arXiv subjects

Sebastiano Cantalupo

Publications and source records attributed to Sebastiano Cantalupo.

At least 55 records · Page 3Linked to original sources

arXiv2024

MUSEQuBES: Mapping the distribution of neutral hydrogen around low-redshift galaxies

We present a detailed study of cool, neutral gas traced by Lya around 4595 z<0.5 galaxies using stacks of background quasar spectra. The galaxies are selected from our MUSEQuBES low-z survey along with data from the literature. These galaxies, with a median stellar mass of log (M*/Msun)= 10.0, are probed by 184 background quasars giving rise to 5054 quasar-galaxy pairs. The median impact parameter is b = 1.5 pMpc (median b/Rvir=10.4) with 204 (419) quasar-galaxy pairs probing b/Rvir < 1 (2). We find excess absorption out to at least ~ 15 Rvir transverse distance and ~ 600 km/s along the line of sight. We show that the median stacked profile for the full sample, dominated by the pairs with b > Rvir, can be explained by a galaxy-absorber two-point correlation function with r0 = 7.6 pMpc and gamma = -1.57. There are strong indications that the inner regions (< Rvir) of the rest equivalent width profile are better explained by a log-linear (or a Gaussian) relation whereas the outer regions are well described by a power-law, consistent with galaxy-absorber large-scale clustering. Using a sub-sample of 339 galaxies (442 quasar-galaxy pairs, median b/Rvir = 1.6) with star formation rate measurements, we find that the Lya absorption is significantly stronger for star-forming galaxies compared to passive galaxies, but only within the virial radius. The Lya absorption at b ~ Rvir for a redshift-controlled sample peaks at M* ~ 10^9 Msun~ (Mhalo ~ 10^11 Msun).

astro-ph.GA↗

arXiv2024

An ensemble study of turbulence in extended QSO nebulae at $z\approx0.5$--1

Turbulent motions in the circumgalactic medium (CGM) play a critical role in regulating the evolution of galaxies, yet their detailed characterization remains elusive. Using two-dimensional velocity maps constructed from spatially-extended [OII] and [OIII] emission, Chen et al. (2023b) measured the velocity structure functions (VSFs) of four quasar nebulae at $z\approx\!0.5$--1.1. One of these exhibits a spectacular Kolmogorov relation. Here we carry out an ensemble study using an expanded sample incorporating four new nebulae from three additional QSO fields. The VSFs measured for all eight nebulae are best explained by subsonic turbulence revealed by the line-emitting gas, which in turn strongly suggests that the cool gas ($T\!\sim\!10^4$ K) is dynamically coupled to the hot ambient medium. Previous work demonstrates that the largest nebulae in our sample reside in group environments with clear signs of tidal interactions, suggesting that environmental effects are vital in seeding and enhancing turbulence within the gaseous halos, ultimately promoting the formation of the extended nebulae. No discernible differences are observed in the VSF properties between radio-loud and radio-quiet QSO fields. We estimate the turbulent heating rate per unit volume, $Q_{\rm turb}$, in the QSO nebulae to be $\sim 10^{-26}$--$10^{-22}$ erg cm$^{-3}$ s$^{-1}$ for the cool phase and $\sim 10^{-28}$--$10^{-25}$ erg cm$^{-3}$ s$^{-1}$ for the hot phase. This range aligns with measurements in the intracluster medium and star-forming molecular clouds but is $\sim10^3$ times higher than the $Q_{\rm turb}$ observed inside cool gas clumps on scales $\lesssim1$ kpc using absorption-line techniques. We discuss the prospect of bridging the gap between emission and absorption studies by pushing the emission-based VSF measurements to below $\approx\!10$ kpc.

