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A&A604,A32(2017) Astronomy DOI:10.1051/0004-6361/201730466 & (cid:13)c ESO2017 Astrophysics The complexity of Orion: an ALMA view I. Data and first results(cid:63),(cid:63)(cid:63) L.Pagani1,C.Favre2,3,P.F.Goldsmith4,E.A.Bergin5,R.Snell6,andG.Melnick7 1 LERMA&UMR8112duCNRS,ObservatoiredeParis,PSLResearchUniversity,CNRS,SorbonneUniversités, UPMCUniv.Paris06,75014Paris,France e-mail:[email protected] 2 Univ.GrenobleAlpes,CNRS,IPAG,38000Grenoble,France 3 INAF–OsservatorioAstrofisicodiArcetri,LargoE.Fermi5,50125Florence,Italy e-mail:[email protected] 4 JPL,Pasadena,California,USA e-mail:[email protected] 5 DepartmentofAstronomy,UniversityofMichigan,311WestHall,1085S.UniversityAve,AnnArbor,MI48109,USA 6 DepartmentofAstronomy,UniversityofMassachusetts,Amherst,MA01003,USA 7 Harvard-SmithsonianCenterforAstrophysics,Cambridge,Massachusetts,USA Received19January2017/Accepted22May2017 ABSTRACT Context.WewishtoimproveourunderstandingoftheOrioncentralstarformationregion(Orion-KL)anddisentangleitscomplexity. Aims.WecollecteddatawithALMAduringcycle2in16GHzoftotalbandwidthspreadbetween215.1and252.0GHzwithatypical sensitivityof5mJy/beam(2.3mJy/beamfrom233.4to234.4GHz)andatypicalbeamsizeof1(cid:48).(cid:48)7×1(cid:48).(cid:48)0(averagepositionangleof 89◦).Weproducedacontinuummapandstudiedtheemissionlinesinnineremarkableinfraredspotsintheregionincludingthehot coreandthecompactridge,plustherecentlydiscoveredethyleneglycolpeak. Methods. We present the data, and report the detection of several species not previously seen in Orion, including n- and i-propyl cyanide (C H CN), and the tentative detection of a number of other species including glycolaldehyde (CH (OH)CHO). The first 3 7 2 detectionsofgGg(cid:48) ethyleneglycol(gGg(cid:48) (CH OH) )andofaceticacid(CH COOH)inOrionarepresentedinacompanionpaper. 2 2 3 Wealsoreportthepossibledetectionofseveralvibrationallyexcitedstatesofcyanoacetylene(HC N),andofits13Cisotopologues. 3 Wewerenotabletodetectthe16O18OlinepredictedbyourdetectionofO withHerschel,duetoblendingwithanearbylineof 2 vibrationally excited ethyl cyanide. We do not confirm the tentative detection of hexatriynyl (C H) and cyanohexatriyne (HC N) 6 7 reportedpreviously,orofhydrogenperoxide(H O )emission. 2 2 Results. Wereportacomplexvelocitystructureonlypartiallyrevealedbefore.Componentsasextremeas−7and+19kms−1 are detected inside the hot region. Thanks to different opacities of various velocity components, in some cases we can position these componentsalongthelineofsight.Weproposethatthesystematicallyredshiftedandblueshiftedwingsofseveralspeciesobserved inthenorthernpartoftheregionarelinkedtotheexplosionthatoccurred∼500yrago.Thecompactridge,noticeablyfarthersouth displaysextremelynarrowlines(∼1kms−1)revealingaquiescentregionthathasnotbeenaffectedbythisexplosion.Thisprobably indicatesthatthecompactridgeiseitherover10000auinfrontoforbehindtherestoftheregion. Conclusions. Many lines remain unidentified, and only a detailed modeling of all known species, including vibrational states of isotopologuescombinedwiththedetailedspatialanalysisofferedbyALMAenrichedwithzero-spacingdata,willallownewspecies tobedetected. Key words. ISM: clouds – ISM: structure – ISM: individual objects: Orion-KL (except planetary nebulae) – astrochemistry – molecularprocesses 1. Introduction Kleinmann-Low Nebula (KL), often referred to as Orion- KL (but also numerous other names, as listed in SIM- The Orion region hosts two well-studied star forming sites, BAD1). The Orion-KL nebula is the nearest massive star Orion A and Orion B. Orion A is subdivided into four clouds forming region (distance equal to 388pc±5pc, Kounkeletal. (Orion Molecular Cloud 1–4, OMC) and OMC1 holds the 2017, in replacement of the previous value of 414pc±7pc, (cid:63) This paper makes use of the following ALMA data: Sandstrometal. 2007; Mentenetal. 2007) and as such has at- ADS/JAO.ALMA#2013.1.00533.S. ALMA is a partnership of tracted considerable attention and is the subject of thousands ESO(representingitsmemberstates),NSF(USA)andNINS(Japan), of publications. The core is complex with several remarkable together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI sources,thehotcore(HC),thecompactridge(CR),theextended (Republic of Korea), in cooperation with the Republic of Chile. The ridge (ER), the plateau, numerous methyl formate (MF) peaks JointALMAObservatoryisoperatedbyESO,AUI/NRAOandNAOJ. (Favreetal. 