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We present a spectroscopic analysis of MACS J0138$-$2155, at $z=0.336$, the first galaxy cluster hosting two strongly-lensed supernovae (SNe), Requiem and Encore, providing us with a chance to obtain a reliable $H_0$ measurement from the time delays between the multiple images. We take advantage of new data from the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope, covering a central $1 \rm \, arcmin^2$ of the lensing cluster, for a total depth of 3.7 hours, including 2.9 hours recently obtained by our Target of Opportunity programme. Our new spectroscopic catalogue contains reliable redshifts for 107 objects, including 50 galaxy cluster members with secure redshift values in the range $0.324 < z < 0.349$, and 13 lensed multiple images from four background sources between $0.767\leq z \leq 3.420$, including four images of the host galaxy of the two SNe. We exploit the MUSE data to study the stellar kinematics of 14 bright cluster members and two background galaxies, obtaining reliable measurements of their line-of-sight velocity dispersion. Finally, we combine these results with measurements of the total magnitude of the cluster members in the Hubble Space Telescope F160W band to calibrate the Faber-Jackson relation between luminosity and stellar velocity dispersion ($L \propto \sigma^{1/\alpha}$) for the early-type cluster member galaxies, measuring a slope $\alpha=0.25^{+0.05}_{-0.05}$. A pure and complete sample of cluster member galaxies and a reliable characterisation of their total mass structure are key to building accurate total mass maps of the cluster, mitigating the impact of parametric degeneracies, which is necessary for inferring the value of $H_0$ from the measured time delays between the lensed images of the two SNe., Comment: Sumbitted to Astronomy and Astrophysics, 13 pages, 8 figures, 3 tables

Cluster cosmology can benefit from combining multi-wavelength studies, which can benefit from characterising the correlation coefficients between different mass-observable relations. In this work, we aim to provide information on the scatter, the skewness, and the covariance of various mass-observable relations in galaxy clusters in cosmological hydrodynamic simulations. This information will help future analyses to better tackle accretion histories and projection effects and model mass observable relations for cosmology studies.We identify galaxy clusters in Magneticum Box2b simulations with mass $M_{\rm 200c}>10^{14} {\rm M}_\odot$ at redshift $z=0.24$ and $z=0.90$. Our analysis includes \Euclid-derived properties such as richness, stellar mass, lensing mass, and concentration. Additionally, we investigate complementary multi-wavelength data, including X-ray luminosity, integrated Compton-$y$ parameter, gas mass, and temperature. The impact of projection effects on mass-observable residuals and correlations is then examined. At intermediate redshift ($z=0.24$), projection effects impact lensing concentration, richness, and gas mass the most in terms of scatter and skewness of log-residuals of scaling relations. The contribution of projection effects can be significant enough to boost a spurious hot- vs. cold-baryons correlation and consequently hide underlying correlations due to halo accretion histories. At high redshift ($z=0.9$), the richness has a much lower scatter (of log-residuals), and the quantity that is most impacted by projection effects is the lensing mass. Lensing concentration reconstruction, in particular, is affected by deviations of the reduced-shear profile shape from the one derived by an NFW profile rather than interlopers in the line of sight., Comment: 26 pages, 22 figures, submitted to A&A, replied to referee comments

We present JWST/NIRSpec PRISM spectroscopic characterization of GHZ9 at z= 10.145 $\pm$ 0.010, currently the most distant source detected by the Chandra X-ray Observatory. The spectrum reveals several UV high-ionization lines, including CII, SiIV, [NIV], CIV, HeII, OIII], NIII], and CIII]. The prominent rest-frame equivalent widths (EW(CIV)$\simeq$65A, EW(HeII)$\simeq$18A, EW(CIII])$\simeq$48A) show the presence of a hard radiation field, while the analysis of line ratio diagnostics suggest this galaxy hosts both AGN and star-formation activity. GHZ9 is nitrogen-enriched (6--9.5 times solar), carbon-poor (0.2--0.65 times solar), metal-poor (Z = 0.01--0.1 Z$_{\odot}$), and compact ($<$ 106 pc), similarly to GNz11, GHZ2, and recently discovered N-enhanced high redshift objects. We exploited the newly available JWST/NIRSpec and NIRCam dataset to perform an independent analysis of the Chandra data confirming that GHZ9 is the most likely JWST source associated to X-ray emission at 0.5-7 keV. Assuming a spectral index $\Gamma$ = 2.3 (1.8), we estimate a black hole (BH) mass of 1.60 $\pm$ 0.31 (0.48 $\pm$ 0.09) $\times$ 10$^8$M$_{\odot}$, which is consistent either with Eddington-accretion onto heavy ($\geq$ 10$^6$ M$_{\odot}$) BH seeds formed at z=18, or super-Eddington accretion onto a light seed of $\sim$ 10$^2-10^4$ M$_{\odot}$ at z = 25. The corresponding BH-to-stellar mass ratio M$_{BH}$/M$_{star}$= 0.33$\pm$0.22 (0.10$\pm$0.07), with a stringent limit $>$0.02, implies an accelerated growth of the BH mass with respect to the stellar mass. GHZ9 is the ideal target to constrain the early phases of AGN-galaxy coevolution with future multi-frequency observations., Comment: Submitted to ApJ

