SMA Observations of the Hot Molecular Core IRAS 18566+0408
Andrea Silva Qizhou Zhang Patricio Sanhueza Xing Lu Maria T. Beltran Cassandra Fallscheer Henrik Beuther T. K. Sridharan Riccardo Cesaroni




Andrea Silva
andrea.silva@tufts.edu


Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Department of Physics and Astronomy, Tufts University, Medford, MA 02155, USA
National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan



Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA


National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan


National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan


INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125, Italy


Central Washington University, 400 E University Way, Ellensburg, WA 98926, USA


Max-Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany


Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA


INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125, Italy





We present Sub­mi­lli­me­ter Array (SMA) observations toward the high-mass star-forming region . Observations at 1.3 mm continuum and in several molecular line transitions were performed  in the com­pact (24 angular resolution) and very-extended (∼04 angular resolution) configurations. 
The continuum emission from the compact configuration shows a dust core
 of 150  , while the very-extended configuration reveals a dense (2.6 × 10^7 cm^-3) and compact 
 (∼4,000 AU) condensation of 8 . 
We detect 31 molecular transitions from 14 species including CO isotopologues, SO, CH_3OH, OCS, and CH_3CN. Using the different k-ladders of the CH_3CN line, we derive a rotational temperature at the location of the continuum peak of 240 K. 
The , , and  lines reveal a molecular outflow at PA∼135 centered at the continuum peak. 
The extended  emission has been recovered with the IRAM 30 m telescope observations. 
Using the combined data set, we derive an  outflow mass of 16.8 . 
The chemically rich spectrum and the high rotational temperature confirm  that  is harboring a hot molecular core.  We find no clear velocity gradient that could suggest the presence of a rotational disk-like structure, even at the high resolution observations obtained with the very-extended configuration. 










§ INTRODUCTION


The study of the formation of high-mass stars, especially in the early evolutionary phases, has been observationally challenging due to the large distances involved (d≥1 kpc), complex cluster environments (n_⋆≳100 pc^-3 ), and short evolutionary timescales (t_≤10^4 yr for a O-type star) in comparison with the study of low-mass stars.  Early stages  of massive star formation have numerous observational signatures, including molecular masers <cit.>, outflows <cit.>, chemically evolved regions <cit.>, hot molecular cores <cit.>, hyper/ultracompact H II regions <cit.>, and ionized winds and jets <cit.>

Hot molecular cores (HMCs) contain gas and dust near or around sites of recent star formation <cit.>.
 They are characterized by small sizes (≤0.1 pc), high gas densities (n_≥10^7 cm^-3), and high-temperatures (T_k≥100 K) <cit.>. Unlike H II regions, these objects present weak or undetectable free-free emission. The lack of free-free emission has been interpreted as due to an intense mass accretion phase that quenches the development of an H II region <cit.>. Therefore, HMCs are likely the precursors of H II regions.
The hot core phase is thought to last about 10^5 yr <cit.> to 10^6 yr <cit.> and represents the most chemically-rich phase of the interestellar medium, characterized by the presence of complex organic molecules such as CH_3OH, CH_3CN, HCOOCH_3, CH_3OCH_3, and CH_3CH_2CN <cit.>.
The observation of HMCs is important for understanding the evolutionary sequence and physical conditions of massive star formation. Due to the compact and dense nature of HMCs, high angular resolution observations using molecular lines with high critical densities and excitation temperatures are crucial to uncover their physical conditions and to search for accretion disks. In recent years, the search for accretion disks in HMCs has been very fruitful, as summarized in the review by 
<cit.>, and Keplerian disk candidates have been found <cit.>


 is a high-mass star-forming region located at a kinematic distance of 6.7 kpc <cit.> with a total far-infrared luminosity of ∼8×10^4  <cit.>  that comes from a single compact (<5) dust continuum source, indicating the presence of an embedded O8 ZAMS high-mass star <cit.>.
Weak radio continuum emission was detected at 3.6 cm <cit.> and at 2 cm
 <cit.>, suggesting that this source is  in a phase prior to the development of a bright ultracompact H II region. Very recent observations with the VLA in the 6 and 1.3 cm wavelength bands resolve the radio continuum source in four components consistent with an ionized jet <cit.>.  
Dense gas traced by CS and CH_3CN, as well as (sub)mm continuum emission, has been observed <cit.>. NH_3(1,1) and (2,2) emission were detected first using single-dish telescopes by <cit.>, <cit.>, and  <cit.>, and later imaged using the VLA <cit.>.


