70 research outputs found
Protoplanetary disk lifetimes vs stellar mass and possible implications for giant planet populations
We study the dependence of protoplanetary disk evolution on stellar mass
using a large sample of young stellar objects in nearby young star-forming
regions. We update the protoplanetary disk fractions presented in our recent
work (paper I of this series) derived for 22 nearby (< 500 pc) associations
between 1 and 100 Myr. We use a subsample of 1 428 spectroscopically confirmed
members to study the impact of stellar mass on protoplanetary disk evolution.
We divide this sample into two stellar mass bins (2 M boundary) and
two age bins (3 Myr boundary), and use infrared excesses over the photospheric
emission to classify objects in three groups: protoplanetary disks, evolved
disks, and diskless. The homogeneous analysis and bias corrections allow for a
statistically significant inter-comparison of the obtained results. We find
robust statistical evidence of disk evolution dependence with stellar mass. Our
results, combined with previous studies on disk evolution, confirm that
protoplanetary disks evolve faster and/or earlier around high-mass (> 2
M) stars. We also find a roughly constant level of evolved disks
throughout the whole age and stellar mass spectra. We conclude that
protoplanetary disk evolution depends on stellar mass. Such a dependence could
have important implications for gas giant planet formation and migration, and
could contribute to explaining the apparent paucity of hot Jupiters around
high-mass stars.Comment: Accepted for publication in A&A. 13 pages, 8 figures, 5 table
New member candidates of Upper Scorpius from Gaia DR1
Context. Selecting a cluster in proper motion space is an established method
for identifying members of a star forming region. The first data release from
Gaia (DR1) provides an extremely large and precise stellar catalogue, which
when combined with the Tycho-2 catalogue gives the 2.5 million parallaxes and
proper motions contained within the Tycho-Gaia Astrometric Solution (TGAS).
Aims. We aim to identify new member candidates of the nearby Upper Scorpius
subgroup of the Scorpius-Centaurus Complex within the TGAS catalogue. In doing
so, we also aim to validate the use of the DBSCAN clustering algorithm on
spatial and kinematic data as a robust member selection method. Methods. We
constructed a method for member selection using a density-based clustering
algorithm (DBSCAN) applied over proper motion and distance. We then applied
this method to Upper Scorpius, and evaluated the results and performance of the
method. Results. We identified 167 member candidates of Upper Scorpius, of
which 78 are new, distributed within a 10 radius from its core. These
member candidates have a mean distance of 145.6 7.5 pc, and a mean proper
motion of (-11.4, -23.5) (0.7, 0.4) mas/yr. These values are consistent
with measured distances and proper motions of previously identified bona-fide
members of the Upper Scorpius association.Comment: 8 pages, 9 figures and 1 table. Accepted for publication in Astronomy
and Astrophysic
Herschel/PACS photometry of transiting-planet host stars with candidate warm debris disks
Dust in debris disks is produced by colliding or evaporating planetesimals,
remnants of the planet formation process. Warm dust disks, known by their
emission at < 24 micron, are rare (4% of FGK main sequence stars) and
especially interesting because they trace material in the region likely to host
terrestrial planets, where the dust has a very short dynamical lifetime.
