Browsing by Author "Afruni, A."
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- ItemDirectly constraining the spatial coherence of the z ∼ 1 circumgalactic medium(2023) Afruni, A.; Lopez, S.; Anshul, P.; Tejos, N.; Noterdaeme, P.; Berg, T. A. M.; Ledoux, C.; Solimano, M.; Gonzalez-Lopez, J.; Gronke, M.; Barrientos Parra, Luis Felipe; Johnston, E. J.One of the biggest puzzles regarding the circumgalactic medium (CGM) is the structure of its cool (T ∼ 104 K) gas phase. While the kinematics of quasar absorption systems suggests the CGM is composed of a population of different clouds, constraining their extent and spatial distribution has proven challenging, both from theoretical and observational points of view. In this work, we study the spatial structure of the z ∼ 1 CGM with unprecedented detail via resolved spectroscopy of giant gravitational arcs. We put together a sample of Mg IIλλ2796, 2803 detections obtained with VLT/MUSE in 91 spatially independent and contiguous sight lines toward 3 arcs, each probing an isolated star-forming galaxy believed to be detected in absorption. We constrain the coherence scale of this gas (Clength) - which represents the spatial scale over which the Mg II equivalent width (EW) remains constant - by comparing EW variations measured across all sight lines with empirical models. We find 1.4 < Clength/kpc < 7.8 (95% confidence). This measurement, of unprecedented accuracy, represents the scale over which the cool gas tends to cluster in separate structures. We argue that, if Clength is a universal property of the CGM, it needs to be reproduced by current and future theoretical models in order for us to understand the exact role of this medium in galaxy evolution....
- ItemMapping the spatial extent of H I-rich absorbers using Mg II absorption along gravitational arcs(2025) Berg, T. A. M.; Afruni, A.; Ledoux, C.; López, S.; Noterdaeme, P.; Tejos, N.; Hernández Guajardo, Joaquín Aléxis; Barrientos, Luis Felipe; Johnston, E. J.H I-rich absorbers seen within quasar spectra contain the bulk of neutral gas in the Universe. However, the spatial extent of these reservoirs are not extensively studied due to the pencil beam nature of quasar sightlines. Using two giant gravitational arc fields (at redshifts 1.17 and 2.06) as 2D background sources with known strong Mg II absorption observed with the Multi Unit Spectroscopic Explorer integral field spectrograph (IFS), we investigated whether spatially mapped Mg II absorption can predict the presence of strong H I systems, and determine both the physical extent and H I mass of the two absorbing systems. We created a simple model of an ensemble of gas clouds in order to simultaneously predict the H I column density and gas covering fraction of H I-rich absorbers based on observations of the Mg II rest-frame equivalent width in IFS spaxels. We first test the model on the lensing field with H I observations already available from the literature, finding that we can recover H I column densities consistent with the previous estimates (although with large uncertainties). We then use our framework to simultaneously predict the gas covering fraction, H I column density and total H I gas mass (MHI) for both fields. We find that both of the observed strong systems have a covering fraction of ≈ 70% and are likely damped Lyman α systems (DLAs) with MHI > 109 M⊙. Our model shows that the typical Mg II metrics used in the literature to identify the presence of DLAs are sensitive to the gas covering fraction. However, these Mg II metrics are still sensitive to strong H I, and can be still applied to absorbers towards gravitational arcs or other spatially extended background sources. Based on our results, we speculate that the two strong absorbers are likely representative of a neutral inner circumgalactic medium and are a significant reservoir of fuel for star formation within the host galaxies.
- ItemMolecular gas budget of strongly magnified low-mass star-forming galaxies at cosmic noon(2024) Catán Valenzuela, Victoria Sofia; González López, Jorge; Solimano Gambardella, Manuel Antonio; Barrientos, Luis Felipe; Afruni, A.; Aravena, M.; Bayliss, M.; Hernández, J. A.; Ledoux, C.; Mahler, G.; Sharon, K.; Tejos, N.Aims. The aim of this study is to investigate the molecular gas content of strongly magnified low-mass star-forming galaxies (SFGs) around the cosmic noon period (z ∼ 2) through observations of carbon monoxide (CO) emission lines and dust continuum emission, both of which serve as tracers of molecular gas (H2). Methods. We observed 12 strongly lensed arcs with the Atacama Compact Array (ACA) to detect CO mid-J rotational transitions and dust continuum. Thanks to the strong lensing, we were able to probe the previously understudied low-mass regime. With a compiled set of observations, we recalibrated empirical relations between star formation rate density (ΣSFR) and the CO line ratios. We derived galaxy properties using spectral energy distribution fitting (SED). We also performed galaxy stacking to combine faint signals. In all cases, molecular gas masses were estimated using both tracers. Results. We detected CO emission in 3 of the 12 arcs and dust continuum emission in another 3. The obtained H2 masses indicate that most of these galaxies (M* < 1010.7 M⊙) have lower molecular gas fractions and shorter depletion times compared to expectations from established scaling relations at these redshifts. We explored several possible explanations for this gas deficit, including uncertainties in mass estimates, effects of low-metallicity environments, larger atomic gas reservoirs in low-mass systems, and the possibility that these represent low-mass analogs of main sequence starburst (MS SBs) galaxies that are undergoing sustained star formation due to gas compaction despite low overall gas fractions. Conclusions. We conclude that these mass and metallicity regimes present a molecular gas deficit. Our results suggest that this deficit is likely due to a significant amount of atomic gas, which our stacking indicates is about 91% of the total gas. However, this estimation might be an upper limit, as the possibility remains that our galaxies contain CO-dark gas.
