Details

Autor(en) / Beteiligte

• Hsieh, Tien-Hao
• Murillo, Nadia M.
• Belloche, Arnaud
• Hirano, Naomi
• Walsh, Catherine
• Dishoeck, Ewine F. van
• Lai, Shih-Ping

Titel

Probing Episodic Accretion in Very Low Luminosity Objects

Ist Teil von

• The Astrophysical journal, 2018-02, Vol.854 (1), p.15

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2018

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Episodic accretion has been proposed as a solution to the long-standing luminosity problem in star formation; however, the process remains poorly understood. We present observations of line emission from N2H+ and CO isotopologues using the Atacama Large Millimeter/submillimeter Array (ALMA) in the envelopes of eight very low luminosity objects (VeLLOs). In five of the sources the spatial distribution of emission from N2H+ and CO isotopologues shows a clear anticorrelation. It is proposed that this is tracing the CO snow line in the envelopes: N2H+ emission is depleted toward the center of these sources, in contrast to the CO isotopologue emission, which exhibits a peak. The positions of the CO snow lines traced by the N2H+ emission are located at much larger radii than those calculated using the current luminosities of the central sources. This implies that these five sources have experienced a recent accretion burst because the CO snow line would have been pushed outward during the burst because of the increased luminosity of the central star. The N2H+ and CO isotopologue emission from DCE161, one of the other three sources, is most likely tracing a transition disk at a later evolutionary stage. Excluding DCE161, five out of seven sources (i.e., ∼70%) show signatures of a recent accretion burst. This fraction is larger than that of the Class 0/I sources studied by Jørgensen et al. and Frimann et al., suggesting that the interval between accretion episodes in VeLLOs is shorter than that in Class 0/I sources.