2011a), and other infrared/submillimeter peaks (cid:63)(cid:63) ThereducedALMAdatacubesaslistedinTable1areavailableat theCDSviaanonymousftpto cdsarc.u-strasbg.fr( 1 http://simbad.u-strasbg.fr/simbad/sim-id?Ident= http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/604/A32 Orion-KL ArticlepublishedbyEDPSciences A32,page1of87 A&A604,A32(2017) listed in many papers (e.g. Riekeetal. 1973; Robbertoetal. weonlydiscussthedatafromthefirstpointing(theOrion-KLre- 2005;Friedel&Weaver2011),includingthreerunawayobjects: gion). The resolution was set to 488 kHz to get ∼0.6 kms−1 BN, I, and n (Gómezetal. 2005; Rodríguezetal. 2005, 2017). resolution to spectrally resolve the expected 16O18O linewidth Among the studies aimed at identifying molecules in Orion, of 1.5–2 kms−1 (see Sect. 3.7.1). The resolution selection which is the reference source along with SgrB2 in which to gives a bandwidth of 0.937 GHz per window. For each point- searchfornewspecies,manysurveyshavebeenconductedwith ing, we split the observations into five observing blocks with single-dish telescopes from the ground (from some of the ear- different frequency setups, resulting in 16 different frequency liest works by Suttonetal. 1985; Blakeetal. 1986, to recent bands(fourwindowspersetup,onewindowalwayscenteredon observations with the IRAM-30 m, Terceroetal. 2010, 2011; 16O18O at 234 GHz, the other three moved around), covering Cernicharoetal.2016;etc.andwithHerschelinadedicated1.2 approximately 16 GHz of total bandwidth between 215.15 and THzbandwidthsurvey,Berginetal.2010;Crockettetal.2014). 252.04 GHz. The details of the frequency coverage are given With the sensitivity progress of the spectroradiometers, these in Table 1. Compared to the Cycle 0 Science Verification sur- surveyshavereachedtheconfusionlimit;almostalltherecorded vey of Orion (SV0), we cover half of the SV0 frequency in- channels contain emission of some species, implying strong terval, but have coverage beyond the SV0 survey between 250 blendinganddifficultydeterminingthebaselinelevel.Thecon- and 252 GHz, with the same frequency resolution, a slightly fusion limit is partly due to the impossibility for single-dish smaller beam (on average 1(cid:48).(cid:48)7 × 1(cid:48).(cid:48)0 compared to 2(cid:48)(cid:48) × 1(cid:48).(cid:48)5, telescopes to spatially separate the contribution of the different Terceroetal. 2015) and a much better sensitivity (SV0 sensi- sources in Orion that occur at different velocities, therefore in- tivityisintherange10–30mJybeam−1,Hirotaetal.2012,com- creasing the overlap between lines. Naturally, interferometers pared to 2–8mJybeam−1 in the present study). The data were have been used to separate the components, diminish the con- re-calibratedusingtheprovidedpythonscript(scriptforPI.py)in fusion,andhelpunderstandtheongoingevolutionofthechem- the Common Astronomy Software Applications (CASA) pack- ical and physical complex structure (e.g. Favreetal. 2011a; age V.4.2.2 (McMullinetal. 2007). The continuum was esti- Pengetal. 2012, 2017; Brouilletetal. 2013; Fengetal. 2015; mated in the UV tables and subtracted, velocity correction to Terceroetal.2015). LSR scale was performed, and the data (UV tables) were sub- After our detection of O in Orion with Herschel sequentlyexportedandconvertedtoGildasformatforfinalpro- 2 (Goldsmithetal. 2011; Chenetal. 2014), and due to the diffi- cessing (cleaning) using the MAPPING application2. For each culties of the interpretation, we decided to try to pinpoint the source,spectrawereextractedinaCLASS2file,convertedfrom emission region by performing deep observations of the rarer Jy/beamtoK(seeTable1)andcorrectedforprimarybeamcou- 16O18O isotopologue with ALMA at 234 GHz. To increase the pling.Theprimarybeamcouplingrunsfrom99%forthesource interest of these observations, we took advantage of the possi- IRc7to71%forMF10.Allvelocitiesareexpressedinthelocal bility to divide the run into five independent observing blocks standardofrest,(LSR). tomovethebackendwindowsasmuchaspossibletocoverthe maximumbandwidth.Thechoiceofthewindowpositionswasa compromisebetweenthetechnicallimitationsandtheinclusion of species somewhat related to O in their formation process, 2 such as SO and NO, or those useful for diagnostic purposes of 3. Analysis thesourcewhereO wouldhavebeendetectedcomparedtothe 2 othersourcesoftheregioninordertounderstandthereasonfor