An Optical Emission Line Survey of Large Planetary Nebulae

view Abstract Citations (43) References (201) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Catalog of Ultraviolet, Optical, and Near-Infrared Emission Lines Identified in Supernova Remnants Fesen, Robert A. ; Hurford, Alan P. Abstract Optical spectra of two filaments in the Cygnus Loop are used to investigate the faint optical line spectra of supernova remnants (SNRs). Data on a bright, previously studied filament in the remnant's northeast rim (NGC 6992) provide accurate relative line strengths for many faint emission lines present in shocked, low-density interstellar gas. Spectra of a particularly strong [O III] λλ4959, 5007 filament {I([O m])/I(Hβ≃45} reveal both a high [O III] electron temperature (60000 ± 3000 K) and many high-ionization lines, including [Ar IV], [Ar V], [Ne IV], [Ca V, [Cl III], [Fe VI], [Fe VII], and [Fe X]. Taken together, these data reveal 16 new emission lines not previously seen in any SNR, plus an additional 11 emission lines seen only once before in various remnants. These new spectral results are incorporated into a comprehensive catalog of over 250 emission lines identified in Galactic and Magellanic Cloud SNRs within the wavelength range 900-12000 Å, and are complete through 1995. Along with accurate laboratory wavelengths and commonly observed relative line intensity information, this tabulation lists individual remnants and references for less commonly observed lines. UV, optical and lines identified in SNRs organized by ionization stage, and a reference list of observational papers sorted by remnant and wavelength regime are also given. Publication: The Astrophysical Journal Supplement Series Pub Date: October 1996 DOI: 10.1086/192348 Bibcode: 1996ApJS..106..563F Keywords: CATALOGS; INFRARED: ISM: LINES AND BANDS; LINE: IDENTIFICATION; ISM: SUPERNOVA REMNANTS full text sources ADS | data products SIMBAD (21)

The nature of turbulence in the warm ionized component of the interstellar medium (WIM) can be investigated using Fabry-Perot spectroscopy of optical emission lines. The Hα intensity provides the emission measure (EM) along a line of sight, which is used in conjunction with the scattering measure, rotation measure, and dispersion measure to study interstellar turbulence. Observations at high spectral resolution ( ∼ 10 km s −1) allow measurements of the bulk radial velocity structure of the emitting gas and investigations of thermal and non-thermal (turbulent) broadening mechanisms through the line widths. By measuring the widths of the Hα line and an emission line from a heavier atom (e.g. the [S II] λ6716 line), one can separate the thermal and non-thermal contributions to the line width. Preliminary studies using this method have shown that the broad range of Hα line widths (typically 15 – 50 km s −1) is mostly due to differences in the non-thermal component of the width and that along many lines of sight this component dominates. The Wisconsin Hα Mapper (WHAM) is in the process of producing a very sensitive kinematic map of the northern sky in Hα at 1 o angular resolution and 12 km s −1 spectral resolution. WHAM is also mapping emission lines from heavier atoms such as sulfur and nitrogen for selected regions of the sky. This data set will provide unique new information concerning turbulence in the WIM. 1.

We present the first optical identification and confirmation of a sample of supernova remnants (SNRs) in the nearby galaxy NGC 3344. Using high spectral and spatial resolution data, obtained with the CFHT imaging Fourier transform spectrograph SITELLE, we identified about 2200 emission line regions, many of which are H ii regions, diffuse ionized gas regions, and also SNRs. Considering the stellar population and diffuse ionized gas background, which are quite important in NGC 3344, we have selected 129 SNR candidates based on four criteria for regions where the emission lines flux ratio [S ii]/H α ≥ 0.4. Emission lines of [O ii] λ3727, H β, [O iii] λλ4959,5007, H α, [N ii] λλ6548,6583, and [S ii] λλ6716,6731 have been measured to study the ionized gas properties of the SNR candidates. We adopted a self-consistent spectroscopic analysis, based on Sabbadin plots and Baldwin, Phillips & Terlevich diagrams, to confirm the shock-heated nature of the ionization mechanism in the candidates sample. With this analysis, we end up with 42 Confirmed SNRs, 45 Probable SNRs, and 42 Less likely SNRs. Using shock models, the confirmed SNRs seem to have a metallicity ranging between Large Magellanic Cloud and 2×solar. We looked for correlations between the size of the confirmed SNRs and their emission lines ratios, their galaxy environment, and their galactocentric distance: We see a trend for a metallicity gradient among the SNR population, along with some evolutionary effects.

