arXiv:astro-ph/9904202v1 15 Apr 1999 hr r ayeiso ie rsn nte1–2.5 recombination – to H 1 due of the those in notably lines present most emission. lines region, the emission spectral for many responsible are in examined processes There conditions be the must physical objects understand the these to of re- about spectra imaging more the the nebulae, learn interpret the to to order and as In sults important, I. is Paper in PNe described of characteristics the (near-IR) present infrared we survey. spectral here near-infrared pre- survey; a I) of imaging Paper results hereafter infrared 1995; an al. et sented (Latter paper first The Pe sosre ntena-nrrd( near-infrared nebulae the planetary in of observed properties as the (PNe) examining surveys of umte oteA.J up eis2 e 98 cetd4Ap 4 Accepted 1998, Dec 21 L Series using Supp. typeset J. Preprint Ap. the to Submitted rsn r tmclnso He of lines atomic are present yosrigteotclln msin oePeas ex- also PNe Some emission. line seen optical and is the than regions observing excitation by different and density, con- sampling temperature, physical of the nebula, ranges probe the to inside tools diagnostic ditions as act can lines rmohrmlclrseissc sC n C and CO as such species molecular other from hr r eea esn h nweg ftenear- the of knowledge why reasons several are There hsi h eodo w aesdsrbn h results the describing papers two of second the is This bevd rmtena-nrrdsetu,w eemnda o an excitation dominant determined the we and spectrum, temperatures, excitation near-infrared vibrational the From observed. sn h H the using Oeiso,adwr utcniumeiso oad h ogwave long the towards emission continuum dust warm and emission, CO sanblrdansi n oorudrtnigo N structure PNe of understanding our headings: to Subject and diagnostic nebular a as id n htn oteectto fH of excitation the to photons and winds bevtoswr banda n rmr oiin nte4 objec 41 H the in categories: general discre positions four sampled more of one which or into used one fall was spectra at slit obtained narrow were A observations (PNe). nebulae planetary uvyd n nxetdrsl rmti nlssi htteH the that is analysis this from result unexpected One surveyed. htn nms ftePesree,atog o eea N no in b PNe correlation The several for role. important although an surveyed, plays PNe shocks the velocity of moderate most in photons msinhsbe teghndwt h e eetoso H of detections new the with strengthened been has emission etrswr bevdi l aeois uha otnu emiss continuum objects as C-rich such the categories, and all group in first observed the were into features falling generally objects opooia ye ihteelpia N aln notefis group, first the into falling PNe H elliptical the the with type, morphological N,H PNe, oeua yrgnwsdtce o h rttm nfu N.A e An PNe. four in time first the for detected was hydrogen Molecular epeetmdu-eouin(R medium-resolution present We I n ie fvbainlyectdH excited vibrationally of lines and , srnm eatet otnUiest,75Commonwealt 725 University, Boston Department, Astronomy NETGTN H ERIFAE RPRISO LNTR N PLANETARY OF PROPERTIES NEAR-INFRARED THE INVESTIGATING 2 2 n otnu msingop.Tectgre locreaewt C with correlate also categories The groups. emission continuum and IT cec etrIfae rcsigadAayi Cen Analysis and Processing Center/Infrared Science SIRTF avr-mtsna etrfrAtohsc,6 adnSt Garden 60 Astrophysics, for Center Harvard-Smithsonian msinln-oiae N,adcniumdmntdPe hs c These PNe. continuum-dominated and PNe, line-dominated emission A 1. T 2 E tl mltajv 04/03/99 v. emulateapj style X ierto o l fteP pcr ntesre hr ucetnu sufficient a where survey the in spectra PN the of all for ratios line INTRODUCTION otnu nrrd S:lnsadbns–mlclrprocesses molecular – bands and lines ISM: infrared: – continuum lntr eua:gnrl–IM oeue S:srcue–inf – structure ISM: – molecules ISM: – general nebulae: planetary umte oteA.J up eis2 e 98 cetd4Ap 4 Accepted 1998, Dec 21 Series Supp. J. Ap. the to Submitted I n [Fe and 1-,Psdn,C 12;[email protected] 91125; CA Pasadena, 310-6, I EIMRSLTO SPECTRA RESOLUTION MEDIUM II. λ II ,ademission and ], 1 = ∼ − 2 2 0)na-nrrd( near-infrared 700) These . 2 . 2 ila .Latter B. William 5 Also . [email protected] yn .Deutsch K. Lynne nPe n osdrsm mlctost h tlt fH of utility the to implications some consider and PNe, in oehL Hora L. Joseph µ ABSTRACT 1999 r m). µ m I msinln-oiae N,H PNe, line-dominated emission 1 ain fPei h erI.Hink wk Geballe & Kwok, Hrivnak, near-IR. the in PNe and of vations PNe new 1990). identify most al. to et of used (Garcia-Lario be characteristics objects can color post-AGB the and from near-IR unique emission are The PNe line & pri- itself. ther- thermal continuum, the and nebula stellar emission, be determined years dust to 1987) emission following mal IR al. ex- the of et sources was in mary Persi what surveys 1985; over photometric (Whitelock emission Other that central the IR determined from star. emission of 1974) continuum reflected excess Barlow from pected & an was Cohen Merrill, spec- there Gillett, 1972; Early (e.g., Stein infrared. surveys the & photometric in and PNe of troscopic are properties that the nebula plored the of regions allows into dust. wavelengths by optical see the obscured to potentially of compared to depth as us optical IR lower the continuum in the and PNe Finally, line between sources. differentiate emission to and it detect µ ii ntena-Rsrn otnu msinfo hot of longward from significant emission becomes continuum emission strong This near-IR dust. the in hibit nmn ftePe eurn erI pcrsoyto spectroscopy near-IR requiring PNe, the of many in m eetyteehv enmr ealdseta obser- spectral detailed more been have there Recently ex- have that surveys previous several been have There vne otn A025 [email protected] 02215; MA Boston, Avenue, h e,Clfri nttt fTcnlg,MS Technology, of Institute California ter, etM/5 abig,M 02138-1516; MA Cambridge, MS/65, reet λ 2 1 = 2 nti uvy edsusterl of role the discuss We survey. this in o rmtecnrlsa,C star, central the from ion ehns fteH the of mechanism tot-aarto h oainland rotational the ratio, rtho-to-para sectdb bopino ultraviolet of absorption by excited is n evolution. and nteohrgop.Ohrspectral Other groups. other the in tenbplrmrhlg n H and morphology bipolar etween − sicue ntesre.TePN The survey. the in included ts rsre olsoa xiainin excitation collisional survey ur n h ioa N rmrl in primarily PNe bipolar the and ctto nlsswsperformed was analysis xcitation 2 elctoswti h nebulae; the within locations te . eghedo h spectra. the of end length 5 µ )setao apeof sample a of spectra m) Orto ihteO-rich the with ratio, /O 1999 r tgre orlt with correlate ategories I n H and bro ie were lines of mber ae:ISM: rared: 2 o ayobjects many for EBULAE 2 msinline emission 2 N and CN, , 2 2 λ 2 = 2 Near-IR PN Spectral Survey

