Journal articles on the topic 'Abundances'
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1
Lamarche, C., J. D. Smith, K. Kreckel, S. T. Linden, N. S. J. Rogers, E. Skillman, D. Berg, et al. "Direct Far-infrared Metal Abundances (FIRA). I. M101." Astrophysical Journal 925, no. 2 (February 1, 2022): 194. http://dx.doi.org/10.3847/1538-4357/ac3b4f.
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Abstract Accurately determining gas-phase metal abundances within galaxies is critical as metals strongly affect the physics of the interstellar medium. To date, the vast majority of widely used gas-phase abundance indicators rely on emission from bright optical lines, whose emissivities are highly sensitive to the electron temperature. Alternatively, direct-abundance methods exist that measure the temperature of the emitting gas directly, though these methods usually require challenging observations of highly excited auroral lines. Low-lying far-infrared (FIR) fine structure lines are largely insensitive to electron temperature and thus provide an attractive alternative to optically derived abundances. Here, we introduce the far-infrared abundance (FIRA) project, which employs these FIR transitions, together with both radio free–free emission and hydrogen recombination lines, to derive direct, absolute gas-phase oxygen abundances. Our first target is M101, a nearby spiral galaxy with a relatively steep abundance gradient. Our results are consistent with the O++ electron temperatures and absolute oxygen abundances derived using optical direct-abundance methods by the CHemical Abundance Of Spirals (CHAOS) program, with a small difference (∼1.5σ) in the radial abundance gradients derived by the FIR/free–free-normalized versus CHAOS/direct-abundance techniques. This initial result demonstrates the validity of the FIRA methodology—with the promise of determining absolute metal abundances within dusty star-forming galaxies, both locally and at high redshift.
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Reggiani, Henrique, Kevin C. Schlaufman, Brian F. Healy, Joshua D. Lothringer, and David K. Sing. "Evidence that the Hot Jupiter WASP-77 A b Formed Beyond Its Parent Protoplanetary Disk’s H2O Ice Line." Astronomical Journal 163, no. 4 (March 10, 2022): 159. http://dx.doi.org/10.3847/1538-3881/ac4d9f.
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Abstract Idealized protoplanetary disk and giant planet formation models have been interpreted to suggest that a giant planet’s atmospheric abundances can be used to infer its formation location in its parent protoplanetary disk. It has recently been reported that the hot Jupiter WASP-77 A b has subsolar atmospheric carbon and oxygen abundances with a solar C/O abundance ratio. Assuming solar carbon and oxygen abundances for its host star WASP-77 A, WASP-77 A b’s atmospheric carbon and oxygen abundances possibly indicate that it accreted its envelope interior to its parent protoplanetary disk’s H2O ice line from carbon-depleted gas with little subsequent planetesimal accretion or core erosion. We show that the photospheric abundances of carbon and oxygen in WASP-77 A are supersolar with a subsolar C/O abundance ratio, implying that WASP-77 A b’s atmosphere has significantly substellar carbon and oxygen abundances with a superstellar C/O ratio. Our result possibly indicates that WASP-77 A b’s envelope was accreted by the planet beyond its parent protoplanetary disk's H2O ice line. While numerous theoretical complications to these idealized models have now been identified, the possibility of nonsolar protoplanetary disk abundance ratios confound even the most sophisticated protoplanetary disk and giant planet formation models. We therefore argue that giant planet atmospheric abundance ratios can only be meaningfully interpreted relative to the possibly nonsolar mean compositions of their parent protoplanetary disks as recorded in the photospheric abundances of their dwarf host stars.
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Pottasch, S. R. "Chemical composition of interstellar material." Symposium - International Astronomical Union 106 (1985): 575–84. http://dx.doi.org/10.1017/s0074180900243192.
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Abundances in interstellar clouds, as determined from interstellar absorption lines, are discussed first, including abundances in ‘abnormal’ (high-velocity) clouds. HII-region abundances are then discussed and compared to results from the interstellar clouds. The present status of an abundance gradient as determined from HII regions is given. Abundances in planetary nebulae are then given for various categories of nebulae, and compared to HII regions. Finally a short status report on abundances near the galactic center is given.
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Pérez-Mesa, V., O. Zamora, D. A. García-Hernández, Y. Ossorio, T. Masseron, B. Plez, A. Manchado, A. I. Karakas, and M. Lugaro. "On the circumstellar effects on the Li and Ca abundances in massive Galactic O-rich AGB stars." Proceedings of the International Astronomical Union 14, S343 (August 2018): 489–90. http://dx.doi.org/10.1017/s174392131800501x.
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AbstractWe explore the circumstellar effects on the Li and Ca abundances determination in a complete sample of massive Galactic AGB stars. The Li abundance is an indicator of the hot bottom burning (HBB) activation, while the total Ca abundance could be affected by overproduction of the short-lived radionuclide 41Ca by the s-process. Li abundances were previously studied with hydrostatic models, while Ca abundances are determined here for the first time. The pseudo-dynamical abundances of Li and Ca are very similar to the hydrostatic ones, indicating that circumstellar effects are almost negligible. The new Li abundances confirm the (super-)Li-rich character of the sample Li-detected stars, supporting the HBB activation in massive Galactic AGB stars. Most sample stars display nearly solar Ca abundances that are consistent with predictions from the s-process nucleosynthesis models. A minority of the sample stars show a significant Ca depletion. Possible reasons for their (unexpected) low Ca content are given.
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Reijniers, Jonas, Mike Begon, Vladimir S. Ageyev, and Herwig Leirs. "Plague epizootic cycles in Central Asia." Biology Letters 10, no. 6 (June 2014): 20140302. http://dx.doi.org/10.1098/rsbl.2014.0302.
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Infection thresholds, widely used in disease epidemiology, may operate on host abundance and, if present, on vector abundance. For wildlife populations, host and vector abundances often vary greatly across years and consequently the threshold may be crossed regularly, both up- and downward. Moreover, vector and host abundances may be interdependent, which may affect the infection dynamics. Theory predicts that if the relevant abundance, or combination of abundances, is above the threshold, then the infection is able to spread; if not, it is bound to fade out. In practice, though, the observed level of infection may depend more on past than on current abundances. Here, we study the temporal dynamics of plague ( Yersinia pestis infection), its vector (flea) and its host (great gerbil) in the PreBalkhash region in Kazakhstan. We describe how host and vector abundances interact over time and how this interaction drives the dynamics of the system around the infection threshold, consequently affecting the proportion of plague-infected sectors. We also explore the importance of the interplay between biological and detectability delays in generating the observed dynamics.
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Sherman, CS, MR Heupel, SK Moore, A. Chin, and CA Simpfendorfer. "When sharks are away, rays will play: effects of top predator removal in coral reef ecosystems." Marine Ecology Progress Series 641 (May 7, 2020): 145–57. http://dx.doi.org/10.3354/meps13307.
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Shark abundances are decreasing on many coral reefs, but the ecosystem effects of this loss are poorly understood. Rays are a prevalent mesopredator in tropical coral reef ecosystems that are preyed upon by top predators like sharks. Studies have suggested reduced predator abundances lead to increases in mesopredator abundance (mesopredator release). We examined the relationship between top predator abundances and the abundance and behaviour of 2 small benthic ray genera using baited remote underwater video systems (BRUVS) across 6 countries. Where predators were more abundant, 2 genera of small benthic rays were sighted less often, possibly because of lower abundances. Small ray behaviour was also significantly affected by predator abundance. Individuals of focal ray species visited BRUVS significantly fewer times at sites with higher predator abundances. Where predators were less abundant, rays spent significantly more time in the video frame, and were more likely to feed from bait bags. In addition to predator abundance, small ray presence was significantly influenced by reef relief and depth. Neotrygon spp. were more abundant on deeper, lower relief habitats, while Taeniura spp. were more prevalent in reef-associated shallow, high relief habitats. Overall, this study found that predator abundance had a significant effect on small benthic ray abundance and behaviour in the presence of BRUVS. Results demonstrate that changes in both abundance and behaviour associated with predator loss may make the interpretation of phenomenon like mesopredator release more difficult to identify unless behavioural effects are considered.
