We analysed red giant branch stars in 16 Galactic globular clusters, computing their atmospheric parameters both from the photometry and from excitation and ionisation balances. The spectroscopic ...parameters are lower than the photometric ones and this discrepancy increases with decreasing metallicity, reaching differences of ~350 K in effective temperature and ~1 dex in surface gravity at Fe/H ~ –2.5 dex. We demonstrate that the spectroscopic parameters are inconsistent with the position of the stars in the colour-magnitude diagram, providing overly low temperatures and gravities, and predicting that the stars are up to about 2.5 magnitudes brighter than the observed magnitudes. The parameter discrepancy is likely due to inadequacies in the adopted physics; in particular the assumption of a one-dimensional geometry could be the origin of the observed slope between iron abundances and excitation potential that leads to low temperatures. However, the current modelling of 3D/NLTE radiative transfer for giant stars seems to be unable to totally erase this slope. We conclude that the spectroscopic parameters are incorrect for metallicity lower than –1.5 dex and that photometric temperatures and gravities should be adopted for these red giant stars. We provide a simple relation to correct the spectroscopic temperatures in order to put them onto a photometric scale.
Plastics are now a major environmental concern worldwide with their widespread contamination and accumulation. Microplastic particle (< 5 mm) is an emerging pollution issue as it is being detected ...worldwide in aquatic and terrestrial ecosystems, but relatively little is known in tropical regions. This study determined the (1) abundance of microplastics in sediment and (2) in situ and laboratory ingestion rates of microplastics in three scarcely studied tropical bivalve mollusc species (
Donax
sp.,
Meretrix meretrix
, and
Katelysia hiantina
) in Panguil Bay, Southern Philippines. A total of 2258 microplastic particles (62.72 ± 18.31 items/m
2
) were found on the sediment samples. Filament/fiber is the most abundant type of microplastic in terms of morphology, while black and blue are the dominant colors of microplastic particles. There were 1495 microplastic particles (4.15 ± 3.37 particles/clam) present in the clam tissues, of which polypropylene (PP) and rayon (RY) polymers are the most common, whereas
K. hiantina
(707 particles) showed the highest amount of microplastics. The number of ATR-FTIR-confirmed polymer types in the wild clams is greater than that in the sediments. The study reveals abundant microplastics in sediments and in the three species of bivalve individuals from the wild. All clams ingested low-density polyethylene (LDPE) microplastic particles in the laboratory. The mean number of LDPE microplastic particles ingested by clams is 4.62 ± 2.40 particles/clam/7days, with the highest value observed in
K. hiantina
. Additionally,
Donax
sp.,
M. meretrix
, and
K. hiantina
could ingest high densities of 40–60-μm microplastic particles.
Context: The effective temperature scale of FGK stars, especially at the lowest metallicities remains a major problem in the chemical abundance analysis of metal-poor stars. Aims: We present a new ...implementation of the infrared flux method (IRFM) using the 2MASS catalogue. Methods: We computed the theoretical quantities in the 2MASS JHKs filters by integrating theoretical fluxes computed from ATLAS models, and compare them directly with the observed 2MASS JHKs magnitudes. This is the main difference between our implementation of the IRFM and that of Ramírez & Meléndez (2005, ApJ, 626, 446, hereafter RM05), since to introduce new stars at the lowest metallicities they transform the 2MASS JHKs magnitudes into the TCS photometric system. We merge in our sample the stars from Alonso et al. (1996, A&AS, 117, 227, hereafter AAM96; 1999, A&AS, 139, 335, hereafter AAM99), and other studies to appropriately cover a wide range of metallicities, ending up with 555 dwarf and subgiant field stars and 264 giant field stars. We derived a new bolometric flux calibration using the available Johnson-Cousins UBV(RI)C and the 2MASS JHKs photometry. We also computed new T_eff versus colour empirical calibrations using our extended sample of stars. Results: We derived effectives temperatures for almost all the stars in the AAM96 and AAM99 samples and find that our scales of temperature are hotter by ˜ }64 K (sigma_T=104 K, N=332 dwarfs) and {˜54 K with a sigma_T=131 K (N=202 giants). The same comparison with the sample of RM05 for stars with Fe/H
Context. Low-mass dwarf spheroidal galaxies are key objects for our understanding of the chemical evolution of the pristine Universe and the Local Group of galaxies. Abundance ratios in stars of ...these objects can be used to better understand their star formation and chemical evolution. Aims. We report on the analysis of a sample of 11 stars belonging to five different ultra-faint dwarf spheroidal galaxies (UfDSph) that is based on X-Shooter spectra obtained at the VLT. Methods. Medium-resolution spectra have been used to determine the detailed chemical composition of their atmosphere. We performed a standard 1D LTE analysis to compute the abundances. Results. Considering all the stars as representative of the same population of low-mass galaxies, we found that the α/Fe ratios vs.s Fe/H decreases as the metallicity of the star increases in a way similar to that which is found for the population of stars that belong to dwarf spheroidal galaxies. The main difference is that the solar α/Fe is reached at a much lower metallicity for the UfDSph than for the dwarf spheroidal galaxies. We report for the first time the abundance of strontium in CVn II. The star we analyzed in this galaxy has a very high Sr/Fe and a very low upper limit of barium which makes it a star with an exceptionally high Sr/Ba ratio.