Because we currently lack the zero-spacing data to recover the alimitedemissionregion. extended emission of many species, we generally have not at- Inthispaper,wepresentthedataresultingfromthissurvey tempted toderive columndensities andexcitation temperatures and the first results we obtain. Further analysis, and in partic- ofthespecieswediscusshere.Thiswillbedoneinafuturework ular the first detection of acetic acid and of the gGg(cid:48) isomer of oncethesedataareobtainedandincludedinthedataprocessing. ethyleneglycolwillbereportedinaseriesofforthcomingpapers However, we tried to fit the emission with the supposition of (Favreetal.2017;Paganietal.,inprep.).Thesearepresentlythe localthermodynamicalequilibrium(LTE),forallspeciesbyad- mostsensitiveinterferometerobservationstowardsOrion-KL. justingtheircolumndensity,excitationtemperature,velocityand The paper is organized as follows. In Sect. 2, we present linewidth (except for methyl cyanide, CH3CN, see Sect. 4.3). the observations and the data reduction. In Sect. 3, we present The fit was adjusted by eye to reasonably fit most of the lines the data analysis (new species or new vibrationally excited of each species; this is considered a definitive determination of transitions, refuted species from previous tentative detections, the line velocity and width, but not of the species column den- non-detected species), and in Sect. 4 we discuss the velocity sityandexcitationtemperature.Thispermitsadeterminationof componentsandpresentourconsiderationsregardingthesource thenumberofvelocitycomponentsnecessarytofittheprofiles. structure.ConclusionsaredevelopedinSect.5. TheLTEfitwasperformedusingLINEDBandWEEDSsetsof routinesinside CLASS(Maretetal. 2011). Theline catalogues aretheCologneDatabaseforMolecularSpectroscopy(CDMS, Mülleretal. 2001, 2005) and the Jet Propulsion Laboratory 2. Observationsanddataprocessing (JPL)catalogue(Pickettetal.1998),withsomecomplementary data provided by A. Belloche from the Bellocheetal. (2013, The observations were performed on 29 December 2014 with hereafter B13) work to identify vibrationally excited states of 37 antennas for the first four scheduling blocks and on 30 De- vinyl and ethyl cyanides which we do not discuss in this paper cember 2014 for the last block with 39 antennas. Two point- but which were needed since a number of these transitions are ing directions were observed, the same as those used in verystrong,upto30K. the Herschel observations (Goldsmithetal. 2011; Chenetal. 2014),namelytheKLregion,RA :05h35m14s.160,Dec : J2000 J2000 −05◦22(cid:48)31(cid:48).(cid:48)504 and the H vibrational peak farther north, 2 RA :05h35m13s.477,Dec :−05◦22(cid:48)08(cid:48).(cid:48)50.Inthispaper, 2 http://www.iram.fr/IRAMFR/GILDAS/ J2000 J2000 A32,page2of87 L.Pagani etal.:ThecomplexityofOrion:anALMAview.I. Table1.Frequencybandsandbeamparameters. Band Window Blocka Frequencyrangeb Beamshape Pos.angle Noisec Conversion Noisec (#) (spw) (sg) (MHz) (MHz) (arcsec) (degree) (mJy/beam) (K/Jy) (mK) 1 3d 1 215149.592 216086.673 1.8×1.1 86 7.0 13.3 93 2 2d 1 216342.044 217279.136 1.8×1.1 84 3.7 13.1 48 3 3 2 217273.522 218210.619 2.2×1.0 102 3.6 11.7 42 4 2 2 218203.531 219140.628 2.2×1.0 102 4.6 11.6 53 5 3d 3 219126.547 220063.614 1.9×1.0 95 4.5 13.3 60 6 2d 3 219783.544 220720.641 1.8×1.0 95 5.1 14.0 71 7 1 1 229756.971 230694.089 1.4×0.8 80 4.0 20.6 82 8 1 2 230698.921 231636.062 2.1×0.9 102 3.9 12.1 47 9 1 5 232238.058 233175.172 1.6×1.0 80 3.5 14.1 49 10 0 1–5 233469.680 234421.910 1.6×0.8 90 2.3 17.5 40 11 1 3 235083.689 236020.787 1.7×0.9 95 5.1 14.4 73 12 1 4 236268.702 237205.799 1.6×0.9 87 3.8 15.2 58 13 3 5 244833.767 245770.865 1.6×0.9 79 4.6 14.1 65 14 2 5 245772.781 246709.895 1.6×0.9 79 4.6 14.0 64 15 2 4 250153.833 251090.932 1.5×0.9 88 8.0 14.4 115 16 3 4 251078.799 252015.916 1.3×0.8 86 8.4 18.6 156 Notes. (a) Observingblock:allfrequencywindowswiththesameobservingblocknumberhavebeenobservedsimultaneously(b) thefrequency rangeisgivenforV =˜ 9kms−1.(c) Noiseisnotcorrectedforprimarybeamcouplingandisthereforealowerlimittotheactualnoiseineach LSR source.Correctionsrunfrom1%(IRc7)to41%(MF10).