分类： 天文学 >> 天文学 提交时间： 2023-02-19
Danial Langeroodi
Jens Hjorth
Wenlei Chen
Patrick L. Kelly
Hayley Williams
Yu-Heng Lin
Claudia Scarlata
Adi Zitrin
Tom Broadhurst
Jose M. Diego
Xiaosheng Huang
Alexei V. Filippenko
Ryan J. Foley
Saurabh Jha
Anton M. Koekemoer
Masamune Oguri
Ismael Perez-Fournon
Justin Pierel
Frederick Poidevin
Lou Strolger
摘要： A tight positive correlation between the stellar mass and the gas-phase metallicity of galaxies has been observed at low redshifts, with only $\sim 0.1$ dex scatter in metallicity. The shape and normalization of this correlation can set strong constraints on theories of galaxy evolution. In particular, its redshift evolution is thought to be determined by stellar and active galactic nucleus feedback-driven outflows, the redshift evolution of the stellar initial mass function or stellar yields, and broadly the star-formation histories of galaxies. The advent of \jwst\ allows probing the mass--metallicity relation at redshifts far beyond what was previously accessible. Here we report the discovery of two emission-line galaxies at redshift $z = 8.15$ and $z = 8.16$ in \jwst\ NIRCam imaging and NIRSpec spectroscopy of galaxies gravitationally lensed by the cluster RX\,J2129.4$+$0009. We measure their metallicities using the strong-line method and their stellar masses through spectral-energy-distribution fitting with a nonparametric star-formation history. We combine these with nine similarly re-analysed galaxies at $7.2 < z < 9.5$ to compile a sample of eleven galaxies at $z \approx 8$ (six with \jwst\ metallicities and five with ALMA metallicities). Based on this sample, we report the first quantitative statistical inference of the mass--metallicity relation at $z\approx8$ (median $z = 8.15$). We measure a $\sim 1.0$ dex redshift evolution in the normalization of the mass--metallicity relation from $z \approx 8$ to the local Universe; at fixed stellar mass, galaxies are 10 times less metal enriched at $z \approx 8$ compared to the present day (abridged).
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Hayley Williams
Patrick L. Kelly
Wenlei Chen
Gabriel Brammer
Adi Zitrin
Tommaso Treu
Claudia Scarlata
Anton M. Koekemoer
Masamune Oguri
Yu-Heng Lin
Jose M. Diego
Mario Nonino
Jens Hjorth
Danial Langeroodi
Tom Broadhurst
Noah Rogers
Ismael Perez-Fournon
Ryan J. Foley
Saurabh Jha
Alexei V. Filippenko
摘要： Given their extremely faint apparent brightness, the nature of the first galaxies and how they reionized the Universe's gas are not yet understood. Here we report the discovery, in JWST imaging, of a highly magnified, low mass (log(Mstellar/Msun) = 7.63+0.22-0.24) galaxy visible when the Universe was only 510 Myr old, and follow-up JWST spectroscopy from Lyman alpha to [O III] 5007 A in its rest frame. We detect the [O III] 5007 A and H Beta emission lines with a respective signal-to-noies ratio of 40 and 7, and five additional lines with signal-to-noise greater than 3. The galaxy's magnification of approximately 20 allows us to measure a radius of 16.4+10.7-7.0 pc, which is a factor of 9.3+10.5-4.4 (3.5 sigma) smaller than galaxies with comparable luminosity at z = 6 - 8.
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