arXiv subjects

E. Portaluri

Publications and source records attributed to E. Portaluri.

17 recordsLinked to original sources

arXiv2026

Structural, thermal and optical tolerance analysis of SHARP, a near infrared spectrograph for next generation telescope

The design and verification of cryogenic near-infrared spectrographs require rigorous multidisciplinary analyses to ensure optical performance under realistic operational conditions. In this work, we present a structural-thermal-optical performance (STOP) analysis of the SHARP instrument, a multi-mode spectrograph designed for use with upcoming multi-conjugate adaptive optics (MCAO) systems on Extremely Large Telescopes (ELTs). Transient and steady-state thermal simulations were performed using Ansys to model the cooldown process and temperature distribution within the opto-mechanical structure. The resulting temperature fields were mapped to structural models through linear interpolation, enabling the evaluation of thermal stresses and deformations of optical elements. Optical sensitivity and tolerance analyses were carried out using Ansys Zemax OpticStudio, with Monte Carlo simulations applied to assess robustness against decenter, tilt, and despace errors. Results indicate that SHARP maintains RMS spot radius values within acceptance threshold, and that the inclusion of compensators significantly enhances compliance with the Ensquared Energy (EE) requirement across all channels. The analysis confirms that SHARP can achieves its optical performance goals while remaining within mechanical and thermal constraints, providing a validated framework for the development of next-generation cryogenic astronomical instrumentation.

astro-ph.IM↗

arXiv2026

Unveiling the properties of galaxy cores excavated by supermassive black hole binaries with SHARP

Massive black hole (MBH) binaries form as a result of galaxy mergers and can coalesce into a single MBH by emitting gravitational waves detectable by LISA and pulsar timing array campaigns. Although electromagnetic observations of bound MBH binaries are extremely challenging, an indirect signature of their passage is the core scouring: a bound binary shrinks by ejecting nearby stars, creating a flat stellar density core of the size of the binary influence radius. Through this mechanism, stars on radial orbits are preferentially ejected, resulting in a central tangential anisotropy in the velocity field of stars that can be identified via IFU observations. At present, the sample of galaxies with such properties is limited by instrument resolution to the closest giant ellipticals within the nearest ~100 Mpc. The SHARP-VESPER IFU and MICADO+MORFEO instruments can work in concert to detect both these features: their unprecedented spatial resolution can allow us to detect central scourings with sizes above ~500 pc in principle up to reionization; smaller cores of ~150 pc can be detected up to z~0.14, encompassing a volume that is more than 40 times the one available at present. In addition, they can enable the search for these features in smaller galaxies, enhancing by a factor 30 the volume over which we can search for pc-size cores around 1-10 million solar mass MBHs. The fraction of scoured galaxies, combined with their kinematic and morphological properties, carry information on the amount of merging binaries, their masses and typical environment, thus knowing this will be fundamental to complement the forthcoming gravitational wave data.

astro-ph.GA↗

arXiv2026

SHARP -- A spectrograph proposal to fully exploit ELT capabilities and look beyond JWST

The Extremely Large Telescopes (ELTs), with their large apertures and cutting-edge Multi-Conjugate Adaptive Optics (MCAO) systems, promise to deliver data that is both sharper and deeper than even the James Webb Space Telescope (JWST) across large fields. SHARP is a concept study for a near-IR (0.95-2.45 $\mu$m) spectrograph specifically designed to fully exploit the collecting area and angular resolution capabilities of the upcoming ESO's ELT. The instrument concept is driven by the goal of tackling the most important questions in astrophysics and cosmology, from exploring primordial galaxies to studying the formation of young stellar object and planetary systems in the nearby dust-enshrouded regions, bridging the gap between the local and the distant Universe. This requires versatility to accommodate diverse observational needs. SHARP is composed of two main units: NEXUS, a Multi-Object Spectrograph (MOS) optimized for detecting the faintest sources, and VESPER, a multi-object Integral Field Unit (multi-IFU) designed for brighter ones. This article provides an overview of the scientific design drivers, the solutions developed to meet them, and the resulting optical design that achieves the required performance.

