arXiv subjects

V. Bollo

Publications and source records attributed to V. Bollo.

2 recordsLinked to original sources

arXiv2026

MUSE-ALMA Haloes XVI: a census of the condensed baryons in z~0.5 HI absorption-selected galaxies

We use the MUSE-ALMA Haloes sample to build a census of the condensed baryons (stars and cold gas) to study the multiphase interstellar medium and circumgalactic medium (CGM). The sample includes 79 gas-rich galaxies at 0.2<z<1.2 located near strong HI Ly-alpha absorbers along quasar sightlines within projected separations of ~5-270 kpc and radial velocity separations of up to 500 km/s. HST spectroscopy characterises the absorbers, while HST imaging, MUSE and ALMA observations trace the stars, ionised gas and molecular gas. We find the following results. (i) HI masses inferred from optical properties show broad agreement with those derived from the CGM absorber properties for impact parameters <100 kpc, although group environments can significantly influence these estimates. (ii) The molecular gas fraction declines more steeply with stellar mass than the HI fraction. This suggests that stars build up more rapidly than the cold gas reservoir, while massive galaxies either consume their molecular gas more efficiently or convert HI into H2 less efficiently. (iii) Galaxies with high stellar surface densities exhibit the highest baryon fractions. This may reflect baryonic feedback, which can produce flatter inner dark matter profiles in high surface density systems, or aperture effects, where the ionised gas kinematic tracer probes only the innermost, baryon-dominated regions in compact sources, but extends further into the dark matter halo in sources with extended baryonic distributions. (iv) A few galaxies are consistent with being the baryon-dominated descendants of the low mass z~6 galaxies detected by JWST, while many appear to be substantially more dark matter dominated, lower mass systems with progenitors beyond JWST detection limits. This study provides a multiscale, multiphase view of the gas in and around galaxies, allowing us to probe the baryon budget across cosmic time.

astro-ph.GA↗

arXiv2026

MUSE-ALMA Haloes XV: Cold molecular, ionised, and stellar kinematics of HI-rich galaxies at z $\sim$ 0.5

Spatially resolved galaxy kinematics are well studied at z $\sim$ 0 and z > 1, revealing that disks are common out to z $\sim3-6$, albeit with higher velocity dispersions. z $\sim$ 0.5 marks a key transition in the drivers of disk turbulence and baryonic-dark matter mass budgets, yet multi-tracer resolved kinematic studies remain rare beyond the local Universe. We exploit a unique dataset combining ALMA CO observations with MUSE ionised gas and stellar continuum data to study the resolved kinematics of six galaxies at 0.43 < z < 0.83, part of the MUSE-ALMA Haloes program, selected via their association with H I absorption systems and spanning stellar masses from log$(M_\star/M_\odot) = 10.1 - 11.8$. Combining new ALMA/CO data with existing MUSE H$β$ kinematics and HST morphologies, we classify galaxies using morpho-kinematic criteria. For rotating disks, we jointly model H$β$ and CO(2-1) kinematics with DYSMALPY and compare results to theoretical predictions for pressure support, while pPXF is used to fit stellar absorption features. Four of the six galaxies are classified as disks, with two having known group members. These disks show elevated gas velocity dispersions relative to z $\sim$ 0 disks, consistent with interpolated trends between z $\sim$ 0 and z > 1. The results support marginally stable gaseous disks where gravitational instability still contributes alongside stellar feedback, with tentative evidence for a dynamically hotter warm ionised phase relative to cold gas ($σ_{0, Hβ} \sim 1.7 \times σ_{0, CO}$). We derive an average dark matter fraction $\langle f_{DM} \rangle = 0.42\pm0.14$, consistent with observations at similar redshifts, stellar masses, and surface densities. This work demonstrates the value of self-consistent, multi-wavelength analyses for probing disk settling physics in a relatively unexplored redshift range.

astro-ph.GA↗