FRAGMENTATION OF MOLECULAR CLUMPS AND FORMATION OF A PROTOCLUSTER

Journal Article · Sun May 10 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/804/2/141· OSTI ID:22522431

Zhang, Qizhou; Lu, Xing ^[1]; Wang, Ke; Jiménez-Serra, Izaskun ^[2]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2. European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München (Germany)

Sufficiently massive clumps of molecular gas collapse under self-gravity and fragment to spawn a cluster of stars that have a range of masses. We investigate observationally the early stages of formation of a stellar cluster in a massive filamentary infrared dark cloud, G28.34+0.06 P1, in the 1.3 mm continuum and spectral line emission using the Atacama Large Millimeter/Submillimeter Array. Sensitive continuum data reveal further fragmentation in five dusty cores at a resolution of several 10{sup 3} AU. Spectral line emission from C{sup 18}O, CH{sub 3}OH, {sup 13}CS, H{sub 2}CO, and N{sub 2}D{sup +} is detected for the first time toward these dense cores. We found that three cores are chemically more evolved as compared with the other two; interestingly, though, all of them are associated with collimated outflows as suggested by evidence from the CO, SiO, CH{sub 3}OH, H{sub 2}CO, and SO emission. The parsec-scale kinematics in exhibit velocity gradients along the filament, consistent with accretion flows toward the clumps and cores. The moderate luminosity and the chemical signatures indicate that the five cores harbor low- to intermediate-mass protostars that likely become massive ones at the end of the accretion. Despite the fact that the mass limit reached by the dust continuum sensitivity is 30 times lower than the thermal Jeans mass, there is a lack of a distributed low-mass protostellar population in the clump. Our observations indicate that in a protocluster, low-mass stars form at a later stage after the birth of more massive protostars.

• OSTI ID: 22522431
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 804; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CARBON 13
CARBON MONOXIDE
CLOUDS
COMPARATIVE EVALUATIONS
FILAMENTS
FRAGMENTATION
GRAVITATION
JETS
LUMINOSITY
MASS
METHANOL
OXYGEN 18
PROTOSTARS
RESOLUTION
SENSITIVITY
SILICON OXIDES
STAR CLUSTERS
STAR EVOLUTION
STARS