ABSTRACT
The Pristine survey uses narrow-band photometry to derive precise metallicities down to the extremely metal-poor regime ($ \rm Fe/H \lt -3$), and currently consists of over 4 million ...FGK-type stars over a sky area of $\sim 2500\, \mathrm{deg}^2$. We focus our analysis on a subsample of ∼80 000 main-sequence turn-off stars with heliocentric distances between 6 and 20 kpc, which we take to be a representative sample of the inner halo. The resulting metallicity distribution function (MDF) has a peak at $ \rm Fe/H =-1.6$, and a slope of Δ(LogN)/$\Delta \rm Fe/H = 1.0 \pm 0.1$ in the metallicity range of $-3.4\; \lt\; \rm Fe/H\; \lt -2.5$. This agrees well with a simple closed-box chemical enrichment model in this range, but is shallower than previous spectroscopic MDFs presented in the literature, suggesting that there may be a larger proportion of metal-poor stars in the inner halo than previously reported. We identify the Monoceros/TriAnd/ACS/EBS/A13 structure in metallicity space in a low-latitude field in the anticentre direction, and also discuss the possibility that the inner halo is dominated by a single, large merger event, but cannot strongly support or refute this idea with the current data. Finally, based on the MDF of field stars, we estimate the number of expected metal-poor globular clusters in the Milky Way halo to be 5.4 for $ \rm Fe/H\; \lt\; -2.5$ and 1.5 for $ \rm Fe/H\; \lt\; -3$, suggesting that the lack of low-metallicity globular clusters in the Milky Way is not due simply to statistical undersampling.
In the last decade, the photospheric solar metallicity as determined from spectroscopy experienced a remarkable downward revision. Part of this effect can be attributed to an improvement of atomic ...data and the inclusion of NLTE computations, but also the use of hydrodynamical model atmospheres seemed to play a role. This “decrease” with time of the metallicity of the solar photosphere increased the disagreement with the results from helioseismology. With a CO
5
BOLD 3D model of the solar atmosphere, the CIFIST team at the Paris Observatory re-determined the photospheric solar abundances of several elements, among them C, N, and O. The spectroscopic abundances are obtained by fitting the equivalent width and/or the profile of observed spectral lines with synthetic spectra computed from the 3D model atmosphere. We conclude that the effects of granular fluctuations depend on the characteristics of the individual lines, but are found to be relevant only in a few particular cases. 3D effects are not responsible for the systematic lowering of the solar abundances in recent years. The solar metallicity resulting from this analysis is
Z
=0.0153,
Z
/
X
=0.0209.
Context.
The measurement of
α
-element abundances provides a powerful tool for placing constraints on the chemical evolution and star formation history of galaxies. The majority of studies on the
α
...-element sulfur (S) are focused on local stars, making S behavior in other environments an astronomical topic that is yet to be explored in detail.
Aims.
The investigation of S in the Galactic bulge was recently considered for the first time. This work aims to improve our knowledge on S behavior in this component of the Milky Way.
Methods.
We present the S abundances of 74 dwarf and sub-giant stars in the Galactic bulge, along with 21 and 30 F and G thick- and thin-disk stars, respectively. We performed a local thermodynamic equilibrium analysis and applied corrections for non-LTE on high resolution and high signal-to-noise UVES spectra. S abundances were derived from multiplets 1, 6, and 8 in the metallicity range of − 2 < Fe/H < 0.6, by spectrosynthesis or line equivalent widths.
Results.
We confirm that the behavior of S resembles that of an
α
-element within the Galactic bulge. In the S/Fe versus Fe/H diagram, S presents a plateau at low metallicity, followed by a decreasing of S/Fe with the increasing of Fe/H, before reaching S/Fe ~ 0 at a super-solar metallicity. We found that the Galactic bulge is S-rich with respect to both the thick- and thin-disks at − 1 < Fe/H < 0.3, supporting a scenario of more rapid formation and chemical evolution in the Galactic bulge than in the disk.
ABSTRACT
The very massive first stars (m > 100 $\rm M_{\odot }$) were fundamental to the early phases of reionization, metal enrichment, and supermassive black hole formation. Among them, those with ...$140\le \rm m/\rm M_{\odot }\le 260$ are predicted to evolve as Pair Instability Supernovae (PISN) leaving a unique chemical signature in their chemical yields. Still, despite long searches, the stellar descendants of PISN remain elusive. Here we propose a new methodology, the PISN-explorer, to identify candidates for stars with a dominant PISN enrichment. The PISN-explorer is based on a combination of physically driven models, and the FERRE code; and applied to data from large spectroscopic surveys (APOGEE, GALAH, GES, MINCE, and the JINA data base). We looked into more than 1.4 million objects and built a catalogue with 166 candidates of PISN descendants. One of which, 2M13593064+3241036, was observed with UVES at VLT and full chemical signature was derived, including the killing elements, Cu and Zn. We find that our proposed methodology is efficient in selecting PISN candidates from both the Milky Way and dwarf satellite galaxies such as Sextans or Draco. Further high-resolution observations are highly required to confirm our best selected candidates, therefore allowing us to probe the existence and properties of the very massive First Stars.
Commensal microbes are an integral component of mammalian physiology. 16S rRNA gene-specific next generation sequencing from DNA of total organs, swabs or lavages has revolutionized the ...characterization of bacterial communities in virtually every ecological niche of the body. Culturomics, next allowed the isolation and characterization of commensal bacteria in the lab and the establishment of artificial communities of bacteria, which were eventually reintroduced in model organisms. Spatial organization of microbiota within a given host environment is critical to the physiological or pathological phenotypes provoked by commensal microbiota.
In situ
hybridization (ISH) is a complementary technique to sequencing and culturing to visualize the presence of individual bacterial operational taxonomic unit (OTUs) in context of the colonized organ. We recently applied highly sensitive
in situ
RNA hybridization to detection of commensal bacteria in low abundance respiratory tract samples of mice housed under specific pathogen free conditions. This technique allows species-specific detection of living bacteria using RNAScope
TM
technology, while preserving the natural environment of the organ. We here provide a detailed step-by-step protocol describing the detection of commensal lung bacteria in respiratory tissue.
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