We analyse the chemical properties of three z∼ 8 galaxies behind the galaxy cluster SMACS J0723.3-7327, observed as part of the Early Release Observations programme of the James Webb Space Telescope (JWST). Exploiting [O iii]λ4363 auroral line detections in NIRSpec spectra, we robustly apply the direct Te method for the very first time at such high redshift, measuring metallicities ranging from extremely metal poor (12+log(O/H)≈ 7) to about one-third solar. We also discuss the excitation properties of these sources, and compare them with local strong-line metallicity calibrations. We find that none of the considered diagnostics match simultaneously the observed relations between metallicity and strong-line ratios for the three sources, implying that a proper re-assessment of the calibrations may be needed at these redshifts. On the mass-metallicity plane, the two galaxies at z ∼ 7.6 ($\rm log(M_*/M_{\odot }) = 8.1, 8.7$) have metallicities that are consistent with the extrapolation of the mass-metallicity relation at z∼2-3, while the least massive galaxy at z ∼ 8.5 ($\rm log(M_*/M_{\odot }) = 7.8$) shows instead a significantly lower metallicity . The three galaxies show different level of offset relative to the Fundamental Metallicity Relation, with two of them (at z∼ 7.6) being marginally consistent, while the z∼ 8.5 source deviating significantly, being probably far from the smooth equilibrium between gas flows, star formation and metal enrichment in place at later epochs.
We examined the evolution of the oxidation state and atomic structure of V in nanophase V 2 O 5 aerogel and ambigel cathodes under in situ conditions using X-ray absorption spectroscopy ͑XAS͒. We show that the oxidation state of V in V 2 O 5 aerogel and ambigel cathodes heated under vacuum ͑100 Torr͒ at 220°C for 16 h is similar to that of V in a commercially obtained sample of orthorhombic V 2 O 5 . However, the local structure of V in aerogel and ambigel V 2 O 5 has a higher degree of local symmetry relative to orthorhombic V 2 O 5 and/or the average V-O bond length is greater than that of orthorhombic V 2 O 5 . Furthermore, we show that during the first cycle of discharge, the degree of Li insertion ͑x in Li x V 2 O 5 ) for the ambigel cathode is greater than that of the aerogel cathode (x ϭ 3.06 for the ambigel cathode compared to x ϭ 2.68 for the aerogel cathode͒ for the same cut-off voltage. Accordingly, the observed V K-edge energy shift for the fully discharged ambigel cathode is greater than that observed for the fully discharged aerogel cathode, and hence, the extent of reduction of pentavalent V is greater for the ambigel cathode. In both cases, the extent of reduction of the V is consistent with the amount of Li inserted ͑i.e., Li x V 2 O 5 ). Initially, pentavalent V is reduced to tetravalent V in the intercalation range 0 Ͻ x Ͻ 2 and then tetravalent V is reduced to trivalent V upon insertion of more Li (x Ͼ 2). Analyses of Fourier transform data reveal that V has a higher degree of local symmetry in the discharged state relative to that of the charged state.Due to a steady increase in the demand for high energy density rechargeable batteries, nanophase vanadium pentoxide (V 2 O 5 ), synthesized using sol-gel techniques, is considered a viable alternative to the cobalt and nickel oxides currently used in lithium ͑Li͒ and Li-ion batteries. 1-3 The electrochemical performance of V 2 O 5 , however, depends on the nature of its structure ͑crystalline vs. amorphous͒ and morphology ͑particle size, surface area, and pore volume͒. 4-7 The electrochemical performance of V 2 O 5 gels has been shown to be superior to that of crystalline material due to their nearly amorphous structure, high surface area, and pore volume distribution. The Li storage capacity of V 2 O 5 gels has been shown to be close to 4 Li per V 2 O 5 yielding capacities as high as 560 mAh/g. Nonetheless, the rechargeable capacity of V 2 O 5 gels strongly depends on preparation conditions such as the method of removal of pore liquid and postpreparation drying/heating conditions, which can alter the structure, water content, and morphology of the final product. In addition, the capacity of V 2 O 5 cathodes has been shown to decrease with increased cycling. Hence, an improved understanding of ͑i͒ the structure of V 2 O 5 gels as a function of preparation method and ͑ii͒ the mechanism of Li interaction with gels during charge ͑Li insertion͒ and discharge ͑Li removal͒ cycles is warranted.In a previous study, 8 the effect of heating at 114 and 220...
We investigate the nature of the scaling relations between the surface density of star formation rate (ΣSFR), stellar mass (Σ*), and molecular gas mass ($\Sigma _{\rm H_2}$), aiming at distinguishing between the relations that are primary, i.e. more fundamental, and those which are instead an indirect by-product of the other relations. We use the ALMaQUEST survey and analyse the data by using both partial correlations and Random Forest regression techniques. We unambiguously find that the strongest intrinsic correlation is between ΣSFR and $\Sigma _{\rm H_2}$ (i.e. the resolved Schmidt-Kennicutt relation), followed by the correlation between $\Sigma _{\rm H_2}$ and Σ* (resolved Molecular Gas Main Sequence, rMGMS). Once these two correlations are taken into account, we find that there is no evidence for any intrinsic correlation between ΣSFR and Σ*, implying that SFR is entirely driven by the amount of molecular gas, while its dependence on stellar mass (i.e. the resolved Star Forming Main Sequence, rSFMS) simply emerges as a consequence of the relationship between molecular gas and stellar mass.
We present JWST NIRCam nine-band near-infrared imaging of the luminous z = 10.6 galaxy GN-z11 from the JWST Advanced Deep Extragalactic Survey of the GOODS-N field. We find a spectral energy distribution (SED) entirely consistent with the expected form of a high-redshift galaxy: a clear blue continuum from 1.5 to 4 μm with a complete dropout in F115W. The core of GN-z11 is extremely compact in JWST imaging. We analyze the image with a two-component model, using a point source and a Sérsic profile that fits to a half-light radius of 200 pc and an index n = 0.9. We find a low-surface-brightness haze about 0.″4 to the northeast of the galaxy, which is most likely a foreground object but might be a more extended component of GN-z11. At a spectroscopic redshift of 10.60 (Bunker et al. 2023), the comparison of the NIRCam F410M and F444W images spans the Balmer jump. From population-synthesis modeling, here assuming no light from an active galactic nucleus, we reproduce the SED of GN-z11, finding a stellar mass of ∼109 M ⊙, a star formation rate of ∼20 M ⊙ yr−1, and a young stellar age of ∼20 Myr. Since massive galaxies at high redshift are likely to be highly clustered, we search for faint neighbors of GN-z11, finding nine galaxies out to ∼5 comoving Mpc transverse with photometric redshifts consistent with z = 10.6, and a tenth more tentative dropout only 3″ away. This is consistent with GN-z11 being hosted by a massive dark-matter halo (≈8 × 1010 M ⊙), though lower halo masses cannot be ruled out.
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