Current star formation in the region is also evident from the presence of 22 GHz H_2O, 6.7 GHz CH_3OH, 8 GHz H_2CO, and 6.03 GHz OH  maser emission <cit.>, as well as the presence of molecular outflows detected in SiO and  NH_3 <cit.> at PA=135.  <cit.> suggest the presence of an ionized jet, inferred by emission at 4.5 μm 
from Spitzer and 3.6 cm continuum from VLA, roughly in the direction of the molecular outflow. This jet has been 
recently confirmed by <cit.> at ∼03 angular resolution. 
 Compact and narrow  NH_3(3,3) line emission features are found associated with the outflow <cit.>, likely arising from weak population inversion similar to maser emission <cit.>. 
<cit.> detected emission at 7 mm of a torus-like structure (PA=44^o) almost perpendicular to the observed ionized jet (PA∼ 100^o). 

In order to study the physical and kinematical properties of the high-mass star-forming region IRAS 18566+0408, we carried out sub-arcsecond angular resolution observations with the Submillimeter Array in both
 continuum and molecular line emission.  has a bipolar molecular outflow, which is expected to be associated to 
 a disk. Our main goal is to search for the presence or absence of disk-like structure(s) around the 
 high-mass star(s) driving the molecular outflow. This paper is organized as follow: in <ref> we summarize the observations, in <ref> we present the results,  and in <ref> we discuss and conclude the main findings of the investigation.










§ OBSERVATIONS


Observations of  were carried out with the Sub-millimeter Array[The Submillimeter Array is a joint project between the Smithsonian
Astrophysical Observatory and the Academia Sinica Institute of Astronomy and
Astrophysics, and is funded by the Smithsonian Institution and the Academia
Sinica.]  (SMA) <cit.> using two different  configurations. Compact-array observations were taken on July 9, 2007 at 24 angular resolution. Very-extended configuration data were obtained on August 3, 2008 at 04 angular resolution.
Two spectral sidebands, of 2 GHz wide and separated by 10 GHz, covered the frequency ranges of 219.4–221.3 GHz and 229.3–231.2 GHz.  The receivers were tuned to 230.538 GHz in the upper sideband with a channel spacing of 0.53 .
The primary beam of the SMA at 225 GHz is 56.
The phase reference center of the observation was set to the position α(J2000)=18^59^09^.99 and
δ(J2000)= 0412157.
Quasars J1751+096 and J1830+063 were observed to monitor the time-dependent antenna gains in both configurations.
For the  configuration the flux was scaled by observing the asteroid Vesta. For the  configuration the flux calibration was achieved by observing MWC349
and the Jovian satellite Callisto.
For bandpass calibration,  quasars 3C 273 and 3C 454.3 were observed for the  and  configuration, respectively. 
The data from different configurations were calibrated separately using the IDL-based MIR package. 
The imaging and data analysis were done with the  miriad software package <cit.>.

 The continuum emission was produced by averaging the line-free channels in the visibility
domain. The 1σ noise for the continuum emission were 3.7 and 1.1 mJy beam^-1 for the 
compact and very-extended configurations, respectively. For spectral lines, the 1σ noise were 
55 and 45 mJy beam^-1 per channel for the compact and very-extended configurations, respectively 
(see Table <ref> for detected lines).

Since the extent of the shortest baseline in the SMA observations is 12 m, corresponding to ∼30 at 225 GHz, more extended spatial structures are resolved out. This spatial filtering mainly affects  the low density tracers, such as  at velocities close to the systemic velocity of the cloud (v_ = 85.2 ).

To recover the missing short spacing information, we observed the ^12CO(2–1) emission at ∼11 with the IRAM 30 m telescope located in Pico Veleta, Spain. A 140 × 140region centered at the same position of the interferometric observations was observed. The receiver was tuned to 230.538 GHz. The spectra have 0.4  spectral resolution and were processed using class.
The combination of the SMA and the IRAM data was performed using miriad <cit.>.





