Catching a Grown-Up Starfish Planetary Nebula: I. Morpho-Kinematical study of PC 22

6.7 MB·

by  L. Sabin

MNRAS000,1–??(2016) Preprint2February2017 CompiledusingMNRASLATEXstylefilev3.0
Catching a Grown-Up Starfish Planetary Nebula: I.
Morpho-Kinematical study of PC22
L. Sabin1(cid:63), M.A. Gómez-Muñoz1, M.A. Guerrero2, S. Zavala3,4, G. Ramos-Larios5,
R. Vázquez1, L. Corral5, M.W. Blanco Cárdenas1, P.F. Guillén1, L. Olguín6, C. Morisset7,
S. Navarro5
1InstitutodeAstronomía,UniversidadNacionalAutónomadeMéxico,Apdo.Postal877,22800Ensenada,B.C.,Mexico
7 2InstitutodeAstrofísicadeAndalucía,IAA-CSIC,C/GlorietadelaAstronomías/n,18008Granada,Spain
1 3InstitutoTecnológicodeEnsenada,BlvdTecnológicoNo.150,22780Ensenada,B.C.,Mexico
0 4InstitutodeEstudiosAvanzadosdeBajaCalifornia,A.C.,BlvdTte.Azueta147,Edif.MatematikéPlantaBaja,22800Ensenada,B.C.,Mexico
2 5InstitutodeAstronomíayMeteorología,Av.VallartaNo.2602,Col.ArcosVallarta,C.P.44130Guadalajara,Jalisco,Mexico
6Dpto.deInvestigaciónenFísica,UniversidaddeSonora,Blvd.Rosales-Colosio,Ed.3H,83190,Hermosillo,Sonora,Mexico
n 7InstitutodeAstronomía,UniversidadNacionalAutónomadeMéxico,Apdo.Postal70264,MexicoD.F.04510,Mexico
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Lastupdated2016xxxx;inoriginalform2016xxxx
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R ABSTRACT
S
. We present the first part of an investigation on the planetary nebula (PN) PC22 which
h
focuses on the use of deep imaging and high resolution echelle spectroscopy to perform a
p
detailedmorpho-kinematicalanalysis.PC22isrevealedtobeamultipolarPNemittingpre-
-
o dominantly in [OIII] and displaying multiple non-symmetric outflows. Its central region is
r foundtobealsoparticularlyinhomogeneouswithaseriesoflowionizationstructures(knots)
t
s locatedonthepathoftheoutflows.Themorpho-kinematicalmodelobtainedwithSHAPEin-
a dicatesthati)thede-projectedvelocitiesoftheoutflowsareratherlarge,(cid:62)100kms−1,while
[ the central region has expansion velocities in the range ∼25 to ∼45 kms−1 following the

1 “Wilsoneffect”,ii)themajorityofthemeasuredstructuressharesimilarinclination,(cid:39)100◦,
v i.e. they are coplanar, and iii) all outflows and lobes are coeval (within the uncertainties).
9 All these results make us to suggest that PC22 is an evolved starfish PN. We propose that
2 themechanismresponsibleforthemorphologyofPC22consistsofawind-shellinteraction,
0 wherethefastpost-AGBwindflowsthroughafilamentaryAGBshellwithsomelargevoids.
0
0 Keywords: (ISM:)planetarynebulae:individual:PC22—ISM:jetsandoutflows—ISM:
. kinematicsanddynamics
2
0
7
1
:
v 1 INTRODUCTION 2011), and NGC6309 (Vázquez et al. 2008). With this aim in
i mind, we present in this article a detailed investigation of a pe-
X Planetary Nebulae (PNe) are well known for displaying different
degreesofmorphologicalcomplexityprobingtheir,oftenintense, culiarPN,PC22(PNG051.0−04.5)locatedatα2000=19:42:03.50,
ar internaldynamicalactivity(seetheimagingcataloguesby,Parker δ2000=+13:50:37.33.
DiscoveredbyApriamashvili(1959)andlatercataloguedby
etal.2006,2016;Sahaietal.2011andSabinetal.2014).Hence,
Peimbert&Costero(1961),thisobject,hasnotbeensubjectofany
thepresenceofoutflows,jets,ringsorknotseachindicateparticular
extensive targeted study so far. Manchado et al. (1996) classified
physicalprocesseswhoseoriginsarenotalwayswellconstrained.
