The relation between Zanstra temperature and morphology in planetary nebulae

Abstract

We have created a master list of Zanstra temperatures for 373 galactic planetary nebulae based upon a compilation of 1575 values taken from the published literature. These are used to evaluate mean trends in temperature for differing nebular morphologies. Among the most prominent results of this analysis is the tendency for η=TZ(He ii)/TZ(He i) to increase with nebular radius, a trend which is taken to arise from the evolution of shell optical depths. We find that as many as 87 per cent of nebulae may be optically thin to H ionizing radiation where radii exceed ∼0.16 pc. We also note that the distributions of values η and TZ(He ii) are quite different for circular, elliptical and bipolar nebulae. A comparison of observed temperatures with theoretical H‐burning tracks suggests that elliptical and circular sources arise from progenitors with mean mass 〈MPG〉≅ 1 M⊙ (although the elliptical progenitors are probably more massive). Higher‐temperature elliptical sources are likely to derive from progenitors with mass ≅2 M⊙, however, implying that these nebulae (at least) are associated with a broad swathe of progenitor masses. Such a conclusion is also supported by trends in mean galactic latitude. It is found that higher‐temperature elliptical sources have much lower mean latitudes 〈b〉 than those with smaller TZ(He ii), a trend which is explicable where there is an increase in 〈MPG〉 with increasing TZ(He ii). This latitude–temperature variation also applies for most other sources. Bipolar nebulae appear to have mean progenitor masses ≅2.5 M⊙, whilst jets, Brets and other highly collimated outflows are associated with progenitors at the other end of the mass range (〈MPG〉∼ 1 M⊙). Indeed it is possible, given their large mean latitudes and low peak temperatures, that the latter nebulae are associated with the lowest‐mass progenitors of all. The present results appear fully consistent with earlier analyses based upon nebular scale heights, shell abundances and the relative proportions of differing morphologies, and offer further evidence for a link between progenitor mass and morphology.

The Detection of C60 in the Well-Characterized Planetary Nebula M1-11

“…Indeed, M1-11 has a cool central star (29,300 K;Phillips 2003), and the nebula is relatively compact, with a size of 6 in diameter in Hα emission, and it appears to be a very young object (∼1000 yr after leaving the AGB phase; this work). Henry et al (2010) measured the C abundance in M1-11 using recombination lines (RLs) and the O abundance with collisionally excited lines (CELs; number density ratio of C/O = 79.4).…”

Near-Infrared Pah Features in Galactic Planetary Nebulae

“…We use T eff as an indicator of the PN evolution as used for post-AGB stars (Sloan et al, 2007;Matsuura et al, 2014). The effective temperatures are obtained from literature (Phillips, 2003;Lumsden et al, 2001;Preite-Martinez et al, 1989, 1991.…”

IC 4406: A Radio‐Infrared View

“…The IRAS color-corrected data were taken from Sahai et al 1991. In our modeling we have assumed a central star temperature of 96,800 K (Phillips 2003), a distance of 1.6 kpc, and a luminosity of 170 L (Sahai et al 1991).…”

“…Values in the 400Y2000 cm À3 range have been estimated using several different optical and infrared lines, with values derived by [S ii] and [O iii] doublets matching around 540 cm À3 (Liu et al 2001;Wang et al 2004). Its central star has a He ii Zanstra temperature of 96,800 K (Phillips 2003), and its distance is probably around 1.6 kpc (Sahai et al 1991), although some authors claim it may be overestimated (O'Dell et al 2002). Gruenwald et al (1997) have modeled IC 4406 with a threedimensional photoionization code and fit many observed line intensities assuming there is a torus around the central star.…”