We present JWST/NIRSpec PRISM follow-up of candidate galaxies at z=9-11 selected from deep JWST/NIRCam photometry in GLASS-JWST Early Release Science data. We spectroscopically confirm six sources with secure redshifts at z = 9.52-10.43, each showing multiple emission lines. An additional object is likely at z = 10.66, based on its Lya-break and a single emission feature, while one source is a lower redshift interloper. The sample includes the first JWST-detected candidate at z=10, GHZ1/GLASS-z10, which we confirm at z = 9.875, and the X-ray detected AGN GHZ9 confirmed at z = 10.145. Three objects in our sample, including GHZ9, have EW(CIII])>20A and occupy a region compatible with AGN emission in the EW(CIII]) vs CIV/CIII] diagram. The spectroscopic sample confirms a high abundance of galaxies at z > 9. We measure a number density of z=10 galaxies in the GLASS-JWST ERS field that is a factor of >3 higher than other JWST-based estimates at demagnified rest-frame magnitudes of -21 < Muv < -19. We find that the positions of these galaxies in redshift and angular space are not consistent with all of them being part of a unique progenitor of present-day galaxy clusters. The high density of objects in the GLASS region can be explained either by clustering on large scales or by a superposition of different forming structures of which we observe only the brightest members. By considering all the spectroscopic z=10 sources in the Abell-2744 field, we identify two potential galaxy proto-clusters centered around GHZ9 and JD1, with relative separations between their members of 1-2 pMpc. The potential AGN nature of three of the sources in our sample lends support to a scenario in which the high abundance of bright sources determined by JWST surveys at cosmic dawn may be affected by AGN contribution to their UV luminosity., Comment: Submitted to A&A

Overcoming both modeling and computational challenges, we present, for the first time, the extended surface-brightness distribution model of a strongly-lensed source in a complex galaxy-cluster-scale system. We exploit the high-resolution Hubble Space Telescope (HST) imaging and extensive Multi Unit Spectroscopic Explorer spectroscopy to build an extended strong-lensing model, in a full multi-plane formalism, of SDSS J1029+2623, a lens cluster at $z = 0.588$ with three multiple images of a background quasar ($z = 2.1992$). Going beyond typical cluster strong-lensing modeling techniques, we include as observables both the positions of 26 pointlike multiple images from seven background sources, spanning a wide redshift range between 1.02 and 5.06, and the extended surface-brightness distribution of the strongly-lensed quasar host galaxy, over $\sim78000$ HST pixels. In addition, we model the light distribution of seven objects, angularly close to the strongly-lensed quasar host, over $\sim9300$ HST pixels. Our extended lens model reproduces well both the observed intensity and morphology of the quasar host galaxy in the HST F160W band (with a 0''.03 pixel scale). The reconstructed source shows a single, compact, and smooth surface-brightness distribution, for which we estimate an intrinsic magnitude of 23.3 $\pm$ 0.1 in the F160W band and a half-light radius of (2.39 $\pm$ 0.03) kpc. The increased number of observables enables the accurate determination of the total mass of line-of-sight halos lying angularly close to the extended arc. This work paves the way for a new generation of galaxy cluster strong-lens models, where additional, complementary lensing observables are directly incorporated as model constraints., Comment: 19 pages, 9 Figures, 2 Tables. Accepted for publication in ApJ

We report the identification of two galaxy overdensities at $z\sim5.7$ in the sightline of the galaxy cluster Abell 2744. These overdensities consist of 25 and 17 member galaxies, spectroscopically confirmed with JWST NIRSpec/MSA and NIRCam/WFSS. Each overdensity has a total stellar mass of $\sim2\times10^{10} M_\odot$ and a star formation rate of $\sim200 M_\odot$/yr within a central region of radius $R=2$ Mpc (physical). The sensitive PRISM spectra allow us to identify six galaxies that show weak Ha+[NII] emissions within the overdensities ($27\pm6\%$), whereas the fraction of such galaxies is found significantly lower ($6\pm2\%$) in field samples of the equivalent redshift range. These weak emission line galaxies, dubbed as wELGs, exhibit a strong continuum break at $4000$AA rest-frame, a characteristic feature of evolved stellar populations. The high observed fraction of wELGs in the two overdensities is consistent with the idea that high-density environments are an ideal site where galaxies can accelerate their evolutionary pace compared to field analogs. Our study pinpoints an early onset of environmental effects, already important within one billion years after the Big Bang, and provides a complementary perspective on the emergence of quenched, massive galaxies at lower redshifts. Potential contributions from black hole accretion feedback to the reduction of star formation activity are discussed, but the connection to the local environments remains unclear., Comment: Submitted to ApJ

