Context. Bars are elongated structures developed by a large fraction of disk galaxies in their central few kiloparsecs. However, the bar formation process is still not fully understood, particularly the role played by the galaxy environment in the formation and evolution of these structures. Aims. The aim of this work is to establish how the galaxy environment affects the evolution of bars by analyzing the bar structural parameters in a sample of galaxies located in three different galaxy environments: in the Virgo cluster, in filaments in the Cosmic Web around it, and in the field. Methods. We performed structural analysis using optical imaging from the DESI Legacy survey, measuring bar radii and disk scale lengths through Fourier analysis and surface brightness fitting techniques. Results. After defining a homogeneous sample of barred galaxies across the three different galaxy environments in terms of color and magnitude, the median bar radii were found to be 2.54 +/- 0.34 kpc, 3.29 +/- 0.38 kpc, and 4.44 +/- 0.81 kpc in the cluster, filaments, and field environments, respectively. In addition, the median bar radii scaled by the disk scale lengths were found to be 1.26 +/- 0.09, 1.72 +/- 0.11, and 2.57 +/- 0.21 in the cluster, filaments, and field environments, respectively. These results indicate that the galaxy environment has a significant influence on the structural parameters of bars, with bars in high-density environments being shorter and less prominent than those in the field. Conclusions. Our findings can be interpreted in terms of a slowing of the secular evolution of bars in dense galaxy environments. Barred galaxies located in clusters could experience a reduced rate of bar secular evolution due to various physical processes that occur in high-density environments, such as gas stripping, strangulation, or tidal interactions.

Context. Solar wavefront sensing has been a challenge for astrophysical instrumentalists, due to the low contrast between the Sun and the sky background compared to night-time observations, which limits the performance of adaptive optics systems. Aims. Wavefront correction in solar physics requires the analysis of extended images; meanwhile, at night the displacement of a punctual object is analysed. This technique limits the spatial resolution, and therefore the accuracy in the wavefront reconstruction. Methods. To solve this problem, a new method of direct wavefront sensing without the need for image formation was explored for this work. A novel and promising technology called integrated photonics was used to accomplish this task. It allows the direct measurement of phase differences across the wavefront without the need to form images, using the principle of interferometry. This technology offers a low-consumption, miniaturised solution to astrophysical problems. Results. For this work a mathematical model was derived to characterise the behaviour of the proposed wavefront sensor. The proposed system was verified and simulated using a Python-based adaptive optics simulator. These simulations demonstrate the physical behaviour of the proposed wavefront sensor and highlight the factors that must be taken into account for its correct functioning.

Galaxies form and evolve within the diverse environments of the cosmic web. However, disentangling the effects of internal properties, local environments, and large-scale structures (LSS) on galaxy evolution involvessignificant complexities, since these effects are frequently overlapping. The aim of this work is to provide evidence of the imprints left by LSS on galaxy properties by selecting samples of galaxies from different environments, while matching their intrinsic characteristics. We investigate the effects of the LSS on the g-r colour and star formation rate (SFR) in galaxies with stellar mass M > 10^10 M_⊙, with the redshift 0.05 ≤ z ≤ 0.1, and selected from the SDSS DR16. We use a catalogue of the LSS available in the literature to define samples of galaxies located in field and filament environments. Galaxies located in the field tend to exhibit bluer g-r stellar colours and higher SFR than those in filaments. These differences persist even in samples of galaxies matched by mass and galaxy local overdensity, indicating that they are not produced by internal processes. These differences cannot be attributed to variations in morphology. There is also a variation in stellar colour and SFR with distance to the filaments (Df). The SFR of galaxies becomes statistically smaller than that of field galaxies for objects located at Df<5 Mpc, while changes in stellar colour occur at smaller distances (Df<1 Mpc). This could indicates that the typical filament width is about 2.5-5 Mpc. The variations in colour and SFR between galaxy samples in the field and in filaments, with matched masses and local overdensities, indicate that large-scale environmental factors drive these transformations rather than local or internal galaxy properties. These transformations are not strong enough to produce changes in galaxy morphology. They could be explained by cosmic web starvation.

