arXiv subjects

Edoardo Borsato

Publications and source records attributed to Edoardo Borsato.

6 recordsLinked to original sources

arXiv2026

Vz-GAL Dusty Star-Forming Galaxies: Revisiting the CO-H2 Conversion Factor Tension

The CO luminosity-to-H$_2$ mass conversion factor ($α_{CO}$) remains a debated uncertainty in determining molecular gas masses of high-redshift dusty star-forming galaxies (DSFGs). Dynamical mass constraints have often favored $α_{CO}=0.8$~$M_{\odot}~{(K~km~{s}^{-1}~{pc}^{2})}^{-1}$, whereas dust- and radiative-transfer-based methods imply higher values. We revisit this ``tension" using the largest homogeneous sample of 21 unlensed $z\sim1-4$ DSFGs, with securely measured \coonezero luminosities from the VLA \vzgal survey and resolved ($\sim{0.1}^{\prime\prime}$) ALMA 1~mm dust continuum imaging. For 12 galaxies with robust modeling constraints, we derive molecular gas masses using dust spectral energy distribution modeling and the TUNER LVG framework, adopting a solar-metallicity gas-to-dust mass ratio of 100. Although not fully independent due to shared assumptions on dust properties, these approaches yield mutually consistent gas masses corresponding to $α_{CO}\sim1.5-11.5$, with a median near the Galactic $α_{CO}=4.3$. Isotropic virial dynamical masses agree with these gas masses when realistic molecular gas sizes are adopted, while our proposed ``mixed" (rotating, pressure-supported, thick-disk) estimator systematically underestimates dynamical masses, producing low $α_{CO}$ limits. Using GN20 ($z=4.055$) as a case study, we show that resolved gas geometry and kinematics reconcile the discrepancy with LVG-derived $α_{CO}$. Our results suggest that current data do not require $α_{CO}=0.8$, and intermediate to near-Galactic values remain dynamically viable given uncertainties in gas geometry, dust properties, and gas-to-dust ratios. Further progress in calibrating $α_{CO}$ in the early universe will require resolved molecular gas observations, physically motivated ISM modeling, and stringent constraints on dust properties.

astro-ph.GA↗

arXiv2026

The onset of stellar bars at Cosmic Noon. Bar-driven quenching and AGN co-evolution in a mature disc galaxy

Observations with the JWST revealed an unexpected abundance of barred galaxies at Cosmic Noon. However, the physical properties of these early bars are almost unconstrained, as it is their impact in the structural evolution of high-z disc galaxies. In this work, we derived the stellar populations of EGS-24154, a barred spiral galaxy at $z=1.17$. First, we investigated the role of the stellar bar in the early assembly history and structural evolution of the galaxy. Second, we studied the properties of the interstellar medium to shed light on the interplay with the central supermassive black hole. We analysed medium-resolution NIRSpec/IFS data of EGS-24154 through full-spectral fitting and derived light and mass-weighted ages and metallicities. We then reconstructed the spatially-resolved SFH, derived the ionizing mechanisms of the interstellar medium analysing several emission lines, characterized the dynamics of EGS-24154, and constrained the properties of a biconical outflow launched by the AGN. EGS-24154 is a baryon-dominated, gas-rich disc galaxy, which grew more than 90% of its stellar mass when the Universe was ~2 Gyr old. We found that the stellar population of the bar started to form at $z\sim5$, compatibly to the time when the stellar disc started to assemble. We observed a star formation desert in the bar region, which is responsible for quenching star formation over several Gyr. We then interpreted that the feedback from the AGN prevented the growth of central mass concentration, allowing the stellar bar to grow in size and strength. In this first study of spatially-resolved stellar populations of a barred disc galaxy at $z>1$, we demonstrated how stellar bars are key drivers of the early structural and dynamical evolution of disc galaxies. In particular, our results call for a revision of most models of disc and bar formation in early baryon-dominated, gas-rich disc galaxies.