Statistical analyses of the source counts of excesses as found with the mid-IR
Wide Field Infrared Survey Explorer (WISE) suggest that warm-dust candidates
found for the Kepler transiting-planet host-star candidates can be explained by
extragalactic or galactic background emission aligned by chance with the target
stars. These statistical analyses do not exclude the possibility that a given
WISE excess could be due to a transient dust population associated with the
target. Here we report Herschel/PACS 100 and 160 micron follow-up observations
of a sample of Kepler and non-Kepler transiting-planet candidates' host stars,
with candidate WISE warm debris disks, aimed at detecting a possible cold
debris disk in any of them. No clear detections were found in any one of the
objects at either wavelength. Our upper limits confirm that most objects in the
sample do not have a massive debris disk like that in beta Pic. We also show
that the planet-hosting star WASP-33 does not have a debris disk comparable to
the one around eta Crv. Although the data cannot be used to rule out rare warm
disks around the Kepler planet-hosting candidates, the lack of detections and
the characteristics of neighboring emission found at far-IR wavelengths support
an earlier result suggesting that most of the WISE-selected IR excesses around
Kepler candidate host stars are likely due to either chance alignment with
background IR-bright galaxies and/or to interstellar emission.Comment: 8 pages, 3 figures, accepted for publication at Astronomy &
Astrophysics on 4 August 201
Infrared study of transitional disks in Ophiuchus with Herschel
Context. Observations of nearby star-forming regions with the Herschel Space
Observatory complement our view of the protoplanetary disks in Ophiuchus with
information about the outer disks. Aims. The main goal of this project is to
provide new far-infrared fluxes for the known disks in the core region of
Ophiuchus and to identify potential transitional disks using data from
Herschel. Methods. We obtained PACS and SPIRE photometry of previously
spectroscopically confirmed young stellar objects (YSO) in the region and
analysed their spectral energy distributions. Results. From an initial sample
of 261 objects with spectral types in Ophiuchus, we detect 49 disks in at least
one Herschel band. We provide new far-infrared fluxes for these objects. One of
them is clearly a new transitional disk candidate. Conclusions. The data from
Herschel Space Observatory provides fluxes that complement previous infrared
data and that we use to identify a new transitional disk candidate.Comment: 21 pages, with 5 figures. Accepted in Astronomy & Astrophysic
Hubble Asteroid Hunter: II. Identifying strong gravitational lenses in HST images with crowdsourcing
The Hubble Space Telescope (HST) archives constitute a rich dataset of high
resolution images to mine for strong gravitational lenses. While many HST
programs specifically target strong lenses, they can also be present by
coincidence in other HST observations. We aim to identify non-targeted strong
gravitational lenses in almost two decades of images from the ESA it Hubble
Space Telescope archive (eHST), without any prior selection on the lens
properties. We used crowdsourcing on the Hubble Asteroid Hunter (HAH) citizen
science project to identify strong lenses, alongside asteroid trails, in
publicly available large field-of-view HST images. We visually inspected 2354
objects tagged by citizen scientists as strong lenses to clean the sample and
identify the genuine lenses. We report the detection of 252 strong
gravitational lens candidates, which were not the primary targets of the HST
observations. 198 of them are new, not previously reported by other studies,
consisting of 45 A grades, 74 B grades and 79 C grades. The majority are
galaxy-galaxy configurations. The newly detected lenses are, on average, 1.3
magnitudes fainter than previous HST searches. This sample of strong lenses
with high resolution HST imaging is ideal to follow-up with spectroscopy, for
lens modelling and scientific analyses. This paper presents an unbiased search
of lenses, which enabled us to find a high variety of lens configurations,
including exotic lenses. We demonstrate the power of crowdsourcing in visually
identifying strong lenses and the benefits of exploring large archival
datasets. This study shows the potential of using crowdsourcing in combination
with artificial intelligence for the detection and validation of strong lenses
in future large-scale surveys such as ESA's future mission Euclid or in JWST
archival images.Comment: 24 page, 14 figures, 5 tables, accepted for publication in A&A June
28 202
ESASky v.2.0: all the skies in your browser
With the goal of simplifying the access to science data to scientists and
citizens, ESA recently released ESASky (http://sky.esa.int), a new open-science
easy-to-use portal with the science-ready Astronomy data from ESA and other
major data providers. In this presentation, we announced version 2.0 of the
application, which includes access to all science-ready images, catalogues and
spectra, a feature to help planning of future JWST observations, the
possibility to search for data of all (targeted and serendipitously observed)
Solar System Objects in Astronomy images, a first support to mobile devices and
several other smaller usability features. We also discussed the future
evolution of the portal and the lessons learnt from the 1+ year of operations
from the point of view of access, visualization and manipulation of big
datasets (all sky maps, also called HiPS) and large catalogues (like e.g. the
Gaia DR1 catalogues or the Hubble Source Catalogue) and the design and
validation principles for the development of friendly GUIs for thin layer web
clients aimed at scientists.Comment: 4 pages, 2 figures, ADASS 2017 conference proceeding
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