J/A+A/567/A116 Maps and datacubes of NGC 7538 IRS 1 (Frau+, 2014)
Shaping a high-mass star-forming cluster through stellar feedback.
The case of the NGC 7538 IRS 1-3 complex.
Frau P., Girart J.M., Zhang Q., Rao R.
<Astron. Astrophys. 567, A116 (2014)>
=2014A&A...567A.116F 2014A&A...567A.116F
ADC_Keywords: Protostars ; Magnetic fields ; Interferometry ;
Interstellar medium
Keywords: ISM: individual objects: NGC 7538 IRS 1 - ISM: magnetic fields -
stars: formation - polarization - submillimeter: ISM -
techniques: interferometric
Abstract:
NGC 7538 IRS 1-3 is a high-mass star-forming cluster with several
detected dust cores, infrared sources, (ultra)compact HII regions,
molecular outflows, and masers. In such a complex environment,
interactions and feedback among the embedded objects are expected to
play a major role in the evolution of the region.
We study the dust, kinematic, and polarimetric properties of the
NGC 7538 IRS 1-3 region to investigate the role of the different
forces in the formation and evolution of high-mass star-forming
clusters. Methods: We performed SMA high angular resolution
observations at 880um with the compact configuration. We developed
the RATPACKS code to generate synthetic velocity cubes from models of
choice to be compared to the observational data. To quantify the
stability against gravitational collapse we developed the "mass
balance" analysis that accounts for all the energetics on core
scales.
We detect 14 dust cores from 3.5M☉ to 37M☉ arranged in two
larger scale structures: a central bar and a filamentary spiral arm.
The spiral arm presents large-scale velocity gradients in
H13CO+ 4-3 and C17O 3-2, and magnetic field segments aligned
well to the dust main axis. The velocity gradient is reproduced well
by a spiral arm expanding at 9km/s with respect to the central core
MM1, which is known to power a large precessing outflow. The energy of
the outflow is comparable to the spiral-arm kinetic energy, which
dominates gravitational and magnetic energies. In addition, the
dynamical ages of the outflow and spiral arm are comparable. On core
scales, those embedded in the central bar seem to be unstable against
gravitational collapse and prone to forming high-mass stars, while
those in the spiral arm have lower masses that seem to be supported by
non-thermal motions and magnetic fields.
The NGC 7538 IRS 1-3 cluster seems to be dominated by protostellar
feedback. The dusty spiral arm appears to be formed in a snowplow
fashion owing to the outflow from the MM1 core. We speculate that the
external pressure from the redshifted lobe of the outflow could
trigger star formation in the spiral arm cores. This scenario would
form a small cluster with a few central high-mass stars, surrounded by
a number of low-mass stars formed through protostellar feedback.
Description:
Single field, spectro-polarimetric observations at 345GHz with the SMA
interferometer (Submillimeter Array located in Hawaii) toward the
high-mass star forming cluster NGC 7538 IRS 1. The antenna's primary
beam is 32.4arcsec (FWHM), and the spectral resolution is 0.7km/s.
Objects:
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RA (2000) DE Designation(s)
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23 13 45.4 +61 28 12 NGC 7538 IRS 1 = [WBN74] NGC 7538 IRS 1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 71 14 Parameters of the 878µm continuum sources
list.dat 115 7 List of FITS files
fits/* . 7 Individual FITS files
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See also:
J/ApJ/696/471 : MIR spectroscopy of NGC 7538 IRS 1 (Knez+, 2009)
J/A+A/543/A88 : NGC 7538 IRS 1 and NGC 7538 S 1.36mm maps (Beuther+, 2012)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [MM]
3- 4 A2 --- Src Source designation (1 to 13)
6- 7 I2 h RAh Right Ascension J2000 (hours)
8 A1 --- --- [:]
9- 10 I2 min RAm Right Ascension J2000 (minutes)
11 A1 --- --- [:]
12- 17 F6.3 s RAs Right Ascension J2000 (seconds)
18 A1 --- --- [:]
19 A1 --- DE- Declination J2000 (sign)
20- 21 I2 deg DEd Declination J2000 (degrees)
22 A1 --- --- [:]
23- 24 I2 arcmin DEm Declination J2000 (minutes)
25 A1 --- --- [:]
26- 30 F5.2 arcsec DEs Declination J2000 (seconds)
32- 36 F5.3 Jy Ipk Peak intensity Ipeak at 341.4GHz (in Jy/beam)
38- 41 F4.2 Jy S Flux at 341.4GHz
43- 46 F4.2 Jy e_S Mean error on 341.4GHz flux
48- 51 F4.2 kAU Diam Source diameter in 103AU (1)
53- 55 I3 K Td Dust temperature (2)
57- 61 F5.2 10+23cm-2 NH2 H2 column density
62- 66 F5.2 10+6cm-3 nH2 H2 density
68- 71 D4.1 Msun Mass Mass of source (3)
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Note (1): diameter of the circle with area equal to the source area
satisfying I>Ipeak/2
Note (2): temperature from Qiu et al. (2011ApJ...728....6Q 2011ApJ...728....6Q),
or set to 40K if source not therein.
Note (3): mass computed, assuming opacity κ341.4GHz=0.0015cm2/g
(Ossenkopf & Henning 1994 (J/A+A/291/943)
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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- 22 F3.1 arcsec/pix Scale Scale of the image
24- 26 I3 --- Nx [128] Number of pixels along X-axis
27 A1 --- --- [x]
28- 30 I3 --- Ny [128] Number of pixels along Y-axis
31 A1 --- --- [x]
32- 33 I2 --- Nz [6/12]? Number of slices for datacubes
35- 40 F6.2 km/s bVel [-68.0/-66.7]? Lower value of LSR velocity
interval for data cubes (VELO-LSR)
42- 47 F6.2 km/s BVel [-60.8/-59.2]? Upper value of LSR velocity
interval for data cubes (VELO-LSR)
49- 52 I4 m/s dVel [705/1400]? Velocity resolution
53- 58 F6.2 GHz Freq [341.47]? LSR frequency, for maps (FREQ-LSR)
64- 66 I3 Kibyte size [96/799] Size of FITS file
68- 79 A12 --- FileName Name of FITS file in subdirectory fits
82-115 A34 --- Title Title of the file
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Acknowledgements:
Pau Frau, p.frau(at)oan.es
(End) Pau Frau [CSIC-ICMM, Spain], Patricia Vannier [CDS] 10-Jul-2014