J/ApJ/906/24 A VLBA Survey of Radio Stars in the ONC. II. (Dzib+, 2021)
A VLBA Survey of Radio Stars in the Orion Nebula Cluster.
II. Astrometry.
Dzib S.A., Forbrich J., Reid M.J., Menten K.M.
<Astrophys. J., 906, 24 (2021)>
=2021ApJ...906...24D 2021ApJ...906...24D
ADC_Keywords: Clusters, open; Radio sources; Stars, radio; Positional data
Keywords: Star formation ; Radio astrometry ; Non-thermal radiation
sources
Abstract:
From Very Long Baseline Array (VLBA) observations we previously
identified a population of 123 young stellar systems with nonthermal
radio emission toward the core of the Orion Nebula Cluster (ONC). We
find optical sources in the Gaia DR2 catalog for 34 of them within 0.2
of the radio positions. Most of the radio sources are likely
companions of Gaia detections. However, there are 11 stars whose VLBA
positions differ from Gaia by <1.6mas, and some of these radio sources
probably are the direct counterparts of the optical stars. We are able
to obtain radio proper motions for 23 stars. Combining the stellar
proper motions derived from the VLBA and Gaia DR2 data we find the
global motion and velocity dispersion of the ONC to be
(µα*,µδ)=(1.20±0.09,0.18±0.09)mas/yr and
(σµα,σµδ)=(0.84±0.09,1.30{+/
-}0.09)mas/yr. Finally, we looked for ordered motions by estimating
the means of scalar and vectorial products, which results in
n.r=-0.61±1.00km/s and νxr=0.57±0.95km/s. These
do not show indications that the young stellar cluster is in
expansion, contraction, or rotation.
Description:
Four C-band observations, centered at 7.196GHz, were carried out with
the VLBA in three different years. Three of these observations were
arranged to be made at the same day of the year, October 26, in 2015,
2017, and 2018. More details about observations are given in Paper I
(Forbrich+, 2021, J/ApJ/906/23).
Objects:
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RA (2000) DE Designation(s)
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05 35.0 -05 29 NAME Orion Nebula Cluster = NAME ONC
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 106 175 Positions of detected sources in the VLBA images
and their formal errors as derived from Imfit
table3.dat 99 23 Sources with determined proper motions from VLBA
observations
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997)
J/ApJS/160/353 : Membership of the Orion nebula population (Getman+, 2005)
J/ApJ/748/14 : ONC population data from WFI observations (Da Rio+, 2012)
J/AJ/146/85 : Spectral types 1576 optical stars in ONC (Hillenbrand+, 2013)
J/ApJ/790/49 : Gould's Belt VLA survey. III. Orion region (Kounkel+, 2014)
J/ApJ/822/93 : The population compact radio sources in ONC (Forbrich+, 2016)
J/A+A/587/A153 : VISION I. VISTA Orion A Survey (Meingast+, 2016)
J/ApJ/834/142 : Gould's Belt Distances Survey. II. OMC (Kounkel+, 2017)
J/MNRAS/467/L71 : Significance of VLBI/Gaia position offsets (Petrov+, 2017)
J/AJ/157/109 : Stellar proper motions in the Orion Nebula Cluster (Kim+, 2019)
J/ApJ/870/32 : Kinematics in young star clusters & associations (Kuhn+, 2019)
J/AJ/159/272 : Orion Nebula Cluster PMs HST Treasury Program (Platais+, 2020)
J/ApJ/906/23 : A VLBA Survey of radio stars in the ONC. I. (Forbrich+, 2021)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- [FRM2016] Source identifier
7- 9 A3 --- Epoch Epoch of observation
11 A1 --- f_[FRM2016] Source detected at a level between 6.0-6.5
times the images noise flagged with letter b
13- 14 I2 h RAh [5] Hour of right ascension (J2000)
16- 17 I2 min RAm [34/35] Minute of right ascension (J2000)
19- 27 F9.6 s RAs Second of right ascension (J2000)
29- 30 I2 s e_RAs Error on RAs
32 A1 --- DE- [-] Sign of declination (J2000)
34- 35 I2 deg DEd [5/5] Degree of declination (J2000)
37- 38 I2 arcmin DEm [20/26] Arcminute of declination (J2000)
40- 48 F9.6 arcsec DEs Arcsecond of declination (J2000)
50- 52 I3 arcsec e_DEs [32/868] Error on DEs; in µarcsec
54- 72 I19 --- Gaia ? Gaia identifier
74 A1 --- f_Gaia [a] Flag on Gaia (1)
76- 80 F5.1 mas Sep [0.5/200]? Total separation between the Gaia
and VLBA
82- 84 F3.1 mas e_Sep [0.2/5]? Error on Sep
86- 91 F6.1 mas SepRA [-195/124]? Separation between the Gaia and
VLBA in RA direction
93- 95 F3.1 mas e_SepRA [0.2/7]? Error on SepRA
97-102 F6.1 mas SepDE [-150/181]? Separation between the Gaia and
VLBA in DE direction
104-106 F3.1 mas e_SepDE [0.2/7]? Error in SepDE
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Note (1): Flag as follows:
a = Source in Gaia DR2 catalog, no proper motion and parallaxes are
given. The angular separations from the radio source are estimated
using the positions in epoch 2015.5 as given in the Gaia DR2 archive.
A Gaia ID source number is also listed when there is coincidence.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- [FRM2016] Source identifier
7 A1 --- f_[FRM2016] [b] Source detected only in two epochs,
the errors may be underestimated
9- 23 A15 --- Name Other identifier
25- 36 A12 --- SpT Spectral type(s) (1)
38- 43 F6.2 mas/yr pmRA-VLBA [-12.1/8.59] Proper motion in RA, VLBA
45- 48 F4.2 mas/yr e_pmRA-VLBA [0.05/0.7] Error on pmRA-VLBA
50- 55 F6.2 mas/yr pmDE-VLBA [-42.2/2.38] Proper motion in DE, VLBA
57- 60 F4.2 mas/yr e_pmDE-VLBA [0.07/2] Error on pmDE-VLBA
62- 66 F5.1 mas Sep [0.4/184]? Total angular separation, GAIA DR2
68- 70 F3.1 mas e_Sep [0.1/2]? Error on Sep
72 A1 --- f_Sep [c] Flag on Sep (2)
74- 78 F5.2 mas/yr pmRA-Gaia [-1.45/3.77]? Proper motion in RA, Gaia DR2
80- 83 F4.2 mas/yr e_pmRA-Gaia [0.1/0.6]? Error on pmRA-Gaia
85- 89 F5.2 mas/yr pmDE-Gaia [-1.72/2.61]? Proper motion in DE, Gaia DR2
91- 94 F4.2 mas/yr e_pmDE-Gaia [0.08/0.5]? Error on pmDE-Gaia
96- 99 F4.2 Msun Mass [0.02/5.6]? Mass lower limit (3)
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Note (1): Spectral types as reported by Hillenbrand+, 2013, J/AJ/146/85,
for multiple systems these do not necessarily represent the
counterparts of the radio sources.
Note (2): Source in Gaia DR2 catalog, no proper motion and parallaxes
are given. The angular separations from the radio source are estimated
using the positions in epoch 2015.5 as given in the Gaia DR2 archive.
Note (3): Estimated from the differences between VLBA and Gaia DR2
proper motions, as discussed in the text.
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History:
From electronic version of the journal
References:
Forbrich et al. Paper I : 2021ApJ...906...23F 2021ApJ...906...23F Cat. J/ApJ/906/23
(End) Prepared by Coralie Fix [CDS], 20-May-2022