J/A+A/635/A2 NGC6334 ALMA 87.6GHz continuum emission map (Sadaghiani+, 2020)
Physical properties of the star-forming clusters in NGC 6334.
A study of the continuum dust emission with ALMA.
Sadaghiani M., Sanchez-Monge A., Schilke P., Liu H.B., Clarke S.D.,
Zhang Q., Girart J.M., Seifried D., Aghababaei A., Li H., Juarez C.,
Tang K.S.
<Astron. Astrophys. 635, A2 (2020)>
=2020A&A...635A...2S 2020A&A...635A...2S (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Radio lines
Keywords: ISM: clouds - submillimetre: ISM - star formation - stars: massive -
ISM: individual objects: NGC6334-I -
ISM: individual objects: NGC6334-I(N)
Abstract:
We aim to characterise certain physical properties of high-mass
star-forming sites in the NGC6334 molecular cloud, such as
the core mass function (CMF), spatial distribution of cores, and mass
segregation.
We used the Atacama Large Millimetre/sub-millimetre Array (ALMA) to
image the embedded clusters NGC6334-I and NGC6334-I(N) in the
continuum emission at 87.6GHz. We achieved a spatial resolution of
1300au, enough to resolve different compact cores and fragments, and to
study the properties of the clusters.
We detected 142 compact sources distributed over the whole surveyed
area. The ALMA compact sources are clustered in different regions. We
used different machine-learning algorithms to identify four main
clusters: NGC6334-I, NGC6334-I(N), NGC6334-I(NW), and NGC6334-E. The
typical separations between cluster members range from 4000au to
12000au. These separations, together with the core masses
(0.1-100M☉), are in agreement with the fragmentation being
controlled by turbulence at scales of 0.1pc. We find that the CMFs
show an apparent excess of high-mass cores compared to the stellar
Initial Mass Function. We evaluated the effects of temperature and
unresolved multiplicity on the derived slope of the CMF. Based on
this, we conclude that the excess of high-mass cores might be spurious
and due to inaccurate temperature determinations and/or resolution
limitations. We searched for evidence of mass segregation in the
clusters and we find that clusters NGC6334-I and NGC6334-I(N) show
hints of segregation with the most massive cores located in the centre
of the clusters.
We searched for correlations between the physical properties of the
four embedded clusters and their evolutionary stage (based on the
presence of Hii regions and infrared sources). NGC6334-E appears as
the most evolved cluster, already harboring a well-developed Hii
region. NGC6334-I is the second-most evolved cluster with an
ultra-compact Hii region. NGC6334-I(N) contains the largest population
of dust cores distributed in two filamentary structures and no
dominant Hii region. Finally, NGC6334-I(NW) is a cluster of mainly
low-mass dust cores with no clear signs of massive cores or Hii
regions.We find a larger separation between cluster members in the
more evolved clusters favoring the role of gas expulsion and stellar
ejection with evolution. The mass segregation, seen in the NGC6334-I
and NGC6334-I(N) clusters, suggests a primordial origin for
NGC6334-I(N). In contrast, the segregation in NGC6334-I might be due
to dynamical effects. Finally, the lack of massive cores in the most
evolved cluster suggests that the gas reservoir is already exhausted,
while the less evolved clusters still have a large gas reservoir along
with the presence of massive cores. In general, the fragmentation
process of NGC6334 at large scales (from filament to clump, i.e. at
about 1pc) is likely governed by turbulent pressure, while at smaller
scales (scale of cores and sub-fragments, i.e. a few hundred au)
thermal pressure starts to be more significant.
Description:
The high-mass star-forming clusters in NGC 6334 are observed with ALMA
with a resolution of 1 arcsec (corresponding to 1300au) at 88GHZ.
Objects:
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RA (2000) DE Designation(s)
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17 20 53.0 -35 46 59.0 NGC 6449-I = NGC 6334I
17 20 54.0 -35 45 06.0 NGC 6449-I(N) = NAME NGC 6334 I(N)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 121 142 Properties of the ALMA continuum sources
in NGC 6334
list.dat 185 1 Information on fits images
fits/* . 1 Individual fits image
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See also:
J/A+A/587/A135 : Halpha images of NGC 6334 and NGC 6357 (Russeil+, 2016)
J/A+A/592/A54 : Combined ArTeMiS+SPIRE 350um image of NGC6334 (Andre+, 2016)
J/A+A/593/A37 : Spectral cube toward NGC 6334 I and I(N) (van der Wiel+, 2016)
J/A+A/632/A83 : NGC 6334 filament with ALMA (Shimajiri+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq ALMA 87.6GHz compact source sequential number
5- 6 I2 h RAh ALMA 87.6GHz Right ascension (J2000)
8- 9 I2 min RAm ALMA 87.6GHz Right ascension (J2000)
11- 16 F6.3 s RAs ALMA 87.6GHz Right ascension (J2000)
18 A1 --- DE- ALMA 87.6GHz Declination sign (J2000)
19- 20 I2 deg DEd ALMA 87.6GHz Declination (J2000)
22- 23 I2 arcmin DEm ALMA 87.6GHz Declination (J2000)
25- 29 F5.2 arcsec DEs ALMA 87.6GHz Declination (J2000)
31- 36 F6.2 mJy/beam I ALMA 87.6GHz peak intensity
38- 44 F7.2 mJy S ALMA 87.6GHz flux density
46- 51 F6.2 mJy e_S rms uncertainty on ALMA 87.6GHz flux density
53- 57 F5.2 arcsec amaj ALMA 87.6GHz major axis
58 A1 --- --- [x]
59- 62 F4.2 arcsec bmin ALMA 87.6GHz minor axis
63 A1 --- --- [,]
64- 66 I3 deg PA ? ALMA 87.6GHz position angle
68- 72 A5 --- Free-Free Radio continuum contribution to the
ALMA 87.6 GHz continuum flux (1)
74- 79 A6 --- IR Association with infrared source (2)
80- 82 I3 K T ? Assumed temperature
84- 89 F6.2 Msun Mg+d ? Dust and gas mass
91- 95 F5.2 10+8cm-3 nH2 ? Volume density
97-101 F5.2 10+24cm-2 NH2 ? Column density
103-109 A7 --- Cluster Cluster to which the source is associated
111-113 I3 % Pmemb ? Confidence level of membership in
percentage
115-121 A7 --- ONames Other names for each source (3)
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Note (1): Radio continuum contribution to the ALMA 87.6GHz continuum flux,
determined from observations published in Hunter et al. (2014ApJ...788..187H 2014ApJ...788..187H),
Brogan et al. (2016, Cat. J/ApJ/832/187), and
Medina et al. (2018, Cat. J/A+A/610/A27).
Note (2): Association with infrared source from Willis et al. (2013,
Cat. J/ApJ/778/96). f* denotes field stars.
Note (3): Other names for each source, from Brogan et al. (2016,
Cat. J/ApJ/832/187, [BHC2016] MMNN in Simbad) and
Hunter et al. (2014ApJ...788..187H 2014ApJ...788..187H, [HBM2006b] I(N)-SMANN in Simbad).
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 51 A22 "datime" Obs.date Observation date
53- 59 F7.4 GHz Freq Observed frequency
61- 65 I5 Kibyte size Size of FITS file
67-138 A72 --- FileName Name of FITS file, in subdirectory fits
140-185 A46 --- Title Title of the FITS file
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Acknowledgements:
Mahya Sadaghiani, sadaghiani(at)ph1.uni-koeln.de
(End) Patricia Vannier [CDS] 06-Feb-2020