J/ApJ/581/325 NGC 2071 water masers (Seth+, 2002)
Water masers as tracers of protostellar disks and outflows in the
intermediate-mass star-forming region NGC 2071.
Seth A.C., Greenhill L.J., Holder B.P.
<Astrophys. J. 581, 325 (2002)>
=2002ApJ...581..325S 2002ApJ...581..325S
ADC_Keywords: H II regions ; Masers ; Radio sources
Keywords: H II regions - ISM: individual (NGC 2071) - ISM: jets and outflows -
masers - stars: formation
Abstract:
We have mapped the water maser emission associated with the infrared
centers IRS 1 and IRS 3 of the NGC 2071 IR star-forming region at four
epochs over ∼4 months with the Very Long Baseline Array. We detected
269 maser features with ∼1km/s line widths and measured 30 proper
motions. In each infrared center, the water maser emission appears to
trace parts of a protostellar disk and collimated outflow.
Description:
We observed the 616-523 transition of water (rest frequency
22235.080MHz) toward NGC 2071 IR with the Very Long Baseline Array
(VLBA) of the NRAO1 at four epochs in 1996 (see Table 1). A single
antenna of the VLA augmented the VLBA, which provided improved
sensitivity to emission extended on several milliarcsecond scales. A
16MHz (∼215km/s) recording bandwidth, centered on VLSR=4.66km/s,
covered the known velocity range of emission. We processed the data
with the VLBA correlator, obtaining 512 spectral channels with a
separation of 0.42km/s.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 83 269 Water Maser Features in NGC 2071 IRS1 & IRS3
table3.dat 77 30 Water Maser Proper Motions in NGC 2071 IRS1 & IRS3
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See also:
J/ApJ/463/205 : CS and NH3 Survey of H2O Maser Emission (Anglada+ 1996)
Table 1: Journal of 1996 VLBA Observations
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Date Track Beam PA rms noise Maser Maser
(hr) (mas) (deg) (Jy) spots features
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Mar 24 8 0.92x 0.51 -9 0.014 337 74
Jun 2 8 1.08x 0.59 -1 0.016 259 67
Jul 5 8 1.03x 0.57 8 0.016 310 81
Aug 3 8.5 1.36x 1.26 24 0.023 168 47
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- IRS Object name (IRS1 or IRS3) (G1)
6- 9 A4 --- Maser Maser identification number (1)
11- 15 F5.2 km/s RV Radial velocity
17 A1 --- l_RV Limit flag on RV error
19- 22 F4.2 km/s e_RV Uncertainty in RV (2)
24- 29 F6.3 Jy Speak Peak fitted flux density
31- 35 F5.3 Jy e_Speak Uncertainty Speak
37- 44 F8.3 mas EWOff Relative position East-West
46- 50 F5.3 mas e_EWOff Uncertainty in EWOff
52- 59 F8.3 mas NSOff Relative position North-South
61- 65 F5.3 mas e_NSOff Uncertainty in NSOff
67- 68 I2 --- SChan Number of contributing spectral channels
70- 74 F5.3 km/s HPFW ? Half Power Full Width of fitted Gaussian (3)
76- 80 F5.3 km/s e_HPFW ? Uncertainty in HPFW
82- 83 I2 --- MNum ? Associated proper motion number (4)
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Note (1): Maser identification number:
The first digit represents the epoch number (1-4)
The last number represents the Maser feature number (0-48)
Note (2): The uncertainty in the radial velocity is assumed to be one-half
channel (.21km/s) for features composed of three or fewer spots.
Note (3): Quoted for features with line profiles fit to a Gaussian model.
Note (4): For features with measured proper motions, entries indicate the
identification numbers of motions, as enumerated in Table 3.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- IRS Object name (IRS1 or IRS3) (G1)
6- 7 I2 --- MNum Associated proper motion number
9 A1 --- f_MNum [cd] Flag on MNum (1)
11- 15 F5.2 km/s RV Radial velocity
17- 24 F8.3 mas EWOff Relative position East-West
26- 33 F8.3 mas NSOff Relative position North-South
35- 40 F6.2 km/s EWVel Measured East-West proper motion expressed as
a velocity (2)
42- 45 F4.2 km/s e_EWVel Uncertainty in EWVel
47- 52 F6.2 km/s NSVel Measured North-South proper motion expressed as
a velocity (2)
54- 57 F4.2 km/s e_NSVel Uncertainty in NSVel
59- 62 A4 --- ID1 Epoch1 maser feature identification number
64- 67 A4 --- ID2 Epoch2 maser feature identification number
69- 72 A4 --- ID3 Epoch3 maser feature identification number
74- 77 A4 --- ID4 Epoch4 maser feature identification number
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Note (1): Flag on associated proper motion number as follows:
c = IRS3 motion 6 is zero because the corresponding feature was used
to align the maps of the four epochs.
d = IRS1 motion 12 corresponds to the maser feature used to align the
maps of the four epochs. An offset is added to all the motions
so that the net apparent motion of the IRS1 region is zero.
Motion 12 corresponds to that offset.
Note (2): Assuming a distance of 390pc.
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Global notes:
Note (G1): Nomenclature:
Objects are identified as [SGH2002b] IRS1 N NN and
[SGH2002b] IRS3 N NN in Simbad
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History:
* 06-Feb-2003: From electronic version of the journal
* 29-Dec-2005 : Some MNum numbers were corrected in table2
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 06-Feb-2003