J/ApJ/906/23 A VLBA Survey of radio stars in the ONC. I. (Forbrich+, 2021)
A VLBA Survey of Radio Stars in the Orion Nebula Cluster.
I. The Nonthermal Radio Population.
Forbrich J., Dzib S.A., Reid M.J., Menten K.M.
<Astrophys. J., 906, 23 (2021)>
=2021ApJ...906...23F 2021ApJ...906...23F
ADC_Keywords: Clusters, open; Radio sources; Stars, radio; Positional data
Keywords: Non-thermal radiation sources ; Star formation ; Radio
astrometry
Abstract:
We present first results of a four-epoch VLBA survey for nonthermal
emission toward all 556 compact radio sources previously identified in
a deep VLA survey of the Orion Nebula Cluster (ONC). We identify VLBA
counterparts toward an unprecedented 123 sources. Of these, 41 do not
have X-ray counterparts, of which 34 also do not display near-infrared
counterparts. Since these cannot be explained by extragalactic
background sources, this suggests a component of the ONC population of
young stellar objects that are too deeply embedded for even X-rays to
be detectable. We find pervasive variability and detect even most of
the highest-S/N sources in only one out of four epochs. Neither a
negative spectral index nor extreme variability in the VLA data is a
good predictor of a VLBA detection.
Description:
We have observed the Orion Nebula Cluster (ONC) with the Very Long
Baseline Array (VLBA) on four occasions. The first observation was
carried out on 2015 October 26 (BF117). In a follow-up program
(BF123), three more observations were obtained on 2017 October 26 and
27 and on 2018 October 26. Observations were carried out in C-band at
2Gbps in dual polarization with an aggregate bandwidth of 256MHz in a
frequency range of 7.068-7.324GHz, using the Roach board-based Digital
Backend with its Polyphase Filter Bank.
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 75 123 List of VLBA detections in the Orion Nebula Cluster
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See also:
J/ApJ/405/498 : Counts and spectral indices at 8.44GHz (Windhorst+, 1993)
J/ApJS/160/353 : Membership of the Orion nebula population (Getman+, 2005)
J/ApJS/160/319 : COUP; observations and source lists (Getman+, 2005)
J/ApJ/677/401 : Xray properties of protostars in ONC (Prisinzano+, 2008)
J/AJ/146/85 : Spectral types 1576 optical stars in ONC (Hillenbrand+, 2013)
J/A+A/551/A97 : Lockman Hole/XMM VLBI observations (Middelberg+, 2013)
J/ApJ/822/93 : Population of compact radio sources in ONC (Forbrich+, 2016)
J/A+A/587/A153 : VISION I. VISTA Orion A Survey (Meingast+, 2016)
J/A+A/607/A132 : VLBA observations of the COSMOS field (Herrera Ruiz+, 2017)
J/ApJ/834/142 : Gould's Belt Distances Survey. II. OMC (Kounkel+, 2017)
J/ApJ/906/24 : A VLBA Survey of Radio Stars in the ONC. II. (Dzib+, 2021)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- [FRM2016] Identifier
5 A1 --- f_[FRM2016] Sources flagged only fulfill the selection
criterion in the concatenated epoch BF123AB
7- 10 I4 --- COUP [107/1473]? COUP identifier of the source
12- 27 A16 --- VISION VISION NIR (1)
29 I1 --- NS/N [0/4] Number of S/N>6.5
31- 35 F5.1 --- S/N [6.5/215] Maximum S/N
37- 38 A2 --- Epoch Epoch of S/N (2)
40- 42 I3 mas Sep [5/663]? Separation between detection and nominal
VLA position
44- 75 A32 --- Note Additional note or comment (3)
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Note (1): From Meingast+, 2016, J/A+A/587/A153 unlisted detections (e.g., due
to crowding) listed as "(det)."
Note (2): BF117 (7), BF123ABC (A,B,C), or the concatenated epoch BF123AB (AB)
Note (3): Previous identifications: YSO classes from
Prisinzano+, 2008, J/ApJ/677/401 and spectral types summarized from
Hillenbrand+, 2013, J/AJ/146/85. Note that these are for counterparts
within 0."5 and do not necessarily represent counterparts of the radio
sources, particularly in the case of multiple systems. See Paper II
for a detailed discussion.
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History:
From electronic version of the journal
References:
Dzib et al. Paper II : 2021ApJ...906...24D 2021ApJ...906...24D Cat. J/ApJ/906/24
(End) Prepared by Coralie Fix [CDS], 20-May-2022