arXiv subjects

Enrica Iodice

Publications and source records attributed to Enrica Iodice.

15 recordsLinked to original sources

arXiv2026

Stellar halos of bright central galaxies II: Scaling relations, colors and metallicity evolution with redshift

We study the formation and evolution of stellar halos (SHs) around bright central galaxies (BCGs), focusing on their scaling relations, colors, and metallicities across cosmic time, and compare model predictions with ultra--deep imaging data. We use the semianalytic model \textsc{FEGA25}, applied to merger trees from high--resolution dark matter simulations, including an updated treatment of intracluster light (ICL) formation. SHs are defined as the stellar component within the transition radius, linked to halo concentration. Predictions are compared with observations from the VST Early-type GAlaxy Survey (VEGAS) and Fornax Deep Survey (FDS). The SH mass correlates strongly with both BCG and ICL masses, with tighter scatter in the SH--ICL relation. The transition radius peaks at 30--40 kpc nearly independent of redshift, but can reach $\sim400$ kpc in the most massive halos, after z=0.5. SHs and ICL show nearly identical color distributions at all epochs, both reddening toward $z=0$. At $z=2$, SHs and the ICL are $\sim0.4$ dex more metal--poor than BCGs, but the gap shrinks to $\sim0.1$ dex by the present time. Observed colors are consistent with model predictions, while observed metallicities are lower, suggesting a larger contribution from disrupted dwarfs. SHs emerge as transition regions between BCGs and the ICL, dynamically and chemically coupled to both. Their properties depend on halo concentration, ICL formation efficiency, and the progenitor mass spectrum. Upcoming wide--field photometric and spectroscopic surveys (e.g. LSST, WEAVE, 4MOST) will provide crucial tests by mapping structure, metallicity, and kinematics in large galaxy samples.

astro-ph.GA↗

arXiv2025

Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: A Low Surface Brightness Science Case

The Extragalactic Low Surface Brightness (LSB, $μ_V\gtrsim 27$ mag/arcsec$^2$) Universe represents a crucial, yet largely unseen, frontier in modern astrophysics. This faint realm holds the keys to completing our understanding of galaxy evolution, hierarchical assembly, and even the fundamental nature of dark matter. Our current theoretical models are inherently incomplete, largely mirroring the properties of the brightest, most easily observed objects. To overcome this critical bias and unlock the secrets of this realm, a transformative leap in observational capability is required. A 30 to 40m class telescope, leveraging unprecedented sensitivity and spatial resolution, especially with adaptive optics, is the essential tool to fundamentally probe these faint, low-density stellar regimes. This white paper details the transformative LSB science that such a facility, strategically positioned in the Northern Hemisphere (NH) to access crucial nearby structures and rich environments, can achieve.

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arXiv2025

The Spatial Distribution of Intra-Cluster Globular Clusters in the Fornax Cluster

We investigate the spatial distribution of the Intra-Cluster Globular Clusters (ICGCs) detected in the core of the Fornax galaxy cluster. By separately modeling different components of the observed population of Globular Clusters (GCs), we confirm the existence of an abundant ICGCs over-density with a geometrically complex, elongated morphology roughly centered on the cluster dominant galaxy NGC 1399 and stretching along the E-W direction. We identify several areas in the ICGCs distribution that deviate from a simple elliptical model and feature large density enhancements. These regions are characterized based on their statistical significance, GCs excess number, position, size and location relative to the galaxies in their surroundings. The relations between the spatial distribution and features of the ICGCs structures, mostly populated by blue GCs, and properties of the intra-cluster light and dwarf galaxies detected in the core of the Fornax cluster are described and discussed. The line-of-sight velocity distribution of spectroscopically confirmed GCs within the ICGCs structures is compatible with the systemic velocities of nearby bright galaxies in the Fornax cluster, suggesting that the ICGCs population is at least partially composed of GCs stripped from their hosts. We argue that the findings here presented suggest that, on sub-cluster scales, different mechanisms contribute to the growth of the ICGC. The western region of Fornax is likely associated with old merging events that predate the assembly of the Fornax cluster. The eastern side instead points to a mix of tidal disruption of dwarf galaxies and stripping from the GCSs of massive hosts, more typical of relaxed, high-density cluster environments.