§ RESULTS




lcccccccc[!htbp]

Parameters of the Observed Lines.
0pt
Line   Freq.    E_u/k_   Config   S_ul   1σa 
     [GHz]    [K]         [ //] 
CH_3CH_2CN(24_2,22-23_2,21)   219.505   135.6   COM   23.83    0.21

C^18O(2-1)   219.560   15.8   COM   2.00     1.19

HNCO(10_2,8-9_2,7)   219.737   231.1   COM+VEX   9.60     0.16 

HNCO(10_0,10-9_0,9)   219.798   58.0   COM+VEX   9.73    0.20

H_2^13CO(3_1,2-2_1,1)   219.909   32.9   COM   2.67    0.16

SO(6_5-5_4)   219.949   35.0   COM+VEX   5.95    0.32

CH_3OH(8_0,8-7_1,6)E   220.079   96.6   COM+VEX   1.21   0.19  
 
H_2CCO(11_1,11-10_1,10)   220.177   76.4   COM   10.91    0.15 
 
^13CO(2-1)   220.399     11.0   COM+VEX   2.00    0.91

CH_3CN(12_8-11_8)   220.476     525.6   COM+VEX   6.67   0.10 

CH_3CN(12_7-11_7)   220.539     418.6   COM+VEX   7.92    0.10

HNCO(10_1,9-9_1,8)   220.585     101.5   COM+VEX   9.52    0.18

CH_3CN(12_6-11_6)   220.594     325.9   COM+VEX   9.00   0.13 

CH_3CN(12_5-11_5)   220.641     247.4   COM+VEX   9.92     0.12

CH_3CH_2CN(25_2,24-24_2,23)   220.661   143.0   COM    24.80   0.23 

CH_3CN(12_4-11_4)   220.679     183.1   COM+VEX   10.67    0.28 

CH_3CN(12_3-11_3)   220.709     133.2   COM+VEX   11.25    0.22

CH_3CN(12_2-11_2)   220.730     97.4   COM+VEX   11.6     0.20

CH_3CN(12_1-11_1)   220.743     76.0   COM+VEX   11.92    0.10

CH_3CN(12_0-11_0)   220.747     68.9   COM+VEX   12.00    0.11 

CH_3OH(15_4,11-16_3,13)E   229.589     374.4   COM+VEX   1.61    0.19

CH_3OH(8_-1,8-7_0,7)E   229.759   89.1   COM+VEX   1.77    0.17

CH_3OH(19_5,15-20_4,16)A^+   229.864   578.6   COM   2.00     0.11

CH_3OH(3_-2,2-4_-1,4)E   230.027     39.8   COM+VEX   0.26     0.19

CH_3OCH_3(17_2,15-16_3,14)   230.234     147.7   COM   2.98    0.19

O^13CS(19-18)    230.317    110.5   COM   19.00    0.11

^12CO(2-1)    230.538   16.6   COM+VEX   2.00     2.38

OCS(19-18)   231.061     110.9   COM+VEX   19.00    0.22

^13CS(5_0-4_0)   231.221     26.7   COM+VEX   10.00   0.25 

CH_3OH(10_2,9-9_3,6)A^-   231.281   165.3   COM+VEX   0.93   0.25 

CH_3CH_2CN(27_0,27-26_1,26)   231.312   157.7   COM+VEX   23.17   0.12 

 Molecular line, rest frequency, energy in the upper state, SMA configuration in which the line was detected, line strength, and sigma for the integrated intensity maps. 
aThe noise level per channel is of the order of 50 mJy beam^-1. Panels in Figure <ref> and <ref> have different integration ranges in velocity.  
In this table, we summarize the 1σ level used in each panel for each molecule. 











 §.§ Continuum Emission


Figure  <ref> shows the dust continuum emission at 1.3 mm (225 GHz) obtained
with the configuration as well as the observations with the   configuration.
The configuration shows a bright source elongated along the north-east south-west direction, similar to 
the torus structure observed by <cit.> at 7 mm, and a weaker component nearly perpendicular that has the 
same direction of the molecular outflow (see Section <ref>). The integrated emission in the whole region above the 3σ level is 503 mJy. To obtain the flux associated with the more compact emission, we fitted a 2-D Gaussian using the CASA software package. The measured integrated intensity was 380 mJy with a deconvolved size of 22 × 
17 (14,700 × 11,400 AU at 6.7 kpc). 


