J/ApJ/807/27 IN-SYNC. III. Radial velocities of IC348 stars (Cottaar+, 2015)
IN-SYNC.
III. The dynamical state of IC 348 - a super-virial velocity dispersion and
a puzzling sign of convergence.
Cottaar M., Covey K.R., Foster J.B., Meyer M.R., Tan J.C., Nidever D.L.,
Drew Chojnowski S., da Rio N., Flaherty K.M., Frinchaboy P.M., Majewski S.,
Skrutskie M.F., Wilson J.C., Zasowski G.
<Astrophys. J., 807, 27 (2015)>
=2015ApJ...807...27C 2015ApJ...807...27C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Radial velocities
Keywords: open clusters and associations: individual: IC 348;
stars: pre-main sequence; techniques: radial velocities
Abstract:
Most field stars will have encountered the highest stellar density and
hence the largest number of interactions in their birth environment.
Yet the stellar dynamics during this crucial phase are poorly
understood. Here we analyze the radial velocities measured for 152 out
of 380 observed stars in the 2-6Myr old star cluster IC 348 as part of
the SDSS-III APOGEE. The radial velocity distribution of these stars
is fitted with one or two Gaussians, convolved with the measurement
uncertainties including binary orbital motions. Including a second
Gaussian improves the fit; the high-velocity outliers that are best
fit by this second component may either (1) be contaminants from the
nearby Perseus OB2 association, (2) be a halo of ejected or dispersing
stars from IC 348, or (3) reflect that IC 348 has not relaxed to a
Gaussian velocity distribution. We measure a velocity dispersion for
IC 348 of 0.72±0.07km/s (or 0.64±0.08km/s if two Gaussians are
fitted), which implies a supervirial state, unless the gas contributes
more to the gravitational potential than expected. No evidence is
found for a dependence of this velocity dispersion on distance from
the cluster center or stellar mass. We also find that stars with lower
extinction (in the front of the cloud) tend to be redshifted compared
with stars with somewhat higher extinction (toward the back of the
cloud). This data suggest that the stars in IC 348 are converging
along the line of sight. We show that this correlation between radial
velocity and extinction is unlikely to be spuriously caused by the
small cluster rotation of 0.024±0.013km/s/arcmin or by correlations
between the radial velocities of neighboring stars. This signature, if
confirmed, will be the first detection of line of sight convergence in
a star cluster. Possible scenarios for reconciling this convergence
with IC 348's observed supervirial state include: (a) the cluster is
fluctuating around a new virial equilibrium after a recent disruption
due to gas expulsion or a merger event, or (b) the population we
identify as IC 348 results from the chance alignment of two
sub-clusters converging along the line of sight. Additional
measurements of tangential and radial velocities in IC 348 will be
important for clarifying the dynamics of this region and informing
models of the formation and evolution of star clusters.
Description:
Cottaar et al. (Paper I, 2014, J/ApJ/794/125) describes the analysis
of the high-resolution near-infrared spectra obtained by the APOGEE
multi-object spectrograph from stars in IC 348, NGC 1333, NGC 2264,
and Orion A as part of the INfrared Spectroscopy of Young Nebulous
Clusters (IN-SYNC) ancillary program.
Using radial velocities determined from APOGEE spectra of 380 likely
cluster members, we have measured the radial velocity distribution of
the young (2-6Myr) cluster IC 348.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 18 4771 List of stars; table added by CDS
table1.dat 77 12945 *Radial velocities of 4771 stars in IC 348
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Note on table1.dat: Marginalized over other parameters the MCMC simulation
gives a mean heliocentric velocity of 15.37±0.07km/s for IC 348.
See section 4.1.
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See also:
II/197 : ISM towards IC 348 and Per OB2 (Cernis, 1993)
J/ApJ/799/136 : IN-SYNC. II. Candidate young stars in NGC1333 (Foster+, 2015)
J/ApJ/794/125 : IN-SYNC. I. APOGEE stellar parameters (Cottaar+, 2014)
J/A+A/563/A94 : Kinematics of the Gamma Vel cluster (Jeffries+, 2014)
J/MNRAS/437/906 : Cl* IC 348 H 254 VRI light curves (Ripepi+, 2014)
J/MNRAS/434/806 : Pre-main-sequence isochrones. II. SFR (Bell+, 2013)
J/AJ/145/66 : Spitzer light curves of YSOs in IC 348 (Flaherty+, 2013)
J/A+A/554/A55 : C18O(1-0) and N2H+(1-0) in L1495/B213 (Hacar+, 2013)
J/A+A/539/A64 : X-ray data for IC 348 young stars (Alexander+, 2012)
J/A+A/537/A135 : X-ray view of IC348 (Stelzer+, 2012)
J/ApJ/754/44 : The AstraLux Large M-dwarf Survey (Janson+ 2012)
J/ApJS/190/1 : A survey of stellar families (Raghavan+, 2010)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/AJ/138/703 : Deep MIPS observations of IC 348 nebula (Currie+, 2009)
J/AJ/134/411 : Properties of IC 348 members (Muench+, 2007)
J/AJ/131/1574 : Infrared photometry of IC348 members (Lada+, 2006)
J/ApJ/649/862 : IR phot. of IC 348 pre-main-sequence stars (Cieza+, 2006)
J/ApJ/597/555 : IR photometry of IC 348 young brown dwarfs (Mainzer+, 2003)
J/A+A/409/147 : J magnitude of IC 348 brown dwarfs (Preibisch+, 2003)
J/ApJ/593/1093 : IC 348 membership (Luhman+, 2003)
J/AJ/122/866 : X-ray sources in IC 348 from Chandra (Preibisch+, 2001)
J/ApJ/541/977 : HST observations of low-mass stars in IC 348 (Najita+, 2000)
J/ApJ/525/466 : Young low-mass stars & brown dwarfs in IC 348 (Luhman+, 1999)
J/A+AS/137/305 : IC 348 proper motion catalogue (Scholz+, 1999)
J/A+A/291/943 : Protostellar cores (Ossenkopf+, 1994)
http://www.sdss3.org/ : SDSS-III home page
http://www.astro.ufl.edu/insync/ : IN-SYNC program home page
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [2M]
3- 18 A16 --- 2MASS 2MASS name (HHMMSSss+DDMMSSs; J2000)
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Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [2M]
3- 18 A16 --- 2MASS 2MASS name (HHMMSSss+DDMMSSs; J2000)
20- 28 F9.1 d JD Julian date of the observation
30- 44 F15.9 km/s RV [-2791/2272] Radial velocity
46- 60 F15.9 km/s RVc [-2791/2272]? Corrected Radial velocity (1)
62- 77 F16.10 km/s e_RVc [0.002/76749]? Uncertainty in RVc
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Note (1): Radial velocities corrected for the systematic redshift found for
the coolest stars in Paper I (Cottaar et al. 2014, J/ApJ/794/125).
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History:
From electronic version of the journal
References:
Cottaar et al. Paper I. 2014ApJ...794..125C 2014ApJ...794..125C Cat. J/ApJ/794/125
Foster et al. Paper II. 2015ApJ...799..136F 2015ApJ...799..136F Cat. J/ApJ/799/136
Da Rio et al. Paper IV. 2016ApJ...818...59D 2016ApJ...818...59D Cat. J/ApJ/818/59
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Nov-2015