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Dors, Oli L. "Chemical abundances in Seyfert galaxies – VI. Empirical abundance calibration." Monthly Notices of the Royal Astronomical Society 507, no. 1 (July 30, 2021): 466–74. http://dx.doi.org/10.1093/mnras/stab2166.
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ABSTRACT We derived a bi-dimensional calibration between the emission-line ratios $R_{23}= ([\mathrm{ O}\, {\small {\rm II}}]\,\lambda 3726 +\lambda 3729 +[\mathrm{ O}\mathrm{ }\, {\small {\rm III}}]\,\lambda 4959 + \lambda 5007)/\rm H\,\beta$, ${\it P}=[([\mathrm{ O}\, {\small {\rm III}}]\,\lambda 4959+\lambda 5007)/{\rm H}\,\beta ]/R_{23}$ and the oxygen abundance relative to hydrogen (O/H) in the gas phase of Seyfert 1 and 2 nuclei. In view of this, emission-line intensity ratios for a sample of objects taken from the Sloan Digital Sky Survey Data Release 7 measured by the MPA/JHU group and direct estimates of O/H based on Te-method, adapted for active galactic nuclei (AGNs), are considered. We find no variation of R23 observed along the radii of AGNs, which shows that this line ratio is a good oxygen abundance (O/H) indicator for the class of objects considered in this work. The derived O/H = f(R23, P) relation produces O/H values similar to estimations via Te-method in a wide range of metallicities [$\rm 8.0 \: \lesssim \: 12+\log \,(O/H) \: \lesssim \: 9.2$]. Conversely to star-forming regions in the high-metallicity regime, R23 shows a positive correlation trend with O/H in AGNs. This indicates that the hardness of ionizing radiation is not affected by the metallicities in these objects or narrow-line regions are not significantly modified by changes in the spectral energy distribution due to metallicity variations.
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Rogers, Noah S. J., Evan D. Skillman, Richard W. Pogge, Danielle A. Berg, Kevin V. Croxall, Jordan Bartlett, Karla Z. Arellano-Córdova, and John Moustakas. "CHAOS. VII. A Large-scale Direct Abundance Study in M33." Astrophysical Journal 939, no. 1 (November 1, 2022): 44. http://dx.doi.org/10.3847/1538-4357/ac947d.
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Abstract The dispersion in chemical abundances provides a very strong constraint on the processes that drive the chemical enrichment of galaxies. Due to its proximity, the spiral galaxy M33 has been the focus of numerous chemical abundance surveys to study the chemical enrichment and dispersion in abundances over large spatial scales. The CHemical Abundances Of Spirals project has observed ∼100 H ii regions in M33 with the Large Binocular Telescope (LBT), producing the largest homogeneous sample of electron temperatures (T e ) and direct abundances in this galaxy. Our LBT observations produce a robust oxygen abundance gradient of −0.037 ± 0.007 dex kpc−1 and indicate a relatively small (0.043 ± 0.015 dex) intrinsic dispersion in oxygen abundance relative to this gradient. The dispersions in N/H and N/O are similarly small, and the abundances of Ne, S, Cl, and Ar relative to O are consistent with the solar ratio as expected for α-process or α-process-dependent elements. Taken together, the ISM in M33 is chemically well-mixed and homogeneously enriched from inside out, with no evidence of significant abundance variations at a given radius in the galaxy. Our results are compared to those of the numerous studies in the literature, and we discuss possible contaminating sources that can inflate abundance dispersion measurements. Importantly, if abundances are derived from a single T e measurement and T e –T e relationships are relied on for inferring the temperature in the unmeasured ionization zone, this can lead to systematic biases that increase the measured dispersion up to 0.11 dex.
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Ito, Hiroko, Wako Aoki, Satoshi Honda, Timothy C. Beers, and Nozomu Tominaga. "A very low upper limit for a Be abundance of a carbon-enhanced metal-poor star." Proceedings of the International Astronomical Union 5, S268 (November 2009): 337–38. http://dx.doi.org/10.1017/s1743921310004369.
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AbstractWe performed a 1D LTE chemical abundance analysis of an extremely metal-poor star BD+44°493 ([Fe/H]= −3.7), and set a very low upper limit for its Be abundance: A(Be) < −2.0. It may indicate that the decreasing trend of Be abundances with lower [Fe/H] still holds at [Fe/H] < −3.5, and demonstrate that high C and O abundances do not necessarily imply high Be abundances. However, since the star is a subgiant with Teff ~ 5500K, Be may be depleted.
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Flury, Sophia R., and Edward C. Moran. "Chemical abundances in active galaxies." Monthly Notices of the Royal Astronomical Society 496, no. 2 (June 6, 2020): 2191–203. http://dx.doi.org/10.1093/mnras/staa1563.
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ABSTRACT The Sloan Digital Sky Survey (SDSS) has proved to be a powerful resource for understanding the physical properties and chemical composition of star-forming galaxies in the local Universe. The SDSS population of active galactic nuclei (AGNs) remains as of yet less explored in this capacity. To extend the rigorous study of H ii regions in the SDSS to AGNs, we adapt methods for computing direct-method chemical abundances for application to the narrow-line regions (NLR) of AGNs. By accounting for triply ionized oxygen, we are able to more completely estimate the total oxygen abundance. We find a strong correlation between electron temperature and oxygen abundance due to collisional cooling by metals. Furthermore, we find that nitrogen and oxygen abundances in AGNs are strongly correlated. From the metal–temperature relation and the coupling of nitrogen and oxygen abundances, we develop a new, empirically and physically motivated method for determining chemical abundances from the strong emission lines commonly employed in flux-ratio diagnostic diagrams (BPT diagrams). Our approach, which for AGNs reduces to a single equation based on the BPT line ratios, consistently recovers direct-method abundances over a 1.5 dex range in oxygen abundance with an rms uncertainty of 0.18 dex. We have determined metallicities for thousands of AGNs in the SDSS, and in the process have discovered an ionization-related discriminator for Seyfert and LINER galaxies.
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Gratton, Raffaele G. "Recent Advances in High Dispersion Spectroscopy of Globular Cluster Stars." Symposium - International Astronomical Union 132 (1988): 525–30. http://dx.doi.org/10.1017/s0074180900035610.
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The use CCD detectors has allowed a major progress in abundance derivations for globular cluster stars in the last years. Abundances deduced from high dispersion spectra now correlates well with other abundance indicators. I discuss some problems concerning the derivation of accurate metal abundances for globular clusters using high dispersion spectra from both the old photographic and the most recent CCD data. The discrepant low abundances found by Cohen (1980), from photographic material for M71 giants, are found to be due to the use of too high microturbulences.
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Fuente, Asunción. "Gas phase Elemental abundances in Molecular cloudS (GEMS)." EPJ Web of Conferences 265 (2022): 00005. http://dx.doi.org/10.1051/epjconf/202226500005.
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Gas phase Elemental abundances in Molecular CloudS (GEMS) is an IRAM 30m Large Program aimed at determining the elemental abundances of carbon (C), oxygen (O), nitrogen (N), and sulphur (S) in a selected set of prototypical star forming filaments. Elemental abundances have a key role in the star formation process by driving the gas cooling rate and the gas ionization degree. Defining elemental abundance as the amount of a given atom in volatiles, the elemental abundances of C, O, and N in the interstellar medium are currently known within a factor of a few. However, the elemental abundance of S remains uncertain by several orders of magnitude, and its determination is one of the most challenging goals of this program. This is a review of the observational, theoretical, and modeling effort that GEMS team is doing to improve our knowledge of the sulphur chemistry. Our results suggest that the sulphur elemental abundance depends on the local physical conditions and the star formation activity in the environment.
