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Register a new userMorphological study of the nested planetary nebula Hubble 12
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We present a visible-infrared imaging study of young planetary nebula (PN) Hubble 12 (Hb 12; PN G111.8-02.8) obtained with Hubble Space Telescope (HST) archival data and our own Canada-France-Hawaii Telescope (CFHT) measurements. Deep HST and CFHT observations of this nebula reveal three pairs of bipolar structures and an arc-shaped filament near the western waist of Hb 12. The existence of nested bipolar lobes together with the presence of H2 knots suggests that these structures originated from several mass-ejection events during the pre-PN phase. To understand the intrinsic structures of Hb 12, a three-dimensional model enabling the visualisation of this PN at various orientations was constructed. The modelling results show that Hb 12 may resemble other nested hourglass nebulae, such as Hen 2-320 and M 2-9, suggesting that this type of PN may be common and the morphologies of PNs are not so diverse as is shown by their visual appearances. The infrared spectra show that this PN has a mixed chemistry. We discuss the possible material that may cause the unidentified infrared emissions. The analyses of the infrared spectra and the spectral energy distribution suggest the existence of a cool companion in the nucleus of this object.
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We present a detailed kinematical analysis of the young compact hourglass-shaped planetary nebula Hb 12. We performed optical imaging and longslit spectroscopy of Hb 12 using the Manchester echelle spectrometer with the 2.1m San Pedro Martir telescope. We reveal, for the first time, the presence of end caps (or knots) aligned with the bipolar lobes of the planetary nebula shell in a deep [NII]6584 image of Hb 12. We measured from our spectroscopy radial velocities of 120 km/s for these knots. We have derived the inclination angle of the hourglass shaped nebular shell to be 65 degrees to the line of sight. It has been suggested that Hb 12s central star system is an eclipsing binary (Hsia et al. 2006) which would imply a binary inclination of at least 80 degrees. However, if the central binary has been the major shaping influence on the nebula then both nebula and binary would be expected to share a common inclination angle. Finally, we report the discovery of high-velocity knots with Hubble-type velocities, close to the core of Hb 12, observed in Halpha and oriented in the same direction as the end caps. Very different velocities and kinematical ages were calculated for the outer and inner knots showing that they may originate from different outburst events.
The ACIS-S camera on board the Chandra X-ray Observatory has been used to discover a hot bubble in the planetary nebula (PN) IC4593, the most distant PN detected by Chandra so far. The data are used to study the distribution of the X-ray-emitting gas in IC 4593 and to estimate its physical properties. The hot bubble has a radius of ~2$^{primeprime}$ and is found to be confined inside the optically-bright innermost cavity of IC 4593. The X-ray emission is mostly consistent with that of an optically-thin plasma with temperature $kTapprox0.15$ keV (or $T_mathrm{X}approx1.7times10^{6}$ K), electron density $n_mathrm{e}approx15$ cm$^{-3}$, and intrinsic X-ray luminosity in the 0.3-1.5 keV energy range $L_mathrm{X}=3.4times10^{30}$ erg s$^{-1}$. A careful analysis of the distribution of hard ($E>$0.8 keV) photons in IC 4593 suggests the presence of X-ray emission from a point source likely associated with its central star (CSPN). If this were the case, its estimated X-ray luminosity would be $L_mathrm{X,CSPN}=7times10^{29}$ erg s$^{-1}$, fulfilling the log$(L_mathrm{X,CSPN}/L_mathrm{bol})approx-7$ relation for self-shocking winds in hot stars. The X-ray detection of the CSPN helps explain the presence of high-ionisation species detected in the UV spectra as predicted by stellar atmosphere models.
The HASH (Hong Kong/ AAO/ Strasbourg/ H{alpha}) planetary nebula research platform is a unique data repository with a graphical interface and SQL capability that offers the community powerful, new ways to undertake Galactic PN studies. HASH currently contains multi-wavelength images, spectra, positions, sizes, morphologies and other data whenever available for 2401 true, 447 likely, and 692 possible Galactic PNe, for a total of 3540 objects. An additional 620 Galactic post-AGB stars, pre-PNe, and PPN candidates are included. All objects were classified and evaluated following the precepts and procedures established and developed by our group over the last 15 years. The complete database contains over 6,700 Galactic objects including the many mimics and related phenomena previously mistaken or confused with PNe. Curation and updating currently occurs on a weekly basis to keep the repository as up to date as possible until the official release of HASH v1 planned in the near future.
We present the images of a textit{Hubble Space Telescope} (textit{HST}/WFC3) snapshot program of angularly compact Galactic planetary nebulae (PNe), acquired with the aim of studying their size, evolutionary status, and morphology. PNe that are smaller than $sim4arcsec$ are underrepresented in most morphological studies, and today they are less well studied than their immediate evolutionary predecessors, the pre-planetary nebulae. The images have been acquired in the light of [ion{O}{3}]$lambda5007$, which is commonly used to classify the PN morphology, in the UV continuum with the aim of detecting the central star unambiguously, and in the $I-$band to detect a cool stellar companion, if present. The sample of 51 confirmed PNe exhibits nearly the full range of primary morphological classes, with the distribution more heavily weighted toward bipolar PNe, but with total of aspherical PNe almost identical to that of the general Galactic sample. A large range of microstructures is evident in our sample as well, with many nebulae displaying attached shells, halos, ansae, and internal structure in the form of arcs, rings, and spirals. Various aspherical structures in a few PNe, including detached arcs, suggest an interaction with the ISM. We studied the observed sample of compact Galactic PNe in the context of the general Galactic PN population, and explore whether their physical size, spatial distribution, reddening, radial metallicity gradient, and possible progenitors, are peculiar within the population of Galactic PNe. We found that these compact Galactic PNe, which have been selected based on apparent dimensions, constitute a diverse Galactic PN population that is relatively uniformly distributed across the Galactic disk, including the outskirts of our Galaxy. This unique sample will be used in the future to probe the old Galactic disk population.
Planetary Nebulae (PN) emit enormous amount of energy in several emission lines. Measuring the line-flux for PNe in a given stellar population, the Planetary Nebula Luminosity Function (PNLF) can be compiled. Surveys of PNe revealed that the faint-end of the PNLF can be approximated by a simple exponential dependency expected for an expanding spherical shell. However at the bright-end there exists a steep cut-off which was unexpected and remains unexplained. Interestingly, the cut-off value appears to be nearly the same for different stellar populations as young spiral galaxies and old elliptical galaxies and, despite the lack of understanding, became an extragalactic distance estimator. Here we show that the recently computed post-AGB evolutionary tracks are capable to explain the decades old mystery. All new models with ages between 1 and 7 Gyr (progenitor masses between 2.0 and 1.1 of solar mass) evolve fast enough to ionize the PN, and at similar post-AGB luminosity which allows the [O III] 500.7nm line to reach nearly the same magnitude. The new models predict that the Sun at the end of its life will form a rather faint PN.
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