We performed a far-IR imaging survey of the circumstellar dust shells of 144 evolved stars as a mission program of the AKARI infrared astronomical satellite. Our objectives were to characterize the far-IR surface brightness distributions of the cold dust component in the circumstellar dust shells. We found that (1) far-IR emission was detected from all but one object, (2) roughly 60–70 % of the target sources showed some extension, (3) 29 sources were newly resolved in the far-IR in the vicinity of the target sources, (4) the results of photometry measurements were reasonable with respect to the entries in the AKARI/FIS Bright Source Catalogue, and (5) an IR two-color diagram would place the target sources in a roughly linear distribution that may correlate with the age of the circumstellar dust shell.

We present the current status update of the Herschel Planetary Nebula Survey Plus project (HerPlaNS+) based on the original General Observer HerPlaNS survey program during the OT1 cycle and the follow-up exhaustive archival search of PN observations using the PACS and SPIRE instruments on-board the Herschel Space Observatory.

We characterized the dusty circumstellar nebula and central star of the C-rich bipolar planetary nebula (PN) NGC 6781 using our own Herschel data augmented with the archival data from UV to radio and constructed one of the most comprehensive photoionization PN models ever produced consisting of the ionized, atomic and molecular gas components as well as the dust component. We reproduced the observed spectral energy distribution (SED), constrained by 136 observational data points. The total nebula mass was estimated to be 0.41 M⊙, with a significant fraction (about 70 %) of it existing in the photo-dissociation region (PDR) surrounding the ionized nebula. This finding demonstrates the critical importance of the PDR in PNe, which are typically recognized as the hallmark of ionized/H+ region. It is therefore essential to characterize the PDR of the circumstellar nebula to understand material recycling in the Milky Way and other galaxies.

We observed two proto-planetary nebulae, HD 56126 representing a source with an elliptical circumstellar shell, and IRAS 16594−4656 representing a source with a bipolar circumstellar shell, with ALMA in the 12CO and 13CO J=3−2 lines and neighboring continuum to see how the morpho-kinematics of CO gas and dust emission properties in their circumstellar environments differ.

The AKARI Far-IR All-Sky Survey (AFASS) maps produced by the AKARI Infrared Astronomical Satellite enabled us to probe the far-IR sky for objects having surface brightnesses greater than a few to a couple of dozen MJy sr−1. Recently, we have verified that, if AFASS-measured fluxes are properly corrected for using the aperture correction method based on the empirical point-spread-function templates derived directly from the AFASS maps, point-source photometry measured from the AFASS maps reproduces fluxes in the AKARI bright source catalogue (BSC). We have surveyed the far-IR sky in the AFASS for Galactic planetary nebulae (PNe) based on the University of Hong Kong/Australian Astronomical Observatory/Strasbourg Observatory Hα Planetary Nebula database (HASHPNDB), preliminarily yielding far-IR fluxes for roughly 1000 Galactic PNe including a few hundreds of PNe not listed in the AKARI/BSC.

We observed the Planetary Nebula NGC 6720 with the Gemini Telescope and the Gemini Multi-Object Spectrographs. We obtained spatial maps of 36 emission-lines in the wavelength range between 3600 Å and 9400 Å. We derived maps of c(Hβ), electronic densities, electronic temperatures, ionic and elemental abundances, and Ionization Correction Factors (ICFs) in the source and investigated the mass-loss history of the progenitor. The elemental abundance results indicate the need for ICFs based on three-dimensional photoionization models.

To understand mass loss history and mass loss and dust formation history of massive AGB stars, we carried out observations of three bipolar planetary nebulae (BPNe) in 30 micron bands from a ground-based telescope. All of our targets have a compact strong emission source in the mid-infrared (MIR) around the position of the central star of planetary nebula (CSPN). These detected emissions can be originated from cool dust. Our results show that the cool dust component is compactly distributed and much more massive than previous studies indicated. These findings suggest that they experienced a strong mass loss into the equatorial direction in past.

As one of the follow-up studies of Herschel Planetary Nebula Survey (HerPlaNS; Ueta et al. 2014), we focus on a bipolar planetary nebula (PN) NGC6781 to characterize the dusty nebula and the central star based on our own Herschel data and the rich archival spectroscopic/photometric image data in the wavelengths from UV to far-IR. With CLOUDY, we constructed a comprehensive photoionization model of NGC6781 ever made including data from UV to radio. We succeeded to reproduce the observed spectral energy distribution (SED) and the atomic gas, H2, CO, and OH molecular line fluxes. We found that about 40% of the total dust mass would be from warm-cold dust components.

We present Herschel PACS and SPIRE images of the dust shells around the planetary nebulae NGC 650, NGC 6853, and NGC 6720, as well as images showing the dust temperature in their shells. The latter show a rich structure, which indicates that internal extinction in the UV is important despite the highly evolved status of the nebulae.

We present Spitzer/MIPS far-infrared (FIR) mapping of O-rich AGB star, R Hya.

We present high-sensitivity near-IR images of a carbon-rich proto-planetary nebula, AFGL 618, obtained with the Infrared Camera and Spectrograph (IRCS) mounted on the 8.2m Subaru Telescope. The deep near-IR images have revealed “bullets” and “horns” extending farther out from the edges of the previously known bipolar nebulosities that consist of dust-scattered star light component and shock-excited line emission component. That these bullets and horns represent the positions from which [Fe II] IR lines arise is strongly suggested from the spatial coincidence between these near-IR microstructures and the optical collimated outflow structure observed by the recent HST/WFPC2 imaging, together with the previous detection of shock-excited, forbidden IR lines of atomic species at those locations. At these positions of the near-IR mincrostructures, we have also discovered CO clumps moving at > 200 km s-1 from our re-analysis of the existing 12CO J = 1 – 0 data obtained with the Berkeley-Illinois-Maryland Association (BIMA) interferometer array. These findings indicate that fast-moving CO clumps seem to be impinging upon the surrounding ambient circumstellar shell, thereby causing shocked emission regions which manifest themselves as the near-IR microstructures at the shock interface. To deepen our understanding of the connection between the near-IR microstructures and the CO outflow structure, we are currently conducting higher resolution observation in CO lines with the BIMA array.

Our observing campaign of proto-planetary nebula (PPN) dust shells has shown that the structure formation in planetary nebulae (PNs) begins as early as the late asymptotic giant branch (AGB) phase due to intrinsically axisymmetric superwind. We describe our latest numerical efforts with a multi-dimensional dust radiative transfer code, 2-DUST, in order to explain the apparent dichotomy of the PPN morphology at the mid-IR and optical, which originates most likely from the optical depth of the shell combined with the effect of inclination angle.