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Marino, R. A., F. F. Rosales-Ortega, F. Sánchez, and A. Gil de Paz. "New empirical metallicity calibrations: Joint analysis of CALIFA data and literature Te-based measurements." Proceedings of the International Astronomical Union 10, S309 (July 2014): 328. http://dx.doi.org/10.1017/s1743921314010229.
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AbstractIn Marino et al. (2013) we provide revisited empirical calibrations for the oxygen abundances in HII regions based on the O3N2 and N2 indicators. This work is based on the most comprehensive compilation of both Te-based and multiple strong-line (ONS-based) ionized-gas abundance measurements in external galaxies to date in terms of all statistical significance, quality, and coverage of the parameters space. Our dataset compiles the Te-based abundances of 603 HII regions extracted from the literature but also includes new measurements from the CALIFA survey. We also present a comparison between our revisited calibrations with a total of 3423 additional CALIFA HII complexes with abundances derived using the ONS calibration. The O3N2 and N2 indicators can be empirically applied to derive oxygen abundances calibrations from either direct-abundance determinations with random errors of 0.18 and 0.16, respectively, and they show shallower abundance dependencies and statistically significant offsets compared to the classical calibrations (as the one of Pettini & Pagel (2004)).
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Daflon, Simone, Katia Cunha, Ramiro de la Reza, Jon Holtzman, and Cristina Chiappini. "Sulfur Abundances in Orion B Stars." Proceedings of the International Astronomical Union 5, S265 (August 2009): 358–59. http://dx.doi.org/10.1017/s1743921310000918.
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AbstractSulfur abundances are derived for a sample of ten B MS star members of the Orion association. The analysis is based on LTE model atmospheres and non-LTE line formation theory by means of spectrum synthesis analysis of Sii and Siii lines. The abundance distribution obtained for the Orion targets is homogeneous within the errors in the analysis: A(S)=7.15±0.05. This abundance result is in agreement with the solar value and with results for the Orion nebula. The sulfur abundances for Orion combined with previous results for other OB-type stars produce a relatively shallow sulfur abundance gradient with a slope of −0.037±0.012 dex Kpc−1.
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Monier, Richard. "New Determinations of the Surface Abundances of HD 1280." Research Notes of the AAS 7, no. 3 (March 10, 2023): 47. http://dx.doi.org/10.3847/2515-5172/acc255.
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Abstract New abundances for several chemical elements are measured for HD 1280 using updated atomic data and spectrum synthesis. The abundances of calcium and scandium are solar whereas strontium is mildly overabundant. The abundances of helium, magnesium, titanium, chromium, manganese, iron and barium are in good agreement with a former abundance analysis. This reinforces the status of HD 1280 as a normal rapidly rotating A star with essentially normal abundances of elements lighter than iron and mild overabundances of heavier elements which may actually have been present in the environment where the star was born.
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Wahlgren, G. M., K. E. Nielsen, and D. S. Leckrone. "High-resolution spectroscopy of the hot Am star HR 3383." Monthly Notices of the Royal Astronomical Society 500, no. 2 (October 27, 2020): 2451–60. http://dx.doi.org/10.1093/mnras/staa3323.
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ABSTRACT We present the spectrum analysis of the hot Am star HR 3383 (A1 Vm). Hubble Space Telescope STIS and Nordic Optical Telescope SOFIN data are modelled with synthetic spectra, and abundances are investigated for 78 elements. Most light elements up through oxygen show deficiencies, compared to solar abundances, followed by the general trend of increasing abundance enhancement with atomic number that levels off at a 30-fold enhancement at the lanthanide group and heavier elements. The derived element distribution is generally consistent with what is observed in other hot Am stars. Abundances for HR 3383 are also similar to what is seen for the cooler HgMn stars, with the exception of the platinum-group elements that generally show dramatic enhancements in the HgMn stars. Current theory and calculations are able to predict most observed abundances and abundance trends through the iron group. The large number of derived element abundances in this study provides a constraint for theoretical calculations attempting to explain the heavy element abundances in chemically peculiar stars. This paper includes a comprehensive description of spectral lines useful for an abundance analysis of late B and A type stars, and comments are provided on the atomic data. New data for hyperfine structure components for three lines in Lu iii and a single line in Lu ii are presented, based on laboratory spectra. In addition to the stellar spectrum, lines from the interstellar medium are noted for several of the strongest Fe ii ultraviolet transitions.
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KUSAKABE, MOTOHIKO, TOSHITAKA KAJINO, and GRANT J. MATHEWS. "POSSIBILITY OF A SIGNATURE OF THE RADIATIVE DECAY OF RELIC PARTICLES ON LIGHT ELEMENT ABUNDANCES." Modern Physics Letters A 22, no. 25n28 (September 14, 2007): 2019–26. http://dx.doi.org/10.1142/s021773230702525x.
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Recent spectroscopic observations of metal poor stars have indicated that both 7 Li and 6 Li have abundance plateaus as a function of the metallicity. Abundances of 7 Li are about a factor three lower than the primordial abundance predicted by standard big-bang nucleosynthesis (SBBN), and 6 Li abundances are ~ 1/20 of 7 Li , whereas SBBN predicts negligible amounts of 6 Li compared to the detected level. These discrepancies suggest that 6 Li has another cosmological or Galactic origin. Furthermore, it appear that 7 Li (and also 6 Li ) has been depleted from its primordial abundance by some post-BBN processes. We study the possibility that the radiative decay of long-lived particles has affected the cosmological lithium abundances in reality. We calculate the non-thermal nucleosynthesis associated with the radiative decay, and explore the allowed region of the parameters specifying the properties of long-lived particles. We also impose constraints from observations of the CMB energy spectrum. It is found that non-thermal nucleosynthesis could produces 6 Li at the level detected in metal poor halo stars (MPHSs), when the lifetime of the unstable particles is of the order ~ 108 − 1012 s depending on their initial abundance. We conclude that a combination of two different processes could explain the lithium isotopic abundances in MPHSs. First, a non-thermal cosmological nucleosynthesis associated with the radiative decay of unstable particles; and second, about the same degree of stellar depletion of both primordial lithium isotopic abundances. If MPHSs experience 6 Li depletion of factor much greater than ~ 3, the simple radiative decay process can not be the cause of large 6 Li abundances in MPHSs.
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Monier, Richard. "The Abundances of Carbon, Sulfur, Scandium, Titanium, Manganese, Iron, Gallium and Strontium in the Atmosphere of HD144844." Research Notes of the AAS 7, no. 1 (January 16, 2023): 10. http://dx.doi.org/10.3847/2515-5172/acb2cd.
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Abstract Abundances of manganese and gallium are derived in LTE for the B9 Mn P Ga star HD 144844 using the Mn ii lines at 4206.37 and 4259.19 Å and the Ga ii line at 6334.07 Å including hyperfine spliting and nuclear shifts. Both elements are found to be overabundant, about 7–10 times the manganese abundance, depending on the line of Mn ii used, and about 1800 times the solar gallium abundance. The synthesis of three Fe ii lines at 4258.15, 4273.33 and 4296.57 Å yields an abundance of iron marginally above the solar iron abundance. The synthesis of other lines in the range 4200 up to 4300 Å yields information on the abundances of carbon and sulfur (0.05 times the solar abundances), of scandium (5 solar), titanium (1.5 solar), strontium (4.5 solar) and samarium (consistent with a 1.0 solar upper limit).