We present a detailed JWST/NIRSpec and NIRCam analysis of a gravitationally-lensed galaxy ($\rm \mu=17-21$) at redshift 6.14 magnified by the Hubble Frontier Field galaxy cluster MACS J0416. The target galaxy is overall a typical compact and UV-faint ($\rm M_{UV}=-17.8$) Lyman-$\alpha$ emitter; yet, the large magnification allows the detailed characterisation of structures on sub-galactic (down to few parsec) scales. Prominent optical $\rm H\alpha$, $\rm H\beta$ and [OIII]$\lambda\lambda4959,5007$ lines are spatially resolved with the high spectral resolution grating (G395H, R~2700), with large equivalent widths, EW($\rm H\beta$+[OIII])$\gtrsim1000$ \AA, and elevated ionising photon production efficiencies $\rm log(\xi_{ion}/erg^{-1}Hz)=25.2-25.7$. NIRCam deep imaging reveals the presence of compact rest-UV bright regions along with individual star clusters of sizes $\rm R_{eff}=3-8~pc$ and masses $\rm M\sim2\cdot10^5-5\cdot10^{6}~M_\odot$ These clusters are characterised by steep UV slopes, $\rm\beta_{UV}\lesssim-2.5$, in some cases associated with a dearth of line emission, indicating possible leaking of the ionising radiation, as also supported by a Lyman-$\rm \alpha$ emission peaking at $\rm \sim100~km~s^{-1}$ from the systemic redshift. While the entire system is characterised by low-metallicity, $\sim0.1~Z_\odot$, the NIRSpec-IFU map also reveals the presence of a low-luminosity, metal-poor region with $\rm Z\lesssim2\%~Z_\odot$, barely detected in NIRCam imaging; this region is displaced by $\rm >200~pc$ from one of the UV brightest structures of the system, and it would have been too faint to detect if not for the large magnification of the system., Comment: 19 pages (11 figures, 2 tables) + appendix (3 pages, 4 figures, 1 table). Submitted to A&A; comments are welcome

We report the serendipitous discovery of a faint (M_UV > -12.2), low-metallicity (Z ~ 0.02 Zsun), ionizing source (dubbed T2c) with a spectroscopic redshift of z=6.146. T2c is part of a larger structure amplified by the Hubble Frontier Field galaxy cluster MACSJ0416, and was observed with JWST/NIRSpec IFU. Stacking the short-wavelength NIRCam data reveals no stellar continuum detection down to a magnitude limit of m_UV ~ 31.0 (3 sigma). However, prominent Hb, [OIII]4959,5007, and Ha emissions are detected, with equivalent widths exceeding 200A, 800A, and 1300A (3 sigma), respectively. The corresponding intrinsic (magnification-corrected x23 +/- 3) ultraviolet and optical rest-frame magnitudes exceed 34.4 and 33.9 (corresponding to M_uv and M_opt fainter than -12.2 and -12.8, at lambda_rest ~ 2000A and ~5000A, respectively), suggesting a stellar mass lower than a few 10^4 Msun under an instantaneous burst scenario. The inferred ionizing photon production efficiency (xi_ion) is high, xi_ion >~ 26.08(25.86) 3(5)sigma, assuming no dust attenuation and no Lyman continuum leakage, indicating the presence of massive stars despite the low mass of the object. The very poor sampling of the initial mass function at such low mass star-forming complex suggests that the formation of very massive stars might be favored in very low metallicity environments. T2c is surrounded by Balmer and weak oxygen emission on a spatial scale of a few hundred parsecs after correcting for lensing effects. This system resembles an HII region potentially powered by currently undetected, extremely efficient, low-metallicity star complexes or clusters. We propose that massive O-type stars populate this low-mass and metallicity high-redshift satellites, likely caught in an early and short formation phase, contributing to the ionization of the surrounding medium., Comment: 9 pages, 5 figures, 1 table. Submitted to A&A. Comments are welcome

Euclid will collect an enormous amount of data during the mission's lifetime, observing billions of galaxies in the extragalactic sky. Along with traditional template-fitting methods, numerous machine learning algorithms have been presented for computing their photometric redshifts and physical parameters (PPs), requiring significantly less computing effort while producing equivalent performance measures. However, their performance is limited by the quality and amount of input information, to the point where the recovery of some well-established physical relationships between parameters might not be guaranteed. To forecast the reliability of Euclid photo-$z$s and PPs calculations, we produced two mock catalogs simulating Euclid photometry. We simulated the Euclid Wide Survey (EWS) and Euclid Deep Fields (EDF). We tested the performance of a template-fitting algorithm (Phosphoros) and four ML methods in recovering photo-$z$s, PPs (stellar masses and star formation rates), and the SFMS. To mimic the Euclid processing as closely as possible, the models were trained with Phosphoros-recovered labels. For the EWS, we found that the best results are achieved with a mixed labels approach, training the models with wide survey features and labels from the Phosphoros results on deeper photometry, that is, with the best possible set of labels for a given photometry. This imposes a prior, helping the models to better discern cases in degenerate regions of feature space, that is, when galaxies have similar magnitudes and colors but different redshifts and PPs, with performance metrics even better than those found with Phosphoros. We found no more than 3% performance degradation using a COSMOS-like reference sample or removing u band data, which will not be available until after data release DR1. The best results are obtained for the EDF, with appropriate recovery of photo-$z$, PPs, and the SFMS., Comment: 26 pages, 13 figures. Accepted for publication on A&A