The LMC is ideal for studying the coevolution of planetary nebulae (PNs) and their central stars in that the debilitating uncertainties of the Galactic PN distance scale and selection biases from attenuation by interstellar dust do not apply. We present images and analyze slitless spectra that were obtained in a survey of Large Magellanic Cloud PNs. These data on 29 targets were obtained with the Hubble Space T elescope (HST ) using the Space Telescope Imaging Spectrograph. The data permit us to determine the nebular dimensions and morphology in the monochromatic light of several emission lines, including those that have traditionally been used for morphological studies in the Galaxy : Ha ,[ NII] j6583, and [O III] j5007, plus others of varying ionization including [O I], He I, and [S II]. Together with the 31 resolved LMC PNs for which monochromatic images exist in the HST archive, these data show that the incidence of nonsymmetric nebulae, including bipolar nebulae (which is an indicator of Population I ancestry in the Galaxy), is signiÐcantly higher than that reported for the Galaxy. The onset of asymmetric features appears even in very young nebulae (with dynamical ages of D1400 yr), suggesting that at least the gross features of the nebular morphology may be more closely tied to PN formation and that subsequent shaping of the expanding envelope by the radiation Ðeld and wind from the central star may play the lesser role of amplifying these gross features. There is some evidence of evolution between two morphological types in the sense that bipolar core nebulae may evolve to pure bipolars late in the PN lifetime. Subject headings : Magellanic Clouds E planetary nebulae : general E stars : evolution

NGC 185 is a dwarf spheroidal satellite of the Andromeda galaxy. From mid-1990s onwards it was revealed that dwarf spheroidals often display a varied and in some cases complex star formation history. In an optical survey of bright nearby galaxies, NGC 185 was classified as a Seyfert galaxy based on its emission line ratios. However, although the emission lines in this object formally place it in the category of Seyferts, it is probable that this galaxy does not contain a genuine active nucleus. NGC 185 was not detected in radio surveys either in 6 or 20 cm, or X-ray observations, which means that the Seyfert-like line ratios may be produced by stellar processes. In this work, we try to identify the possible ionization mechanisms for this galaxy. We discussed the possibility of the line emissions being produced by planetary nebulae (PNe), using deep spectroscopy observations obtained with GMOS-N, at Gemini. Although the fluxes of the PNe are high enough to explain the integrated spectrum, the line ratios are very far from the values for the Seyfert classification. We then proposed that a mixture of supernova remnants and PNe could be the source of the ionization, and we show that a composition of these two objects do mimic Seyfert-like line ratios. We used chemical evolution models to predict the supernova rates and to support the idea that these supernova remnants should be present in the galaxy.

Aims. As a new approach to the study of resolved stellar populations in nearby galaxies, our goal is to demonstrate with a pilot study in NGC 300 that integral field spectroscopy with high spatial resolution and excellent seeing conditions reaches an unprecedented depth in severely crowded fields. Methods. Observations by MUSE with seven pointings in NGC 300 have resulted in data cubes that are analyzed in four ways: (1) Point spread function-fitting 3D spectroscopy with PampelMUSE, as already successfully pioneered in globular clusters, yields de-blended spectra of individually distinguishable stars, thus providing a complete inventory of blue and red supergiants, and asymptotic giant branch (AGB) stars of type M and C. The technique is also applicable to emission line point sources and provides samples of planetary nebulae (PNe) that are complete down to m5007 = 28. (2) Pseudo-monochromatic images, created at the wavelengths of the most important emission lines and corrected for continuum light with the P3D visualization tool, provide maps of H II regions, supernova remnants (SNR), and the diffuse interstellar medium (ISM) at a high level of sensitivity, where also faint point sources stand out and allow for the discovery of PNe, Wolf–Rayet (WR) stars, etc. (3) The use of the P3D line-fitting tool yields emission line fluxes, surface brightness, and kinematic information for gaseous objects, corrected for absorption line profiles of the underlying stellar population in the case of Hα. (4) Visual inspection of the data cubes by browsing through the row-stacked spectra image in P3D is demonstrated to be efficient for data mining and the discovery of background galaxies and unusual objects. Results. We present a catalog of luminous stars, rare stars such as WR, and other emission line stars, carbon stars, symbiotic star candidates, PNe, H II regions, SNR, giant shells, peculiar diffuse and filamentary emission line objects, and background galaxies, along with their spectra. Conclusions. The technique of crowded-field 3D spectroscopy, using the PampelMUSE code, is capable of deblending individual bright stars, the unresolved background of faint stars, gaseous nebulae, and the diffuse component of the ISM, resulting in unprecedented legacy value for observations of nearby galaxies with MUSE.