For the configuration the integrated intensity above 3σ is 168 mJy. A 2-D Gaussian fit to the most 
compact emission gives a deconvolved size of 08 × 05 (5,400 × 3,300 AU at 6.7 kpc) and an 
integrated intensity of 125 mJy.  The dust continuum peak  is located  at the same position of the 87 GHz and 46 GHz continuum emission peaks detected by <cit.>. We detect no emission toward the secondary 87 GHz peak detected by <cit.> at (R.A.,Dec)_= (18^59^09.21^,0412226).




 §.§ Spectral Lines



Figure <ref> shows the observed spectral bandpass (averaged in time and baseline) of the visibility dataset around 220 and 230 GHz of the lower and upper sidebands obtained with  the compact configuration. All the lines identified in the configurations were also detected in the configuration (see Table <ref> for details).

  The spectra reveal a chemically-rich core with 31 lines from 14 species with a broad range of energy levels (11.0 K for (2–1) up to 525.6 K for CH_3CN(12_8–11_8)).  The identification of lines is based on frequencies and line strengths listed in the Splatalogue Spectral line database.[http://www.splatalogue.net/]
 The lines detected include three CO isotopologues (^12CO, ^13CO, and C^18O), sulfur-bearing species (SO, 
 O^13CS, OCS, and ^13CS), and the dense gas tracers CH_3CN and CH_3OH  that usually arise from hot cores. 

 We produce the integrated intensity maps of all the detected lines. For lines identified in both configurations, we make integrated maps combining the two datasets. 
Most of the species show compact spatial emission coincident with the dust continuum (Figure <ref> and <ref>). 
 However, some of them show elongated emission in the same direction of the continuum bridge (Figure  <ref>). This direction is the same of the molecular outflow discussed in Section <ref>.  
 Table <ref> lists the molecular and observational parameters of  all the detected lines.   























 §.§ Temperature














We detect nine components of the  k-ladder with k=0-8 (Table <ref>).
CH_3CN is a symmetric top molecule, with a  large line strength and dipole moment (3.91 D). The  CH_3CN(12_k–11_k) level is well-suited for measuring the gas temperature in hot cores <cit.>. Since radiative processes across k-ladders are forbidden, the population in the different k-ladders can be used to estimate the kinetic temperature even if the levels are not fully thermalized.  

We have simultaneously fit all CH_3CN transitions with the simple model described  by <cit.> and <cit.>  assuming 
local thermodynamic  equilibrium (LTE) conditions[The Python script used for fitting the CH_3CN(12_k–11_k) transitions and determining the rotational temperature and column density can be obtained from the following 
link: https://github.com/xinglunju/emanon]. The separation of the different transitions is restricted by their 
rest frequency and we have assumed that all lines have the same velocity dispersion and filling factor. The free parameters in the fitting are 
the rotational temperature, column density, line width, and filling factor. The optical depth was calculated using the best-fit temperature, column density, and line width, following Equation A8 of <cit.> (we detected no isotopologue of CH_3CN).  



The CH_3CN spectra and the best-fit model are shown in Figure <ref>. The best fit resulted in a 
rotational temperature, T_ rot, of 240 ± 20 K and a column density, N_ tot, of (7.3 ± 1.0) ×
 10^16 cm^-2, values similar to those found in other hot cores <cit.>.
 

 







 §.§ Mass of the Core


<cit.> derived a spectral index of β=1.3 by fitting a greybody to the SED of , indicating that the entire millimeter continuum from the source is attributable to thermal emission from dust. 
We adopt the rotational temperature T=45 K derived by <cit.> using NH_3 line observations as the dust temperature in the region since this is more representative of the extension of the dust emission in the compact configuration.  
For optically thin and isothermal emission, the mass of the core can be obtained from the expression  

    M_gas=S_1.3mmD^2/R_dgk_1.3mmB_1.3mm(T_d),

where S_1.3mm is the integrated flux density at 1.3 mm,
 D is the distance to the source,
R_dg is the dust-to-gas mass ratio with a value of 0.01,
B_1.3mm(T_d) is the Planck function at the dust temperature T_d, and
k_1.3mm is the dust absorption coefficient  assumed to be equal to 
0.9 cm^2 g^-1 at 230 GHz <cit.>. 



Assuming T=45 K and using the integrated flux from the 2-D Gaussian fitting,  we obtain a gas mass of 150  and 50  for the   and the configuration, respectively. Using the temperature of 240 K derived from the k-ladders of the CH_3CN(12-11) line, the measured mass for the configuration is 8 .  

