1993ApJ...408L.105G THEAsTROPHYSICALJOUR.NAL,408:L105-L107, 91125. © nology, molecular mapped. emission (Zuckerman etary Graham metry molecular very 1,Germany. ponents; feature et ionized ionized in to the resolution nebulae ular bridges planetary also detected Webster 1980; 1993. 2 4 6 3 1 5 By The NGC be al. Cornell Division Palomar Alfred Astronomy Max-Planck outer become Tho lines striking, nebulae also contrast, the more Zuckerman 320-47, 1976). © (Graham American gas gas planetary the of shows iomzed en~ulf sations, neous. pa~ates 7027 Thi.s contrast Subject region, show of et P. sources The that et an American University, edge gas are Sloan Observatory, of H The nebulae. planetary al. is envelope (Beckwith, extended ~h~ir gap al. Pasadena, inner et increasingly Department, 2 It Physics closely Astronomical H loops (Mufson implies Institut is 1988; and ~triking imaging important al. that 1993). som~ We of is Research distributions II between located m headings: et while ~hrou.gh atomic of H; between region 1990). & shows shell now CO nebula the Ithaca, JAMES qualitatively contrast al. vibrationally around endorse Math the II Geballe, flir CA related Gatley Low-resolution than, of 1. nebulae (Bieging, Society. California The that regions. Persson, et and Astronomical H the 1993). similarities: University Fellow. Astronomic, of 91125. clear H of just the High-resolution INTRODUCTION gas NY lies that and the al. clear, the 2 II R. tracers H planetary NGC NGC ISM: remnant All the H H young the emission the (Bachiller region; dense 1988; 1975), beyond 14853. 2 a in to Astronomy, GRAHAM, H 2 rights Burton, 2 and the clumpy of that The emission morphologies scenano Institute (Isaacman optical emission The since a II H H neutral & older of Wilner, H reserved. molecules different excited distribution cavity 6781 2 region 7027 of II Kiinigstuhl Gatley California, dense Webster 2 that an~ molecular outer H both MORPHOLOGY extended region of the a 1-0 2 the closely the nebulae & molecular 1993May10 of et nebulae 1 emission mapping Printed detached emission the California shows mm ' old that envelopes edge for at Isaacman 2 was Technology al. detection consists and CO Society H have ' loop molecular neutral S(l) & 1978; 3 1984; from the photodissoCiated 2 with Berkeley, in et T. - 1993). the wavelength 17, planetarie~ follows, is Received emission U.S.A. of mapping ofNGC Thronson the among of individual knot.s, al. H emission that center M. limb-brightened coincident of planetary D-6900 where the evolution Beckwith E. Institute that molecular four-fold 2 those outer envelope, is 1988). Storey of inner envelopes of H ' ' emission HERBST, 1991). of of SERABYN, Pasadena CA ionized the a 2 • 1993January5;accepted1993 knots. two traces w~ich planetary but of CO Heidelberg common emission these the (Treffers 7027 94720. Provided the of shell already edge of excited Higher OF a molec­ in can (BD It 1991; 1984; tends nebulae: plan­ com­ (1-0) large sym­ et Tech­ with of 4 ionized first and leaving ABSTRACT the has gas • are the can CA in In young 5 al. 6 YOUNG of of of envelope only a K. AND + L105 both young planetary an arcs be 30°3639, MATTHEWs, be general by evolved and the S. identified planetaries envelope. photodissociation phology planetary pagating (1993) detached of only izing dissociation 2 x 2 which has pumping strongly expansion H to relationship van Several Stutski survived & front. al. attributed clumps 200 the InSb were of nebulae BECKWITH 2 explained New The BD may planetary the planetary NGC Gatley 1993). ionized PLANETARY H and recently molecular CO 10 Dishoeck inch 