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Lou, Jun, Li Yang, Haizhen Wang, Laosheng Wu, and Jianming Xu. "Assessing soil bacterial community and dynamics by integrated high-throughput absolute abundance quantification." PeerJ 6 (March 14, 2018): e4514. http://dx.doi.org/10.7717/peerj.4514.
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Microbial ecological studies have been remarkably promoted by the high-throughput sequencing approach with explosive information of taxonomy and relative abundance. However, relative abundance does not reflect the quantity of the microbial community and the inter-sample differences among taxa. In this study, we refined and applied an integrated high-throughput absolute abundance quantification (iHAAQ) method to better characterize soil quantitative bacterial community through combining the relative abundance (by high-throughput sequencing) and total bacterial quantities (by quantitative PCR). The proposed iHAAQ method was validated by an internal reference strain EDL933 and a laboratory strain WG5. Application of the iHAAQ method to a soil phenanthrene biodegradation study showed that for some bacterial taxa, the changes of relative and absolute abundances were coincident, while for others the changes were opposite. With the addition of a microbial activity inhibitor (NaN3), the absolute abundances of soil bacterial taxa, including several dominant genera of Bacillus, Flavobacterium, and Paenibacillus, decreased significantly, but their relative abundances increased after 28 days of incubation. We conclude that the iHAAQ method can offer more comprehensive information to reflect the dynamics of soil bacterial community with both relative and absolute abundances than the relative abundance from high-throughput sequencing alone.
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Evans, Marlene S. "Large-Lake Responses to Declines in the Abundance of a Major Fish Planktivore—the Lake Michigan Example." Canadian Journal of Fisheries and Aquatic Sciences 47, no. 9 (September 1, 1990): 1738–54. http://dx.doi.org/10.1139/f90-198.
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Alewife abundances declined dramatically in southeastern Lake Michigan over 1973–77, several years before the lakewide decline occurred. The regional effects of this decline on adult copepod abundances, zooplankton biomass, and water clarity are examined. In the offshore region, the two largest copepods, Limnocalanus macrurus and Diaptomus sicilis, increased in abundance during the mid-1970's, reflecting the decrease in alewife predation. Limnocalanus macrurus abundances declined in later years, reflecting increased prédation pressures from the increasing bloater population. The small-bodied D. minutus and the medium-bodied D. ashlandi exhibited no apparent response to the decline in alewife abundance. Large-bodied D. oregonensis and small-bodied C. bicuspidatus thomasi declined in abundance. Size-selective fish prédation pressures continued to remain high in the inshore region: increased abundances of yellow perch and rainbow smelt apparently compensated for the alewife decline. Zooplankton biomass, zooplankton mean dry weight, and water clarity apparently were not affected by the decline in alewife abundance in either the inshore or offshore region. The results of this study are evaluated in terms of the lakewide decline in alewife abundance, the summer 1983 dominance of Daphnia pulicaria in offshore waters, the 1983 marked improvement in offshore water clarity, and later changes in summer offshore D. pulicaria populations.
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Roche, Kimberly E., and Sayan Mukherjee. "The accuracy of absolute differential abundance analysis from relative count data." PLOS Computational Biology 18, no. 7 (July 11, 2022): e1010284. http://dx.doi.org/10.1371/journal.pcbi.1010284.
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Concerns have been raised about the use of relative abundance data derived from next generation sequencing as a proxy for absolute abundances. For example, in the differential abundance setting, compositional effects in relative abundance data may give rise to spurious differences (false positives) when considered from the absolute perspective. In practice however, relative abundances are often transformed by renormalization strategies intended to compensate for these effects and the scope of the practical problem remains unclear. We used simulated data to explore the consistency of differential abundance calling on renormalized relative abundances versus absolute abundances and find that, while overall consistency is high, with a median sensitivity (true positive rates) of 0.91 and specificity (1—false positive rates) of 0.89, consistency can be much lower where there is widespread change in the abundance of features across conditions. We confirm these findings on a large number of real data sets drawn from 16S metabarcoding, expression array, bulk RNA-seq, and single-cell RNA-seq experiments, where data sets with the greatest change between experimental conditions are also those with the highest false positive rates. Finally, we evaluate the predictive utility of summary features of relative abundance data themselves. Estimates of sparsity and the prevalence of feature-level change in relative abundance data give reasonable predictions of discrepancy in differential abundance calling in simulated data and can provide useful bounds for worst-case outcomes in real data.
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Whiteman, Noah Kerness, and Patricia G. Parker. "Body Condition and Parasite Load Predict Territory Ownership in the GaláPagos Hawk." Condor 106, no. 4 (November 1, 2004): 915–21. http://dx.doi.org/10.1093/condor/106.4.915.
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Abstract We tested for associations between body condition, territory ownership, and permanent parasite load of Galápagos Hawks (Buteo galapagoensis) on Isla Marchena, Galápagos. Two louse species were collected from most of the 26 hawks sampled: the amblyceran Colpocephalum turbinatum and the ischnoceran Degeeriella regalis. Nonterritorial hawks were in significantly poorer body condition than territorial hawks. Body condition was negatively correlated with the abundance of C. turbinatum. Nonterritorial hawks had significantly higher mean abundances, mean intensities, and median intensities of both louse species than territorial hawks. The amblyceran's mean abundance and intensity were significantly higher than the ischnoceran's. Abundances of the two lice were positively related when the population size of C. turbinatum was <100 individuals, and negatively related when >100 individuals. Parasite load and body condition both predicted territory ownership well. La Condición Corporal y la Carga Parasitaria Predicen la Posesión de Territorios en Buteo galapagoensis Resumen. Probamos la relación entre la condición corporal, la posesión de territorios y la carga parasitaria permanente en el Gavilán de Galápagos (Buteo galapagoensis) en la Isla Marchena, Galápagos. En la mayoría de los 26 gavilanes muestreados se colectaron dos especies de piojo: el ambliceránido Colpocephalum turbinatum y el ischnoceránido Degeeriella regalis. Los gavilanes no territoriales se encontraron en condiciones corporales significativamente peores que los gavilanes territoriales. Encontramos una correlación negativa significativa entre la condición corporal y la abundancia de C. turbinatum. Los gavilanes no territoriales tuvieron significativamente mayor abundancia, intensidad media e intensidad mediana de las dos especies de piojo que los gavilanes territoriales. La abundancia promedio y la intensidad de los ambliceránidos fueron significativamente mayores que las de los ischnoceránidos. Las abundancias de las dos especies de piojo estuvieron positivamente correlacionadas cuando el tamaño poblacional de C. turbinatum fue <100 individuos y negativamente correlacionadas cuándo fue >100 individuos. Tanto la carga parasitaria como la condición corporal predijeron bien la posesión de territorios.
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Lemoine, Martin, Jean Audouze, Lotfi Ben Jaffel, Paul Feldman, Roger Ferlet, Guillaume Hébrard, Edward B. Jenkins, et al. "Deuterium abundances." New Astronomy 4, no. 4 (July 1999): 231–43. http://dx.doi.org/10.1016/s1384-1076(99)00017-2.
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Laird, J. B. "Abundances in field dwarf stars. III - Magnesium abundances." Astrophysical Journal 303 (April 1986): 718. http://dx.doi.org/10.1086/164119.
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Giridhar, Sunetra. "Abundance Analysis of Alpha Ursae Minoris." International Astronomical Union Colloquium 82 (1985): 100–103. http://dx.doi.org/10.1017/s0252921100109224.
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AbstractWe have derived atmospheric abundances of the bright Cepheid a UMi in order to study the abundance anomalies in different elements. The atmospheric abundance of C, 0, Fe-peak elements Ca, Sc, Ti, Cr, Fe and heavier s-process elements Y, Ba, Ce and Sm have been derived using the method of spectrum synthesis. The abundance of carbon is derived using the C I lines in 4700A region, whereas for oxygen, the forbidden line at 6300.311A is employed. Abundances of the Fe-peak elements and s-process elements are obtained by synthesizing selected portions in the wavelength range 4330A - 4650A. The estimates of C/0 derived from the present investigation are compared with other Cepheids of similar period. The evolutionary status of a UMi is discussed in the light of these derived abundances.