astro-ph.GA↗

arXiv2025

Vz-GAL: Probing Cold Molecular Gas in Dusty Star-forming Galaxies at z=1-6

We present the first results of Vz-GAL, a high-redshift CO(J=1-0) large survey with the Karl G. Jansky Very Large Array, targeting 92 Herschel-selected, infrared-luminous, dusty star-forming galaxies (DSFGs) at redshifts 1 to 6. These sources are selected based on having redshifts and mid/high-J CO transitions from the NOrthern Extended Millimeter Array z-GAL survey. We successfully detect CO(J=1-0) emission in 90/92 galaxies at the expected positions and redshifts, including 9 tentative detections at $2σ- 3σ$ significance, and CO(J=2-1) emission in 10 of these galaxies. The CO(J=1-0) luminosities suggest apparent gas masses in the range $μ{M}_{\rm H_2}$ = $(2-20) \times {10}^{11}~(α_{CO}/{4.0})~\mathrm{M_{\odot}}$, which implies gas depletion times of $(50-600)$ Myr. These timescales show similar spread as local ULIRGs, suggesting a self-regulatory mechanism that maintains a consistent SFR per unit gas mass in starbursts across redshifts. To quantify the contribution of "excitation correction" factors to gas mass estimates, we calculate median CO line brightness temperature ratios of $r_{21}=0.88\pm0.25$, $r_{31}=0.61\pm0.22$, $r_{41}=0.49\pm0.15$, $r_{51}=0.47\pm0.13$, and $r_{61}=0.28\pm0.13$. Accounting for these corrections results in a reduced scatter in 'gas mass$-$star formation rate' relations. We also find a median log(${L}^{\prime}_{\mathrm{[CI]}(^{3}P_1 - ^{3}P_0)}/{L}^{\prime}_{\mathrm{CO}(J=1-0)})=-0.71\pm0.12$ for a subsample of 23 sources, consistent with the ratios derived for local star-forming galaxies. Together, our findings are in agreement with common conditions in the cold gas reservoirs among star-forming galaxies over a broad range in star formation modes, efficiencies, and scales.

astro-ph.GA↗

arXiv2024

The onset of bar formation in a massive galaxy at $z \sim 3.8$

We examine the morphological and kinematical properties of SPT-2147, a strongly lensed, massive, dusty, star-forming galaxy at $z = 3.762$. Combining data from JWST, HST, and ALMA, we study the galaxy's stellar emission, dust continuum and gas properties. The imaging reveals a central bar structure in the stars and gas embedded within an extended disc with a spiral arm-like feature. The kinematics confirm the presence of the bar and of the regularly rotating disc. Dynamical modeling yields a dynamical mass, ${M}_{\rm dyn} = (9.7 \pm 2.0) \times 10^{10}$ ${\rm M}_{\odot}$, and a maximum rotational velocity to velocity dispersion ratio, $V / σ= 9.8 \pm 1.2$. From multi-band imaging we infer, via SED fitting, a stellar mass, ${M}_{\star} = (6.3 \pm 0.9) \times 10^{10}$ $\rm{M}_{\odot}$, and a star formation rate, ${\rm SFR} = 781 \pm 99$ ${\rm M_{\odot} yr^{-1}}$, after correcting for magnification. Combining these measurements with the molecular gas mass, we derive a baryonic-to-total mass ratio of ${M}_{\rm bar} / {M}_{\rm dyn} = 0.9 \pm 0.2$ within 4.0 kpc. This finding suggests that the formation of bars in galaxies begins earlier in the history of the Universe than previously thought and can also occur in galaxies with elevated gas fractions.

astro-ph.GA↗

arXiv2023

Characterisation of Herschel-selected strong lens candidates through HST and sub-mm/mm observations

We have carried out HST snapshot observations at 1.1 $μ$m of 281 candidate strongly lensed galaxies identified in the wide-area extragalactic surveys conducted with the Herschel space observatory. Our candidates comprise systems with flux densities at $500\,μ$m$ S_{500}\geq 80$ mJy. We model and subtract the surface brightness distribution for 130 systems, where we identify a candidate for the foreground lens candidate. After combining visual inspection, archival high-resolution observations, and lens subtraction, we divide the systems into different classes according to their lensing likelihood. We confirm 65 systems to be lensed. Of these, 30 are new discoveries. We successfully perform lens modelling and source reconstruction on 23 systems, where the foreground lenses are isolated galaxies and the background sources are detected in the HST images. All the systems are successfully modelled as a singular isothermal ellipsoid. The Einstein radii of the lenses and the magnifications of the background sources are consistent with previous studies. However, the background source circularised radii (between 0.34 kpc and 1.30 kpc) are $\sim$3 times smaller than the ones measured in the sub-mm/mm for a similarly selected and partially overlapping sample. We compare our lenses with those in the SLACS survey, confirming that our lens-independent selection is more effective at picking up fainter and diffuse galaxies and group lenses. This sample represents the first step towards characterising the near-IR properties and stellar masses of the gravitationally lensed dusty star-forming galaxies.

astro-ph.GA↗

arXiv2020

GMNet: Graph Matching Network for Large Scale Part Semantic Segmentation in the Wild

The semantic segmentation of parts of objects in the wild is a challenging task in which multiple instances of objects and multiple parts within those objects must be detected in the scene. This problem remains nowadays very marginally explored, despite its fundamental importance towards detailed object understanding. In this work, we propose a novel framework combining higher object-level context conditioning and part-level spatial relationships to address the task. To tackle object-level ambiguity, a class-conditioning module is introduced to retain class-level semantics when learning parts-level semantics. In this way, mid-level features carry also this information prior to the decoding stage. To tackle part-level ambiguity and localization we propose a novel adjacency graph-based module that aims at matching the relative spatial relationships between ground truth and predicted parts. The experimental evaluation on the Pascal-Part dataset shows that we achieve state-of-the-art results on this task.

cs.CV↗