1, centred at negative veloc- ities, suggesting an extremely fast blue-shifted outflow. For the The H2 mass of the SO extreme outflow is determined lowerpanelweonlyfittedanarrowcomponenttotheSO(23–12) byusingthenH2lowerlimitestimatedwiththeLVGanalysis linewithaFWHMof∼108kms−1. from RADEX.Imai et al.(2012)modelledtheCOemission anddeterminedthattheCSE/jethaveasizeintherangeof 6,000–10,000 AU. Assuming that the emission comes from (albeit in theweak SiO (5–4) and SiO (6–5): Sahai& Patel aspheroid with dimensions6,000 AU×6,000 AU×10,000 2015).HencetoourknowledgetheSiOemissionwefoundin AU,whichhasauniformnH2 of104.8–105.7cm−3(bestvalue IRAS16342−3814isthehighestvelocityreporteduntilnow of 105.3 cm−3), the mass of such structure should be larger in pPNe. It is important to point out that previous stud- than ∼ 0.02–0.15 M⊙ (0.06 M⊙ for the best value). This ies show the SiO emission tracing the expanding CSE (see mass estimate agrees very well with themass calculated by deVicenteet al. 2016, for a recent study of the SiO emis- Zijlstra et al. (2001, see table 4.), where the dust model of sion in evolved stars). Our data shows SiO emission with the inner most region gives them a density of 108 cm−3, a highervelocities,byafactorofthree,whichmustbetracing dust temperature of 80-200 K and a mass of 0.1 M⊙. This adifferentkinematiccomponent,possiblyrelatedtothejet, lower limit to the mass is higher by up to a factor of five given the similarity with the velocity spread of the water thanthecalculationsforafast outflowasseenfromtheCO masers. To ourknowledge, only IRAS16342−3814 presents emission(see,e.g.,Sahai et al.2006).Suchadense,veryfast EHV emission simultaneously in SiO,SO,HCN and 13CO. andmassivematerialmayberelatedtoajetcomponent.We We assumed LTE conditions in order to calculate the point out, however, that theSO emission may come from a column densities (N) of themolecular species found. In the smaller (shocked) region than theone traced by CO, which case of SO, with the two transitions detected,we were able thenwouldincreasethenH2 estimation.Interferometricmm- to provide an estimation of the rotational temperature and wavelength observations with angular resolution below 1′′ columndensity,byemployingarotationaldiagram analysis are needed to probe the structure of the SO EHV emission (following Claude et al. 2000). In our calculations we have in greater detail. MNRAS000,1–6(2016) Molecules in the Extreme Outflow of a pPN 5 specttoOH231.8+4.2,thereisstillthesimilaritythatboth Table 2.Molecular abundances and column densities pPNe present a very fast outflow. It has been suggested Molecule N(cm−2) Xa that the shocks from the extreme-outflow of OH 231.8+4.2 may have a major impact on the rich chemistry observed SiO 1.4E17 5.2E-7 in that source. Velilla Prieto et al. (2015),for example, dis- HCN 2.7E16 9.6E-8 cuss the posibility of molecular reformation after the high- SO 7.0E16 4.0E-7 speed shocks, from the interaction of the jet and the CSE, 13CO 5.6E18 2.0E-5b destroythemolecules.Theypropose,inparticular,thatad- ditional atoms (such as Si and S) may be released to the a:X=X(13CO)×N/N(13CO).b:Bujarrabaletal.2001. gasphasefrom thedustgrainsbytheactionsoftheshocks, andwhentheshockedmaterial hascooled downsufficiently to allow molecular reformation, there is a different propor- tion of the elements available for the reactions in the post- Inordertotesttheeffectofmagneticfields,weprovide shockedgas,affectingtheabundancesofasecond-generation a rough estimate of the field intensity needed to broaden ofmolecules.Suchprocessmayalsobeapplicabletothecase the SO line to a few hundredkm s−1, assuming exclusively ofIRAS16342−3814.Inthatregard,wenoticethattheSiO theZeeman effect.Usingtheformulas given inBel & Leroy abundance is close to the range predicted by shock chem- (1989), we calculated that the minimum field detectable is istry models (SiO production in the gas phase through the of the order of mG. For a broadening of ∼60-90 MHz the sputtering of Si-bearing material in refractory grain cores: magnetic fieldintensityneeded