(1994) surveyed a set of proto-PNe in the H and K bands. telescope background flux. Dome flats were used to cor- In these objects the H I Brackett lines were observed in ab- rect for pixel-to-pixel gain variations in the array. Stars of sorption, and most objects had CO absorption or emission, known spectral type (either G0 or A0) were observed at indicating recent mass loss events. Rudy et al. (1992, and the same airmass as the nebulae immediately before and references therein) and Kelly & Latter (1995) have sur- after the PNe observations and were used for correction of veyed several PNe and proto-PNe in the λ =0.5 − 1.3 µm the instrumental response and sky transmission. Individ- range. Dinerstein & Crawford (1998) have completed a ual lines were removed from the stellar spectra, and then survey of a set of PNe in the K-band, focusing on excita- normalized using a blackbody function of T = 5920 K for tion of molecular hydrogen. the G0 stars and T = 10800 K for the A0 standards. The There are several unique aspects of the survey re- spectra were wavelength-calibrated using observations of sults presented here that were made possible by the an Argon reference lamp. The wavelength values used for KSPEC spectrograph (see the instrument description be- lines greater than 1.1 µm are from Rao et al. (1966); for low). First, because of KSPEC’s high sensitivity and lines less than 1.1 µm, the wavelengths were taken from simultaneous sampling of the full near-infrared spectral Wiese, Smith, & Miles (1969) and corrected to vacuum range, we were able to obtain data on a comparatively wavelengths. The average 1σ uncertainty in the measured large number of objects (41) in a short period of time. wavelengths of the lines is about 5 A.˚ Using the relatively narrow and short slit of the spectro- Infrared photometric standard stars were observed in graph, we sampled different regions of the PNe to examine the same way as the PNe and used to flux calibrate the the emission throughout the nebula. In most of the other spectra. Absolute calibration is difficult with these spec- surveys described above, larger beams were used that in- tra because not all of the flux from the star enters the cluded much or all of the object. Another aspect of the narrow slit during a single integration, and the amount data presented here is because of the cross-dispersed de- differs for each integration depending on how well the star sign of the instrument, the entire λ =1.1 − 2.5 µm range is centered on the slit (the seeing at 2 µm during typi- is obtained at once, eliminating the possibility of telescope cal observations was 0′′. 5–1′′. 0). The amount of light lost pointing errors or other fluctuations affecting the relative was estimated by the following method: the full width at line strengths in the spectra. Finally, the slit-viewing de- half maximum (FWHM) brightness of the standard star tector allowed precise positioning and guiding, so the re- was measured along the spatial direction of the slit, in the gion of the PN being observed was well known for each spectrum with maximum flux for that star. It was then spectrum. The PNe observed in this survey were chosen to assumed that the point spread function (PSF) is well rep- overlap with the near-IR imaging survey (Paper I), along resented by a two-dimensional Gaussian distribution with with several other optically-bright PNe and unresolved ob- the measured FWHM, and the amount of flux falling out- jects that were not included in the imaging survey. side of the slit was then calculated. This was typically 20 – 30% of the total light for a single integration. The calibra- 2. OBSERVATIONS AND DATA REDUCTION tion for each star was corrected by this factor, along with The observations were performed on several runs during corrections for airmass. Comparing results from different the period 1992 October through 1994 September at the standard stars taken throughout the night indicated that University of Hawaii 2.2m telescope on Mauna Kea, using this method is accurate to approximately 20%. For the the near-IR KSPEC spectrograph (Hodapp et al. 1994). observations of the PNe, no correction was applied for the KSPEC is a λ =1 − 2.5 µm cross-dispersed spectrograph slit width or length. The length along the slit of the ex- ′′ ′′ that has a separate slit-viewing IR array for acquiring the tracted regions for the three bands were 2. 0 (J), 3. 5 (H), ′′ source and guiding. The full spectral range is obtained in a and 4. 0 (K). single exposure, resulting in accurate relative line measure- 3. ments and highly efficient data acquisition. The diffraction RESULTS orders are well-matched to the atmospheric transmission The spectra are presented in Figures 1 – 32. One to windows, with the K band in 3rd order (1.9 – 2.5 µm), H three PNe spectra are plotted in each figure. Tables 2 in 4th order (1.45 – 1.8 µm) and J in 5th order (1.15 – through 7 list the line identifications and extracted fluxes 1.32 µm), with a resolution R ∼ 700. The 1×6 arcsecond with uncertainties for the spectra shown in the Figures. slit provides a small aperture that was used to sample dif- The PN in this section are listed in Tables 2, 3, and 4. ferent spatial regions of the nebula to search for spectral There are a number of features not identified (indicated variations. by question marks in the tables). These features tend to Table 1 lists the nebulae observed and details of the appear above the ∼ 3σ level and must be considered real, observations. Integration times for each exposure ranged though confirming spectra would be valuable. Our search from a few seconds for the extremely bright sources to 5 for possible identifications for these lines has been careful, minutes for faint sources. The off-axis guider was used but perhaps not exhaustive. In addition to the relatively to keep a consistent on-source slit position. Multiple low S/N of these lines, the moderate wavelength resolu- “Fowler” sampling was used to reduce the read noise. The tion is not sufficient to differentiate between the several number of samples for a particular integration ranged from possible identifications for each line. 4 to 16, with more samples used for the longer integration The PNe spectra are separated into four groups that times. The spectra were reduced using IRAF; the extrac- share common characteristics. These are H I recombina- tion and processing of the spectral data were done us- tion line-dominated, H I recombination line + H2 emission, ing the functions in the noao.twodspec and noao.onedspec H2 – dominated, and continuum-dominated. A fifth group packages. Alternating source and sky integrations of the of objects is included that contains two objects that were same length were taken and differenced to remove sky and at one time classified as PNe, but are now generally re- Hora, Latter, & Deutsch 3 garded as being H II regions (M 1–78 and K 4–45; Acker centered on the ring directly east (E) of the central star. et al. 1992). We do not discuss these objects further, but The dominant emission lines are those of atomic hydrogen. include them for comparison. Within each group, the NGC objects are listed first, followed by the remaining PNe in 3.1.3. NGC 2392 alphanumeric order. The morphological classifications are The PN NGC 2392 (the “Eskimo nebula”) is another given according to Balick (1987), unless otherwise noted. double-shell nebula; however, this PN has a significant amount of structure in the inner ring and outer shell. I 3.1. H - line dominated Spectrophotometric (Barker 1991) and kinematic studies The line emission in these PNe is dominated by lines of (Reay, Atherton, & Taylor 1983; O’Dell, Weiner, & Chu H I and He I. In the J-band, the Paschen β (Paβ) line is the 1990) that have been carried out with optical imaging and most intense, with contributions from lines of He I, [Fe II], spectroscopy have revealed the abundances and ionization and O I. In the H band, the Brackett series of H I dom- states and velocities of the various components. Near-IR inate, with He I emission at 1.7002 µm and [Fe II] emis- images of this PN were presented in Paper I. sion at 1.6440 µm present in some PNe. In the K band, The spectrum of NGC 2392 in Figure 1 was taken cen- the brightest line is usually Brackett γ (Brγ), with strong tered on the brightest part of the ring directly E of the lines of He I at 2.058 and 2.112 µm. When the H I lines central star. This third early-type round PN differs from are strong enough, one begins to see the Pfund series lines the other two in Figure 1 primarily from the bright He I starting near 2.35 µm where they are just beginning to be line at 2.058 µm, and the [Fe II] lines in the J and H bands separated at this resolution. There are also two uniden- of the spectrum. tified lines at 2.199 and 2.287 µm (Geballe et al. 1991) that appear in several PNe in this category. A few of the 3.1.4. NGC 3242 spectra shown here have contributions from central star NGC 3242 is an early elliptical with several interesting continuum flux that is larger towards shorter wavelengths, morphological features. In addition to the bright elliptical or warm dust continuum which is stronger at longer wave- ring, there are several filaments and knots of emission in lengths. the central region, and two ansae that are placed roughly along the major axis of the elliptical emission. Also, there 3.1.1. NGC 1535 is a larger faint halo that envelopes the inner structure. NGC 1535 is classified as early round, and its near-IR Spectra acquired at three different positions on the neb- spectrum is dominated by emission lines of H I. It has a ula are shown in Figure 2, on the SE knot (NGC 3242SE), bright ionized shell of emission which is surrounded by a on the E section of the bright ring (NGC 3242E), and on fainter halo (e.g., see Schwarz, Corradi, & Melnick 1992). the SW halo (NGC 3242H). The spectra are similar in all Near-IR images were presented in Paper I. This PN has locations; the bright H I lines are present in all positions, previously been observed to have H2 lines in absorption along with stellar continuum at the shorter wavelengths. in the far-UV (Bowers et al. 1995). Recent observations One difference is that the He II line at 2.189 µm are much by Luhman et al. (1997) failed to detect H2 in emission brighter in the E ring than in the SE knot or halo position. in the v = 1 → 0 S(1) line. They attributed the earlier detection of absorption at shorter wavelengths to the in- 3.1.5. NGC 6210 terstellar medium, or a region in the PN itself of a much NGC 6210 is a fairly compact PN with a core – halo smaller size than the ionized zone. morphology similar to other ellipticals. Phillips & Cuesta The spectrum of NGC 1535 shown in Figure 1 was ob- (1996) performed a visible wavelength spectroscopic study tained at a position centered on the brightest part of the that revealed a complex velocity structure which suggests ring directly west (W) of the central star. We also fail to multiple shells and possibly “jets” at various position an- detect the H2 emission in the v = 1 → 0 S(1) line, at a gles. The near-IR image presented in Paper I does not 1 σ level of about 5 × 10−17 ergs cm−2 s−1 A˚−1. There reveal much of the structure. This PN is one of several in is some indication of emission from H2 in the v = 1 → 0 which Geballe et al. (1991) detected unidentified emission Q(1) and v =1 → 0 Q(3) lines at the long wavelength end at 2.286 µm (but not at 2.199 µm). of the spectrum. However, the spectrum is noisier in this Three spectra are presented for this PN, and shown in region and there is confusion with the Pfund-series H I Figure 3. They were acquired with the slit centered on ′′ ′′ lines, therefore the H2 lines are not detected above the 3 the core (Core), 1 east (E1), and 3 east (E3). The core σ level. position shows a contribution from stellar continuum in the λ = 1 − 1.8 µm region that decreases successively in 3.1.2. NGC 2022 the E1 and E3 positions. The unidentified feature at 2.287 NGC 2022 is an early elliptical PN, but is morpholog- µm is detected at the E1 position, but not the 2.199 line, ically very similar to NGC 1535 in optical images (e.g., similar to the findings of Geballe et al. (1991). Schwarz et al. 1992). The main difference between the two is a different relative outer halo size as compared to 3.1.6. NGC 6543 the inner ring (the halo is relatively smaller in NGC 2022). NGC 6543 (the “Cat’s Eye”) has a complex morphology, Zhang & Kwok (1998) also find similar parameters with with a high degree of symmetry. Recent HST imaging their morphological fits of these two PNe. Near-IR images (Harrington & Borkowski 1994) has shown more clearly of this PN were presented in Paper I. the structure of rings, shock fronts, jets, and fast, low- NGC 2022 is also spectrally similar to NGC 1535, as ionization emission-line regions (FLIERS) present in this seen in Figure 1. The spectrum of NGC 2022 was taken PN. 4 Near-IR PN Spectral Survey

The spectrum shown in Figure 4 was taken at the po- SW Lobe was taken on the inner bright ring directly SW sition S of the central star and slightly E, where the two of the central star. The SW Halo position was taken in the emission arcs cross and create a local emission maximum halo midway between the bright ring and the outer edge (see Paper I, Figure 6a). The spectra is similar to the of the PN. The lobe and halo emission is similar, except other PN in the H I/He I - dominated class, and also show for relatively brighter lines of He I at 1.7002 µm in the the unidentified lines at 2.199 and 2.286 µm. lobe. There is also some continuum emission at the short wavelength end of the nebular positions, which is probably 3.1.7. NGC 6572 scattered light from the central star. This young PN has a bipolar morphology in the near-IR, with its major axis in the N-S direction, and a bright ring 3.1.11. NGC 7009 structure closer to the central star (Paper I). The near-IR NGC 7009 (the “Saturn” nebula) is an elliptical with an spectrum from 0.77 to 1.33 µm was measured by Rudy et interesting twisted symmetry in its shell and in the vari- al. (1991), and the UV and optical spectrum was recently ous filaments and knots of emission. Balick et al. (1998) obtained by Hyung, Aller, & Feibelman (1994), who found recently published HST images that show the “microstruc- evidence of variability. tures” in this PN. The images show that the inner knots Figure 5 shows two slit positions on the PN, one on the are actually groups of FLIERs, and jets in [N II] are seen nebula center, and one on the brightest location in the E that terminate at the tips of the nebula. lobe of the PN. Both the core and E lobe spectra show a Two positions were sampled, one in the halo region on strong contribution from stellar continuum flux. There is the W edge of the PN, and one in the N part of the nebula. strong H I and He I line emission, and relatively strong Both positions show a stellar continuum emission contri- unidentified line emission at 2.199 and 2.286 µm. bution from the central star. The halo emission is similar to the spectrum taken on the north edge of the PN. 3.1.8. NGC 6790 This PN has been shown by radio continuum observa- 3.1.12. NGC 7662 tions to be an elliptically-shaped nebula with a diameter NGC 7662 is a triple-shell elliptical, with a bright inner of roughly an arcsecond (Aaquist & Kwok 1990). Aller, ring, a fainter outer shell, and a very faint nearly circular Hyung, & Feibelman (1996) obtained UV and optical spec- halo (Hyung & Aller 1997). This PN also has a large num- tra and suggest that NGC 6790 is a relatively young object, ber of complex microstructures, recently examined using slightly more evolved than Hb 12. Kelly & Latter (1995) HST imaging by Balick et al. (1998). They suggest that obtained a 0.9 – 1.3 µm spectrum and find similarities to there is a prolate elliptical bubble around the central star Hb 12 and AFGL 618. aligned perpendicular to the bright ring. The bright ring The spectrum of NGC 6790 in Figure 4 shows a stellar is interpreted as a torus seen at roughly 30◦ inclination. contribution because the slit was centered on the object, The spectrum shown in Figure 9 was taken on the bright and includes the star as well as the nebular emission that ring directly SE of the central star. The N end of the slit is typical of this class of PN. was near the central star, so some stellar continuum is seen in the spectrum, which is otherwise dominated by H I and 3.1.9. NGC 6803 He I lines. This compact elliptical PN has a uniformly bright disk with no apparent structure in the optical, and is sur- 3.1.13. IC 351 rounded by a fainter halo about twice the size of the bright This compact PN has a double-lobed structure with a shell (Schwarz et al. 1992). In the KSPEC imaging chan- round halo (Hua & Grundseth 1986; Aaquist & Kwok nel, however, the PN was seen to be double-lobed, with 1990; Manchado et al. 1996). Feibelman, Hyung, & Aller the lobes on the minor axis of the bright elliptical region. (1996) obtained UV and visible light spectra of IC 351 Spectra were obtained at two positions, one centered on that show it to be a high excitation nebula, but without the E lobe, and the other position 5 arcseconds NW in the the presence of the usual silicon lines, and suggest that the halo region. The lobe spectrum shows bright H I and He I silicon atoms could be locked up in grains. lines, with a stellar continuum contribution out to about Our spectrum (Figure 9) taken centered on the PN suf- 1.5 µm. There is also unidentified line emission at 2.286 fers somewhat from an incomplete subtraction of OH air- µm. The halo spectrum is quite different, with weak Paβ glow lines, due to the sky frames not being taken properly and continuum emission, and is probably reflected star and for the on-source images. The OH lines show up in emis- nebular emission. sion mainly in the H and K-band portions of the spectrum. However, the major features of H I and He I emission lines 3.1.10. NGC 6826 can be seen. This elliptical PN is morphologically similar to NGC 3242, with a bright elliptical inner ionized ring, ansae along 3.1.14. IC 418 the major axis, and a fainter halo that envelopes the sys- The spectrum of this well-studied young, low-excitation tem (Balick 1987). The I-band image in Paper I shows PN was previously shown to be dominated by lines of H I evidence for a shell between the inner bright ring and the and He I in the near-IR, with a hot dust continuum (Will- outer halo, and at the same radial distance as the ansae. ner et al. 1979; Zhang & Kwok 1992; Hodapp et al. 1994). The spectra are shown in Figure 7. The bright core is Hora et al. (1993) and Paper I showed broad- and narrow- dominated by stellar continuum emission. The other posi- band near-IR images of the PN, showing the elliptical, tions show strong H I line emission. The spectrum labeled double-lobed structure in the IR. Hora, Latter, & Deutsch 5

