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Published March 10, 2022 | Accepted Version + Published
Journal Article Open

New Constraints on Protoplanetary Disk Gas Masses in Lupus

Abstract

Gas mass is a fundamental quantity of protoplanetary disks that directly relates to their ability to form planets. Because we are unable to observe the bulk H₂ content of disks directly, we rely on indirect tracers to provide quantitative mass estimates. Current estimates for the gas masses of the observed disk population in the Lupus star-forming region are based on measurements of isotopologues of CO. However, without additional constraints, the degeneracy between H₂ mass and the elemental composition of the gas leads to large uncertainties in such estimates. Here, we explore the gas compositions of seven disks from the Lupus sample representing a range of CO-to-dust ratios. With Band 6 and 7 ALMA observations, we measure line emission for HCO⁺, HCN, and N₂H⁺. We find a tentative correlation among the line fluxes for these three molecular species across the sample, but no correlation with ¹³CO or submillimeter continuum fluxes. For the three disks where N₂H⁺ is detected, we find that a combination of high disk gas masses and subinterstellar C/H and O/H are needed to reproduce the observed values. We find increases of ∼10–100× previous mass estimates are required to match the observed line fluxes. This work highlights how multimolecular studies are essential for constraining the physical and chemical properties of the gas in populations of protoplanetary disks, and that CO isotopologues alone are not sufficient for determining the mass of many observed disks.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 October 27; revised 2022 January 31; accepted 2022 February 1; published 2022 March 21. We thank the anonymous referee for providing helpful feedback and suggestions. D.E.A. acknowledges support from the Virginia Initiative on Cosmic Origins (VICO) Postdoctoral Fellowship. L.I.C. gratefully acknowledges support from the David and Lucille Packard Foundation, the Virginia Space grant Consortium, Johnson and Johnson's WiSTEM2D Award, and NSF AAG grant number AST-1910106. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2019.1.01135.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. We also acknowledge the University of Virginia's Rivanna computing cluster, which was used to run some of the models used in this work. Software: Astropy (Astropy Collaboration et al. 2013; Price-Whelan et al. 2018), CASA (McMullin et al. 2007), linmix (https://github.com/jmeyers314/linmix), Matplotlib (Hunter2007), Numpy (van der Walt et al. 2011), parallel (Tange 2018).

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Published - Anderson_2022_ApJ_927_229.pdf

Accepted Version - 2202.00709.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 23, 2023