J/A+A/606/A8 Bubble HII region Sh2-39 (N5) (Duronea+, 2017)
Triggered massive star formation associated with the HII region bubble
Sh2-39 (N5).
Duronea N.U., Cappa C.E., Bronfman L., Borissova J., Gromadzki M., Kuhn M.A.
<Astron. Astrophys. 606, A8 (2017)>
=2017A&A...606A...8D 2017A&A...606A...8D (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Infrared sources ; Radio lines
Keywords: molecules: data - infrared: ISM - stars: formation - H II regions -
stars: massive
Abstract:
Aiming at studying the physical properties of Galactic IR bubbles and
to explore their impact in triggering massive star formation, we
perform a multiwavelength analysis of the bubble HII region Sh2-39
(N5) and its environs.
To analyze the molecular gas we use CO(3-2) and HCO+(4-3) line data
obtained with the on-the-fly technique from the ASTE telescope. To
study the distribution and physical characteristics of the dust, we
make use of archival data from ATLASGAL, Herschel, and MSX, while the
ionized gas was studied making use of an NVSS image. We use public
WISE, Spitzer, and MSX point source catalogs to search for infrared
candidate YSOs in the region. To investigate the stellar cluster
[BDS2003] 6 we use IR spectroscopic data obtained with the ARCoIRIS
spectrograph, mounted on Blanco 4-m Telescope at CTIO, and new
available IR Ks band observations from the VVVeXtended ESO Public
Survey (VVVX).
The new ASTE observations allowed the molecular gas component in the
velocity range from 30km/s to 46km/s, associated with Sh2-39, to be
studied in detail. The morphology of the molecular gas suggests that
the ionized gas is expanding against its parental cloud. We have
identified four molecular clumps, that were likely formed by the
expansion of the ionization front, and determined some of their
physical and dynamical properties. Clumps having HCO+ and 870um
counterparts show evidence of gravitational collapse. We identified
several candidate YSOs across the molecular component. Their spatial
distribution, as well as the fragmentation time derived for the
collected layers of the molecular gas, suggest that massive star
formation might have been triggered by the expansion of the nebula via
the collect and collapse mechanism. The spectroscopical distance
obtained for the stellar cluster [BDS2003] 6, placed over one of the
collapsing clumps in the border of the HII region, reveals that this
cluster is physically associated with the nebula and gives more
support to the triggered massive star formation scenario. A radio
continuum data analysis indicates that the nebula is older and expands
at lower velocity than typical IR Galactic bubbles.
Description:
The molecular observations were carried out in August 2015 with the
10m Atacama Submillimeter Telescope Experiment (ASTE). We used
DASH345, a two sideband single-polarization heterodyne receiver,
tunable in LO frequency range from 327GHz to 370GHz at observable
frequency range from 321GHz to 376GHz. The XF digital spectrometer was
set to a bandwidth and spectral resolution of 128MHz and 125KHz,
respectively. The spectral velocity resolution was 0.11km/s, the half
power beamwidth (HPBW) is ∼22", and the main beam efficiency (mb) is
0.65. Observations were made using the on-the-fly (OTF) mode with two
orthogonal scan directions along RA and Dec. (J2000) centered on RA,
Dec.(J2000)= (18:17:02.1, -18:40:19). We observed simultaneously the
lines CO(3-2) (345.796GHz) and HCO+(4-3) (356.734) in a region of
∼17'x17' (see Fig. 1). The spectra were reduced with NOSTAR2 using the
standard procedure.
The brightest star projected at the center of [BDS2003] 6
(2MASS J18165113-1841488) was observed on August 2016 with Astronomy
Research using the Cornell Infra Red Imaging Spectrograph (ARCoIRIS),
a cross-dispersed, single-object, longslit, infrared imaging
spectrograph,mounted on Blanco 4-m Telescope, CTIO. The spectra cover
a simultaneous wavelength range of 0.80 to 2.47um, at a spectral
resolution of about 3500 λ{δλ, encompassing the
entire zYJHK photometric range. The spectrum was taken with 480 sec
integration time, at 1.03 average airmass. The HD163336 telluric A0 V
standard is observed immediately after target. The basic steps of the
reduction procedure are described in Chene et al.
(2012A&A...545A..54C 2012A&A...545A..54C, Cat. J/A+A/545/A54, 2013A&A...549A..98C 2013A&A...549A..98C). We
used the corresponding pipeline.
Objects:
--------------------------------------------------------
RA (2000) DE Designation(s)
--------------------------------------------------------
18 16 59 -18 40.2 [CPA2006] N5 = [CPA2006] N5
18 16 51 -18 41.9 [BDS2003] 6 = [BDS2003] 6
18 16 51.13 -18 41 48.8 2MASS J18165113-1841488
--------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 98 2 List of datacubes centered on bubble HII region
Sh2-39 ([CPA2006] N5)
fits/* . 2 Individual datacubes
2m1816ma.dat 70 8447 2MASS J18165113-1841488 ARCoIRIS spectrum
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Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 31 I4 --- Nz Number of slices
33- 42 A10 "date" Obs.dat Observation date
44- 51 F8.1 m/s bVlsr Lower value of LSR velocity interval
53- 59 F7.1 m/s BVlsr Upper value of LSR velocity interval
61- 65 F5.1 m/s dVlsr LSR velocity resolution
67- 71 I5 Kibyte size Size of FITS file
73- 81 A9 --- FileName Name of FITS file, in subdirectory fits
83- 98 A16 --- Title Title of the FITS file
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Byte-by-byte Description of file (#): 2m1816ma.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
7- 16 F10.8 um lambda Wavelength
21- 34 E14.8 mW/m2 Flux ?=- Flux
40- 52 E13.8 mW/m2 e_Flux ?=- rms uncertainty on Flux
62- 70 F9.7 --- --- [0]
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Acknowledgements:
Nicolas Urbano Duronea, duronea(at)gmail.com
(End) Patricia Vannier [CDS] 19-Jun-2017