2 NGC nebula dense source detector obtained The - find 22 the H + emission NASA be observations 1988; planetary, of CO February24 envelope, 2 authors is the 30°3639 2 cm is through 7027 with arc to telescope favor nebulae emission molecular neutral of detected G. 1988). H to core no similar extend 7027) attributed 4 stressed - kinematics, H passage if knots 2 front between nebulae nebula • in the from of 2 Sternberg shocks 5 NEUGEBAUER, evidence knots 2 1987; bright gas array. survive the and at embedded which excitation H Astrophysics with a H was By the 2 have region envelope photodissociation 2.09, to the races and well NEBULAE are molecular the II from in as using photodissociation emission. BD the evolution. of Dinerstein associated of contrast, gas region driven radii The observed [O BD interclump that 2. H a the a to molecular the H more central for BD is beyond relevance & 2 while 2.12, faint discussed + photodissociation OBSERVATIONS through planetary model, with , 1] a a entire identified II seeing +30°3639 of in photodissociation Dalgarno 30°3639 in 3.28 that shock 2 is photodissociation and + aea equipped camera (Beckwith into region B. planetary NGC nearly an optical We 2.17, inhomogeneous. sufficient 30°3639 envelope arguing for Tielens on star with are et T. µm and the planetary H envelope Data molecular the excitation at ofphotodissociation discuss the form. al. NGC 2 1990 SoIFER, nebulae the and about within 7027, has is with edge 1-0 2 PAH argue coextensive. the fronts 1989), halo. and neutral 1988; interclump that show et µm describes switched region column nebulae May is System contribution 2.21 expanded H S(l) Clumps 7027, al. the a in 2 of NGC twice nebula of inhomoge­ that emission, was the II front the has and are Genzel, photodissociation gas by 1980; that that front the partially 7 region conden­ µm envelope H with region. at When morphological context comparing Graham in generally interpretation. currently 2 depth Tielens in ~0 (e.g., those a 7027 on pro­ H the morphology both phase. The the with these with gas Zuckerman (Graham scenario the 1 to :1. a Harris, II are a H and Palomar Black the 58 to of regions leaving neutral Images photo­ have 2 a by young of (1993) NH dense et mor­ have been x pro­ /l.J../}., ion­ CO UV the the the al. 62 ;;:::: in & & et a 1993ApJ...408L.105G [Pl. for found centered continuum large. line strong, surements subtracted from emission. distance clearly distinct cannot H tional measuring the map with with neutral subtracted sion a elliptical extended ionized H H H Bry the there beam. blend size seconds and CO emission outer of 2.21 L106 H the this while neutral 1992). ~ diameter 2 2 Comparison The To 1.3% The II Figure BD II Figure II the emission 1-0 extended H ionized exceeding region planetary (1-0), LlO]). region. or surface µm NGC the region brightness to of the Therefore, is shell emphasize the of by II + Bry H shows noise, i.e., show gas. S(l) continuum H envelopes envelope a from circular Masson settings observations beyond the of region 30°3639 2 H area from on 2.17 H limb-brightened 2 1 Beckwith Within close 1 © image (2-1), of of 2.17 the in 4" 7027 of 2 The from for line in II between The emission flux (Dinerstein gas. compares brightness east, measured in the component, American and H both Beckwith this from region most µm an 12". of the H H that nebula and BD 2 of µm spatial to enhancements emission image are in 2.21 2 this the and 2 4. emission 8" and BD variable (1989b). line central is arc and the of setting the directly 1-0 He flux the that beyond H Neither cases. a a the of unreliable + emission