An HST Survey of Protostellar Outflow Cavities: Does Feedback Clear Envelopes?

Abstract We study protostellar envelope and outflow evolution using Hubble Space Telescope NICMOS or WFC3 images of 304 protostars in the Orion molecular clouds. These near-IR images resolve structures in the envelopes delineated by the scattered light of the central protostars with 80 au resolution...

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Bibliographic Details
Published in:The Astrophysical journal 2021-04, Vol.911 (2), p.153
Main Authors: Habel, Nolan M., Thomas Megeath, S., Jon Booker, Joseph, Fischer, William J., Kounkel, Marina, Poteet, Charles, Furlan, Elise, Stutz, Amelia, Manoj, P., Tobin, John J., Nagy, Zsofia, Pokhrel, Riwaj, Watson, Dan
Format: Article
Language:English
Subjects:
Algorithms
Astrophysics
Clearing
Early stellar evolution
Edge detection
Holes
Hubble Space Telescope
Infrared imaging
Molecular clouds
Morphology
Near infrared astronomy
Outflow
Point sources
Polls & surveys
Protostars
Radiative transfer
Space telescopes
Star & galaxy formation
Star formation
Stellar evolution
Stellar feedback
Stellar jets
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Summary:Abstract We study protostellar envelope and outflow evolution using Hubble Space Telescope NICMOS or WFC3 images of 304 protostars in the Orion molecular clouds. These near-IR images resolve structures in the envelopes delineated by the scattered light of the central protostars with 80 au resolution, and they complement the 1.2 μ m to 870 μ m spectral energy distributions (SEDs) obtained with the Herschel Orion Protostar Survey program. Based on their 1.60 μ m morphologies, we classify the protostars into five categories: nondetections, point sources without nebulosity, bipolar cavity sources, unipolar cavity sources, and irregulars. We find point sources without associated nebulosity are the most numerous, and show through monochromatic Monte Carlo radiative transfer modeling that this morphology occurs when protostars are observed at low inclinations or have low envelope densities. We also find that the morphology is correlated with the SED-determined evolutionary class, with Class 0 protostars more likely to be nondetections, Class I protostars to show cavities, and flat-spectrum protostars to be point sources. Using an edge detection algorithm to trace the projected edges of the cavities, we fit power laws to the resulting cavity shapes, thereby measuring the cavity half-opening angles and power-law exponents. We find no evidence for the growth of outflow cavities as protostars evolve through the Class I protostar phase, in contradiction with previous studies of smaller samples. We conclude that the decline of mass infall with time cannot be explained by the progressive clearing of envelopes by growing outflow cavities. Furthermore, the low star formation efficiency inferred for molecular cores cannot be explained by envelope clearing alone.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/abded8