(d)Alastminutechangeoffrequencyintroducedanerrorinsettingthebandscreatinga holefrom216087MHzto216342MHzandanoverlapfrom219784to220064MHz.ThereducedALMAdatacubesareavailableattheCDS. Fig. 1. Continuum flux image of Orion-KL at ∼1.3mm, from an assemblage of channels free of line emission. The contours are ev- ery 100 mJy/beam (uncorrected for primary beam coupling). The ten sources analyzed in detail in this work are indicated and la- beled (other labels of the same sources can be found in SIMBAD/CDS): HC = hot core, CR = compact ridge, MFxx from Favreetal. (2011a), Cxx from Friedel&Weaver (2011), IRcxx from Riekeetal. (1973), Shupingetal. (2004),mmxxfromFengetal.(2015)andref- erencestherein.Theyellowcrossindicatesthe centerofexplosionfromwhichtheBN,I,and n sources (marked by yellow stars) are mov- ing away (Gómezetal. 2005). The blue cir- clesmarktheprimarybeamcouplingefficiency (though the size changes by ±8% with fre- quency, decreasing with increasing frequency, we keep the same median case for all the fig- ures).Theprimarybeamcouplingcorrectionis notappliedinthepresentandfollowingfigures. 3.1. Continuummap detailinthisworkalongwiththethreerunawaysources(BN,I, and n), and the methyl formate peak 6 (MF6). The continuum Owing to the density of lines, it is somewhat difficult to find emission(attheHCposition)hasapeakvalueof∼1.2Jy/beam enoughchannelsfreeofemissiontobuildacontinuummap.We after correcting for primary beam coupling, which corresponds couldfindtworeasonablycleanfrequencyrangesinthe218and toabrightnessof∼2.9×104 MJy/sr. 235GHzbands(bands4and11resp.),eachconstitutingaselec- tionofchannelsacrossthe1GHzbandpass,whichgavesimilar 3.2. Lineemission results, confirming that the channels were not polluted by line emission.Figure1showstheresultingcontinuumemissionmap Several molecular components, that can be distinguished both togetherwiththepositionsofthetensourceswearestudyingin spatially and spectroscopically, are associated with Orion-KL. A32,page3of87 A&A604,A32(2017) Table2.Orion-KLmolecularcomponents. Component RA Dec Size (cid:51) ∆v T n(H ) N(H ) J2000 J2000 LSR Kin 2 2 05h35m... −05◦22(cid:48)... (arcsec) (kms−1) (kms−1) (K) (cm−3) (cm−2) extendedridge 14s.6 21(cid:48).(cid:48)5 ∼180 8–10 2.5–5 40–60 ∼1×105 7.1×1022 plateau 14s.516 30(cid:48).(cid:48)59 20–30 5–10 20 95–150 1–10×106 1.8×1023 hotcore 14s.6 31(cid:48).(cid:48)0 5–10 4–6 5–15 150–400 1–10×107 3.1–10×1023 hotcore(peak) 7.3×108 5.4×1024 compactridge/MF1 14s.09 36(cid:48).(cid:48)9 5–15 7–9 1–2 80–150 1–10×106 3.9×1023 compactridge(peak) 6.8×108 5.0×1024 IRc7 14s.26 31(cid:48).(cid:48)29 ∼2 −2–8 2.5–5 ∼160 – – IRc21 14s.557 27(cid:48).(cid:48)13 ∼2 ∼6 2.5 ∼160 – – MF2 14s.44 34(cid:48).(cid:48)4 ∼2 3–17 2.5–6 100–150 4.2×108 3.1×1024 MF4/IRc20 14s.132 29(cid:48).(cid:48)3 ∼2 7–14 2–8 ∼100 2.2×108 1.6×1024 MF5/IRc6 14s.158 27(cid:48).(cid:48)83 ∼2 6.5–13 2.5–6 ∼100 2.2×108 1.6×1024 MF10/IRc2 14s.63 28(cid:48).(cid:48)9 ∼2 -3–7 3–5 150–200 – – MF12/IRc4 14s.188 34(cid:48).(cid:48)44 ∼2 0–11 2–5 100–150 – – EGP 14s.47 33(cid:48).(cid:48)17 ∼2 −7–12 3–6 100–140 – – Notes.ForfurtherdetailsseeIrvineetal.(1987),Blakeetal.(1987),andFavreetal.(2011a).ExtendedRidgeandPlateauarequotedforcom- pleteness but not discussed in this paper, their positions are simply given as those of Orion KL and Source I, respectively. All other source positionsandsizesarefromthispaperorfromFavreetal.(2011a)exceptEGP=ethyleneglycolpeakfromBrouilletetal.(2015).Peakdensities andcolumndensitiesfortheHCandtheCRandforsomeoftheMFpeaksaremeasuredina1.8(cid:48)(cid:48)×0.8(cid:48)(cid:48)beam(Favreetal.2011a)butshouldbe consideredcautiously.OurpositionsofIRc7andIRc21areclosertothepositionsofC23andC13sourcesofFriedel&Weaver(2011)thantothe IRcpositionsofShupingetal.(2004)whiletheyareprobablythesameobjects,respectively. The hot core, compact ridge, extended ridge and plateau have known in other sources are not detected (the list of species is beendescribedinanumberofpapers(e.g.Mangumetal.1990; presentedinTableB.1).Twospecies,thedioxygen18Oisotopo- Lerateetal. 2008; Friedel&Weaver 2011). A sketch illustrat- logue (16O18O) and hydroxylamine (NH OH), have been ac- 2 ingthepositionofthesecomponentsintheplaneofskyisgiven tivelysearchedforintheinterstellarmedium,buthavestill not by Irvineetal. (1987). In addition, interferometric studies of beendetected. complexorganicmoleculeshaverevealedthepresenceofother Figure 2 displays the ensemble of the collected spectra for molecular clumps within Orion-KL (see e.g. Friedel&Snyder all ten sources in band 1, while Fig. 3 displays the same data 2008; Favreetal. 2011a,b; Friedel&WidicusWeaver 2012; expandingtheverticalaxistoshowemissionbelow5Ktohigh- Brouilletetal. 