astro-ph.IM↗

arXiv2026

A new era for Dual AGN science with SHARP

The search for and the characterization of ultra-compact dual active galactic nuclei (AGN) are among the hottest topics of current extragalactic astrophysics. These systems involve two accreting massive black holes (MBHs) embedded within the same host galaxy, with relative projected separations from a few hundred pc down to a few pc. They are central to understanding hierarchical galaxy formation, black hole growth and demographics, and accretion-feedback coupling in the most extreme interaction phases. Even more compellingly, such tight pairs are the most direct precursors of gravitationally bound binary MBHs (sub-pc scale separation), which are among the loudest emitters of gravitational waves (GWs) in the low-frequency ranges. SHARP will deliver the first statistical census and physical characterization of ultra-compact dual AGN up to cosmic distances, finally bridging the observational gap between kpc-scale pairs and sub-pc GW-emitting binaries, and enabling a breakthrough understanding of MBH growth, feedback and co-evolution across cosmic time.

astro-ph.GA↗

arXiv2026

Advancing the detection of low surface brightness galaxies. I. ATTILA: multi-tAsking deTecTIon tool for Lsb gAlaxies

Context. Ultra-diffuse galaxies (UDGs) lie at the extreme end of the size-luminosity distribution of low surface-brightness (LSB) galaxies. Their detection and characterization require deep imaging and reliable source detection techniques that can handle low signal-to-noise ratios and severe source blending. Aims. We aim at improving the detection and characterization of the LSB galaxies and UDG candidates in different environments. To this end, we have developed a new automated detection Python-based tool, named ATTILA. Methods. We use deep g- and r-band imaging from the VST Early-type GAlaxy Survey (VEGAS), covering the central region of Hydra I and three new additional fields. Sources are identified combining tiling processing, source detection, and iterative deblending. The structural parameters are derived through surface brightness profile analysis and S\'ersic modelling. Cluster membership is determined using the early-type galaxies colour-magnitude relation. Results. We identify 24 new UDGs, doubling the known population in the Hydra-I cluster to 48, consistent with expectations from halo mass scaling relations, and 92 additional LSB galaxies. In real data, ATTILA recovers more than 80% of previously known LSB galaxies and significantly improves the automated detection rate relative to standard methods. Conclusions. By improving the recovery of faint and diffuse sources while mitigating blending and contamination effects, ATTILA enables a more complete census of the LSB galaxy population, including UDGs.

astro-ph.GA↗

arXiv2026

Fast, dust-poor outflows in the local candidate dual AGN MCG-03-34-64 observed with VLT/ERIS

We present VLT/ERIS IFU J-band observations of MCG-03-34-64, a nearby (z = 0.0167) Seyfert galaxy hosting a candidate dual AGN system with a separation of ~100 pc between the nuclei. The observations cover, among others, the HeI1.083um, [FeII]1.257um and Pa$\beta$ emission lines, over a FoV of 3"x3"(~1x1 kpc$^2$). We analyse the ionised gas kinematics and identify two regions with enhanced velocity dispersion (W80~1500 km/s), suggestive of fast outflowing gas, spatially coincident with the position of the two candidate active nuclei. The spectra of the two outflows show a prominent blueshifted wing with velocities vmax ~ -1700 km/s corresponding to the highest 2-5 percentiles of samples of local AGN with similar bolometric luminosities. For the ionised phase of the two outflows, we derive comparable masses of $(4\pm1)\times 10^5$ $M_{\odot}$ and mass outflow rates of $20\pm5$ $M_{\odot}$/yr. The two distinct outflows could be associated with the two nuclei, or be generated by the interaction of the radio jet with the ISM. We also analyse the peculiar profile of the [Fe VII]6087A optical coronal line from an archival VLT/X-shooter spectrum. The comparison with the [NeV]3425A and [FeII]1.257um profiles indicates that [Fe VII] emission likely arises only from the outflow. The absence of the systemic component in [Fe VII] - unlike in [NeV], which has similar ionisation potential and critical density - suggests suppression of [Fe VII] due to iron depletion onto dust grains, while its detection in the outflow implies a lower dust content than in the host ISM. The additional information gained from the ERIS data are consistent with the scenario of a dual AGN, however further observations are required to confirm its nature.