In the next generation network, the satellite network will play a fundamental role, in overcoming the limitation of the terrestrial network. Nonetheless, the satellite-terrestrial network integration presents a number of problems due to the time-variant topology of the first. One of the most important is the routing process of such networks. Many solutions have been proposed in the literature since the 1990s, and in recent years, the development of modern technologies such as Software Defined Networking (SDN) led to new possible approaches to the routing of satellite network. In this paper, a graph-based, source routing algorithm is presented. The algorithm exploits reliability and flexibility of the SDN architecture and the simplicity of source routing to tackle the dynamic topology of the network, providing rerouting solutions when necessary., Comment: The article must be further refined

We present the first analysis of the Euclid Early Release Observations (ERO) program that targets fields around two lensing clusters, Abell 2390 and Abell 2764. We use VIS and NISP imaging to produce photometric catalogs for a total of $\sim 500\,000$ objects. The imaging data reach a $5\,\sigma$ typical depth in the range 25.1-25.4 AB in the NISP bands, and 27.1-27.3 AB in the VIS band. Using the Lyman-break method in combination with photometric redshifts, we identify $30$ Lyman-break galaxy (LBG) candidates at $z>6$ and 139 extremely red sources (ERSs), most likely at lower redshift. The deeper VIS imaging compared to NISP means we can routinely identify high-redshift Lyman breaks of the order of $3$ magnitudes, which reduces contamination by brown dwarf stars and low-redshift galaxies. Spectroscopic follow-up campaigns of such bright sources will help constrain both the bright end of the ultraviolet galaxy luminosity function and the quasar luminosity function at $z>6$, and constrain the physical nature of these objects. Additionally, we have performed a combined strong lensing and weak lensing analysis of A2390, and demonstrate how Euclid will contribute to better constraining the virial mass of galaxy clusters. From these data, we also identify optical and near-infrared counterparts of known $z>0.6$ clusters, which exhibit strong lensing features, establishing the ability of Euclid to characterize high-redshift clusters. Finally, we provide a glimpse of Euclid's ability to map the intracluster light out to larger radii than current facilities, enabling a better understanding of the cluster assembly history and mapping of the dark matter distribution. This initial dataset illustrates the diverse spectrum of legacy science that will be enabled by the Euclid survey., Comment: Paper submitted as part of the A&A special issue `Euclid on Sky', which contains Euclid key reference papers and first results from the Euclid Early Release Observations. 17 pages, 12 figures

The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015-2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14,000 deg^2 of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance., Comment: Accepted for publication in the A&A special issue`Euclid on Sky'

We present new VLT/MUSE observations of the Hubble Frontier Field (HFF) galaxy cluster MACS J1149.5+2223, lensing the well-known supernova "Refsdal" into multiple images, which enabled the first cosmological applications with a strongly lensed supernova. Thanks to these data, targeting a northern region of the cluster and thus complementing our previous MUSE program on the cluster core, we release a new catalog containing 162 secure spectroscopic redshifts. We confirm 22 cluster members, which were previously only photometrically selected, and detect ten additional ones, resulting in a total of 308 secure members, of which 63% are spectroscopically confirmed. We further identify 17 new spectroscopic multiple images belonging to 6 different background sources. By exploiting MUSE data, in combination with the deep HFF images, we develop an improved total mass model of MACS J1149.5+2223. This model includes 308 total mass components for the member galaxies and requires four additional mass profiles, one of which is associated with a cluster galaxy overdensity identified in the North, representing the DM mass distribution on larger scales. The values of the resulting 34 free parameters are optimized based on the observed positions of 106 multiple images from 34 different families, that cover the redshift range between 1.240 and 5.983. Our final model has a multiple image position rms value of 0.39", which is well in agreement with that of other cluster lens models. With this refined mass model, we pave the way towards even better strong-lensing analyses that will exploit the deep and high resolution observations with HST and JWST on a pixel level in the region of the supernova Refsdal host. This will increase the number of observables by around two orders of magnitudes, thus offering us the opportunity of carrying out more precise and accurate cosmographic measurements., Comment: 14 pages, 7 figures, 4+1 tables, published with A&A

The James Webb Space Telescope (JWST) has discovered a surprising population of bright galaxies in the very early universe (<500 Myrs after the Big Bang) that is hard to explain with conventional galaxy formation models and whose physical properties remain to be fully understood. Insight into their internal physics is best captured through nebular lines but, at these early epochs, the brightest of these spectral features are redshifted into the mid-infrared and remain elusive. Using the JWST Mid-Infrared Instrument, MIRI, here we present the first detection of H{\alpha} and doubly-ionized oxygen ([OIII]5007AA) at z>10. These detections place the bright galaxy GHZ2/GLASS-z12 at z=12.33+/-0.04, making it the most distant astronomical object with direct spectroscopic detection of these lines. These observations provide key insights into the conditions of this primeval, luminous galaxy, which shows hard ionizing conditions rarely seen in the local Universe likely driven by compact and young (~30Myr) burst of star formation. Its oxygen-to-hydrogen abundance is close to a tenth of the solar value, indicating a rapid metal enrichment. This study confirms the unique conditions of this remarkably bright and distant galaxy and the huge potential of mid-IR observations to characterize these objects., Comment: Published in Nature Astronomy on 30 October 2024 (this represents the authors' submitted version)