2013; Pengetal. 2013). Table 2 lists the main lighttheweakerlines.All16bandsarepresentedinAppendixA, physicalparametersofthemolecularcomponents. Wehaveex- Figs.A.1–A.16,andA.17–A.32.Thesamedataplusthecombi- tractedspectrafortensourceslabeledinFig.1,convertedthem nationofthefitstoindividualspeciesissubsequentlydisplayed to an antenna (main beam) temperature scale using the con- in the same appendix in order to give an idea of the unknown version factor listed in Table 1, corrected them for beam cou- lines that remain (Figs. A.33–A.48 and A.49–A.64). It is inter- pling by measuring the primary beam coupling at the source esting to see that due to the absence of beam dilution for all position (Fig. 1), and removed any residual continuum offset sources, a large number of lines are stronger than 5 K, unlike (typically 0.2–0.5 K, maximum 2 K). Hereafter, bands will be in reported surveys from the 30 m and other single-dish tele- called by their number, for example band 1 for the 215150 to scopes (e.g. Terceroetal. 2010). Depending on the source, 13 216087 MHz band, which was spectral window #3 in the first to 29% of the channels are above 5 K, and this is only a lower group of observations (=spw3/sg1, see Table 1). Nine sources limitsincetheintensityoflinesthatareproducedbyspatiallyex- are infrared compact sources and sometimes methyl formate tendedemissionisreducedbythelackofzero-spacingdata.For (MF) sources (Favreetal. 2011a). One source, not known as thestrongestlinesthisisclearlyseenintheirdistortedlineshape, an infrared peak or a MF peak but situated between the MF2 including strongly negative channels (see, e.g., the SO line at andMF6peakshasbeennamedtheethyleneglycolpeak(here- 215220.653MHzinFig.2)andwhatitwouldbefromanesti- afterEt.GlycolinthefiguresorEGPinthetext),followingthe matedfit(Fig.A.33). discovery of aGg(cid:48) ethylene glycol ((CH OH) ) in this location 2 2 (Brouilletetal.2015).WedidnotanalyzeMF6becauseaquick 3.3. Detectionofnewspeciesandnewvibrationallyexcited inspection showed that apart from the SiO maser centered on sourceIandoverlappingwithHC,thereislittledifferenceinthe statesinOrion mainlineshapesandratiosbetweenMF6andHC. We report the first detection in Orion of gGg(cid:48) ethylene glycol Wehaveexaminedourdataforthepresenceofover130can- isomer((CH OH) )andofaceticacid(CH COOH),whichwill 2 2 3 didate species (where a species corresponds to one entry in be presented elsewhere (Favre et al. 2017). We have also de- the JPL (Pickettetal. 1998) or CDMS (Mülleretal. 2005) cat- tected for the first time in Orion, n- and i-propyl cyanide con- alogues, which differentiate vibrationally excited states, iso- formers(C H CN).Afewcyanoacetylene(HC N)vibrationally 3 7 3 topologues,isomersandconformers,representing∼60different excitedtransitionsarealso(probably)detectedhereforthefirst species and ∼70 if we differentiate the isomers and conform- time, both for the main isotopologue and for the three singly ers).Ofthe∼130candidates,∼90speciesaresecurelyidentified, 13Csubstitutedisotopologues(someofthemhavebeenreported 11 species are tentatively detected, and ∼35 species already in Espluguesetal. 2013, and a contemporary paper published A32,page4of87 L.Pagani etal.:ThecomplexityofOrion:anALMAview.I. Fig.2.Spectrafromtheband1setupforalltensources.Theredlineindicatesthe0K(continuum-removed)level. A32,page5of87 A&A604,A32(2017) Fig.3.Spectrafromtheband1setupforalltensourceswithafixedmaximumtemperaturescaleof5Ktohighlighttheweakerlines.Theredline indicatesthe0K(continuum-removed)level. A32,page6of87 L.Pagani etal.:ThecomplexityofOrion:anALMAview.I. Fig.4.Detectionofn-C H CNpropylcyanideisomertowardsIRc21(seemapFig.1).Inthisandthefollowingfigures,themostintenselinesare 3 7 displayed(i.e.linestypicallystrongerthan∼5σ.Weakerlinesarehardlyornotatalldetectableandhavenoimpactontheresults,nordolines blendedwithmuchstrongerlinesofotherspecies).Thedataareinblackandthefitisinred.Thesummationofthefitofallthespecieswehave identifiedisdisplayedinblue. after the submission of the present paper also presents a study theweakeriisomer.Thevariationofthisn/iratiofrom2to6is of some of these vibrationally excited states; Pengetal. 2017). compatiblewiththemodelingproposedbyGarrodetal.(2017) Except for the gGg(cid:48) ethylene glycol isomer, only detected to- forthemediumandfastwarm-uptimescalesoftheicesinwhich wards IRAS16293 A/B (Jørgensenetal. 