1,518 research outputs found
Abundances and kinematics for ten anticentre open clusters
Open clusters are distributed all across the disk and are convenient tracers
of its properties. In particular, outer disk clusters bear a key role for the
investigation of the chemical evolution of the Galactic disk. The goal of this
study is to derive homogeneous elemental abundances for a sample of ten outer
disk OCs, and investigate possible links with disk structures such as the
Galactic Anticenter Stellar Structure. We analyse high-resolution spectra of
red giants, obtained from the HIRES@Keck and UVES@VLT archives. We derive
elemental abundances and stellar atmosphere parameters by means of the
classical equivalent width method. We also performed orbit integrations using
proper motions. The Fe abundances we derive trace a shallow negative radial
metallicity gradient of slope -0.027+/-0.007 dex.kpc-1 in the outer 12 kpc of
the disk. The [alpha/Fe] gradient appears flat, with a slope of 0.006+/-0.007
dex.kpc-1 . The two outermost clusters (Be 29 and Sau 1) appear to follow
elliptical orbits. Be 20 also exhibits a peculiar orbit with a large excursion
above the plane. The irregular orbits of the three most metal-poor clusters (of
which two are located at the edge of the Galactic disk), if confirmed by more
robust astrometric measurements such as those of the Gaia mission, are
compatible with an inside-out formation scenario for the Milky Way, in which
extragalactic material is accreted onto the outer disk. We cannot determine if
Be 20, Be 29,and Sau 1 are of extragalactic origin, as they may be old genuine
Galactic clusters whose orbits were perturbed by accretion events or minor
mergers in the past 5 Gyr, or they may be representants of the thick disk
population. The nature of these objects is intriguing and deserves further
investigations in the near future.Comment: 17 pages, 9 figures; accepted for publication in A&
The chemistry of planetary nebulae and HII regions in the dwarf galaxies Sextans A and B from deep VLT spectra
Spectroscopic observations obtained with the VLT of one planetary nebula (PN)
in Sextans A and of five PNe in Sextans B and of several HII regions (HII) in
these two dwarf irregular galaxies are presented. The extended spectral
coverage, from 320.0 to 1000.0nm, and the large telescope aperture allowed us
to detect a number of emission lines, covering more than one ionization stage
for several elements (He, O, S, Ar). The electron temperature (Te) diagnostic
[OIII] line at 436.3 nm was measured in all six PNe and in several HII allowing
for an accurate determination of the ionic and total chemical abundances by
means of the Ionization Correction Factors method. For the time being, these
PNe are the farthest ones where such a direct measurement of the Te is
obtained. In addition, all PNe and HII were also modelled using the
photoionization code CLOUDY. The physico-chemical properties of PNe and HII are
presented and discussed. A small dispersion in the oxygen abundance of HII was
found in both galaxies: 12 + (O/H)=7.60.2 in SextansA, and
7.80.2 in SextansB. For the five PNe of SextansA, we find that 12 +
(O/H)=8.00.3, with a mean abundance consistent with that of HII. The
only PN known in SextansA appears to have been produced by a quite massive
progenitor, and has a significant nitrogen overabundance. In addition, its
oxygen abundance is 0.4 dex larger than the mean abundance of HII, possibly
indicating an efficient third dredge-up for massive, low-metallicity PN
progenitors. The metal enrichment of both galaxies is analyzed using these new
data.Comment: 19 pages, 11 figures, Accepted by A&
Atomic and Molecular Data for Optical Stellar Spectroscopy
High-precision spectroscopy of large stellar samples plays a crucial role for
several topical issues in astrophysics. Examples include studying the chemical
structure and evolution of the Milky Way galaxy, tracing the origin of chemical
elements, and characterizing planetary host stars. Data are accumulating from
instruments that obtain high-quality spectra of stars in the ultraviolet,
optical and infrared wavelength regions on a routine basis. These instruments
are located at ground-based 2- to 10-m class telescopes around the world, in
addition to the spectrographs with unique capabilities available at the Hubble
Space Telescope. The interpretation of these spectra requires high-quality
transition data for numerous species, in particular neutral and singly ionized
