- ID:
- ivo://CDS.VizieR/J/ApJ/758/59
- Title:
- Nickel isotopes in meteorites
- Short Name:
- J/ApJ/758/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new, mass-independent, Ni isotope data for a range of bulk chondritic meteorites. The data are reported as {epsilon}g^60^Ni_58/61_, {x3b5}^62^Ni_58/61_, and {epsilon}g^64^Ni_58/61_, or the parts per ten thousand deviations from a terrestrial reference, the NIST SRM 986 standard, of the ^58^Ni/^61^Ni internally normalized ^60^Ni/^61^Ni, ^62^Ni/^61^Ni, and ^64^Ni/^61^Ni ratios. The chondrites show a range of 0.15, 0.29, and 0.84 in {epsilon}g^60^Ni_58/61_, {x3b5}^62^Ni_58/61_, and {epsilon}g^64^Ni_58/61_ relative to a typical sample precision of 0.03, 0.05, and 0.08 (2 s.e.), respectively. The carbonaceous chondrites show the largest positive anomalies, enstatite chondrites have approximately terrestrial ratios, though only EH match Earth's composition within uncertainty, and ordinary chondrites show negative anomalies. The meteorite data show a strong positive correlation between {epsilon}g^62^Ni_58/61_ and {x3b5}^64^Ni_58/61_, an extrapolation of which is within the error of the average of previous measurements of calcium-, aluminium-rich inclusions. Moreover, the slope of this bulk meteorite array is 3.003+/-0.166 which is within the error of that expected for an anomaly solely on ^58^Ni. We also determined to high precision (~10 ppm per AMU) the mass-dependent fractionation of two meteorite samples which span the range of {epsilon}g^62^Ni_58/61_ and {x3b5}^64^Ni_58/61_. These analyses show that "absolute" ratios of ^58^Ni/^61^Ni vary between these two samples whereas those of ^62^Ni/^61^Ni and ^64^Ni/^61^Ni do not. Thus, Ni isotopic differences seem most likely explained by variability in the neutron-poor ^58^Ni, and not correlated anomalies in the neutron-rich isotopes, ^62^Ni and ^64^Ni. This contrasts with previous inferences from mass-independent measurements of Ni and other transition elements which invoked variable contributions of a neutron-rich component. We have examined different nucleosynthetic environments to determine the possible source of the anomalous material responsible for the isotopic variations observed in Ni and other transition elements within bulk samples.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/827/74
- Title:
- [NII]/H{alpha} ratio in galaxies with KMOS^3D^
- Short Name:
- J/ApJ/827/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the [NII]/H{alpha} ratio as a probe of gas-phase oxygen abundance for a sample of 419 star-forming galaxies at z=0.6-2.7 from the KMOS^3D^ near-IR multi-integral field unit (IFU) survey. The mass-metallicity relation (MZR) is determined consistently with the same sample selection, metallicity tracer, and methodology over the wide redshift range probed by the survey. We find good agreement with long-slit surveys in the literature, except for the low-mass slope of the relation at z~2.3, where this sample is less biased than previous samples based on optical spectroscopic redshifts. In this regime we measure a steeper slope than some literature results. Excluding the contribution from active galactic nuclei from the MZR reduces sensitivity at the high-mass end, but produces otherwise consistent results. There is no significant dependence of the [NII]/H{alpha} ratio on star formation rate at fixed redshift and stellar mass. The IFU data allow spatially resolved measurements of [NII]/H{alpha}, from which we can infer abundance gradients for 180 galaxies, thus tripling the current sample in the literature. The observed gradients are on average flat, with only 15 gradients statistically offset from zero at >3{sigma}. We have modeled the effect of beam smearing, assuming a smooth intrinsic radial gradient and known seeing, inclination, and effective radius for each galaxy. Our seeing-limited observations can recover up to 70% of the intrinsic gradient for the largest, face-on disks, but only 30% for the smaller, more inclined galaxies. We do not find significant trends between observed or corrected gradients and any stellar population, dynamical, or structural galaxy parameters, mostly in agreement with existing studies with much smaller sample sizes. In cosmological simulations, strong feedback is generally required to produce flat gradients at high redshift.
