arXiv subjects

Nicolas F. Bouche

Publications and source records attributed to Nicolas F. Bouche.

4 recordsLinked to original sources

arXiv2025

MUSEQuBES: The Column Density, Covering Fraction, Mass, and Environmental Dependence of Cool HI Gas Around Low-Redshift Galaxies

We investigate cool HI gas traced by Lyman series absorption around 256 galaxies at z ~ 0.48 (median stellar mass, log10(M*/Msun) = 8.7) using 15 background quasars (median impact parameter, D = 140 pkpc), as part of the MUSE Quasar-fields Blind Emitters Survey (MUSEQuBES). We find that the HI column density (N(HI)) profile around isolated star-forming galaxies spanning ~3 dex in stellar mass is well described by a power law with slope ~ -3 when expressed as a function of normalized impact parameter D/Rvir. The HI covering fraction (k) within the virial radius for log10(N(HI)/cm^{-2}) = 14 is significantly lower in high-mass passive galaxies than in isolated star-forming galaxies. The k-profile of isolated star-forming galaxies suggests a characteristic size of the HI-rich CGM of ~ 1.5 Rvir across the stellar mass range. The mean HI mass in the outer CGM (0.3-1 Rvir ) increases with stellar mass, ranging from ~ 10^5 to 10^6.6 Msun. The b-parameters of the strongest HI components correlate and anti-correlate with specific star-formation rate (sSFR) and mass, respectively, with >2 sigma significance. Broad Lya absorbers (BLAs) with b > 60 km/s are predominantly associated with high-mass galaxies, likely tracing the warm-hot phase of the CGM. The velocity centroids of H i components indicate that absorbers at D < Rvir are largely consistent with being gravitationally bound to their galaxies, independent of stellar mass. Finally, leveraging ~ 3000 galaxies from the wide-field Magellan follow-up of six MUSEQuBES fields, we find that non-isolated galaxies exhibit an HI-rich environment extending roughly three times farther than in isolated counterparts.

astro-ph.GA↗

arXiv2024

The Wide-field Spectroscopic Telescope (WST) Science White Paper

The Wide-field Spectroscopic Telescope (WST) is proposed as a new facility dedicated to the efficient delivery of spectroscopic surveys. This white paper summarises the initial concept as well as the corresponding science cases. WST will feature simultaneous operation of a large field-of-view (3 sq. degree), a high multiplex (20,000) multi-object spectrograph (MOS) and a giant 3x3 sq. arcmin integral field spectrograph (IFS). In scientific capability these requirements place WST far ahead of existing and planned facilities. Given the current investment in deep imaging surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work synergistically with future ground and space-based facilities. This white paper shows that WST can address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; origin of stars and planets; time domain and multi-messenger astrophysics. WST's uniquely rich dataset will deliver unforeseen discoveries in many of these areas. The WST Science Team (already including more than 500 scientists worldwide) is open to the all astronomical community. To register in the WST Science Team please visit https://www.wstelescope.com/for-scientists/participate

astro-ph.IM↗

arXiv2023

EMPRESS. IX. Extremely Metal-Poor Galaxies are Very Gas-Rich Dispersion-Dominated Systems: Will JWST Witness Gaseous Turbulent High-z Primordial Galaxies?

We present kinematics of 6 local extremely metal-poor galaxies (EMPGs) with low metallicities ($0.016-0.098\ Z_{\odot}$) and low stellar masses ($10^{4.7}-10^{7.6} M_{\odot}$). Taking deep medium-high resolution ($R\sim7500$) integral-field spectra with 8.2-m Subaru, we resolve the small inner velocity gradients and dispersions of the EMPGs with H$α$ emission. Carefully masking out sub-structures originated by inflow and/or outflow, we fit 3-dimensional disk models to the observed H$α$ flux, velocity, and velocity-dispersion maps. All the EMPGs show rotational velocities ($v_{\rm rot}$) of 5--23 km s$^{-1}$ smaller than the velocity dispersions ($σ_{0}$) of 17--31 km s$^{-1}$, indicating dispersion-dominated ($v_{\rm rot}/σ_{0}=0.29-0.80<1$) systems affected by inflow and/or outflow. Except for two EMPGs with large uncertainties, we find that the EMPGs have very large gas-mass fractions of $f_{\rm gas}\simeq 0.9-1.0$. Comparing our results with other H$α$ kinematics studies, we find that $v_{\rm rot}/σ_{0}$ decreases and $f_{\rm gas}$ increases with decreasing metallicity, decreasing stellar mass, and increasing specific star-formation rate. We also find that simulated high-$z$ ($z\sim 7$) forming galaxies have gas fractions and dynamics similar to the observed EMPGs. Our EMPG observations and the simulations suggest that primordial galaxies are gas-rich dispersion-dominated systems, which would be identified by the forthcoming James Webb Space Telescope (JWST) observations at $z\sim 7$.

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arXiv2021

MUSEQuBES: Characterizing the circumgalactic medium of redshift $\approx3.3$ Ly$α$ emitters

We present the first characterization of the circumgalactic medium of Ly$α$ emitters (LAEs), using a sample of 96 $z\approx3.3$ LAEs detected with the VLT/MUSE in fields centered on 8 bright background quasars. The LAEs have low Ly$α$ luminosities ($\sim 10^{42}\,\text{erg}\,\text{s}^{-1}$) and star formation rates (SFRs) $\sim 1~\text{M}_\odot\,\text{yr}^{-1}$, which for main sequence galaxies corresponds to stellar masses of only $\sim 10^{8.6}\,\text{M}_\odot$. The median transverse distance between the LAEs and the quasar sightlines is 165 proper kpc (pkpc). We stacked the high-resolution quasar spectra and measured significant excess HI and CIV absorption near the LAEs out to 500 $\text{km}\,\text{s}^{-1}$ and at least $\approx 250$ pkpc (corresponding to $\approx 7$ virial radii). At $\lesssim 30~\text{km}\,\text{s}^{-1}$ from the galaxies the median HI and CIV optical depths are enhanced by an order of magnitude. The absorption is significantly stronger around the $\approx 1/3$ of our LAEs that are part of `groups', which we attribute to the large-scale structures in which they are embedded. We do not detect any strong dependence of either the HI or CIV absorption on transverse distance (over the range $\approx 50-250$ pkpc), redshift, or the properties of the Ly$α$ emission line (luminosity, full width at half maximum, or equivalent width). However, for HI, but not CIV, the absorption at $\lesssim 100\,\text{km}\,\text{s}^{-1}$ from the LAE does increase with the SFR. This suggests that LAEs surrounded by more HI tend to have higher SFRs.

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