PC22 as an elliptical planetary nebula with “internal structures”
By establishing with accuracy the morpho-kinematics and chem-
(no description of these were made). Although no binary system
ical characteristics of PNe, one can expect to better understand
has been detected, Soker (1997) predicted a high probability for
their formation history. Such multi-approach analyses have been
the progenitor to have gone through a common envelope with a
performedtostudyingreatdetailvariousPNesuchasNGC3132
sub-stellarcompanionbasedonthismorphology.Exceptforpho-
(Monteiroetal.2000),IPHASXJ194359.5+170901(Corradietal.
tometric measurements realized at various wavelengths we found
2011),K4-55andKn26(Guerreroetal.1996,2013,respectively),
nootherrelevantpieceofinformationaboutthePN.
M2-48 (López-Martín et al. 2002), ETHOS1 (Miszalski et al.
ThedistancetoPC22seemstoberelativelywellconstrained.
Tajitsu & Tamura (1998) obtained a distance of 5.5 kpc for this
(cid:63) E-mail:[email protected](LS) object by fitting a blackbody to the flux of the four IRAS bands,
(cid:13)c 2016TheAuthors
2 L.Sabinetal.
whereasGiammancoetal.(2011)estimatedadistanceof4.0±0.5 Thewavelength-calibrationwasperformedwithaThArarclamp
kpc based on the distance-extinction method built with the first toanaccuracyof±1kms−1.TheFWHMofthearclampemission
IPHAS data release1 . More recently Frew et al. (2016), us- lines,(cid:39)12±1kms−1,providesanestimateofthespectralresolu-
ing a new Hα surface brightness-radius relation, derived a mean tion.
distance of 5.27±1.52 kpc adopting log(S(Hα))= –2.77±0.10
ergcm−2s−1sr−1.
In this paper we present new deep morpho-kinematical ob- 2.3 ESPRESSOmulti-orderopticalechellespectroscopy
servationswhichrevealawealthofinformationonPC22andas-
Multi-orderechellespectroscopicobservationswereperformedon
sert its physical structure. The article is organized as the follow-
2014May29usingESPRESSO,anEchellespectrographmounted
ing:theobservationsaredescribedin§2;theresultsobtainedfrom
onthe2.12mtelescopeattheOAN-SPM(Mexico).TheE2VCCD
eachobservingtechniquearedescribedin§3andthisincludesour
detectordescribedabovewasused.Thewavelengthrangecovered
proposed kinematical model. Finally we conclude our investiga-
was 3900–7290 Å distributed through 27 orders with a spectral
tionpresentingthemainfindingsin§4followedbythediscussion
scale∼0.1Åpixel−1 at5000Å.Theslitwaspositionedatanan-
and concluding remarks in §5. This is the first paper on a series
gleof47◦passingthroughthecentralstar.Nobinningwasapplied
which focuses on the morpho-kinematical analysis of PC22. We
andtheexposuretimewassetto1800s.Thedatareduction,which
will present a comprehensive chemical analysis in a forthcoming
includes bias removal and flat fielding correction, was performed
paper(Sabinetal.inpreparation).
withMIDAS(Grosbol1989).Two-dimensionalspectraofeachor-
derwasthenextractedandwavelengthcalibratedwithaThArarc
lampusingIRAFroutines.Wenotetheabsolutewavelengthcali-
2 OBSERVATIONS brationofthespectralorderscoveringthe[OIII]λ5007and[ArV]
λ7006emissionlineswasnotoptimal.Nofluxcalibrationwasper-
2.1 ALFOSCopticalimaging
formed.Eachorderwasthenanalyzedseparatelyandnoattemptto
Direct narrow-band images of PC22 were obtained on 2009 bringthemtogetherwasmade.
September 4 using the Alhambra Faint Object Spectrograph and
Camera (ALFOSC) at the 2.5m Nordic Optical Telescope (NOT)
at the Roque de los Muchachos Observatory (ORM, La Palma,
3 RESULTS
Spain). The detector was a 2048×2048 EEV CCD (13.5µm
pixel size) with a plate scale of 0.(cid:48)(cid:48)184 pix−1 providing a field 3.1 Morphology
of view of 6.(cid:48)3×6.(cid:48)3. The Hα (λc=6567Å, FWHM=8Å),
[NII] (λc=6588Å, FWHM=9Å), and [OIII] (λc=5007Å, OurdeepandhighresolutionHα,[NII]and[OIII]imagesofPC22
FWHM=30Å) filters were used to acquire two 900s images in unveiladetailedpictureofacomplexmultipolarmorphology.The
eachfilter.TheimageswereprocessedusingstandardIRAFrou- “elliptical”structureoncebelievedtoformthewholenebulaisac-
tines.Ameanspatialresolutionof0.(cid:48)(cid:48)6wasachieved,asdetermined tuallythecentralpartofaPNwithmultipleoutflows(Fig.1).We
fromtheFWHMofstarsinthefield. identifiedsixlargelobesoroutflows(numbered1-6inFig.1)and
threesecondarylobesoroutflowsclosertothecentralellipticalre-
gion(numbered7-9inFig.1).The[OIII]5007Ånebularemission
2.2 MESlong-slithighresolutionopticalspectroscopy issignificantlybrightandshowsanextensionof∼1.(cid:48)5×0.(cid:48)9includ-
ingthetipofthefaintestcomponentspresentedinFig.2andFig.3.