astro-ph.GA↗

arXiv2023

Bipolar Outflows out to 10~kpc for Massive Galaxies at Redshift $z\approx 1$

Galactic outflows are believed to play a critical role in the evolution of galaxies by regulating their mass build-up and star formation. Theoretical models assumes bipolar shapes for the outflows that extends well into the circumgalctic medium (CGM), up to tens of kpc perpendicular to the galaxies. They have been directly observed in the local Universe in several individual galaxies, e.g., around the Milky Way and M82. At higher redshifts, cosmological simulations of galaxy formation predict an increase in the frequency and efficiency of galactic outflows due to the increasing star formation activity. Outflows are responsible for removing potential fuel for star formation from the galaxy, while at the same enriching the CGM and the intergalactic medium. These feedback processes, although incorporated as key elements of cosmological simulations, are still poorly constrained on CGM scales. Here we present an ultra-deep MUSE image of the mean MgII emission surrounding a sample of galaxies at z~1 that strongly suggests the presence of outflowing gas on physical scales of more than 10kpc. We find a strong dependence of the detected signal on the inclination of the central galaxy, with edge-on galaxies clearly showing enhanced MgII emission along the minor axis, while face-on galaxies display much weaker and more isotropic emission. We interpret these findings as supporting the idea that outflows typically have a bipolar cone geometry perpendicular to the galactic disk. We demonstrate that the signal is not dominated by a few outliers. After dividing the galaxy sample in subsamples by mass, the bipolar emission is only detected in galaxies with stellar mass $\mathrm{M_* \gtrsim 10^{9.5} M_\odot}$.

astro-ph.GA↗

arXiv2023

The first comprehensive study of a giant nebula around a radio-quiet quasar in the $z < 1$ Universe

We present the first comprehensive study of a giant, $\approx \! \! 70$ kpc-scale nebula around a radio-quiet quasar at $z<1$. The analysis is based on deep integral field spectroscopy with MUSE of the field of HE$\,$0238$-$1904, a luminous quasar at $z=0.6282$. The nebula emits strongly in $\mathrm{[O \, II]}$, $\rm H β$, and $\mathrm{[O \, III]}$, and the quasar resides in an unusually overdense environment for a radio-quiet system. The environment likely consists of two groups which may be merging, and in total have an estimated dynamical mass of $M_{\rm dyn}\approx 4\times 10^{13}$ to $10^{14}\ {\rm M_\odot}$. The nebula exhibits largely quiescent kinematics and irregular morphology. The nebula may arise primarily through interaction-related stripping of circumgalactic and interstellar medium (CGM/ISM) of group members, with some potential contributions from quasar outflows. The simultaneous presence of the giant nebula and a radio-quiet quasar in a rich environment suggests a correlation between such circum-quasar nebulae and environmental effects. This possibility can be tested with larger samples. The upper limits on the electron number density implied by the $\mathrm{[O \, II]}$ doublet ratio range from $\log(n_{\rm e, \, [O \, II]} / \mathrm{cm^{-3}}) < 1.2$ to $2.8$. However, assuming a constant quasar luminosity and negligible projection effects, the densities implied from the measured line ratios between different ions (e.g., $\mathrm{[O\,II]}$, $\mathrm{[O\,III]}$, and $\mathrm{[Ne\,V]}$) and photoionization simulations are often $10{-}400$ times larger. This large discrepancy can be explained by quasar variability on a timescale of $\approx 10^4{-}10^5$ years.

astro-ph.GA↗

arXiv2023

The Cosmic Ultraviolet Baryon Survey: Empirical Characterization of Turbulence in the Cool Circumgalactic Medium

This paper reports the first measurement of the relationship between turbulent velocity and cloud size in the diffuse circumgalactic medium (CGM) in typical galaxy halos at redshift z~0.4-1. Through spectrally-resolved absorption profiles of a suite of ionic transitions paired with careful ionization analyses of individual components, cool clumps of size as small as l_cl~1 pc and density lower than nH = 0.001 cm^-3 are identified in galaxy halos. In addition, comparing the line widths between different elements for kinematically matched components provides robust empirical constraints on the thermal temperature T and the non-thermal motions bNT, independent of the ionization models. On average, bNT is found to increase with l_cl following bNT \propto l_cl^0.3 over three decades in spatial scale from l_cl~1 pc to l_cl~1 kpc. Attributing the observed bNT to turbulent motions internal to the clumps, the best-fit bNT-l_cl relation shows that the turbulence is consistent with Kolmogorov at <1 kpc with a roughly constant energy transfer rate per unit mass of epsilon~0.003 cm^2 s^-3 and a dissipation time scale of <~ 100 Myr. No significant difference is found between massive quiescent and star-forming halos in the sample on scales less than 1 kpc. While the inferred epsilon is comparable to what is found in CIV absorbers at high redshift, it is considerably smaller than observed in star-forming gas or in extended line-emitting nebulae around distant quasars. A brief discussion of possible sources to drive the observed turbulence in the cool CGM is presented.