We present images and slitless spectra which were obtained in HST surveys of Planetary Nebulae (PNe) in both the Large and Small Magellanic Clouds, using the Space Telescope Imaging Spectrograph. These new data on 59 PNe (54 in the LMC and five in the SMC) permit us to determine the nebular dimensions and morphology in the monochromatic light of several emission lines: Halpha, [N II] lambda 6583 and [O III] lambda 5007, plus others of varying ionization, including [O I], He I, and [S II]. We describe the nebular morphology and related features in detail. This survey, when combined with similar data from our prior HST programs and other archived PN images, brings the total of nebulae imaged with HST to 114 in the LMC and 35 in the SMC. We describe various basic properties for the sample, including sizes, morphologies, densities, and completeness. Trends in [O III] lambda 5007 flux, surface brightness, and electron density with physical radius suggest that many nebulae, particularly those with bipolar morphology, may be optically thick even at large size. Bipolars also show the most extreme values of [N II]/Halpha flux ratios, which is a rough indicator N enrichment.

We have obtained spectra of the 42 supernova remnants (SNRs) and remnant candidates identified in the recent survey of the inner portion of M33. Relative fluxes for the important diagnostic emission lines in the red portion of the optical spectrum (6200-7500 A) are reported. We have confirmed that all the candidate SNRs have [S II]/Hα ratios >= 0.4, the canonical dividing line between SNR emission and emission from the photoionized gas in H II regions and planetary nebulae. Significant [O I] emission, another distinguishing characteristic of shocked gas, is also seen in the majority of the remnants. We find little evidence of emission line variation with SNR diameter, unlike that reported in previous SNR samples. Using published grids of shock models, we derive abundances and abundance gradients in the interstellar gas in M33. While the oxygen abundances and gradient derived agree (to within the rather large errors) with those derived from H II region studies, the nitrogen abundances and gradient show the same offset as previously noted in studies of other galaxies. Subject headings : galaxies : abundances galaxies : individual (M33) - H ii regions - nebulae: supernova remnants

We report on observations of several optical emission lines toward a variety of newly revealed faint, large-scale Halpha-emitting regions in the Galaxy. The lines include [NII] 6583, [NII] 5755, [SII] 6716, [OIII] 5007, and HeI 5876 obtained with the Wisconsin H-Alpha Mapper (WHAM) toward sightlines that probe superbubbles, high latitude filamentary features, and the more diffuse warm ionized medium (WIM). Our observations include maps covering thousands of square degrees toward the well-known Orion-Eridanus bubble, a recently discovered 60deg x 20deg bipolar superbubble centered in Perseus, plus several classical HII regions surrounding OB stars and hot evolved stellar cores. We use the emission line data to explore the temperature and ionization conditions within the emitting gas and their variations between the different emission regions. We find that in the diffuse WIM and in the faint high latitude filamentary structures the line ratios of [NII]/Ha and [SII]/Ha are generally high, while [OIII]/Ha and HeI/Ha are generally low compared to the bright classical HII regions. This suggests that the gas producing this faint wide-spread emission is warmer, in a lower ionization state, and ionized by a softer spectrum than gas in classical HII regions surrounding O stars, the presumed ionization source for the WIM. In addition, we find differences in physical conditions between the large bubble structures and the more diffuse WIM, suggesting that the ionization of superbubble walls by radiation from interior O associations does not account entirely for the range of conditions found within the WIM, particularly the highest values of [NII]/Ha and [SII]/Ha.