Long-slit high dispersion optical spectra of PC22 were acquired
Thehighlevelof[OIII]5007Åemissionissomewhatpeculiarasit
with the Manchester Echelle Spectrograph (MES, Meaburn et al.
extendsuptotheoutermostregionsofthePNandisnotconfined
2003) mounted on the 2.12m telescope at the Observatorio As-
to the inner parts of the nebula as one would expect (i.e. there is
tronómico Nacional, San Pedro Mártir (OAN-SPM, Mexico). A
nostratificationintheemissionlinesdistribution).Suchbehavior,
firstsetofdatawasobtainedon2015August14-16.Atthistime,a
2048×2048pixelsE2VCCDwithapixelsizeof13.5µmpixel−1 however,isnotuniqueandithasbeennotedinotherPNesuchas
was used as detector. The fixed slit length is 6.(cid:48)5 and we set the NGC6309(Rubioetal.2015)andNGC6905(Cuestaetal.1993).
slitwidthto150µm(1.(cid:48)(cid:48)9).Weused2×2and4×4binningslead- Thefaintaforementionedstructuresareundertheformoffila-
ingtospatialscalesof0.(cid:48)(cid:48)351pixel−1 and0.(cid:48)(cid:48)702 pixel−1,respec- ments(inthesouthforexample)andweakoutflowswhicharebest
seeninthecontrast-enhancedimageshowninFig.3.Threearc-like
tively. The different spectra were taken with exposures of 1200 s
patterns,labelled“A,BandC”canbeassociatedtothetipsofthree
and1800sthroughtwofilters:anHα filterwith∆λ =90Åtoiso-
late the 87th order (0.05 and 0.1 Åpixel−1 spectral scale for the differentoutflowsdetailedbelow.
TheHα and[OIII]imagesindicateabrightandslightlycol-
2×2binningand4×4binning,respectively)andan[OIII]5007Å
limatedgroupofejectaalongtheSE-NWdirection(hereafterAxis
filterwith∆λ =50Åtoisolatethe114thorder(0.043and0.086
Åpixel−1spectralscaleforthe2×2binningand4×4binning,re- 1), with the NW outflow appearing to be “broken” by the emer-
genceofanewonewhosemuchdimerrimismostlyseenin[OIII]
spectively).Wemostlyusedthelatterfilterbasedonthedominant
(Fig. 3– label “C”). This effect is not symmetric, i.e. the struc-
[OIII]emissioninthePN(asseenintheimages,seebelow).Ad-
ture “C” does not have a clear counterpart in the SE outflow. In
ditional spectra were taken on 2016 February 25 using the same
the N-S direction (hereafter Axis 2), the presence of a bright in-
settings.
nersectionimmediatelyfollowedbyamuchfainteroneatlarger
All the spectra were bias and flat corrected, and wavelength
distances(seenin[OIII])couldindicatetheoccurrenceoftwodif-
calibratedusingstandardIRAFroutinesforlong-slitspectroscopy.
ferent outflows running approximately along the same direction.
Thepresenceofthesenewstructuresissupportedbythearc-like
1 SincethenanewphotometriccalibrationhasbeenperformedbyBar- patterns“A”and“B”observedinFig.3.Onceagain,thereisnot
entsenetal.(2014). aclear,symmetriccounterparttothenorthernoutflows.Fig.3also
MNRAS000,1–??(2016)
PropertiesofPC22 3
N
E
2
3
4
9
8
5
7
1
6
10", 0.25 pc
Figure1. NordicOpticalTelescopeRGBpictureofPC22(R=Hα,G=[NII],B=[OIII]).Theimagerevealsanon-homogeneouscentralellipticalstructure
andseveralejectionsreachingdistancesupto∼50(cid:48)(cid:48)fromthecentralstar.Thenumbersindicatethedifferentoutflowsidentifiedinthisnebula.
Ha [NII] [OIII]
10" 10" 10"
Figure2. Detailedgray-scalerenderingoftheHα,[NII],and[OIII]NOTimages.Inthelargestimages(FoV(cid:39)1.7(cid:48)×2.2(cid:48))thegray-scalelevelsarechosento
unveilthefaintestandmostdiffusedstructuresofthePN,whilesaturatingthecentralregions.Anumberofoutflowsandfilamentsareseenmostlyin[OIII].