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arXiv2025

Intra-Cluster Light as a Dynamical Clock for Galaxy Clusters: Insights from the MAGNETICUM, IllustrisTNG, Hydrangea and Horizon-AGN Simulations

As the most massive nodes of the cosmic web, galaxy clusters represent the best probes of structure formation. Over time, they grow by accreting and disrupting satellite galaxies, adding those stars to the brightest cluster galaxy (BCG) and the intra-cluster light (ICL). However, the formation pathways of different galaxy clusters can vary significantly. To inform upcoming large surveys, we aim to identify observables that can distinguish galaxy cluster formation pathways. Using four different hydrodynamical simulations, Magneticum, TNG100 of IllustrisTNG, Horizon-AGN, and Hydrangea, we study how the fraction of stellar mass in the BCG and ICL ($f_{ICL+BCG}$) relates to the galaxy cluster mass assembly history. For all simulations, $f_{ICL+BCG}$ is the best tracer for the time at which the cluster has accumulated 50% of its mass ($z_{f}$), performing better than other typical dynamical tracers, such as the subhalo mass fraction, the halo mass, and the center shift. More relaxed clusters have higher $f_{ICL+BCG}$, in rare cases up to 90%, while dynamically active clusters have lower fractions, down to 20%, which we find to be independent of the exact implemented baryonic physics. We determine the average increase in $f_{ICL+BCG}$ from stripping and mergers to be between 3-4% per Gyr. $f_{ICL+BCG}$ is tightly traced by the stellar mass ratio between the BCG and both the second (M12) and fourth (M14) most massive cluster galaxy. The average galaxy cluster has assembled half of its halo mass by $z_{f}=0.67$ (about 6 Gyr ago), though individual histories vary significantly from $z_{f}=0.06$ to $z_{f}=1.77$ (0.8 to 10 Gyr ago). As all four cosmological simulations consistently find that $f_{ICL+BCG}$ is an excellent tracer of the cluster dynamical state, upcoming surveys can leverage measurements of $f_{ICL+BCG}$ to statistically quantify the assembly of the most massive structures.

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arXiv2021

The Fornax Deep Survey (FDS) with the VST XI. The search for signs of preprocessing between the Fornax main cluster and Fornax A group

We investigate the structural properties of cluster and group galaxies by studying the Fornax main cluster and the infalling Fornax A group, exploring the effects of galaxy preprocessing in this showcase example. Additionally, we compare the structural complexity of Fornax galaxies to those in the Virgo cluster and in the field. Our sample consists of 582 galaxies from the Fornax main cluster and Fornax A group. We quantified the light distributions of each galaxy based on a combination of aperture photometry, Sérsic+PSF (point spread function) and multi-component decompositions, and non-parametric measures of morphology (Concentration $C$; Asymmetry $A$, Clumpiness $S$; Gini $G$; second order moment of light $M_{20}$), and structural complexity based on multi-component decompositions. These quantities were then compared between the Fornax main cluster and Fornax A group. The structural complexity of Fornax galaxies were also compared to those in Virgo and in the field. Overall, we find significant differences in the distributions of quantities derived from Sérsic profiles ($g'-r'$, $r'-i'$, $R_e$, and $\barμ_{e,r'}$), and non-parametric indices ($A$ and $S$) between the Fornax main cluster and Fornax A group. Moreover, we find significant cluster-centric trends with $r'-i'$, $R_e$, and $\barμ_{e,r'}$, as well as $A$, $S$, $G$, and $M_{20}$ for galaxies in the Fornax main cluster. We find the structural complexity of galaxies increases as a function of the absolute $r'$-band magnitude (and stellar mass), with the largest change occurring between -14 mag $\lesssim M_{r'}\lesssim$ -19 mag. This same trend was observed for galaxies in the Virgo cluster and in the field, which suggests that the formation or maintenance of morphological structures (e.g. bulges, bar) is largely dependent on the stellar mass of the galaxies, rather than their environment.

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arXiv2020

The Fornax Deep Survey with VST. IX. The catalog of sources in the FDS area, with an example study for globular clusters and background galaxies