We spectroscopically confirm the $M_{\rm UV} = -20.5$ mag galaxy GHZ2/GLASS-z12 to be at redshift $z=12.34$. The source was selected via NIRCam photometry in GLASS-JWST ERS data, providing the first evidence of a surprising abundance of bright galaxies at $z \gtrsim 10$. The NIRSpec PRISM spectrum shows detections of N IV, C IV, He II, O III, C III, O II, and Ne III lines, and the first detection at high-redshift of the O III Bowen fluorescence line at 3133 {\AA} rest-frame. The prominent C IV line with rest-frame equivalent width (EW) $\approx 46$ {\AA} puts GHZ2 in the category of extreme C IV emitters. GHZ2 displays UV lines with EWs that are only found in active galactic nuclei (AGNs) or composite objects at low/intermediate redshifts. The UV line-intensity ratios are compatible both with AGNs and star formation in a low-metallicity environment, with the low limit on the [Ne IV]/[N IV] ratio favoring a stellar origin of the ionizing photons. We discuss a possible scenario in which the high ionizing output is due to low metallicity stars forming in a dense environment. We estimate a metallicity $\lesssim 0.1 Z/{\rm Z}_{\odot}$, a high ionization parameter logU $> -2$, a N/O abundance 4--5 times the solar value, and a subsolar C/O ratio similar to the recently discovered class of nitrogen-enhanced objects. Considering its abundance patterns and the high stellar mass density ($10^4$~M$_{\odot}$~pc$^{-2}$), GHZ2 is an ideal formation site for the progenitors of today's globular clusters. The remarkable brightness of GHZ2 makes it a ``Rosetta stone'' for understanding the physics of galaxy formation within just 360 Myr after the Big Bang., Comment: Accepted for publication in The Astrophysical Journal. 20 pages, 7 figures, 2 tables

The exceptional spectra of the most luminous $z>10$ sources observed so far have challenged our understanding of early galaxy evolution, requiring a new observational benchmark for meaningful interpretation. As such, we construct spectroscopic templates representative of high-redshift, star-forming populations, using 482 confirmed sources at $z=5.0-12.9$ with JWST/NIRSpec prism observations, and report on their average properties. We find $z=5-11$ galaxies are dominated by blue UV continuum slopes ($\beta=-2.3$ to $-2.7$) and reduced Balmer indices, characteristic of dust-poor and young systems, with a shift towards bluer slopes and younger ages with redshift. The evolution is mirrored by ubiquitous CIII] detections across all redshifts (rest-frame equivalent widths of $=5-14$ \r{A}), which increase in strength towards early times. Rest-frame optical lines reveal elevated ratios ($O32=7-31$, $R23=5-8$, and $Ne3O2=1-2$) and subsolar metallicities (log O/H$=7.3-7.9$), typical of ionization conditions and metallicities rarely observed in $z\sim0$ populations. Within our sample, we identify 57 Ly$\alpha$ emitters, which we stack and compare to a matched sample of nonemitters. The former are characterized by more extreme ionizing conditions with enhanced CIII], CIV, and HeII+[OIII] line emission, younger stellar populations from Balmer jumps, and a more pristine interstellar medium seen through bluer UV slopes and elevated rest-frame optical line ratios. The novel comparison illustrates important intrinsic differences between the two populations, with implications for Ly$\alpha$ visibility. The spectral templates derived here represent a new observational benchmark with which to interpret high-redshift sources, lifting our constraints on their global properties to unprecedented heights and extending out to the earliest of cosmic times., Comment: Accepted for publication in ApJ (with minor changes). Replaced to match accepted version. All composite spectra available online or upon request

Piezoelectric transducers applied on or integrated in structures, combined with appropriate circuits have been extensively investigated as a smart approach to the mitigation of resonant vibrations with high relative amplitudes. \cmt{A resonant shunt circuit consisting of the capacitive piezoelectric transducer and an inductance can be configured to target specific eigenmodes of a structure, if appropriately placed and tuned. Their effect is expressed in terms of mechanical impedance of the host structure, allowing for the exchange of energy between the mechanical and electrical domain, to dramatically affect the dynamic response of the structure. By re-framing the function of resonant shunted piezoelectric transducers as frequency dependent variable stiffness elements, this paper investigates their capability to realize a frequency dependent structural mechanical connectivity, where the load path within a lattice structure can be interrupted at will for specific frequencies by tunable null-stiffness components. Here, we offer the numerical and experimental verification of this idea, by demonstrating the ability to significantly affect the dynamic response of a unit cell of an adaptive lattice metamaterial, even away from a structural resonance. In the latter case, the null-stiffness shunt leads to an additional resonance peak in the truss' dynamic response.} Its realization as additively manufactured component points to the feasibility of such structures in real life.