Theinsetoneachfigureshowsazoomoftheellipticalcentralregionthatunderlinesitsinhomogeneitywithvarioushighdensityclumpsbestseenin[NII]
distributedaroundthecentralstar.
showsthattheejectaintheAxis2arewider,lesscollimated,less The“clumpy”/knottynatureofthisregionisbetterseenin[NII],
definedandgenerallyfainterthanthoseinAxis1.Thereisalsoa whichisaknowntraceroflowionizationstructurescomparedto
slightdifferenceinthedominatingemissionlines(andhenceinthe thehigherionization[OIII]emissionline(Corradietal.1996).We
ionization factor). Whereas [OIII] emission prevails in Axis 2, a produced different line ratio images, namely (Hα+[NII])/[OIII]
combination of Hα and [NII] emissions are prevalent in Axis 1. and[NII]/[OIII],tocheckforthepresenceofsuchpatterns(Fig.4).
Amoreexhaustiveanalysisofthesetworegions,fromachemical No new structures were revealed besides those already seen. In
pointofview,willbepresentedinthesecondpartofthisinvestiga- termsofspatialdistribution,theclumpsdescribedaboveareseen
tion(Sabinetal.inpreparation). insideand(mostly)attheedgesoftheellipticalring,i.e.,theinho-
mogeneitiesareconcentratedinthecentralregion.Moreprecisely
The central region of PC22 has a size of 13.(cid:48)(cid:48)5×23.(cid:48)(cid:48)9 and a
themainover-densitypositionsarecoincidentwiththebaseofthe
position angle (P.A.) on the plane of the sky of 49◦. It shows a
ejectarelatedtotheAxis1,suggestingtheirregularbrighteningor
notableinhomogeneousmorphologyinallemissionlines(Fig.2).
MNRAS000,1–??(2016)
4 L.Sabinetal.
A
B 2
C
1
D
Figure3. Leftpanel:[OIII]image(FoV(cid:39)1.7(cid:48)×2.2(cid:48))withgrey-scalelevelschosentohighlightthefaintestpatternssuchasthearcsoroutflowstipslabelled
A,B,andCandthefilamentarystructureD.Rightpanel:Gaussianfilteredratiomap(Hα+[NII])/[OIII](FoV(cid:39)1(cid:48)×1.2(cid:48))wherethelighterzonesimply
dominant[OIII]emissionoverHα+[NII].Thetwodottedlinesindicatethetwomainregionsoraxisshowingdifferentionizationdegrees.
10’’ Table1. DescriptionoftheslitsusedfortheMESobservations.”Offset
CSPN”correspondstotheslitoffsetfromthecentralstar.
Slit P.A. Filter OffsetCSPN Texp
(◦) ((cid:48)(cid:48)) (s)
A 5 [OIII] 0 1800
B 28 [OIII] 0 1800
C 49 [OIII],Hα 0 1200
D 49 [OIII] 13.3 1200
E 49 [OIII] 13.0 1200
F 75 [OIII] 0 1200
G 100 [OIII] 0 1200
H 137 [OIII],Hα 0 1200
I 137 [OIII] 10.0 1200
J 137 [OIII] 8.0 1200
Figure4.0[NI0.I00]9/9[O0I.0I3I]ra0.0t6i9om0.1a5pun0.3d1erly0.6i2ngt1h.2ebri2.g5htk5nots1a0ndclumpy K 166 [OIII] 0 1200
mediuminthecentralpartofPC22. L 128 [OIII] 2.1 1800
M 114 [OIII] 3.4 1800
ionization of material following the passage of a collimated out-
flows. Such interaction is not unusual and has been described by Table2. Kinematicalcharacteristics(i.e.velocitiesandage)foreightdif-
Vázquezetal.(2000)inM2-48. ferent structural components obtained from our best fitting model con-
The morphological analysis of PC22 unveils a much more structed with SHAPE (see Fig.7). Velocities are relative to the calculated
complex object than initially described by an elliptical morphol- systemicof36.4kms−1 andθ istheangularradiusmeasuredfromthe
ogy.ThePNshowsmultiplenonsymmetricejectawithtwomain centralstar.Wenotethatthede-projectedvelocity(Vdep)forstructure7is
likelytobe“affected“bythepresenceofothervelocityfieldcomponents
differingdegreesofionizationwhose“waist”seemstobeshaped
fromitssurrounding.
bytheinteractionwiththedifferentoutflows.
