2022A&A...657A..30T


Query : 2022A&A...657A..30T

2022A&A...657A..30T - Astronomy and Astrophysics, volume 657A, 30-30 (2022/1-1)

W51 North: A protocluster emerging out of a thermally inhibited fragmenting cloud.

TANG M., PALAU A., ZAPATA L.A. and QIN S.-L.

Abstract (from CDS):

Context. The fragmentation process in massive star-forming regions is one of the contemporary problems in astrophysics, and several physical processes have been proposed to control the fragmentation including turbulence, magnetic field, rotation, stellar feedback, and gravity. However, the fragmentation process has been poorly studied at small spatial scales well below 1000 AU. Aims. W51 IRS2 is a well-known massive star-forming region whose fragmentation properties have not been thoroughly investigated yet. We aim to use the Atacama Large Millimeter and Submillimeter Array (ALMA) high angular resolution data to identify the fragments in W51 IRS2 and to study the fragmentation properties on a spatial scale of 0.04'' (200 AU). Methods. We used ALMA data of W51 IRS2 from three projects, which give an angular resolution of 0.028'' (144 AU) at millimeter wavelengths. The continuum images reveal a significant substructure in an east-west ridge, where both W51 North and W51d2 are embedded. A spectral index map has been generated from the 3 and 1.3 mm high-resolution continuum images. We identified compact fragments by using uv-range constrained 1.3 mm continuum data. A mean surface density of companions (MSDC) analysis has been performed to study the separations between fragments. Results. A total number of 33 continuum sources are identified and 29 out of them are defined as fragments in the surveyed region.The MSDC analysis reveals two breaks corresponding to spatial scales of 1845 and 7346 AU, indicative of a two-level clustering phenomenon, along with a linear regime below 1845 AU, mostly associated with W51 North, whose slope is consistent with the slope for the clustering regime of other cluster-like regions in the Galaxy. Conclusions. The typical masses and separations of the fragments as well as the relation between the density and number of fragments can be explained through a thermal Jeans process operating at high temperatures of 200-400 K, consistent with previous measurements of the temperature in the region, and produced by the nearby massive stars. Therefore, although W51 IRS2 seems to be undergoing a thermally inhibited fragmentation phase, this does not seem to prevent the formation of a protocluster associated with W51 North.

Abstract Copyright: © ESO 2021

Journal keyword(s): instrumentation: high angular resolution - methods: observational - stars: formation - stars: massive - radio continuum: ISM - ISM: individual objects: W51 North

VizieR on-line data: <Available at CDS (J/A+A/657/A30): table1.dat list.dat fits/*>

Status at CDS : Examining the need for a new acronym. // Tables of objects will be appraised for possible ingestion in SIMBAD.

Simbad objects: 16

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Number of rows : 16
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 4093 0
2 NAME OMC 1S PoC 05 35 14.5 -05 25 49           ~ 73 1
3 NAME Ori Trapezium OpC 05 35 16.5 -05 23 14           ~ 1568 1
4 Lupus 1 Cld 15 43 02.1 -34 09 06           ~ 263 0
5 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3446 1
6 NAME the Pipe Nebula DNe 17 30 -25.0           ~ 378 1
7 4C 09.57 BLL 17 51 32.81857326 +09 39 00.7284066   17.46 16.78 15.57   ~ 901 1
8 GB6 B1920+1524 Rad 19 22 34.69936025 +15 30 10.0326112           ~ 56 0
9 [KTH2018] W51 N4 smm 19 23 39.756 +14 31 05.37           ~ 4 0
10 OKYM W51 IRS 2 6 IR 19 23 39.816 +14 31 05.07           ~ 24 0
11 [WBN74] W 51 IRS 2 PCG 19 23 39.93 +14 31 09.4           ~ 277 0
12 NAME W 51 North Rad 19 23 40.0 +14 30 51           ~ 155 0
13 [KTH2018] W51 N2 smm 19 23 39.970 +14 31 05.70           ~ 4 0
14 [KTH2018] W51 N1 smm 19 23 40.047 +14 31 05.53           ~ 4 0
15 QSO B1921-293 BLL 19 24 51.05595254 -29 14 30.1210248   18.71 18.21 15.07   ~ 802 0
16 4C 06.69 QSO 21 48 05.45866779 +06 57 38.6041877   16.85 16.47 15.06   ~ 642 1

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2023.01.27-19:09:27

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