180 research outputs found
Habitat fragmentation and anthropogenic factors affect wildcat Felis silvestris silvestris occupancy and detectability on Mt Etna
Knowledge of patterns of occupancy is crucial for planning sound biological management and for identifying areas which require paramount conservation attention. The European wildcat Felis silvestris is an elusive carnivore and is classified as âleast concernâ on the IUCN red list, but with a decreasing population trend in some areas. Sicily hosts a peculiar wildcat population, which deserves conservation and management actions, due to its isolation from the mainland. Patterns of occupancy for wildcats are unknown in Italy, and especially in Sicily. We aimed to identify which ecological drivers determined wildcat occurrence on Mt Etna and to provide conservation actions to promote the wildcatsâ long-term survival in this peculiar environment. The genetic identity of the wildcat population was confirmed through a scat-collection which detected 22 different wildcat individuals. We analysed wildcat detections collected by 91 cameras using an occupancy frame work to assess which covariates influenced the detection (p) and the occupancy (Ï) estimates. We recorded 70 detections of the target species from 38 cameras within 3377 trap-days. Wildcat detection was positively influenced by the distance to the major paved roads and negatively affected by the presence of humans. Wildcat occupancy was positively associated with mixed forest and negatively influenced by pine forest, fragmentation of mixed forest and altitude. A spatially explicit predicted occupancy map, validated using an independent dataset of wildcat presence records, showed that higher occupancy estimates were scattered, mainly located on the north face and at lower altitude. Habitat fragmentation has been claimed as a significant threat for the wildcat and this is the first study that has ascertained this as a limiting factor for wildcat occurrence. Conservation actions should promote interconnectivity between areas with high predicted wildcat occupancy while minimising the loss of habitat
A New Approach to the Study of Stellar Populations in Early-Type Galaxies: K-band Spectral Indices and an Application to the Fornax Cluster
New measurements of K-band spectral features are presented for eleven
early-type galaxies in the nearby Fornax galaxy cluster. Based on these
measurements, the following conclusions have been reached: (1) in galaxies with
no signatures of a young stellar component, the K-band Na I index is highly
correlated with both the optical metallicity indicator [MgFe]' and central
velocity dispersion; (2) in the same galaxies, the K-band Fe features saturate
in galaxies with sigma > 150 km/s while Na I (and [MgFe]') continues to
increase; (3) [Si/Fe] (and possibly [Na/Fe]) is larger in all observed Fornax
galaxies than in Galactic open clusters with near-solar metallicity; (4) in
various near-IR diagnostic diagrams, galaxies with signatures of a young
stellar component (strong Hbeta, weak [MgFe]') are clearly separated from
galaxies with purely old stellar populations; furthermore, this separation is
consistent with the presence of an increased number of M-giant stars (most
likely to be thermally pulsating AGB stars); (5) the near-IR diagrams discussed
here seem as efficient for detecting putatively young stellar components in
early-type galaxies as the more commonly used age/metallicity diagnostic plots
using optical indices (e.g Hbeta vs. [MgFe]').Comment: 47 pages, 16 figures, ApJ accepte
Implantation temps réel d'un algorithme de segmentation par modélisation de l'architecture du systÚme visuel biologique
La segmentation d'images en temps rĂ©el pose encore Ă l'heure actuelle des problĂšmes d'implantations et de performances. Les mĂ©thodes utilisant une modĂ©lisation du systĂšme visuel biologique prĂ©sentent de bonnes performances mais restent pĂ©nalisantes en termes de calculs sur machines sĂ©quentielles. Dans cet article, on propose un algorithme utilisant une architecture visuelle biologique pour rĂ©aliser une dĂ©tection de contours. Notre travail a consistĂ© Ă Ă©valuer, en vue d'une implantation DSP, chaque opĂ©rateur en terme de coĂ»t de calculs, mĂ©moires et communications. Leur rĂ©partition est Ă©tudiĂ©e pour un environnement multiprocesseurs. La solution matĂ©rielle proposĂ©e rĂ©pond aux besoins temps rĂ©el nĂ©cessaires aux applications embarquĂ©es oĂč l'on recherche un opĂ©rateur homogĂšne, performant et sans rĂ©glage de paramĂštres de vision s'accommodant aux diffĂ©rentes caractĂ©ristiques des images naturelles
Numerical study of a non-equilibrium interface model
We have carried out extensive computer simulations of one-dimensional models
related to the low noise (solid-on-solid) non-equilibrium interface of a two
dimensional anchored Toom model with unbiased and biased noise. For the
unbiased case the computed fluctuations of the interface in this limit provide
new numerical evidence for the logarithmic correction to the subnormal L^(1/2)
variance which was predicted by the dynamic renormalization group calculations
on the modified Edwards-Wilkinson equation. In the biased case the simulations
are in close quantitative agreement with the predictions of the Collective
Variable Approximation (CVA), which gives the same L^(2/3) behavior of the
variance as the KPZ equation.Comment: 15 pages revtex, 4 Postscript Figure
Properties of mm galaxies: Constraints from K-band blank fields
We have used the IRAM Plateau de Bure mm interferometer to locate with
subarcsecond accuracy the dust emission of three of the brightest 1.2mm sources
in the NTT Deep Field (NDF) selected from our 1.2mm MAMBO survey at the IRAM
30m telescope. We combine these results with deep B to K imaging and VLA
interferometry. Strikingly, none of the three accurately located mm galaxies
MMJ120546-0741.5, MMJ120539-0745.4, and MMJ120517-0743.1 has a K-band
counterpart down to the faint limit of K>21.9. This implies that these three
galaxies are either extremely obscured and/or are at very high redshifts
(z>~4). We combine our results with literature data for 11 more (sub)mm
galaxies that are identified with similar reliability. In terms of their K-band
properties, the sample divides into three roughly equal groups: (i) undetected
to K~22, (ii) detected in the near-infrared but not the optical and (iii)
detected in the optical with the possibility of optical follow-up spectroscopy.
