J/ApJ/749/47 VLBA 22.2GHz H2O maser features in G28.87+0.07 (Li+, 2012)
Massive star formation toward G28.87+0.07 (IRAS 18411-0338) investigated by
means of maser kinematics and radio to infrared continuum observations.
Li J.J., Moscadelli L., Cesaroni R., Furuya R.S., Xu Y., Usuda T.,
Menten K.M., Pestalozzi M., Elia D., Schisano E.
<Astrophys. J., 749, 47 (2012)>
=2012ApJ...749...47L 2012ApJ...749...47L
ADC_Keywords: Interstellar medium ; Masers ; Radio continuum ; Interferometry
Keywords: ISM: individual objects (G28.87+0.07) - ISM: kinematics and dynamics -
masers - techniques: interferometric
Abstract:
We used the Very Long Baseline Array and the European VLBI Network to
perform phase-referenced very long baseline interferometry
observations of the three most powerful maser transitions associated
with the high-mass star-forming region G28.87+0.07: the 22.2GHz H2O,
6.7GHz CH3OH, and 1.665GHz OH lines. We also performed Very Large
Array (VLA) observations of the radio continuum emission at 1.3 and
3.6cm and Subaru observations of the continuum emission at 24.5µm.
Two centimeter-continuum sources are detected and one of them (named
hot molecular core (HMC)) is compact and placed at the center of the
observed distribution of H2O, CH3OH, and OH masers. The bipolar
distribution of line-of-sight velocities and the pattern of the proper
motions suggest that the water masers are driven by a (proto)stellar
jet interacting with the dense circumstellar gas. The same jet could
both excite the centimeter-continuum source named HMC (interpreted as
free-free emission from shocked gas) and power the molecular outflow
observed at larger scales--although one cannot exclude that the
free-free continuum is rather originating from a hypercompact H II
region. At 24.5µm, we identify two objects separated along the
north-south direction, whose absolute positions agree with those of
the two VLA continuum sources. We establish that ∼90% of the
luminosity of the region (∼2x105L☉) is coming from the radio
source HMC, which confirms the existence of an embedded massive young
stellar object exciting the masers and possibly still undergoing heavy
accretion from the surrounding envelope.
Description:
We observed the HMSFR G28.87+0.07 (tracking center:
RA(J2000=18:43:46.24 and DEC(J2000)=-03:35:30.4) with the VLA at X
(3.6cm) and K (1.3cm) bands in both the C-array (in 2008 April) and
A-array configurations (in 2008 November).
We observed the HMSFR G28.87+0.07 (tracking center: J184346.22-033529.9)
at 22.2GHz with the VLBA in the 616-523 H2O transition (rest
frequency 22.235079GHz). The observations (program code: BM244)
consisted of four epochs: 2006 April 23, 2006 June 30, 2006 September
28, and 2007 January 18.
We observed G28.87+0.07 (tracking center: J184346.22-033529.9) with
the European VLBI Network (EVN) in the 51-60A+ CH3OH transition
(rest frequency 6.66851 GHz). Data were taken in four epochs (program
code: EM061 and EM069) separated by ∼1 year: 2006 February 28, 2007
March 18, 2008 March 18, and 2009 March 17.
And we observed G28.87+0.07 (tracking center: J184346.34-033529.9
with the VLBA in the 2π3/2J=3/2 OH transition (rest frequency
1.665401GHz) on 2007 April 28 (program code: BM244O).
Using the mid-infrared imaging spectrometer (COMICS) at the Cassegrain
focus of the 8.2m Subaru Telescope, we carried out imaging
observations of the 24.5um emission toward G28.87+0.07 on 2008 July
15.
Objects:
------------------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------------------
18 43 46.3 -03 35 29 G028.87+00.07 = GAL 028.87+00.07
------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 70 169 Parameters of VLBA 22.2GHz H2O maser features
in G28.87+0.07
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See also:
J/MNRAS/416/1764 : H2O Southern Galactic Plane Survey (HOPS) (Walsh+, 2011)
J/MNRAS/418/1689 : Red MSX water maser and ammonia emissions (Urquhart+, 2011)
J/ApJS/154/553 : Inner galaxy massive star formation regions (Sewilo+, 2004)
J/ApJ/566/945 : Massive star forming regions at 1.2mm (Beuther+, 2002)
J/A+A/368/845 : Arcetri updates of H2O maser sources. (Valdettaro+, 2001)
J/A+AS/137/43 : OH/H2O masers database (Forster+, 1999)
J/ApJ/463/205 : CS and NH3 Survey of H2O Maser Emission (Anglada+ 1996)
J/A+AS/101/153 : Galactic H2O masers (Palagi+ 1993)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Num [0/168] Feature number
5- 11 A7 --- Epoch [ ,1-4] Epoch(s) of detection (1)
13- 18 F6.2 km/s VLSR [93.3/112] Local Standard of Rest velocity (2)
20- 24 F5.2 Jy Snu [0.1/54]? The VLBA 22.2 GHz flux density (3)
26- 31 F6.2 mas oRA Position offset along Right Ascension (4)
33- 36 F4.2 mas e_oRA [0.05/0.07]? Uncertainty in oRA
38- 45 F8.3 mas oDE Position offset along Declination (4)
47- 50 F4.2 mas e_oDE [0.05/0.2]? Uncertainty in oDE
52- 56 F5.1 km/s VRA [-51/56]? Velocity component along
Right Ascension (5)
58- 60 F3.1 km/s e_VRA [1/4.5]? Uncertainty in VRA
62- 66 F5.1 km/s VDE [-27/22]? Velocity component along Declination (5)
68- 70 F3.1 km/s e_VDE ? Uncertainty in VDE
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Note (1): Epoch as in table 2, as follows:
1 = 2006-Apr-23 (at position J184346.22467-033529.8161)
2 = 2006-Jun-30 (at position J184346.22465-033529.8173)
3 = 2006-Sep-28 (at position J184346.22455-033529.8190)
4 = 2007-Jan-18 (at position J184346.22448-033519.8212)
Note (2): Intensity-weighted, averaged over the observing epoch(s).
Note (3): Of the strongest spot, averaged over the observing epoch(s).
Note (4): Relative to the feature #1, measured at the first epoch of
detection (2006-Apr-23), at position 18:43:46.22467=-03:35:29.8161.
See table 2 for further details.
Note (5): Measured with respect to the reference feature #0.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 12-Nov-2013