J/AJ/149/119 Radial velocities of stars in NGC 2264 (Tobin+, 2015)
Kinematic and spatial substructure in NGC 2264.
Tobin J.J., Hartmann L., Furesz G., Hsu W.-H., Mateo M.
<Astron. J., 149, 119 (2015)>
=2015AJ....149..119T 2015AJ....149..119T
ADC_Keywords: Clusters, open ; Radial velocities ; Spectral types ;
Photometry, infrared
Keywords: ISM: individual: NGC 2264 - ISM: kinematics and dynamics -
stars: formation - stars: pre-main sequence -
techniques: radial velocities - techniques: spectroscopic
Abstract:
We present an expanded kinematic study of the young cluster NGC 2264
based upon optical radial velocities measured using multi-fiber
echelle spectroscopy at the 6.5m MMT and Magellan telescopes. We
report radial velocities for 695 stars, of which approximately 407
stars are confirmed or very likely members. Our results more than
double the number of members with radial velocities from Furesz et
al., resulting in a much better defined kinematic relationship between
the stellar population and the associated molecular gas. In
particular, we find that there is a significant subset of stars that
are systematically blueshifted with respect to the molecular (13CO)
gas. The detection of Lithium absorption and/or infrared excesses in
this blueshifted population suggests that at least some of these stars
are cluster members; we suggest some speculative scenarios to explain
their kinematics. Our results also more clearly define the redshifted
population of stars in the northern end of the cluster; we suggest
that the stellar and gas kinematics of this region are the result of a
bubble driven by the wind from O7 star S Mon. Our results emphasize
the complexity of the spatial and kinematic structure of NGC 2264,
important for eventually building up a comprehensive picture of
cluster formation.
Description:
We report radial velocities for 695 stars (see Table 3), of which
approximately 407 stars are confirmed or very likely members.
We have observed NGC2264 with the multi-fiber echelle spectrograph
Hectochelle on the MMT during several epochs over the past six years.
Hectochelle uses robots to position 240 fibers on a 1° field of
view (FOV). The fibers subtend 1.4'' on the sky yielding a spectral
resolution of R∼35000. There are limitations of fiber spacing in a
given configuration; no targets may be closer than 30''. We used an
order-separating filter (RV 31) to cover the wavelength range of
∼5150-5300Å. Furesz et al. 2006 (cat. J/ApJ/648/1090) observed NGC
2264 in 2004 March and 2005 December; our new observations were
conducted in the fall of 2007 (Oct 12, Oct 26, Oct 28-29, Nov 25),
2008 (Oct 22--26), spring 2009 (Mar 13-14, Apr 10, Apr 13), fall 2009
(Oct 25-26, Oct 31, Nov 02, Nov 27), and spring 2010 (Jan 31, Feb 02,
Feb 06, Mar 03, Mar 05-06, Mar 31, Apr 03).
We also used MIKE Fibers on the 6.5m Magellan Clay telescope (located
at Las Campanas Observatory, Chile) to observe NGC2264 in the spectral
range ∼5150-5210Å on Dec 10-11 2009 and Dec 14-15 2009. This
instrument uses 256 manually plugged fibers that fit within a
pre-drilled plate on a 25' FOV. Each fiber subtends 1.25'' on the sky,
resulting in a resolution R∼18000 and fibers must be spaced at least
14'' apart. MIKE Fibers has two independent spectrograph channels; at
5200Å we are able to use both channels with 128 fibers going to
each channel.
Low-resolution spectra for the purpose of determining membership from
LiI 6707Å absorption were obtained with Inamori-Magellan Areal
Camera & Spectrograph (IMACS) on the Magellan Baade telescope, during
December 20--22 2010 (UT). We used the IMACS f/2 camera in multi-slit
spectroscopy mode with the 300 line grism at a blaze angle of
17.5°. With a 0.6'' slit, this configuration yields a resolution
of 4Å and spectral coverage from approximately 4000-9000Å.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 80 695 Velocity summary
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/AJ/138/1116 : A Spitzer view of NGC 2264 (Sung+, 2009)
J/AJ/138/963 : Rotation of NGC 2264 members (Baxter+, 2009)
J/AJ/135/441 : VRIHa photometry in NGC 2264 (Sung+, 2008)
J/ApJ/676/1109 : Velocities of stars in Orion Nebula Cluster (Furesz+, 2008)
J/ApJ/648/1090 : Radial velocities of NGC 2264 stars (Furesz+, 2006)
J/AJ/127/2659 : CHANDRA observations of NGC 2264 (Ramirez+, 2004)
J/AJ/123/1528 : UBV(RI)c and JHK photometry in NGC 2264 (Rebull+, 2002)
J/AJ/114/2644 : UBVRIHa photometry of NGC2264 (Sung+, 1997)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- 2MASS Internal source name (HHMMSSs+DDMMSS, J2000)
16- 17 I2 h RAh Hour of Right Ascension (J2000)
19- 20 I2 min RAm Minute of Right Ascension (J2000)
22- 26 F5.2 s RAs Second of Right Ascension (J2000)
28- 29 I2 deg DEd Degree of Declination (J2000)
31- 32 I2 arcmin DEm Arcminute of Declination (J2000)
34- 37 F4.1 arcsec DEs Arcsecond of Declination (J2000)
39- 45 F7.2 km/s [-108/235] Mean Heliocentric Radial Velocity (1)
47- 50 F4.2 km/s e_ Uncertainty in HRV
52- 53 I2 --- Nobs [2/14] Number of observations (epochs) (2)
55- 60 F6.2 0.1nm EW ?=-99.00 Lithium 6707Å Equivalent Width
62- 66 F5.1 --- SpT [61/77.2]?=-99.00 Numerical spectral type (3)
68- 73 F6.2 mag K-3.6 [-23/22]?=-99.00 The Ks-[3.6] color index (4)
75- 80 F6.2 mag 3.6-4.5 [-22/22]?=-99.00 The [3.6]-[4.5] color index (4)
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Note (1): Average radial velocity for all observations with cross-correlation
signal-to-noise R>6 including values from Furesz et al. 2006
(J/ApJ/648/1090). R is defined as: R=h/21/2σa, Equation (1),
where h is the peak height of the correlation function and σa is
the rms noise estimated from the antisymmetric portion of the correlation
function.
Note (2): Number of observations with cross-correlation signal-to-noise R>6.
Note (3): The spectral types are numbered with the codes:
20=B0; 30=A0; 40=F0; 50=G0;
60=K0; 61=K1; 62=K2; 63=K3; 64=K4; 65=K5; 66=K6; 67=K7;
68=M0; 69=M1; 70=M2; 71=M3; 72=M4; 73=M5; 74=M6.
Note (4): Infrared Colors derived from 2MASS Catalog (cat. II/246; KS) and
Sung et al. 2009 (cat. J/AJ/138/1116; [3.6] and [4.5]).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 21-Apr-2015