astro-ph.GA↗

arXiv2023

Resolving the physics of Quasar Ly$α$ Nebulae (RePhyNe): I. Constraining Quasar host halo masses through Circumgalactic Medium kinematics

Ly$α$ nebulae ubiquitously found around z>2 quasars can supply unique constraints on the properties of the Circumgalactic Medium, such as its density distribution, provided the quasar halo mass is known. We present a new method to constrain quasar halo masses based on the line-of-sight velocity dispersion maps of Ly$α$ nebulae. By using MUSE-like mock observations obtained from cosmological hydrodynamic simulations under the assumption of maximal quasar fluorescence, we show that the velocity dispersion radial profiles of Ly$α$-emitting gas are strongly determined by gravity and that they are thus self-similar with respect to halo mass when rescaled by the virial radius. Through simple analytical arguments and by exploiting the kinematics of HeII1640Ȧ emission for a set of observed nebulae, we show that Ly$α$ radiative transfer effects plausibly do not change the shape of the velocity dispersion profiles but only their normalisation without breaking their self-similarity. Taking advantage of these results, we define the variable $η^{140-200}_{40-100}$ as the ratio of the median velocity dispersion in two specifically selected annuli and derive an analytical relation between $η^{140-200}_{40-100}$ and the halo mass which can be directly applied to observations. We apply our method to 37 observed quasar Ly$α$ nebulae at 3<z<4.7 and find that their associated quasars are typically hosted by ~$10^{12.16 \pm 0.14}$ M$_{\odot}$ haloes independent of redshift within the explored range. This measurement, which is completely independent of clustering methods, is consistent with the lowest mass estimates based on quasar auto-correlation clustering at z~3 and with quasar-galaxies cross-correlation results.

astro-ph.GA↗

arXiv2023

NGC 2992: The interplay between the multiphase disk, wind and radio bubbles

We present an analysis of the gas kinematics in NGC 2992, based on VLT/MUSE, ALMA and VLA data, aimed at characterising the disk, the wind and their interplay in the cold molecular and warm ionised phases. CO(2-1) and H$\rm α~$ arise from a multiphase disk with inclination 80 deg and radii 1.5 and 1.8 kpc, respectively. We find that the velocity dispersion of the cold molecular phase is consistent with that of star forming galaxies at the same redshift, except in the inner 600 pc region, and in the region between the cone walls and the disk. This suggests that a disk-wind interaction locally boosts the gas turbulence. We detect a clumpy ionised wind distributed in two wide opening angle ionisation cones reaching scales of 7 kpc. The [O III] wind expands with velocity exceeding -1000 km/s in the inner 600 pc, a factor of 5 larger than the previously reported wind velocity. Based on spatially resolved electron density and ionisation parameter maps, we infer an ionised outflow mass of $M_{\rm of,ion} = (3.2 \pm 0.3) \times \, 10^7 \, M_{\odot}$, and a total ionised outflow rate of $\dot M_{\rm of,ion}=13.5\pm1$ \sfr. We detected clumps of cold molecular gas located above and below the disk reaching maximum projected distances and velocities of 1.7 kpc and 200 km/s, respectively. On these scales, the wind is multiphase, with a fast ionised component and a slower molecular one, and a total mass of $M_{\rm of, ion+mol}= 5.8 \times 10^7 \, M_{\odot}$, of which the molecular component carries the bulk of the mass. The dusty molecular outflowing clumps and the turbulent ionised gas are located at the edges of the radio bubbles, suggesting that the bubbles interact with the surrounding medium through shocks. We detect a dust reservoir co-spatial with the molecular disk, with a cold dust mass $M_{\rm dust} = (4.04 \pm 0.03) \times \, 10^{6} \, M_{\odot}$.

astro-ph.GA↗

arXiv2023

MUSEQuBES: The relation between Ly$α$ emitters and C IV absorbers at $z \approx 3.3$