Dwarf barred galaxies are the perfect candidates for hosting slowly-rotating bars. They are common in dense environments and they have a relatively shallow potential well, making them prone to heating by interactions. When an interaction induces bar formation, the bar should rotate slowly. They reside in massive and centrally-concentrated dark matter halos, which slow down the bar rotation through dynamical friction. While predictions suggest that slow bars should be common, measurements of bar pattern speed, using the Tremaine-Weinberg method, show that bars are mostly fast in the local Universe. We present a photometric and kinematic characterisation of bars hosted by two dwarf galaxies in the Virgo Cluster, NGC 4483 and NGC 4516. We derive the bar length and strength using the Next Generation Virgo Survey imaging and the circular velocity, bar pattern speed, and rotation rate using spectroscopy from the Multi Unit Spectroscopic Explorer. Including the previously studied galaxy IC 3167, we compare the bar properties of the three dwarf galaxies with those of their massive counterparts from literature. Bars in the dwarf galaxies are shorter and weaker, and rotate slightly slower with respect to those in massive galaxies. This could be due to a different bar formation mechanism and/or to a large dark matter fraction in the centre of dwarf galaxies. We show that it is possible to push the application of the Tremaine-Weinberg method to the galaxy low mass regime.

In this paper, the redshift evolution of the galactic bar properties, like the bar length, pattern speed, and bar fraction, has been investigated for simulated galaxies at stellar masses of M-* > 10(10) M-circle dot in the cosmological magnetohydrodynamical simulation TNG50. We focus on the redshift evolution of the bar pattern speeds and the fast bar tension. We show that the median value of the pattern speed of the bars increases as the redshift grows. On the other hand, although the median value of the bar length increases with time, the ratio between the corotation radius and the bar radius - namely, the R = R-CR/R-bar parameter - increases as well. In other words, the corotation radius increases with a higher rate than the bar length. This directly means that galactic bars slow down with time, or equivalently as the redshift declines. We discuss the possible mechanisms that reduce the pattern speeds in TNG50. We demonstrate that while mergers can have a significant impact on a galaxy's pattern speed, they do not play a crucial role in the overall evolution of mean pattern speed within the redshift range z <= 1.0. Furthermore, we show that the R parameter does not correlate with the gas fraction. Consequently, the existence of gas in TNG50 does not alleviate the fast bar tension. We show that the mean value of the pattern speed, computed for all the galaxies irrespective of their mass, at z = 1.0 is Omega(p) = 70.98 +/- 2.34 km s(-1) kpc(-1) and reduces to Omega(p) = 33.65 +/- 1.07 km s(-1) kpc(-1) at z = 0.0. This is a direct prediction by TNG50 that bars at z = 1.0 rotate faster by a factor of similar to 2 compared to bars at z = 0.0.

The distribution of moving groups in the solar neighborhood has been used to constrain dynamical properties of the Milky Way for decades. The kinematic bimodality between the main mode (Hyades, Pleiades, Coma Berenices, and Sirius) and Hercules can be explained by two different bar models – via the outer Lindblad resonance of a bar with a high pattern speed (∼55 km s^-1 kpc^-1), or via the corotation resonance of a bar with a low pattern speed (∼40 km s^-1 kpc^-1). Recent works directly studying the kinematics of bar stars and gas flows near the center of the Galaxy have converged on the low pattern speed model. In this paper, we independently confirm this result by using Gaia DR3 to directly study the variation of Hercules across Galactic azimuth. We find that Hercules increases in V_ϕ and becomes stronger as we move towards the minor axis of the bar, and decreases in V_ϕ and becomes weaker as we move towards the major axis of the bar. This is in direct agreement with theoretical predictions of a low pattern speed bar model in which Hercules is formed by the corotation resonance with stars orbiting the bar's L4/L5 Lagrange points.