This paper continues the series of the Fornax Deep Survey (FDS). Following the previous studies dedicated to extended Fornax cluster members, we present the catalogs of compact stellar systems in the Fornax cluster as well as extended background sources and point-like sources. We derive ugri photometry of ~1.7 million sources over the $\sim$21 sq. degree area of FDS centered on NGC1399. For a wider area, of $\sim$27 sq. degs extending in the direction of NGC1316, we provide gri data for ~3.1 million sources. To improve the morphological characterization of sources we generate multi-band image stacks by coadding the best seeing gri-band single exposures with a cut at FWHM<=0.9 arcsec. We use the multi-band stacks as detection frames. The identification of compact sources is obtained from a combination of photometric and morphometric selection criteria taking as reference the properties of sources with well-defined classification from the literature. We present a preliminary analysis of globular cluster (GC) distributions in the Fornax area. The study confirms and extends further previous results. We observe the inter-galactic population of GCs, a population of mainly blue GCs centered on NGC1399, extends over $\sim$0.9Mpc, with an ellipticity $\sim$0.65. Several sub-structures extend over $\sim$0.5Mpc along various directions. Two of these structures do not cross any bright galaxy; one of them appears to be connected to NGC1404, a bright galaxy close to the cluster core and particularly poor of GCs. Using the gri catalogs we analyze the GC distribution over the extended FDS area, and do not find any obvious GC sub-structure bridging the two brightest cluster galaxies, NGC1316 and NGC1399. Although NGC1316 is twice brighter of NGC1399 in optical bands we estimate a factor of 3-4 richer GC population around NGC1399 compared to NGC1316, out to galactocentric distances of 40 arcmin

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arXiv2019

Astroinformatics based search for globular clusters in the Fornax Deep Survey

In the last years, Astroinformatics has become a well defined paradigm for many fields of Astronomy. In this work we demonstrate the potential of a multidisciplinary approach to identify globular clusters (GCs) in the Fornax cluster of galaxies taking advantage of multi-band photometry produced by the VLT Survey Telescope using automatic self-adaptive methodologies. The data analyzed in this work consist of deep, multi-band, partially overlapping images centered on the core of the Fornax cluster. In this work we use a Neural-Gas model, a pure clustering machine learning methodology, to approach the GC detection, while a novel feature selection method ($Φ$LAB) is exploited to perform the parameter space analysis and optimization. We demonstrate that the use of an Astroinformatics based methodology is able to provide GC samples that are comparable, in terms of purity and completeness with those obtained using single band HST data (Brescia et al. 2012) and two approaches based respectively on a morpho-photometric (Cantiello et al. 2018b) and a PCA analysis (D'Abrusco et al. 2015) using the same data discussed in this work.

astro-ph.IM↗

arXiv2019

Intra-cluster GC-LMXB in the Fornax galaxy cluster

The formation of Low mass X-ray binaries (LMXB) is favored within dense stellar systems such as Globular Clusters (GCs). The connection between LMXB and Globular Clusters has been extensively studied in the literature, but these studies have always been restricted to the innermost regions of galaxies. We present a study of LMXB in GCs within the central 1.5 deg^2 of the Fornax cluster with the aim of confirming the existence of a population of LMXB in intra-cluster GCs and understand if their properties are related to the host GCs, to the environment or/and to different formation channels.

astro-ph.HE↗

arXiv2019

Halo mass estimates from the Globular Cluster populations of 175 Low Surface Brightness Galaxies in the Fornax Cluster

The halo masses $M_{halo}$ of low surface brightness (LSB) galaxies are critical measurements for understanding their formation processes. One promising method to estimate a galaxy's $M_{halo}$ is to exploit the empirical scaling relation between $M_{halo}$ and the number of associated globular clusters ($N_{\mathrm{GC}}$). We use a Bayesian mixture model approach to measure $N_{\mathrm{GC}}$ for 175 LSB ($23\leq\left\langle μ_{e,r} \right\rangle [\mathrm{mag\ arcsec}^{-2}]\leq 28$) galaxies in the Fornax cluster using the Fornax Deep Survey (FDS) data; this is the largest sample of low mass galaxies so-far analysed for this kind of study. The proximity of the Fornax cluster means that we can measure galaxies with much smaller physical sizes ($0.3\leq r_{e,r}\ [\mathrm{kpc}]\leq 9.5$) compared to previous studies of the GC systems of LSB galaxies, probing stellar masses down to $M_{*}\sim10^{5}\mathrm{M_{\odot}}$. The sample also includes \nudg\ ultra-diffuse galaxies (UDGs), with projected $r$-band half-light radii greater than 1.5 kpc. Our results are consistent with an extrapolation of the $M_{*}-M_{halo}$ relation predicted from abundance matching. In particular, our UDG measurements are consistent with dwarf sized halos, having typical masses between $10^{10}$ and $10^{11}\mathrm{M_{\odot}}$. Overall, our UDG sample is statistically indistinguishable from smaller LSB galaxies in the same magnitude range. We do not find any candidates likely to be as rich as some of those found in the Coma cluster. We suggest that environment might play a role in producing GC-rich LSB galaxies.

