The Astrophysical Journal (Jan 2023)

300: An ACA 870 μm Continuum Survey of Orion Protostars and Their Evolution

  • Samuel Federman,
  • S. Thomas Megeath,
  • John J. Tobin,
  • Patrick D. Sheehan,
  • Riwaj Pokhrel,
  • Nolan Habel,
  • Amelia M. Stutz,
  • William J. Fischer,
  • Lee Hartmann,
  • Thomas Stanke,
  • Mayank Narang,
  • Mayra Osorio,
  • Prabhani Atnagulov,
  • Rohan Rahatgaonkar

DOI
https://doi.org/10.3847/1538-4357/ac9f4b
Journal volume & issue
Vol. 944, no. 1
p. 49

Abstract

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We present an 870 μ m continuum survey of 300 protostars from the Herschel Orion Protostar Survey using the Atacama Compact Array (ACA). These data measure protostellar flux densities on envelope scales ≤8000 au (20″) and resolve the structure of envelopes with 1600 au (4″) resolution, a factor of 3–5 improvement in angular resolution over existing single-dish 870 μ m observations. We compare the ACA observations to Atacama Large Millimeter/submillimeter Array 12 m array observations at 870 μ m with ∼0.″1 (40 au) resolution. Using the 12 m data to measure the fluxes from disks and the ACA data within 2500 au to measure the combined disk plus envelope fluxes, we calculate the 12 m/ACA 870 μ m flux ratios. Our sample shows a clear evolution in this ratio. Class 0 protostars are mostly envelope-dominated with ratios <0.5. In contrast, Flat Spectrum protostars are primarily disk-dominated with ratios near 1, although with a number of face-on protostars dominated by their envelopes. Class I protostars span the range from envelope to disk-dominated. The increase in ratio is accompanied by a decrease in the envelope fluxes and estimated mass infall rates. We estimate that 80% of the mass is accreted during the envelope-dominated phase. We find that the 12 m/ACA flux ratio is an evolutionary indicator that largely avoids the inclination and foreground extinction dependence of spectral energy distribution-based indicators.

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