We present a detailed study of the large-scale shock front in Stephan's Quintet, a by-product of past and ongoing interactions. Using integral-field spectroscopy from the new William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE), recent 144 MHz observations from the LOFAR Two-metre Sky Survey, and archival data from the Very Large Array and JWST, we obtain new measurements of key shock properties and determine its impact on the system. Harnessing the WEAVE large integral field unit's field of view (90 x 78 arcsec(2)), spectral resolution (R similar to 2500), and continuous wavelength coverage across the optical band, we perform robust emission-line modelling and dynamically locate the shock within the multiphase intergalactic medium with higher precision than previously possible. The shocking of the cold gas phase is hypersonic, and comparisons with shock models show that it can readily account for the observed emission-line ratios. In contrast, we demonstrate that the shock is relatively weak in the hot plasma visible in X-rays (with Mach number of M similar to 2-4), making it inefficient at producing the relativistic particles needed to explain the observed synchrotron emission. Instead, we propose that it has led to an adiabatic compression of the medium, which has increased the radio luminosity 10-fold. Comparison of the Balmer line-derived extinction map with the molecular gas and hot dust observed with JWST suggests that pre-existing dust may have survived the collision, allowing the condensation of H-2 - a key channel for dissipating the shock energy.

ABSTRACT WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, saw first light in late 2022. WEAVE comprises a new 2-deg field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable ‘mini’ integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366–959 nm at R ∼ 5000, or two shorter ranges at $R\sim 20\, 000$. After summarizing the design and implementation of WEAVE and its data systems, we present the organization, science drivers, and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy’s origins by completing Gaia’s phase-space information, providing metallicities to its limiting magnitude for ∼3 million stars and detailed abundances for ∼1.5 million brighter field and open-cluster stars; (ii) survey ∼0.4 million Galactic-plane OBA stars, young stellar objects, and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ∼400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionized gas in z < 0.5 cluster galaxies; (vi) survey stellar populations and kinematics in ${\sim} 25\, 000$ field galaxies at 0.3 ≲ z ≲ 0.7; (vii) study the cosmic evolution of accretion and star formation using >1 million spectra of LOFAR-selected radio sources; and (viii) trace structures using intergalactic/circumgalactic gas at z > 2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.

Galaxies undergo numerous transformative processes throughout their lifetimes that ultimately lead to the expulsion of gas and the cessation of star-forming activity. This phenomenon is commonly known as quenching, and in this study, we delve into the possibility that this process is caused by the environmental processes associated with the surrounding cluster. To this end, we used the results of our previous paper - where we analyzed dwarf galaxies in the SAMI-Fornax survey together with massive galaxies from the ATLAS(3D) survey - to compute the quenching time of each galaxy and compare it with the infall time into the cluster. Using t(90) as an approximation of the quenching time and deriving the infall time from phase-space models, we determined the probability of the quenching being produced by the local environment of galaxies. Our results reveal a relation between galaxy mass and quenching probability. Massive galaxies, down to M-star similar to 10(10)M(circle dot), exhibit a low, almost zero probability of quenching, suggesting their independence of environmental effects. As we move into the mass regime of dwarf galaxies, the probability increases with decreasing mass, highlighting their sensitivity to environmental quenching. For dwarfs, 36 +/- 9% of our observational data are consistent with this hypothesis, challenging the idea that the present-day cluster, Fornax, is the primary driver of quenching in the low-mass galaxies of our sample with stellar mass from 10(7) to 10(9)M(circle dot). To further investigate the importance of environmental processes, we compared these results with cosmological simulations, selecting galaxies under similar conditions to our observational sample. Remarkably, the simulated sample shows lower quenching probabilities as we move down in mass, and barely 5 +/- 1% of galaxies meet the quenching criteria. This discrepancy between observations and simulations underlines the fact that the modelling of quenching is still in its infancy. In general, the number of observed galaxies quenched by their environment is lower than expected, which suggests that preprocessing plays a larger role in galaxy evolution. Ultimately, our results highlight the need for higher-quality simulations and refinement of galaxy formation and evolution models.

