2016A&A...589A..44G


C.D.S. - SIMBAD4 rel 1.7 - 2021.04.19CEST07:46:50

2016A&A...589A..44G - Astronomy and Astrophysics, volume 589A, 44-44 (2016/5-1)

Hot ammonia around young O-type stars. III. High-mass star formation and hot core activity in W51 Main.

GODDI C., GINSBURG A. and ZHANG Q.

Abstract (from CDS):

Context. This paper is the third in a series of NH3 multilevel imaging studies in well-known, high-mass star-forming regions. The main goal is to characterize kinematics and physical conditions of (hot and dense) circumstellar molecular gas around O-type young stars.
Aims. We want to map at subarcsecond resolution highly excited inversion lines of NH3 in the high-mass star-forming region W51 Main (distance=5.4kpc), which is an ideal target to constrain theoretical models of high-mass star formation.
Methods. Using the Karl Jansky Very Large Array (JVLA), we mapped the hot and dense molecular gas in W51 Main with ∼0.2"-0.3" angular resolution in five metastable (J=K) inversion transitions of ammonia (NH3): (J,K)=(6, 6), (7, 7), (9, 9), (10, 10), and (13, 13). These lines arise from energy levels between ∼400K and ∼1700K above the ground state. We also made maps of the (free-free) continuum emission at frequencies between 25 and 36GHz.
Results. We have identified and characterized two main centers of high-mass star formation in W51 Main, which excite hot cores and host one or multiple high-mass young stellar objects (YSOs) at their centers: the W51e2 complex and the W51e8 core (∼6" southward of W51e2). The former breaks down into three further subcores: W51e2-W, which surrounds the well-known hypercompact (HC) HII region, where hot NH3 is observed in absorption, and two additional dusty cores, W51e2-E (∼0.8" to the East) and W51e2-NW (∼1" to the North), where hot NH3 is observed in emission. The velocity maps toward the HC HII region show a clear velocity gradient along the east-west in all lines. The gradient may indicate rotation, although any Keplerian motion must be on smaller scales (<1000AU) as we do not directly observe a Keplerian velocity profile. The absence of outflow and/or maser activity and the low amount of molecular gas available for accretion (∼5M, assuming [NH3]/[H2]=10–7) with respect to the mass of the central YSO estimated from radio luminosity (>20M), both indicate that the central YSO has already accreted most of its final mass. On the other hand, the nearby W51e2-E, while not showing evidence of rotation, shows signatures of infall in a hot dense core (T∼170K, nH2∼5x107cm–3), based on asymmetric spectral profiles (skewed toward the blueshifted component) in optically thick emission lines of NH3. The relatively large amount of hot molecular gas available for accretion (∼20M within about half an arcsecond or 2500AU), along with strong outflow and maser activity, indicates that the main accretion center in the W51e2 complex is W51e2-E rather than W51e2-W. Finally, W51e2-NW and W51e8, although less dense (nH2∼2x107cm–3 and ∼3x106cm–3), are also hot cores (Tgas∼140 and 200K) and contain a significant amount of molecular gas (Mgas∼30M and ∼70M, respectively). We speculate that they may host high-mass YSOs either at a previous evolutionary stage or with a mass that is lower than W51e2-E and W51e2-W.
Conclusions. Using high-angular resolution multilevel imaging of highly excited NH3 metastable lines, we characterized the physical and dynamical properties of four individual high-mass young stars forming in the W51 Main clump.

Abstract Copyright: © ESO, 2016

Journal keyword(s): accretion, accretion disks - line: profiles - ISM: kinematics and dynamics - ISM: molecules - stars: protostars - HII regions

VizieR on-line data: <Available at CDS (J/A+A/589/A44): list.dat fits/*>

Simbad objects: 17

goto Full paper

goto View the reference in ADS

Number of rows : 17

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 3C 48 QSO 01 37 41.2995845985 +33 09 35.079126038   16.62 16.20     ~ 2577 2
2 3C 84 Sy2 03 19 48.1597607660 +41 30 42.114155434   13.10 12.48 11.09   ~ 3632 3
3 W 31c HII 18 10 29.1 -19 56 05           ~ 308 0
4 IRAS 18449-0115 cor 18 47 34.4947 -01 12 40.269           ~ 323 0
5 NAME W 51 North Rad 19 23 40.0 +14 30 51           ~ 145 0
6 [WBN74] W 51 IRS 2 SFR 19 23 40.05 +14 31 07.1           ~ 256 0
7 NAME W 51 IRS 1 PoC 19 23 41.9 +14 30 36           ~ 100 0
8 W 51e1 Rad 19 23 43.77 +14 30 25.9           ~ 117 0
9 NAME W 51 Main reg 19 23 43.8 +14 30 37           ~ 132 0
10 [SZH2010] W51e2-NW Rad 19 23 43.870 +14 30 35.97           ~ 8 0
11 [SZH2010] W51e2-W Rad 19 23 43.900 +14 30 34.62           ~ 8 0
12 W 51e2 Rad 19 23 43.90 +14 30 34.8           ~ 187 0
13 [SZH2010] W51e2-E Rad 19 23 43.960 +14 30 34.56           ~ 13 0
14 W 51e8 HII 19 23 44.2 +14 30 28           ~ 34 0
15 W 51 SNR 19 23 50 +14 06.0           ~ 1176 1
16 ICRF J192439.4+154043 Bz? 19 24 39.45588 +15 40 43.9420           ~ 32 1
17 [WBN74] NGC 7538 IRS 1 Y*O 23 13 45.318 +61 28 11.69           ~ 375 3

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2016A&A...589A..44G and select 'bookmark this link' or equivalent in the popup menu


2021.04.19-07:46:50

© Université de Strasbourg/CNRS

    • Contact