Detection of Irregular, Submillimeter Opaque Structures in the Orion Molecular Clouds: Protostars within 10,000 yr of Formation?

We wish to thank the anonymous referee for insightful comments and suggestions that improved the quality of this manuscript. The authors acknowledge Lee Hartmann for the useful discussions and many insightful comments. Support for Nicole Karnath was provided by the NSF through award SOSP AST-1519126 from the NRAO and by the NASA Origin of the Solar System program 13-OSS13-0094 (Megeath PI for both). This work made use of the SIMBAD database, the Vizier database, and the NASA Astrophysics Data System, funded by the National Aeronautics and Space Administration and the NSF. A.S. acknowledges funding through Fondecyt regular (project code 1180350), "Concurso Proyectos Internacionales de Investigacion" (project code PII20150171), and Chilean Centro de Excelencia en Astrofisica y Tecnologias Afines (CATA) BASAL grant AFB-170002. J.J.T. acknowledges funding from the National Science Foundation AST-1814762. Z.Y.L. is supported in part by NSF 1716259 and NASA 80NSSC18K1095. G.A., M.O., and A.K.D.-R. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the AYA2017-84390-C2-1-R grant (co-funded by FEDER) and through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofisica de Andalucia (SEV2017-0709). This research was conducted in part at the SOFIA Science Center, which is operated by the Universities Space Research Association under contract NNA17BF53C with the National Aeronautics and Space Administration. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2015.1.00041.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.