We find a trend in this sample between near-infrared to submm and submm to
radio spectral indices, which in comparison to spectral energy distributions
(SEDs) of low redshift infrared luminous galaxies suggests that the most
plausible primary factor causing the extreme near-infrared faintness of our
objects is their high redshift. We show that the near-infrared to radio SEDs of
the sample are inconsistent with SEDs that resemble local far-infrared cool
galaxies with moderate luminosities, which were proposed in some models of the
submm sky. We briefly discuss the implications of the results for our
understanding of galaxy formation.Comment: aastex, 5 figures. Accepted by Ap
ESO Imaging Survey: infrared observations of CDF-S and HDF-S
This paper presents infrared data obtained from observations carried out at
the ESO 3.5m New Technology Telescope (NTT) of the Hubble Deep Field South
(HDF-S) and the Chandra Deep Field South (CDF-S). These data were taken as part
of the ESO Imaging Survey (EIS) program, a public survey conducted by ESO to
promote follow-up observations with the VLT. In the HDF-S field the infrared
observations cover an area of ~53 square arcmin, encompassing the HST WFPC2 and
STIS fields, in the JHKs passbands. The seeing measured in the final stacked
images ranges from 0.79" to 1.22" and the median limiting magnitudes (AB
system, 2" aperture, 5sigma detection limit) are J_AB~23.0, H_AB~22.8 and
K_AB~23.0 mag. Less complete data are also available in JKs for the adjacent
HST NICMOS field. For CDF-S, the infrared observations cover a total area of
\~100 square arcmin, reaching median limiting magnitudes (as defined above) of
J_AB~23.6 and K_AB~22.7 mag. For one CDF-S field H-band data are also
available. This paper describes the observations and presents the results of
new reductions carried out entirely through the un-supervised, high-throughput
EIS Data Reduction System and its associated EIS/MVM C++-based image processing
library developed, over the past 5 years, by the EIS project and now publicly
available. The paper also presents source catalogs extracted from the final
co-added images which are used to evaluate the scientific quality of the survey
products, and hence the performance of the software. This is done comparing the
results obtained in the present work with those obtained by other authors from
independent data and/or reductions carried out with different software packages
and techniques. The final science-grade catalogs and co-added images are
available at CDS.Comment: Accepted for publication in A&A, 13 pages, 12 figures; a full
resolution version of the paper is available from
http://www.astro.ku.dk/~lisbeth/eisdata/papers/4528.pdf ; related catalogs
and images are available through http://www.astro.ku.dk/~lisbeth/eisdata
VLT-ISAAC near-IR Spectroscopy of ISO selected Hubble Deep Field South Galaxies
We report the results of near-infrared VLT-ISAAC spectroscopy of a sample of
12 galaxies at z = 0.4-1.4, drawn from the ISOCAM survey of the Hubble Deep
Field South. We find that the rest frame R-band spectra of the ISOCAM galaxies
resemble those of powerful dust-enshrouded starbursts. Halpha emission is
detected in 11 out of 12 objects down to a flux limit of 7x10^(-17) erg/cm^2/s,
corresponding to a luminosity limit of 10^41 erg/s at z = 0.6, (for an Ho = 50
and Omega = 0.3 cosmology). From the Halpha luminosities in these galaxies we
derive estimates of the star formation rate in the range 2--50 Mo/yr for
stellar masses 1--100 Mo. The raw Halpha-based star formation rates are an
order of magnitude or more lower than SFR(FIR) estimates based on ISOCAM LW3
fluxes. If the Halpha emission is corrected for extinction the median offset is
reduced to a factor of 3. The sample galaxies are part of a new population of
optically faint but infrared--luminous active starburst galaxies, which are
characterized by an extremely high rate of evolution with redshift up to z~1.5
and expected to contribute significantly to the cosmic far-IR extragalactic
background.Comment: Accepted for publication in the Astrophysical Journal Letters, 16
pages, 2 figure
Physical and dynamical properties of the main belt triple asteroid (87) Sylvia
We present the analysis of high angular resolution observations of the triple
Asteroid (87) Sylvia collected with three 8-10 m class telescopes (Keck, VLT,
Gemini North) and the Hubble Space Telescope. The moons' mutual orbits were
derived individually using a purely Keplerian model. We computed the position
of Romulus, the outer moon of the system, at the epoch of a recent stellar
occultation which was successfully observed at less than 15 km from our
predicted position, within the uncertainty of our model. The occultation data
revealed that the Moon, with a surface-area equivalent diameter
Ds=23.10.7km, is strongly elongated (axes ratio of
2.70.32.70.3), significantly more than single asteroids of similar
size in the main-belt. We concluded that its shape is probably affected by the
tides from the primary. A new shape model of the primary was calculated
combining adaptive-optics observations with this occultation and 40 archived
light-curves recorded since 1978. The difference between the
J2=0.024-0.009+0.016 derived from the 3-D shape model assuming an homogeneous
distribution of mass for the volume equivalent diameter Dv=27310km primary
and the null J2 implied by the Keplerian orbits suggests a non-homogeneous mass
distribution in the asteroid's interior
- âŠ