2,766 research outputs found
New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools: II. SDSS DR7 vs UKIDSS LAS DR6, SDSS DR7 vs UKIDSS LAS DR8, SDSS DR9 vs UKIDSS LAS DR10, and SDSS DR7 vs 2MASS
We aim at developing an efficient method to search for late-type subdwarfs
(metal-depleted dwarfs with spectral types >M5) to improve the current
statistics. Our objectives are: improve our knowledge of metal-poor low-mass
dwarfs, bridge the gap between the late-M and L types, determine their surface
density, and understand the impact of metallicity on the stellar and substellar
mass function.
We carried out a search cross-matching the SDSS, 2MASS, and UKIDSS using
STILTS, Aladin, and Topcat. We considered different photometric and proper
motion criteria for our selection. We identified 29 and 71 late-type subdwarf
candidates in each cross-correlation over 8826 and 3679 square degrees,
respectively. We obtained low-resolution optical spectra for 71 of our
candidates with GTC, NOT, and VLT and retrieved spectra for 30 candidates from
the SDSS spectroscopic database. We classified 92 candidates based on 101
optical spectra using two methods: spectral indices and comparison with
templates of known subdwarfs.
We confirmed 86% and 94% of the candidates as late-type subdwarfs from the
SDSS vs 2MASS and SDSS vs UKIDSS cross-matches, respectively. These subdwarfs
have spectral types ranging between M5 and L0.5 and SDSS magnitudes in the
r=19.4-23.3 mag range. Our new late-type M discoveries include 49 subdwarfs, 25
extreme subdwarfs, six ultrasubdwarfs, one subdwarf/extreme subdwarf, and two
dwarfs/subdwarfs. We derived a surface density of late-type subdwarfs of
0.040 per square degree in the SDSS DR7 vs UKIDSS LAS DR10
cross-match. We also checked the AllWISE photometry of known and new subdwarfs
and found that mid-infrared colours of M subdwarfs do not appear to differ from
their solar-metallicity counterparts of similar spectral types. However, the
J-W2 and J-W1 colours are bluer for lower metallicity dwarfs. (abstract
strongly abridged)Comment: 28 pages, 4 Tables, 10 figures, 1 appendix. Accepted to A&A.
Photometry and spectra available in a dedicated archive on late-type
subdwarfs at http://svo2.cab.inta-csic.es/vocats/ltsa
Leishmania (Viannia) spp. dissemination and tissue tropism in naturally infected dogs (Canis familiaris).
First evidence is presented for Leishmania (Viannia) spp. dissemination and tissue tropism in the domestic dog. Using PCR and histology, parasites were detected in the conjunctiva, lung, lymph nodes and ovaries of 2 naturally infected Peruvian dogs. The detection of parasites in the blood indicates that parasite dissemination to those organs may have been haematogenous
A two-temperature open-source CFD model for hypersonic reacting flows, part two : multi-dimensional analysis
hy2Foam is a newly-coded open-source two-temperature computational fluid dynamics (CFD) solver that has previously been validated for zero-dimensional test cases. It aims at (1) giving open-source access to a state-of-the-art hypersonic CFD solver to students and researchers; and (2) providing a foundation for a future hybrid CFD-DSMC (direct simulation Monte Carlo) code within the OpenFOAM framework. This paper focuses on the multi-dimensional verification of hy2Foam and firstly describes the different models implemented. In conjunction with employing the coupled vibration-dissociation-vibration (CVDV) chemistry–vibration model, novel use is made of the quantum-kinetic (QK) rates in a CFD solver. hy2Foam has been shown to produce results in good agreement with previously published data for a Mach 11 nitrogen flow over a blunted cone and with the dsmcFoam code for a Mach 20 cylinder flow for a binary reacting mixture. This latter case scenario provides a useful basis for other codes to compare against
Early optical spectra of nova V1369 Cen show presence of Lithium
We present early high resolution spectroscopic observations of the nova V1369
Cen. We have detected an absorption feature at 6695.6 \AA\, that we have
identified as blue--shifted Li I 6708 \AA. The absorption line,
moving at -550 km/s, was observed in five high-resolution spectra of the nova
obtained at different epochs. On the basis of the intensity of this absorption
line we infer that a single nova outburst can inject in the Galaxy
0.3 - 4.8 M. Given the current estimates of
Galactic nova rate, this amount is sufficient to explain the puzzling origin of
the overabundance of Lithium observed in young star populations.Comment: 6 pages, 5 figures, accepted for publication in ApJLetter
Changes in drought tolerance of Pinus radiata in Chile associated with provenance and breeding generation
