J/AJ/157/109 Stellar proper motions in the Orion Nebula Cluster (Kim+, 2019)
Stellar proper motions in the Orion Nebula Cluster.
Kim D., Lu J.R., Konopacky Q., Chu L., Toller E., Anderson J.,
Theissen C.A., Morris M.R.
<Astron. J., 157, 109-109 (2019)>
=2019AJ....157..109K 2019AJ....157..109K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, double and multiple ; Proper motions ;
Photometry, HST
Keywords: open clusters and associations: individual: Orion Nebula Cluster -
proper motions - stars: formation - stars: kinematics and dynamics
Abstract:
The Orion Nebula Cluster (ONC) is the nearest site of ongoing massive
star formation, which allows us to study the kinematics and dynamics
of the region in detail and constrain star formation theories. Using
HST ACS/WFPC2/WFC3IR and Keck II NIRC2 data, we have measured the proper
motions of 701 stars within an ∼6'x6' field of view around the center of
the ONC. We have found more than 10 escaping star candidates, concentrated
predominantly at the core of the cluster. The proper motions of the bound
stars are consistent with a normal distribution, albeit elongated
north-south along the Orion filament, with proper-motion dispersions of
(σµ,α*, σµ,δ)=(0.83±0.02,
1.12±0.03) mas/yr or intrinsic velocity dispersions of
(σv,α*, σv,δ)=(1.57±0.04,
2.12±0.06) km/s assuming a distance of 400 pc to the ONC. The cluster
shows no evidence for tangential-to-radial anisotropy. Our velocity
dispersion profile agrees with the prediction from the observed
stellar + gas density profile from Da Rio et al. (2014ApJ...795...55D 2014ApJ...795...55D,
2017ApJ...845..105D 2017ApJ...845..105D), indicating that the ONC is in virial equilibrium.
This finding suggests that the cluster was formed with a low star formation
efficiency per dynamical timescale based on comparisons with current star
formation theories. Our survey also recovered high-velocity IR sources BN,
x and n in the BN/KL region. The estimated location of the first two
sources ∼500 yr ago agrees with that of the radio source I, consistent
with their proposed common origin from a multistellar disintegration.
However, source n appears to have a small proper motion and is unlikely
to have been involved in the event.
Description:
The observations from HST consisted of 11 epochs between 1995 and 2015
(Prosser et al. 1994ApJ...421..517P 1994ApJ...421..517P; O'dell et al. 1997AJ....114..730O 1997AJ....114..730O;
Rubin et al. 1997ApJ...474L.131R 1997ApJ...474L.131R; O'Dell 2001AJ....122.2662O 2001AJ....122.2662O;
Robberto et al. 2004ApJ...606..952R 2004ApJ...606..952R, 2013, J/ApJS/207/10), mostly with
medium or wide optical/IR passband filters (F435W, F439W, F539M, F555W,
F775W, F791W, and F139M), except for IR filter F130N. All HST archival
images having central coordinates within ∼3.0' of the center of the ONC
were selected. However, only those images with exposure times longer
than 40 s were used in our proper motion (PM) analysis to ensure
sufficiently high signal-to-noise ratios for faint sources.
The HST images were obtained from several different cameras. The ACS/WFC
consists of two 2048x4096 pixel CCD detectors. The plate scale is
50 mas/pixel, which corresponds to a 202"x200" field of view. The WFPC2
uses four 800x800 pixel CCDs where three of them cover a 150"x150" region
(WF) and have a pixel scale of 100 mas/pixel. The fourth CCD (PC) images
a 34"x34" field with a spatial scale of 56 mas/pixel. The WFC3IR channel
uses a single 1024x1024 pixel CCD detector with a plate scale of
130 mas/pixel, corresponding to a 136"x123" field of view. Observations
that were within ∼1 month and with the same instrument were combined to
define a single epoch.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 69 210 HST observation
table3.dat 66 715 Proper motion measurements
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See also:
J/A+AS/118/503 : Proper motions of stars in Ori Nebula (Tian+ 1996)
J/AJ/111/846 : Orion HST survey (O'Dell+ 1996)
J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997)
J/AJ/125/277 : High proper motions in central Orion nebula (O'dell+, 2003)
J/AJ/127/3456 : Internal velocities in the Orion Nebula (Doi+, 2004)
J/AJ/136/2136 : HST/ACS Atlas of Great Orion Nebula proplyds (Ricci+, 2008)
J/ApJ/676/1109 : Velocities of stars in the Orion Nebula Cluster
(Furesz+, 2008)
J/ApJ/697/1103 : Kinematics of Orion Nebula Cluster (Tobin+, 2009)
J/ApJ/722/1092 : Optical photometry of the ONC. II. (Da Rio+, 2010)
J/A+A/534/A10 : HST/NICMOS III imaging in Orion Nebula Cluster
(Andersen+, 2011)
J/ApJ/733/50 : Mid-IR photometric monitoring of the ONC
(Morales-Calderon+, 2011)
J/ApJS/207/10 : HST Treasury Program on the ONC (Robberto+, 2013)
J/AJ/150/108 : Spectroscopy and HST imaging in ONC (O'Dell+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Epoch [1/11] Epoch number
4- 13 A10 "date" Date Date of the observation
15 I1 h RAh Hour of Right Ascension (J2000) (1)
17- 18 I2 min RAm Minute of Right Ascension (J2000) (1)
20- 24 F5.2 s RAs Second of Right Ascension (J2000) (1)
26 A1 --- DE- Sign of the Declination (J2000)
27 I1 deg DEd Degree of Declination (J2000) (1)
29- 30 I2 arcmin DEm Arcminute of Declination (J2000) (1)
32- 36 F5.2 arcsec DEs Arcsecond of Declination (J2000) (1)
38- 42 A5 --- Inst Instrument
44- 48 A5 --- Filt Filter
50- 54 F5.1 s ExpTime [40/500] Exposure time
56- 60 I5 --- GO-ID [5976/13826] Proposal ID
62- 69 A8 --- PI Principal investigator's name
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Note (1): At the center of the frame.
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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- 3 I3 --- ID [1/715] Internal source identifier
5- 15 F11.8 deg RAdeg Right Ascension in decimal degrees (J2000,
Epoch=J2015.5)
17- 27 F11.8 deg DEdeg Declination in decimal degrees (J2000,
Epoch=J2015.5)
29- 34 F6.2 mas/yr pmRA [-29.21/26.83] Proper motion along RA,
µα*cos(δ)
36- 39 F4.2 mas/yr e_pmRA [0/3.98] Uncertainty in pmRA
41- 46 F6.2 mas/yr pmDE [-33.83/29.69] Proper motion along DE,
µδ
48- 51 F4.2 mas/yr e_pmDE [0/6.81] Uncertainty in pmDE
53 I1 --- Ndet [2/9] Number of detections within the time
baseline
55- 58 F4.1 yr Dt [4.1/20.1] Time baseline Δt
60- 64 F5.2 mag F139 [9.62/20.34]? F139 Vega-mag photometry
66 I1 --- Note [1/6]? Note (1)
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Note (1): Note as follows:
1 = Proplyd morphology;
2 = Herbig-Haro object (Ricci et al. 2008, J/AJ/136/2136);
3 = Double star, previously known in the literature (Hillenbrand 1997,
J/AJ/113/1733; Robberto et al. 2013, J/ApJS/207/10);
4 = New double star, previously reported as single in the literature;
5 = Double-star candidate, previously reported as single in the literature;
6 = Double-star candidate, previously unreported.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 05-Jun-2019