Diagnostic diagrams of emission-line ratios have been used extensively to categorize extragalactic emission regions; however, these diagnostics are occasionally at odds with each other due to differing definitions. In this work, we study the applicability of supervised machine-learning techniques to systematically classify emission-line regions from the ratios of certain emission lines. Using the Million Mexican Model database, which contains information from grids of photoionization models using cloudy, and from shock models, we develop training and test sets of emission line fluxes for three key diagnostic ratios. The sets are created for three classifications: classic H ii regions, planetary nebulae, and supernova remnants. We train a neural network to classify a region as one of the three classes defined above given three key line ratios that are present both in the SITELLE and MUSE instruments’ band-passes: [O iii]λ5007/H β, [N ii]λ6583/H α, ([S ii]λ6717+[S ii]λ6731)/H α. We also tested the impact of the addition of the [O ii]λ3726, 3729/[O iii]λ5007 line ratio when available for the classification. A maximum luminosity limit is introduced to improve the classification of the planetary nebulae. Furthermore, the network is applied to SITELLE observations of a prominent field of M33. We discuss where the network succeeds and why it fails in certain cases. Our results provide a framework for the use of machine learning as a tool for the classification of extragalactic emission regions. Further work is needed to build more comprehensive training sets and adapt the method to additional observational constraints.

Aims. Two-dimensional spectroscopic data for the whole extent of the NGC 3132 planetary nebula have been obtained. We deliver a reduced data-cube and high-quality maps on a spaxel-by-spaxel basis for the many emission lines falling within the Multi-Unit Spectroscopic Explorer (MUSE) spectral coverage over a range in surface brightness >1000. Physical diagnostics derived from the emission line images, opening up a variety of scientific applications, are discussed. Methods. Data were obtained during MUSE commissioning on the European Southern Observatory (ESO) Very Large Telescope and reduced with the standard ESO pipeline. Emission lines were fitted by Gaussian profiles. The dust extinction, electron densities, and temperatures of the ionised gas and abundances were determined using Python and PyNeb routines. Results. The delivered datacube has a spatial size of ~63′′× 123′′, corresponding to ~0.26 × 0.51 pc2 for the adopted distance, and a contiguous wavelength coverage of 4750–9300 Å at a spectral sampling of 1.25 Å pix−1. The nebula presents a complex reddening structure with high values (c(Hβ) ~ 0.4) at the rim. Density maps are compatible with an inner high-ionisation plasma at moderate high density (~1000 cm−3), while the low-ionisation plasma presents a structure in density peaking at the rim with values ~700 cm−3. Median Te, using different diagnostics, decreases according to the sequence [N II], [S II] →[S III] → [O I] → He I → Paschen Jump. Likewise, the range of temperatures covered by recombination lines is much larger than those obtained from collisionally excited lines (CELs), with large spatial variations within the nebula. If these differences were due to the existence of high density clumps, as previously suggested, these spatial variations would suggest changes in the properties and/or distribution of the clumps within the nebula. We determined a median helium abundance He/H = 0.124, with slightly higher values at the rim and outer shell. The range of measured ionic abundances for light elements are compatible with literature values. Our kinematic analysis nicely illustrates the power of 2D kinematic information in many emission lines, which sheds light on the intrinsic structure of the nebula. Specifically, our derived velocity maps support a geometry for the nebula that is similar to the diabolo-like model previously proposed, but oriented with its major axis roughly at PA ~ −22°. We identified two low-surface brightness arc-like structures towards the northern and southern tips of the nebula, with high extinction, high helium abundance, and strong low-ionisation emission lines. They are spatially coincident with some extended low-surface brightness mid-infrared emission. The characteristics of the features suggest that they could be the consequence of precessing jets caused by the binary star system. A simple 1D Cloudy model is able to reproduce the strong lines in the integrated spectrum of the whole nebula with an accuracy of ~15%. Conclusions. Together with similar work with MUSE on NGC 7009, the present study illustrates the enormous potential of wide field integral field spectrographs for the study of Galactic planetary nebulae.

