1,271 research outputs found
Praesepe (NGC 2632) and its tidal tails
Within a 400 pc sphere around the Sun, we search for Praesepe's tidal tails
in the Gaia DR2 dataset. We used a modified convergent-point method to search
for stars with space velocities close to the space velocity of the Praesepe
cluster. We find a clear indication for the existence of Praesepe's tidal
tails, both extending up to 165~pc from the centre of the cluster. A total of
1393 stars populate the cluster and its tails, giving a total mass of 794
M_Sun. We determined a tidal radius of 10.77 pc for the cluster and a tidal
mass of 483 M_Sun. The corresponding half-mass radius is 4.8 pc. We also found
clear indication for mass segregation in the cluster. The tidal tails outside 2
tidal radii are populated by 389 stars. The total contamination of our sample
by field stars lies between 50 to 100 stars or 3.6 to 7.2 per cent. We used an
astrometrically and photometrically clean sub-sample of Gaia DR2 which makes
our Praesepe sample incomplete beyond M_G ~ 12.0 mag, which corresponds to
about 0.25 M_Sun. A comparison with an N-body model of the cluster and its
tails shows remarkably good coincidence. Three new white dwarfs are found in
the tails.Comment: 6 pages, 5 figures. Accepted by Astronomy and Astrophysic
Investigating alterations of social interaction in psychiatric disorders with dual interactive eye tracking and virtual faces
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).Peer reviewedPublisher PD
"Making it explicit" makes a difference: Evidence for a dissociation of spontaneous and intentional level 1 perspective taking in high-functioning autism
This research was supported by Volkswagen Foundation grant âBeing addressed as you: Conceptual and empirical investigations of a Second-Person approach to other mindsâ awarded to LS and BT. LS is also supported by the Koeln Fortune Program of the Medical Faculty, University of Cologne. BT was supported by a European Commission Marie Curie Fellowship FP7-PEOPLE-IEF 237502 âSocial Brain.â We thank Dana Samson for providing the stimulus material and Julia Proft and Franka Pieplow for data collection. For helpful comments and suggestions we are also grateful to three anonymous reviewers.Peer reviewedPreprin
Hot Stuff for One Year (HSOY) - A 583 million star proper motion catalogue derived from Gaia DR1 and PPMXL
Recently, the first installment of data from ESA's Gaia astrometric satellite
mission (Gaia-DR1) was released, containing positions of more than 1 billion
stars with unprecedented precision, as well as only proper motions and
parallaxes, however only for a subset of 2 million objects. The second release,
due in late 2017 or early 2018, will include those quantities for most objects.
In order to provide a dataset that bridges the time gap between the Gaia-DR1
and Gaia-DR2 releases and partly remedies the lack of proper motions in the
former, HSOY ("Hot Stuff for One Year") was created as a hybrid catalogue
between Gaia-DR1 and ground-based astrometry, featuring proper motions (but no
parallaxes) for a large fraction of the DR1 objects. While not attempting to
compete with future Gaia releases in terms of data quality or number of
objects, the aim of HSOY is to provide improved proper motions partly based on
Gaia data, allowing some studies to be carried out just now or as pilot studies
for later larger projects requiring higher-precision data. The HSOY catalogue
was compiled using the positions taken from Gaia-DR1 combined with the input
data from the PPMXL catalogue, employing the same weighted least-squares
technique that was used to assemble the PPMXL catalogue itself. Results. This
effort resulted in a four-parameter astrometric catalogue containing
583,000,000 objects, with Gaia-DR1 quality positions and proper motions with
precisions from significantly less than 1 mas/yr to 5 mas/yr, depending on the
object's brightness and location on the sky.Comment: 4 pages, 5 figures, accepted for publication in A&A letter
A census of the near-by Pisces-Eridanus stellar stream -- Commonalities with and disparities from the Pleiades
Within a 400~pc sphere around the Sun, we search for members of the
Pisces-Eridanus (Psc-Eri) stellar stream in the Gaia Data Release 2 (DR2) data
set. We compare basic astrophysical characteristics of the stream with those of
the Pleiades. We used a modified convergent-point method to identify stars with
2D - velocities consistent with the space velocity of the Psc-Eri stream and
the Pleiades, respectively. We found 1387 members of the Psc-Eri stream in a G
magnitude range from 5.1 mag to 19.3 mag at distances between 80 and 380 pc
from the Sun. The stream has a nearly cylindrical shape with length and
thickness of about 700 pc and 100 pc, respectively. The total stellar mass
contained in the stream is about 770 M_Sun, and the members are gravitationally
unbound. For the stream we found an age of about 135 Myr. In many astrophysical
properties Psc-Eri is comparable to the open cluster M45 (the Pleiades): in its
age, its luminosity function (LF), its Present-day mass Function (PDMF) as well
as in its total mass. Nonetheless, the two stellar ensembles are completely
unlike in their physical appearance. We cautiously give two possible
explanations for this disagreement: (i) the star-formation efficiency in their
parental molecular clouds was higher for the Pleiades than for Psc-Eri or/and
(ii) the Pleiades had a higher primordial mass segregation immediately after
the expulsion of the molecular gas of the parental cloud.Comment: 10 pages, 6 figure
Global survey of star clusters in the Milky Way IV. 63 new open clusters detected by proper motions
AIMS: In their 1st extension to the Milky Way Star Clusters (MWSC) survey,
Schmeja et al. applied photometric filters to the 2MASS to find new cluster
candidates that were subsequently confirmed or rejected by the MWSC pipeline.