Three positions in the nebula were observed to deter- from warm (∼ 200 K) dust that has a similar morphology mine the spectral variations across the object. The posi- but the position angle of the dust emission maxima is or- tions observed were on the central star, the peak of the E thogonal to those shown in Hα emission. The spectrum of lobe, and in the E halo region outside of the bright ring the core of this PN shown in Figure 14 has strong stellar (Figure 10). In the central position, stellar continuum is continuum, as well as H I and He I line emission. The visible, rising towards shorter wavelengths. The nebular slit was positioned N-S across the compact ring of the PN, lines are similar in the central and lobe positions. The halo so the ionized regions of the nebula are included in this emission is almost devoid of lines; there is some faint Paβ spectrum. present as well as Brγ. This is possibly reflected from the bright lobes. The main component of the halo emission is 3.2. H I - line and H2 emission a weak continuum that rises toward longer wavelengths. The emission lines present in the spectra of this PNe 3.1.15. IC 2149 group contain those mentioned in the previous section plus lines of molecular hydrogen. The H lines are strongest in This peculiar PN has a bright core and a roughly bipolar 2 the K band, although in some objects there are lines vis- nebula extending approximately E-W, but does not show ible in the H and J bands as well. In the objects where the usual H signature of bipolar PN. The two spectra 2 more than one slit position was measured, there is often shown in Figure 11 were taken centered on the bright cen- a large change in the relative line strength of H I versus tral star, and on the E lobe. The core spectrum shows H emission, indicating that the emission is being pro- strong stellar continuum, with the nebular lines superim- 2 duced in different regions of the nebula. In general, the posed. The E lobe emission is primarily from lines of H I H emission is more likely to be in the outer regions of and He I, in addition to weak continuum emission which 2 the PNe, whereas the H I emission lines more closely trace is probably reflected from the central star. the ionized regions and has similar morphology to the vis- 3.1.16. IC 3568 ible appearance. The PNe in this group all have some bipolar symmetry in their shape, most being of the “but- This round PN consists of spherical shells, an inner terfly” morphology characterized by narrow equatorial re- bright one and a outer halo. Balick et al. (1987) showed gions and large bipolar lobes (e.g., M 2–9, Hb 12). How- that the structure was consistent with simple hydrody- ever, some are classified as elliptical based on the shape namic models of PN that are shaped by interior stellar of the brightest components. Tables 5 and 6 list the line winds. The spectrum taken on the N edge of the PN is identifications and extracted fluxes for the PNe in this sec- shown in Figure 12. The predominant features are H I tion. and He I emission lines, and low level continuum emission which is probably reflected from the central star. 3.2.1. Molecular hydrogen excitation in PNe 3.1.17. IC 4593 A near-infrared H2 emission line spectrum can occur Bohigas & Olguin (1996) obtained spectroscopy and through slow electric quadrupole vibration-rotation tran- imaging of this PN which has two inner shells surrounded sitions in the ground electronic state. Because the allowed by an outer highly excited halo. IC 4593 is unusual in that transitions are such that Tex ∼> 1000 K is required to the condensations outside of the inner region are located produce a detectable near-IR H2 spectrum, special exci- asymmetrically in the SW region. tation conditions must exist when the near-IR spectrum is Two spectra were taken on this PN, one positioned on present. In Paper I we discussed mechanisms of H2 exci- the central star, and the other at a position 3′′ E (Fig- tation in PNe; see also Kastner et al. (1996). If detected ure 12). The core shows bright stellar continuum, with in sufficient number, the observed H2 line ratios are an ex- nebular lines superimposed, and Paβ absorption. The E cellent diagnostic for determining the relative importance spectrum has the typical H I and He I emission lines. The of shocks and UV photons in a photodissociation region sky subtraction was not of high quality for this spectrum, (PDR) for the excitation of the H2 emission. Even if the which resulted in OH airglow lines showing up in emission excitation mechanism cannot be determined, the presence in the H and K spectral regions. of H2 emission is important to understanding the condi- tions in PNe and how they evolve through wind interac- J 320 3.1.18. tions and photodissociation. Images of J 320 (Balick 1987) show it to have a central An analysis of near-IR H2 emission can determine an region that is elongated roughly E-W, but the low level ortho-to-para (O/P) ratio, the rotational excitation tem- flux has a N-S elongation indicating a shell or streamer perature Tex(J), and the vibrational excitation tempera- extending in this direction. Three spectra for J 320 are ture Tex(v) of the molecules. If the rotational and vibra- shown in Figure 13, centered on the core (C), offset 1′′ tional excitation temperatures differ, then UV excitation is N, and offset 1′′. 5 N. The core has a stronger contribution indicated. This is most readily determined by comparing from stellar continuum, but otherwise the spectra are sim- the column densities in the upper state vibration-rotation ilar. We therefore detect no spectral differences between levels with the upper state energy (in temperature units; the N extension and the nebula near the core. see Hora & Latter 1994, 1996 for a full discussion; see also Black & van Dishoeck 1987; Sternberg & Dalgarno 3.1.19. M 4–18 1989). When many H2 lines are detected, especially those This young, low-excitation PN was recently imaged with from highly excited levels that fall in the J band, a much HST by Dayal et al. (1997) and shows a toroidal shell sur- stronger case can be made for the importance of UV excita- rounding the central star. There is strong mid-IR emission tion than does the traditional v =2 → 1 S(1) to v =1 → 0 6 Near-IR PN Spectral Survey