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Heiter, U., and R. E. Luck. "Abundance Analysis of Planetary Host Stars. I. Differential Iron Abundances." Astronomical Journal 126, no. 4 (October 2003): 2015–36. http://dx.doi.org/10.1086/378366.
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Smiljanic, R., P. Donati, A. Bragaglia, B. Lemasle, and D. Romano. "Deep secrets of intermediate-mass giants and supergiants." Astronomy & Astrophysics 616 (August 2018): A112. http://dx.doi.org/10.1051/0004-6361/201832877.
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Context. Recent observational results have demonstrated an increase in the surface Na abundance that correlates with stellar mass for red giants between 2 and 3 M⊙. This trend supports evolutionary mixing processes as the explanation for Na overabundances seen in some red giants. In this same mass range, the surface Al abundance was shown to be constant. Aims. Our main aim was to extend the investigation of the Na and Al surface abundances to giants more massive than 3 M⊙. We sought to establish accurately whether the Na abundances keep increasing with stellar mass or a plateau is reached. In addition, we investigated whether mixing can affect the surface abundance of Al in giants more massive than 3 M⊙. Methods. We obtained new high-resolution spectra of 20 giants in the field of 10 open clusters; 17 of these stars were found to be members of 9 clusters. The giants have masses between 2.5 M⊙ and 5.6 M⊙. A model atmosphere analysis was performed and abundances of up to 22 elements were derived using equivalent widths. Additionally, abundances of C, N, and O were determined using spectrum synthesis. The abundances of Na and Al were corrected for non-local thermodynamic equilibrium (non-LTE) effects. Moreover, to extend the mass range of our sample, we collected from the literature high-quality C, N, O, and Na abundances of 32 Galactic Cepheids with accurate masses in the range between 3 M⊙ and 14 M⊙. Results. The surface abundances of C, N, O, Na, and Al were compared to predictions of stellar evolution models with and without the inclusion of rotation-induced mixing. The surface abundances of most giants and Cepheids of the sample can be explained by models without rotation. For giants above Ȉ2.5 M⊙, the Na abundances reach a plateau level of about [Na/Fe] ~ 0.20–0.25 dex (in non-LTE). This is true for both Cepheids and giants in open clusters. Regarding Al, the non-LTE [Al/Fe] ratios are mostly close to solar and suggest that Al is not affected by the first dredge-up up to ~5.0 M⊙. Our results support previous works that found models with rotation to overestimate the mixing effects in intermediate-mass stars.
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Matsushita, Kyoko, Yasushi Ikebe, Alexis Finoguenov, and Hans Böhringer. "XMM Observations of Abundances in the Intracluster Medium." Symposium - International Astronomical Union 217 (2004): 102–7. http://dx.doi.org/10.1017/s0074180900197220.
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Based on XMM-Newton observations of M 87 and the Centaurus cluster, abundance profiles of various elements of the intracluster medium (ICM) are derived. The abundances of Si and Fe show strong decreasing gradients. In contrast, the O and Mg abundances are about half of the Si abundance at the center.From the gas mass to stellar mass ratio and the comparison of Mg abundance with the stellar metallicity, the stellar mass loss from the central galaxies is indicated to be the main source of gas in the very central region of the clusters.The observed O, Si and Fe abundance pattern determines the contribution of supernova (SN) Ia and SN II, with the abundance pattern of ejecta of SN Ia. Most of the Si and Fe of the ICM in the central region of the clusters comes from SN Ia which occured in the central galaxies. In order to explain the observed O/Si ratio of a half solar, SN Ia products should have similar abundances of Si and Fe, which may reflect dimmer SN Ia observed in old stellar systems.
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De Freitas Pacheco, J. A. "O, S, Ar from Planetary Nebulae Data and the Chemical Evolution of the Galactic Disk." Symposium - International Astronomical Union 155 (1993): 576. http://dx.doi.org/10.1017/s007418090017250x.
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The O, S, Ar abundances for a sample of 122 planetary nebulae (merging LNA data and those by Köppen, Acker and Stenholm 1991) were analysed. Average abundances were calculated for progenitors having different metallicities (ages). Our study suggests that type I planetaries, whose progenitors are not older than 1–2 Gyr, have average oxygen abundances 0.2 dex lower than the solar value. This agrees with O-abundance determinations in HII regions, intermediate mass supergiants and B stars in young associations. S and Ar show a different behaviour. We suggest that such a paucity of O in the ISM is produced by recent infalling gas from the halo, having abundance ratios similar to those expected from type Ia supernovae.
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Bowler, Diana E., Peter Haase, Christian Hof, Ingrid Kröncke, Léon Baert, Wouter Dekoninck, Sami Domisch, et al. "Cross-taxa generalities in the relationship between population abundance and ambient temperatures." Proceedings of the Royal Society B: Biological Sciences 284, no. 1863 (September 20, 2017): 20170870. http://dx.doi.org/10.1098/rspb.2017.0870.
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Identifying patterns in the effects of temperature on species' population abundances could help develop a general framework for predicting the consequences of climate change across different communities and realms. We used long-term population time series data from terrestrial, freshwater, and marine species communities within central Europe to compare the effects of temperature on abundance across a broad range of taxonomic groups. We asked whether there was an average relationship between temperatures in different seasons and annual abundances of species in a community, and whether species attributes (temperature range of distribution, range size, habitat breadth, dispersal ability, body size, and lifespan) explained interspecific variation in the relationship between temperature and abundance. We found that, on average, warmer winter temperatures were associated with greater abundances in terrestrial communities (ground beetles, spiders, and birds) but not always in aquatic communities (freshwater and marine invertebrates and fish). The abundances of species with large geographical ranges, larger body sizes, and longer lifespans tended to be less related to temperature. Our results suggest that climate change may have, in general, positive effects on species’ abundances within many terrestrial communities in central Europe while the effects are less predictable in aquatic communities.
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Tanaka, S., S. Kitamoto, T. Suzuki, K. Torii, M. F. Corcoran, and W. Waldron. "Chemical Abundances of Early Type Stars." Symposium - International Astronomical Union 188 (1998): 224–25. http://dx.doi.org/10.1017/s007418090011486x.
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X-rays from early-type stars are emitted by the corona or the stellar wind. The materials in the surface layer of early-type stars are not contaminated by nuclear reactions in the stellar inside. Therefore, abundance study of the early-type stars provides us an information of the abundances of the original gas. However, the X-ray observations indicate low-metallicity, which is about 0.3 times of cosmic abundances. This fact raises the problem on the cosmic abundances.
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Mashonkina, L., T. Ryabchikova, S. Alexeeva, T. Sitnova, and O. Zatsarinny. "Chemical diversity among A–B stars with low rotational velocities: non-LTE abundance analysis." Monthly Notices of the Royal Astronomical Society 499, no. 3 (October 9, 2020): 3706–19. http://dx.doi.org/10.1093/mnras/staa3099.
