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29 March 2024 |
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Article overview
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IN-SYNC III: The dynamical state of IC 348 - A super-virial velocity dispersion and a puzzling sign of convergence | Michiel Cottaar
; Kevin R. Covey
; Jonathan B. Foster
; Michael R. Meyer
; Jonathan C. Tan
; David L. Nidever
; S. Drew Chojnowski
; Nicola da Rio
; Kevin M. Flaherty
; Peter M. Frinchaboy
; Steve Majewski
; Michael F. Skrutskie
; John C. Wilson
; Gail Zasowski
; | Date: |
28 May 2015 | 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 2-6 Myr 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 $0.72 pm 0.07$ km s$^{-1}$ (or
$0.64 pm 0.08$ km s$^{-1}$ 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 (towards the
back of the cloud). This data suggests 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 $0.024 pm 0.013$ km s$^{-1}$ arcmin$^{-1}$ 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(...) | Source: | arXiv, 1505.7504 | Services: | Forum | Review | PDF | Favorites |
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