We present a detailed study of the column density and covering fraction profiles of C IV absorption around 86 redshift $z \approx 3.3$ Ly$α$ emitters (LAEs) detected in 8 Multi-Unit Spectroscopic Explorer (MUSE) fields of $1'\times 1'$ centered on 8 bright background quasars as part of the MUSEQuBES survey. Using Voigt profile fitting of all the C IV absorbers detected along these 8 sightlines, we generated a ``blind'' absorbers' catalog consisting of 489 C IV absorption components. We cross-matched this blind C IV catalog with the MUSE-detected LAE catalog and found a significant enhancement of C IV components within $\approx \pm$400 $\rm km\, s^{-1}$ of the systemic redshifts of the LAEs. Neither the C IV column density ($N$) nor the Doppler parameter ($b$) of individual C IV components shows any significant anti-correlation with impact parameter ($ρ$) of the LAEs in the 68 percentile range of $90\leq ρ\leq 230$ physical kpc (pkpc). We find a covering fraction of $\approx 60\%$ for a threshold $N$(C IV) of $10^{12.5}\, \rm \rm cm^{-2}$, which is roughly twice as high as in random regions. The C IV covering fraction remains constant at $\approx50\%$ for impact parameters in the range 150--250~pkpc ($\approx 3-6 R_{200}$). Using the covering fraction profile, we constrained the LAE--C IV absorber two-point correlation function, and obtained $r_0 = 3.4$ comoving Mpc (cMpc) and $γ= 1.2$ for a threshold $N$(C IV) of $10^{13.0}\, \rm cm^{-2}$. The C IV covering fraction is found to be enhanced for the LAEs that are part of a ``pair/group'' compared to the isolated ones.

astro-ph.GA↗

arXiv2023

The Cosmic Ultraviolet Baryon Survey (CUBS) VI: Connecting Physical Properties of the Cool Circumgalactic Medium to Galaxies at $z\approx 1$

This paper presents a new sample of 19 unique galaxies and galaxy groups at $z\approx1$ from the CUBS program, which is designated as the CUBSz1 sample. In this CUBSz1 sample, nine galaxies or galaxy groups show absorption features, while ten systems do not have detectable absorption with 2-$σ$ upper limits of log$N$(HeI)/cm$^{-2}\lesssim 13.5$ and log$N$(OV)/cm$^{-2}\lesssim 13.3$. Environmental properties of the galaxies, including galaxy overdensities, the total stellar mass and gravitational potential summed over all nearby neighbors, and the presence of local ionizing sources, are found to have a significant impact on the observed CGM absorption properties. Specifically, massive galaxies and galaxies in overdense regions exhibit a higher rate of incidence of absorption. At the same time, the observed CGM absorption properties in galaxy groups appear to be driven by the galaxy closest to the QSO sightline, rather than by the most massive galaxy or by mass-weighted properties. We introduce a total projected gravitational potential $ψ$, defined as $-ψ/G =\sum M_{\rm halo}/d_{\rm proj}$ summed over all group members, to characterize the overall galaxy environment. This projected gravitational potential correlates linearly with the maximum density detected in each sightline, consistent with higher-pressure gas being confined in deeper gravitational potential wells. In addition, we find that the radial profile of cool gas density exhibits a general decline from the inner regions to the outskirts, being in pressure balance with the hot halo. Finally, we note that the ionizing flux from nearby galaxies can generate an elevated $N$(HI)/$N$(HeI) ratio, which in turn provides a unique diagnostic of possible local sources contributing to the ionizing radiation field.

astro-ph.GA↗

arXiv2023

On the evolution of the size of Lyman alpha halos across cosmic time: no change in the circumgalactic gas distribution when probed by line emission