- ID:
- ivo://CDS.VizieR/J/ApJS/211/20
- Title:
- NiI transition probability measurements
- Short Name:
- J/ApJS/211/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Atomic transition probability measurements for 371 NiI lines in the UV through near-IR are reported. Branching fractions from data recorded using a Fourier transform spectrometer and a new echelle spectrograph are combined with published radiative lifetimes to determine these transition probabilities. Generally good agreement is found in comparisons to previously reported NiI transition probability measurements. Use of the new echelle spectrograph, independent radiometric calibration methods, and independent data analysis routines enable a reduction of systematic errors and overall improvement in transition probability uncertainty over previous measurements. The new NiI data are applied to high-resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to derive new, more accurate Ni abundances. Lines covering a wide range of wavelength and excitation potential are used to search for non-LTE effects.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A177
- Title:
- 56Ni masses in supernovae
- Short Name:
- J/A+A/641/A177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass of synthesised radioactive material is an important power source for all supernova (SN) types. In addition, the difference of ^56^Ni yields statistics are relevant to constrain progenitor paths and explosion mechanisms. Here, we re-estimate the nucleosynthetic yields of ^56^Ni for a well-observed and well-defined sample of stripped-envelope SNe (SE-SNe) in a uniform manner. This allows us to investigate whether the observed hydrogen-rich-stripped-envelope (SN II-SE SN) ^56^Ni separation is due to real differences between these SN types or because of systematic errors in the estimation methods. We compiled a sample of well-observed SE-SNe and measured ^56^Ni masses through three different methods proposed in the literature: first, the classic "Arnett rule"; second the more recent prescription of Khatami & Kasen (2019ApJ...878...56K) and third using the tail luminosity to provide lower limit ^56^Ni masses. These SE-SN distributions were then compared to those compiled in this article. Results. Arnett's rule, as previously shown, gives ^56^Ni masses for SE-SNe that are considerably higher than SNe II. While for the distributions calculated using both the Khatami & Kasen (2019ApJ...878...56K) prescription and Tail ^56^Ni masses are offset to lower values than "Arnett values", their ^56^Ni distributions are still statistically higher than that of SNe II. Our results are strongly driven by a lack of SE-SN with low ^56^Ni masses, that are, in addition, strictly lower limits. The lowest SE-SN ^56^Ni mass in our sample is of 0.015M_{sun}_, below which are more than 25% of SNe II. We conclude that there exist real, intrinsic differences in the mass of synthesised radioactive material between SNe II and SE-SNe (types IIb, Ib, and Ic). Any proposed current or future CC SN progenitor scenario and explosion mechanism must be able to explain why and how such differences arise or outline a bias in current SN samples yet to be fully explored.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/3693
- Title:
- N in Galactic high-mass star-forming cores
- Short Name:
- J/MNRAS/478/3693
- Date:
- 10 Dec 2021 00:14:43
- Publisher:
- CDS
- Description:
- The fractionation of nitrogen (N) in star-forming regions is a poorly understood process. To put more stringent observational constraints on the N-fractionation, we have observed with the IRAM-30-m telescope a large sample of 66 cores in massive star-forming regions. We targeted the (1-0) rotational transition of HN^13^C, HC^15^N, H^13^CN and HC^15^N, and derived the ^14^N/^15^N ratio for both HCN and HNC. We have completed this sample with that already observed by Colzi et al., and thus analysed a total sample of 87 sources. The ^14^N/^15^N ratios are distributed around the Proto-Solar Nebula value with a lower limit near the TA value (~272). We have also derived the ^14^N/^15^N ratio as a function of the Galactocentric distance and deduced a linear trend based on unprecedented statistics. The Galactocentric dependences that we have found are consistent, in the slope, with past works but we have found a new local ^14^N/^15^N value of ~400, i.e. closer to the Prosolar Nebula value. A second analysis was done, and a parabolic Galactocentric trend was found. Comparison with Galactic chemical evolution models shows that the slope until 8 kpc is consistent with the linear analysis, while the flattening trend above 8 kpc is well reproduced by the parabolic analysis.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/L3
- Title:
- NIR spectra of 10 PNe in LMC and SMC
- Short Name:
- J/ApJ/831/L3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared spectra of 10 planetary nebulae (PNe) in the Large and Small Magellanic Clouds (LMC and SMC), acquired with the FIRE and GNIRS spectrometers on the 6.5 m Baade and 8.1 m Gemini South Telescopes, respectively. We detect Se and/or Kr emission lines in eight of these objects, the first detections of n-capture elements in Magellanic Cloud PNe. Our abundance analysis shows large s-process enrichments of Kr (0.6-1.3 dex) in the six PNe in which it was detected, and Se is enriched by 0.5-0.9 dex in five objects. We also estimate upper limits to Rb and Cd abundances in these objects. Our abundance results for the LMC are consistent with the hypothesis that PNe with 2-3 M_{\sun}_ progenitors dominate the bright end of the PN luminosity function in young gas-rich galaxies. We find no significant correlations between s-process enrichments and other elemental abundances, central star temperature, or progenitor mass, though this is likely due to our small sample size. We determine S abundances from our spectra and find that [S/H] agrees with [Ar/H] to within 0.2 dex for most objects, but is lower than [O/H] by 0.2-0.4 dex in some PNe, possibly due to O enrichment via third dredge-up. Our results demonstrate that n-capture elements can be detected in PNe belonging to nearby galaxies with ground-based telescopes, allowing s-process enrichments to be studied in PN populations with well-determined distances.