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arXiv2017

VEGAS-SSS II: Comparing the globular cluster systems in NGC3115 and NGC1399 using VEGAS and FDS survey data

We analyze the globular cluster (GC) systems in two very different galaxies, N3115 and N1399. With the papers of this series, we aim at highlighting common and different properties in the GC systems in galaxies covering a wide range of parameter space. We compare the GCs in N3115 and N1399 as derived from the analysis of u, g, and i band images taken with the VST telescope as part of the VEGAS and FDS surveys. We selected GC candidates using as reference the morpho-photometric and color properties of confirmed GCs. The surface density of GCs in N3115 reveal a morphology similar to the profile of field stars; the same is true when blue and red GCs are taken separately. The GC maps for N1399 are richer in structure and confirm the existence of an intracluster GC component. We confirm the presence of a spatial offset in the N1399 GC centroid and find that the centroid of the GCs for N3115 coincides well with the galaxy center. Both GC systems show unambiguous color bimodality in g-i and u-i. The azimuthal average of the radial density profiles in both galaxies reveals a larger spatial extent for the total GCs population with respect to the galaxy surface brightness profile. As for the specific frequency of GCs, Sn, we find it is a factor of two higher in N1399 than for N3115. By inspecting the radial behavior of the specific frequency, Sn(<r), for the total, blue, and red GCs, we find notable similarities between the trends for red GCs in the two targets. In spite of extremely different host environments, the red GCs in both cases appear closely linked to the light distribution of field stars. Blue GCs extend to larger galactocentric scales than red GCs, marking a significant difference between the two galaxies: the blue/red GCs and field stellar components of N3115 appear well thermalized with each other and the blue GCs in N1399 appear to fade into an unrelaxed intracluster GC population.

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arXiv2017

A VST and VISTA study of globular clusters in NGC253

Aims. We analyze the properties of the sources in the NGC253 to define an up to date catalog of GC candidates in the galaxy. Methods. Our analysis is based on the science verification data of two ESO survey telescopes, VST and VISTA. Using ugri photometry from VST and JKs from VISTA, GC candidates were selected using the morpho-photometric and color properties of spectroscopically confirmed GCs available in the literature. The strength of the results was verified against available archival HST/ACS data from the GHOSTS survey. Results. The adopted GC selection leads to the definition of a sample of ~350 GC candidates. At visual inspection, we find that 82 objects match all the requirements for selecting GC candidates and 155 are flagged as uncertain GC candidate; 110 are unlikely GCs, most likely background galaxies. Furthermore, our analysis shows that four of the previously spectroscopically confirmed GCs, i.e., ~20% of the total spectroscopic sample, are more likely either background galaxies or high-velocity Milky Way stars. The radial density profile of the selected best candidates shows the typically observed r1/4-law radial profile. The analysis of the color distributions reveals only marginal evidence of the presence of color bimodality, which is normally observed in galaxies of similar luminosity. The GC luminosity function does not show the typical symmetry, mainly because of the lack of bright GCs. Part of the bright GCs missing might be at very large galactocentric distances or along the line of sight of the galaxy dusty disk. Conclusions. Using ugriJKs photometry we purged the list of GCs with spectroscopic membership and photometric GC candidates in NGC 253. Our results show that the use of either spectroscopic or photometric data only does not generally ensure a contaminant-free sample and a combination of both spectroscopy and photometry is preferred.

astro-ph.GA↗

arXiv2014

VEGAS-SSS. A VST survey of elliptical galaxies in the southern hemisphere: analysis of small stellar systems. Testing the methodology on the globular cluster system in NGC3115

We present a study of globular clusters (GCs) and other small stellar systems (SSSs) in the field of NGC3115, observed as part of the VEGAS imaging survey, carried out with the VST telescope. We use deep g and i data of NGC3115, a well-studied lenticular galaxy with excellent scientific literature. This is fundamental to test the methodologies, verify the results, and probe the capabilities of the VEGAS-SSS. Leveraging the large field of view of the VST allow us to accurately study of the distribution and properties of SSSs as a function of galactocentric distance Rgc, well beyond ~20 galaxy effective radii, in a way not often possible. Our analysis of colors, magnitudes and sizes of SSS candidates confirms the results from existing studies, some of which carried out with 8-10m class telescopes, and further extends them to unreached Rgc distances, with similar accuracy. We find a color bimodality for the GC population and a r1/4 profile for the surface density of GCs as for the galaxy light profile. The radial color gradient of blue and red GCs previously found, for instance by the SLUGGS survey, is further extended out to the largest Rgc inspected, ~65 kpc. The surface density profiles of blue and red GCs taken separately are well approximated by a r1/4 density profile, with the fraction of blue GCs being slightly larger at larger Rgc. We do not find hints of a trend for the red GC and for the GC turnover magnitude to vary with radius, but we observe a ~0.2 mag difference in the turnover magnitude of the blue and red GCs subpopulations. Inspecting SSS sizes and colors we obtained a list of UCDs and GC candidates suitable for future spectroscopic follow-up. In conclusion, our study shows the reliability of the methodologies developed to study SSSs in the field of bright early-type galaxies, and the great potential of the VEGAS survey to produce original results on SSSs science.

