J/A+A/647/A78 NGC6334 850um I, Q, U Stokes parameter maps (Arzoumanian+, 2021)
Dust polarized emission observations of NGC 6334.
BISTRO reveals the details of the complex but organized magnetic field structure
of the high-mass star-forming hub-filament network.
Arzoumanian D., Furuya R., Hasegawa T., Tahani M., Sadavoy S., Hull C.L.H.,
Johnstone D., Koch P.M., Inutsuka S., Doi Y., Hoang T., Onaka T.,
Iwasaki K., Shimajiri Y., Inoue T., Peretto N., Andre P., Bastien P.,
Berry D., Chen H.-R.V., Di Francesco J., Eswaraiah C., Fanciullo L.,
Fissel L.M., Hwang J., Kang J.-h., Kim G., Kim K.-T., Kirchschlager F.,
Kwon W., Lee C.W., Liu H.-L., Lyo A.-R., Pattle K., Soam A., Tang X.,
Whitworth A., Ching T.-C., Coude S., Wang J.-W., Ward-Thompson D.,
Lai S.-P., Qiu K., Bourke T.L., Byun D.-Y., Chen M., Chen Z., Chen W.P.,
Cho J., Choi Y., Choi M., Chrysostomou A., Chung E.J., Dai S., Diep P.N.,
Duan H.-Y., Duan Y., Eden D., Fiege J., Franzmann E., Friberg P.,
Fuller G., Gledhill T., Graves S., Greaves J., Griffin M., Gu Q., Han I.,
Hatchell J., Hayashi S., Houde M., Jeong I.-G., Kang M., Kang S.-J.,
Kataoka A., Kawabata K., Kemper F., Kim M.-R., Kim K.H., Kim J., Kim S.,
Kirk J., Kobayashi M.I.N., Konyves V., Kusune T., Kwon J., Lacaille K.,
Law C.-Y., Lee C.-F., Lee Y.-H., Lee S.-S., Lee H., Lee J.-E., Li H.-b.,
Li D., Liu J., Liu T., Liu S.-Y., Lu X., Mairs S., Matsumura M.,
Matthews B., Moriarty-Schieven G., Nagata T., Nakamura F., Nakanishi H.,
Ngoc N.B., Ohashi N., Park G., Parsons H., Pyo T.-S., Qian L., Rao R.,
Rawlings J., Rawlings M., Retter B., Richer J., Rigby A., Saito H.,
Savini G., Scaife A., Seta M., Shinnaga H., Tamura M., Tang Y.-W.,
Tomisaka K., Tram L.N., Tsukamoto Y., Viti S., Wang H., Xie J., Yen H.-W.,
Yoo H., Yuan J., Yun H.-S., Zenko T., Zhang G., Zhang C.-P., Zhang Y.,
Zhou J., Zhu L., de Looze I., Dowell C.D., Eyres S., Falle S., Friesen R.,
Robitaille J.-F., van Loo S.
<Astron. Astrophys. 647, A78 (2021)>
=2021A&A...647A..78A 2021A&A...647A..78A (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Polarization
Keywords: stars: formation - submillimeter: ISM - ISM: magnetic fields -
ISM: structure - plarization - ISM: clouds
Abstract:
Molecular filaments and hubs have received special attention recently
thanks to new studies showing their key role in star formation. While
the (column) density and velocity structures of both filaments and
hubs have been carefully studied, their magnetic field (B-field)
properties have yet to be characterized. Consequently, the role of
B-fields in the formation and evolution of hub-filament systems is not
well constrained.
We aim to understand the role of the B-field and its interplay with
turbulence and gravity in the dynamical evolution of the NGC 6334
filament network that harbours cluster-forming hubs and high-mass star
formation.
We present new observations of the dust polarized emission at 850mum
toward the 2pcx10pc map of NGC 6334 at a spatial resolution of 0.09pc
obtained with the James Clerk Maxwell Telescope (JCMT) as part of the
B-field In STar-forming Region Observations (BISTRO) survey. We study
the distribution and dispersion of the polarized intensity (PI), the
polarization fraction (PF), and the plane-of-the-sky (POS) B-field
angle (χBPOS) toward the whole region, along the 10pc-long ridge
and along the sub-filaments connected to the ridge and the hubs. We
derived the power spectra of the intensity and χBPOS along the
ridge crest and compared them with the results obtained from simulated
filaments.
The observations span ∼3 orders of magnitude in I and PI and ∼2 orders
of magnitude in PF (from ∼0.2% to ∼20%). A large scatter in PI and PF
is observed for a given value of I. Our analyzes show a complex
B-field structure when observed over the whole region (∼10pc);
however, at smaller scales (∼1pc), χBPOS varies coherently along
the crests of the filament network.
The observed power spectrum of χBPOS can be well
represented with a power law function with a slope of -1.33±0.23,
which is ∼20% shallower than that of I. We find that this
result is compatible with the properties of simulated filaments and
may indicate the physical processes at play in the formation and
evolution of star-forming filaments. Along the sub-filaments,
χBPOS rotates from being mostly perpendicular or
randomly oriented with respect to the crests to mostly parallel as the
sub-filaments merge with the ridge and hubs. This variation of the
B-field structure along the sub-filaments may be tracing local
velocity flows of infalling matter in the ridge and hubs. Our analysis
also suggests a variation in the energy balance along the crests of
these sub-filaments, from magnetically critical or supercritical at
their far ends to magnetically subcritical near the ridge and hubs. We
also detect an increase in PF toward the high-column density
(NH2≳1023cm-2) star cluster-forming hubs. These latter
large PF values may be explained by the increase in grain alignment
efficiency due to stellar radiation from the newborn stars, combined
with an ordered B-field structure.
These observational results reveal for the first time the
characteristics of the small-scale (down to ∼0.1pc) B-field structure
of a 10pc-long hub-filament system. Our analyzes show variations in
the polarization properties along the sub-filaments that may be
tracing the evolution of their physical properties during their
interaction with the ridge and hubs. We also detect an impact of
feedback from young high-mass stars on the local B-field structure and
the polarization properties, which could put constraints on possible
models for dust grain alignment and provide important hints as to the
interplay between the star formation activity and interstellar
B-fields.
Description:
Stokes parameter maps (I, Q, and U) observed with the JCMT/POL-2
camera at 850 microns toward the NGC 6334 high-mass star-forming
hub-filament system. The maps are at the angular resolution of 14.1".
The variance maps of the signal are also given as second layers of the
fits files.
Objects:
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RA (2000) DE Designation(s)
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17 20 50.9 -36 06 54 NGC 6334 = NAME Cat's Paw Nebula
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 134 3 List of fits files
fits/* . 3 Individual fits files
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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 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 50 A23 "datime" Obs.date Observation date
52- 54 I3 um lambda Wavelength
56- 59 I4 Kibyte size Size of FITS file
61- 80 A20 --- FileName Name of FITS file, in subdirectory fits
82-134 A53 --- Title Title of the FITS file
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Acknowledgements:
Doris Arzoumanian, doris.arzou[at]gmail.com
(End) Patricia Vannier [CDS] 13-Jan-2021