Browsing by Author "Spiniello, Chiara"

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    Building the Largest Spectroscopic Sample of Ultracompact Massive Galaxies with the Kilo Degree Survey
    (IOP PUBLISHING LTD, 2020) Scognamiglio, Diana; Tortora, Crescenzo; Spavone, Marilena; Spiniello, Chiara; Napolitano, Nicola R.; D'Ago, Giuseppe; La Barbera, Francesco; Getman, Fedor; Roy, Nivya; Raj, Maria Angela; Radovich, Mario; Brescia, Massimo; Cavuoti, Stefano; Koopmans, Leon V. E.; Kuijken, Koen H.; Longo, Giuseppe; Petrillo, Carlo Enrico
    Ultracompact massive galaxies (UCMGs), i.e., galaxies with stellar masses M. > 8 ' 1010M. and effective radii Re < 1.5 kpc, are very rare systems, in particular at low and intermediate redshifts. Their origin as well as their number density across cosmic time are still under scrutiny, especially because of the paucity of spectroscopically confirmed samples. We have started a systematic census of UCMG candidates within the ESO Kilo Degree Survey, together with a large spectroscopic follow-up campaign to build the largest possible sample of confirmed UCMGs. This is the third paper of the series and the second based on the spectroscopic follow-up program. Here, we present photometrical and structural parameters of 33 new candidates at redshifts 0.15. z. 0.5 and confirm 19 of them as UCMGs, based on their nominal spectroscopically inferred M. and Re. This corresponds to a success rate of 58%, nicely consistent with our previous findings. The addition of these 19 newly confirmed objects allows us to fully assess the systematics on the system selection-and to finally reduce the number density uncertainties. Moreover, putting together the results from our current and past observational campaigns and some literature data, we build the largest sample of UCMGs ever collected, comprising 92 spectroscopically confirmed objects at 0.1. z. 0.5. This number raises to 116, allowing for a 3s tolerance on the M. and Re thresholds for the UCMG definition. For all these galaxies, we have estimated the velocity dispersion values at the effective radii, which have been used to derive a preliminary mass-velocity dispersion correlation.
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    Formation of an ultra-diffuse galaxy in the stellar filaments of NGC 3314A: Caught in the act?
    (2021) Iodice, Enrichetta; La Marca, Antonio; Hilker, Michael; Cantiello, Michele; D'Ago, Giuseppe; Gullieuszik, Marco; Rejkuba, Marina; Arnaboldi, Magda; Spavone, Marilena; Spiniello, Chiara; Forbes, Duncan A.; Greggio, Laura; Rampazzo, Roberto; Mieske, Steffen; Paolillo, Maurizio; Schipani, Pietro
    The VEGAS imaging survey of the Hydra I cluster has revealed an extended network of stellar filaments to the south-west of the spiral galaxy NGC 3314A. Within these filaments, at a projected distance of similar to 40 kpc from the galaxy, we discover an ultra-diffuse galaxy (UDG) with a central surface brightness of mu(0,g) similar to 26 mag arcsec(-2) and effective radius R-e similar to 3.8 kpc. This UDG, named UDG 32, is one of the faintest and most diffuse low-surface-brightness galaxies in the Hydra I cluster. Based on the available data, we cannot exclude that this object is just seen in projection on top of the stellar filaments and is thus instead a foreground or background UDG in the cluster. However, the clear spatial coincidence of UDG 32 with the stellar filaments of NGC 3314A suggests that it might have formed from the material in the filaments, becoming a detached, gravitationally bound system. In this scenario, the origin of UDG 32 depends on the nature of the stellar filaments in NGC 3314A, which is still unknown. The stellar filaments could result from ram-pressure stripping or have a tidal origin. In this letter we focus on the comparison of the observed properties of the stellar filaments and of UDG 32 and speculate on their possible origin. The relatively red colour (g - r=0.54 +/- 0.14 mag) of the UDG, similar to that of the disk in NGC 3314A, combined with an age older than 1 Gyr and the possible presence of a few compact stellar systems, points towards a tidal formation scenario.
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    Galaxy populations in the Hydra I cluster from the VEGAS survey I. Optical properties of a large sample of dwarf galaxies
    (2022) La Marca, Antonio; Peletier, Reynier; Iodice, Enrichetta; Paolillo, Maurizio; Challapa, Nelvy Choque; Venhola, Aku; Forbes, Duncan A.; Cantiello, Michele; Hilker, Michael; Rejkuba, Marina; Arnaboldi, Magda; Spavone, Marilena; D'Ago, Giuseppe; Raj, Maria Angela; Ragusa, Rossella; Mirabile, Marco; Rampazzo, Roberto; Spiniello, Chiara; Mieske, Steffen; Schipani, Pietro
    Context. Due to their relatively low stellar mass content and diffuse nature, the evolution of dwarf galaxies can be strongly affected by their environment. Analyzing the properties of the dwarf galaxies over a wide range of luminosities, sizes, morphological types, and environments, we can obtain insights about their evolution. At similar to 50 Mpc, the Hydra I cluster of galaxies is among the closest cluster in the z similar or equal to 0 Universe, and an ideal environment to study dwarf galaxy properties in a cluster environment.