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ABSTRACT We present accurate element abundance patterns based on the non-local thermodynamic equilibrium (non-LTE, NLTE) line formation for 14 chemical elements from He to Nd for a sample of nine A9 to B3-type stars with well-determined atmospheric parameters and low rotational velocities. We constructed new model atom of Zr ii–iii and updated model atoms for Sr ii and Ba ii by implementing the photoionization cross-sections from calculations with the Dirac B-spline R-matrix method. The NLTE abundances of He to Fe in the stars HD 17081, HD 32115, HD 160762, and HD 209459 are found to be consistent with the solar abundances, and HD 73666 being a Blue Straggler does not reveal deviations from chemical composition of the Praesepe cluster. Three of these stars with an effective temperature of lower than 10 500 K have supersolar abundances of Sr, Zr, Ba, and Nd, and our results suggest the presence of a positive correlation between stellar effective temperature and abundance. For each star, enhancement of Ba is higher than that for any other heavy element. We propose that the solar Ba abundance is not representative of the galactic Ba abundance at modern epoch. The status of HD 145788 was not clarified: This star has solar abundances of C to Si and enhancements of Sr to Ba similar to that for superficially normal stars of similar temperature, while Ca, Ti, and Fe are overabundant. The NLTE abundances of Vega support its status of a mild λ Bootis star.
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Soneson, Charlotte, Michael I. Love, Rob Patro, Shobbir Hussain, Dheeraj Malhotra, and Mark D. Robinson. "A junction coverage compatibility score to quantify the reliability of transcript abundance estimates and annotation catalogs." Life Science Alliance 2, no. 1 (January 17, 2019): e201800175. http://dx.doi.org/10.26508/lsa.201800175.
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Most methods for statistical analysis of RNA-seq data take a matrix of abundance estimates for some type of genomic features as their input, and consequently the quality of any obtained results is directly dependent on the quality of these abundances. Here, we present the junction coverage compatibility score, which provides a way to evaluate the reliability of transcript-level abundance estimates and the accuracy of transcript annotation catalogs. It works by comparing the observed number of reads spanning each annotated splice junction in a genomic region to the predicted number of junction-spanning reads, inferred from the estimated transcript abundances and the genomic coordinates of the corresponding annotated transcripts. We show that although most genes show good agreement between the observed and predicted junction coverages, there is a small set of genes that do not. Genes with poor agreement are found regardless of the method used to estimate transcript abundances, and the corresponding transcript abundances should be treated with care in any downstream analyses.
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Rodríguez, Mónica, and Gloria Delgado-Inglada. "Chlorine and sulfur in nearby planetary nebulae and H II regions." Proceedings of the International Astronomical Union 7, S283 (July 2011): 488–89. http://dx.doi.org/10.1017/s1743921312012069.
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AbstractWe derive the chlorine abundances in a sample of nearby planetary nebulae (PNe) and H II regions that have some of the best available spectra. We use a nearly homogeneous procedure to derive the abundance in each object and find that the Cl/H abundance ratio shows similar values in H II regions and PNe. This supports our previous interpretation that the underabundance we found for oxygen in the H II regions is due to the depletion of their oxygen atoms into organic refractory dust components. For other elements, the bias introduced by ionization correction factors in their derived abundances can be very important, as we illustrate here for sulfur using photoionization models. Even for low-ionization PNe, the derived sulfur abundances can be lower than the real ones by up to 0.3 dex, and the differences found with the abundances derived for H II regions that have similar S/H can reach 0.4 dex.
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Walton, N. A., M. J. Barlow, and R. E. S. Clegg. "Chemical Abundances in Galactic Bulge Pn." Symposium - International Astronomical Union 155 (1993): 581. http://dx.doi.org/10.1017/s0074180900172559.
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We present abundance determinations, in particular of carbon, and C/O ratios, for 11 Galactic bulge planetary nebulae (PN) based on our low resolution UV data from IUE observations and optical spectrophotometry from the Anglo-Australian Telescope. We compare the observed abundances with those predicted by dredge-up theory for the high metallicity Galactic bulge. The sample abundances are also contrasted with the abundances found for PN in the Galactic disk. The mean C/O ratio for the bulge PN is significantly lower than that found for Galactic disk PN. Further, we present an abundance analysis of the very metal-poor bulge PN M2-29. From an analysis of the differential extinction found from the observed ratios of the He ii 1640,4686Å lines, we find that the ultraviolet reddening law towards the bulge is steeper than in the solar neighbourhood.
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Wang, Zhicheng, Lina Zhuang, Lianru Gao, Andrea Marinoni, Bing Zhang, and Michael K. Ng. "Hyperspectral Nonlinear Unmixing by Using Plug-and-Play Prior for Abundance Maps." Remote Sensing 12, no. 24 (December 16, 2020): 4117. http://dx.doi.org/10.3390/rs12244117.
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Spectral unmixing (SU) aims at decomposing the mixed pixel into basic components, called endmembers with corresponding abundance fractions. Linear mixing model (LMM) and nonlinear mixing models (NLMMs) are two main classes to solve the SU. This paper proposes a new nonlinear unmixing method base on general bilinear model, which is one of the NLMMs. Since retrieving the endmembers’ abundances represents an ill-posed inverse problem, prior knowledge of abundances has been investigated by conceiving regularizations techniques (e.g., sparsity, total variation, group sparsity, and low rankness), so to enhance the ability to restrict the solution space and thus to achieve reliable estimates. All the regularizations mentioned above can be interpreted as denoising of abundance maps. In this paper, instead of investing effort in designing more powerful regularizations of abundances, we use plug-and-play prior technique, that is to use directly a state-of-the-art denoiser, which is conceived to exploit the spatial correlation of abundance maps and nonlinear interaction maps. The numerical results in simulated data and real hyperspectral dataset show that the proposed method can improve the estimation of abundances dramatically compared with state-of-the-art nonlinear unmixing methods.
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Hinch, Scott G., Keith M. Somers, and Nicholas C. Coliins. "Spatial Autocorrelation and Assessment of Habitat–Abundance Relationships in Littoral Zone Fish." Canadian Journal of Fisheries and Aquatic Sciences 51, no. 3 (March 1, 1994): 701–12. http://dx.doi.org/10.1139/f94-070.
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Spatial autocorrelation, wherein intersite similarity is correlated with distance between sites, is a characteristic of most ecological studies spanning a large environmental range. If data are spatially autocorrelated, classical statistical techniques provide biased estimates of relationships between species attributes and environmental variables. We examined abundances of seven littoral fishes in 25 lakes that varied substantially in morphometry, chemistry, and elevation across central Ontario. Weak correlations were observed between abundances of particular species and environmental variables before correcting for spatial autocorrelation, and we hypothesized that correlations reflected species' habitat preferences. However, spatial autocorrelation existed in the abiotic and fish abundance datasets. Once large-scale geographic patterns (spatial autocorrelation) were removed using partial Mantel tests, correlations changed within and between datasets. A strong relationship emerged between abundances and lake elevation. By comparing patterns within geographically corrected data with those without correction, we identified particular species that exhibited spatially autocorrelated abundances. The geographic direction of spatial autocorrelation provided additional insights into environmental factors also correlating with species abundance. We recommend that ecologists examine both geographically corrected and noncorrected data when developing hypotheses to explain regional variation in species abundance.
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Mishenina, T. V., I. A. Usenko, A. Yu Kniazev, and V. V. Kovtyukh. "TYC5594-576-1: R-PROCESS ENRICHMENT METAL-POOR STAR." Odessa Astronomical Publications 34 (December 3, 2021): 48–52. http://dx.doi.org/10.18524/1810-4215.2021.34.244291.
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Atmospheric parameters and elemental abundances of metal-poor Population II star TYC5594-576-1 ([Fe/H] = –2.8) have been studied, including the elements of neutron (n-) capture processes, as an important part of the enrichment sources of early Galaxy. Na, Mg, Al, Co, Sr, Y, Zr, Mo, Ba, La, Ce, Pr, Sm, Eu, Gd, Dy, Os, and Th abundances were determined using the synthetic spectrum method, taken into account the hyperfine structure (HFS) for the Ba II, La II and Eu II lines. The abundances of Si, Ca, Sc, N were determined based on the equivalent widths of their lines. The carbon abundance was obtained by the molecular synthesis fitting for the CH region of 4300-4330 ÅÅ. For the abundances determinations of C, Na, Mg, Al, Ba, and Th the NLTE corrections have been applied.We have determined the abundances of several n- capture elements for the first time and found that the behaviour of these elements abundances shows a significant trend with increasing atomic number. The elements ratios of [Eu/Fe] = 1.85, [Ba/Eu] = –1.24, [Sr/Ba] = –1.04 confirm the status of TYC5594-576-1 as a r-process enrichment star, with lower strontium [Sr/Fe] = –0.33 and higher thorium [Th/Fe] = 1.28 abundances. The obtained europium and thorium excesses testifies to the early enrichment of the Galaxy by the r-process elements as a result of the merger of neutron stars or black holes. The carbon abundance confirms the effect of canonical additional mixing in this star.