To further extend the MWSC census, we aimed at discovering new clusters by
conducting an almost global search in proper motion catalogues as a starting
point. METHODS: We first selected high-quality samples from the PPMXL and UCAC4
for comparison and verification of the proper motions. For 441 circular proper
motion bins (radius 15 mas/yr) within 50 mas/yr, the sky outside a thin
Galactic plane zone (5) was binned in small areas ('sky
pixels') of 0.250.25 deg. Sky pixels with enhanced numbers of stars
with a certain common proper motion in both catalogues were considered as
cluster candidates. After visual inspection of the sky images, we built an
automated procedure that combined these representations of the sky for
neighbouring proper motion subsamples after a background correction. RESULTS:
About half of our 692 candidates overlapped with known clusters (46 globular
and 68 open clusters in the Galaxy, about 150 known clusters of galaxies) or
the Magellanic Clouds. About 10% of our candidates turned out to be 63 new open
clusters confirmed by the MWSC pipeline. They occupy predominantly the two
inner Galactic quadrants and have apparent sizes and numbers of high-probable
members slightly larger than those of the typically small MWSC clusters,
whereas their other parameters (ages, distances, tidal radii) fall in the
typical ranges. As our search aimed at finding compact clusters, we did not
find new very nearby (extended) clusters. (abridged)Comment: 14 pages, 14 figures, accepted for publication in Astronomy and
Astrophysic
Global survey of star clusters in the Milky Way II. The catalogue of basic parameters
Although they are the main constituents of the Galactic disk population, for
half of the open clusters in the Milky Way reported in the literature nothing
is known except the raw position and an approximate size. The main goal of this
study is to determine a full set of uniform spatial, structural, kinematic, and
astrophysical parameters for as many known open clusters as possible. On the
basis of stellar data from PPMXL and 2MASS, we used a dedicated data-processing
pipeline to determine kinematic and photometric membership probabilities for
stars in a cluster region. For an input list of 3784 targets from the
literature, we confirm that 3006 are real objects, the vast majority of them
are open clusters, but associations and globular clusters are also present. For
each confirmed object we determined the exact position of the cluster centre,
the apparent size, proper motion, distance, colour excess, and age. For about
1500 clusters, these basic astrophysical parameters have been determined for
the first time. For the bulk of the clusters we also derived the tidal radius.
We estimated additionally average radial velocities for more than 30% of the
confirmed clusters. The present sample (called MWSC) reaches both the central
parts of the Milky Way and its outer regions. It is almost complete up to 1.8
kpc from the Sun and also covers neighbouring spiral arms. However, for a small
subset of the oldest open clusters () we found some evidence
of incompleteness within about 1 kpc from the Sun.Comment: 8 pages, 5 figures, accepted for publication in Astronomy and
Astrophysic
Eyes on the mind : investigating the influence of gaze dynamics on the perception of others in real-time social interaction
ACKNOWLEDGMENTS This study was partially supported by a grant of the Köln Fortune Program of the Medical Faculty at the University of Cologne to Leonhard Schilbach and by a grant âOther Mindsâ of the German Ministry of Research and Education to Kai Vogeley. The authors would like to thank Stephanie Alexius and Leonhard Engels for their assistance in data collection.Peer reviewedPublisher PD
Spectroscopic and photometric studies of white dwarfs in the Hyades
The Hyades cluster is known to harbour ten so-called classical white dwarf
members. Numerous studies through the years have predicted that more than twice
this amount of degenerate stars should be associated with the cluster. Using
the PPMXL catalog of proper motions and positions, a recent study proposed 17
new white dwarf candidates. We review the membership of these candidates by
using published spectroscopic and photometric observations, as well as by
simulating the contamination from field white dwarfs. In addition to the ten
classical Hyades white dwarfs, we find six white dwarfs that may be of Hyades
origin and three more objects that have an uncertain membership status due to
their unknown or imprecise atmospheric parameters. Among those, two to three
are expected as field stars contamination. Accurate radial velocity
measurements will confirm or reject the candidates. One consequence is that the
longstanding problem that no white dwarf older than ~340 Myr appears to be
associated with the cluster remains unsolved.Comment: 14 pages, 9 figures, accepted for publication in the Astronomy and
Astrophysics journa
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