S(1) line ratio (e.g. Hora & Latter 1994, 1996). The com- kinematic study that the inner bright lobes (their lobes parison of the column densities to the upper state energy “A” and “B”) are the emission maxima from a radially- levels has been done for the PNe with detected H2 emission expanding toroid viewed nearly in the plane of the sky. and the results are summarized in Table 8. Only the rota- In the near-IR, the inner pairs of lobes are also promi- tional excitation temperatures are listed. For collisionally- nent, but the large E-W lobes are not visible (see Paper I). (shock-) excited spectra, the rotational and vibrational ex- Instead, there is a circular outer halo visible in H2 that is citation temperatures are coupled and the same. For UV not quite centered on the inner lobe structure. Also visible excited spectra, the vibrational temperature is the result are faint H2 “spikes” that extend from the center to the of a cascade through levels and not a thermal process. The circular outer halo, roughly in the equatorial plane of the rotational levels are easily thermalized by collisions. The large optical E-W lobes (Latter & Hora 1998). observed O/P ratio is in general rather uncertain, espe- The spectra shown in Figures 15 and 16 were taken at cially if only v = 1 lines are detected. We did not attempt three different positions in the PN: on the N lobe (of the to determine the O/P ratio for objects without sufficient innermost bright pair of lobes), on the fainter E knot, and line detections. An observed O/P ratio lower than 3 in- on a clump of H2 emission located on the NE edge of the dicates that the H2 emission is not thermally excited. A outer circular halo (see Paper I, Figure 4a; it is the clump subthermal O/P ratio as determined from near-IR spectra visible at the upper left corner of the “H2 sub” image). is not caused by the UV excitation process itself, but is a The N lobe exhibits H I and He I lines from the ionized function of chemistry and density in the PDR (e.g., Hora gas in this region, but also has significant H2 emission. & Latter 1996; Black & van Dishoeck 1987), and might There is also strong [Fe II] emission at 1.64 and 1.257 µm. not be indicative of the “true” O/P abundance ratio of The E knot also displays similar H I, He I, [Fe II], and the H2 (see Sternberg & Neufeld 1999). Selected excita- H2 emission, although fainter. In contrast to the inner re- tion diagrams for several objects that are discussed below gions, the NE clump spectrum in Figure 16 is dominated are shown in Figure 33. by H2 emission, with the only H I lines detected being Paβ and Brγ. There is strong [Fe II] emission at 1.64 and 1.257 3.2.2. NGC 40 µm in this region as well. The excitation analysis for the The morphological classification of NGC 40 is middle three positions observed showed that they are UV-excited, elliptical (Balick 1987), which seems to contradict the pre- except for the E knot position for which there is insuffi- viously observed strong correlation between bipolar mor- cient data. The low value of the observed O/P ratio is phology and H2 detection. However, if one examines the suggestive of the H2 emission arising from a PDR at this low-level emission in the N and S regions of this PN (see location as well. Paper I), one can see material that has broken through Since the inner region of NGC 2440 is morphologically and expanded beyond the elliptical shell defined by the E complex and any line of sight through the PN is likely to and W bright lobes. Mellema (1995) has found the mor- intersect several distinct regions, it is probably the case phology consistent with models of “barrel”-shaped PNe, that the ionized and molecular zones are not mixed as the which have roughly cylindrical emission regions slightly spectra might seem to indicate, but that the slit simply in- bowed outwards at the equatorial plane, and less dense cludes several nebular components, or is looking through a polar regions. Higher resolution and more sensitive opti- PDR and is sampling both the molecular and the recently cal imaging has recently been carried out by Meaburn et ionized gas. al. (1996) show gas escaping from the polar regions of the PN, with other filamentary structure in the outer halo. 3.2.4. NGC 6720 This is the first reported detection of H2 in NGC 40. The spectrum was taken centered on the W lobe, and the NGC 6720 (the “Ring Nebula”) is probably the best- H2 lines are relatively weak compared to the H I and He I known PN, and is the archetype for the ring or elliptical lines from the ionized gas in this region. The H2 emission morphology that characterizes the brightest part of the was not detected in the narrowband imaging surveys of Pa- nebula. The emission is not consistent with a uniform pro- per I or Kastner et al. (1996), so the molecular emission late shell, however, since the ratio of flux between the edge must be confined to a region near the bright ionized gas and center of the ring is higher than expected from a limb- that dominates the spectrum. The data suggest that the brightened shell (Lame & Pogge 1994). Balick et al. (1992) H2 is shock-excited. However, insufficient line detections have suggested that NGC 6720 is actually a bipolar PN make this result less than firm. viewed along the polar axis, based on narrow-band imag- ing and high-resolution spectroscopic observations. This 3.2.3. NGC 2440 view is supported by the presence of H2 in the nebula and NGC 2440 is a bipolar PN with complex morphological halo, which correlates strongly with bipolar morphology. and spectral structure. In the optical, the nebula is bipolar Guerrero, Manchado, & Chu (1997) draw different con- with the major axis in roughly the E-W direction for the clusions, however, based on their chemical abundance and large outer lobes (Balick 1987; Schwartz 1992). However, kinematic study of the nebula. They argue that the Ring there are two bright lobes near the core that are posi- has a prolate ellipsoid structure, with a halo of remnant tioned along an axis roughly perpendicular to the major red giant wind. axis of the outer lobes. There are two fainter knots that Our spectra of the Ring (Figure 17) were obtained at two are also along a roughly E-W axis, but not aligned with positions, one on the bright ring directly N of the central the outer lobes. There are filaments and knots throughout star, and the second position several arcseconds further the lobes. Lopez et al. (1998) finds up to three outflow- north, off the bright ring but on a moderately bright (in ing bipolar structures in the lobes, and find from their H2) position in the halo. Both positions show bright H2 Hora, Latter, & Deutsch 7 emission, with the lobe position also showing contributions obtained a λ = 0.46 − 1.3 µm spectrum of BD+30◦3639; from emission lines of H I and He I from the ionized gas, high-resolution visible and near-IR images were recently as one would expect based on the visible wavelength and obtained by Harrington et al. (1997) and Latter et al. IR images showing the distribution of the line emission. (1998), and ground-based near- and mid-IR images have The ring spectrum is strongly UV excited, indicating it is been presented by Hora et al. (1993), Paper I, and Shupe the PDR interface to the outer molecular shell. et al. (1998). Three positions in BD+30◦3639 were sampled in the 3.2.5. NGC 7026 spectra presented in Figure 20; the emission peak on the N lobe of the ring, the E side of the ring, and on the H2 emis- The late elliptical PN NGC 7026 has two bright lobes ′′ on either side (E-W) of the central star, with fainter bipo- sion region located approximately 3 E of the ring. These lar emission extending roughly N-S from the core. Cuesta, spectra show a steady progression of decreasing emission Phillips, & Mampaso (1996) obtained optical spectra and from the ionized gas and increasing molecular emission as one moves east. As for NGC 7027, the H2 emission in imaging of this object and found kinematically complex ◦ structure, with several separate outflows at the outer edge BD+30 3639 is UV excited (Figure 33a) and defines the of an inner spherical shell, and suggested that the primary PDR (see also Shupe et al. 1998). shell may be undergoing breakup in transition to a more 3.2.8. Hubble 12 typical bipolar outflow structure. Two positions were sampled in NGC 7026, shown in Hubble 12 (Hb 12) has been notable primarily because it Figure 18, centered on the E and W bright lobes near represents one of the clearest cases known of UV excited the central star. The lobe spectra are nearly identical, as near-IR fluorescent H2 emission (Dinerstein et al. 1988; Ramsay et al. 1993). Our Hb 12 results from this survey one might expect from the symmetry in this PN. The H2 emission in this PN is fairly weak at these positions. This and our imaging survey were presented in a previous paper (Hora & Latter 1996); the spectra are reproduced here for might be due to the H2 being concentrated in other regions of the PN, and not in the bright ionized lobes that were comparison with the rest of the survey. sampled by the spectra presented here. We are unable to Dinerstein et al. had mapped the inner structure and determine the excitation mechanism. found it to be elliptical surrounding the central star; our deep H2 images showed the emission to be tracing the 3.2.6. NGC 7027 edges of a cylindrical shell around the star, with faint bipo- lar lobes extending N-S. We also detected [Fe II] line emis- NGC 7027 is one of the most highly studied PN at all sion at 1.64 µm in a position along the edge of the shell. wavelengths, particularly in the infrared because of its The H2 line ratios observed were in excellent agreement brightness and wealth of spectral features. Treffers et al. with predictions by theoretical H2 fluorescence calcula- (1976) obtained a spectrum for λ = 0.9 − 2.7 µm with a tions, and no significant differences were found between beam that included the entire nebula. They identified the the excitation in the two positions of the nebula that were major near-IR spectral components, including the first de- sampled (see also Luhman & Rieke 1996). tection of H2 lines in a PN, and the first detection of the unidentified line at 2.29 µm. Since then, several near- 3.2.9. IC 2003 IR spectra have been published, including Scrimger et al. IC 2003 is a round, high-excitation PN that has a ring of (1978), Smith, Larson, & Fink (1981), Rudy et al. (1992), emission, with a bright knot on the S edge (Manchado et and Kelly & Latter (1995). al. 1996; Zhang & Kwok 1998). Feibelman (1997) obtained The spectra shown in Figure 19, one taken centered on IUE spectra of this PN that shows a wealth of nebular and the W bright lobe, and the other at the brightest position stellar lines. The IR spectra presented in Figure 22 taken I in H2 of the NW lobe (see Paper I). Both show H and H2 in the center of the PN shows that there is little contin- emission; the H2 is relatively stronger in the NW position uum from the nebula; the emission is primarily from lines than in the bright lobe. Narrowband imaging has shown of H I in the J, H, and K bands. There is strong unidenti- I I that the H and He emission is primarily in the bright fied emission at 2.286 µm but none detected at 2.199 µm. inner ring of the nebula, and the H2 emission is in what H2 emission is tentatively detected in the K-band, in the appears to be bipolar lobes outside of this shell (Graham v =1 → 0 S(1), v =3 → 2 S(1), and v =1 → 0 Q(1) lines. et al. 1993a,b; Paper I; Latter et al. 1998). It has been ar- Each of the lines are detected at roughly a 2σ level. The gued before based on morphology that the H2 is in a PDR line fluxes are not reliable or numerous enough to allow (Graham et al. 1993a). Our data clearly demonstrate this fitting of the line ratios. to be the case, with the H2 showing a strongly UV excited spectrum in a relatively high density medium (see Figure 3.2.10. IRAS 21282+5050 33b). The young, carbon-rich PN IRAS 21282+5050 has been ◦ identified as having an 07(f)-[WC11] nucleus (Cohen & 3.2.7. BD+30 3639 Jones 1987) with possibly a binary at its center. Strong The young PN BD+30◦3639 is well-studied in the in- 12CO has been detected in a clumpy expanding shell frared, and is remarkable primarily because of its large IR (Likkel et al. 1988) with elongated emission N-S. Shibata emission excess. It has many similarities to NGC 7027, et al. (1989) believe the elongated emission suggests the including its IR morphology and the presence of H2 in the presence of a dust torus in the E-W direction; however, near-IR and unidentified IR (UIR) emission features in the Meixner et al. (1993) was evidence for a clumpy, expand- mid-IR spectrum, which are usually attributed to poly- ing elliptical envelope. The elongated structure is also seen cyclic aromatic hydrocarbons (PAHs). Rudy et al. (1991) in the visible (Kwok et al. 1993). Weak continuum flux at 8 Near-IR PN Spectral Survey