- ID:
- ivo://CDS.VizieR/J/ApJ/734/82
- Title:
- NIR spectroscopy of five dwarf galaxies
- Short Name:
- J/ApJ/734/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared (NIR) spectroscopic observations of five blue compact dwarf (BCD) galaxies, II Zw 40, Mrk 71, Mrk 930, Mrk 996, and SBS 0335-052E. The NIR spectra which cover the 0.90-2.40um wavelength range show hydrogen, molecular hydrogen, helium, sulfur, and iron emission lines. The NIR data for all BCDs have been supplemented by optical spectra.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/L113
- Title:
- Nitrogen abundance of Seyfert 2 AGN
- Short Name:
- J/MNRAS/468/L113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained new quantitative determinations of the nitrogen abundance and a consistent relation between the nitrogen and oxygen abundances for a sample of Seyfert 2 galaxies located at redshift z<0.1. We carried out this analysis using the CLOUDY code to build detailed photoionization models. We were able to reproduce observed optical narrow emission line intensities for 44 sources compiled from the literature. Our results show that Seyfert 2 nuclei have nitrogen abundances ranging from ~0.3 to ~7.5 times the solar value. We derived the relation log (N/H)=1.05(+/-0.09)x[log(O/H)]-0.35(+/-0.33). Results for N/O versus O/H abundance ratios derived for Seyfert 2 galaxies are in consonance with those recently derived for a sample of extragalactic disc HII regions with high metallicity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/3398
- Title:
- Nitrogen abundances for Be and B stars
- Short Name:
- J/MNRAS/471/3398
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photospheric nitrogen abundances for a sample of 26 Be stars and 16 normal B stars were found using high-resolution spectra from the Magnetism in Massive Stars (MiMeS) spectroscopic survey. Nitrogen abundances were obtained using non-local-thermodynamic-equilibrium equivalent widths and line profiles, and Monte Carlo simulation was used to determine the error bounds of the measured nitrogen abundances due to uncertainties in the adopted stellar parameters, continuum normalization and atomic data. In addition, the effects of gravitational darkening and disc contamination on the measured Be star nitrogen abundances were investigated. About one third of the sample of Be stars and half of the normal B-type stars have nitrogen enrichment that may be due to rotational mixing in these rapidly rotating objects. Corrections for gravitational darkening and disc contamination do not significantly change the overall results for the Be star sample. The average nitrogen abundance of the B and Be star samples coincides with the solar abundance, although the dispersion in the nitrogen abundances is much larger in the Be star sample. The Be star sample also has a significant fraction of sub-solar nitrogen abundance objects that are not present in significant numbers in the B star sample. This may point to yet unresolved systematic errors in the analysis of the Be stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/658/1203
- Title:
- Nitrogen-enhanced metal-poor stars
- Short Name:
- J/ApJ/658/1203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Theoretical models of very metal-poor intermediate-mass asymptotic giant branch (AGB) stars predict a large overabundance of primary nitrogen. The very metal-poor, carbon-enhanced, s-process-rich stars, which are thought to be the polluted companions of now extinct AGB stars, provide direct tests of the predictions of these models. Recent studies of the carbon and nitrogen abundances in metal-poor stars have focused on the most carbon-rich stars, leading to a potential selection bias against stars that have been polluted by AGB stars that produced large amounts of nitrogen and hence have small [C/N] ratios. We call these stars nitrogen-enhanced metal-poor (NEMP) stars and define them as having [N/Fe]>+0.5 and [C/N]<-0.5. In this paper we report on the [C/N] abundances of a sample of 21 carbon-enhanced stars, all but three of which have [C/Fe]<+2.0. If NEMP stars were made as easily as carbon-enhanced metal-poor (CEMP) stars, then we expected to find between two and seven NEMP stars. Instead, we found no NEMP stars in our sample.