ABSTRACT Recent advances in the stellar population studies of unresolved galaxies in the NIR domain demonstrated that it contains several line-strength indices to be potentially used as diagnostics for stellar population properties. Reduction of the extinction and possibility to disentangle different stellar populations dominating different spectral ranges are obviously beneficial. To this aim, we have investigated the connections between 19 Lick/IDS indices and 39 NIR indices measured in the central regions of 32 galaxies observed with X-shooter. We adopted a systematic approach to deriving a correlation matrix using all the optical and NIR indices measured for the galaxies and building new NIR composite indices to maximize their correlations with the best age and metallicity optical tracers. We found that the new T1 and [AlFeCr] composite indices are promising age and metallicity diagnostics in NIR, respectively. We finally tested the T1 and [AlFeCr] indices with the predictions of simple stellar populations models, and we found that the models show a general agreement with the data. Some fine tuning and further comparison between models and data, which are now largely available, is necessary to reach the prediction level of the optical line-strength indices.

ABSTRACT We present a study on the star formation histories (SFHs) of galaxies covering the range 104 < M⋆/M⊙ < 1012, leveraging full spectral fitting algorithms. Our sample consists of 31 dwarf galaxies from the SAMI-Fornax Survey with stellar masses between 107–$10^{9.5} \, {\rm M}_{\odot }$, early-type galaxies from the ATLAS3D project with stellar masses between 1010–$10^{12} \, {\rm M}_{\odot }$, and dwarf galaxies that are satellites of Andromeda and the Milky Way, with 104 < M⋆/M⊙ < 108. We find that galaxies from 107–$10^{8} \, {\rm M}_{\odot }$ exhibit the smallest star formation rates (SFRs), while the SFR increase as we move down or up in mass. In this sense, we find that some $10^{5} \, {\rm M}_{\odot }$ galaxies have cumulative SFHs that are comparable to those of $10^{12} \, {\rm M}_{\odot }$ galaxies. Our study shows that the evolution of giant galaxies is primarily governed by their internal properties, with time-scales that do not depend on their environmental location. In contrast, dwarf galaxies below $10^{8} \, {\rm M}_{\odot }$ can be significantly affected in dense environments, such as the inner regions of a cluster, that severely quench the galaxies before the assembly of their 50 per cent present-day mass. We find that, only dwarfs with stellar masses between 107–$10^{9} \, {\rm M}_{\odot }$ actively form stars nowadays, while less massive galaxies seem to remain unaffected by the environment due to the expulsion of most of their gas at an early stage in their evolution. Our study highlights and corroborates a critical threshold around $10^{8}-10^{9} \, {\rm M}_{\odot }$ in galaxy evolution from previous studies, separating more massive galaxies minimally impacted by the environment from those less massive galaxies quenched by it.

Barred structures are widespread in a considerable fraction of galactic discs, spanning diverse environments and galaxy luminosities. The environment likely exerts a significant influence on bar formation. It is plausible that the structural parameters of bars resulting from tidal interactions in high-density galactic environments differ from those formed through internal disc instabilities in isolated galaxies. To empirically test this scenario, a viable approach is to compare the structural parameters of bars in galaxies situated within distinct environments. We have collected data on the bar radius and bar strength for a sample of 36 SB0 and SBa galaxies located within the Virgo cluster. Additionally, we analyzed a sample of 46 field galaxies with similar morphologies and luminosity range. The analysis reveals that the bar radius exhibits a correlation with galaxy luminosity, indicating that larger bars are typically found in more luminous galaxies. When comparing galaxies with fixed luminosities, the field galaxies display larger bar radii compared to those in the Virgo cluster. However, when the bar radius is scaled by the size of the galaxy, the disparity diminishes and the scaled bars in the Virgo cluster and the field exhibit similar sizes. This is because galaxies of similar luminosities tend to be larger in the field environment compared to the cluster and because the bars adapt to the discs in which they live. Regarding the bar strength, no significant differences were observed for bright galaxies ($M_{r} < -19.5$) between those located in the Virgo cluster and those in the field. In contrast, faint galaxies ($M_{r} > -19.5$) show stronger bars in the field than in the cluster.