Lyman $α$ (Ly$α$) is now routinely used as a tool for studying high-redshift galaxies and its resonant nature means it can trace neutral hydrogen around star-forming galaxies. Integral field spectrograph measurements of high-redshift Ly$α$ emitters indicate that significant extended Ly$α$ halo emission is ubiquitous around such objects. We present a sample of redshift 0.23 to 0.31 galaxies observed with the Hubble Space Telescope selected to match the star formation properties of high-$z$ samples while optimizing the observations for detection of low surface brightness Ly$α$ emission. The Ly$α$ escape fractions range between 0.7\% and 37\%, and we detect extended Ly$α$ emission around six out of seven targets. We find Ly$α$ halo to UV scale length ratios around 6:1 which is marginally lower than high-redshift observations, and halo flux fractions between 60\% and 85\% -- consistent with high-redshift observations -- when using comparable methods. However, our targets show additional extended stellar UV emission: we parametrize this with a new double exponential model. We find that this parametrization does not strongly affect the observed Ly$α$ halo fractions. We find that deeper H$α$ data would be required to firmly determine the origin of Ly$α$ halo emission, however, there are indications that H$α$ is more extended than the central FUV profile, potentially indicating conditions favorable for the escape of ionizing radiation. We discuss our results in the context of high-redshift galaxies, cosmological simulations, evolutionary studies of the circumgalactic medium in emission, and the emission of ionizing radiation.

astro-ph.GA↗

arXiv2023

Metal line emission from galaxy haloes at z~1

We present a study of the metal-enriched halo gas, traced using MgII and [OII] emission lines, in two large, blind galaxy surveys - the MUSE (Multi Unit Spectroscopic Explorer) Analysis of Gas around Galaxies (MAGG) and the MUSE Ultra Deep Field (MUDF). By stacking a sample of ~600 galaxies (stellar masses M* ~10^{6-12} Msun), we characterize for the first time the average metal line emission from a general population of galaxy haloes at 0.7 <= z <= 1.5. The MgII and [OII] line emission extends farther out than the stellar continuum emission, on average out to ~25 kpc and ~45 kpc, respectively, at a surface brightness (SB) level of 10^{-20} erg/s/cm2/arcsec2. The radial profile of the MgII SB is shallower than that of the [OII], suggesting that the resonant MgII emission is affected by dust and radiative transfer effects. The [OII] to MgII SB ratio is ~3 over ~20-40 kpc, also indicating a significant in situ origin of the extended metal emission. The average SB profiles are intrinsically brighter by a factor ~2-3 and more radially extended by a factor of ~1.3 at 1.0 < z <= 1.5 than at 0.7 <= z <= 1.0. The average extent of the metal emission also increases independently with increasing stellar mass and in overdense group environments. When considering individual detections, we find extended [OII] emission up to ~50 kpc around ~30-40 percent of the group galaxies, and extended (~30-40 kpc) MgII emission around two z~1 quasars in groups, which could arise from outflows or environmental processes.

astro-ph.GA↗

arXiv2023

Characterizing the Circumgalactic Medium of Quasars at z $\sim$ 2.2 through H$α$ and Ly$α$ Emission

The discovery of giant quasar Ly$α$ nebulae at $z>2$ has opened up the possibility to directly study in emission the Circumgalactic and Intergalactic Medium (CGM/IGM). However, the resonant nature of the Ly$α$ line and its different emission mechanisms hamper the ability to constrain both the kinematics and physical properties of the CGM/IGM. Here, we present results of a pilot project aiming at the detection of CGM H$α$ emission, a line which does not suffer from these limitations. To this end, we first used KCWI to detect Ly$α$ emission around three bright quasars with $2.25 10^{12}$M$_{\odot}$).

astro-ph.GA↗

arXiv2023

Modelling gas around galaxy pairs and groups using the Q0107 quasar triplet

We examine to what extent disk and outflow models can reproduce observations of H I gas within a few virial radii of galaxies in pairs and groups. Using highly-sensitive HST/COS and FOS spectra of the Q0107 quasar triplet covering Ly$α$ for z$\lesssim$1, as well as a deep galaxy redshift survey including VIMOS, DEIMOS, GMOS and MUSE data, we test simple disk and outflow models against the H I absorption along three lines-of-sight (separated by 200-500 kpc) through nine galaxy groups in this field. These can be compared with our previous results in which these models can often be fit to the absorption around isolated galaxies. Our models can reproduce $\approx$ 75$\%$ of the 28 identified absorption components within 500 km/s of a group galaxy, so most of the H I around groups is consistent with a superposition of the CGM of the individual galaxies. Gas stripped in interactions between galaxies may be a plausible explanation for some of the remaining absorption, but neither the galaxy images nor the galaxy and absorber kinematics provide clear evidence of such stripped material, and these unexplained absorbers do not preferentially occur around close pairs of galaxies. We find H I column densities typically higher than at similar impact parameters around isolated galaxies ($\approx$ 2.5$σ$), as well as more frequent detections of O VI than around isolated galaxies (30$\%$ of sightlines to 7$\%$).