2 and 6 cm suggests a young PN just beginning to be ion- 3.2.13. M 2–9 ized (Likkel et al. 1994; Meixner et al. 1993). Kwok et M 2–9 (the “Butterfly”) is a highly symmetric bipo- al. (1993) believe there has been a recent sharp drop in lar nebula, with lobes extending from opposite sides of a luminosity based on the measured CO/FIR ratio. Weak bright central core, nearly in the plane of the sky. Bright HCO+ and 13CO are present (Likkel et al. 1988). knots of emission are visible in the lobes at the N and S Two positions were sampled on IRAS 21282+5050, cen- ′′ ends. Our results for M 2–9 from this survey were pre- tered on the bright core, and offset approximately 3 N ′′ viously presented in Hora & Latter (1994), and some of and 3 W. The spectrum of the offset position is shown in the spectra are reproduced in Figures 25 and 26 for com- Figure 22. The core is dominated by continuum emission parison. High-resolution imaging in several near-IR lines from the central star. Also present are both emission lines indicated that the lobes had a double-shell structure, with from the ionized gas, and H2 features in the K-band. The ′′ the inner shell dominated by H I and He I line emission nebula is compact, about 4 in diameter at K (Paper I). from ionized gas and continuum emission scattered from The slit therefore samples a slice through the entire nebula, the central source, and the outer shell (the “Lobe O” spec- and as a result this spectrum does not necessarily imply trum in Figure 25) of the lobes showing strong H emission that the molecular and ionized gas is mixed. The Lobe 2 which exhibit a spectrum consistent with UV excitation spectrum shows primarily lines of H (with the OH night 2 in a PDR. The core region shows a strong dust continuum sky lines showing up in absorption because of imperfect component, as well as emission lines of H I, He I, Fe II, sky subtraction in this spectrum). The lack of emission [Fe II] and O I. The N knot has strong [Fe II] emission, lines due to H I and He I in the Lobe spectrum indicates with relatively weaker H I, He I, and H2 emission. that the H2 emission is predominantly in the outer regions of the PN. The data are suggestive of shock excitation, but this should be considered tentative. 3.2.14. Vy 2–2 Vy 2–2 is a compact PN, so very little is known about 3.2.11. M 1–16 its morphology. The spectrum obtained in this survey was M 1–16 is a PN with a near-IR bright central region taken centered on the bright core and the slit sampled most and bipolar lobes with fast winds extending at least 35′′ or all of the emission from this object. The spectrum con- from the core (Schwartz et al. 1992; Aspin et al. 1993; tains stellar continuum, lines of H I and He I emission from Sahai et al. 1994). Several spectra were obtained in this the nebula, and weak H2 emission. This detection confirms PN scanning across the central region; the two positions the indication of H2 emission as reported by Dinerstein et shown in Figure 23 are on the core position and 1′′ S of the al. (1986). The spectrum shown in Figure 26 is similar ◦ core. Both positions show H2 emission; the S position is to others in this category, such as BD+30 3639 and NGC slightly brighter in both H2 and the ionized nebular lines. 2440, where several nebular components are superimposed Our data reveal that the H2 is UV excited in both regions because of the position and size of the slit. As for those observed. This had be suggested earlier by Aspin et al. objects, the H2 spectrum in Vy 2–2 is also UV excited. (1993). The core shows a slight rise towards long wave- lengths indicating emission from warm dust continuum. 3.3. H2 dominated 3.2.12. M 1–92 The PNe in this group have spectra that primarily con- tain emission lines of H2. These objects all have bipolar M 1–92 (“Minkowski’s Footprint”) is a bipolar proto- morphology, and most are young or proto-PNe (PPNe). planetary nebula similar in near-IR appearance to AFGL The PPNe also have warm continuum dust emission or 618, and has evidence of highly collimated outflows along stellar continuum that is strongest in the core. Table 7 the bipolar axis (Paper I; Trammell & Goodrich 1996 and lists the line identifications and fluxes for the PNe in this references therein). Two positions were sampled in M 1– section. 92, one in the core and one on the NW bipolar lobe. There are problems with the sky background subtraction in both spectra, which are most prominent in the λ = 1.9 − 2.1 3.3.1. NGC 2346 µm region of the spectrum, but also contribute to a lower NGC 2346 is a PN with faint bipolar lobes seen clearly signal to noise ratio (S/N) over the whole dataset. Nev- in H2 emission (e.g., Paper I). The brightest part of the ertheless, the primary characteristics are apparent. The nebula is in the “equatorial” region near the central star core region is dominated by strong warm dust continuum where the bipolar lobes meet. Walsh, Meaburn, & White- emission. There is also weak Brγ and Paβ emission, but head (1991) performed deep imaging and spectroscopy the other most other H I and He I lines are too weak to be that showed the full extent of the lobes, and they model detected. The lobe position shows weak H2 emission. The the PN as two ellipsoidal shells that are joined near the emission appears to be shock-excited, but the low excita- central star. The distribution of the H2 emission is similar tion suggested by our data is suggestive of UV excitation. to the optical (Zuckerman & Gatley 1988; Kastner et al. Data of higher S/N are required to discern the dominant 1994; Paper I). excitation mechanism. There might also be H2 emission The near-IR spectrum of NGC 2346 in Figure 27 is dom- near the core that is being masked by the strong contin- inated by UV-excited H2 emission, as shown in Figure 33d. uum emission. In both positions, there also seems to be The spectrum was obtained with the slit positioned on the CO bandhead emission at λ =2.3 − 2.5 µm although the bright condensation to the W of the central star. There S/N is not high in these regions. is also weak Paβ and Brγ emission seen, which is possibly reflected from near the central star. Hora, Latter, & Deutsch 9

