J/ApJ/676/1109 Velocities of stars in the Orion Nebula Cluster (Furesz+, 2008)
Kinematic structure of the Orion Nebula Cluster and its surroundings.
Furesz G., Hartmann L.W., Megeath S.T., Szentgyorgyi A.H., Hamden E.T.
<Astrophys. J., 676, 1109-1122 (2008)>
=2008ApJ...676.1109F 2008ApJ...676.1109F
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Radial velocities ;
Photometry, H-alpha ; Equivalent widths ; Photometry, infrared
Keywords: ISM: kinematics and dynamics - stars: formation - stars: kinematics -
stars: pre-main sequence
Abstract:
We present results from 1351 high-resolution spectra of 1215 stars
in the Orion Nebula Cluster (ONC) and the surrounding Orion 1c
association, obtained with the Hectochelle multiobject echelle
spectrograph on the 6.5m MMT. We confirmed 1111 stars as members,
based on their radial velocity and/or Hα emission. The radial
velocity distribution of members shows a dispersion of
σ=3.1km/s. We found a substantial north-south velocity gradient
and spatially coherent structure in the radial velocity distribution,
similar to that seen in the molecular gas in the region. We also
identified several binary and high velocity stars, a region exhibiting
signs of triggered star formation, and a possible foreground
population of stars somewhat older than the ONC.
Description:
The spectroscopic observations were carried out using the Hectochelle
multiobject spectrograph at the 6.5m MMT telescope in Arizona.
The first set of spectra was taken in 2004 December, when a total of
866 stars in four fields were observed. Initially we chose not to bin
in the resolution direction, which resulted in low S/N values for the
faintest targets. Therefore, we used a 2x2 binning in 2005 November in
order to decrease the readout noise in the data and thus go fainter.
Accordingly, the accuracy of RVs derived for the 485 stars observed in
2005 are comparable to the 2004 values.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 105 1111 Spectroscopy of member stars
table3.dat 105 104 Spectroscopy of non-members stars
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See also:
J/ApJ/660/704 : Optical and X-ray variability of ONC PMS (Stassun+, 2007)
J/ApJ/660/1462 : Abundances of ONC X-ray PMS stars (Maggio+, 2007)
J/ApJ/671/605 : NGC 2264 and ONC PMS stars in the infrared (Cieza+, 2007)
J/ApJS/183/261 : Optical photometry of the ONC (Da Rio+, 2009)
Table1: Summary of Spectroscopic Observations
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Date ID Field Center Exposures Binning Mode Number of Targets
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2004 Dec 01 F11 5 35 19 -04 49 27 3x20 min 1x1 224
2004 Dec 01 F21 5 35 13 -05 21 14 3x20 min 1x1 210
2004 Dec 01 F22 5 35 13 -05 21 14 3x20 min 1x1 219
2004 Dec 01 F31 5 35 26 -06 07 30 3x20 min 1x1 213
2005 Nov 15 S3 5 35 13 -05 33 10 3x15 min 2x2 161
2005 Nov 15 S2 5 35 11 -05 07 28 3x15 min 2x2 154
2005 Nov 15 S1 5 35 21 -05 18 50 3x15 min 2x2 170
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Byte-by-byte Description of file: table[23].dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- 2MASS 2MASS identification (HHMMSSS+DDMMSS)
16- 24 A9 --- ID This paper's identification (1)
26- 30 F5.2 mag Jmag 2MASS J band magnitude
32- 36 F5.2 mag J-K 2MASS J-K color index
38- 42 F5.2 mag H-K 2MASS H-K color index
44- 48 F5.2 mag 3.6-4.5 ? IRAC (3.6-4.5) micron band color index
50- 54 F5.2 mag 5.8-8.0 ? IRAC (5.8-8.0) micron band color index
56- 62 F7.2 km/s HRV ? Measured heliocentric radial velocity
64- 68 F5.2 km/s e_HRV ? Error estimate in HRV from xcsao
70- 73 F4.1 --- R Cross-correlation signal-to-noise
75- 78 F4.2 --- S Cross-correlation function peak height
80- 84 F5.1 0.1nm EWc ? Hα absolute equivalent width (2)
86- 88 I3 km/s FW10 ? Hα full width at 10% of corrected
maximum
90- 93 A4 --- Ha Hα emission profile note (3)
95-103 A9 --- CCF Cross-correlation function note (4)
105 I1 --- N Number of observations
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Note (1): ID specifies the field (see Table 1) and aperture of observation.
* Hectochelle targets in ONC found to be members based on measured RV
value or by detected Hα emission. The criteria of beeing RV
member is to have at least one velocity measurement within 4σ of
the cluster mean velocity: 13.7km/s<HRV<38.5km/s. RV members listed
only with R>2, while stars with Hα emission are included
regardless of R value, but with no velocity displayed.
* Hectochelle targets in ONC found to be non-members based on measured
RV value or lack of detected Hα emission. Stars are listed
regardless of R value, but no velocity is displayed in case of very
low R or undefined CCF.
Note (2): Measured in Angstroems on the corrected Hα profile (see
text for details).
Note (3): CTTS/WTTS classification, as follows:
C = classical T Tauri stars, CTTS
W = nonaccreting, weak-emission T Tauri star, sWTTS
CW = rather CTTS, but could be WTTS
WC = rather WTTS, but could be CTTS
W+ = assymetry in line profile/wing: likley WTTS
W- = assymetry in wings, but wings at low intensity: could be WTTS
D = resolved or unresolved double gaussian profile, no excess
Hα emission (likley non-TTS)
CD = resolved or unresolved double gaussian profile, likely CTTS
WD = resolved or unresolved double gaussian profile, likely WTTS
R = obviously shifted Hα absorption : high RV stars
X = very wide Hα absorption with nebular emissions
CX = CTTS, with strange emission profiles
AE = stellar absorption and nebular emission together
NS = very strong nebular component component, no wings, no asymmetry
NSC = like NS, but if intensity logscaled wide wings/assymetry is
visible and suggest CTTS emission signature under the strong
nebular component
NSW = like NS, but if intensity logscaled narrow wings/asymmetry is
visible and suggest WTTS emission signature under the strong
nebular component
SAT = saturated, or neighbour saturated
Note (4): Cross-correlation function flag as follows:
w = wide peak, results large errors in RV
l = very low peak, but still sticks out from surrounding
u = almost undefined, very low/wide peak
n = very noisy (several local peaks, almost as high as the one picked)
s = side lobed, could be a spectroscopic binary
d = double peak, spectroscopic binary
dv = RV measured more than once, found different velocities, could be binary
r = template spectra with highest peak in cross-correlation resulted
non-realistic velocity, so the template resulting in highest
R value was used instead to determine velocity
c = clear, well-isolated peak
? = uncertainty in assigning the given note
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History:
* 05-Nov-2010: From electronic version of the journal
* 31-Jan-2011: Label J-H corrected into J-K in tables 2,3.
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 25-Sep-2010