This mass of 8  corresponds to the mass of the central, dense compact (∼4,000 AU) hot core.










 §.§ Molecular Outflow














The , ,  and  spectra show emission in an  extended velocity range
 (Figure <ref>).
 The CO isotopologue spectra  show dips around the systemic velocity = 85.2 . The dips are  likely caused by both self-absorption  and  missing flux of the extended cloud envelope in the interferometer data. The interferometric spatial filtering affects the  line strongest since it is the most abundant isotopologue and traces the most extended regions that cannot be covered by the shortest baselines of the interferometer.
 We recover the missing flux of  by combining in the visibility domain the single-dish data from the IRAM 30 m telescope and the interferometric data  <cit.>.   
 
 Figure <ref>  shows the channel maps produced using  the SMA+IRAM observations of . 
The channel maps show emission extending in north-west south-east direction in a velocity range of Δv = 30 km s^-1, tracing a molecular outflow in the same direction as the bipolar molecular outflow delineated in SiO 
emission by <cit.>. Figure <ref> shows the integrated intensity maps of the wing emission for the , , and  lines.  We excluded in the integration the velocity range associated with the ambient cloud (81–89 ), as defined by molecular emission that seems unaffected by the outflow. 

 The outflow maps reveal emission centered at the position of the dust core.  
  Using the  line from the combined interferometric and single-dish data set,  we compute mass, momentum, and energy of the outflow following the procedure described in <cit.>. We assume optically-thin emission and an excitation temperature of 70 K.  With a total mass of 16.8 
  , the molecular outflow is consistent with other molecular outflows found in high-mass star-forming regions 
  <cit.>.
  It has a mass ∼60% lower than the 27 
   derived by <cit.> using SiO. This discrepancy can be produced by the more uncertain conversion factor from SiO to H_2 column than from CO to H_2, and by the assumption of optically thin CO emission. Indeed, CO wing emission with an optical depth of 1 would increase the mass to the same value measured using SiO.  The parameters of the outflow are shown in Table <ref>.


<cit.> identified four compact and narrow line NH_3(3,3) emission features that likely arise from a weak population inversion (labeled as “A", “B", “C", and “D" in Figure <ref> and <ref>). 
They suggest that these NH_3(3,3) features are associated to the outflow activity in the region and that “C" and “D" could be part of an outflow driven by an undetected core 
located between them. We detect no dust continuum core (nor hot core line emission) between “C" and “D" and no hint of a molecular outflow 
other than the one driven by the bright dust continuum core. Given the position of these features in the channel 
map of CO, we conclude that they are all associated with the outflow emanating from the massive dust core. 




  
  
lccc

Parameters of the outflow derived from the  emission.
0pt

   Mass    Momentum    Energy 

Lobe   ()    ()    ( km^2 s^-2)

Blue      11.4      105     600 

Red     5.4         45     240

Total     16.8      150     840 


  
  
 
   








 §.§ Velocity gradients


We investigated the  velocity gradients for all the detected lines in  and find no clear trend for rotational structures at 
4,000 AU scales. As an example, we present in Figure <ref> the moment one and the position-velocity maps for three spectral lines 
(CH_3OH(10_2,9-9_3,6)A, CH_3CN(12_3-11_3), and OCS(19-18)). Position-velocity maps were made in a direction roughly perpendicular to the direction of the molecular outflow. The absence of velocity gradients 
does not rule out the existence of an accretion disk (sizes <1,000 AU) feeding the central high-mass star(s), but discards the 
presence of a toroidal-rotating structure at several thousand AU scales.  













§ DISCUSSION AND CONCLUSION



We detected a variety of spectral lines as well as 1.3 mm continuum emission which allowed us to measure the mass and temperature of the compact core embedded in . Molecular emission at high-velocities (e.g., CO and SO) reveal a bipolar molecular outflow for which we determine its properties. This molecular outflow is roughly perpendicular to the torus-like structure detected by <cit.> at 7 mm continuum (also seen at the low angular resolution with SMA). However, molecular tracers often used to study core rotation (e.g., CH_3CN) show no clear signs of rotating structures. 