astro-ph.GA↗

arXiv2023

MUSE Analysis of Gas around Galaxies (MAGG) -- V: Linking ionized gas traced by CIV and SiIV absorbers to Ly$α$ emitting galaxies at $z\approx 3.0-4.5$

We use 28 quasar fields with high-resolution (HIRES and UVES) spectroscopy from the MUSE Analysis of Gas Around Galaxies survey to study the connection between Ly$α$ emitters (LAEs) and metal-enriched ionized gas traced by CIV in absorption at redshift $z\approx3-4$. In a sample of 220 CIV absorbers, we identify 143 LAEs connected to CIV gas within a line-of-sight separation ${\rm \pm 500\,km\,s^{-1}}$, equal to a detection rate of $36\pm 5$ per cent once we account for multiple LAEs connected to the same CIV absorber. The luminosity function of LAEs associated with CIV absorbers shows a $\approx 2.4$ higher normalization factor compared to the field. CIV with higher equivalent width and velocity width are associated with brighter LAEs or multiple galaxies, while weaker systems are less often identified near LAEs. The covering fraction in groups is up to $\approx 3$ times larger than for isolated galaxies. Compared to the correlation between optically-thick HI absorbers and LAEs, CIV systems are twice less likely to be found near LAEs especially at lower equivalent width. Similar results are found using SiIV as tracer of ionized gas. We propose three components to model the gas environment of LAEs: i) the circumgalactic medium of galaxies, accounting for the strongest correlations between absorption and emission; ii) overdense gas filaments connecting galaxies, driving the excess of LAEs at a few times the virial radius and the modulation of the luminosity and cross-correlation functions for strong absorbers; iii) an enriched and more diffuse medium, accounting for weaker CIV absorbers farther from galaxies.

astro-ph.GA↗

arXiv2022

Directly tracing cool filamentary accretion over >100 kpc into the interstellar medium of a quasar host at z=1

We report the discovery of giant (50-100 kpc) [O II] emitting nebulae with the Multi-Unit Spectroscopic Explorer (MUSE) in the field of TXS 0206-048, a luminous quasar at z=1.13. Down-the-barrel UV spectra of the quasar show absorption at velocities coincident with those of the extended nebulae, enabling new insights into inflows and outflows around the quasar host. One nebula exhibits a filamentary morphology extending over 120 kpc from the halo toward the quasar and intersecting with another nebula surrounding the quasar host with a radius of 50 kpc. This is the longest cool filament observed to-date and arises at higher redshift and in a less massive system than those in cool-core clusters. The filamentary nebula has line-of-sight velocities >300 km/s from nearby galaxies but matches that of the nebula surrounding the quasar host where they intersect, consistent with accretion of cool inter- or circum-galactic medium or cooling hot halo gas. The kinematics of the nebulae surrounding the quasar host are unusual and complex, with redshifted and blueshifted spiral-like structures. The emission velocities at 5-10 kpc from the quasar match those of inflowing absorbing gas observed in UV spectra of the quasar. Together, the extended nebulae and associated redshifted absorption represent a compelling case of cool, filamentary gas accretion from halo scales into the extended interstellar medium and toward the nucleus of a massive quasar host. The inflow rate implied by the combined emission and absorption constraints is well below levels required to sustain the quasar's radiative luminosity, suggesting anisotropic or variable accretion.

astro-ph.GA↗

arXiv2022

Empirical constraints on the turbulence in QSO host nebulae from velocity structure function measurements

