ALMA and Herschel Observations of the Prototype Dusty and Polluted White Dwarf G29-38

TL;DR

This study used ALMA and Herschel observations to search for cold dust around the white dwarf G29-38, finding no emission and constraining the mass and location of potential parent bodies, thus informing models of planetary debris evolution.

Contribution

First combined ALMA and Herschel observations of a dusty white dwarf, providing constraints on cold dust and parent body populations around G29-38.

Findings

No emission sources detected down to L_IR/L ~ 1e-4.

Cold dust masses greater than 1e24 - 1e25 g are ruled out.

Results support models of long-term collisional evolution in planetesimal disks.

Abstract

ALMA Cycle 0 and Herschel PACS observations are reported for the prototype, nearest, and brightest example of a dusty and polluted white dwarf, G29-38. These long wavelength programs attempted to detect an outlying, parent population of bodies at 1-100 AU, from which originates the disrupted planetesimal debris that is observed within 0.01 AU and which exhibits L_IR/L = 0.039. No associated emission sources were detected in any of the data down to L_IR/L ~ 1e-4, generally ruling out cold dust masses greater than 1e24 - 1e25 g for reasonable grain sizes and properties in orbital regions corresponding to evolved versions of both asteroid and Kuiper belt analogs. Overall, these null detections are consistent with models of long-term collisional evolution in planetesimal disks, and the source regions for the disrupted parent bodies at stars like G29-38 may only be salient in exceptional circumstances, such as a recent instability. A larger sample of polluted white dwarfs, targeted with the full ALMA array, has the potential to unambiguously identify the parent source(s) of their planetary debris.