2016), all the species the propyl cyanide was produced, supposing a high activation wepresentherehavebeenseeninsomeothermassivestarform- energy for reactions of CN with double-bonded hydrocarbons. ingregions,especiallyinSgrB2(B13discussallofthesedetec- Therefore, it may be a hint to how the origins of these species tionsconcernedwithSgrB2thoughsomepredatethatwork). relate to the environment as the different clumps were and are likelyexposedtoadifferentialheatingbothbeforeandafterthe 500-year-oldexplosion. 3.3.1. PropylcyanideC H CN 3 7 Both n- and i-propyl cyanide isomer are detected (spec- Inthecaseofsuchrelativelyrarespecies,blendingwithother troscopic data are provided by Demaison&Dreizler 1982; species in different portions of the region is unavoidable, and Vormann&Dreizler1988;Wlodarczaketal.1988,fortheniso- thereforeanintensitymapofthespeciesemissionwouldbemis- merandbyMülleretal.2011,fortheiisomer).Wemainlyde- leading.Figure6showstheintegratedlineintensitycontourmap tectthemtowardsIRc7,IRc21,MF2,andMF10,withatentative oftheseeminglyisolated236.990GHztransition(Fig.4)super- detectionofthenisomertowardsEGP(Figs.4andb).Sincethe imposed on the continuum map of the region. While C H CN 3 7 spatialextentofthesetwospeciesislimited,wecanestimatea seems to clearly peak on MF2, the real peak is towards IRc21. first-orderLTEcolumndensityforagiventemperature.Towards The MF2 peak presents a mixture of an unidentified line with theIRc21peak,wefindacolumndensityof1×1015cm−2 fora propyl cyanide at that frequency. The second strongest peak, temperatureof160Kforthenisomerandhalfthatvalueforthe towards CR/MF1 is purely coincidental and does not represent i isomer. This n/i ratio is similar to what Bellocheetal. (2014) thisspecies,astheunsuccessfulfitattemptshows(Fig. 7).This findtowardsSgrB2.However,thisisnotthecaseforMF10(ra- problemisgeneralandgreatcareshouldbetakenwhenexamin- tio of 3) nor for MF2 (ratio of 6). The column density of the ingintensitymapsofspeciesinOrion.Identificationofaspecies nstructuralisomeristoosmalltowardsIRc7tobeabletodetect basedonasinglecomponentinoneofthestudiedsources,even A32,page7of87 A&A604,A32(2017) Fig.5.SameasFig.4forthedetectionofthei-C H CNpropylcyanideisomer. 3 7 (HC N, (cid:51) = 1, 2), there were a few further attempts to iden- 3 7 tify higher excitation levels in this source, and finally the large work of Espluguesetal. (2013), which combines IRAM 30 m and Herschel HIFI data, reported numerous excited states (up to (cid:51) =(cid:51) = 1). It can also be noted that vibrationally excited 6 7 statesofnumerousotherspeciesarenowknown(e.g.Dalyetal. 2013; Lópezetal. 2014). Turner (1991) invokes the HC N (cid:51) 3 6 = 1 transition in his analysis of a 3 mm NRAO survey, but all the transitions are always mixed with (cid:51) = 1 lines and are not 7 detected separately. Since the (cid:51) = 1 lines are much stronger, 7 the actual identification of the (cid:51) = 1 mode was not secure. 6 deVicenteetal. (2002) report the detection of (cid:51) = 1, (cid:51) = 1, 5 6 and(cid:51) =1.Theyclaimtohavedetectedalltheseexcitedstates, 7 butshownodatafor(cid:51) = 1.Simultaneouslywithandindepen- 6 dentlyfromthiswork,Pengetal.(2017)publishedastudybased ontheSV0dataonpartofthevibrationallyexcitedstateswere- porthere.Wenotethatintheirstudytheypresentthe(cid:51) =1and 5 (cid:51) = 3 data separately, while the CDMS present them together, 7 which is the recommended way to proceed since the states are coupled(Fermicoupling,HSPMüller,priv.comm.). Fig. 6. Integrated intensity map of the 236.990 GHz set of the n- We have detected several vibrationally excited states of C H CNisomertransitions(whitecontours)superimposedonthecon- tin3uu7mmap.TheemissiontowardIRc7andIRc21andpartoftheemis- HC3N throughout the region and also the three 13C singly sub- sion toward MF2 are due to this species. Emission in other regions, stituted isotopologues, H13CCCN, HC13CCN, and HCC13CN. especially the relatively strong emission seen toward CR/MF1 is due SpectroscopicdataaretakenfromThorwirthetal.