Can mid-infrared spectral energy distribution quantitatively trace protoplanetary disk evolution?
Mingchao Liu, Jinhua He, Zhen Guo, Jixing Ge, Yuping Tang
arXiv:2404.11048v1 Announce Type: new
Abstract: Infrared (IR) spectral energy distribution (SED) is the major tracer of protoplanetary disks. It was recently proposed to use the mid-IR (MIR) SED slope $alpha$ defined between 2-24$mu$m as a potential quantitative tracer of disk age. We critically examine the viability of this idea and confront it with additional statistics of IR luminosities and SED shapes. We point out that, because the statistical properties of most of the complicated physical factors involved in disk evolution are still poorly understood in a quantitative sense, the only viable way is to assume them to be random so that an idealized `average disk’ can be defined, which allows the $alpha$ histogram to trace its age. We confirm that the statistics of the zeroth order (luminosity), first order (slope $alpha$) and second order characteristics (concavity) of the observed MIR SED indeed carry useful information upon the evolutionary processes of the `average disk’ and provide useful constraints to future disk population synthesis modeling. We also demonstrate that intrinsic diversities in MIR SED shapes and luminosities are always large at the level of individual stars so that the application of the evolutionary path of the `average disk’ to individual stars must be done with care. The data of all curves in plots are provided on GitHub.arXiv:2404.11048v1 Announce Type: new
Abstract: Infrared (IR) spectral energy distribution (SED) is the major tracer of protoplanetary disks. It was recently proposed to use the mid-IR (MIR) SED slope $alpha$ defined between 2-24$mu$m as a potential quantitative tracer of disk age. We critically examine the viability of this idea and confront it with additional statistics of IR luminosities and SED shapes. We point out that, because the statistical properties of most of the complicated physical factors involved in disk evolution are still poorly understood in a quantitative sense, the only viable way is to assume them to be random so that an idealized `average disk’ can be defined, which allows the $alpha$ histogram to trace its age. We confirm that the statistics of the zeroth order (luminosity), first order (slope $alpha$) and second order characteristics (concavity) of the observed MIR SED indeed carry useful information upon the evolutionary processes of the `average disk’ and provide useful constraints to future disk population synthesis modeling. We also demonstrate that intrinsic diversities in MIR SED shapes and luminosities are always large at the level of individual stars so that the application of the evolutionary path of the `average disk’ to individual stars must be done with care. The data of all curves in plots are provided on GitHub.