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Kaiser, B. C., J. C. Clemens, S. Blouin, P. Dufour, R. J. Hegedus, J. S. Reding, and A. Bédard. "Lithium pollution of a white dwarf records the accretion of an extrasolar planetesimal." Science 371, no. 6525 (December 17, 2020): 168–72. http://dx.doi.org/10.1126/science.abd1714.
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Tidal disruption and subsequent accretion of planetesimals by white dwarfs can reveal the elemental abundances of rocky bodies in exoplanetary systems. Those abundances provide information on the composition of the nebula from which the systems formed, which is analogous to how meteorite abundances inform our understanding of the early Solar System. We report the detection of lithium, sodium, potassium, and calcium in the atmosphere of the white dwarf Gaia DR2 4353607450860305024, which we ascribe to the accretion of a planetesimal. Using model atmospheres, we determine abundance ratios of these elements, and, with the exception of lithium, they are consistent with meteoritic values in the Solar System. We compare the measured lithium abundance with measurements in old stars and with expectations from Big Bang nucleosynthesis.
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Ishigaki, Miho N., Wako Aoki, and Masashi Chiba. "Chemical differences and similarities among the kinematically selected thick disk, inner halo and outer halo stars." Proceedings of the International Astronomical Union 9, S298 (May 2013): 71–76. http://dx.doi.org/10.1017/s1743921313006224.
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AbstractChemical diversity among metal-poor stars in the old stellar components in the Milky Way (MW), namely the thick disk and stellar halo, provides clues to understanding the early chemodynamical evolution of our Galaxy. We present our results on a homogeneous chemical abundance analysis for nearby metal-poor stars likely belonging to the MW thick disk, inner and outer stellar halos. Abundances of alpha, sodium, iron-peak and neutron-capture elements in the sample stars have been estimated using high-resolution (R 50000) spectra obtained with the High Dispersion Spectrograph mounted on the Subaru Telescope. The derived abundances are used to examine differences and similarities in elemental abundance ratios among the kinematically defined thick disk, inner and outer halo subsamples in the metallicity range of −3.3 < [Fe/H] < −0.5. We show that, in the metallicity range of [Fe/H] < −2, the three subsamples are similar in most of the elemental abundances. On the other hand, in the higher metallicities, particularly in [Fe/H] > −1.5, the thick disk and the inner/outer halo subsamples show systematically different abundance ratios for some elements including alpha, sodium, zinc and europium. A modest difference in the sodium and zinc abundances between the inner- and outer halo subsamples is also identified. The observed distinct abundances of some elements among the three subsamples implies that their constituent stars originally formed in progenitor systems that have experienced different star formation and chemical enrichment histories.
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Yong, D., A. I. Karakas, D. L. Lambert, A. Chieffi, and M. Limongi. "Insights into the s-process and r-process as revealed by globular clusters." Proceedings of the International Astronomical Union 5, S265 (August 2009): 54–56. http://dx.doi.org/10.1017/s1743921310000153.
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AbstractWe present abundance measurements for a large number of neutron-capture elements in giant stars of the globular clusters M4, M5, and M13. The relative abundance ratios differ between all three clusters. For all clusters, we find that the mean abundances for the elements from Ba to Hf can be well explained by scaled versions of the solar s- and r-process abundances, albeit with different mixtures of s- and r-process material for each clusters.
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Tautvaišienė, G., A. Drazdauskas, A. Bragaglia, S. L. Martell, E. Pancino, C. Lardo, Š. Mikolaitis, et al. "Gaia-ESO Survey: Detailed elemental abundances in red giants of the peculiar globular cluster NGC 1851." Astronomy & Astrophysics 658 (February 2022): A80. http://dx.doi.org/10.1051/0004-6361/202142234.
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Context. NGC 1851 is one of several globular clusters for which multiple stellar populations of the subgiant branch have been clearly identified and a difference in metallicity detected. A crucial piece of information on the formation history of this cluster can be provided by the sum of A(C+N+O) abundances. However, these values have lacked a general consensus thus far. The separation of the subgiant branch can be based on age and/or A(C+N+O) abundance differences. Aims. Our main aim was to determine carbon, nitrogen, and oxygen abundances for evolved giants in the globular cluster NGC 1851 in order to check whether or not the double populations of stars are coeval. Methods. High-resolution spectra, observed with the FLAMES-UVES spectrograph on the ESO VLT telescope, were analysed using a differential model atmosphere method. Abundances of carbon were derived using spectral synthesis of the C2 band heads at 5135 and 5635.5 Å. The wavelength interval 6470−6490 Å, with CN features, was analysed to determine nitrogen abundances. Oxygen abundances were determined from the [O I] line at 6300 Å. Abundances of other chemical elements were determined from equivalent widths or spectral syntheses of unblended spectral lines. Results. We provide abundances of up to 29 chemical elements for a sample of 45 giants in NGC 1851. The investigated stars can be separated into two populations with a difference of 0.07 dex in the mean metallicity, 0.3 dex in the mean C/N, and 0.35 dex in the mean s-process dominated element-to-iron abundance ratios [s/Fe]. No significant difference was determined in the mean values of A(C+N+O) as well as in abundance to iron ratios of carbon, α- and iron-peak-elements, and of europium. Conclusions. As the averaged A(C+N+O) values between the two populations do not differ, additional evidence is given that NGC 1851 is composed of two clusters, the metal-rich cluster being by about 0.6 Gyr older than the metal-poor one. A global overview of NGC 1851 properties and the detailed abundances of chemical elements favour its formation in a dwarf spheroidal galaxy that was accreted by the Milky Way.
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Monier, Richard. "The Abundances of Helium, Magnesium and Phosphorus in the Atmosphere of HD144844." Research Notes of the AAS 7, no. 1 (January 10, 2023): 4. http://dx.doi.org/10.3847/2515-5172/acb145.
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Abstract Abundances of helium and magnesium are derived in LTE for the B9 Mn P Ga star HD 144844 using the group of He i lines near 4470.40 Å and the Mg ii triplet at 4481.22 Å. Both elements are found to be very underabundant, about 2% of the solar helium and magnesium abundances. The profile of the Mg ii line at 4481.22 Å clearly shows two components and confirms that this star is a double-lined spectroscopic binary. The synthesis of three P ii lines at 6024.18, 6034.04 and 6043.88 Å yields phosphorus abundances from 150 up to 200 times the solar phosphorus abundance. A NLTE synthesis is necessary to derive more accurate abundances.
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Ramírez, S. V., K. Sellgren, D. M. Terndrup, J. S. Carr, S. Balachandran, and R. D. Blum. "Iron Abundances in AGB Stars and M Supergiant Stars at the Galactic Center." Symposium - International Astronomical Union 191 (1999): 529–34. http://dx.doi.org/10.1017/s0074180900203513.
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We are measuring Fe abundances of cool, luminous stars within 30 pc of the center of the Milky Way. Our sample contains both AGB stars and M supergiants. Low-resolution (λ/Δλ = 500) H and K band spectra are used to estimate temperatures and gravities. Stellar Fe abundances are determined from high-resolution (λ/Δλ = 40 000) K band spectra obtained on the IRTF using CSHELL. We find that Fe abundances of stars in the Galactic Center are consistent with the solar Fe abundance.