astro-ph.GA↗

arXiv2025

SHARP: Beyond JWST -- Revealing the galaxy birth and growth with the resolution of the ELT

A deep understanding of the life-cycle of galaxies, particularly those of high mass, requires clarifying the mechanisms that regulate star formation (SF) and its abrupt shutdown (quenching), often capable of stopping SF rates of hundreds of solar masses per year. What initially triggers quenching, and what sustains the quiescent state thereafter, especially given the frequent presence of large gas reservoirs or even massive gas inflows, are unsolved key issues. Ultimately, the crucial connection between the galaxy life-cycle and the surrounding Intergalactic (IGM) and Circumgalactic (CGM) Medium remains largely unclear. Addressing these issues requires studying star formation, chemical enrichment, and quenching homogeneously up to high redshift. The upcoming AO-assisted Extremely Large Telescope (ELT), will deliver sharper and deeper data than the JWST. SHARP is a concept study for a near-IR (0.95-2.45 mu) spectrograph designed to fully exploit the capabilities of ELT. Designed for multi-object slit spectroscopy and multi-Integral Field spectroscopy, SHARP points to achieve angular resolutions (~30 mas) far superior to NIRSpec at JWST(100 mas) to decipher and reconstruct the life-cycle oa galaxies.

astro-ph.IM↗

arXiv2025

Conceptual Opto-Mechanical design of SHARP: a near-infrared multi-mode spectrograph conceived for the next-generation telescopes

The next generation of Extremely Large Telescopes (ELTs), with their wide apertures and advanced Multi-Conjugate Adaptive Optics (MCAO) systems, will provide unprecedented sharp and deep observations, even surpassing the capabilities of James Webb Space Telescope (JWST). SHARP, a near-infrared (0.95-2.45 {\mu}m) spectrograph, is designed to optimally exploit the collecting area and angular resolution of these forthcoming ELTs, and specifically optimized for the MCAO unit MORFEO at the ELT. SHARP includes two main units: NEXUS, a Multi-Object Spectrograph (MOS), and VESPER, a multi-Integral Field Unit. This paper outlines the opto-mechanical design of SHARP based on the scientific requirements of the project. The optical design is engineered to meet project specifications, featuring a compact mechanical structure that minimizes the required cryogenic power while ensuring ease of access for maintenance and straightforward assembly procedures.

astro-ph.IM↗

arXiv2024

Estimating Masses of Supermassive Black Holes in Active Galactic Nuclei from the Halpha Emission Line

The goal of this project is to construct an estimator for the masses of supermassive black holes in active galactic nuclei (AGNs) based on the broad Halpha emission line. We make use of published reverberation mapping data. We remeasure all Halpha time lags from the original data as we find that often the reverberation measurements are improved by detrending the light curves. We produce mass estimators that require only the Halpha luminosity and the width of the Halpha emission line as characterized by either the FWHM or the line dispersion. It is possible, on the basis of a single spectrum covering the Halpha emission line, to estimate the mass of the central supermassive black hole in AGNs, taking into account all three parameters believed to affect mass measurement: luminosity, line width, and Eddington ratio. The typical formal accuracy in such estimates is of order 0.2-0.3 dex.

astro-ph.GA↗

arXiv2024

SHARP -- A near-IR multi-mode spectrograph conceived for MORFEO@ELT

The Extremely Large Telescopes (ELTs), thanks to their large apertures and cutting-edge Multi-Conjugate Adaptive Optics (MCAO) systems, promise to deliver sharper and deeper data even than the JWST. SHARP is a concept study for a near-IR (0.95-2.45 $μ$m) spectrograph conceived to fully exploit the collecting area and the angular resolution of the upcoming generation of ELTs. In particular, SHARP is designed for the 2nd port of MORFEO@ELT. Composed of a Multi-Object Spectrograph, NEXUS, and a multi-Integral Field Unit, VESPER, MORFEO-SHARP will deliver high angular ($\sim$30 mas) and spectral (R$\simeq$300, 2000, 6000, 17000) resolution, outperforming NIRSpec@JWST (100 mas). SHARP will enable studies of the nearby Universe and the early Universe in unprecedented detail. NEXUS is fed by a configurable slit system deploying up to 30 slits with $\sim$2.4 arcsec length and adjustable width, over a field of about 1.2"$\times$1.2" (35 mas/pix). Each slit is fed by an inversion prism able to rotate by an arbitrary angle the field that can be seen by the slit. VESPER is composed of 12 probes of 1.7"$\times$1.5" each (spaxel 31 mas) probing a field 24"$\times$70". SHARP is conceived to exploit the ELTs apertures reaching the faintest flux and the sharpest angular resolution by joining the sensitivity of NEXUS and the high spatial sampling of VESPER to MORFEO capabilities. This article provides an overview of the scientific design drivers, their solutions, and the resulting optical design of the instrument achieving the required optical performance.