astro-ph.GA↗

arXiv2014

A panoramic VISTA of the stellar halo of NGC 253

Outskirts of large galaxies contain important information about the galaxy formation and assembly process, and resolved star count studies can probe the extremely low surface brightness of the outer halos. We use images obtained with the VISTA telescope to construct spatially resolved J vs Z-J colour-magnitude diagrams (CMDs) of NGC 253, a nearly edge-on disk galaxy in the Sculptor group. The very deep photometry, down to J ~ 23.5, and the wide area covered allows us to trace the red giant branch (RGB) and asymptotic giant branch (AGB) stars that belong to the outer disk and the halo of NGC 253, out to 50 kpc along the galaxy minor axis. We confirm the existence of an extra planar stellar component of the disk, with a very prominent southern shelf and a symmetrical feature on the north side. The only additional visible sub-structure is an overdensity in the north-west part of the halo at about 28 kpc from the plane and extending over ~ 20 kpc parallel with the disk of the galaxy. From the stellar count profile along the major axis we measure the transition from the disk to the halo at a radial distance of about 25 kpc, where a clear break appears in the number density profile. The isodensity contours show that the inner halo is a flattened structure that blends with a more extended, diffuse, rounder outer halo. Such external structure can be traced to the very edge of our image out to 50 kpc from the disk plane. The number density profile of the stars in the stellar halo follows a power law with index -1.6, as function of radius. The CMD shows a very homogeneous stellar population across the whole field; by comparison with theoretical isochrones we conclude that the RGB stars are ~ 8 Gyr old or more, while the AGB stars trace a population of about 2 x 10^8 Mo, formed from ~ 0.5 to a few Gyr ago. Surprisingly, part of this latter population appears scattered over a wide area.

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arXiv2012

A tale of two tails and an off-centered envelope: diffuse light around the cD galaxy NGC 3311 in the Hydra I cluster

The formation of intracluster light and of the extended halos around brightest cluster galaxies is closely related to morphological transformation, tidal stripping, and disruption of galaxies in clusters. We analyze Ks- and V-band surface photometry as well as deep long-slit spectra, and establish a link between the structures in the light distribution, the absorption line kinematics, and the LOS velocity distributions of nearby galaxies and planetary nebulae (PNs). The central galaxy NGC 3311 is surrounded by an extended symmetric outer halo with n=10 and an additional, off-centered envelope ~ 50" to the North-East. Its luminosity L_V= 1.2x10^{10} +/- 6.0 x 10^8 L_sun corresponds to ~50 % of the luminosity of the symmetric halo in the same region. Based on measured PN velocities, at least part of the off-centered envelope consists of high-velocity accreted stars. We have also discovered two tidal streams in the cluster center, emerging from the dwarf galaxy HCC 026 and from the S0 galaxy HCC 007. The HCC 026 stream is redshifted by ~1200 km/s with respect to NGC 3311, similarly as HCC 026 itself, a fraction of PNs in the off-centered envelope, and several other dwarf galaxies nearby. The stars in one of the HCC 026 tails are known to be consistent with the low-metallicity population of HCC 026, and our photometry shows that this galaxy is already mostly dissolved in the tidal field. The tidal stream around HCC 007 extends over at least 110 kpc. It is fairly thick and is brighter on the side of the asymmetric outer halo of NGC 3311, which it may join. Its luminosity is several 10^9 L_sun, similar to the luminosity of the stripped-down galaxy HCC 007. The redshift of the stream is determined from a few PN velocities and is similar to that for HCC 007 and HCC 026.

astro-ph.CO↗

arXiv2003

Polar Ring Galaxies and the Tully-Fisher relation

We have investigated the Tully-Fisher relation for Polar Ring Galaxies (PRGs), based on near infrared, optical and HI data available for a sample of these peculiar objects. Many PRGs show larger HI line-widths than expected for the observed K band luminosity, and this result is confirmed by a larger sample of objects, based on B-band data. This observational evidence may be related to the dark halo shape and orientation in these systems: the larger rotation velocities observed in PRGs can be explained by a flattened polar halo, aligned with the polar ring.

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