(2000),which toemissionfromothermolecularspeciesatdifferentvelocitiesandap- is the most recent published measurement for HC N, and from 3 pearingatthesamefrequency. Thorwirthetal. (2001) for the 13C isotopologues. The highest energyvibrationallyexcitedstatewecanreportwithconfidence ifthespeciesisclearlyidentifiedsomewhereelseintheregion, is the (cid:51) =(cid:51) = 1 state, at E ≈ 1170 K and the emission is 6 7 up mustthereforeremainverytentative. located near the HC. These are the same states as reported by Espluguesetal. (2013) from their single-dish survey. The next states, in the range 1400–1600K, ((cid:51) = 4/(cid:51) =(cid:51) = 1, (cid:51) = 1, 3.3.2. VibrationallyexcitedHC3Nand13Csinglysubstituted and(cid:51) =2)arepossiblyseenbutnot7securely7dete5cted3(F4ig.8). cyanoacetyleneisotopologues 6 AftertheearlyworkbyGoldsmithetal.(1982,1983),whode- 3 ForanenergyleveldiagramofthevibrationalstatesofHC N,see 3 tectedthefirsttwovibrationallyexcitedstatesofcyanoacetylene Yamada&Creswell(1986). A32,page8of87 L.Pagani etal.:ThecomplexityofOrion:anALMAview.I. Fig.7.CR/MF1displayofexpectedn-C H CNcomponents.DespitethecoincidentalemissionpeaktowardsCR/MF1inFig.6thatisvisiblein 3 7 the236.99GHzwindow,n-C H CNisnotdetectedinthissourceatasimilarleveltothatseeninIRc21(Fig.4).Color-codingandT scaleas 3 7 MB inFig.4. Other excited states are reported from Sgr B2 observations in HC-North in Pengetal. 2017), the lines are stronger and less B13butwerenotfoundinourdata.Sincethevibrationallyex- blendedthantowardsHCandgivebetterresults(Fig.10). cited modes are probably pumped by IR radiation, we did not try to evaluate the column density for any of these states since their temperature is not physically related to the local gas tem- 3.4. TentativedetectionofnewspeciesinOrion perature. Furthermore, their excitation temperature within each Anumberofspecies,alreadyknownintheinterstellarmedium vibrationalstateinvolvestransitionswithupperlevelstooclose butnotdetectedinOriontothebestofourknowledge,havebeen inenergytoallowasecurerotationaldiagramanalysistobeper- tentativelydetectedinthissurvey.Cautionshouldbeexercised, formed.Aspreviouslynotedbyseveralauthors(e.g.Fengetal. however.AswediscussinSect.3.5.1,eventhedetectionofthree 2015;Pengetal.2017),theseexcitedmodesaremostlysituated inthenorthernpartoftheregion(Fig.9).Indeed,thoughthe(cid:51) = linesofaspeciesisnotaclearproofofitspresence,independent 7 oftheirsignal-to-noiseratios.Wethereforereportthesetentative 1 and 2 states are detected even towards the CR in the south- detections for the sake of completeness. The addition of zero- ernpartoftheregion,thehigherstatesareonlydetectedfarther spacing data in the future will possibly allow a better cleaning north. The excited state emission is mostly concentrated in an ofthespectraandwehopethatsomeofthesedetectionswillbe arc around the explosion center (Fig. 9). If they are related, it secured.Allthebasicinformationforthesespeciescanbefound wouldbeviacollisionalexcitationratherthaninfraredpumping attheCDMSwebpage“MoleculesinSpace”4. butallspeciesemittinginthesamearcdonotseemtoshowthe same high excitation level. We discuss the possible impact of the500-year-oldexplosioninSect.4.4andinafuturepaperon the different behavior of cyanide- and oxygen-bearing complex 3.4.1. MethylamineCH3NH2 organicmoleculesinOrion-KL(Paganietal.,inprep.). MethylaminewasdetectedearlyontowardsSgrB2(Kaifuetal. Wehavealsodetectedthe13Csinglysubstitutedcyanoacety- 1974;Fourikisetal.1974).Thesamepapersreportitsdetection leneisotopologuesinthevibrationalstates(cid:51)7=1and2.Thenext inOrion,butJohanssonetal.(1984)provedthesedetectionsto vibrational level ((cid:51) = 1) is most probably present, but all lines 6 are weak and often blended (the H13CCCN (cid:51) = 1 vibrational 6 state has no transitions in our bands). Towards IRc21 (named 4 http://www.astro.uni-koeln.de/cdms/molecules A32,page9of87 A&A604,A32(2017) Though the fitting parameters are equivalent towards the gly- col peak and MF2, the blending is slightly less severe towards MF2, which we display here. Spectroscopic data are provided byButleretal.(2001). 3.4.4. 13Cdoublysubstitutedcyanoacetyleneisotopologues The 13C doubly substituted cyanoacetylene isotopologues have still only been tentatively detected in CRL618 (Pardo & Cernicharo 2007) and Sgr B2 (Bellocheetal. 2016). Again, in Orion, the three 13C doubly substituted cyanoacetylene iso- topologues are possibly detected towards IRc21 in the fun- damental vibrational state (Fig. 14). The abundance ratio, in the ground vibrational state, between singly (averaged over the three isotopologues) and doubly substituted isotopologues is ∼45, but because of blending, this value is likely underesti- matedbutconsistentwithpreviousreports(Pardo&Cernicharo 2007;Bellocheetal.2016).Spectroscopicdataareprovidedby Thorwirthetal.