We present deep JWST NIRSpec observations in the sightline of MACS J1149.5+2223, a massive cluster of galaxies at $z=0.54$. We report the spectroscopic redshift of 28 sources at $37$, i.e. comparable to the most metal poor galaxies in the local Universe. The search of primordial galaxies may be accomplished by extending toward a lower mass and/or by investigating inhomogeneities at smaller spatial scales. Lastly, we investigate potential systematics caused by the limitation of JWST's MSA observations. Caution is warranted when the target exceeds the slit size, as this situation could allow an overestimation of "global" metallicity, especially under the presence of strong negative metallicity gradient., Comment: Accepted for publication on May 29, 2024 to ApJ

We present a new weak lensing analysis of the Hubble Frontier Fields galaxy cluster Abell 2744 ($z$ = 0.308) using new Magellan/MegaCam multi-band $gri$ imaging data. We carry out our study by applying brand-new PSF and shape measurement softwares that allow for the use of multi-band data simultaneously, which we first test on Subaru/Suprime-Cam $BR_cz'$ imaging data of the same cluster. The projected total mass of this system within $2.35 \, \mathrm{Mpc}$ from the south-west BCG is $(2.56 \pm 0.26) \times 10^{15} \, \mathrm{M}_\odot$, which makes Abell 2744 one of the most massive clusters known. This value is consistent, within the errors, with previous weak lensing and dynamical studies. Our analysis reveals the presence of three high-density substructures, thus supporting the picture of a complex merging scenario. This result is also confirmed by a comparison with a recent strong lensing study based on high-resolution JWST imaging. Moreover, our reconstructed total mass profile nicely agrees with an extrapolation of the strong lensing best-fit model up to several Mpc from the BCG centre.

We present a new high-precision strong lensing model of PLCK G287.0$+$32.9, a massive lens galaxy cluster at $z=0.383$, with the aim to get an accurate estimation of its effective Einstein radius and total mass distribution. We also present a spectroscopic catalog containing accurate redshift measurements for 490 objects, including multiply-lensed sources and cluster member galaxies. We exploit high-quality spectroscopic data from three pointings of the VLT Multi Unit Spectroscopic Explorer, covering a central $3~\rm{arcmin}^2$ region of the cluster. We complete the spectroscopic catalog by including redshift measurements from VLT-VIMOS and KECK-DEIMOS. We identify 129 spectroscopic cluster member galaxies, with redshift values $0.360 \leq z \leq 0.405$ and $m_{\rm{F160W}} \leq 21$, and 24 photometric ones identified with a Convolutional Neural Network from ancillary HST imaging. We also identify 114 multiple images from 28 background sources, of which 84 images from 16 sources are new and the remaining ones were identified in previous work. The best-fitting lens model shows a root mean square separation value between the predicted and observed positions of the multiple images of $0.75''$, corresponding to an improvement in reconstructing the observed positions of the multiple images of a factor of $2.5$ with respect to previous models. Using the predictive power of our new lens model we find 3 new multiple images and we confirm the configuration of three systems of multiple images that were not used for the optimization of the model. The derived total mass distribution confirms this cluster to be a very prominent gravitational lens with an effective Einstein $\theta_{E} = 43.4'' \pm 0.1''$, that is in agreement with previous estimates and corresponds to a total mass enclosed in the critical curve of $M_E = {3.33}_{-0.07}^{+0.02} \times{ 10^{14} M_\odot}$., Comment: submitted to "Astronomy & Astrophysics" and accepted the on January 29th 2024

We present a novel approach to measuring the expansion rate and the geometry of the Universe, which combine time-delay cosmography in lens galaxy clusters with pure samples of 'cosmic chronometers' (CCs) by probing the member galaxies. The former makes use of the measured time delays between the multiple images of time-varying sources strongly lensed by galaxy clusters, while the latter exploits the most massive and passive cluster member galaxies to measure the differential time evolution of the Universe. We applied two different statistical techniques, adopting realistic errors on the measured quantities, to assess the accuracy and the gain in precision on the values of the cosmological parameters. We demonstrate that the proposed combined method allows for a robust and accurate measurement of the value of the Hubble constant. In addition, this provides valuable information on the other cosmological parameters thanks to the complementarity between the two different probes in breaking parameter degeneracies. Finally, we showcase the immediate observational feasibility of the proposed joint method by taking advantage of the existing high-quality spectro-photometric data for several lens galaxy clusters., Comment: 6 pages, 2 figures. Accepted for publication in A&A Letters

We present a simple and promising new method to measure the expansion rate and the geometry of the universe that combines observations related to the time delays between the multiple images of time-varying sources, strongly lensed by galaxy clusters, and Type Ia supernovae, exploding in galaxies belonging to the same lens clusters. By means of two different statistical techniques that adopt realistic errors on the relevant quantities, we quantify the accuracy of the inferred cosmological parameter values. We show that the estimate of the Hubble constant is robust and competitive, and depends only mildly on the chosen cosmological model. Remarkably, the two probes separately produce confidence regions on the cosmological parameter planes that are oriented in complementary ways, thus providing in combination valuable information on the values of the other cosmological parameters. We conclude by illustrating the immediate observational feasibility of the proposed joint method in a well-studied lens galaxy cluster, with a relatively small investment of telescope time for monitoring from a 2 to 3m class ground-based telescope., Comment: 6 pages, 2 figures, 1 table. Published in A&A Letters