Theories of massive star formation predict that outflows must be powered and fed by accretion disks. Evidence of rotation and infall that hint at the presence of disks has been detected in several systems <cit.>. 
However, the velocity structures shown in Figure <ref>  indicate that there is no dominant angular momentum
axis in the hot core at a spatial scale of 4000 AU. The size scale of the accretion disk responsible for driving the CO outflow must be much smaller. Small disks are expected in dense cluster forming regions as cores harboring massive stars tend to fragment and form multiple stars. The dynamical interactions limit the size of circumstellar disks. In addition, the complex velocity structures seen in the CH_3OH, CH_3CN and OCS emission may also be partly due to the influence of the molecular outflow, which affects the kinematics and chemistry of the gas.



 High-mass stars are overwhelmingly observed in binary or multiple systems. Indeed, in a high-resolution spectroscopic survey
 including nearly 800 O- and B-type stars, 82% of high-mass stars were found in close binary systems <cit.>.
  In addition, the majority of high-mass stars are paired with high-mass companions <cit.>. 
  We cannot rule out the formation of a binary or multiple system embedded in the  hot core. By comparing the 
  structure of the continuum emission observed with the compact and very-extended configurations, we can see that 
  some substructures are detected, but not resolved. It is possible that rotational motions are present on smaller scales unaccessible with our SMA observations. 
  Indeed, in the nearby high-mass star-forming region NGC 6334I, at least 4 high-mass stars are in the 
  process of formation in less that 2,500 AU <cit.>. 
  Higher spatial resolution will be needed to search for possible multiplicity in . 

<cit.> and recently <cit.> suggest that in IRAS 17233-3606 the CH_3CN emission, typically 
used to reveal rotating structures (toroid-disk-like), can be affected by molecular outflows. This is particularly interesting 
in the study of  <cit.>  at 006 resolution (130 AU scales), in which the P-V diagrams show Keplerian motions 
and contamination that is attributed to both infall and molecular outflows even in high-excitation CH_3CN(37_k-36_k) transitions 
(E_u∼1,000 K). Therefore, high angular resolution observations in  are not only necessary to resolve possible 
further fragmentation, but also to clarify if CH_3CN and the other observed hot core tracers have contamination 
from processes other than rotation that are unresolved at the SMA angular resolution, precluding the detection of disks. 
Interestingly, the recent observations of CH_3CN(5-4) in  at 1 resolution by <cit.> show a 
velocity gradient in the direction of the jet/outflow. Their observations support the idea that CH_3CN emission can 
be contaminated by outflowing gas. This velocity gradient is likely not evident in our CH_3CN(12-11) lines because the 
higher transitions will be excited at higher temperatures, closer to the high-mass star and confusion from both 
physical processes, rotation and outflowing gas, can be more important than at lower energy transitions.  This is supported by the lower filling factor of 0.03 derived in this work for CH_3CN(12-11) with respect to 0.17 derived 
by  <cit.> for  CH_3CN(5-4). 

In summary, we have examined the continuum and spectral line emission and draw the following conclusions:

1. Using SMA in the compact and very extended configurations, we have observed 1.3 mm continuum and molecular line emission  toward  to reveal a chemically-rich, compact core with a  mass of 8  (50  at 45 K) and central temperature of 240 K that drives a bipolar molecular outflow with a total mass of 16.8 M_⊙. 

2. The molecular outflow in CO and SO is consistent with the previously detected outflow in SiO. The molecular outflow 
is roughly perpendicular to the torus structure detected in continuum emission with the compact configuration <cit.>. However, this torus shows substructures at higher angular resolution and present 
no velocity gradients that would suggest a toroidal-disk-like rotating structure. 

3. We suggest that the lack of rotational structures is due to multiplicity of high-mass stars embedded in the hot 
core and possibly the influence of the outflow (and maybe infall) in the hot core tracers used to search for 
velocity gradients. Higher angular resolution, likely with ALMA, can confirm or refute both scenarios. 


We  thank the anonymous referee for helpful comments that improved the paper.
Data analysis was in part carried out on the open use data analysis computer system 
at the Astronomy Data Center, ADC, of the National Astronomical Observatory of Japan.



SMA, IRAM

MIRIAD <cit.>, Python[https://www.python.org], emanon[https://github.com/xinglunju/emanon], CASA <cit.>, CLASS[http://www.iram.fr/IRAMFR/GILDAS]
          


  
 




  





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