This paper presents a detailed spectral pixel (spaxel) analysis of the ten Luminous Infrared Galaxies (LIRGs) previously observed with the Wide Field Spectrograph (WiFeS), an integral field spectrograph mounted on the ANU 2.3m telescope, and for which an abundance gradient analysis has already been presented by Rich et al. (2012). Here we use the strong emission line analysis techniques developed by Dopita et al. (2013) to measure the ionisation parameter and the oxygen abundance in each spaxel. In addition, we use the observed Hα flux to determine the surface rate of star formation (M yr −1 kpc −2 ) and use the [S II] λλ6717/6731 ratio to estimate the local pressure in the ionised plasma. We discuss the correlations discovered between these physical quantities, and use them to infer aspects of the physics of star formation in these extreme star forming environments. In particular, we find a correlation between the star formation rate and the inferred ionisation parameter. We examine the possible reasons for this correlation, and determine that the most likely explanation is that the more active star forming regions have a different distribution of molecular gas which favour higher ionisation parameters in the ionised plasma.

Two-dimensional (2D) line ratio diagnostic diagrams have become a key tool in understanding the excitation mechanisms of galaxies. The curves used to separate the different regions -H II-like or else excited by an active galactic nucleus (AGN) -have been refined over time but the core technique has not evolved significantly. However, the classification of galaxies based on their emission line ratios really is a multi-dimensional problem. Here we exploit recent software developments to explore the potential of three-dimensional (3D) line ratio diagnostic diagrams. We introduce a specific set of 3D diagrams, the ZQE diagrams, which separate the oxygen abundance and the ionisation parameter of H II region-like spectra, and which also enable us to probe the excitation mechanism of the gas. By examining these new 3D spaces interactively, we define a new set of 2D diagnostics, the ZE diagnostics, which can provide the metallicity of objects excited by hot young stars, and which cleanly separate H II region-like objects from the different classes of AGNs. We show that these ZE diagnostics are consistent with the key log[N II]/Hα vs. log[O III]/Hβ diagnostic currently used by the community. They also have the advantage of attaching a probability that a given object belongs to one class or to the other. Finally, we discuss briefly why ZQE diagrams can provide a new way to differentiate and study the different classes of AGNs in anticipation of a dedicated follow-up study.

We present integral field unit (IFU) spectroscopy and self-consistent photoionisation modelling for a sample of four southern Galactic planetary nebulae (PNe) with supposed weak emission-line (WEL) central stars. The Wide Field Spectrograph (WiFeS) on the ANU 2.3 m telescope has been used to provide IFU spectroscopy for NGC 3211, NGC 5979, My 60, and M 4-2 covering the spectral range of 3400-7000Å. All objects are high excitation non-Type I PNe, with strong He II emission, strong [Ne V] emission, and weak low-excitation lines. They all appear to be predominantly optically-thin nebulae excited by central stars with T eff > 10 5 K. Three PNe of the sample have central stars which have been previously classified as weak emission-line stars (WELS), and the fourth also shows the characteristic recombination lines of a WELS. However, the spatially-resolved spectroscopy shows that rather than arising in the central star, the C IV and N III recombination line emission is distributed in the nebula, and in some cases concentrated in discrete nebular knots. This may suggest that the WELS classification is spurious, and that, rather, these lines arise from (possibly chemically enriched) pockets of nebular gas. Indeed, from careful background subtraction we were able to identify three of the sample as being hydrogen rich O(H)-Type. We have constructed fully self-consistent photoionization models for each object. This allows us to independently determine the chemical abundances in the nebulae, to provide new model-dependent distance estimates, and to place the central stars on the H-R diagram. All four PNe have similar initial mass (1.5 < M/M ⊙ < 2.0) and are at a similar evolutionary stage.

We have studied the chemistry of the molecular gas in evolved planetary nebulae. Three pseudo‐time‐dependent gas‐phase models have been constructed for dense (104–105 cm−3) and cool (T∼15 K) clumpy envelopes of the evolved nebulae NGC 6781, M4‐9 and NGC 7293. The three nebulae are modelled as carbon‐rich stars evolved from the asymptotic giant branch to the late planetary nebula phase. The clumpy neutral envelopes are subjected to ultraviolet radiation from the central star and X‐rays that enhance the rate of ionization in the clumps. With the ionization rate enhanced by four orders of magnitude over that of the ISM, we find that resultant abundances of the species HCN, HNC, HC3N and SiC2 are in good agreement with observations, while those of CN, HCO+, CS and SiO are in rough agreement. The results indicate that molecular species such as CH, CH2, CH2+, HCl, OH and H2O are anticipated to be highly abundant in these objects.