ABSTRACT Using very deep, high spectral resolution data from the SAMI Integral Field Spectrograph, we study the stellar population properties of a sample of dwarf galaxies in the Fornax Cluster, down to a stellar mass of 107 M⊙, which has never been done outside the Local Group. We use full spectral fitting to obtain stellar population parameters. Adding massive galaxies from the ATLAS3D project, which we re-analysed, and the satellite galaxies of the Milky Way, we obtained a galaxy sample that covers the stellar mass range 104–1012 M⊙. Using this large range, we find that the mass–metallicity relation is not linear. We also find that the [α/Fe]-stellar mass relation of the full sample shows a U-shape, with a minimum in [α/Fe] for masses between 109 and 1010 M⊙. The relation between [α/Fe] and stellar mass can be understood in the following way: when the faintest galaxies enter the cluster environment, a rapid burst of star formation is induced, after which the gas content is blown away by various quenching mechanisms. This fast star formation causes high [α/Fe] values, like in the Galactic halo. More massive galaxies will manage to keep their gas longer and form several bursts of star formation, with lower [α/Fe] as a result. For massive galaxies, stellar populations are regulated by internal processes, leading to [α/Fe] increasing with mass. We confirm this model by showing that [α/Fe] correlates with clustercentric distance in three nearby clusters and also in the halo of the Milky Way.

Context. Barred structures are widespread in a considerable fraction of galactic disks, spanning diverse environments and galaxy luminosities. The environment likely exerts a significant influence on bar formation, with tidal interactions leading to the emergence of elongated features resembling bars within galaxy disks. It is plausible that the structural parameters of bars resulting from tidal interactions in high-density galactic environments differ from those that formed through internal disk instabilities in isolated galaxies. To empirically test this scenario, a viable approach is to compare the structural parameters of bars in galaxies situated within distinct environments. Aims. The objective of this study is to study environmental effects on the properties of bars by conducting a comparison between the two key structural parameters of bars, namely strength and radius, in galaxies situated within the Virgo cluster and galaxies of comparable luminosities found in environments characterized by lower galaxy densities. Methods. We have collected data on the bar radius and bar strength for a sample of 36 SB0 and SBa galaxies located within the Virgo cluster. These galaxies exhibit a large range of magnitudes, with values ranging from Mr = −22 to Mr = −17. Additionally, we analyzed a sample of 46 field galaxies with similar morphologies and luminosity ranges. The measurements of bar parameters were conducted by employing Fourier decomposition on the r-band photometric images of the galaxies. Results. The analysis reveals that the bar radius exhibits a correlation with the galaxy luminosity, indicating that larger bars are typically found in more luminous galaxies. When comparing galaxies with fixed luminosities, the field galaxies display larger bar radii compared to those in the Virgo cluster. However, when the bar radius is scaled by the size of the galaxy, the disparity diminishes and the scaled bars in the Virgo cluster and the field exhibit similar sizes. This is because galaxies of similar luminosities tend to be larger in the field environment compared to the cluster and because the bars adapt to the disks in which they live. Regarding the bar strength, no significant differences were observed for bright galaxies (Mr < −19.5) between those located in the Virgo cluster and those in the field. In contrast, faint galaxies (Mr > −19.5) show stronger bars in the field than in the cluster. Conclusions. The findings of this study indicate that the size of galaxies is the parameter that is influenced by the environment, while the bar radius remains independent of the environment when scaled by the galaxy size. The findings of this study indicate that the environment influences the size of galaxies rather than the bar radius, which remains independent of the environment when scaled by the galaxy size. Regarding the bar strength, there is no influence of the environment for bright galaxies. However, bars in faint galaxies are weaker in the cluster environment. This could be explained by an enhancement of disk thickness in dense environments which is more efficient in faint galaxies. These results support the notion that the internal dynamics and intrinsic characteristics of galaxies play a dominant role in the formation and evolution of bars, regardless of the surrounding environment.