We study the ultraviolet (UV) continuum $\beta$ slope of a sample of 166 clumps, individual star-forming regions observed in high redshift galaxies. They are hosted by 67 galaxies with redshift between 2 and 6.2, strongly lensed by the Hubble Frontier Fields cluster of galaxies MACS J0416.1-2403. The $\beta$ slope is sensitive to a variety of physical properties, such as the metallicity, the age of the stellar population, the dust attenuation throughout the galaxy, the stellar initial mass function (IMF), and the star-formation history (SFH). The aim of this study is to compare the $\beta$ values of individual clumps with those measured on the entire galaxy, to investigate possible physical differences between these regions and their hosts. We found a median value of $\beta \sim -2.4$, lower than that of integrated galaxies. This result confirms that clumps are sites of intense star formation, populated by young, massive stars, whose spectrum strongly emits in the UV. This is also consistent with the assumption that the dust extinction at the location of the clumps is lower than the average extinction of the galaxy, or that clumps have a different IMF or SFH. We made use of the correlations, discovered for high-redshift galaxies, of the $\beta$ value with those of redshift and UV magnitude, $M_{UV}$, finding that clumps follow the same relations, extended to much fainter magnitudes ($M_{UV}<-13$). We also find evidence of eight clumps with extremely blue ($\beta \lesssim -2.7$) slopes, which could be the signpost of low-metallicity stars and constrain the emissivity of ionizing photons at high redshift., Comment: 16 pages, 9 figures. Accepted for publication in MNRAS

We aim at a direct measurement of the compactness of three galaxy-scale lenses in massive clusters, testing the accuracy of the scaling laws that describe the members in strong lensing (SL) models of galaxy clusters. We selected the multiply imaged sources MACS J0416.1$-$2403 ID14 ($z=3.221$), MACS J0416.1$-$2403 ID16 ($z=2.095$), and MACS J1206.2$-$0847 ID14 ($z=3.753$). Eight images were observed for the first SL system, and six for the latter two. We focused on the main deflector of each galaxy-scale SL system (identified as members 8971, 8785, and 3910, respectively), and modelled its total mass distribution with a truncated isothermal sphere. We accounted for the lensing effects of the remaining cluster components, and included the uncertainty on the cluster-scale mass distribution through a bootstrapping procedure. We measured a truncation radius value of $6.1^{+2.3}_{-1.1} \, \mathrm{kpc}$, $4.0^{+0.6}_{-0.4} \, \mathrm{kpc}$, and $5.2^{+1.3}_{-1.1} \, \mathrm{kpc}$ for members 8971, 8785, and 3910, respectively. Alternative non-truncated models with a higher number of free parameters do not lead to an improved description of the SL system. We measured the stellar-to-total mass fraction within the effective radius $R_e$ for the three members, finding $0.51\pm0.21$, $1.0\pm0.4$, and $0.39\pm0.16$, respectively. We find that a parameterisation of the properties of cluster galaxies in SL models based on power-law scaling relations with respect to the total luminosity cannot accurately describe their compactness over their full total mass range. Our results agree with modelling of the cluster members based on the Fundamental Plane relation. Finally, we report good agreement between our values of the stellar-to-total mass fraction within $R_e$ and those of early-type galaxies from the SLACS Survey. Our work significantly extends the regime of the current samples of lens galaxies., Comment: Accepted for publication in Astronomy and Astrophysics, 15 pages, 12 figures, 8 tables

Previous studies have revealed that the estimated probability of galaxy-galaxy strong lensing in observed galaxy clusters exceeds the expectations from the $\Lambda$ Cold Dark Matter cosmological model by one order of magnitude. We aim to understand the origin of this excess by analyzing a larger set of simulated galaxy clusters and investigating how the theoretical expectations vary under different adopted prescriptions and numerical implementations of star formation and feedback in simulations. We perform a ray-tracing analysis of 324 galaxy clusters from the Three Hundred project, comparing the Gadget-X and Gizmo-Simba runs. These simulations, which start from the same initial conditions, are performed with different implementations of hydrodynamics and galaxy formation models tailored to match different observational properties of the Intra-Cluster-Medium and cluster galaxies. We find that galaxies in the Gizmo-Simba simulations develop denser stellar cores than their Gadget-X counterparts. Consequently, their probability for galaxy-galaxy strong lensing is higher by a factor of $\sim 3$. This increment is still insufficient to fill the gap with observations, as a discrepancy by a factor $\sim 4$ still persists. In addition, we find that several simulated galaxies have Einstein radii that are too large compared to observations. We conclude that a persistent excess of galaxy-galaxy strong lensing exists in observed galaxy clusters. The origin of this discrepancy with theoretical predictions is still unexplained in the framework of the cosmological hydrodynamical simulations. This might signal a hitherto unknown issue with either the simulation methods or our assumptions regarding the standard cosmological model., Comment: 6 pages, 2 figures, accepted for publication on A&A Letters. See companion paper Srivastava et al. (2023)

