3,737 research outputs found
Evidence for azimuthal variations of the oxygen abundance gradient tracing the spiral structure of the galaxy HCG91c
Context. The distribution of elements in galaxies forms an important
diagnostic tool to characterize the system's formation and evolution. This tool
is however complex to use in practice, as galaxies are subject to a range of
simultaneous physical processes active from pc to kpc scales. This renders
observations of the full optical extent of galaxies down to sub-kpc scales
essential. Aims. Using the WiFeS integral field spectrograph, we previously
detected abrupt and localized variations in the gas-phase oxygen abundance of
the spiral galaxy HCG91c. Here, we follow-up on these observations to map
HCG91c's disk out to ~2Re at a resolution of 600pc, and characterize the
non-radial variations of the gas-phase oxygen abundance in the system. Methods.
We obtained deep MUSE observations of the target under ~0.6 arcsec seeing
conditions. We perform both a spaxel-based and aperture-based analysis of the
data to map the spatial variations of 12+log(O/H) across the disk of the
galaxy. Results. We confirm the presence of rapid variations of the oxygen
abundance across the entire extent of the galaxy previously detected with
WiFeS, for all azimuths and radii. The variations can be separated in two
categories: a) localized and associated with individual HII regions, and b)
extended over kpc scales, and occurring at the boundaries of the spiral
structures in the galaxy. Conclusions. Our MUSE observations suggest that the
enrichment of the interstellar medium in HGC91c has proceeded preferentially
along spiral structures, and less efficiently across them. Our dataset
highlights the importance of distinguishing individual star-forming regions
down to scales of a few 100pc when using integral field spectrographs to
spatially resolve the distribution of oxygen abundances in a given system, and
accurately characterize azimuthal variations and intrinsic scatter.Comment: 12 pages, 11 figures, accepted for publication in A&A. Supplementary
movie assocociated with Fig. 8 is available (until publication) at:
http://www.sc.eso.org/~fvogt/supp_mat/HCG91c/O_gradient.mp
Galaxy Interactions in Compact Groups II: abundance and kinematic anomalies in HCG 91c
Galaxies in Hickson Compact Group 91 (HCG 91) were observed with the WiFeS
integral field spectrograph as part of our ongoing campaign targeting the
ionized gas physics and kinematics inside star forming members of compact
groups. Here, we report the discovery of HII regions with abundance and
kinematic offsets in the otherwise unremarkable star forming spiral HCG 91c.
The optical emission line analysis of this galaxy reveals that at least three
HII regions harbor an oxygen abundance ~0.15 dex lower than expected from their
immediate surroundings and from the abundance gradient present in the inner
regions of HCG 91c. The same star forming regions are also associated with a
small kinematic offset in the form of a lag of 5-10 km/s with respect to the
local circular rotation of the gas. HI observations of HCG 91 from the Very
Large Array and broadband optical images from Pan-STARRS suggest that HCG 91c
is caught early in its interaction with the other members of HCG 91. We discuss
different scenarios to explain the origin of the peculiar star forming regions
detected with WiFeS, and show that evidence point towards infalling and
collapsing extra-planar gas clouds at the disk-halo interface, possibly as a
consequence of long-range gravitational perturbations of HCG 91c from the other
group members. As such, HCG 91c provides evidence that some of the
perturbations possibly associated with the early phase of galaxy evolution in
compact groups impact the star forming disk locally, and on sub-kpc scales.Comment: 25 pages, 21 figures, MNRAS accepted. Until publication of the
article, the interactive component of Figure 4 is available at this URL:
http://www.mso.anu.edu.au/~fvogt/website/misc.htm
Potencialidades hÃdricas superficiais de Fernando de Noronha, PE, e alternativas para incremento da oferta.