3.3.2. J 900 al. 1996). There is an enigmatic equatorial region seen The PN J 900 is a bipolar nebula with an unusual “jet”- in H2 emission and might be traced by other molecu- like structure and an outer shell structure that is seen pri- lar species, such as HCN (Latter et al. 1993; Bieging & Ngyuen-Quang-Rieu 1996; Sahai et al. 1998b). marily in H2 emission (Shupe et al. 1995; Paper I). The spectrum of J 900 shown in Figure 27 was obtained at Similar to AFGL 618, this object also has a rich molec- a position N of the brighter lobe just NW of the central ular content. SiC2 is seen in absorption (Cohen & Kuhi star, centered on the “jet” of emission. Problems with 1977); this feature is usually found in stars of the high- sky-subtraction caused the J and H-band portions of the est carbon abundance. Strong absorption features of C3 spectrum continuum to be slightly negative. There is no and emission in C2 (Crampton et al. 1975) are present, detected continuum in any part of the spectrum. The while C2 is also seen in absorption in reflected light from the lobes (Bakker et al. 1997). The CO J = 1 → 0 H2 spectrum is shock-excited in a moderate velocity wind (Figure 33e). line shows three distinct velocity structures (Kawabe et al. 1987; Young et al. 1992). 3.3.3. AFGL 618 Our results for this object from this survey were pre- viously presented in Hora & Latter (1994, 1995) and our AFGL 618 is a carbon-rich, bipolar reflection nebula narrowband imaging in Latter et al. (1993). The spec- with a relatively hot central star (≈ 30, 000 K), similar tra are reproduced here for comparison with the rest of spectra in the two lobes, and the eastern lobe is signifi- the survey. Spectra were obtained at several positions in cantly brighter than the other. In this as in other ways, the nebula, including positions along the N lobe, and in the object bears a great resemblance to AFGL 2688 (see the equatorial region (see Hora & Latter 1994 for details). below), despite the fact that their central star tempera- The emission is segregated; the core is dominated by con- tures differ by about a factor of 5. The visible spectrum tinuum emission, there are emission lines of C2 and CN shows numerous emission lines characteristic of ionized gas further from the core along the lobes, and the H2 emission (Westbrook et al. 1975; Schmidt & Cohen 1981) which are is confined to the ends of the lobes and in the equatorial scattered by dust into the line of sight, with a small H II re- region in what appears to be a ring or toroidal structure gion surrounding the central object (Carsenty & Solf 1982; (Latter et al. 1993; Sahai et al. 1998b). Our analysis of Kelly, Latter, & Rieke 1992). The near-IR spectrum of the H2 line ratios showed that the emission is collisionally AFGL 618 is also dominated by rotation-vibration lines of excited in shocks, with no discernible difference between H2 (Thronson 1981, 1983; Latter et al. 1992; Paper I). the emission in the lobes and the equatorial region. AFGL 618 exhibits a rich spectrum of molecular line emission (Lo and Bechis 1976; Knapp et al. 1982; Cer- 3.4. Continuum - dominated nicharo et al. 1989; Kahane et al. 1992; Martin-Pintado These are young PNe or PPNe that have strong warm & Bachiller 1992; Bachiller et al. 1997; Young 1997). The dust continuum and little line emission. The strongest 12 13 17 18 lines detected include CO, CO, C O, C O, CS, NH3, component is in general the core, with most of the emission + HCN, HCO , CN, and C I. from an unresolved point source. In some of the nebulae, Two of the positions sampled are presented here in Fig- ′′ emission structure extends a few arcseconds from the core ure 28 – the core spectrum and one taken 2. 4 E of the region. Also, in objects such as AFGL 915, they are asso- core. Both spectra show strong H2 emission, along with ciated with larger optical nebulae that extend arcminutes [Fe II] and weak Paβ and Brγ. In addition, the core has from the core. In this survey, only the regions near the a warm dust continuum that is apparent throughout the core were sampled. spectrum, and clear CO bandhead features in the 2.3 – 2.4 µm region. The CO features are also present but at 3.4.1. AFGL 915 ′′ lower levels in the 2. 4 E spectrum position. Our analysis AFGL 915 (the “Red Rectangle”) is a carbon-rich bicon- of the H2 spectrum confirms the earlier results by Latter et ical reflection nebula with a metal-depleted spectroscopic al. (1992) – the spectrum is dominated by a shock-heated binary at its center (Cohen et al. 1975). The nebula ap- component, but a UV excited component is clearly present pears axially symmetric and shows spikes running tangent as well (Figure 33c). to the edge of the bicone. Surrounding the post-AGB star at its center is a circumbinary disk viewed edge-on (Jura, 3.3.4. AFGL 2688 Balm, & Kahane 1995) which could be oxygen-rich (Wa- AFGL 2688 (the “Egg Nebula”) is a bipolar reflection ters et al. 1998). nebula (Ney et al. 1975) at visible and near-infrared wave- C2 and CN are not detected near the binary, though C2 lengths. It has a central star that exhibits the spectrum is present in emission in the reflection lobes. CH+ (0,0) of a carbon-rich supergiant (Crampton et al. 1975; Lo & and (1,0) are detected in emission (Bakker et al. 1997; Bechis 1976). Similar in visible appearance to AFGL 915, Balm & Jura 1992). CO is underabundant, with relatively each lobe shows two “jets” or “horns” extending away from weak emission and broad wings detected (Dayal & Bieging the central region (Crampton et al. 1975; Latter et al. 1996; Greaves & Holland 1997; Loup et al. 1993; Bujarra- 1993; Sahai et al. 1998a). The lobes have identical spectra bal et al. 1992). Glinski et al. (1997) found CO and C I at visible wavelengths, but their brightness differs signif- in the UV in both absorption and emission. They expect icantly (Cohen & Kuhi 1977). The near-IR spectrum is strong CO overtone emission in the IR based on their ob- dominated by H2 rotation-vibration lines (Thronson 1982; servations of hot CO emission and absorption in the UV. Beckwith 1984; Latter et al. 1993). A central source is The object shows ERE (extended red emission) from about seen in the mid-IR and longer wavelengths, with fainter λ = 5400 to 7200 A˚ and a set of emission bands around extended emission along the axis of the nebula (Hora et 5800 A˚ (Schmidt, Cohen, & Margon 1980) whose carriers 10 Near-IR PN Spectral Survey might be the same material as the carriers of the DIBs PNe in this group of the sample, however, do have IR “ex- (diffuse interstellar bands). This object also shows strong cess” continuum emission from warm dust, which in some emission in the PAH bands at 3.3, 7.7, and 11.2 µm (Co- cases prompted their inclusion in this sample. hen et al. 1975), which are located predominantly in the The spectral groups with molecular and/or dust con- lobes and spikes of emission (Bregman et al. 1993; Hora tinuum emission are primarily bipolar. This classification et al. 1996). includes objects such as NGC 6720 which have a ring mor- Spectra taken at two different positions are shown, one phology but are thought to be bipolar viewed pole-on; Hb ′′ centered on the core, and the other at 4 S of the core. 12 which is brightest in H2 in the equatorial region and Both show strong warm dust continuum, and the core along the outer edges of the lobes; M 2–9 which is brightest also has strong CO bandhead emission features in the in H2 at the edges of the lobes with no equatorial emission λ =2.3 − 2.4 µm range. other than at the core; and AFGL 2688 which is bright- est along the axis of the bipolar lobes, with H2 emission 3.4.2. IRC+10◦420 in the equatorial plane. Clearly this is a heterogeneous ◦ group with a wide range of emission and morphological IRC+10 420 is a highly evolved, OH/IR star that is differences that imply a range of evolutionary tracks and thought to be in a post-red supergiant phase (Jones et al. states. 1993). The central star seems to have changed spectral type, transitioning recently to an early A type (Oudmai- 4.1.2. The Carbon-to-Oxygen Ratio jer 1998). Oudmaijer et al. (1996) detected several of the hydrogen lines in absorption and emission in the near-IR, Carbon stars, although a small fraction of all AGB stars, return about half of the total mass injected into the ISM and Oudmaijer (1998) presented a high-resolution 0.38 – 1 by all AGB stars, since they have on average much higher µm spectrum showing a large number of emission and ab- − − > 4 1 sorption lines. Recent HST imaging by Humphreys et al. mass loss rates ( 10 M⊙ yr ) than do O-rich ob- jects. The carbon-to-oxygen (C/O) abundance ratio in (1997) shows that the circumstellar environment around PNe has previously been shown to correlate with morphol- this star is extremely complex, with spherical outer shells that extend to a diameter of 6 arcseconds, and several in- ogy (Zuckerman & Aller 1986), with bipolar PNe tending to be carbon-rich. It is therefore expected that the C/O ner condensations. In the near- and mid-infrared, bipolar ∼ ratio also correlates with the spectral classifications pre- lobes are visible that extend 2 arcseconds from the core. I The spectrum of IRC+10◦420 shown in Figure 31 was sented here. This is in general the case, with the H - line dominated PNe having C/O ratios less than or about taken centered on the object. The slit length includes the inner few arcseconds of the object, although it is domi- 1, whereas the remaining categories which are dominated > nated by the bright core. The observed spectrum shows by the bipolar PNe have C/O ratios 1, as reported by Zuckerman & Aller (1986) and Rola & Stasi´nska (1994). a bright and relatively featureless continuum. Some H I lines, e.g., Paβ, are seen in absorption. Rola & Stasi´nska discuss problems with previous determi- nations of the C/O ratio, and use different criteria that result in a slightly lower percentage of carbon-rich PNe 3.4.3. M 2–56 (35%) than others. Their ratios are used in the discussion The PPN M 2–56 is a bipolar nebula with a bright below. central core. It is similar in morphology to AFGL 618, The morphology of PN also has been shown to depend although it seems to be at an earlier evolutionary stage on the progenitor mass (see Corradi & Schwarz 1995), with since it does not appear to have an H II region (Trammell, the bipolar PN being more massive than other morpholog- Dinerstein, & Goodrich 1993; Goodrich 1991). The spec- ical types. This relationship, along with the link between trum of M 2–56 shown in Figure 31 was taken centered on carbon abundance and morphology, suggests that carbon the core of this PPN. The dominant feature is a hot dust stars are the progenitors of bipolar PN and those with continuum that is most prominent in the K band region a large amount of molecular material. The mechanisms of the spectrum. There are some residual features in the that cause massive carbon-rich stars to preferentially form spectrum from imperfect sky subtraction, mostly in the K bipolar PN are still not understood. band. There are some exceptions to the correlation of morpho- logical type to C/O ratio; in particular, NGC 6543 has a 4. DISCUSSION AND SUMMARY much higher value (9.55) than the others in the class. In 4.1. Spectral Categories the other extreme, NGC 2346 stands out as having a low C/O ratio (0.35) compared to other bipolar PNe in the H2 The PNe spectra presented in this paper were grouped - dominated group. This object is a much more evolved according to spectral characteristics as described above. object than the others in its group (e.g., AFGL 2688), and The groups are an efficient way to present the data, but exhibits weak Paβ emission, showing that the ionized gas also can be seen to correlate strongly with other charac- is present although weak relative to the molecular emission teristics of the PN. in the nebula. 4.1.1. Morphology 4.2. Spectral Sampling of Morphological Features The group of H I - line dominated PNe is composed of This survey has differed from many previous investiga- primarily elliptical or round PNe, along with the peculiar tions in that a short, narrow slit was used to obtain the or irregular nebulae of the sample. In general these PNe data, rather than a large beam that could include most or are well-known from optical studies, identified either by all of the nebula. Because of this, one cannot easily use the their morphology or their optical spectra. Many of the spectra presented here to model the PNe in a global sense, Hora, Latter, & Deutsch 11 if that requires a measurement of the total flux from the Black & van Dishoeck 1987). object. Also, if a complete census of emission lines were The first two mechanisms have been identified in several required, some might be missed if there were variations PNe, such as thermal excitation in AFGL 2688 (e.g., Hora of emission characteristics across the nebula and certain & Latter 1994; Sahai et al. 1998a), pure UV excitation in a regions were not sampled. low density gas around Hb 12 (e.g., Dinerstein et al. 1988; The spatial selectivity that prevents viewing the entire Hora & Latter 1996; Luhman & Rieke 1996), and UV ex- PN at once, however, has proven to be an advantage when citation in a high density gas in M 2–9 (Hora & Latter trying to examine various aspects of the PN, including 1994) and NGC 7027 (Graham et al. 1993b; this paper). variations across the nebula, as a function of distance from A combined spectrum was found from a detailed analy- the central star, or in examining certain morphological fea- sis of AFGL 618 (Latter et al. 1992; this paper). While tures. For example, in M 2–9 and NGC 2440, the emission the form of the excitation might be apparent for these and of the lobe walls and emission knots were separately sam- other objects, it is not always evident what is the source of pled, which showed the large spectral differences in these the warm gas or UV photons. Winds are present in AFGL regions. This information is important for modeling the 2688 which could directly heat the gas through shocks, but structure and formation of the PN. Another reason why considerable grain streaming is likely taking place as well the small aperture is useful is that if the emission from a (see Jura & Kroto 1990). group of lines such as H2 is to be modeled, it is important Very fast winds and dissociating shocks are present in to compare the emission from a clump of material where AFGL 618, M 2–9 (e.g., Kelly, Latter, & Hora 1998), and the conditions do not vary greatly over its size. For exam- M 1–16 (Sahai et al. 1994; Schwarz 1992), and all show ple, the emission from H2 present very close to the central clear evidence of UV excitation. In addition, the photon star in a strong UV field could be quite different from H2 path to the H2 emitting regions is not in a direct line-of- emission from the outer parts of the halo. Also, the small sight to the central star, which for photons coming from slit has aided in detecting weak H2 emission from several the central star suggests scattering in what is a fairly low PNe such as NGC 40, where detection would have been density medium. Alternatively, we are seeing in each of difficult if the central star and the rest of the nebula could these objects excitation of H2 at the bipolar lobe walls by not be excluded from the measurement. UV photons generated within strong shocks produced by the fast winds. This hypothesis was explored through de- 4.3. Summary of Molecular Hydrogen Emission in PNe tailed modeling by Latter et al. (1992) of AFGL 618, but A long-standing problem in the interpretation of H2 the high relative intensity of the thermally excited emis- emission from interstellar and circumstellar environments sion and poor spatial resolution limited this analysis. The is understanding the excitation mechanism. Three fun- presence of very fast winds in the lobes of each of these damental mechanisms are possible. One is excitation objects, and the presence of UV excited H2 emission at of a near-infrared fluorescence spectrum resulting from the lobe walls strongly suggests that indirect excitation of a rotational-vibrational cascade in the ground electronic the H2 is occurring by interactions with photons generated state following electronic excitation by the absorption a by wind-produced shocks. Detailed modeling of sensitive, UV photon in the Lyman and Werner bands (Black & van high spatial resolution spectra is required. It is also ev- Dishoeck 1987). A second excitation mechanism is colli- ident, in general, that without detailed spectra, H2 is a sional excitation in a warm gas (TK ∼> 1600 K). While UV rather poor diagnostic of overall conditions in PNe and excitation in a low density gas produces an easily iden- PPNe. tifiable spectrum, the level populations can be driven to If we conclude that all of the ways to excite H2 in PNe produce thermal line ratios when the UV flux is large and and PPNe listed above are present and important, what densities begin to exceed ≈ 104 cm−3 (Sternberg & Dal- does this imply for our understanding of these objects and garno 1989). Detailed spectral and morphological analysis the utility of H2 as a diagnostic? It is now well under- are often required to determine an origin of the near-IR stood that the presence of molecular emission from PNe spectrum. A third excitation mechanism is formation of and PPNe is tied to the morphology of the objects such H2 on the surfaces of dust grains and in the gas phase. that if molecular emission is present, the object has a bipo- While potentially important in isolated regions of certain lar morphology (e.g., Zuckerman & Gatley 1988; Latter et objects, we do not consider this to be generally impor- al. 1996; Kastner et al. 1996, and references therein). We tant in PNe and PPNe relative to the other two processes. have argued that H2 emission is excited in multiple ways in This is because molecular formation in PNe is relatively PNe and PPNe. While special conditions are required for slow compared to dissociation rates. H2 emission to be seen in near-IR spectra, the conditions In PNe and PPNe, the situation can be complicated by that drive the excitation are common in all PNe and PPNe both dominant excitation mechanisms being present simul- and are not clearly dependent on morphological type. A taneously, and in different forms. Several ways of exciting conclusion that can be drawn from this argument alone near-IR H2 emission have been identified as possible: di- is that molecular material is present in nebulae with a rect thermal excitation in warm gas created behind moder- bipolar morphology and a significant amount of molecu- ate velocity shocks, direct excitation by UV photons from lar material is not present in other morphological types. the hot central star, somewhat indirectly by collisional Therefore, objects that have a bipolar morphology must excitation in warm gas created by rapid grain streaming have a dense, high mass envelope in which the molecular (e.g. Jura & Kroto 1990), and excitation through absorp- material can be shielded and survive dissociation for rel- tion of Lyα photons (by an accidental resonances with the atively long times – suggesting a high mass loss rate and 1 + 1 + B Σu − X Σg v =1 − 2 P(5) and R(6) transitions of H2) a high mass progenitor star. A correlation between bipo- which can be generated in a nearby strong shock (e.g., lar morphology and high mass progenitor stars has been 12 Near-IR PN Spectral Survey found by others (e.g., Corradi & Schwarz 1995). It is ap- We thank Xander Tielens and David Hollenbach for parent that the presence of H2 emission in a PN is not useful discussions and encouragement. We acknowledge tied to directly to the morphology, but that the bipolar support from NASA grant 399-20-61 from the Long Term morphology is intimately related to the density and mass Space Astrophysics Program. WBL was supported during of the circumstellar envelope, and therefore the mass of part of this study by a National Research Council Research the progenitor star. Why high mass, high mass loss rate Associateship. asymptotic giant branch stars shed material in an axisym- metric, not spherical, way remains a mystery.

