arXiv subjects

Caterina Liboni

Publications and source records attributed to Caterina Liboni.

5 recordsLinked to original sources

arXiv2026

Developing Environments: Formation and Quenching at Cosmic Noon Traced by the Large-scale Distribution of Gas and Galaxies

Environmental density correlates with galaxy properties in the local Universe, but how and when these trends emerge is unclear: at cosmic noon, large-scale structures are still assembling and galaxies quench rapidly for debated reasons. We study how the formation and quenching histories of massive galaxies at 1.7$<$z$<$3.5 depend on environment, using two independent tracers: galaxy number density ($δ_\#$) from COSMOS-Web and intergalactic neutral hydrogen ($δ_{HI}$, cool gas) from LATIS Ly$α$ tomography. We combine 139 Blue Jay JWST/NIRSpec galaxies with 57 DAWN JWST Archive prism spectra in COSMOS, deriving stellar masses, star formation histories, dust attenuation, and Na\,{\sc d} outflow rates from joint spectro-photometric \texttt{Prospector} fits. In massive quiescent galaxies, the formation-to-quenching interval increases with density. AGN and Na\,{\sc d} outflows are confined to $δ_\#<0.5$ and elevated Ly$α$ absorption ($δ_{HI}>1$), mostly in massive quiescent galaxies showing both. About 65\% of the sample follows a correlation between the tracers; two outlier regions stand out. A galaxy-rich, gas-poor region ($δ_\#>2$, $δ_{HI}<1$) coincides with one of the most massive Hyperion protocluster cores, where the gas is plausibly fully ionized; its quiescent galaxies formed earlier and lack significant AGN activity and outflows. A galaxy-poor, gas-rich region ($δ_\#<1$, $δ_{HI}>1$), within 60 cMpc of the densest Hyperion cores, hosts rapidly quenched galaxies with a high incidence of AGN and outflows. This \emph{developing environment}, distinct from both mature protoclusters and the field, likely traces massive halos still assembling. Galaxy counts alone cannot capture the environment at cosmic noon: jointly mapping galaxies and cool gas is crucial to understand how environment regulates gas accretion, star formation, and quenching.

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arXiv2026

How Steep is your Dust? Direct Measurements of Nebular Attenuation Curves at Cosmic Noon with JWST

Tracing the shape of the nebular attenuation curve, which is crucial for accurately measuring intrinsic emission-line fluxes, has proven challenging both in the local universe and at high redshift. Here we present nebular dust attenuation curves measured directly for 24 star-forming galaxies ($9.3<\log(\rm M{\star}/M_\odot)<11.1$) at cosmic noon ($1.8<z<3.3$) from the Blue Jay survey. Using deep JWST/NIRSpec spectra, we measure up to eight hydrogen recombination lines from H$δ$ to Pa$β$ per galaxy and find little diversity in the curve shape, with most galaxies agreeing with the \citet{calzetti_dust_2000} attenuation curve. For over $90\%$ of the sample, the nebular reddening from the Balmer lines is consistent with that from the Paschen lines. Using \texttt{Prospector} spectral energy distribution (SED) fits, we obtain the stellar reddening and find that the difference between stellar and nebular reddening increases with stellar mass, and that each reddening measurement is independent of inclination, which disagrees with the two-component dust model. We then measure the impact of using the derived nebular attenuation curve or a literature curve when determining metallicity using the strong-line method, and find that for some diagnostics (e.g., S32, S3, S23, and S3O3), the difference can be as large as $5σ$. Caution is needed when using these diagnostics if the nebular attenuation curve cannot be directly measured, since the resulting uncertainty can exceed the measurement uncertainty on the emission-line fluxes even with high signal-to-noise Balmer decrement measurements. These results show that the shape of the nebular attenuation curve is poorly understood and that constraining it is important for reducing systematic uncertainty in galaxy measurements.