is∼70G. Vlemmings (2014) Gusdorf et al. 2008), which may give support to such sce- estimated ∼100G for the upper limit for the magnetic field nario. However, we point out that the caveat here is that near the stellar surface for AGB stars, so our estimations the abundance calculations are dependent on the assumed areconsistentwiththislimit.However,theresolutionofthe value of the excitation temperature (that can be different RSRpreventsus from saying anythingmore conclusive. for different molecules), hence a better estimation of such quantity is required before drawing any general conclusion. Also, the limitation of our spectral line data is that it is 4.2 Molecular abundances in the EHV gas difficult to separate the contribution from the low-velocity In Table 2 we report the molecular abundances (X) com- (circumstellarenvelope)andhigh-velocity(jet)components. puted by using the column density estimations and the ex- Hencetheabundancesreportedherearetheaverageofboth pression X=X(13CO)×N/N(13CO), where X(13CO) is as- components, which may not be sufficent for detailed future sumed to be 2×10−5 (following Bujarrabal et al. 2001). We shock chemistry models. noticethattheSOabundance(4.0×10−7)isconsistentwith results of the SO wings in OH 231.8+4.2 Claude et al. (2000). The abundance of SiO (5.2×10−7) is lower by 5 CONCLUSIONS two orders of magnitude than in IRAS 08005−2356, the other known SiO extreme-outflow (Sahai & Patel 2015). (i) Our modest 1.5 hr LMT observations with the RSR The HCN abundance (9.6×10−8) is more similar to the probedtobeagoodstrategytotestthechemicalcontentof lower limit calculated in CRL 618 for the low-velocity extremevelocity outflows from pPNe. HCN emission (>2×10−7) than for high-velocity (4×10−6) (ii) Withalinewidthof∼240kms−1,wefoundthehigh- (S´anchezContreras & Sahai 2004). est velocity SO outflowin a pPN. The SiO/HCN abundanceratio is ∼ 5, suggesting that (iii) The HCN emission has a velocity spread similar to C-bearingmoleculesaredepletedintheextreme-outflow.In CRL618, the otherpPN known with high-velocityHCN. contrast, the other O-rich pPN with an extreme-outflow, (iv) WefoundthehighestvelocitySiOemissioninapPN, OH 231.8+4.2, such abundance ratio is ∼ 0.5 for the which may trace a different kinematic component with re- EHV range (average of ∼ 0.3 for the whole line emission specttopreviousSiOobservationsinevolvedstars,possibly range: SanchezContreras et al. 1997). On the other hand, related toa jet. the SiO/SO abundance ratio is close to one, which there- (v) By using a SO line ratio, we found that the extreme fore implicates that the elemental abundances of Si and outflowconsist ofdensegas(nH2 >104.8–105.7 cm−3),with S are similar; in sharp contrast with OH 231.8+4.2 for a mass of ∼ 0.02–0.15 M⊙. which such ratio is∼ 10−2 (SanchezContreras et al. 1997; (vi) We found a weak indication of very fast SO (32–21) Claude et al. 2000). A remarkable result is that thehighest emission reaching velocities ∼ −700 km s−1, that if con- abundances are those of SiO and SO, which suggests that firmedwouldbethefastest molecular outfloweverfoundin the extreme high velocity gas is dominated by O-bearing a proto-Planetary Nebula. molecules. It is well known that theextreme-outflowin OH 231.8+4.2 is more prominent in HCN than in SiO (e.g., SanchezContreras et al.1997),whichmayindicatethatthis 6 ACKNOWLEDGEMENTS kinematic component, contrary to IRAS 16342−3814, is more C-rich than O-rich. In that respect, it is relevant to This work would not have been possible without the long- notice that an O-rich EHV gas in the pPN presented here term financialsupport from theMexican Scienceand Tech- is more similar to what is found in the star-formation case nologyFundingAgency,ConsejoNacionaldeCienciayTec- (Tafalla et al. 2010). nolog´ıa (CONACYT), during the construction and early Despitetheabundancetrenddifferencesnoted with re- science phase of the Large Millimetre Telescope Alfonso MNRAS000,1–6(2016) 6 A.I. G´omez-Ruiz et al. Serrano, as well as support from the the US National Science Foundation via the University Radio Observatory program, the Instituto Nacional de Astrof´ısica, O´ptica y Electronica (INAOE), and the University of Massachusetts (UMASS).AGRisfundedbytheprogramC´atedrasCONA- CYT para Jovenes Investigadores. LGR is co-funded under theMarieCurieActionsoftheEuropeanCommission(FP7- COFUND). REFERENCES BachillerR.,1996, ARA&A,34,111 BalickB.,Huarte-EspinosaM.,Frank A.,Gomez T.,AlcoleaJ., CorradiR.L.M.,Vinkovi´cD.,2013,ApJ,772,20 BelN.,LeroyB.,1989, A&A,224,206 BujarrabalV., Castro-CarrizoA., AlcoleaJ., S´anchez Contreras C.,2001,A&A,377,868 ChongS.