We present a comprehensive search and analysis of high-redshift galaxies in a suite of nine public JWST extragalactic fields taken in Cycle 1, covering a total effective search area of $\sim358{\rm arcmin^2}$. Through conservative ($8\sigma$) photometric selection, we identify 341 galaxies at $51.5\,\sigma$ below the derived size-mass slope. These compact sources exhibit a high star formation surface density $\Sigma_{\rm SFR}>10\,M_\odot\,{\rm yr^{-1}\,kpc^{-2}}$, a range in which only $<0.01\,\%$ of the local star-forming galaxy sample is found. For those with available NIRSpec data, no evidence of ongoing supermassive black hole accretion is observed. A potential explanation for the observed high [OIII]-to-Hbeta ratios could be high shock velocities, likely originating within intense star-forming regions characterized by high $\Sigma_{\rm SFR}$. Lastly, we find that the rest-frame UV and optical sizes of our sample are comparable. Our results are consistent with these early galaxies building up their structures inside-out and yet to exhibit the strong color gradient seen at lower redshift., Comment: Accepted for publication in ApJ

In this paper, we incorporate the effect of nonlinear damping with the concept of locally resonant metamaterials to enable vibration attenuation beyond the conventional bandgap range. The proposed design combines a linear host cantilever beam and periodically distributed inertia amplifiers as nonlinear local resonators. The geometric nonlinearity induced by the inertia amplifiers causes an amplitude-dependent nonlinear damping effect. Through the implementation of both modal superposition and numerical harmonic methods the finite nonlinear metamaterial is accurately modelled. The resulting nonlinear frequency response reveals the bandgap is both amplitude-dependent and broadened. Furthermore, the modal frequencies are also attenuated due to the nonlinear damping effect. The theoretical results are validated experimentally. By embedding the nonlinear damping effect into locally resonant metamaterials, wideband attenuation of the proposed metamaterial is achieved, which opens new possibilities for versatile metamaterials beyond the limit of their linear counterparts.

Forthcoming imaging surveys will potentially increase the number of known galaxy-scale strong lenses by several orders of magnitude. For this to happen, images of tens of millions of galaxies will have to be inspected to identify potential candidates. In this context, deep learning techniques are particularly suitable for the finding patterns in large data sets, and convolutional neural networks (CNNs) in particular can efficiently process large volumes of images. We assess and compare the performance of three network architectures in the classification of strong lensing systems on the basis of their morphological characteristics. We train and test our models on different subsamples of a data set of forty thousand mock images, having characteristics similar to those expected in the wide survey planned with the ESA mission \Euclid, gradually including larger fractions of faint lenses. We also evaluate the importance of adding information about the colour difference between the lens and source galaxies by repeating the same training on single-band and multi-band images. Our models find samples of clear lenses with $\gtrsim 90\%$ precision and completeness, without significant differences in the performance of the three architectures. Nevertheless, when including lenses with fainter arcs in the training set, the three models' performance deteriorates with accuracy values of $\sim 0.87$ to $\sim 0.75$ depending on the model. Our analysis confirms the potential of the application of CNNs to the identification of galaxy-scale strong lenses. We suggest that specific training with separate classes of lenses might be needed for detecting the faint lenses since the addition of the colour information does not yield a significant improvement in the current analysis, with the accuracy ranging from $\sim 0.89$ to $\sim 0.78$ for the different models., Comment: 23 pages,12 figures

We present JWST/NIRSpec integral field spectroscopy (IFS) of a lensed Population III candidate stellar complex (dubbed Lensed And Pristine 1, LAP1), with a lensing-corrected stellar mass ~<10^4 Msun, absolute luminosity M_UV > -11.2 (m_UV > 35.6), confirmed at redshift 6.639 +/- 0.004. The system is strongly amplified (\mu >~ 100) by straddling a critical line of the Hubble Frontier Field galaxy cluster MACS J0416. Despite the stellar continuum is currently not detected in the Hubble and JWST/NIRCam and NIRISS imaging, arclet-like shapes of Lyman and Balmer lines, Lya, Hg, Hb and Ha are detected with NIRSpec IFS with signal-to-noise ratios SNR=5-13 and large equivalent widths (>300-2000A), along with a remarkably weak [OIII]4959-5007 at SNR ~ 4. LAP1 shows a large ionizing photon production efficiency, log(\xi_{ion}[erg~Hz^{-1}])>26. From the metallicity indexes R23 = ([OIII]4959-5007 + [OII]3727) / Hb ~< 0.74 and R3 = ([OIII]5007 / Hb) = 0.55 +/- 0.14, we derive an oxygen abundance 12+log(O/H) ~< 6.3. Intriguingly, the Ha emission is also measured in mirrored sub-components where no [OIII] is detected, providing even more stringent upper limits on the metallicity if in-situ star formation is ongoing in this region (12+log(O/H) < 6, or Z < 0.002 Zsun). The formal stellar mass limit of the sub-components would correspond to ~10^{3} Msun or M_UV fainter than -10. Alternatively, such a metal-free pure line emitting region could be the first case of a fluorescing HI gas region, induced by transverse escaping ionizing radiation from a nearby star-complex. The presence of large equivalent-width hydrogen lines and the deficiency of metal lines in such a small region, make LAP1 the most metal poor star-forming region currently known in the reionization era and a promising site that may host isolated, pristine stars., Comment: 15 pages, 10 figures, 1 table. Submitted to A&A. Comments welcome