Debris disks around stars in the NIKA2 era

TL;DR

This study uses NIKA2 observations to analyze debris disks around stars, revealing a spectral inversion in dust emission between millimeter and submillimeter wavelengths, and proposing a model involving two dust grain populations.

Contribution

First demonstration of spectral inversion in debris disks using millimeter observations, modeling dust grain size distributions with two populations to explain the spectral behavior.

Findings

Spectral index consistent with Rayleigh-Jeans regime at millimeter wavelengths.

Spectral inversion observed in two debris disks, not in the youngest one.

Model successfully explains spectral inversion with two dust grain populations.

Abstract

The new NIKA2 camera at the IRAM 30m radiotelescope was used to observe three known debris disks in order to constrain the SED of their dust emission in the millimeter wavelength domain. We have found that the spectral index between the two NIKA2 bands (1mm and 2mm) is consistent with the Rayleigh-Jeans regime (lambda^{-2}), unlike the steeper spectra (lambda^{-3}) measured in the submillimeter-wavelength domain for two of the three disks $-$ around the stars Vega and HD107146. We provide a succesful proof of concept to model this spectral inversion in using two populations of dust grains, those smaller and those larger than a grain radius a0 of 0.5mm. This is obtained in breaking the slope of the size distribution and the functional form of the absorption coefficient of the standard model at a0. The third disk - around the star HR8799 - does not exhibit this spectral inversion but is also the youngest.