2021A&A...648A.100B


Query : 2021A&A...648A.100B

2021A&A...648A.100B - Astronomy and Astrophysics, volume 648A, 100-100 (2021/4-1)

Fragmentation in the massive G31.41+0.31 protocluster.

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.

Abstract (from CDS):


Context. ALMA observations at 1.4 mm and ∼0.2" (∼750au) 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 3.5mm that achieved angular resolutions of ∼0.1" (∼375au) and ∼0.075" (∼280au), respectively. VLA observations at 7 mm and 1.3 cm at even higher angular resolution, ∼0.05" (∼190au) and ∼0.07" (∼260au), 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 3.5mm, are ∼400-500au; their masses range from ∼15 to ∼26M; and their number densities are several 109cm–3. Sources A and B, located closer to the center of the core and separated by ∼750au, 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.

Abstract Copyright: © ESO 2021

Journal keyword(s): ISM: individual objects: G31.41+0.31 - stars: formation - stars: massive - techniques: interferometric

VizieR on-line data: <Available at CDS (J/A+A/648/A100): list.dat fits/*>

Status at CDS : Examining the need for a new acronym.

Simbad objects: 8

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Number of rows : 8
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 3C 286 Sy1 13 31 08.2883506368 +30 30 32.960091564   17.51 17.25     ~ 4369 2
2 QSO B1730-130 QSO 17 33 02.70578907 -13 04 49.5482119   18 19.50 18.78 17.39 ~ 1144 1
3 NAME Sgr B2 (North) Rad 17 47 20.2 -28 22 21           ~ 677 1
4 4C 09.57 BLL 17 51 32.81857326 +09 39 00.7284066   17.46 16.78 15.57   ~ 953 1
5 IRAS 18449-0115 cor 18 47 34.27 -01 12 43.2           ~ 390 1
6 NVSS J185146+003532 Rad 18 51 46.72295 +00 35 32.3649           ~ 84 1
7 W 51 SNR 19 23 50 +14 06.0           ~ 1283 1
8 QSO B1921-293 BLL 19 24 51.05595254 -29 14 30.1210248   18.71 18.21 15.07   ~ 878 1

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