wavelengths, THE planetary free x et therefore edge BD line is 2.09 5" radius of II µm shows emission, 30°3639 Na on-line + ofGeballe NGC the H in I, current S(l) reaches 12". al. central within the prominent, extend association region. cannot beam, 30°3639 et is H of & but NEUTRAL flux II covers star + data 3. I BD of rather their (1978). and is H 2 At filter. is 2.1218 arcs because bright al. Astronomical unreliable Thus, of D the region Sneden 30°3639 H emission of 7027 aligned RESULTS II virtually the that only forms is 2 2.12 these (1978) images an observations accounts within is and nebulae star. data unfortunately region. significantly significantly 2.21 at + a The to morphology accurate. of 10" edge the be Bry H The that than et and 30°3639 annulus a emission This both are least µm and more H the H µm the find II but straightforward al. made diameter Fainter 2.09 ENVELOPE the an features of 1988; with µm. is equivalent 2 at along 2 suggests region, the that the similar of 2.12 and NGC 1-0 identical where (1991) (see from The H north almost beyond is 2.1661 unbroken conclusion 2.12 the planetary 6". mapped there 34% continuum for 2 µm Consequently, the accurate molecular H the therefore , between by Bachiller He is S(l) extends This µm CO the lines. brightest free-free Fig. emission the beyond beyond II that µm is 7027 ~ detached off-line forming of who and H because beam suffers of is single the Society 1 interpolating region. µm. that twice major 70% present emission, 3 setting the and the a H width to P- result II image 1). BD to the elliptical ridge continuum south measured nebulae are II The is region, 3 the 1':5 flux most comes continuum­ date, edge subtraction This due S2.114 implication several envelope beam the et the the region. continuum of from that image part size extends consistent axis +30°3639 However, a they therefore of from confirms 2.09 al. at includes and 15 the of traces roughly in GRAHAM edge ionized edge (Fig. • the to with of of image where Bry of of either of of emis­ addi­ a GHz 1991, mea­ from have have shell Provided at flux was and µm, 10", line We the the 10" the the the the the the arc H the to of of of is is 1, a a a 2 ET NGC directions mass nation surface simply observed ence forms a form, detected et is gas tion tion may the marked: region. neutral brightness peak between NGC sponding asymmetric asymmetry 7027, CO(l-0) asymmetry central of cal BD Bachiller the make s- () strength and and consistent BD BD therefore UV respectively. relationship peak, [Draine sion; T 1988; 11':5 = up Graham The The The Molecular al. = by 1 H parameters (Beckwith east Na AL. cm- intensity 6", + BD arise in + 2 140,000 to T loss + Na and arises and 1988; dereddened, 7027 Heap this the being a 6781 the 30°3639 distribution 30°3639 emission by x east-west because 30°3639 star the = The material a I distinct brightness, 5. assuming side. 21cmH1 3" in 2 1 D far-UV the 1978]) + et 23" factor resonance asymmetry distribution it and region the 25,000 because conclusion planetaries the sr- photodissociation with: to UV where NASA to 30°3639 and et both data (Beckwith al. is Zuckerman & is because, luminosity is than much H between surface eastern and the beam central emission The BD K a 1 H al. et likely Hintzen present 2 1989, EXCITED (2-1) which is unexpected, photodissociation and/ is there 5" of bright 2 the morphology at 4" in may al. planetary (Masson east on that (1993) x asymmetry the that surface K, also + 2 H the west the molecular emission; brighter (912 of = a the () (R.A. east evolved 1978; CO is the Astrophysics weaker 30°3639 1993). D brightness 2 that lobe star molecular 1 lines (Taylor, is = the compared determine more while 3.8 is H the _ from emission distance that material very of et reflect in patch. 