The Galactic Disk Distribution of Planetary Nebulae with Warm Dust Emission Features: II

Abstract

Can the distribution of warm-dust compositions in IR-bright galactic disk PNe be linked to the underlying stellar population? The PNe with warm dust emission represent a homogeneous population, which is presumably young and minimally affected by a possible dependence of PN lifetime on progenitor mass. The sample in paper I thus allows testing the predictions of single star evolution, through a comparison with synthetic distributions and under the assumption that tip-of-the-AGB and PN statistics are similar. We construct a schematic model for AGB evolution (adapted from Groenewegen & de Jong 1993), whose free-parameters are calibrated with the luminosity function (LF) of C stars in the LMC, the initial-final mass relation, and the range of PN compositions. The observed metallicity gradient and distribution of star forming regions with galactocentric radius (Bronfman et al. 2000) allow us to synthesise the galactic disk PN progenitor population. We find the fraction of O-rich PNe, f(O), is a tight constraint on AGB parameters. For our best model, a minimum PN progenitor mass Mmin=1Msun predicts that about 50% of all young PNe should be O-rich, compared to an observed fraction of 22%; thus Mmin=1.2Msun, at a 2sigma confidence level. By contrast, current AGB models for single stars can account neither for the continuous range of N enrichment (Leisy & Dennefeld 1996), nor for the observation that the majority of very C-rich PNe have Peimbert type I (paper I). f(O) is thus an observable much easier to model. The decrease in f(O) with galactocentric radius, as reported in paper I, is a strong property of the synthetic distribution, independent of Mmin. This trend reflects the sensitivity of the surface temperature of AGB stars and of the core mass at the first thermal pulse to the galactic metallicity gradient.

accepted by MNRAS

References in corpus (4)

• The Accretion of Brown Dwarfs and Planets by Giant Stars -- I. AGB Stars
• A New Look At Carbon Abundances In Planetary Nebulae. IV. Implications For Stellar Nucleosynthesis
• The Galactic Disk Distribution of Planetary Nebulae With Warm Dust Emission Features: I
• The Galactic Disk Distribution of Planetary Nebulae with Warm Dust Emission Features: II

Cited by in corpus (8)

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• Interstellar 12C/13C ratios through CH+ ll 3957,4232 absorption in local clouds: incomplete mixing in the ISM
• The Galactic Disk Distribution of Planetary Nebulae With Warm Dust Emission Features: I
• 8-13um Dust Emission Features in Galactic Bulge Planetary Nebulae
• The Galactic Disk Distribution of Planetary Nebulae with Warm Dust Emission Features: II
• The Mid-Infrared Colours of Galactic Bulge, Disk and Magellanic Planetary Nebulae