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    Galaxy populations in the Hydra I cluster from the VEGAS survey II. The ultra-diffuse galaxy population
    (2022) La Marca, Antonio; Iodice, Enrichetta; Cantiello, Michele; Forbes, Duncan A.; Rejkuba, Marina; Hilker, Michael; Arnaboldi, Magda; Greggio, Laura; Spiniello, Chiara; Mieske, Steffen; Venhola, Aku; Spavone, Marilena; D'Ago, Giuseppe; Raj, Maria Angela; Ragusa, Rossella; Mirabile, Marco; Rampazzo, Roberto; Peletier, Reynier; Paolillo, Maurizio; Challapa, Nelvy Choque; Schipani, Pietro
    In this work, we extend the catalog of low-surface brightness (LSB) galaxies, including ultra-diffuse galaxy (UDG) candidates, within approximate to 0.4R(vir) of the Hydra I cluster of galaxies based on deep images from the VST Early-type GAlaxy Survey (VEGAS). The new galaxies were found by applying an automatic detection tool and carrying out additional visual inspections of g and r band images. This led to the detection of 11 UDGs and 8 more LSB galaxies. For all of them, we assessed the cluster membership using the color-magnitude relation derived for early-type giant and dwarf galaxies in Hydra I. The UDGs and new LSB galaxies found in Hydra I span a wide range of central surface brightness (22.7 less than or similar to mu(0.g) less than or similar to 26.5 mag arcse(-2)), effective radius (0.6 less than or similar to R-e less than or similar to 4.0 kpc), and color (0.4 <= g-r <= 0.9 mag), and have stellar masses in the range similar to 5 x 10(6)-2 x 10(8) M-circle dot. The 2D projected distribution of both galaxy types is similar to the spatial distribution of dwarf galaxies, with over-densities in the cluster core and north of the cluster center. They have similar color distribution and comparable stellar masses to the red dwarf galaxies. Based on photometric selection, we identify a total of nine globular cluster (GC) candidates associated to the UDGs and four to the LSB galaxies, with the highest number of candidates in an individual UDG being three. We find that there are no relevant differences between dwarfs, LSB galaxies, and UDGs: the structural parameters (i.e., surface brightness, size, color, and n-index) and GC content of the three classes have similar properties and trends. This finding is consistent with UDGs being the extreme LSB tail of the size-luminosity distribution of dwarfs in this environment.
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    The elemental abundance of quiescent galaxies in the LEGA-C survey: the (non-)evolution of [α/Fe] from z=0.75 to z=0
    (2023) Bevacqua, Davide; Saracco, Paolo; La Barbera, Francesco; D'Ago, Giuseppe; De Propris, Roberto; Ferreras, Ignacio; Gallazzi, Anna; Pasquali, Anna; Spiniello, Chiara
    We measure the [alpha/Fe] abundances for 183 quiescent galaxies at z = 0.60-0.75 with stellar masses ranging 10.4 <= log(10)(M-*/M-circle dot) <= 11.6 selected from the Large Early Galaxy Astrophysics Census survey. We estimate [alpha/Fe] from the ratio of the spectral indices Mgb (lambda similar to 5177 angstrom) and Fe4383, compared to predictions of simple stellar population models. We find that 91 percent of quiescents in our sample have supersolar [alpha/Fe], with an average value of [alpha/Fe] = +0.24 +/- 0.01. We find no significant correlation between [alpha/Fe] and stellar metallicity, mass, velocity dispersion, and average formation time. Galaxies that formed the bulk of their stellar mass on time-scales shorter than 1 Gyr follow the same [alpha/Fe] distribution as those which formed on longer time-scales. In comparison to local early-type galaxies and to stacked spectra of quiescent galaxies at z = 0.38 and z = 0.07, we find that the average [alpha/Fe] has not changed between z = 0.75 and the present time. Our work shows that the vast majority of massive quiescent galaxies at z similar to 0.7 are alpha-enhanced, and that no detectable evolution of the average [alpha/Fe] has taken place over the last similar to 6.5 Gyr.
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    The Fornax Cluster VLT Spectroscopic Survey III. Kinematical characterisation of globular clusters in the Fornax galaxy cluster
    (2022) Chaturvedi, Avinash; Hilker, Michael; Cantiello, Michele; Napolitano, Nicola R.; van de Ven, Glenn; Spiniello, Chiara; Fahrion, Katja; Paolillo, Maurizio; Gatto, Massimiliano; Puzia, Thomas
    The Fornax cluster provides an unparalleled opportunity of investigating the formation and evolution of early-type galaxies in a dense environment in detail. We aim at kinematically characterising photometrically detected globular cluster (GC) candidates in the core of the cluster. We used spectroscopic data from the Visible Multi Object Spectrograph at Very Large Telescope (VLT/VIMOS) from the FVSS survey in the Fornax cluster, covering one square degree around the central massive galaxy NGC 1399. We confirm a total of 777 GCs, almost doubling previously detected GCs, using the same dataset as was used before. Combined with previous literature radial velocity measurements of GCs in Fornax, we compile the most extensive spectroscopic GC sample of 2341 objects in this environment. We found that red GCs are mostly concentrated around major galaxies, while blue GCs are kinematically irregular and are widely spread throughout the core region of the cluster. The velocity dispersion profiles of blue and red GCs show a quite distinct behaviour. Blue GCs exhibit a sharp increase in the velocity dispersion profile from 250 to 400 km s(-1) within 5 arcmin (similar to 29 kpc/similar to 1 r(eff) of NGC 1399) from the central galaxy. The velocity dispersion profile of red GCs follows a constant value between 200 and 300 km s(-1) until 8 arcmin (similar to 46 kpc/similar to 1.6 r(eff)), and then rises to 350 km s(-1) at 10 arcmin (similar to 58 kpc/similar to 2 r(eff)). Beyond 10 arcmin and out to 40 arcmin (similar to 230 kpc/ similar to 8 r(eff)), blue and red GCs show a constant velocity dispersion of 300 +/- 50 km s(-1), indicating that both GC populations trace the cluster potential. We kinematically confirm and characterise the previously photometrically discovered overdensities of intra-cluster GCs. We found that these substructured intra-cluster regions in Fornax are dominated mostly by blue GCs.