We discuss the classification and orientation of planetary nebulae that interact with the interstellar medium throughout the Milky Way. A sample of 117 confirmed interacting planetary nebulae is used for this purpose. Our results indicate that the majority of interacting objects are located close to the Galactic plane, and ∼77% of them are located inside the Galactic thin disk. One third of the sample is less than 100 parsec from the Galactic plane and thus may interact with molecular and cold neutral clouds. There is a tendency for the planetary nebula interaction region to be parallel to the Galactic plane. We found that ∼73% of interacting planetary nebulae have inclination angles (defined as the angles that join the planetary nebula centroid and the interaction area or bow shock with the Galactic plane) larger than 45 • and ∼38% larger than 70 • , which highlights the possible effect of interstellar magnetic fields. While it is sometime believed that the interaction preferentially occurs in old planetary nebulae, our analysis indicates that the majority of observed planetary nebulae are in the mid stage of their evolution. The mean inclination angle, Galactic height, linear size, and dynamical age are estimated for each stage of interaction. The results indicate strong correlations between the mean inclination angle and the above parameters.

In this paper we describe integral field spectroscopic observations of four southern Galactic Planetary Nebulae (PNe), M3-4, M3-6, Hen2-29 and Hen2-37 covering the spectral range; 3400-7000Å. We derive the ionisation structure, the physical conditions, the chemical compositions and the kinematical characteristics of these PNe and find good agreement with previous studies that relied upon the long-slit technique in their co-spatial area. From their chemical compositions as well as their spatial and kinematic characteristics, we determined that Hen2-29 is of the Peimbert Type I (He and N rich), while the other three are of Type II. The strength of the nebular He II line reveals that M3-3, Hen2-29 and Hen2-37 are of mid to high excitation classes while M3-6 is a low excitation planetary nebula (PN). A series of emission-line maps extracted from the data cubes were constructed for each PN to describe its overall structure. These show remarkable morphological diversity. Spatially resolved spectroscopy of M3-6, shows that the recombination lines of C II, C III, C IV and N III are of nebular origin, rather than arising from the central star as had been previously proposed. This result increases doubts regarding the weak emission-line star (WELS) classification raised by Basurah et al. (2016). In addition, they reinforce the probability that most genuine cases of WELS are arise from irradiation effects in close binary central stars (Miszalski 2009).

We describe high spectral resolution, high dynamic range integral field spectroscopy of IC418 covering the spectral range 3300-8950Å and compare with earlier data. We determine line fluxes, derive chemical abundances, provide a spectrum of the central star, and determine the shape of the nebular continuum. Using photoionisation models, we derive the reddening function from the nebular continuum and recombination lines. The nebula has a very high inner ionisation parameter. Consequently, radiation pressure dominates the gas pressure and dust absorbs a large fraction of ionising photons. Radiation pressure induces increasing density with radius. From a photoionisation analysis we derive central star parameters; log T ef f = 4.525K, log L * /L = 4.029, log g = 3.5 and using stellar evolutionary models we estimate an initial mass of 2.5 < M/M < 3.0. The inner filamentary shell is shocked by the rapidly increasing stellar wind ram pressure, and we model this as an externally photoionised shock. In addition, a shock is driven into the pre-existing Asymptotic Giant Branch stellar wind by the strong D-Type ionisation front developed at the outer boundary of the nebula. From the dynamics of the inner mass-loss bubble, and from stellar evolutionary models we infer that the nebula became ionised in the last 100 − 200 yr, but evolved structurally during the ∼ 2000 yr since the central star evolved off the AGB. The estimated current mass loss rate (Ṁ = 3.8 × 10 −8 M yr −1 ) and terminal velocity (v ∞ ∼ 450 km/s) is sufficient to excite the inner mass-loss bubble. While on the AGB, the central star lost mass atṀ = 2.1 × 10 −5 M yr −1 with outflow velocity ∼ 14 km/s.

No abstract