- ItemOrientation effects on cool gas absorption from gravitational-arc tomography of a z=0.77 disc galaxy(2022) Fernandez-Figueroa, A.; Lopez, S.; Tejos, N.; Berg, T. A. M.; Ledoux, C.; Noterdaeme, P.; Afruni, A.; Barrientos, L. F.; Gonzalez-Lopez, J.; Hamel, M.; Johnston, E. J.; Katsianis, A.; Sharon, K.; Solimano, M.We use spatially resolved spectroscopy of a distant giant gravitational arc to test orientation effects on Mg ii absorption equivalent width (EW) and covering fraction () in the circumgalactic medium of a foreground star-forming galaxy (G1) at z similar to 0.77. Forty-two spatially-binned arc positions uniformly sample impact parameters (D) to G1 between 10 and 30 kpc and azimuthal angles alpha between 30 degrees and 90 degrees (minor axis). We find an EW-D anticorrelation, akin to that observed statistically in quasar absorber studies, and an apparent correlation of both EW and with alpha, revealing a non-isotropic gas distribution. In line with our previous results on Mg ii kinematics suggesting the presence of outflows in G1, at minimum a simple 3D static double-cone model (to represent the trace of bipolar outflows) is required to recreate the EW spatial distribution. The D and alpha values probed by the arc cannot confirm the presence of a disc, but the data highly disfavour a disc alone. Our results support the interpretation that the EW-alpha correlation observed statistically using other extant probes is partly shaped by bipolar metal-rich winds.
- ItemTransverse clues on the kiloparsec-scale structure of the circumgalactic medium as traced by C IV absorption(2024) López, Sebastián; Afruni, A.; Zamora Hidalgo, Diego Amaro; Tejos, Nicolás; Ledoux, Cédric; Hernández Guajardo, Joaquín Alexis; Berg, Trystyn A. M.; Cortés Muñoz, Hugo R.; Urbina Jiménez, Francisco; Johnston, E. J.; Barrientos, Luis Felipe; Bayliss, M. B.; Cuellar, Rodrigo; Krogager, Jens-Kristian; Noterdaeme, Pasquier; Solimano, ManuelThe kiloparsec-scale kinematics and density structure of the circumgalactic medium (CGM) is still poorly constrained observationally, which poses a problem for understanding the role of the baryon cycle in galaxy evolution. Here we present VLT/MUSE integral-field spectroscopy (R ≈ 1800) of four giant gravitational arcs exhibiting W0 ≳ 0.2 Å C IV absorption at eight intervening redshifts, zabs ≈ 2.0–2.5. We detected C IV absorption in a total of 222 adjacent and seeing-uncorrelated sight lines whose spectra sample beams of ("de-lensed") linear size ≈1 kpc. Our data show that (1) absorption velocities cluster at all probed transverse scales, Δr⊥ ≈ 0–15 kpc, depending on system; (2) the (transverse) velocity dispersion never exceeds the mean (line-of-sight) absorption spread; and (3) the (transverse) velocity autocorrelation function does not resolve kinematic patterns at the above spatial scales, but its velocity projection, ξarc(Δv), exhibits a similar shape to the known two-point correlation function toward quasars, ξQSO(Δv). An empirical kinematic model suggests that these results are a natural consequence of wide-beam observations of an unresolved clumpy medium. Our model recovers both the underlying velocity dispersion of the clumps (70–170 km s‑1) and the mean number of clumps per unit area (2–13 kpc‑2). The latter constrains the projected mean inter-clump distance to within ≈0.3–0.8 kpc, which we argue is a measure of clump size for a near-unity covering fraction. The model is also able to predict ξarc(Δv) from ξQSO(Δv), suggesting that the strong systems that shape ξarc(Δv) and the line-of-sight velocity components that define ξQSO(Δv) trace the same kinematic population. Consequently, the clumps must possess an internal density structure that generates both weak and strong components. We discuss how our interpretation is consistent with previous observations using background galaxies and multiple quasars as well as its implications for the connection between the small-scale kinematic structure of the CGM and galactic-scale accretion and feedback processes....