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arXiv2026

The Blue Jay Survey: Deep JWST Spectroscopy for a Representative Sample of Galaxies at Cosmic Noon

We present the Blue Jay survey, a cycle 1 JWST program aimed at studying the stellar and gas content of galaxies at cosmic noon. The survey consists of deep spectroscopy for 153 targets observed over two pointings in the COSMOS field using the NIRSpec micro-shutter assembly (MSA). We employed the three medium-resolution gratings, G140M, G235M, and G395M, with exposure times of 13 hours, 3.2 hours, and 1.6 hours, respectively. We thus obtained full coverage of the 1 - 5 um range, corresponding to the entire rest-frame optical wavelength range, with a spectral resolution R~1000. Parallel observations provided deep multiband NIRCam imaging, which partially overlaps with the spectroscopic observations. The sample was carefully selected to provide a census of galaxies over the redshift range 1.7 < z < 3.5 without strong biases in color, star formation rate, or other properties. Since the standard A-B nod subtraction leads to flux self-subtraction for large galaxies, we constructed a master background from empty shutters and subtracted it from each of the science spectra. In order to obtain self-consistent fits of spectroscopic and photometric data, we measured multiband photometry using space-based observations from the exact area in the sky where the NIRSpec 1D spectrum is extracted. The spectra contain a wealth of emission and absorption lines, including hydrogen lines, helium lines, metal emission lines from ionized gas, metal stellar absorption lines, and resonant absorption lines. Spectroscopic redshifts are unambiguously measured for 93% of the sample. The Blue Jay dataset, which we publicly release, represents the ideal sample for studying the stellar populations, neutral gas, and ionized gas in cosmic noon galaxies, including star formation histories, quenching, outflows, metallicity, and dust attenuation.

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arXiv2026

Outflows in the Early Universe: Neutral gas Absorption in Galaxies at z > 3 from low-resolution JWST Spectroscopy

Recent JWST/NIRSpec observations have shown that Na I D absorption tracing neutral gas outflows is widespread in massive galaxies at Cosmic Noon ($z\sim2$-$3$), but their prevalence at higher redshift remains largely unexplored. Here we investigate whether similar outflows are already in place during the first 2 Gyr of cosmic history ($z>3$), using a sample of 811 galaxies at $3 5$ in their JWST/NIRSpec PRISM low-resolution spectra ($R\sim100$). We derived physical properties and star formation histories via Prospector SED fitting and isolated the Na I D feature in each spectrum by subtracting the best-fit stellar continuum. We detect an excess of Na I D absorption in 20 galaxies, almost all at $3 10^{10} M_\odot$, an overall detection fraction of $\sim2.5\%$. The detection fraction rises steeply with stellar mass and quiescence, reaching $\sim11\%$ among the most massive galaxies and $\sim43\%$ among massive quenched systems. The Na I D equivalent widths are large, spanning 4 to 16 Angstrom, and are highest in dusty star-forming galaxies. In previous medium-resolution observations, EWs above 5 Angstrom were mostly found in outflowing gas; we thus interpret our detections as mostly tracing neutral outflows, despite the lack of kinematic information at PRISM resolution. A stacking analysis confirms these trends and provides average Na I D EWs for different subsamples. Under conservative assumptions, we estimate mass outflow rates of 4 to 12 $M_\odot$ yr$^{-1}$, exceeding the current star formation rate for about 30% of the detected galaxies. We conclude that neutral outflows are likely already present and important in massive galaxies during the first 2 Gyr of cosmic history.

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arXiv2026

Probing neutral outflows in z ~ 2 galaxies using JWST observations of Ca II H and K absorption lines

Using deep JWST/NIRSpec spectra from the Blue Jay survey, we perform the first systematic investigation of neutral gas content in massive galaxies at Cosmic Noon based on the Ca II H, K absorption lines. We analyze a sample of 9 galaxies at 1.8 < z < 2.8 with stellar masses > 10.6, for which we detect neutral gas absorption both in Ca II and in Na I. After removing the stellar continuum using the best-fit model obtained with Prospector, we fit the excess absorption due to neutral gas in the Ca II H, K doublet and in the Na I D doublet, together with nearby emission lines produced by ionized gas. We measure covering fractions between 0.2 and 0.9 from the Ca II H and K lines, which are spectrally well resolved in the NIRSpec R ~ 1000 observations, unlike the absorption lines in the Na I D doublet. We measure the velocity shift, velocity dispersion, and column density separately for Ca II and Na I. About half of the galaxies present blueshifted Ca II, indicative of an outflow of neutral gas, consistent with previous results based on Na I. The velocity shift and the column density measured from Ca II are correlated with those measured from Na I, implying that these absorption lines trace gas in similar physical conditions. However, the column densities are not in a 1:1 relation, meaning that the relative amount of Ca II and Na I atoms along the line of sight varies with the gas column density. After discussing possible reasons for this behavior, we derive an empirical relation between the column density of Ca II and the column density of Na I and, in a more indirect way, of neutral hydrogen H I. This calibration offers a new way to estimate the outflow mass and the mass outflow rate for the neutral phase from current and future JWST observations of massive galaxies at Cosmic Noon and beyond

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