The Evolution of Far-infrared CO Emission from Protostars
Abstract
We investigate the evolution of far-IR CO emission from protostars observed with Herschel/PACS for 50 sources from the combined sample of HOPS and DIGIT Herschel key programs. From the uniformly sampled spectral energy distributions, whose peaks are well sampled, we computed the L_(bol), T_(bol), and L_(bol)/L_(smm) for these sources to search for correlations between far-IR CO emission and protostellar properties. We find a strong and tight correlation between far-IR CO luminosity (L_(CO)^(fir)) and the bolometric luminosity L_(bol) of the protostars with L_(CO)^(fir) α L_(bol)^(0.7). We, however, do not find a strong correlation between L_(CO)^(fir) and protostellar evolutionary indicators, T_(bol) and L(bol)/L(smm). FIR CO emission from protostars traces the currently shocked gas by jets/outflows, and far-IR CO luminosity, L_(CO)^(fir), is proportional to the instantaneous mass-loss rate, M_(out). The correlation between L_(CO)^(fir) and L_(bol), then, is indicative of instantaneous M_(out) tracking instantaneous M_(acc). The lack of a correlation between L_(CO)^(fir) and evolutionary indicators T_(bol) and L_(bol)/L_(smm) suggests that M_(out) and, therefore, M_(acc) do not show any clear evolutionary trend. These results are consistent with mass accretion/ejection in protostars being episodic. Taken together with the previous finding that the time-averaged mass-ejection/accretion rate declines during the protostellar phase, our results suggest that the instantaneous accretion/ejection rate of protostars is highly time variable and episodic, but the amplitude and/or frequency of this variability decreases with time such that the time-averaged accretion/ejection rate declines with system age.
Additional Information
© 2016. The American Astronomical Society. Received 2016 May 16; revised 2016 August 11; accepted 2016 August 13; published 2016 October 27. Support for this work, part of the Herschel Open Time Key Project Program, was provided by NASA through an award issued by the Jet Propulsion Laboratory, California Institute of Technology. This work was supported by NSF grant AST-1109116 to the University of Texas at Austin. This work is based on observations made with the Herschel Space Observatory, a European Space Agency Cornerstone Mission with significant participation by NASA; it is also on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology (Caltech), under a contract with NASA. We also include data from the Atacama Pathfinder Experiment, a collaboration between the Max-Planck Institut für Radio-astronomie, the European Southern Observatory, and the Onsala Space Observatory. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/Caltech, funded by NASA and the NSF.Attached Files
Published - Manoj_2016_ApJ_831_69.pdf
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Additional details
- Eprint ID
- 71559
- Resolver ID
- CaltechAUTHORS:20161027-141753498
- NASA/JPL/Caltech
- AST-1109116
- NSF
- Created
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2016-10-28Created from EPrint's datestamp field
- Updated
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2021-11-11Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)