-N.,ImaiH.,DiamondP.J.,2015,ApJ,805,53 Claude S. M. X., Avery L. W., Matthews H. E., 2000, ApJ, 545,379 ClaussenM.J.,SahaiR.,MorrisM.R.,2009,ApJ,691,219 CybulskiR.,etal.,2016,MNRAS, Erickson N., Narayanan G., Goeller R., Grosslein R., 2007, in Baker A. J., Glenn J., Harris A. I., Mangum J. G., Yun Figure A1. Results from the LVG analysis of the SO lines de- M. S., eds, Astronomical Society of the Pacific Conference tected.ThecurvesrepresentthepredictedSO(32–21)toSO(23– SeriesVol.375,FromZ-MachinestoALMA:(Sub)Millimeter 12)intensityratioforacolumndensityof5×1014 cm−2.Thera- Spectroscopy ofGalaxies.p.71 tiosthatmatchtheobservedSOlineratioanditserrors(3.3±1.1) G´omez J. F., Rizzo J. R., Su´arez O., Miranda L. F., Guerrero areindicatedbythesolidanddashedredcurves,respectively. M.A.,Ramos-LariosG.,2011,ApJ,739,L14 GusdorfA.,CabritS.,FlowerD.R.,PineauDesForˆetsG.,2008, A&A,482,809 APPENDIX A: RADEX DIAGNOSTIC PLOT He J. H., Imai H., Hasegawa T. I., Campbell S. W., Nakashima We used the offline version of RADEX (van derTak et al. J.,2008,A&A,488,L21 ImaiH.,HeJ.-H.,NakashimaNobuharuJ.-I.U.,DeguchiS.,Kon- 2007)togenerateadiagnosticplot oftheSO(32–21)toSO ingN.,2009,PASJ,61,1365 (23–12)intensityratio,asafunctionofkinetictemperatures ImaiH.,ChongS.N.,HeJ.-H.,NakashimaJ.-i.,HsiaC.-H.,Sakai andH2volumedensities.Adiscussionontheuseofthesedi- T.,DeguchiS.,KoningN.,2012,PASJ,64 agnosticplotsarepresentedfordifferentmoleculesintheap- LeflochB.,etal.,2015,A&A,581,A4 pendix of van der Tak et al. (2007). Linear molecules, such SahaiR.,PatelN.A.,2015,ApJ,810,L8 as SO, are density probes at low densities, while at higher SahaiR.,TraugerJ.T.,1998,AJ,116,1357 densities the line ratios are more sensitive to temperature. Sahai R., te Lintel Hekkert P., MorrisM.,ZijlstraA., Likkel L., However, with no other information than a single line ratio 1999,ApJ,514,L115 (suchasourcase),itisonlypossibletoprovidelowerlimits Sahai R., Young K., Patel N. A., S´anchez Contreras C., Morris todensity and temperature. M.,2006,ApJ,653,1241 S´anchezContrerasC.,SahaiR.,2004, ApJ,602,960 In Fig. A1weshow thediagnostic plot for theSO(32– Sanchez Contreras C., Bujarrabal V., Alcolea J., 1997, A&A, 21) to SO (23–12) intensity ratio, assuming 2.73 K as the 327,689 background temperature and a line width of 170 km s−1 Tafalla M., Santiago-Garc´ıa J., Hacar A., Bachiller R., 2010, (average FWHM of the two SO lines). The plot shows the A&A,522,A91 results for a column density of 5×1014 cm−2, however we VelillaPrietoL.,etal.,2015,A&A,575,A84 find that the SO line ratio is not very sensitive to column Vlemmings W. H. T., 2014, in Petit P., Jardine M., density within the range 1011 cm−2 to ∼ 1018 cm−2. The Spruit H. C., eds, IAU Symposium Vol. 302, Mag- ratios obtained from this run varies from 1.77 to 145.57. netic Fields throughout Stellar Evolution. pp 389–397, TheSOintensityratio thatmatch theobserved ratio (from doi:10.1017/S1743921314002580 Table1:3988±453/1217±395 =3.3±1.1)constrainsalower Yung B. H. K., Nakashima J.-i., Hsia C.-H., Imai H., 2016, preprint, (arXiv:1611.03306) limittotheH2volumedensity,nH2 >104.8–105.7 cm−3,and Zijlstra A. A., Chapman J. M., te Lintel Hekkert P., Likkel L., kinetictemperature, Tkin > 15–55 K. Comeron F., Norris R. P., Molster F. J., Cohen R. J., 2001, MNRAS,322,280 Thispaper has been typeset fromaTEX/LATEX fileprepared by deVicenteP.,etal.,2016,A&A,589,A74 theauthor. vanderTakF.F.S.,BlackJ.H.,Sch¨oierF.L.,JansenD.J.,van DishoeckE.F.,2007,A&A,468,627 MNRAS000,1–6(2016)