The kinematic plane of stars near the Sun has proven an indispensable tool for untangling the complexities of the structure of our Milky Way (MW). With ever improving data, numerous kinematic "moving groups" of stars have been better characterized and new ones continue to be discovered. Here we present an improved method for detecting these groups using MGwave, a new open-source 2D wavelet transformation code that we have developed. Our code implements similar techniques to previous wavelet software; however, we include a more robust significance methodology and also allow for the investigation of underdensities which can eventually provide further information about the MW's non-axisymmetric features. Applying MGwave to the latest data release from Gaia (DR3), we detect 47 groups of stars with coherent velocities. We reproduce the majority of the previously detected moving groups in addition to identifying three additional significant candidates: one within Arcturus, and two in regions without much substructure at low V_R. Finally, we have followed these associations of stars beyond the solar neighborhood, from Galactocentric radius of 6.5 to 10 kpc. Most detected groups are extended throughout radius indicating that they are streams of stars possibly due to non-axisymmetric features of the MW.

Context. Recent studies show that barred galaxies have a light deficit, called a dark gap (DG), in the direction of the bar minor axis with respect to the major axis. The properties of these DGs might be related to the properties of the bars and to the location of some resonances of the galaxies. Aims. We have analyzed the evolution of the DGs properties in the barred galaxy of the GALAKOS simulation to compare them with those from real galaxies and infer conclusions about the evolutionary status of the bars. Methods. The DGs were measured by using the bar and the interbar surface brightness profiles from the Fourier decomposition of the light of the galaxies. We characterized them by two parameters: the prominence of the DG (Δμmax), and its location in the galaxy (RDG). Results. In the GALAKOS simulation, both Δμmax and RDG evolve with time. Thus, the DGs are more prominent and are located at larger radii as the bar evolves. In addition, RDG is smaller than the bar radius (Rb) at all time steps of the simulation, being always Rb/RDG > 1.2. About 90% of the real galaxies show Rb/RDG > 1.2 similar to the GALAKOS simulation. For these objects, the ratio of the corrotation radius (RCR) and the DG radius is RCR/RDG ≈ 1.8. This is similar to the expected ratio of the corrotation resonance (CR) and the ultraharmonic resonance (UHR) radius. This indicates a link between the DGs and the UHR of these galaxies. The remaining 10% of the galaxies show Rb/RDG < 1.2 and RCR/RDG ≈ 1. In these cases, the DG would be linked with the CR of the galaxy. We have found that the bar in GALAKOS, as well as real bars in galaxies, can be located in distinct places on the RCR/h − Rb/h plane based on the prominence of their DGs. In particular, galaxies with high values of Δμmax are located at RCR/h and Rb/h larger than 1.5. The simulated bar turned to be a slow rotator when Δμmax was larger than 0.8. When this occurs, RCR/h and Rb/h are larger than 2.0 and 1.5, respectively, for the GALAKOS bar. Conclusions. The location of the DG seems to be a robust signature of the location of the galaxy resonances. In addition, the prominence of the DG could be used as indicators of the amount of angular momentum exchange by the bar and other galactic components. Galaxies with Δμmax > 0.8 would be candidates for slow bar rotators. In addition, flat bars would be more evolved or would have exchanged more angular momentum than exponential bars.

ABSTRACT We investigate the link between the bar rotation rate and dark matter content in barred galaxies by concentrating on the cases of the lenticular galaxies NGC 4264 and NGC 4277. These two gas-poor galaxies have similar morphologies, sizes, and luminosities. But, NGC 4264 hosts a fast bar, which extends to nearly the corotation, while the bar embedded in NGC 4277 is slow and falls short of corotation. We derive the fraction of dark matter fDM, bar within the bar region from Jeans axisymmetric dynamical models by matching the stellar kinematics obtained with the MUSE integral-field spectrograph and using SDSS images to recover the stellar mass distribution. We build mass-follows-light models as well as mass models with a spherical halo of dark matter, which is not tied to the stars. We find that the inner regions of NGC 4277 host a larger fraction of dark matter ($f_{\rm DM, bar}\, =\, 0.53\pm 0.02$) with respect to NGC 4264 ($f_{\rm DM, bar}\, =\, 0.33\pm 0.04$) in agreement with the predictions of theoretical works and the findings of numerical simulations, which have found that fast bars live in baryon-dominated discs, whereas slow bars experienced a strong drag from the dynamical friction due to a dense DM halo. This is the first time that the bar rotation rate is coupled to fDM, bar derived from dynamical modelling.

