2015A&A...579A..51B


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.08CEST04:26:38

2015A&A...579A..51B - Astronomy and Astrophysics, volume 579A, 51-51 (2015/7-1)

Kinematic and thermal structure at the onset of high-mass star formation.

BIHR S., BEUTHER H., LINZ H., RAGAN S.E., HENNEMANN M., TACKENBERG J., SMITH R.J., KRAUSE O. and HENNING T.

Abstract (from CDS):

Even though high-mass stars are crucial for understanding a diversity of processes within our galaxy and beyond, their formation and initial conditions are still poorly constrained. We want to understand the kinematic and thermal properties of young massive gas clumps prior to and at the earliest evolutionary stages of high-mass star formation. Do we find signatures of gravitational collapse? Do we find temperature gradients in the vicinity or absence of infrared emission sources? Do we find coherent velocity structures toward the center of the dense and cold gas clumps? To determine kinematics and gas temperatures, we used ammonia, because it is known to be a good tracer and thermometer of dense gas. We observed the NH3 (1, 1) and (2, 2) lines within six very young high-mass star-forming regions comprised of infrared dark clouds (IRDCs), along with ISO-selected far-infrared emission sources (ISOSS) with the Karl G. Jansky Very Large Array (VLA) and the Effelsberg 100m Telescope. The molecular line data allows us to study velocity structures, linewidths, and gas temperatures at high spatial resolution of 3-5", corresponding to ∼0.05pc at a typical source distance of 2.5kpc. We find on average cold gas clumps with temperatures in the range between 10K and 30K. The observations do not reveal a clear correlation between infrared emission peaks and ammonia temperature peaks. Several infrared emission sources show ammonia temperature peaks up to 30K, whereas other infrared emission sources show no enhanced kinetic gas temperature in their surrounding. We report an upper limit for the linewidth of ∼1.3km/s, at the spectral resolution limit of our VLA observation. This indicates a relatively low level of turbulence on the scale of the observations. Velocity gradients are present in almost all regions with typical velocity differences of 1 to 2km/s and gradients of 5 to 10km/s/pc. These velocity gradients are smooth in most cases, but there is one exceptional source (ISOSS23053), for which we find several velocity components with a steep velocity gradient toward the clump centers that is larger than 30km/s/pc. This steep velocity gradient is consistent with recent models of cloud collapse. Furthermore, we report a spatial correlation of ammonia and cold dust, but we also find decreasing ammonia emission close to infrared emission sources.

Abstract Copyright:

Journal keyword(s): stars: formation - stars: massive - ISM: clouds - ISM: kinematics and dynamics - techniques: interferometric

VizieR on-line data: <Available at CDS (J/A+A/579/A51): list.dat fits/*>

Status at CDS:   Objects in title, abstract, text, figures, and all or part of small table(s) being processed in SIMBAD.

Simbad objects: 13

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Number of rows : 13

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3715 1
2 QSO B1730-130 QSO 17 33 02.70578476 -13 04 49.5481484   18 18.5 18.78 17.39 ~ 983 1
3 QSO B1741-038 QSO 17 43 58.85613396 -03 50 04.6166450     18.5 17.98   ~ 479 1
4 [RBP2006] G05.85-0.23 MoC 17 59 49.500 -24 00 50.25           ~ 8 0
5 NAME IRDC 18310-4 cor 18 33 39.42 -08 21 10.4           ~ 14 0
6 [RBP2006] G24.05-0.22 MoC 18 35 54.610 -07 59 48.07           ~ 8 0
7 NAME Dragon Nebula DNe 18 42 50.6 -04 03 30           ~ 112 0
8 [WZP2008] IRS 2 IR 18 42 51.92 -03 59 54.0           ~ 2 0
9 NVSS J185146+003532 Rad 18 51 46.72295 +00 35 32.3649           ~ 54 1
10 QSO B2023+336 BLL 20 25 10.84210 +33 43 00.2144       0   ~ 127 1
11 [MBS2007c] CygX-N44 Rad 20 39 01.01 +42 22 50.2           ~ 363 0
12 NGC 7027 PN 21 07 01.8 +42 14 10   9.1 10.9     ~ 2322 1
13 ICRF J232225.9+505751 QSO 23 22 25.98218320 +50 57 51.9636985       18.6   ~ 57 1

    Equat.    Gal    SGal    Ecl

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2020.07.08-04:26:38

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