Universität zu Köln

Beltran, M. T., Rivilla, V. M., Cesaroni, R., Maud, L. T., Galli, D., Moscadelli, L., Lorenzani, A., Ahmadi, A., Beuther, H., Csengeri, T., Etoka, S., Goddi, C., Klaassen, P. D., Kuiper, R., Kumar, M. S. N., Peters, T., Sanchez-Monge, A., Schilke, P., van der Tak, F., Vig, S. and Zinnecker, H. (2021). Fragmentation in the massive G31.41+0.31 protocluster. Astron. Astrophys., 648. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Context. ALMA observations at 1.4 mm and similar to 0.'' 2 (similar to 750 au) angular resolution of the Main core in the high-mass star-forming region G31.41+0.31 have revealed a puzzling scenario. On the one hand, the continuum emission looks very homogeneous and the core appears to undergo solid-body rotation, suggesting a monolithic core stabilized by the magnetic field; on the other hand, rotation and infall speed up toward the core center, where two massive embedded free-free continuum sources have been detected, pointing to an unstable core having undergone fragmentation. Aims. To establish whether the Main core is indeed monolithic or if its homogeneous appearance is due to a combination of large dust opacity and low angular resolution, we carried out millimeter observations at higher angular resolution and different wavelengths. Methods. We carried out ALMA observations at 1.4 mm and 3.5 mm that achieved angular resolutions of similar to 0.'' 1 (similar to 375 au) and similar to 0.'' 075 (similar to 280 au), respectively. VLA observations at 7 mm and 1.3 cm at even higher angular resolution, similar to 0.'' 05 (similar to 190 au) and similar to 0.'' 07 (similar to 260 au), respectively, were also carried out to better study the nature of the free-free continuum sources detected in the core. Results. The millimeter continuum emission of the Main core has been clearly resolved into at least four sources, A, B, C, and D, within 1 '', indicating that the core is not monolithic. The deconvolved radii of the dust emission of the sources, estimated at 3.5 mm, are similar to 400-500 au; their masses range from similar to 15 to similar to 26 M-circle dot; and their number densities are several 10(9) cm(-3). Sources A and B, located closer to the center of the core and separated by similar to 750 au, are clearly associated with two free-free continuum sources, likely thermal radio jets, and are brightest in the core. The spectral energy distribution of these two sources and their masses and sizes are similar and suggest a common origin. Source C has not been detected at centimeter wavelengths, while source D has been clearly detected at 1.3 cm. Source D is likely the driving source of an E-W SiO outflow previously detected in the region, which suggests that the free-free emission might be coming from a radio jet. Conclusions. The observations have confirmed that the Main core in G31 is collapsing, that it has undergone fragmentation, and that its homogeneous appearance previously observed at short wavelengths is a consequence of both high dust opacity and insufficient angular resolution. The low level of fragmentation together with the fact that the core is moderately magnetically supercritical, suggests that G31 could have undergone a phase of magnetically regulated evolution characterized by a reduced fragmentation efficiency, eventually leading to the formation of a small number of relatively massive dense cores.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Beltran, M. T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Rivilla, V. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Cesaroni, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Maud, L. T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Galli, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Moscadelli, L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lorenzani, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ahmadi, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Beuther, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Csengeri, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Etoka, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Goddi, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Klaassen, P. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kuiper, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kumar, M. S. N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Peters, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sanchez-Monge, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schilke, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED van der Tak, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Vig, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Zinnecker, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-604782
DOI:	10.1051/0004-6361/202040121
Journal or Publication Title:	Astron. Astrophys.
Volume:	648
Date:	2021
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language ROTATING MAGNETIZED CLOUDS; COMPLEX ORGANIC-MOLECULES; STAR-FORMATION; COLLAPSE; CORES; EVOLUTION; DENSITY; FIELDS; ACCRETION; EMISSION Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/60478