A Dust-Scattering Model for M1-92: A Revised Estimate of the Mass Distribution and Inclination

TL;DR

This paper develops a dust-scattering radiative transfer model to analyze the structure of the bipolar preplanetary nebula M1-92, revealing a density cutoff likely caused by a binary companion, aiding future dynamical studies.

Contribution

It introduces an efficient single-scattering radiative transfer model with double-scattering corrections for studying PPNe dust distributions.

Findings

M1-92 has a radial density cutoff in its equatorial torus.

The nebula's orientation and dust profile were inferred from HST data.

Binary interaction likely influenced the nebula's structure.

Abstract

Preplanetary nebulae (PPNe) are formed from mass-ejecting late-stage AGB stars. Much of the light from the star gets scattered or absorbed by dust particles, giving rise to the observed reflection nebula seen at visible and near-IR wavelengths. Precursors to planetary nebulae (PNe), PPNe generally have not yet undergone any ionization by UV radiation from the still-buried stellar core. Bipolar PPNe are a common form of observed PPNe. This study lays the groundwork for future dynamical studies by reconstructing the dust density distribution of a particularly symmetric bipolar PPN, M1-92 (Minkowski's Footprint, IRAS 19343$+$2926). For this purpose, we develop an efficient single-scattering radiative transfer model with corrections for double-scattering. Using a V-band image from the Hubble Space Telescope (HST), we infer the dust density profile and orientation of M1-92. These results indicate that M1-92's slowly expanding equatorial torus exhibits an outer radial cutoff in its density, which implicates the influence of a binary companion during the formation of the nebula.