The FMOS-COSMOS survey of star-forming galaxies at z~1.6. IV: Excitation state and chemical enrichment of the interstellar medium

We investigate the physical conditions of ionized gas in high-z star-forming galaxies using diagnostic diagrams based on the rest-frame optical emission lines. The sample consists of 701 galaxies with an Ha detection at $1.4\lesssim z\lesssim1.7$, from the FMOS-COSMOS survey, that represent the normal star-forming population over the stellar mass range $10^{9.6} \lesssim M_\ast/M_\odot \lesssim 10^{11.6}$ with those at $M_\ast>10^{11}~M_\odot$ being well sampled. We confirm an offset of the average location of star-forming galaxies in the BPT diagram ([OIII]/Hb vs. [NII]/Ha), primarily towards higher [OIII]/Hb, compared with local galaxies. Based on the [SII] ratio, we measure an electron density ($n_e=220^{+170}_{-130}~\mathrm{cm^{-3}}$), that is higher than that of local galaxies. Based on comparisons to theoretical models, we argue that changes in emission-line ratios, including the offset in the BPT diagram, are caused by a higher ionization parameter both at fixed stellar mass and at fixed metallicity with additional contributions from a higher gas density and possibly a hardening of the ionizing radiation field. Ionization due to AGNs is ruled out as assessed with Chandra. As a consequence, we revisit the mass-metallicity relation using [NII]/Ha and a new calibration including [NII]/[SII] as recently introduced by Dopita et al. Consistent with our previous results, the most massive galaxies ($M_\ast\gtrsim10^{11}~M_\odot$) are fully enriched, while those at lower masses have metallicities lower than local galaxies. Finally, we demonstrate that the stellar masses, metallicities and star formation rates of the FMOS sample are well fit with a physically-motivated model for the chemical evolution of star-forming galaxies.Comment: 38 pages; Accepted for publication in Ap

Rifiuti industriali. Metodologie di calcolo dei coefficienti di produzione

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Resolving Galactic-scale Obscuration of X-Ray AGNs at z ≳ 1 with COSMOS-Web

A large fraction of the accreting supermassive black hole population is shrouded by copious amounts of gas and dust, particularly in the distant (z ≳ 1) universe. While much of the obscuration is attributed to a parsec-scale torus, there is a known contribution from the larger-scale host galaxy. Using JWST/NIRCam imaging from the COSMOS-Web survey, we probe the galaxy-wide dust distribution in X-ray selected active galactic nuclei (AGNs) up to z ∼ 2. Here, we focus on a sample of three AGNs with their host galaxies exhibiting prominent dust lanes, potentially due to their edge-on alignment. These represent 27% (3 out of 11 with early NIRCam data) of the heavily obscured (N H &gt; 1023 cm−2) AGN population. With limited signs of a central AGN in the optical and near-infrared, the NIRCam images are used to produce reddening maps E(B − V) of the host galaxies. We compare the mean central value of E(B − V) to the X-ray obscuring column density along the line of sight to the AGN (N H ∼ 1023−23.5 cm−2). We find that the extinction due to the host galaxy is present (0.6 ≲ E(B − V) ≲ 0.9; 1.9 ≲ A V ≲ 2.8) and significantly contributes to the X-ray obscuration at a level of N H ∼ 1022.5 cm−2 assuming an SMC gas-to-dust ratio that amounts to ≲30% of the total obscuring column density. These early results, including three additional cases from CEERS, demonstrate the ability to resolve such dust structures with JWST and separate the different circumnuclear and galaxy-scale obscuring structures.</p

Resolving Galactic-scale Obscuration of X-Ray AGNs at z ≳ 1 with COSMOS-Web

A large fraction of the accreting supermassive black hole population is shrouded by copious amounts of gas and dust, particularly in the distant (z ≳ 1) universe. While much of the obscuration is attributed to a parsec-scale torus, there is a known contribution from the larger-scale host galaxy. Using JWST/NIRCam imaging from the COSMOS-Web survey, we probe the galaxy-wide dust distribution in X-ray selected active galactic nuclei (AGNs) up to z ∼ 2. Here, we focus on a sample of three AGNs with their host galaxies exhibiting prominent dust lanes, potentially due to their edge-on alignment. These represent 27% (3 out of 11 with early NIRCam data) of the heavily obscured (N H &gt; 1023 cm−2) AGN population. With limited signs of a central AGN in the optical and near-infrared, the NIRCam images are used to produce reddening maps E(B − V) of the host galaxies. We compare the mean central value of E(B − V) to the X-ray obscuring column density along the line of sight to the AGN (N H ∼ 1023−23.5 cm−2). We find that the extinction due to the host galaxy is present (0.6 ≲ E(B − V) ≲ 0.9; 1.9 ≲ A V ≲ 2.8) and significantly contributes to the X-ray obscuration at a level of N H ∼ 1022.5 cm−2 assuming an SMC gas-to-dust ratio that amounts to ≲30% of the total obscuring column density. These early results, including three additional cases from CEERS, demonstrate the ability to resolve such dust structures with JWST and separate the different circumnuclear and galaxy-scale obscuring structures.</p

Resolving Galactic-scale Obscuration of X-Ray AGNs at z ≳ 1 with COSMOS-Web

A large fraction of the accreting supermassive black hole population is shrouded by copious amounts of gas and dust, particularly in the distant ( z ≳ 1) universe. While much of the obscuration is attributed to a parsec-scale torus, there is a known contribution from the larger-scale host galaxy. Using JWST/NIRCam imaging from the COSMOS-Web survey, we probe the galaxy-wide dust distribution in X-ray selected active galactic nuclei (AGNs) up to z ∼ 2. Here, we focus on a sample of three AGNs with their host galaxies exhibiting prominent dust lanes, potentially due to their edge-on alignment. These represent 27% (3 out of 11 with early NIRCam data) of the heavily obscured ( N _H > 10 ^23 cm ^−2 ) AGN population. With limited signs of a central AGN in the optical and near-infrared, the NIRCam images are used to produce reddening maps E ( B − V ) of the host galaxies. We compare the mean central value of E ( B − V ) to the X-ray obscuring column density along the line of sight to the AGN ( N _H ∼ 10 ^23−23.5 cm ^−2 ). We find that the extinction due to the host galaxy is present (0.6 ≲ E ( B − V ) ≲ 0.9; 1.9 ≲ A _V ≲ 2.8) and significantly contributes to the X-ray obscuration at a level of N _H ∼ 10 ^22.5 cm ^−2 assuming an SMC gas-to-dust ratio that amounts to ≲30% of the total obscuring column density. These early results, including three additional cases from CEERS, demonstrate the ability to resolve such dust structures with JWST and separate the different circumnuclear and galaxy-scale obscuring structures