International audienceAbstractKey messageIn Chile, breeding radiata pine for growth has led to drifts in the degree of drought tolerance of the seedlings. Interior provenances gained a larger tolerance to drought after three breeding generations as shown by larger survival and root/shoot ratio under water shortage, while coastal provenance displayed an opposite trend.•Context Given that rainfall is predicted to decrease and to affect establishment and early survival of radiata pine (Pinus radiata D. Don) in Chile, there is a need to identify more drought tolerant genotypes at seedling stage.•Aims The aim of this study was to test whether provenances of P. radiata originating from interior or from coastal provenances, displayed different responses to short-term water shortage, and whether these responses differed from the first to the third breeding generation.•Methods Three generations of breeding families from two sites in Central Chile were compared. The seedlings were grown during 100 days and subjected to two watering regimes for 45 days. Survival, growth, and biomass allocation to roots and shoots were recorded.•Results The two provenances displayed different responses to drought. Biomass allocation to shoots and survival were significantly reduced by water shortage. The first generation seedlings from the coastal provenance displayed a larger survival rate when exposed to water shortage (i.e., 60 %); this rate decreased in the following breeding generations. On the contrary, the survival rate increased from the first to the third generation in the interior provenance.•Conclusions We observed an important local adaptation to water shortage in the interior provenance. This response may be due to the fact that parent tree populations of the interior provenance have successfully adapted to sites with periodic drought
Ermakov-Lewis angles for one-parameter supersymmetric families of Newtonian free damping modes
We apply the Ermakov-Lewis procedure to the one-parameter damped modes
\tilde{y} recently introduced by Rosu and Reyes, which are related to the
common Newtonian free damping modes y by the general Riccati solution [H.C.
Rosu and M. Reyes, Phys. Rev. E 57, 4850 (1998), physics/9707019]. In
particular, we calculate and plot the angle quantities of this approach that
can help to distinguish these modes from the common y modesComment: 6 pages, twocolumn, 18 figs embedded, only first 9 publishe
Phase Splitting for Periodic Lie Systems
In the context of the Floquet theory, using a variation of parameter
argument, we show that the logarithm of the monodromy of a real periodic Lie
system with appropriate properties admits a splitting into two parts, called
dynamic and geometric phases. The dynamic phase is intrinsic and linked to the
Hamiltonian of a periodic linear Euler system on the co-algebra. The geometric
phase is represented as a surface integral of the symplectic form of a
co-adjoint orbit.Comment: (v1) 15 pages. (v2) 16 pages. Some typos corrected. References and
further comments added. Final version to appear in J. Phys. A
Unveiling the Active Nucleus of Centaurus A
We report new HST WFPC2 and NICMOS observations of the center of the nearest
radio galaxy Centaurus A (NGC 5128) and discuss their implications for our
understanding of the active nucleus and jet. We detect the active nucleus in
the near-IR (K and H) and, for the first time, in the optical (I and V),
deriving the spectral energy distribution of the nucleus from the radio to
X-rays. The optical and part of the near-IR emission can be explained by the
extrapolation of the X-ray power law reddened by A_V~14mag, a value consistent
with other independent estimates.
The 20pc-scale nuclear disk discovered by Schreier et al. (1998) is detected
in the [FeII] 1.64mic line and presents a morphology similar to that observed
in Pa alpha with a [FeII]/Pa alpha ratio typical of low ionization Seyfert
galaxies and LINERs. NICMOS 3 Pa alpha observations in a 50"x50" circumnuclear
region suggest enhanced star formation (~0.3Msun/yr) at the edges of the
putative bar seen with ISO, perhaps due to shocks driven into the gas.
The light profile, reconstructed from V, H and K observations, shows that
Centaurus A has a core profile with a resolved break at ~4" and suggests a
black--hole mass of ~10^9 Msun. A linear blue structure aligned with the
radio/X-ray jet may indicate a channel of relatively low reddening in which
dust has been swept away by the jet.Comment: 19 pages, 13 figures, Astrophysical Journal, in press. High quality
figures available at http://www.arcetri.astro.it/~marconi/colpic.htm
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