Structures Vrad θdep i Vdep tkin
3.2 Kinematics number (kms−1) ((cid:48)(cid:48)) (◦) (kms−1) (yrs)
3.2.1 Morpho-kinematicalmodellingofMESdatawithSHAPE 1 –9±3 12.1 83 131 2300±700
2 –40±7 13.2 74 140 2400±800
The large set of slit positions (see Fig. 5 and Tab. 1) provides a 3 –9±4 8.6 100 56 3800±1400
uniquecoverageofPC22tocarryoutacomprehensivekinemati- 4 21±4 8.3 100 59 3500±1300
calanalysis.Theobservationsusedinthefollowingwillbethose 5 23±3 15.1 103 101 3700±1200
takeninthe[OIII]line.Usingthesevenpositionspassingthrough 6 26±5 23.0 100 155 3700±1100
thecentralstar,wederivedameanobservedsystemicvelocityV¯ 7 12±3 5.4 100 33: 4100±2000
of28.1kms−1,whichcorrespondstoanLSRmeanvalueof36o.b4s 8 –7±3 6.5 100 48 3400±1400
kms−1.
AlthoughwewereabletosecureagoodmappingofthePN,
the overall higher brightness of the central region and the lobes
MNRAS000,1–??(2016)
PropertiesofPC22 5
N B A K N E
E C E
D
F
G
M
I
H L
J
10" 10"
Figure5. SlitpositionsusedfortheMESobservationssuperimposedontheopticalRGBpictureofPC22.Ontheleftpanelwepresentallthosepassing
throughthecentralstar(redsquare)andtheremainingareshownontherightpanel.ThethirteenpositionsaremeanttoprovidethebestcoverageofthePN
forthekinematicanalysis.
correspondingtotheAxis1weretheonlystructurestoactuallyap-
pearclearlyinthespectra,withtheothercomponentsbeingmuch
fainter. The upper panels of Fig. 6 show the resulting spectra or
position-velocity (PV) maps, passing through the short and long
axisofthemaininternalstructure(PA=49◦:slitCandPA=137◦:
slitH,respectively)andthebrightlobesinAxis1atPA=100◦cor-
responding to the slit G. In all three cases we note the irregular
shape of the inner regions which corresponds to the presence of
compactknots.TheremainingobservedPVmapsarepresentedin
theappendixA,Fig.A1andA2.
We subsequently used the morpho-kinematical tool SHAPE
(Steffen et al. 2011) to model all the PV diagrams and obtain a
completeviewofthe(kinematicalandmorphological)structureof
PC22. Due to the inhomogeneous nature of the central part, we
concentrated only on the representation and modelling of the ba-
sic velocity patterns corresponding to an equatorial ring and sev-
eralbipolaroutflows.Therefore,onewillobserveadifferencebe-
tweentheactual(thicker)observedspectraandthenarrowersyn-
theticones(seethelowerpanelsofFig.6).Thenon-inclusionof
theknots/clumpsdoesnothampertheoverallkinematicalanalysis.
We should keep in mind that the spectra are not treated indepen-
dentlyi.e.achangeintheposition/morphologyorthevelocityof
one spectrum will affect the position/morphology or the velocity
of the adjacent one(s). The full set of PV diagrams are shown in
Fig.6andtheappendicesA1andA2.ThesubsequentSHAPEre-
constructionofthePNisshowninFig.7.Table2summarizesthe
data for the brightest (and best defined) components. In this case
Figure 6. Top: MES [OIII] position-velocity (PV) plots of three of the
wederivedinformationforthetwonorthern“bumps”(#1,#2),the
mainslitpositionswithhighersignal-to-noiselevel,namelyslitpositions
southernsmalloutflow(#5),thefourextensionsoftheinternalel- C,G,andH(seeTab.1andFig.5,wheretheCandHslitsgoacrossthe
lipsoid(#3,4,7and8)andfinallyoneofthewesternoutflows(#6). nebulacenteralongP.A.49◦and137◦,respectively,andslitHisoffsetform
In all cases the velocities were measured at the tip of the struc- thecentralstarandgoesalongP.A.100◦.Thebinningfactoris2×2inall
tures.Foreachwecalculatedtheradialvelocities(Vrad)andtheir images.Bottom:SHAPEkinematicalmodellingoftheselinesforthemodel
respectiveerrors,thede-projectedangularradii(θdep),theinclina- assumedinthetext.
tions(i),de-projectedvelocities(V )andkinematicalages(t ).
dep kin
The errors on i and V were derived empirically solely based
dep
onourmodelandweestimatedameanerrorontheinclinationof
∼5◦ andameanerroronV of∼3kms−1.Thosearethetypi-
dep
calvaluesabovewhichweobservedanotablevariationinthePV
maps. The inclinations found indicate that most of the structures formervalueisverylikelyaffectedbynearbystructures),whichare
arenearlylyingintheplaneofthesky.Thededucedde-projected relatedtothecentralregion,andthehighvelocities(jets-like)ones,
velocitiesallowustodistinguishtwogroups:themediumveloci- above∼100kms−1relatedtothe“bumps”andlargeroutflows.