(2001). 3.4.5. 13CsubstitutedIminomethylium,H13CNH+ To the best of our knowledge, iminomethylium (HCNH+) has not yet been reported in Orion. This cation has no transition in Fig. 8. Cyanoacetylene (HC3N) vibrationally excited transitions to- our frequency coverage. Its (J:3–2) line, where J is the rota- wardstheHC.Thefitshelptotracethecomponents,buthavelimited tional quantum number (representing the total angular momen- physicalsignificancebecausetheirtemperatureisnotconstrained.The tum excluding nuclear spin), is at 222.329 GHz. Its presence (cid:51) = 1lineat218.861or237.093GHzdisplaysashoulderduetothe (cid:51)7 = 1at218.854and237.086GHz,respectively).Color-codingasin must be verified in the reduced SV0 data as soon as they be- 6 come available. The 13C substituted isotopologue, H13CNH+ is Fig.4. observed in a single transition within the frequency range cov- ered, and is identified towards all sources, being the strongest be incorrect5. To the best of our knowledge, this species has towardsCR/MF1(Fig.15).Withonlyonelineobserved,itcan not been reported in Orion since these early works. The line at best be a tentative detection, since the density of unknown remains difficult to identify, but towards the hot core, a tenta- linesabove10Kis∼3.8GHz−1towardsCR/MF1.Itisonly∼3K tive detection can be reported thanks to several lines fitting the inMF2andisweakeverywhereelse(0.5–1.0K).Ifconfirmed, expected emission (Fig. 11, spectroscopic data are provided by thehigherabundanceofiminomethyliumintherichestsourcein Motiyenkoetal. 2014). Possible detections are also found to- oxygen-carriercomplexorganicmolecules(hereafterO-COMs) wardsIRc7,MF2,MF5,andMF10.TowardstheHC,forT = isaninterestingchemicalproblem,whichisbeyondthescopeof ex 280K,wefindacolumndensityof1×1016cm−2. thispaper.SpectroscopydataareprovidedbyAmano&Tanaka (1986). 3.4.2. CyanamideNH CN 2 3.4.6. PropanalCH CH CHO,propenalCH CHCHO, 3 2 2 ThisspecieshasbeententativelydetectedbyLópezetal.(2014). andpropynalCHCCHO Ourdetectionconfirmstheirwork(stilltentatively),butthesig- nal seems to come primarily from the EGP rather than from Thethreealdehydesderivedfrompropane,propeneandpropyne the HC (which Lópezetal. 2014, could not distinguish in their haveneverbeenobservedinOrion.Theirlargenumberoftran- single-dishdata),2(cid:48)(cid:48) farthernorth,andatavelocityof8kms−1 sitionsandweakemissionduetoarelativelylowabundancein instead of 5 (Fig. 12). Towards the EGP, the fit indicates a this source make them difficult to detect, especially when the column density of 1.1× 1014cm−2 for T = 140 K. Spectro- zero-spacing data is missing, producing negative features that ex scopicdataareprovidedbyJohnsonetal.(1976),Moruzzietal. caneraseweaksignalsatthelimitofsensitivityoftheobserva- (1998). tions. We possibly detect propanal (spectroscopic data are pro- videdbyHardyetal.1982;Demaisonetal.1987)andpropenal (spectroscopic data are provided by Dalyetal. 2015) towards 3.4.3. GlycolaldehydeCH (OH)CHO 2 IRc21(Figs.16and17)andverytentativelypropynal(spectro- Of the three C H O isomers, glycolaldehyde, acetic acid, and scopic data are provided by Winnewisser 1973; McKellaretal. 2 4 2 methyl formate, only the last is widely spread in molecular 2008; Barrosetal. 2015) towards the EGP (Fig. 18). Concern- cloudsandalreadyknowninOrion.Ourdetectionofglycolalde- ingpropenal,threeorpossiblyfourveryweaklinesatthe3–5σ hydeissomewhatuncertainbecausemanylinesareblendedand levelarenotseenoutofthestrongest23lineswereport(allre- weconservativelydeclarethedetectiontobetentative(Fig.13). maining lines not presented here are too weak to be detectable in our data). We consider that these non-detections are not sig- 5 ThisinformationhasbeentakenfromtheCDMSwebpageonmethy- nificant. Propynal is not seen towards the same source because lamine: http://www.astro.uni-koeln.de/site/vorhersagen/ allpropynallinesareweakandblendedexceptthepossiblepair molecules/ism/MeNH2.html we present here. The 217.437 propynal transition is somewhat A32,page10of87

compact ridge/MF1. 14s.09. 36.9. 5–15. 7–9. 1–2. 80–150. 1–10 × 106. 3.9 × 1023 compact ridge (peak). 6.8 × 108. 5.0 × 1024. IRc7. 14s.26. 31.29. ∼2. −2– 8 .. Despite the coincidental emission peak towards CR/MF1 in Fig. 6 that is Goldsmith, P. F., Snell, R. L., Erickson, N. R.
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