1,209 research outputs found
UPMASK: unsupervised photometric membership assignment in stellar clusters
We develop a method for membership assignment in stellar clusters using only
photometry and positions. The method, UPMASK, is aimed to be unsupervised, data
driven, model free, and to rely on as few assumptions as possible. It is based
on an iterative process, principal component analysis, clustering algorithm,
and kernel density estimations. Moreover, it is able to take into account
arbitrary error models. An implementation in R was tested on simulated clusters
that covered a broad range of ages, masses, distances, reddenings, and also on
real data of cluster fields. Running UPMASK on simulations showed that it
effectively separates cluster and field populations. The overall spatial
structure and distribution of cluster member stars in the colour-magnitude
diagram were recovered under a broad variety of conditions. For a set of 360
simulations, the resulting true positive rates (a measurement of purity) and
member recovery rates (a measurement of completeness) at the 90% membership
probability level reached high values for a range of open cluster ages
( yr), initial masses (M_{\sun}) and
heliocentric distances ( kpc). UPMASK was also tested on real data
from the fields of the open cluster Haffner~16 and of the closely projected
clusters Haffner~10 and Czernik~29. These tests showed that even for moderate
variable extinction and cluster superposition, the method yielded useful
cluster membership probabilities and provided some insight into their stellar
contents. The UPMASK implementation will be available at the CRAN archive.Comment: 12 pages, 13 figures, accepted for publication in Astronomy and
Astrophysic
NGC 2401: A template of the Norma-Cygnus Arm's young population in the Third Galactic Quadrant
Based on a deep optical CCD (UBV(RI)_C) photometric survey and on the
Two-Micron All-Sky-Survey (2MASS) data we derived the main parameters of the
open cluster NGC 2401. We found this cluster is placed at 6.3 0.5 kpc
(V_O - M_V = 14.0 \pm 0.2) from the Sun and is 25 Myr old, what allows us to
identify NGC 2401 as a member of the young population belonging to the
innermost side of the extension of the Norma-Cygnus spiral--arm in the Third
Galactic Quadrant. A spectroscopic study of the emission star LSS 440 that lies
in the cluster area revealed it is a B0Ve star; however, we could not confirm
it is a cluster member. We also constructed the cluster luminosity function
(LF) down to and the cluster initial mass function (IMF) for all
stars with masses above M \sim 1-2 M_{\sun}. It was found that the slope of
the cluster IMF is . The presence of a probable PMS star
population associated to the cluster is weakly revealed.Comment: 10 paginas, 11 eps figures, accepted for publication in MNRA
Evidence of tidal distortions and mass loss from the old open cluster NGC 6791
We present the first evidence of clear signatures of tidal distortions in the
density distribution of the fascinating open cluster NGC 6791. We used deep and
wide-field data obtained with the Canada-France-Hawaii-Telescope covering a 2x2
square degrees area around the cluster. The two-dimensional density map
obtained with the optimal matched filter technique shows a clear elongation and
an irregular distribution starting from ~300" from the cluster center. At
larger distances, two tails extending in opposite directions beyond the tidal
radius are also visible. These features are aligned to both the absolute proper
motion and to the Galactic center directions. Moreover, other overdensities
appear to be stretched in a direction perpendicular to the Galactic plane.
Accordingly to the behaviour observed in the density map, we find that both the
surface brightness and the star count density profiles reveal a departure from
a King model starting from ~600" from the center. These observational evidence
suggest that NGC 6791 is currently experiencing mass loss likely due to
gravitational shocking and interactions with the tidal field. We use this
evidence to argue that NGC 6791 should have lost a significant fraction of its
original mass. A larger initial mass would in fact explain why the cluster
survived so long. Using available recipes based on analytic studies and N-body
simulations, we derived the expected mass loss due to stellar evolution and
tidal interactions and estimated the initial cluster mass to be M_ini=(1.5-4) x
10^5 M_sun.Comment: Accepted for publication in the MNRAS (9 pages, 8 Figures
The edge of the young Galactic disc
In this work we report and discuss the detection of two distant diffuse
stellar groups in the third Galactic quadrant. They are composed of young
stars, with spectral types ranging from late O to late B, and lie at
galactocentric distances between 15 and 20 kpc. These groups are located in the
area of two cataloged open clusters (VdB-Hagen~04 and Ruprecht~30), projected
towards the Vela-Puppis constellations, and within the core of the Canis Major
over-density. Their reddening and distance has been estimated analyzing their
color-color and color-magnitude diagrams, derived from deep photometry.