atoms, and di- or triatomic molecules. We rely heavily on the continuous
efforts of laboratory astrophysics groups that produce and improve the relevant
experimental and theoretical atomic and molecular data. The compilation of the
best available data is facilitated by databases and electronic infrastructures
such as the NIST Atomic Spectra Database, the VALD database, or the Virtual
Atomic and Molecular Data Centre (VAMDC). We illustrate the current status of
atomic data for optical stellar spectra with the example of the Gaia-ESO Public
Spectroscopic Survey. Data sources for 35 chemical elements were reviewed in an
effort to construct a line list for a homogeneous abundance analysis of up to
100000 stars.Comment: Published 30 April 2015 in Physica Script
The metallicity gradient of M 33: chemical abundances of HII regions
We present spectroscopic observations of a sample of 72 emission-line
objects, including mainly HII regions, in the spiral galaxy M 33. Spectra were
obtained with the multi-object, wide field spectrograph AF2/WYFFOS at the 4.2m
WHT telescope. Line intensities, extinction, and electron density were
determined for the whole sample of objects. The aim of the present work was to
derive chemical and physical parameters of a set of HII regions, and from them
the metallicity gradient. Electron temperatures and chemical abundances were
derived for the 14 HII regions where both [OII] and [OIII] emission line fluxes
were measured, including the electron temperature sensitive emission line
[OIII] 436.3 nm and in a few cases [NII] 575.5 nm. The ionization correction
factor (ICF) method was used to derive the total chemical abundances. The
presence of abundance gradients was inferred from the radial behaviour of
several emission-line ratios, and accurately measured from chemical abundances
directly derived in 14 HII regions. The oxygen abundances of our HII regions,
located in the radial region from ~2 to ~7.2 kpc, gave an oxygen gradient
-0.054+/-0.011 dex/kpc The overall oxygen gradient for M 33 obtained using ours
and previous oxygen determinations in a large number of HII regions with direct
electron temperature determination as well as abundance in young stars
presented a two slope shape: -0.19 dex/kpc for the central regions (R<3kpc),
and -0.038dex/kpc for the outer regions (R>=3kpc).Comment: 16 pages, 14 figures, A&A accepted 10/05/200
Crustacea, Isopoda, Oniscidea Latreille, 1802: New continent record and distribution extension in Brazil
Terrestrial Isopods were sampled in four protected Atlantic Forest areas located in Serra do Mar, state of SĂŁoPaulo, southeastern Brazil. A total of 2,217 individuals of six species (Atlantoscia sp., Benthana werneri, Pseudodiploexochustabularis, Pudeoniscus obscurus, Styloniscus spinosus and Trichorhina sp.) were captured in pitfall traps. The exotic speciesS. spinosus is recorded for the first time for the Americas. Another introduced species, P. tabularis, previously recorded onlyfrom the state of Rio Grande do Sul, had its geographic distribution extended to the state of SĂŁo Paulo. The most abundantisopods in this study belong to an undescribed species of Atlantoscia
Uso da espectroscopia de refletĂąncia no infravermelho prĂłximo visando uma anĂĄlise discriminatĂłria de diferentes cultivares do gĂȘnero Paspalum.
Editado por Ana Rita de AraĂșjo Nogueira, Simone Cristina MĂ©o Niciur
The surface proteomic profile of serum extracellular vesicles as a diagnostic and prognostic tool in breast cancer
The diagnosis of breast cancer in the early stage is essential for a favorable prognosis. Extracellular vesicles isolated from body fluids have a central role in breast cancer development due to their biochemical components. Among the biochemical components, surface proteins mediate vesicle interactions with elements of the extracellular milieu, the extracellular matrix, and neighboring cells. The identification of specific surface proteomic profile has been regarded as an easy and reproducible means to define cancer parameters, identify markers for a diagnosis, and determine targets for therapeutical treatments. In this review, we will focus on annexins, tetraspanins, integrins, immune checkpoint proteins, and growth factor receptors that have been identified on the surface of extracellular vesicles isolated from the serum of patients with breast cancer and that have been found to be relevant diagnostic and prognostic biomarkers
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