tiesstructures,from∼33to59kms−1 (althoughwenotethatthe Thekinematicalageofthesecomponentscanbederivedusing
MNRAS000,1–??(2016)
6 L.Sabinetal.
Table3. Kinematicalanalysisbasedonthedifferentlinesplitsobserved
in the ESPRESSO Echelle spectra at PA=47◦. The values were derived
throughaGaussianfitofthelines.Forboththeblue-andredshiftedlines
wepresent:theobservedvelocities(Vobs),theobserveddatacorrectedfrom
LSR(VLSR)andthevelocitiesrelativetothesystemic(Vrel).Notethat,due
todifficultiesintheabsolutewavelengthcalibrationofthespectralorders
coveringthe[OIII]and[ArV]emissionlines,onlytheobservedvelocities
arequotedfortheselines.
2 n
1 nn n 6 LineID Blueshiftedlines(km/s) Redshiftedlines(km/s)
3 n 8 Vobs VLSR Vrel Vobs VLSR Vrel
7 n
[OIII]5007 -21.9 – – 55.2 – –
n 4
n 5 HeII5411 -30.7 6.6 -29.8 37.7 74.9 38.6
HeI5876 -43.8 -6.5 -42.9 31.4 68.7 32.3
[SIII]6312 -33.2 4.1 -32.3 38.9 76.2 39.8
[NII]6548 -37.2 0.1 -36.3 40.9 78.3 41.8
HeII6560 -34.0 3.3 -33.1 29.3 66.6 30.2
Hα6563 -39.4 -2.1 -38.5 30.2 67.5 31.1
[NII]6583 -44.8 -7.5 -43.9 33.9 71.3 34.9
[SII]6716 -42.1 -4.8 -41.2 42.9 80.3 43.9
[SII]6731 -39.3 -1.9 -38.4 41.6 78.9 42.5
[ArV]7005 -41.9 – – 12.0 – –
[ArIII]7135 -37.5 -0.2 -36.6 42.8 80.2 43.8
Figure7. SHAPEreconstructionofPC22basedonallPVdiagrams.The
numbersindicatethestructuresofreferenceforthedifferentkinematical
calculations(seetable2).
Table4.Ionizationpotentialvsexpansionvelocityforthelinewithclear
splittingseeninPC22
therelationship:
4744∗d(kpc)∗θ((cid:48)(cid:48)) Ion Line Ionizationpotential Vexp
tkin= V (km/s) . (1) (Å) (eV) (kms−1)
dep
We can clearly see two groups: components #1 and #2, related [SII] 6716 10.36 42.5
to the northern “bumps” or small outflows, have a mean age of [SII] 6731 10.36 40.4
Hα 6563 13.59 34.8
2300±800yr,whereastheothercomponentshaveameanageof
3600±1300yr2.Theellipticalregion,ifinterpretedasaring,hasa [NII] 6548 14.53 39.1
[NII] 6583 14.53 39.4
kinematicalageof∼4500yrs.Withintheerrors,thedifferentcom-
[SIII] 6312 23.34 36.1
ponents are coeval, but we notice that the interaction of the out- HeI 5876 24.59 37.6
flowswiththecircumstellarmediumwouldreducetheirexpansion [ArIII] 7135 27.63 40.2
velocity (thus increasing their kinematical age). The kinematical [OIII] 5007 35.12 38.5
analysiscompletesthemorphologicalone,pointingtowardsaPN HeII 5411 54.42 34.2
mostly shaped by the interaction of high-velocity non-symmetric HeII 6560 54.42 31.6
winds,thezoneoftheinteractionbeingthecentralregionwhichas [ArV] 7006 59.81 26.9
aconsequenceishighlyinhomogeneous.Mostoftheevents(e.g.
outflowslaunching)alsoappeartohaveoccurredatapproximately
thesametimeinthelifeofthenotsooldPC22.Thiswillgiveus
animportantconstraintontheevolutionaryhistoryofthisPN(see
section5). fitting Gaussian curves to each component to derive their wave-
lengths.Weestimatedthatthemaximumerroronthelinemeasure-
mentis∼6kms−1.Table3reportstheobserved(V ),LSRcor-
obs
3.2.2 ESPRESSO rected(V ),andrelative(fromsystemicvelocity,V )velocities
LSR rel
forbothblueshiftedandredshiftedcomponents.Thesystemicve-
TheinspectionoftheESPRESSOechellespectrumofthecentral
locity,asderivedfromtheESPRESSOdata,is36.4kms−1,which
region of PC22 reveals a notable number of emission lines that
isconsistentwiththatderivedfromtheMESdata.