astro-ph.IM↗

arXiv2021

Detectability of large-scale counter-rotating stellar disks in galaxies with integral-field spectroscopy

In recent years integral-field spectroscopic surveys have revealed that the presence of kinematically decoupled stellar components is not a rare phenomenon in nearby galaxies. However, complete statistics are still lacking because they depend on the detection limit of these objects. We investigate the kinematic signatures of two large-scale counter-rotating stellar disks in mock integral-field spectroscopic data to address their detection limits as a function of the galaxy properties and instrumental setup. We built a set of mock data of two large-scale counter-rotating stellar disks as if they were observed with the Multi-Unit Spectroscopic Explorer (MUSE). We accounted for different photometric, kinematic, and stellar population properties of the two counter-rotating components as a function of galaxy inclination. We extracted the stellar kinematics in the wavelength region of the calcium triplet absorption lines by adopting a Gauss-Hermite (GH) parameterization of the line-of-sight velocity distribution (LOSVD). We confirm that the strongest signature of the presence of two counter-rotating stellar disks is the symmetric double peak in the velocity dispersion map, already known as the $2σ$ feature. The size, shape, and slope of the 2$σ$ peak strongly depend on the velocity separation and relative light contribution of the two counter-rotating stellar disks. When the $2σ$ peak is difficult to detect due to the low signal-to-noise ratio of the data, the large-scale structure in the $h_3$ map can be used as a diagnostic for strong and weak counter-rotation. The counter-rotating kinematic signatures become fainter at lower viewing angles as an effect of the smaller projected velocity separation between the two counter-rotating components. We confirm that the observed frequency of $2σ$ galaxies represents only a lower limit of the stellar counter-rotation phenomenon.

astro-ph.GA↗

arXiv2018

Data processing on simulated data for SHARK-NIR

A robust post processing technique is mandatory to analyse the coronagraphic high contrast imaging data. Angular Differential Imaging (ADI) and Principal Component Analysis (PCA) are the most used approaches to suppress the quasi-static structure in the Point Spread Function (PSF) in order to revealing planets at different separations from the host star. The focus of this work is to apply these two data reduction techniques to obtain the best limit detection for each coronagraphic setting that has been simulated for the SHARK-NIR, a coronagraphic camera that will be implemented at the Large Binocular Telescope (LBT). We investigated different seeing conditions ($0.4"-1"$) for stellar magnitude ranging from R=6 to R=14, with particular care in finding the best compromise between quasi-static speckle subtraction and planet detection.

astro-ph.EP↗

arXiv2018

Velocity-resolved reverberation mapping of five bright Seyfert 1 galaxies

We present the first results from a reverberation-mapping campaign undertaken during the first half of 2012, with additional data on one AGN (NGC 3227) from a 2014 campaign. Our main goals are (1) to determine the black hole masses from continuum-Hbeta reverberation signatures, and (2) to look for velocity-dependent time delays that might be indicators of the gross kinematics of the broad-line region. We successfully measure Hbeta time delays and black hole masses for five AGNs, four of which have previous reverberation mass measurements. The values measured here are in agreement with earlier estimates, though there is some intrinsic scatter beyond the formal measurement errors. We observe velocity dependent Hbeta lags in each case, and find that the patterns have changed in the intervening five years for three AGNs that were also observed in 2007.

astro-ph.GA↗

arXiv2018

A virtual coronagraphic test bench for SHARK-NIR, the second-generation high contrast imager for the Large Binocular Telescope