In this work we study the large-scale structure around a sample of non-fossil systems and compare the results with earlier findings for a sample of genuine fossil systems selected using their magnitude gap. We compute the distance from each system to the closest filament and intersection as obtained from a catalogue of galaxies in the redshift range $0.05 \le z \le 0.7$. We then estimate the average distances and distributions of cumulative distances to filaments and intersections for different bins of magnitude gap. We find that the average distance to filaments is $(3.0\pm 0.8)$ $R_{200}$ for fossil systems, whereas it is $(1.1\pm 0.1)\,R_{200}$ for non-fossil systems. Similarly, the average distance to intersections is larger in fossil than in non-fossil systems, with values of $(16.3\pm 3.2)$ and $(8.9\pm 1.1) \,R_{200}$, respectively. Moreover, the cumulative distributions of distances to intersections are statistically different between fossil and non-fossil systems. Fossil systems selected using the magnitude gap appear to be, on average, more isolated from the cosmic web than non-fossil systems. No dependence is found on the magnitude gap (i.e. non-fossil systems behave in a similar manner independently of their magnitude gap and only fossils are found at larger average distances from the cosmic web). This result supports a formation scenario for fossil systems in which the lack of infalling galaxies from the cosmic web, due to their peculiar position, favours the building of the magnitude gap via the merging of all the massive satellites with the central galaxy. Comparison with numerical simulations suggests that fossil systems selected using the magnitude gap are not old fossils of the ancient Universe, but systems located in regions of the cosmic web not influenced by the presence of intersections.

The distribution of moving groups in the solar neighborhood has been used to constrain dynamical properties of the Milky Way for decades. The kinematic bimodality between the main mode (Hyades, Pleiades, Coma Berenices, and Sirius) and Hercules can be explained by two different bar models -- via the outer Lindblad resonance of a bar with a high pattern speed ($\sim$55 km s$^{-1}$ kpc$^{-1}$), or via the corotation resonance of a bar with a low pattern speed ($\sim$40 km s$^{-1}$ kpc$^{-1}$). Recent works directly studying the kinematics of bar stars and gas flows near the center of the Galaxy have converged on the low pattern speed model. In this paper, we independently confirm this result by using Gaia DR3 to directly study the variation of Hercules across Galactic azimuth. We find that Hercules increases in $V_\phi$ and becomes stronger as we move towards the minor axis of the bar, and decreases in $V_\phi$ and becomes weaker as we move towards the major axis of the bar. This is in direct agreement with theoretical predictions of a low pattern speed bar model in which Hercules is formed by the corotation resonance with stars orbiting the bar's L4/L5 Lagrange points.

Aims. In this work we study the large-scale structure around a sample of non-fossil systems and compare the results with earlier findings for a sample of genuine fossil systems selected using their magnitude gap. Methods. We computed the distance from each system to the closest filament and intersection as obtained from a catalogue of galaxies in the redshift range 0.05 ≤ z ≤ 0.7. We then estimated the average distances and the distributions of cumulative distances to filaments and intersections for different magnitude-gap bins. Results. We find that the average distance to filaments is (3.0 ± 0.8) R 200 for fossil systems, whereas it is (1.1 ± 0.1) R 200 for non-fossil systems. Similarly, the average distance to intersections is larger in fossil than in non-fossil systems, with values of (16.3 ± 3.2) and (8.9 ± 1.1) R 200 , respectively. Moreover, the cumulative distributions of distances to intersections are statistically different for fossil and non-fossil systems. Conclusions. Fossil systems selected using the magnitude gap appear to be, on average, more isolated from the cosmic web than non-fossil systems. No dependence is found on the magnitude gap (i.e. non-fossil systems behave in a similar manner independently of their magnitude gap, and only fossils are found at larger average distances from the cosmic web). This result supports a formation scenario for fossil systems in which the lack of infalling galaxies from the cosmic web, due to their peculiar position, favours the growing of the magnitude gap via the merging of all the massive satellites with the central galaxy. Comparison with numerical simulations suggests that fossil systems selected using the magnitude gap are not old fossils of the ancient Universe, but rather systems located in regions of the cosmic web not influenced by the presence of intersections.