We report the discovery of an accreting supermassive black hole at z=8.679, in CEERS_1019, a galaxy previously discovered via a Ly\(\alpha\)-break by Hubble and with a Ly\(\alpha\) redshift from ...Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we observed this source with JWST/NIRSpec spectroscopy, MIRI and NIRCam imaging, and NIRCam/WFSS slitless spectroscopy. The NIRSpec spectra uncover many emission lines, and the strong O III emission line confirms the ground-based Ly\(\alpha\) redshift. We detect a significant broad (FWHM~1200 km/s) component in the H\(\beta\) emission line, which we conclude originates in the broad-line region of an active galactic nucleus (AGN), as the lack of a broad component in the forbidden lines rejects an outflow origin. This hypothesis is supported by the presence of high-ionization lines, as well as a spatial point-source component embedded within a smoother surface brightness profile. The mass of the black hole is log(\(M_{BH}/M_{\odot})=6.95{\pm}0.37\), and we estimate that it is accreting at 1.2 (\(\pm\)0.5) x the Eddington limit. The 1-8 \(\mu\)m photometric spectral energy distribution (SED) from NIRCam and MIRI shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M\(_{\odot}\)~9.5) and highly star-forming (SFR~30 M\(_{\odot}\) yr\(^{-1}\)). Ratios of the strong emission lines show that the gas in this galaxy is metal-poor (Z/Z\(_{\odot}\)~0.1), dense (n\(_{e}\)~10\(^{3}\) cm\(^{-3}\)), and highly ionized (log U~-2.1), consistent with the general galaxy population observed with JWST at high redshifts. We use this presently highest-redshift AGN discovery to place constraints on black hole seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from massive black hole seeds is required to form this object by the observed epoch.
We present a robust sample of very high-redshift galaxy candidates from the first epoch of {\it JWST}/NIRCam imaging from the Next Generation Extragalactic Exploratory Deep (NGDEEP) Survey. The ...NGDEEP NIRCam imaging in the Hubble Ultra Deep Field Parallel Field 2 (HUDF-Par2) reaches \(m=30.4\) (5\(\sigma\), point-source) in F277W, making it the deepest public {\it JWST} GO imaging dataset to date. We describe our detailed data reduction process of the six-filter broad-band {\it JWST}/NIRCam imaging, incorporating custom corrections for systematic effects to produce high-quality calibrated images. Using robust photometric redshift selection criteria, we identify a sample of 38 \(z \gtrsim 9\) galaxy candidates. These objects span a redshift range of \(z=8.5-15.8\), and apparent magnitudes of \(m_\mathrm{F277W} = 27-30.5\) AB mag, reaching \(\sim 1.5\) mag deeper than previous public {\it JWST} imaging surveys. We calculate the rest-frame ultraviolet (UV) luminosity function at \(z \sim\) 9 and 11, and present a new measurement of the luminosity function faint-end slope at \(z \sim 11\). There is no significant evolution in the faint-end slope and number density from \(z=9\) to 11. Comparing our results with theoretical predictions, we find that some models produce better agreement at the faint end than the bright end. These results will help to constrain how stellar feedback impacts star formation at these early epochs.
We present the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey, a deep slitless spectroscopic and imaging Cycle 1 JWST treasury survey designed to constrain feedback mechanisms ...in low-mass galaxies across cosmic time. NGDEEP targets the Hubble Ultra Deep Field (HUDF) with NIRISS slitless spectroscopy (f~1.2e-18 erg/s/cm^2, 5sigma) to measure metallicities and star-formation rates (SFRs) for low-mass galaxies through the peak of the cosmic SFR density (0.5<z<4). In parallel, NGDEEP targets the HUDF-Par2 parallel field with NIRCam (m=30.6-30.9, 5sigma) to discover galaxies to z>12, constraining the slope of the faint-end of the rest-ultraviolet luminosity function. NGDEEP overlaps with the deepest HST ACS optical imaging in the sky: F435W in the HUDF (m=29.6), and F814W in HUDF-Par2 (m=30), making this a premier HST+JWST Deep Field. As a treasury survey, NGDEEP data is public immediately, and we will rapidly release data products and catalogs in the spirit of previous deep field initiatives. In this paper we present the NGDEEP survey design, summarize the science goals, and detail plans for the public release of NGDEEP reduced data products.
Ombres de Thucydide Alvar, Jaime; Andurand, Anthony; Bertrand, Estelle ...
2010
Book
Open access
Durant toute l’Antiquité, l’historien Thucydide a constitué une référence obligée et un modèle qui a inspiré nombre de continuateurs et d’imitateurs, en milieu grec et à Rome, que ce soit pour sa ...méthode ou pour les caractéristiques formelles de son œuvre. Cet engouement, qui a perduré jusqu’au Moyen Âge byzantin et ne s’est pas démenti à la Renaissance, redouble à partir du xviiie siècle, au moment où l’histoire se construit comme « science » : la Guerre du Péloponnèse devient alors le paradigme de l’histoire « véritable », rationaliste et positiviste. C’est aussi au xviiie siècle que se construit une certaine image de l’Athènes classique, largement tributaire de la vision qu’en donne Thucydide. Cependant, depuis quelques années, l’héritage documentaire auquel son nom est attaché se voit de plus en plus contesté par les historiens et les archéologues spécialistes de cette période. La fortune de Thucydide, les modalités de sa réception ont donc varié selon les époques, et ce sont ces fluctuations qu’il a paru nécessaire d’étudier sur la longue durée, de manière aussi exhaustive que possible, en croisant les points de vue disciplinaires.