1990; circumstellar column due from 05 lines almost and of 4", 2 western >)./A> less have and et H2 of al. NGC is CO, emission < x the brightness the x 1 H Zuckerman is 1 the 1989a, al. nebulae (Bachiller > have a the assuming quantitative similar: the 10 Deel.). to EMISSION than to for given temperature 1978; = material ;<:: H nebulae (Dinerstein is seemingly Kaler the BD The extended distribution attributed in of Gussie, will central 4 emission 1990). H an gas 4 2 a 1.7 the progenitor. certainly in the coincides to 7027. (in of gas central kinematics; 2 the side density NGC times BD H to been bulk photodissociation at , 1108) the east-west + region. the asymmetric and Zuckerman b; x in 2 the east occur However, units density only 880 & are density. the H 30°3639 BD I (Graham It envelope. and of 10- 1 Data BD outer in + such The star, & Jacoby 2 west Underhill a of et _ IN & observed brighter the is similar surface symmetry equivalent 0 halo the unlikely 7027 30°3639 extends star, than distance we Pottasch that pc, planetary which the due of so> Gatley & is 3 + al. BD with of field likely This Na + most eastern of ergs the Nonuniform 3.28 is 30°3639 the as H loops compare and Sneden asymmetry 30°3639 lowest. L the System H = L of is to 1991, direction. not and, light +30°3639 there to 1991). x II I Na = the NGC 2 et interpretation (see brightness-the & The interstellar is 1.6 = s- distribution detected H than = µm an D region. that morphological alternative. emission at 1988; the rapidly is are strength 1.3 the 1983; al. unresolved molecular, ofNGC 2 of 10 Gatley 1990). 1 2.3 eastern 1 D H positions at of x nebula scattered emission much asymmetric is low below), emission cm- asymmetry PAH 1992). 4 region. 1988). and 2 1993). Thus, west. 2.8 is large, x the the the 10- 6720 UV a positions x the emission emission L Webster Vol. nonuni­ 10 sugges­ is Similar Ioniza­ Jacoby surface illumi­ 0 10 2 kpc, differ­ physi­ corre­ in 3 along NGC 4 1988; emis­ more quite from sr- peak 7027 H with This 4 field field ergs The The The and L and and low the 408 the for To on or 0 in in in of in at is 1 II a , , 1993ApJ...408L.105G PLATE GRAHAM emission. of loops - 2.6 the ~ - ~ "C u rz1 0 <1 "C u rz1 <1 0 d 0 0 Q) rn M m 0 rn d 0 rn M m 0 0 Q) rn BD FIG peak x are 10- . .-'4 0 0 0 .-'4 .-'4 0 0 + !.-Line I of et 30 The pure 3 LlO ergs the ° al. 3639 2.12 H © (see emission s BD+30-H2 7027-H2 2 D - images • is µm 1 American Contours 408, cm 3.6 images - L106) in x 2 of BD of sr 10- the !::. - are 1 include 4 outer and RA ergs logarithmic, + 0 30 for Astronomical H s ° a - 3639 2 the contribution (arc 1 shell c Brix m- and . n starting In 2 image 0 sr- the NGC seconds) 1 Br from ofNGC and at y 7027 and 10 .• for He Society % Brix (top 12 NGC 7027 of .· . the 11 images, ..... and 4 µm 7027 peak . 6 bottom x within • o@ black 10 intensity 2.1 Provided - 2 , x the ergs respectively) corresponds -10 10- H , s- and 4 n ergs 1 region cm increasing 10 by s - - 2 to showing . 