J/ApJ/854/170 Methanol (CH3OH) and OH masers in NGC 6334I (Hunter+, 2018)
The extraordinary outburst in the massive protostellar system NGC 6334I-MM1:
emergence of strong 6.7GHz methanol masers.
Hunter T.R., Brogan C.L., MacLeod G.C., Cyganowski C.J., Chibueze J.O.,
Friesen R., Hirota T., Smits D.P., Chandler C.J., Indebetouw R.
<Astrophys. J., 854, 170 (2018)>
=2018ApJ...854..170H 2018ApJ...854..170H
ADC_Keywords: Masers; Interstellar medium; Radio continuum
Keywords: ISM: individual objects (NGC 6334I) ; ISM: magnetic fields ; masers ;
radio continuum: ISM ; stars: formation ; stars: protostars
Abstract:
We report the first sub-arcsecond VLA imaging of 6GHz continuum,
methanol maser, and excited-state hydroxyl maser emission toward the
massive protostellar cluster NGC 6334I following the recent 2015
outburst in (sub)millimeter continuum toward MM1, the strongest
(sub)millimeter source in the protocluster. In addition to detections
toward the previously known 6.7GHz Class II methanol maser sites in
the hot core MM2 and the UCHII region MM3 (NGC 6334F), we find new
maser features toward several components of MM1, along with weaker
features ∼1" north, west, and southwest of MM1, and toward the
nonthermal radio continuum source CM2. None of these areas have
heretofore exhibited Class II methanol maser emission in three decades
of observations. The strongest MM1 masers trace a dust cavity, while
no masers are seen toward the strongest dust sources MM1A, 1B, and 1D.
The locations of the masers are consistent with a combination of
increased radiative pumping due to elevated dust grain temperature
following the outburst, the presence of infrared photon propagation
cavities, and the presence of high methanol column densities as
indicated by ALMA images of thermal transitions. The nonthermal radio
emission source CM2 (2" north of MM1) also exhibits new maser emission
from the excited 6.035 and 6.030GHz OH lines. Using the Zeeman effect,
we measure a line-of-sight magnetic field of +0.5 to +3.7mG toward
CM2. In agreement with previous studies, we also detect numerous
methanol and excited OH maser spots toward the UCHII region MM3, with
predominantly negative line-of-sight magnetic field strengths of -2 to
-5mG and an intriguing south-north field reversal.
Description:
In this paper, we present follow-up observations of NGC 6334I with the
National Science Foundation's Karl G. Jansky Very Large Array (VLA) in
5cm continuum, the 6.7GHz CH3OH transition, and multiple transitions
of excited-state OH. The relatively nearby distance to the source
(1.3±0.1kpc) allows us to achieve a linear resolution of ∼500au.
The VLA observations were made in 2016 Oct 29 and 2016 Nov 19 in the
C band (5GHz,7GHz) and in 2011 May 23 in the K band (24.059GHz,
25.406GHz --1.3cm).
Objects:
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RA (ICRS) DE Designation(s)
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17 20 53.35 -35 47 01.5 NGC 6334I = NAME NGC 6334-I
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 69 647 Fitted properties of the 6.7GHz methanol masers
table3.dat 84 20 Summary of 6.7GHz methanol maser associations
table4.dat 68 49 Fitted properties of the OH 6.030GHz masers
(left circular polarization)
table5.dat 69 50 Fitted properties of the OH 6.030GHz masers
(right circular polarization)
table6.dat 68 139 Fitted properties of the OH 6.035GHz masers
(left circular polarization)
table7.dat 68 134 Fitted properties of the OH 6.035GHz masers
(right circular polarization)
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See also:
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
J/A+A/316/102 : JHK Photometry in NGC 6334 (Tapia+, 1996)
J/MNRAS/301/640 : Ultracompact H II regions studies. II. (Walsh+, 1998)
J/A+A/466/989 : Hot ammonia from NGC 6334I and NGC 6334I(N) (Beuther+, 2007)
J/ApJ/668/331 : OH masers in W3(OH) (Fish+, 2007)
J/A+A/481/169 : ATCA 3mm obs. of NGC 6334I and NGC 6334I(N) (Beuther+, 2008)
J/ApJ/702/1615 : CH3OH maser survey of EGOs (Cyganowski+, 2009)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJ/767/36 : APEX observations of HOPS protostars (Stutz+, 2013)
J/MNRAS/431/1752 : ATLASGAL 6.7GHz methanol masers (Urquhart+, 2013)
J/ApJ/778/96 : Spitzer and NEWFIRM observations of NGC 6334 (Willis+, 2013)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
J/ApJ/832/187 : ALMA & VLA radio continuum obs. of NGC 6334I (Brogan+, 2016)
J/MNRAS/465/3011 : VVV high amplitude NIR var. stars (Contreras Pena+, 2017)
J/ApJ/851/L46 : CH3OCH2OH ALMA detection in NGC 6334I (McGuire+, 2017)
Byte-by-byte Description of file: table[24567].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/647] Internal index number (1)
5- 14 A10 --- Assoc Association
16- 21 F6.2 km/s VChan [-19/-1.5] Velocity channel
23- 24 I2 h RAh [17] Hour of Right Ascension (J2000)
26- 27 I2 min RAm [20] Minute of Right Ascension (J2000)
29- 35 F7.4 s RAs [53.1/53.6] Second of Right Ascension (J2000)
37 A1 --- DE- [-] Sign of the Declination (J2000)
38- 39 I2 deg DEd [35] Degree of Declination (J2000)
41- 42 I2 arcmin DEm [46/47] Arcminute of Declination (J2000)
44- 49 F6.3 arcsec DEs Arcsecond of Declination (J2000)
51- 61 F11.6 Jy Flux [0.006/1820] Flux density
63- 69 F7.5 Jy e_Flux [0.001/1] Uncertainty in Flux (2)
--------------------------------------------------------------------------------
Note (1): Entries are sorted by velocity.
Note (2): Uncertainty in the fitted value. Does not include the flux
calibration uncertainty.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Assoc Association identification (and total)
12- 13 I2 h RAh [17]? Hour of right ascension (J2000)
15- 16 I2 min RAm [20]? Minute of right ascension (J2000)
18- 23 F6.3 s RAs [53.13/53.5]? Second of right ascension (J2000)
25 A1 --- DE- [- ] Sign of declination (J2000)
26- 27 I2 deg DEd [35]? Degree of declination (J2000)
29- 30 I2 arcmin DEm [46/47]? Arcminute of declination (J2000)
32- 36 F5.2 arcsec DEs ? Arcsecond of declination (J2000)
38- 46 F9.4 Jy.km/s Flux [0.09/3420] 6.7GHz integrated flux
48- 53 F6.2 km/s Velmin [-18.8/-4.5] Minimum velocity
55- 60 F6.2 km/s Velpk [-11.2/-3.5] Peak velocity
62- 66 F5.2 km/s Velmax [-9.1/-1.5] Maximum velocity
68- 75 F8.3 Jy FluxPk [0.1/1820]? 6.7GHz peak flux density
77- 84 F8.4 10+6K TB [0.01/307]? Lower limit to the brightness
temperature TB (1)
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Note (1): Lower limits to the brightness temperature TB using the synthesized
beam; the physical sizes of the maser spots are likely to be smaller
than the beam (∼520au).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Nov-2018