Constraining Planetary Gas Accretion Rate from H{\alpha} Linewidth and Intensity: Case of PDS 70 b and c

TL;DR

This paper uses radiation-hydrodynamic models to analyze Hα emission line data from protoplanets PDS 70 b and c, aiming to better constrain their gas accretion rates and masses, highlighting the potential of high-resolution spectral imaging.

Contribution

It applies advanced shock-heated accretion flow models to interpret Hα linewidths and intensities, refining estimates of protoplanetary accretion parameters.

Findings

Hα linewidths and intensities can significantly narrow down accretion rate estimates.

Current spectral resolution limits definitive conclusions, but high-resolution imaging shows promise.

Models suggest possible ranges for protoplanet masses and accretion rates.

Abstract

Recent observations of protoplanets embedded in circumstellar disks have shed light on the planet formation process. In particular, detection of hydrogen Balmer-line (H{\alpha}) emission gives direct constraints on late-stage accretion onto gas giants. Very recently Haffert et al. (2019) measured the spectral line-widths, in addition to intensities, of H{\alpha} emission from the two protoplanets orbiting PDS 70. Here, we study these protoplanets by applying radiation-hydrodynamic models of the shock-heated accretion flow onto protoplanets that Aoyama et al. (2018) has recently developed. As a result, we demonstrate that H{\alpha} line-widths combined with intensities lead to narrowing down the possible ranges of the protoplanetary accretion rate and/or mass significantly. While the current spectral resolution is not high enough to derive a definite conclusion regarding their accretion process, high-resolution spectral imaging of growing protoplanets is highly promising.