1 sr- See§ BD+30-HII the cm 7027-HII the 1 • - peak by 3 2 regarding NASA sr the x - emission 2 1 . distribution !::. • In The the RA the first Astrophysics in 2.12 accuracy the contour µm (arc of shell. H images 2 of The 1 for 0 0 - the 0 seconds) the the first S(l) continuum linear Br Data contour (left) y i m gray-scale and a ge subtraction. System for of Br the y BD and 2.12 maps + Bnx 30 The µm black ° 3639 -10 (right) image outer to is 1993ApJ...408L.105G --. Bachiller, Bachiller, Atherton, evolved Geballe, Graham, Genzel, Beckwith, Dinerstein, Draine, Dyson, Black, Bieging, Balick, Bachiller, Dinerstein, Beckwith, strong evolved etary contain condensations gas Forveille, ments the molecular shows (Graham are Jaminet that vived populated formed of cm- absence ary density comparable dissociation line theoretical the knots molecular region rounded No. strength 7027. at BD BD BD BD 6. A&A, 231 Phillips, Astronomy, 625 Soifer, 1980,AJ,85,886 There If The the the CLUMPY density bright association is nebulae of 2, + 3 these + + + J. nebulae , B., from J.E., observed (nH B. we 1993, (Forveille clumpy-so J. H., 30°3639 218, that photodissociation T. H., 30°3639 BD R., 30°3639 © (the ultraviolet 30°3639 H respectively 1993 B. T., J. R., component R., small P. planetaries. R., S., Gonzalez, by T. S., et of J.P. is planetary R., by H. H. 2 T., 2 et & implies R., American Harris, D., & condensations 252 Persson, Huggins, Hartquist, 1978, (Reay, Bujarrabal, in al. ~ Neugebauer, and A&A, substantial Huggins, a Wilner, (i.e., gas + scaling assume L., L., inner ed. the van ionization Burton, the in al. Wilson, a Huggins, 1979, PHOTODISSOCIA is strong Serabyn, Hicks, front 30°3639 10 to [O photodissociation 1991). optical & Lester, is B. the 1993). Dishoeck, ApJS, are is good molecular CO earliest phases earliest 6 H that may is Sneden, 276, and clumpy. n of H. G., A. & ApJ, that cm 1] D., ring half S. 2 OF Walton, P. radiation ~ M. molecular T. a T. inhomogeneous, Kaldeich P. law detected H T. Huggins brightness that and I., Frank, E., nebulae, D. T. 177 (Mass9n emission. (nH self-absorption observations J., On 36, & V., D., ncrit(2-1) - is E., G., R., NGC be 232, J., that evidence 2 FAINT condensations W., UV-excited G., suggests & & that 3 1991, Cox, F., Thronson, of evidence C. of in 595 ) 2 26% of and & Martin-Pintado, E. Astronomical Reay, Martin-Pintado, & Herbst, Gatley, the about it that are Stutski, ~ Carr, For 786 Pettini, Becklin, 1988, H Beckwith, A., front are F. Isaacrnan, the Sternberg gas P., (ESA NGC can A&A, in & 2 3 x 3 the 7027 other 1987, , & field-it CO OPTICAL in 1991). lower knots N. eventually & example, such TION survive gas J. cold NGC ApJ, Atherton 1989b). = Jacoby, neutral Dyson and is I. T. that Forveille, that S., of survive H. SP-290), a K., (the H M., 10 J. 248, that H E. 1978, region. x 3 ApJ, fragmented emission M., molecular factor adjacent & 2 A. 335, are S. 4 mass hand of 7027 2 Robinson, 1988, dense E., R. morphology & H as REGIONS In adjacent than emission Harvey, cm- 599 1993, feature 7027, the BD 1991, outer (1988). MORPHOLOGY within 322, G. consisting ApJ, NGC the 1991, 2 Smith, Matthews, 10 is the Matthews, J., L23 et J., fact 2.6 Since envelope, HALOS NGC 115 many T.1991, 4 1992, in in very surface & the loss. J 1988). & 412 of (nH al. 3 AJ, molecular engulfed ApJ, + 219, clumps NGC passage cm- ) MNRAS, Gomez-Gonzalez, = then Society Infrared x molecular P. unless H Cox, L. with which 30°3639 to G. 7027 2 electron 2 (1989) the 105, in ApJ, Thus 10 1 difficult 2 M. L33 to the 379, into In J. 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Walsh 30°3639 H fact extends 7027 1988, evolution to 356, al. emission responsible some the 14 these the Nebulae, NGC 2 apparently the have 209, 615 increasing likely extending will to the 1 twice although envelope 6543 1979]). 1-0 7027 that L59 only MNRAS, km from ionized planet­ photo­ molec­ has There­ permit 793 of knots. dilute of 1989; reach plan­ suffi­ L107 rem­ 7027 halo The to that and S(l) this s - the the the the an ed. or in in of of a a i