presentblueandredcomponents(Fig.8).Thesecanbeinterpreted
Theexpansionvelocitiesaredifferentfordifferentlines.We
astheapproachingandrecedingwallsofthecentralstructuralcom-
notethatthereisatrendfortheexpansionvelocitytoincreaseas
ponent,respectively,andthereforetheyprovideinformationonits
theionizationpotentialofthespeciesincreases,asrevealedbythe
internalkinematics.AlistoftheselinesisreportedinTable3.The
linearfittothedata(Table4andFig.9).Sincespecieswithhigher
radialvelocitiesassociatedwitheachlinehasbeendeterminedby
ionizationpotentialareclosertotheCSPN,itmeansthereisaneg-
ativevelocitygradientasmaterialislocatedfurtherawayfromthe
2 Component#7,whichsuffersfromthepresenceofadjacentknotsthat CSPN.Thisistheso-called“Wilsoneffect”(Wilson1950),which
addvelocitycomponentsnotnecessarilyrelatedtothispartoftheshell,has describesthedecreaseofthelineseparation(orexpansionvelocity)
notbeentakenintoaccountinthisaverage. withanincreaseoftheionizationpotentialinPNe.
MNRAS000,1–??(2016)
PropertiesofPC22 7
[S II]λ(6716 + 6730)Å Hα λ6563Å [N II]λ(6548 + 6583)Å [S III]λ6312Å He I λ5874Å
2
1
0
ec) -1
arcs -2
Position ( V[Aexpr= II4I]1λ.741 k3m5Å/s V[eOxp =II3I]4λ.580 k0m7Å/s VHexep= I3I 9λ5.24 1k1mÅ/s VHexep= I3I 6λ6.15 6k0mÅ/s V[eAxpr= V3]7λ.760 k0m5Å/s
e 2
v
ati
Rel 1
0
-1
-2
Vexp=40.2 km/s Vexp=38.5 km/s Vexp=34.2 km/s Vexp=31.6 km/s Vexp=26.9 km/s
-50 0 50 -50 0 50 -50 0 50 -50 0 50 -50 0 50
Relative Velocity (km/s)
Figure8. Position-Velocity(PV)diagramsresultingoftheanalysisoftwelvewelldefinedemissionlinesfromtheESPRESSOechellespectraofPC22.All
linesshowasplitandthecorrespondingexpansionvelocitiesarequoted.ThePVsarearrangedintermsofincreasingpotentialionizationlevelsoastovisually
followthechangeinVexp.Wenoticethatthe[SII]and[NII]emissionlineshavebeenaddedtoincreasethesignal-to-noiseratio.AsfortheHeII(6560Å)
line,thedarkareaontherighthand-sidecorrespondstothemuchbrightercontiguousHαline.
the [N II] bright) are concentrated in the elliptical central part of
45
thenebulaandarespatiallyrelatedtothepassageoftheaforemen-
tionedoutflows.
• Themorpho-kinematicalmodelobtainedwithSHAPErevealsin-
formationonthedifferentstructuralcomponentsofPC22.Hence:
40
-Thede-projectedvelocitiesoftheoutflowsandbumpsarerather
large((cid:62)100kms−1)comparedtothatofthecentralellipticalre-
-1s) gion(∼30–60kms−1).
p (km 35 -Allthestructuressharesimilarinclinationaround100◦ (slightly
x lessforthestructures#1and#2inFig.7),i.e.,nearlyalltheejec-
e
V
tions can be considered as coplanar and close to the plane of the
sky.
30 -Thekinematicalagecalculationsarealsowellconsistentforall
theanalysedoutflowswithameanof3600±1300yrs,butforstruc-
tures#1and#2,whichseemtobeslightly“younger"(2300±800
yrs).Thismayindicateeitherthatstructuralfeaturesattheelliptical
25
0 10 20 30 40 50 60 70 centralregionhavebeenaccelerated,orthattheoutflowsarebeen
Ionization potential (eV) slowed down (see, for instance, the ejecta in the born-again PNe
A30andA78,Fangetal.2014).Thisisatantalizingpossibility,
Figure9.GraphrenderofTable4withthereddottedlinerepresentingthe butatthismomentweconcludethatallejectionsinPC22should
linearfit.
beconsideredtobecoeval,owingtotheuncertaintiesontheage
calculation.
• TheESPRESSOechelledataobtainedfortwelveemissionlines
4 MAINFINDINGS presentingblue-andred-shiftedcomponentsallowedustoderive
theirexpansionvelocities.Thisvariesfrom26.9to42.5kms−1and
The main results of the morpho-kinematical study of PC22
tendstoabidebythe“Wilsoneffect”aswenotedadecreaseofthe
presentedherearethefollowing:
expansionvelocitywithanincreaseoftheionizationpotential.
