J/A+A/542/A76 Herschel-HIFI water spectra of W43-MM1 (Herpin+, 2012)
The massive protostar W43-MM1 as seen by Herschel-HIFI water spectra:
high turbulence and accretion luminosity.
Herpin F., Chavarria L., van der Tak F., Wyrowski F., van Dishoeck E.F.,
Jacq T., Braine J., Baudry A., Bontemps S., Kristensen L.
<Astron. Astrophys. 542, A76 (2012)>
=2012A&A...542A..76H 2012A&A...542A..76H
ADC_Keywords: Stars, early-type ; Interstellar medium ; Spectroscopy
Keywords: ISM: molecules - ISM: abundances - stars: formation -
stars: protostars - stars: early-type - line: profiles
Abstract:
We present Herschel/HIFI observations of 14 water lines in W43-MM1, a
massive protostellar object in the luminous star-cluster-forming
region W43. We place our study in the more general context of
high-mass star formation. The dynamics of these regions may be
represented by either the monolithic collapse of a turbulent core, or
competitive accretion. Water turns out to be a particularly good
tracer of the structure and kinematics of the inner regions, allowing
an improved description of the physical structure of the massive
protostar W43-MM1 and an estimation of the amount of water around it.
We analyze the gas dynamics from the line profiles using Herschel-HIFI
observations acquired as part of the Water In Star-forming regions
with Herschel project of 14 far-IR water lines (H216O, H217O,
H218O), CS(11-10), and C18O(9-8) lines, using our modeling of
the continuum spectral energy distribution. The spectral modeling
tools allow us to estimate outflow, infall, and turbulent velocities
and molecular abundances. We compare our results to previous studies
of low-, intermediate-, and other high-mass objects.
As for lower-mass protostellar objects, the molecular line profiles
are a mix of emission and absorption, and can be decomposed into
'medium' (full width at half maximum FWHM~=5-10km/s), and 'broad'
velocity components (FWHM~=20-35km/s). The broad component is the
outflow associated with protostars of all masses. Our modeling shows
that the remainder of the water profiles can be well-fitted by an
infalling and passively heated envelope, with highly supersonic
turbulence varying from 2.2km/s in the inner region to 3.5km/s in the
outer envelope. In addition, W43-MM1 has a high accretion rate of
between 4.0x10-4 and 4.0x10-2M☉/yr, as derived from the fast
(0.4-2.9km/s) infall observed. We estimate a lower mass limit for
gaseous water of 0.11M☉ and total water luminosity of
1.5L☉ (in the 14 lines presented here). The central hot core is
detected with a water abundance of 1.4x10-4, while the water
abundance for the outer envelope is 8x10-8. The latter value is
higher than in other sources, and most likely related to the high
turbulence and the micro-shocks created by its dissipation.
Examining the water lines of various energies, we find that the
turbulent velocity increases with the distance from the center. While
not in clear disagreement with the competitive accretion scenario,
this behavior is predicted by the turbulent core model. Moreover, the
estimated accretion rate is high enough to overcome the expected
radiation pressure.
Description:
Data files (ASCII) of the HIFI-Herschel Space Observatory observations
of 14 water lines as well as the CS(11-10) and C18O(9-8) lines
toward W43-MM1. Continuum has been subtracted. Observations were
performed in March, April, and October 2010 (OD 293, 295, 310, 312,
333, 338, 339, and 531). The position observed is RA=18:47:47.0,
DEC=-01:54:28 J2000. The observations are part of WISH GT-KP.
Data were taken simultaneously in H and V polarizations using both the
acousto-optical Wide-Band Spectrometer (WBS) with a 1.1MHz resolution
and the digital auto-correlator or High-Resolution Spectrometer (HRS)
providing higher spectral resolution. We used the double beam switch
observing mode with a throw of 3'. The HIFI receivers are double
sideband with a sideband ratio close to unity. The frequencies, energy
of the upper levels, system temperatures, integration times, and
rms noise level at a given spectral resolution for each of the lines
are provided in Table 1 of the paper. The calibration of the raw data
onto the TA scale was performed by the in-orbit system (see
Roelfsema et al., 2012A&A...537A..17R 2012A&A...537A..17R); and the conversion to Tmb
was done using a beam efficiency given in Table 1 and a forward
efficiency of 0.96. The flux scale accuracy was estimated to be 10%
for bands 1 and 2, 15% for bands 3 and 4, and 20% in bands 6 and 7.
Data calibration was performed in the Herschel Interactive Processing
Environment version 6.0. Further analysis was done within the CLASS
package. After inspection, data from the two polarizations were
averaged together. Since HIFI operates in double-sideband, the
measured continuum level was divided by a factor of two.
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------
18 47 47.0 -01 54 28 W43-MM1 = [MSM95] G30.79 FIR 10
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 123 16 Herschel/HIFI observed line transitions in W43-MM1
sp/* . 16 Individual spectra
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See also:
J/A+A/538/A11 : 70um-1.2mm and N2H+ maps of IRDC18454 (W43) (Beuther+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Species Water species
25 A1 --- n_Species [a] a: this line was mapped in OTF mode
27- 35 F9.4 GHz Freq Frequency (1)
37- 41 F5.1 um lambda Wavelength
43- 47 F5.1 K Eu Energy of upper level (2)
49- 50 A2 --- HIFI HIFI band
52- 55 F4.1 arcsec Beam Beam size (3)
57- 61 F5.3 --- etamb Main beam efficiency, ηmb (3)
63- 66 I4 K Tsys System temperature
68- 71 F4.2 MHz dnu Spectral resolution δν
73- 76 I4 s Tint Integration time
78- 80 I3 mK rms rms noise level at the given spectral
resolution dnu
82- 92 A11 --- FileName Name of the file with spectrum
94-101 A8 --- Inst Instrument (HRS-HIFI or WBS-HIFI)
103-123 A21 --- ObsId Observation Id(s)
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Note (1): Frequencies are from Pearson et al. (1991ApJ...379L..41P 1991ApJ...379L..41P).
Note (2): The energy of the upper level, Eu, is considered to be the same
for H217O and H218O.
Note (3): Beam and etamb are from Roelfsema et al. (2012A&A...537A..17R 2012A&A...537A..17R).
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Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.10 km/s RVlsr LSR radial velocity
20- 30 E11.5 K T Main beam temperature
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Acknowledgements:
Fabrice Herpin, herpin(at)obs.u-bordeaux1.fr
(End) Patricia Vannier [CDS] 24-Apr-2012