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Fig. 1.— Spectra of NGC 1535, NGC 2022, and NGC 2392. The spectra have been offset and scaled by the constants shown in the plot labels. The brightest lines in the lower spectra in the figure have been clipped to keep them from overlapping with the spectra above them. At the bottom, some of the prominent lines have been labeled with small vertical lines. The first row are H I, the second row He I, and below the rows individual lines have been indicated. These are the same for all plots in this spectral grouping for means of comparison; they do not necessarily indicate that the lines were detected in any or all of the spectra plotted in the figure. The spectral data points between λ = 1.32 − 1.42 µm and 1.8 – 1.9 µm are in regions of poor atmospheric transmission and are not plotted. The positions in the nebula where these spectra were taken is given in Table 1.

Fig. 2.— NGC 3242 (see caption to Figure 1). Hora, Latter, & Deutsch 15

Fig. 3.— NGC 6210 (see caption to Figure 1).

Fig. 4.— NGC 6543 and NGC 6790 (see caption to Figure 1). 16 Near-IR PN Spectral Survey

Fig. 5.— NGC 6572 (see caption to Figure 1).

Fig. 6.— NGC 6803 (see caption to Figure 1). Hora, Latter, & Deutsch 17

Fig. 7.— NGC 6826 (see caption to Figure 1).

Fig. 8.— NGC 7009 (see caption to Figure 1). 18 Near-IR PN Spectral Survey

Fig. 9.— NGC 7662 and IC 351 (see caption to Figure 1).

Fig. 10.— IC 418 (see caption to Figure 1). Hora, Latter, & Deutsch 19

Fig. 11.— IC 2149 (see caption to Figure 1).

Fig. 12.— IC 3568 and IC 4593 (see caption to Figure 1). 20 Near-IR PN Spectral Survey

Fig. 13.— J320 (see caption to Figure 1).

Fig. 14.— M 4–18 (see caption to Figure 1). Hora, Latter, & Deutsch 21

Fig. 15.— Spectra of NGC 40 and NGC 2440. The spectra have been offset and scaled by the constants shown in the plot labels. At the bottom, some of the prominent lines have been labeled with small vertical lines. The first row are H I, the second row He I, and the third row H2. These are the same for all plots in this spectral grouping for means of comparison; they do not necessarily indicate that the lines were detected in any or all of the spectra plotted in the figure. The spectral data points between λ = 1.32 − 1.42 µm and 1.8 – 1.9 µm are in regions of poor atmospheric transmission and are not plotted. Below the rows individual lines have been indicated. The positions in the nebula where these spectra were taken is given in Table 1.

Fig. 16.— NGC 2440 (see caption to Figure 15). 22 Near-IR PN Spectral Survey

Fig. 17.— NGC 6720 (see caption to Figure 15).

Fig. 18.— NGC 7026 (see caption to Figure 15). Hora, Latter, & Deutsch 23

Fig. 19.— NGC 7027 (see caption to Figure 15).

Fig. 20.— BD+30◦3639 (see caption to Figure 15). 24 Near-IR PN Spectral Survey

Fig. 21.— Hubble 12 (see caption to Figure 15).

Fig. 22.— IC 2003 and IRAS 21282+5050 (see caption to Figure 15). Hora, Latter, & Deutsch 25

Fig. 23.— M 1–16 (see caption to Figure 15).

Fig. 24.— M 1–92 (see caption to Figure 15). 26 Near-IR PN Spectral Survey

Fig. 25.— M 2–9 (see caption to Figure 15).

Fig. 26.— M 2–9 and Vy 2–2 (see caption to Figure 15). Hora, Latter, & Deutsch 27

Fig. 27.— J 900 and NGC 2346 (see caption to Figure 15).

Fig. 28.— AFGL 618 (see caption to Figure 15). 28 Near-IR PN Spectral Survey

Fig. 29.— AFGL 2688 (see caption to Figure 15).

Fig. 30.— AFGL 915. The spectra have been offset and scaled by the constants shown in the plot labels. The spectral data points between λ = 1.32 − 1.42 µm and 1.8 – 1.9 µm are in regions of poor atmospheric transmission and are not plotted. The positions in the nebula where these spectra were taken is given in Table 1. Hora, Latter, & Deutsch 29

Fig. 31.— M 2–56 and IRC+10◦420 (see caption to Figure 30).

Fig. 32.— M 1–78 and K 4–45 (see caption to Figure 15). 30 Near-IR PN Spectral Survey

1.0 1.0

o 0.0 v = 1 BD+30 3639 H2 0.0 v = 1 NGC 7027 W

-1.0 -1.0 v = 2 v = 3 -2.0 -2.0 4,2 S(6) v = 5 v = 3 7,5 Q(3) 9,7 O(3) -3.0 -3.0 v = 2

N(v,J)/g(J)N(1,3)] v = 8 3 N(v,J)/g(J)N(1,3)]

3 8,5 Q(3)

ln[g -4.0

ln[g -4.0 v = 4 -5.0 v = 9 -5.0

-6.0 4,2 S(5) 5000 10000 15000 20000 25000 30000 35000 40000 45000 -6.0 5000 10000 15000 20000 25000 30000 35000 40000 45000 Tupper (K) Tupper (K)

1.0 1.0

0.0 AFGL 618 2.4 East 0.0 NGC 2346 v = 1 -1.0 -1.0

-2.0 v = 2 -2.0 v = 1 -3.0 7,5 Q(3) v = 2 3,1 S(2) -3.0 N(v,J)/g(J)N(1,3)] N(v,J)/g(J)N(1,3)] 3

-4.0 3 v = 3 ln[g ln[g -4.0 -5.0 8,5 Q(3) v = 3

-5.0 -6.0 4,2 S(5) -7.0 -6.0 5000 10000 15000 20000 25000 30000 35000 40000 45000 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 T (K) Tupper (K) upper

1.0 J900 "Jet" v = 2 0.0 v = 1

-1.0

-2.0 N(v,J)/g(J)N(1,3)] 3 -3.0 ln[g

-4.0

-5.0 5000 10000 15000 20000 25000

Tupper (K) Fig. 33.— Excitation diagram for several of the PNe detected in H2. Shown are the upper state vibration-rotation level populations relative to that in the v = 1,J = 3 level plotted against the energy of the upper state in Kelvin. The statistical weight, gJ , for odd J levels includes the ortho-to-para ratio as determined from the data (Table 8), or if not determined the thermal value of 3 was used. The data are labeled by the upper state vibration level. Linear fits to the different vibrational levels determines the rotational excitation temperature. The lines shown are characteristic for this value of Tex(J). Line ratios not used in the analysis because of blending are not plotted. Dereddening of the ◦ H2 spectrum has been done using the attenuation values shown in Table 8 (or not at all). a) BD+30 3639 at the “H2” slit position shows strong UV excitation (see also Shupe et al. (1998). b) NGC 7027 at the “W” slit position also shows strong UV excitation at relatively high density (see also Graham et al. (1993a). c) AFGL 618 at 2′′. 4 E of the core shows a combined UV and shock-excited spectrum (see also Latter et al. 1992). The arrow is connected to the v = 1 (square) point and indicates an upper limit. The dotted line is a linear fit to the v = 1 and v = 2 data points. d) NGC 2346 is also dominated by UV excitation. The solid line is a linear fit (Tex = 2500 K) to all the data points and is offset for clarity. The dashed lines are representative of Tex(J) = 1260 K. e) J 900 shows only shock excitation of the H2. For another example of a shock (collisional) excitation diagram, see AFGL 2688 in Hora & Latter (1994).

TABLE

PN Survey Summary

Observation Slit Sp ectral Classical

a b c d

No Ob ject PN G Dates UT Orient Positions Comp onents Morphology

Hydrogen recomb line dominated

NGC NS W lob e H I eRo

NGC EW E ring H I eE

NGC NS E lob e H I eRo

NGC NS SE knot E ring SW halo H I eE

00 00

NGC NS Core E E H I I

NGC NS S knot H I P

NGC NS Core E lob e H I Cs Cw lE

NGC NS Core H I Cw S

NGC NS E lob e NW halo H I mE

NGC NS CS SW lob e halo H I eE

NGC NS N nebula W edge H I mE

NGC NS Ring H I Cs eE

IC EW Center H I

IC NS CS E Lob e Halo H I Cw eE

IC NS CS E lob e H I Cs P

IC EW CS N Edge H I E

IC NS CS E nebula H I Cs I

00

00

J EW Core N N H I B

M


NS Core H I Cw Cs E

Hydrogen recomb lines molecular hydrogen

e

NGC NS W lob e H I H mE

NGC NSEW N E lob es NE clump H I H Fe II B

NGC EW N ring N halo H I H mB

e

NGC NS W E Lob es H I lE

NGC NS W lob e NW H Lob e H I H Cw mE



BD EW N E ring H Lob e H I H Cw eRo

00 00

00

Hb NS CS E E S H I H CwFe II B

e

IC EW Center H I H Cw

I


EW Core Lob e H H I Cw eE

00

M NS Core S H H I B

e

M


NS Core NW lob e H I H Cw CO B

M NSEW CS N knot NE Lob e H I H Cw Fe II B

Vy NS Core H I H Cw S

Molecular hydrogendominated

NGC EW W Filament H Pa B

00

AFGL NS Core E Cw H CO B

00

00

AFGL


NSEW N N E Lob e H Cw Cs B

J EW H jet H B

Continuumdominated

00

AFGL


NS Core S Cw CO H I B

IRC


NS Core Cw H I S

M


EW Core Cw B

HI I regions

K


EW Brightest lob e H H I B

M NS SW knot H I H Cw B

a

Strasb ourg Planetary Nebulae catalog number Acker et al

b

Unless otherwise sp ecied the slit was centered on the brightest part of comp onent sp ecied CS Central Star

c

H I hydrogen recombination lines H molecular hydrogen Cs stellar continuum Cw warm dust continuum CO CO

bandhead emission

d

Classical morphology categories E elliptical B Bip olar Ri ring Ro round S stellar ie unresolved P p eculiar I

irregular Mo diers in lower case b efore category e early m middle l late

e

New detection of H Wavelength A b NGC




















         NGC
































     NGC





























      E NGC























        H I PN TABLE Line SE NGC























        Fluxes a H NGC
































     E NGC
































     E NGC






































   NGC
































     C NGC











            E NGC




















         He He He He C He Fe He Pa He He O I I I I I I I I I I I I Identication Pa C Fe

Fe I I H I I I Fe I I Wavelength A b NGC
















































































       NGC

































































            NGC






































TABLE                      E NGC Continued




















                           SE NGC




















                           H NGC












































                   E NGC



































                      E NGC



































                      NGC









































                    C NGC


























                         E NGC























                          Br Br Br Br Br Br Br Br He Br Br Br Br Br He Br Br Br Fe He He He Br U U He c c Identication I I I I I I I I I H Br H H H H H H H H H H H H H H H I