In this article, we present a simulator conceived for the conceptual study of an AO-fed high-contrast coronagraphic imager. The simulator implements physical optics: a complex disturbance (the electric field) is Fresnel-propagated through any user-defined optical train, in an end-to-end fashion. The effect of atmospheric residual aberrations and their evolution with time can be reproduced by introducing in input a temporal sequence of phase screens: synthetic images are then generated by co-adding instantaneous PSFs. This allows studying with high accuracy the impact of AO correction on image quality for different integration times and observing conditions. In addition, by conveniently detailing the optical model, the user can easily implement any coronagraphic set-up and introduce optical aberrations at any position. Furthermore, generating multiple images can allow exploring detection limits after a differential post-processing algorithm is applied (e.g. Angular Differential Imaging). The simulator has been developed in the framework of the design of SHARK-NIR, the second-generation high contrast imager selected for the Large Binocular Telescope.

astro-ph.IM↗

arXiv2018

A testing facility for AO on-sky demonstrations at the Copernico's Telescope within the ADONI framework

In the context of ADONI - the ADaptive Optics National laboratory of INAF - we are arranging for a facility, accessible to the AO community, in which visiting multi-purpose instrumentation, e.g. systems and prototypes of innovative AO concepts, may be directly tested on sky. The facility is located at the 182cm Copernico telescope in Asiago, the largest telescope in Italy, at its Coude focus, for which refurbishment activities are carried out, given that this focus was initially foreseen in the design, but never implemented and used till today. The facility hosts a laboratory where specialized visiting AO instrumentation may be properly accommodated on an optical bench for on-sky demonstrations. We present the current status of the facility, describing the opto-mechanical design implemented at the telescope that allows to redirect the light toward the Coude focus, the tests on the opto-mechanics carried on for stability verification, the integration of the optical and mechanical components within the preexisting structure.

astro-ph.IM↗

arXiv2016

The young nuclear stellar disc in the SB0 galaxy NGC 1023

Small kinematically-decoupled stellar discs with scalelengths of a few tens of parsec are known to reside in the centre of galaxies. Different mechanisms have been proposed to explain how they form, including gas dissipation and merging of globular clusters. Using archival Hubble Space Telescope imaging and ground-based integral-field spectroscopy, we investigated the structure and stellar populations of the nuclear stellar disc hosted in the interacting SB0 galaxy NGC 1023. The stars of the nuclear disc are remarkably younger and more metal rich with respect to the host bulge. These findings support a scenario in which the nuclear disc is the end result of star formation in metal enriched gas piled up in the galaxy centre. The gas can be of either internal or external origin, i.e. from either the main disc of NGC 1023 or the nearby satellite galaxy NGC 1023A. The dissipationless formation of the nuclear disc from already formed stars, through the migration and accretion of star clusters into the galactic centre is rejected.

astro-ph.GA↗

arXiv2013

Searching for nuclear stellar discs in simulations of star cluster mergers

The nuclei of galaxies often host small stellar discs with scale-lengths of a few tens of parsecs and luminosities up to 10^7 Lsun. To investigate the formation and properties of nuclear stellar discs (NSDs), we look for their presence in a set of N-body simulations studying the dissipationless merging of multiple star clusters in galactic nuclei. A few tens of star clusters with sizes and masses comparable to those of globular clusters observed in the Milky Way are accreted onto a pre-existing nuclear stellar component: either a massive super star cluster or a rapidly rotating, compact disc with a scale-length of a few parsecs, mimicing the variety of observed nuclear structures. Images and kinematic maps of the simulation time-steps are then built and analysed as if they were real and at the distance of the Virgo cluster. We use the Scorza-Bender method to search for the presence of disc structures via photometric decomposition. In one case the merger remnant has all the observed photometric and kinematic properties of NSDs observed in real galaxies. This shows that current observations are consistent with most of the NSD mass being assembled from the migration and accretion of star clusters into the galactic centre. In the other simulation instead, we detect an elongated structure from the unsharp masked image, that does not develop the photometric or kinematic signature of a NSD. Thus, in the context of searches for a disc structure, the Scorza-Bender method is a robust and necessary tool.

astro-ph.CO↗