The chemical inventory of the planet-hosting disk PDS 70. (arXiv:2101.08369v1 [astro-ph.EP])

The chemical inventory of the planet-hosting disk PDS 70. (arXiv:2101.08369v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Facchini_S/0/1/0/all/0/1">Stefano Facchini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Teague_R/0/1/0/all/0/1">Richard Teague</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bae_J/0/1/0/all/0/1">Jaehan Bae</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Benisty_M/0/1/0/all/0/1">Myriam Benisty</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Keppler_M/0/1/0/all/0/1">Miriam Keppler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Isella_A/0/1/0/all/0/1">Andrea Isella</a>

As host to two accreting planets, PDS 70 provides a unique opportunity to
probe the chemical complexity of atmosphere-forming material. We present ALMA
Band 6 observations of the PDS~70 disk and report the first chemical inventory
of the system. With a spatial resolution of $0.4”-0.5”$ ( $sim50,$au), 12
species are detected, including CO isotopologues and formaldehyde, small
hydrocarbons, HCN and HCO$^+$ isotopologues, and S-bearing molecules. SO and
CH$_3$OH are not detected. All lines show a large cavity at the center of the
disk, indicative of the deep gap carved by the massive planets. The radial
profiles of the line emission are compared to the (sub-)mm continuum and
infrared scattered light intensity profiles. Different molecular transitions
peak at different radii, revealing the complex interplay between density,
temperature and chemistry in setting molecular abundances. Column densities and
optical depth profiles are derived for all detected molecules, and upper limits
obtained for the non detections. Excitation temperature is obtained for
H$_2$CO. Deuteration and nitrogen fractionation profiles from the hydro-cyanide
lines show radially increasing fractionation levels. Comparison of the disk
chemical inventory to grids of chemical models from the literature strongly
suggests a disk molecular layer hosting a carbon to oxygen ratio C/O$>$1, thus
providing for the first time compelling evidence of planets actively accreting
high C/O ratio gas at present time.

As host to two accreting planets, PDS 70 provides a unique opportunity to
probe the chemical complexity of atmosphere-forming material. We present ALMA
Band 6 observations of the PDS~70 disk and report the first chemical inventory
of the system. With a spatial resolution of $0.4”-0.5”$ ( $sim50,$au), 12
species are detected, including CO isotopologues and formaldehyde, small
hydrocarbons, HCN and HCO$^+$ isotopologues, and S-bearing molecules. SO and
CH$_3$OH are not detected. All lines show a large cavity at the center of the
disk, indicative of the deep gap carved by the massive planets. The radial
profiles of the line emission are compared to the (sub-)mm continuum and
infrared scattered light intensity profiles. Different molecular transitions
peak at different radii, revealing the complex interplay between density,
temperature and chemistry in setting molecular abundances. Column densities and
optical depth profiles are derived for all detected molecules, and upper limits
obtained for the non detections. Excitation temperature is obtained for
H$_2$CO. Deuteration and nitrogen fractionation profiles from the hydro-cyanide
lines show radially increasing fractionation levels. Comparison of the disk
chemical inventory to grids of chemical models from the literature strongly
suggests a disk molecular layer hosting a carbon to oxygen ratio C/O$>$1, thus
providing for the first time compelling evidence of planets actively accreting
high C/O ratio gas at present time.

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