We present long slit spectrophotometric emission line fluxes of bright and extended (< 5 arcsec in diameter) planetary nebulae (PNe), selected from a catalogue with suitable equatorial coordinates for northern hemisphere. In total, 17 planetary nebulae have been chosen and observed in 2008–2010. To measure absolute fluxes, broad slit sizes, ranging from 3.5 to 7.5 arcsec were used and thus equivalent widths (EW) of all observable emission line fluxes were also calculated. Among 17 planetary nebulae observed, line flux measurements of 12 of them were made for the first time. This work also aims to extend the sky coverage of emission line flux standards in northern hemisphere (52 planetary nebulae in southern hemisphere; 6 planetary nebulae in northern hemisphere). Electron temperatures and densities, and chemical abundances of these planetary nebulae were also calculated in this work. These data are expected to lead the photometric or spectrometric further work for absolute emission line flux measurements needed for H ii regions, supernova remnants etc.

The first IUE observations of the "O VI Sequence" planetary nebula He 2-55 are reported. The ultraviolet spectrum is dominated by strong emission lines of O V, C IV, He II, and C III], plus a number of weaker ions for which emission line fluxes were measured. N V λ1240 and C IV λ1549 show P Cygni profiles. The stellar terminal wind velocity of 4500 ± 400 km s-1 is derived from the C IV λ1549 absorption. Interstellar extinction, E(B - V) = 0.54 ± 0.1, was determined from the observed flux of the He II λ1640/λ4686 lines. The only density diagnostic available from low-dispersion data, the Si III]/C III] emission-line ratio, yields an electron density of log Ne = 9.5 ± 0.5 cm-3 but usually results in higher log Ne than that derived from the C III] F(λ1907/λ1909) diagnostic that requires high-dispersion data.

The Wisconsin H-Alpha Mapper (WHAM) has completed a velocity-resolved map of\ndiffuse H-alpha emission of the entire northern sky, providing the first\ncomprehensive picture of both the distribution and kinematics of diffuse\nionized gas in the Galaxy. WHAM continues to advance our understanding of the\nphysical conditions of the warm ionized medium through observations of other\noptical emission lines throughout the Galactic disk and halo. We discuss some\nhighlights from the survey, including an optical window into the inner Galaxy\nand the relationship between HI and HII in the diffuse ISM.\n

Me 2-1 is a high-excitation planetary nebula whose morphology and physical structure have not yet been investigated. We present narrow-band images in several emission lines, and high- and intermediate-resolution long-slit spectra aimed at investigating its morphology and 3D structure, and its physical parameters and chemical abundances. By applying deconvolution techniques to the images, we identified in Me 2-1: an elliptical ring; two elongated, curved structures (caps) that contain three pairs of bright point-symmetric (PS) knots; a shell interior of the ring; and a faint halo or attached shell. The caps are observed in all images, while the PS knots are only observed in the low-excitation emission line ones. These structures are also identified in the high-resolution long-slit spectra, allowing us to study their morphokinematics. The 3D reconstruction shows that Me 2-1 consists of a ring seen almost pole-on, and a virtually spherical shell, to which the caps and PS knots are attached. Caps and PS knots most probably trace the sites where high-velocity collimated bipolar outflows, ejected along a wobbling axis, collide with the spherical shell, are slowed down, and remain attached to it. Although the main excitation mechanism in Me 2-1 is found to be photoionization, a contribution of shocks in the PS knots is suggested by their emission line ratios. The combination of collimated outflows and a ring with a spherical shell is unusual among planetary nebulae. We speculate that two planets, each with less than one Jupiter mass, could be involved in the formation of Me 2-1 if both enter a common envelope evolution during the asymptotic giant branch phase of the progenitor. One planet is tidally disrupted, forming an accretion disk around the central star, from which collimated bipolar outflows are ejected; the other planet survives, causing wobbling of the accretion disk. The physical parameters and chemical abundances obtained from our intermediate-resolution spectrum are similar to those obtained in previous analyses, with the abundances also pointing to a low-mass progenitor of Me 2-1.