We present the first empirical constraints on the turbulent velocity field of the diffuse circumgalactic medium around four luminous QSOs at $z\!\approx\!0.5$--1.1. Spatially extended nebulae of $\approx\!50$--100 physical kpc in diameter centered on the QSOs are revealed in [OII]$λλ\,3727,3729$ and/or [OIII]$λ\,5008$ emission lines in integral field spectroscopic observations obtained using MUSE on the VLT. We measure the second- and third-order velocity structure functions (VSFs) over a range of scales, from $\lesssim\!5$ kpc to $\approx\!20$--50 kpc, to quantify the turbulent energy transfer between different scales in these nebulae. While no constraints on the energy injection and dissipation scales can be obtained from the current data, we show that robust constraints on the power-law slope of the VSFs can be determined after accounting for the effects of atmospheric seeing, spatial smoothing, and large-scale bulk flows. Out of the four QSO nebulae studied, one exhibits VSFs in spectacular agreement with the Kolmogorov law, expected for isotropic, homogeneous, and incompressible turbulent flows. The other three fields exhibit a shallower decline in the VSFs from large to small scales. However, with a limited dynamic range in the spatial scales in seeing-limited data, no constraints can be obtained for the VSF slopes of these three nebulae. For the QSO nebula consistent with the Kolmogorov law, we determine a turbulence energy cascade rate of $\approx\!0.2$ cm$^{2}$ s$^{-3}$. We discuss the implication of the observed VSFs in the context of QSO feeding and feedback in the circumgalactic medium.

astro-ph.GA↗

arXiv2022

Rediscovering Practice and Inquiry in Academic Education: Experiences in a European University Environment

I describe the design and implementation of a series of university MSc courses in Switzerland and in Italy on the topic of Cosmic Structure Formation whose goal has been to provide to the students a formative experience using interwoven research practice and fundamental scientific content. The course educational framework, which is based on the ISEE Inquiry Framework, emphasizes science, as much in teaching as in research, as a set of practices, rediscovering and actualizing in modern terms the original pivotal role which these practices had in education in ancient times. In particular, the courses focus on formative, intuitive, student-centered and dialogic learning in opposition to the informative, mnemonic, teacher-centered and monologic teaching of frontal lecture based instruction, which is still the dominant teaching framework in university education, at least in Europe. I describe how course activities are designed in such a way as to mirror authentic research, including all aspects which are usually not practiced in lecture-based courses and standard laboratories (e.g., generating and refining questions; making and testing assumptions; developing one's own research path; and sharing, explaining and justifying ideas and results with peers). Finally, I discuss the major outcomes of the courses and the main challenges which were faced in order to provide to the students a truly transformative experience which could allow them to improve both as learners and future scientific researchers, as well as members of a larger community.

physics.ed-ph↗

arXiv2022

MUSE Analysis of Gas around Galaxies (MAGG) -- IV: The gaseous environment of $z\sim$ 3-4 Lyman-alpha emitting galaxies

We study the link between galaxies and HI-selected absorption systems at z~3-4 in the MUSE Analysis of Gas around Galaxies (MAGG) survey, an ESO large programme consisting of integral field pectroscopic observations of 28 quasar fields hosting 61 strong absorbers with $\rm N_{\rm HI}\gtrsim 10^{16.5}~\rm cm^{-2}$. We identify 127 Ly$α$ emitting galaxies (LAEs) around the absorbers, corresponding to a detection rate of 82$\pm$16 per cent. The luminosity function of these LAEs is approximately 5 times higher in normalization than the field population and we detect a significant clustering of galaxies with respect to the gas, confirming that high column density absorbers and LAEs trace each other. Between 30 and 40 per cent of the absorbers are associated with multiple LAEs, which lie preferentially along filaments. Galaxies in groups also exhibit a three times higher covering factor of optically-thick gas compared to isolated systems. No significant correlations are identified between the emission properties of LAEs and the absorption properties of optically-thick gas clouds, except for a weak preference of brighter and multiple galaxies to reside near broad absorbers. Based on the measured impact parameters and the covering factor, we conclude that the near totality of optically-thick gas in the Universe can be found in the outer circumgalactic medium (CGM) of LAEs or in the intergalactic medium (IGM) in proximity to these galaxies. Thus, LAEs act as tracers of larger scale structures within which both galaxies and optically-thick clouds are embedded. The patchy and inhomogeneous nature of the CGM and IGM explains the lack of correlations between absorption and emission properties. This implies that very large samples are needed to unveil the trends that encode the properties of the baryon cycle.

astro-ph.GA↗