The existence of young star aggregates at such extreme distances from the
Galactic center challenges the commonly accepted scenario in which the Galactic
disc has a sharp cut-off at about 14 kpc from the Galactic center, and
indicates that it extends to much greater distances (as also supported by
recent detection of CO molecular complexes well beyond this distance). While
the groups we find in the area of Ruprecht~30 are compatible with the Orion and
Norma-Cygnus spiral arms, respectively, the distant group we identify in the
region of VdB-Hagen~4 lies in the external regions of the Norma-Cygnus arm, at
a galactocentric distance (20 kpc) where no young stars had been detected
so far in the optical.Comment: 45 pages, 11 eps figure, accepted for publication in the
Astrophysical Journa
Photometry of a Galactic field at l = 232, b = -6. The old open cluster Auner 1, the Norma-Cygnus spiral arm and the signature of the warped Galactic Thick Disk
We perform a detailed photometric study of the stellar populations in a
Galactic Field at l = 232, b = -6 in the Canis Major (CMa) constellation. We
present the first U,B,V,I photometry of the old open cluster Auner1 and
determine it to be 3.25 Gyr old and to lie at 8.9 kpc from the Sun. In the
background of the cluster, at more than 9 kpc, we detect a young population
most probably associated to the Norma Cygnus spiral arm. Furthermore, we detect
the signature of an older population and identify its Turn Off and Red Giant
Branch. This population is found to have a mean age of 7 Gyrs and a mean
metallicity of Z = 0.006 . We reconstruct the geometry of the stellar
distribution and argue that this older population - often associated to the
Canis Major {\it galaxy}- belongs in fact to the warped old thin/thick disk
component along this line of sight.Comment: 19 pages, 7 eps figures (some degraded), accepted for publication in
the Astronomical Journa
Marital Satisfaction and Attachment Style: The Mediating Role of Emotional Intelligence and Religious Commitment
Most couples enter marriage hoping to experience happiness and satisfaction. This study acknowledges that spouses bring their worldviews, personalities, behaviors, and emotions to the marriage relationship, and for this reason, this study investigates the connection between marital satisfaction and attachment style as mediated by emotional intelligence and religious commitment in a sample of heterosexual married Christian individuals living in the United States. This quantitative, non-experimental, survey-based research analyzes data collected through Amazon Mechanical Turk from 530 married individuals to understand the relationship between variables affecting marital satisfaction. Results from Pearson’s correlation analyses show a significant relationship between attachment style subscales (avoidance and anxiety) and marital satisfaction (p \u3c .05). Additionally, a comprehensive mediation analysis shows that the attachment style subscales of avoidance and anxiety in the mother and father relationship have an indirect effect on marital satisfaction through both emotional intelligence and religious commitment. Thus, future studies need to consider marriage relationship dynamics, spouses’ management of emotions, and the protective role of religion in the marriage relationship
Open clusters in the Third Galactic Quadrant. II. The intermediate age open clusters NGC 2425 and NGC 2635
We analyse CCD broad band (UBV(RI)c) photometric data obtained in the fields
of the poorly studied open clusters NGC 2425 and NGC 2635. Both clusters are
found to be of intermediate age thus increasing the population of open clusters
known to be of the age of, or older than, the Hyades. More explicitly, we find
that NGC 2425 is a 2.2 Gyr old cluster, probably of solar metallicity, located
at 3.5 kpc from the Sun. NGC 2635 is a Hyades age (600 Myr) cluster located at
a distance of 4.0 kpc from the Sun. Its Colour Magnitude Diagram reveals that
it is extremely metal poor for its age and position, thus making it a very
interesting object in the context of Galactic Disk chemical evolution models.Comment: 10 pages, 13 figures. Figure quality has been quiet degraded.
Accepted by A&
Blue Straggler Stars in Galactic Open Clusters and the effect of field star contamination
We investigate the distribution of Blue Straggler stars in the field of three
open star clusters. The main purpose is to highlight the crucial role played by
general Galactic disk fore-/back-ground field stars, which are often located in
the same region of the Color Magnitude Diagram as Blue Straggler stars. We
analyze photometry taken from the literature of 3 open clusters of
intermediate/old age rich in Blue Straggler stars, and which are projected in
the direction of the Perseus arm, and study their spatial distribution and the
Color Magnitude Diagram. As expected, we find that a large portion of the Blue
Straggler population in these clusters are simply young field stars belonging
to the spiral arm. This result has important consequences on the theories of
the formation and statistics of Blue Straggler stars in different population
environments: open clusters, globular clusters or dwarf galaxies. As previously
emphasized by many authors, a detailed membership analysis is mandatory before
comparing the Blue Straggler population in star clusters against theoretical
models. Moreover, these sequences of young field stars (blue plumes) are
potentially powerful tracers of Galactic structure which require further
consideration.Comment: 11 pages, 4 figurs, in press as Research Note in A&
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