I I I I I I I I I I I I I I I H Mg I I Wavelength c b a Unidentied Fluxes These A are are b the in lines units measured NGC




















observed    of wavelengths NGC in erg





























several cm NGC





























other with s a and PNe E NGC TABLE





























 have see error not text SE of NGC een b





























 Continued A corrected H NGC





























for extinction E NGC














     E NGC





























NGC











      C NGC           E NGC           Pf Pf Pf Pf Pf Pf Pf Identication Pf Pf Pf H H H H H H H H I I I I I I I I Wavelength A b E NGC

















           SW NGC






































    SWH NGC












































  N NGC





























     H   I PN TABLE Line W NGC






































    Fluxes a NGC
































      IC
































      C IC





























       E IC




















          H IC















































 He He C Fe Pa He He He He O He Fe Fe I I I I I I I I I I I I I I Identication Pa Fe C

Fe Fe I I H I I I I I Fe I I Wavelength A b E NGC





























                        SW NGC






































                     SWH NGC

































































TABLE             N NGC












































Continued                    W NGC






































                     NGC


















































                 IC












































                   C IC









































                    E IC





























                        H IC































































































  Br Br Br Br Br Br Br Br Br Br Br Br Br Br Br Br Br He He Br Br He He He Identication I I I I I I H H H H H H H H H H H H H H H H H H H I I I I I I I I I I I I I I I I I I I Mg I Wavelength c b a Unidentied Fluxes These A are are b the in lines units measured E NGC








observed                of wavelengths in SW erg NGC several












































   cm other with s SWH NGC a and PNe


















































TABLE   have see error not text of N NGC een b 









































Continued     A corrected W NGC












































 for   extinction NGC









































    IC









































    C IC












































   E IC





























        H IC


















































 Identication He Pf Pf Pf Pf Pf Br U Pf Pf He U Pf Pf Pf c c I I I Br H H H H H H H H I I I I I I I I

H I Wavelength A b C IC















































   E IC
































        IC





























         C IC















































   H I PN TABLE E Line IC















































   Fluxes J C a















































   J N


















































  J N


















































  M














              He He He C He Pa He Fe He He O I I I I I I I I I I I Identication Pa C Fe

I Fe I H I I I Fe I I Wavelength c b a Unidentied Fluxes These A are are b the in lines units measured C IC





















































observed                of wavelengths in erg E several IC














                            cm other with s a and PNe IC









































TABLE                     have see error not text of C een b  IC









































Continued                    A corrected E IC






















































































for     extinction J C
























































              J N

































































           J N

































































           M





























                       Br Br Br Br Br Br Br Br Br Br Br Br Br Fe Br Br Pf Pf He Br Pf Pf Pf He He Pf He Pf Br Pf Identication I I I I I I H Br H H H H H H H H H H H H H H H H H H H H H H H I I I I I I I I I

I I I I I I I I I I I I I I I H Mg I I Wavelength A b NGC
























































   NE NGC






























































 N NGC


















































     T H NGC





















































    H I TABLE PN L NGC
































Line            Fluxes OL NGC






























































a  W NGC


























             NW NGC























              BD H




















                BD N















































       BD OE




















                He C He H He He H H He H H H H H H H He Fe H I C Identication I I I I I I I O I I I S Fe H S S Q Q S S Q Q Q Q Fe Fe I I I I I S Wavelength A b NGC
























































            NE NGC






















































































  N NGC
























































TABLE             T NGC







































































Continued        L NGC
















































































    OL NGC




























































































W NGC























                       NW NGC























                       BD H





























                      BD N






































                   BD OE







































































        H Pa He He H O He H Br Br Br Br H Br H Br Br H Br Br Br Br Fe Br Br I I I I I I Pa Identication H H H H H H H H H H H H H H S S I I I I I I I I I I I Q

I I S Q S Q O S H Mg I Q I S Wavelength A b NGC













































































       NE NGC










































































        N NGC
























































TABLE               T NGC




































































Continued           L NGC






































                    OL NGC



















































































     W NGC









































                   NW NGC









































                   BD H









































                    BD N






























































             BD OE


















































                 He Br He Br H H H H He He H H H H H H He H Br H H U He H H H c H I I I I I I I I H Br Identication H I

I S Q Q S S S O O S Q S S S O S S H S I Fe I I Wavelength c b a Unidentied Fluxes These A are are b the in lines units measured NGC





















































observed    of wavelengths in NE erg NGC several


















































    cm other with s N NGC a and PNe















































TABLE       have see error not text of T NGC een b 





















































Continued    A corrected L NGC












































for       extinction OL NGC





















































   W NGC





























           NW NGC
































          BD H



































          BD N























              BD OE



































          H U CO H H Pf H CO Pf CO Pf Pf Pf Pf Pf H H H H Pf c Identication H H H H H H H H H I I I I I I I I O S S S S S Q Q Q S Wavelength A b Hb core


















































   Hb 00




















E              c 00 Hb E





























          S c H IC















































    H I TABLE I PN



























































Line Fluxes M core
































         a M S



































        M NW
































         M Core















































    N M Knot


















































   d o e Lob M



























































O d Vy









































      C He H H He He Fe H H H H H H H H He Fe I I I I I I O I I H Fe Identication Fe S S S Q S S Q Q Q I I Fe I I I S Fe I S Wavelength A b Hb core


















































                Hb 00





















































E                c 00 Hb E















































                 TABLE S c IC

































































           Continued I































































































 M core










































































        M S










































































        M NW

























































































   M Core



























































             N M Knot

























































































   d o e Lob M































































































 O d Vy





















































               Pa He H O He H H H Br H H C H Br Br Br Br Br Br Br H Br Fe H Br Br Br H H H I I I I I I Pa H H H H H H H H H H Identication H H H S I I I I I I I I I I

I I O S S S S Q Q S S Q Q H I Q S S Q Wavelength A b Hb core







































































          Hb 00






































E                      c 00 Hb E


















































TABLE                  S c IC










































































Continued          I

























































































    M core






























































             M S
























































               M NW










































































         M Core




































































           N M Knot













































































        d o e Lob M







































































          O d Vy
























































               Br Fe Br H H He He H Br Fe C H Br He H H Br He H H H H H H He H He U H H H H H e I I I I I I I I I I I I I H Br Identication H H H I

I I I O S Q S S O S S O S S S S S S S O H H Fe I I I Fe Fe He S I I I I I Wavelength d e c b a Unidentied See Fluxes See These A Hora Hora are are b the in Latter Latter lines units measured Hb core






































observed        of for wavelengths for in an Hb an erg 00 several






































E        explanation explanation cm c other with s 00 Hb E a and of PNe












































of      TABLE S slit slit  have see c error ositions p ositions p not text of IC een b















































     Continued A corrected I


















































   for extinction M core


















































   M S















































    M NW












































     M Core



























































N M Knot


















































   d o e Lob M









































      O d Vy




















             Pf H CO H f Pf CO Pf U CO Pf Pf Pf H Pf Pf H H H Pf e Identication H H H H H H H H H H I I I I I I I I I O S S S Q Q Q S Wavelength A b NGC












































   AFGL











E               AFGL

















H             core Dominated o e lob AFGL





















































c PN TABLE torus AFGL H





















































I I Region c J jet Line


















































 Fluxes J o e lob


















































a  K





















































M









































    C He H He H H H H H H Fe H He Pa He H H I I I I I I I I Pa Identication S Fe

S S Q S S Q Q Q S Fe I H I I I S S Wavelength A b NGC
















































































       AFGL





















































E                 AFGL















































TABLE                  core  o e lob AFGL
















































































Continued        c torus AFGL







































































          c J jet






















































































     J o e lob




























































































   K


































































































 M





























                        O Br H He Br Br H Br H Br Br Br Fe Br Br H H H He Br He H H H H He He H H I I I I I I I I H H H H H H Identication H H H H H I I I I I I I I I I Q O S S S S S S S S S S Q Br Fe I I Q H I Wavelength d c b a See Fluxes Unidentied These A Hora are are b the in Latter lines units measured NGC


















































observed        of for wavelengths in an erg AFGL several explanation



































E             cm other with s AFGL a and of PNe
































TABLE          core slit      have see error ositions p not text of o e lob AFGL een b 



























































Continued     A corrected c torus AFGL












































for          extinction c J jet
























































     J o e lob
























































     K






























































   M


























               H Br H H H CO H U CO H Pf Pf CO Pf Pf Pf Pf H H H H c Br H H H H H H Identication H

I I I I I I S S S S S S S Q Q Q H I S Pf O H I

TABLE

H Excitation Analysis Results

2

1 2 3

Ob jectPosition UV Excited T J S S OP A

ex V

K mag

4

NGC No 

NGC Yes  

5

NGC E lob e Yes 




NGC N lob e Yes  

NGC NE Clump No  

NGC Ring Yes   

4

NGC Halo No 




6

NGC

NGC NW Yes  

NGC W Yes  

AFGL Core Yes   

AFGL E Yes   

AFGL No  

 5

BD N Yes  



BD E Yes   



BD H Yes   

Hb E Yes  

Hb E S Yes 

IC

4

I No 

J Jet No 

J Lob e No 

M Core Yes 




M S Yes  

4

M No

M N knot

M O Lob e Yes  

Vy Yes 

1

For UV excited sp ectra T J is the rotational excitation temp erature For collisionally excited

ex

sp ectra T J T v

ex ex

2

Listed only for those ob jects with enough lines well detected to make an estimate of the OP ratio

see Sternberg Neufeld

3

Value of visual attenuation used to deredden the H sp ectra for the excitation analysis as determined

2

from the H lines only and using a standard interstellar extinction law Rieke Leb ofsky Entries

2

with errors shown are determined to greater accuarcy than those without which should b e considered

highly uncertain In no case do es the value of A change the basic results of the analysis

V

4

v detections only

5

v transitions detected

6

means there are not enough lines detected to make an excitation analysis