A disponibilidade de recursos hÃdricos para usos múltiplos, com ênfase no abastecimento público, é questão da mais alta relevância e depende de aspectos edáficos, hidrológicos, ambientais e de gestão. Avaliou-se o potencial hÃdrico de bacias hidrográficas da Ilha de Fernando de Noronha, com vistas a dar suporte à gestão da água no arquipélago; para isto se delimitaram e caracterizaram cinco bacias representativas e se estimou a precipitação efetiva através do método da Curva Número. Adicionalmente, foram investigadas as caracterÃsticas de infiltração dos principais solos do arquipélago. Verifica-se que, em geral, as bacias hidrográficas têm limitada infiltrabilidade e elevado potencial de escoamento, constatando-se o potencial de incremento de oferta de água superficial superior a 90%, desde que se contemple a utilização racional das principais bacias existentes. Dentre os solos analisados, os Cambissolos Háplicos Vertissólicos e os Vertissolos são os solos de menor infiltrabilidade e, portanto, de maior contribuição à macrodrenagem do arquipélago. Sugere-se a utilização das bacias estudadas no abastecimento doméstico da Ilha, de modo a incrementar a disponibilidade de água no local
Biopesticide activity from drimanic compounds to control tomato pathogens
Indexación: Scopus.Tomato crops can be affected by several infectious diseases produced by bacteria, fungi, and oomycetes. Four phytopathogens are of special concern because of the major economic losses they generate worldwide in tomato production; Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato, causative agents behind two highly destructive diseases, bacterial canker and bacterial speck, respectively; fungus Fusarium oxysporum f. sp. lycopersici that causes Fusarium Wilt, which strongly affects tomato crops; and finally, Phytophthora spp., which affect both potato and tomato crops. Polygodial (1), drimenol (2), isonordrimenone (3), and nordrimenone (4) were studied against these four phytopathogenic microorganisms. Among them, compound 1, obtained from Drimys winteri Forst, and synthetic compound 4 are shown here to have potent activity. Most promisingly, the results showed that compounds 1 and 4 affect Clavibacter michiganensis growth at minimal inhibitory concentrations (MIC) values of 16 and 32 μg/mL, respectively, and high antimycotic activity against Fusarium oxysporum and Phytophthora spp. with MIC of 64 μg/mL. The results of the present study suggest novel treatment alternatives with drimane compounds against bacterial and fungal plant pathogens. © 2018 by the authors.https://www.mdpi.com/1420-3049/23/8/205
Predisposition To Metabolic Acidosis Induced By Topiramate.
Metabolic acidosis induced by topiramate is a well documented but infrequent adverse event. The objective was to demonstrate the lowering of carbon dioxide serum levels, which is usually asymptomatic but may facilitate the occurrence of metabolic acidosis in patients using topiramate. We evaluated, prospectively, the carbon dioxide serum levels of 18 patients seen at the epilepsy clinic of our university hospital, before and 3 months after introducing topiramate. Five patients were female and 13 were male, age ranging from 2 to 16 years old (mean=9. 3). Carbon dioxide mean serum levels were 25 and 21.2 mmol/L (normal = 22 to 30), before and 3 months after introducing topiramate, respectively. Dose ranged from 2.08 to 11.76 mg/kg/day (mean=6. 7mg/kg/day). Adverse events were anorexia, nausea and somnolence. We conclude that the lowering of carbon dioxide serum levels induced by topiramate is mostly asymptomatic, but may facilitate the occurrence of metabolic acidosis. Since patients in use of topiramate have refractory epilepsy, they may need epilepsy surgery, and must be carefully monitored for the risk of metabolic acidosis during surgery.581021-
Seyfert's Sextet: A Slowly Dissolving Stephan's Quintet?
We present a multiwavelength study of the highly evolved compact galaxy group
known as Seyfert's Sextet (HCG79: SS). We interpret SS as a 2-3 Gyr more
evolved analog of Stephan's Quintet (HCG92: SQ). We postulate that SS formed by
sequential acquisition of 4-5 primarily late-type field galaxies. Four of the
five galaxies show an early-type morphology which is likely the result of
secular evolution driven by gas stripping. Stellar stripping has produced a
massive/luminous halo and embedded galaxies that are overluminous for their
size. These are interpreted as remnant bulges of the accreted spirals. H79d
could be interpreted as the most recent intruder being the only galaxy with an
intact ISM and uncertain evidence for tidal perturbation. In addition to
stripping activity we find evidence for past accretion events. H79b (NGC6027)
shows a strong counter-rotating emission line component interpreted as an
accreted dwarf spiral. H79a shows evidence for an infalling component of gas
representing feedback or possible cross fueling by H79d. The biggest challenge
to this scenario involves the low gas fraction in the group. If SS formed from
normal field spirals then much of the gas is missing. Finally, despite its
advanced stage of evolution, we find no evidence for major mergers and infer
that SS (and SQ) are telling us that such groups coalesce via slow dissolution.Comment: 70 pages, 19 figures, 15 tables - accepted for publication in the
Astronomical Journa
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