The highly reddened planetary nebula Abell 48 (PNG029.000.4) and its central star (CS) have been the subject of recent spectroscopic studies (Frew et al., 2013; Depew et al., 2011; Todt et al., 2013; Wachter et al., 2010). The CS of Abell48 has been classified as Wolf-Rayet [WN5] (Todt et al., 2013), where the square brackets distinguish it from the massive WN stars. Abell 48 was first identified as a planetary nebula (PN) by Abell (1955). However, its nature remains a source of controversy whether it is a massive ring nebula or a PN as previously identified. Recently, Wachter et al. (2010) described it as a spectral type of WN6 with a surrounding ring nebula. But, Todt et al. (2013) concluded from spectral analysis of the CS and the surrounding nebula that Abell 48 is rather a PN with a low-mass CS than a massive (Pop I) WN star. Previously, Todt et al. (2010) also associated the CS of PB8 with [WN/C] class. Furthermore, IC4663 is another PN found to possess a [WN] star (Miszalski et al., 2012).
A narrow-band H+[NII] image of Abell 48 obtained by Jewitt et al. (1986) first showed its faint double-ring morphology. Zuckerman & Aller (1986) identified it as a member of the elliptical morphological class. The H image obtained from the SuperCOSMOS Sky H Survey (Parker et al., 2005) shows that the angular dimensions of the shell are about 46 38 , and are used throughout this paper. The first integral field spectroscopy of Abell 48 shows the same structure in the H emission-line profile. But, a pair of bright point-symmetric regions is seen in [NII] (see Fig.2), which could be because of the N stratification layer produced by the photoionization process. A detailed study of the kinematic and ionization structure has not yet been carried out to date. This could be due to the absence of spatially resolved observations.
|PN||Date (UT)||range (Å)||Exp.(s)|
The main aim of this study is to investigate whether the [WN] model atmosphere from Todt et al. (2013) of a low-mass star can reproduce the ionization structure of a PN with the features like Abell 48. We present integral field unit (IFU) observations and a three-dimensional photoionization model of the ionized gas in Abell 48. The paper is organized as follows. Section 2 presents our new observational data. In Section 3 we describe the morpho-kinematic structure, followed by an empirical analysis in Section 4. We describe our photoionization model and the derived results in Sections 5 and 6, respectively. Our final conclusion is stated in Section7.