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Skillman, Evan D. "Uncertainties in nebular helium abundances." Proceedings of the International Astronomical Union 5, S268 (November 2009): 113–18. http://dx.doi.org/10.1017/s1743921310003947.
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AbstractEfforts to determine the primordial helium abundance via observations of metal poor HII regions have been limited by significant uncertainties. Because of a degeneracy between the solutions for density and temperature, the precision of the helium abundance determinations is limited. Spectra from the literature are used to show the effects of new atomic data and to demonstrate the challenges of determining precise He abundances. Several suggestions are made for meeting these challenges.
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Coulombe-Pontbriand, M., and Michel Lapointe. "Landscape controls on boulder-rich, winter habitat availability and their effects on Atlantic salmon (Salmo salar) parr abundance in two fifth-order mountain streams." Canadian Journal of Fisheries and Aquatic Sciences 61, no. 4 (April 1, 2004): 648–58. http://dx.doi.org/10.1139/f04-023.
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We test the effect at river reach and segment scales of landscape controls on the distribution of Atlantic salmon (Salmo salar) parr densities, as well as associated variations in boulder (diameter ≥ 256 mm) abundance and potential overwintering habitat. This study encompasses data from 45 km of fifth-order mainstem channels along two neighbouring river catchments in the Gaspé region, Québec. At both scales, winter habitat availability was correlated with boulder availability. At the river segment scale (15 km), parr densities significantly correlated (P < 0.05) with boulder availability along the Bonaventure River, which presented significant intersegment variations in boulder abundances. In contrast, segment-scale boulder and parr abundances were uniformly low along the Petite Cascapédia River. At the reach scale (600 m), positive but less strongly significant boulder parr abundance correlations were observed in both the Bonaventure and Petite Cascapédia rivers. Spatial variations in boulder abundances in these systems reflected variations in the degree of channel to valley walls coupling and imposed channel formative shear stresses. In similarly boulder-poor segments with comparable fry abundances, parr abundances were significantly greater along the Bonaventure than the Petite Cascapédia River, possibly because of the presence in the former system of nearby boulder-rich refugia segments.
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Li, Yanbing, E. B. da Silva, Jingchun Li, and L. Kung. "Effect of Homo-Fermentative Lactic Acid Bacteria Inoculants on Fermentation Characteristics and Bacterial and Fungal Communities in Alfalfa Silage." Fermentation 8, no. 11 (November 10, 2022): 621. http://dx.doi.org/10.3390/fermentation8110621.
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We evaluated the effects of a homo-fermentative lactic acid bacteria (homo-LAB) inoculant on the fermentation and microbial communities of alfalfa ensiled at two dry matter (DM) contents of 38 and 46% DM. At both DMs, alfalfa was treated or not with an inoculant containing Pediococcus acidilactici, Enterococcus faecium and Lactobacillus plantarum at a targeted application rate of 165,000 cfu/g of fresh weight and stored for 3, 30 and 60 days. Treatment with the inoculant resulted in a lower drop in pH and, in general, higher lactic acid and lower acetic acid when applied to medium DM silage. For the four most abundant microbial genera, increased abundances of Bacteroides and Lactobacillus (p < 0.05), as well as decreased abundances of Muribaculaceae were observed in high DM and inoculated silages. The abundance of Prevotellaceae-UCG-001 was lower in medium DM control silages than in high DM control silages. Inoculation and DM affected abundances of Vishniacozyma (p < 0.05). Increased abundances of Vishniacozyma, as well as decreased abundances of Leucosporidium were observed in medium DM-inoculated silages. Changes in the relative abundance (RA) of the main populations of bacteria and yeasts did explain the fermentation and nutrition differences among treatments.
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Rennó, C., B. Barbuy, T. C. Moura, and M. Trevisan. "Abundances from integrated spectra of 47 Tucanae (NGC 104)." Monthly Notices of the Royal Astronomical Society 498, no. 4 (September 8, 2020): 5834–54. http://dx.doi.org/10.1093/mnras/staa2697.
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ABSTRACT 47 Tucanae is among the most studied and observed globular clusters, given its proximity. The aim of this work is to study in detail the integrated spectrum of 47 Tucanae, as a template, in order to have a list of reliable lines that are validated for a moderate spectral resolution case. The spectrum of 47 Tucanae is reproduced by computing synthetic spectra, taking into account individual element abundances. The results are compared with other methods. We reproduce the integrated spectrum in the range 4500–9000 Å and derive abundances from individual lines of Na, Mg, Al, Si, Ca, Ti, Ba, and Eu. We report a list of lines that are suitable for abundance derivation. Adopting these abundances, we are able to fit the well-known triplets of Mg i and Ca ii. Finally, the effect of multiple stellar populations through enhanced Na abundances are tested. Element abundances derived are compatible with previous literature abundances, from different methods. The method applied here to build integrated synthetic spectra can be used to derive abundances from observed integrated spectra of distant and faint clusters, that are usually observed at low or moderate spectral resolution.
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Gao, Lin, Rui Wang, Jiaming Gao, Fangming Li, Guanghua Huang, Guang Huo, Zhiyu Liu, Wei Tang, and Guoming Shen. "Analysis of the structure of bacterial and fungal communities in disease suppressive and disease conducive tobacco-planting soils in China." Soil Research 58, no. 1 (2020): 35. http://dx.doi.org/10.1071/sr19204.
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To clarify the differences between microbial communities resident in disease suppressive soil (DSS) and disease conducive soil (DCS) in tobacco cultivation, representative soil samples were collected from tobacco plantations in Shengjiaba, China, and the structure and diversity of the resident bacterial and fungal communities were analysed using high-throughput sequencing technology. Our results showed a greater number of operational taxonomic units associated with bacteria and fungi in DSS than in DCS. At the phylum level, abundances of Chloroflexi, Saccharibacteria, Firmicutes, and Planctomycetes in DSS were lower than in DCS, but abundance of Gemmatimonadetes was significantly higher. Abundances of Zygomycota and Chytridiomycota were higher in DSS than DCS, but abundance of Rozellomycota was significantly lower. At the genus level, abundances of 18 bacterial and nine fungal genera varied significantly between DSS and DCS. Relative abundances of Acidothermus, Microbacterium, Curtobacterium, and Colletotrichum were higher in DCS than DSS. The Shannon and Chao1 indices of DSS microbial communities were higher than those of DCS communities. High microbial diversity reduces the incidence of soil-borne diseases in tobacco plantations and promotes the formation of DSSs.
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Tan, Kefeng, and Gang Zhao. "Two distinct halo populations in the solar neighborhood: evidence from stellar abundance of beryllium." Proceedings of the International Astronomical Union 9, S298 (May 2013): 83–85. http://dx.doi.org/10.1017/s1743921313006248.
Full textAbstract:
AbstractIt is now generally believed that the Galaxy was formed through hierarchical merging, which means that different components of the Galaxy may have experienced different chemical evolution histories. Since alpha elements are mainly produced by core collapse supernovae, they are closely associated with the star formation history of the Galaxy. In this regard, Galactic components with different alpha elemental abundance patterns may show different behaviors in beryllium abundances since the production of beryllium is correlated with the cosmic rays and thus the supernovae. A recent study by Nissen & Schuster (2010) has revealed the existence of two distinct halo populations in the solar neighborhood based on the alpha elemental abundances and kinematics of 94 dwarf stars. We determined beryllium abundances for some of these stars and find systematic differences in beryllium abundances between these two halo populations. Our results consolidate the conclusion of two distinct halo populations in the solar neighborhood. Our results also show that beryllium abundance is a very good indicator of star formation rate, and could be used to trace the substructures of the Galactic halo.