• The PN, principally emitting in [O III], is not elliptical as pre-
viously stated, but multipolar with several sets of non-symmetric
5 DISCUSSIONANDCONCLUSION
outflowsshowingdifferentdegreesofbrightness,collimationand
ionization. Thecombinationofthemorphologicalandkinematicalanalysisin-
• Most(ifnotall)over-densityandlow-ionizationstructures(e.g., dicatesthatPC22belongstothecategoryofso-calledstarfishPNe
MNRAS000,1–??(2016)
8 L.Sabinetal.
atalateevolutionarystage.StarfishnebulaewereintroducedbySa- edgessupportfromCONACYT,CGCI,PRODEPandSEP(Mex-
hai(2000)todescribeHen2-47andM1-37,twoyoungPNeinves- ico).MAGacknowledgessupportofthegrantAYA2014-57280-P,
tigatedduringanHα imagingsurveywiththeHubbleSpaceTele- co-fundedwithFEDERfunds.SZacknowledgessupportfromthe
scope.Later,theproto-PNIRAS19024+0044(Sahaietal.2005) UNAM-ITEcollaborationagreement1500-479-3-V-04.Wethank
was added to this group. All three objects present the same mor- thedaytimeandnightsupportstaffattheOAN-SPMforfacilitat-
phologicalcharacteristics:theyshowmultiplewelldefinedandfast ingandhelpingobtainourobservationsespeciallytoMrGustavo
(∼100–200kms−1)collimatedlobeswithapproximatelythesame Melgoza-Kennedy, our telescope operator, for his assistance dur-
sizeswhichwouldindicatethattheyhaveemergedatthesametime ing observations, as well as the CATT for time allocation. This
andanequatorialwaistorring.OurclaimthatPC22isverylikely article is based upon observations carried out at the Observato-
anevolvedversionoftheaforementionednebulaeholdsinthefact rioAstronómicoNacionalontheSierraSanPedroMártir(OAN-
that: SPM),BajaCalifornia,México.Thedatapresentedherewereob-
tainedinpartwithALFOSC,whichisprovidedbytheInstitutode
(i) Thecontemporarylobeshavealargerextent(∼20–40(cid:48)(cid:48)),theyare
Astrofisica de Andalucia (IAA) under a joint agreement with the
fainterandshowlesscollimationinsomecases(seeAxis2).There-
University of Copenhagen and NOTSA. We acknowledge the In-
fore,thecompactnessoftheyoungstarfishnebulae(withoutflow
stitutodeAstrofisicadeCanariasfortheuseofthefilters.Thisre-
extentslessthan∼5(cid:48)(cid:48) inallcases)andtheirsharpnessoftheirlobes
searchhasmadeuseoftheNASA/IPACInfraredScienceArchive,
arelost.
whichisoperatedbytheJetPropulsionLaboratory,CaliforniaIn-
(ii) PC22 is a high-excitation PN, with dominant [O III] emission,
stituteofTechnology,undercontractwiththeNationalAeronautics
indicatingthatthecentralstarishotandthephotoionizationvery
andSpaceAdministration.Wehavealsousedarchivalobservations
efficient.Thisiscontrarytotheproto-PNeandyoungPNestarfish,
madewiththeNASA/ESAHubbleSpaceTelescope,andobtained
which were selected for the HST observing program HST-P6353
fromtheHubbleLegacyArchive,whichisacollaborationbetween
basedonthe(very)low[OIII]5007ÅtoHαlineratio,probingtheir
the Space Telescope Science Institute (STScI/NASA), the Space
“early”evolutionarystage.PC22wouldthereforejoinNGC6058
TelescopeEuropeanCoordinatingFacility(ST-ECF/ESA)andthe
(Guillén et al. 2013) in the very small group of evolved starfish
Canadian Astronomy Data Centre (CADC/NRC/CSA). IRAF is
PNe.
distributedbytheNationalOpticalAstronomyObservatory,which
This investigation opens a new door in the understanding of isoperatedbytheAssociationofUniversitiesforResearchinAs-
thehistoryformationandevolutionofsuchobjects.Themorphol- tronomy(AURA)underacooperativeagreementwiththeNational
ogyofPC22canbeexplainedbyafastandprobablyprimarilyuni- ScienceFoundation.
formwindfromtheAsymptoticGiantBranch(AGB)phasegoing
through irregular and inhomogeneous cavities from the previous
denser AGB shell. Steffen et al. (2013) studied this phenomenon
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ThispaperhasbeentypesetfromaTEX/LATEXfilepreparedbytheauthor.
APPENDIXA: OBSERVEDANDSYNTHETICSPECTRA
OFPC22
MNRAS000,1–??(2016)
10 L.Sabinetal.
FigureA1.Fromlefttoright:MES[OIII],[OIII]+contours,Hαand[OIII]lineSHAPEmodellingfortheslitsC(top)andH(bottom)
MNRAS000,1–??(2016)