Browsing by Author "Coccato, L."

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    Comparing the properties of the X-shaped bulges of NGC 4710 and the Milky Way with MUSE
    (2016) Rejkuba, M.; Valenti, E.; Zoccali, Manuela; Coccato, L.; Minniti, D.; Ness, M.; Gonzalez, O.; Gadotti, D.; Debattista, V.
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    Fornax3D project: Assembly history of massive early-type galaxies in the Fornax cluster from deep imaging and integral field spectroscopy
    (2022) Spavone, M.; Iodice, E.; D'Ago, G.; van de Ven, G.; Morelli, L.; Corsini, E. M.; Sarzi, M.; Coccato, L.; Fahrion, K.; Falcon-Barroso, J.; Gadotti, D. A.; Lyubenova, M.; Martin-Navarro, I.; McDermid, R. M.; Pinna, F.; Pizzella, A.; Poci, A.; de Zeeuw, P. T.; Zhu, L.
    This work is based on high-quality integral-field spectroscopic data obtained with the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT). The 21 brightest (m(B) <= 15 mag) early-type galaxies (ETGs) inside the virial radius of the Fornax cluster are observed out to distances of similar to 2-3 R-e. Deep imaging from the VLT Survey Telescope (VST) is also available for the sample ETGs. We investigated the variation of the galaxy structural properties as a function of the total stellar mass and cluster environment. Moreover, we correlated the size scales of the luminous components derived from a multi-component decomposition of the VST surface-brightness radial profiles of the sample ETGs with the MUSE radial profiles of stellar kinematic and population properties. The results are compared with both theoretical predictions and previous observational studies and used to address the assembly history of the massive ETGs of the Fornax cluster. We find that galaxies in the core and north-south clump of the cluster, which have the highest accreted mass fraction, show milder metallicity gradients in their outskirts than the galaxies infalling into the cluster. We also find a segregation in both age and metallicity between the galaxies belonging to the core and north-south clump and the infalling galaxies. The new findings fit well within the general framework for the assembly history of the Fornax cluster.
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    INSPIRE: INvestigating Stellar Population In RElics - IV. The initial mass function slope in relics
    (2023) Martin-Navarro, Ignacio; Spiniello, C.; Tortora, C.; Coccato, L.; D'Ago, G.; Ferre-Mateu, A.; Pulsoni, C.; Hartke, J.; Arnaboldi, M.; Hunt, L.; Napolitano, N. R.; Scognamiglio, D.; Spavone, M.
    In the last decade, growing evidence has emerged supporting a non-universal stellar initial mass function (IMF) in massive galaxies, with a larger number of dwarf stars with respect to the Milky Way (bottom-heavy IMF). However, a consensus about the mechanisms that cause IMF variations is yet to be reached. Recently, it has been suggested that stars formed early-on in cosmic time, via a star formation burst, could be characterized by a bottom-heavy IMF. A promising way to confirm this is to use relics, ultra-compact massive galaxies, almost entirely composed by these 'pristine' stars. The INvestigating Stellar Population In RElics (INSPIRE) Project aims at assembling a large sample of confirmed relics, that can serve as laboratory to investigate on the conditions of star formation in the first 1-3 Gyr of the Universe. In this third INSPIRE paper, we build a high signal-to-noise spectrum from five relics, and one from five galaxies with similar sizes, masses, and kinematical properties, but characterized by a more extended star formation history (non-relics). Our detailed stellar population analysis suggests a systematically bottom-heavier IMF slope for relics than for non-relics, adding new observational evidence for the non-universality of the IMF at various redshifts and further supporting the above proposed physical scenario.
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    INSPIRE: INvestigating Stellar Population In RElics II. First data release (DR1)
    (2021) Spiniello, C.; Tortora, C.; D'Ago, G.; Coccato, L.; La Barbera, F.; Ferre-Mateu, A.; Pulsoni, C.; Arnaboldi, M.; Gallazzi, A.; Hunt, L.; Napolitano, N. R.; Radovich, M.; Scognamiglio, D.; Spavone, M.; Zibetti, S.
    Context. The INvestigating Stellar Population In RElics (INSPIRE) is an ongoing project targeting 52 ultra-compact massive galaxies at 0.1 < z < 0.5 with the X-shooter at VLT spectrograph (XSH). These objects are the ideal candidates to be `relics', massive red nuggets that have formed at high redshift (z > 2) through a short and intense star formation burst, and then have evolved passively and undisturbed until the present day. Relics provide a unique opportunity to study the mechanisms of star formation at high-z. Aims. INSPIRE is designed to spectroscopically confirm and fully characterise a large sample of relics, computing their number density in the redshift window 0:1 < z < 0:5 for the first time, thus providing a benchmark for cosmological galaxy formation simulations. In this paper, we present the INSPIRE Data Release (DR1), comprising 19 systems with observations completed in 2020. Methods. We use the methods already presented in the INSPIRE Pilot, but revisiting the 1D spectral extraction. For the 19 systems studied here, we obtain an estimate of the stellar velocity dispersion, fitting the two XSH arms (UVB and VIS) separately at their original spectral resolution to two spectra extracted in di fferent ways. We estimate [Mg /Fe] abundances via line-index strength and mass-weighted integrated stellar ages and metallicities with full spectral fitting on the combined (UVB +VIS) spectrum. Results. For each system, di fferent estimates of the velocity dispersion always agree within the errors. Spectroscopic ages are very old for 13 /19 galaxies, in agreement with the photometric ones, and metallicities are almost always (18 /19) super-solar, confirming the mass-metallicity relation. The [Mg /Fe] ratio is also larger than solar for the great majority of the galaxies, as expected. We find that ten objects formed more than 75% of their stellar mass (M-*) within 3 Gyr from the big bang and classify them as relics. Among these, we identify four galaxies that had already fully assembled their M-* by that time and are therefore `extreme relics' of the ancient Universe. Interestingly, relics, overall, have a larger [Mg /Fe] and a more metal-rich stellar population. They also have larger integrated velocity dispersion values compared to non-relics (both ultra-compact and normal-size) of similar stellar mass. Conclusions. The INSPIRE DR1 catalogue of ten known relics is the largest publicly available collection, augmenting the total number of confirmed relics by a factor of 3.3, and also enlarging the redshift window. The resulting lower limit for the number density of relics at 0.17 < z < 0.39 is rho similar to 9.1 x 10(-8) Mpc(-3).
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    INSPIRE: INvestigating Stellar Population In RElics III. Second data release (DR2): testing the systematics on the stellar velocity dispersion
    (2023) D'Ago, G.; Spiniello, C.; Coccato, L.; Tortora, C.; La Barbera, F.; Arnaboldi, M.; Bevacqua, D.; Ferre-Mateu, A.; Gallazzi, A.; Hartke, J.; Hunt, L. K.; Martin-Navarro, I.; Napolitano, N. R.; Pulsoni, C.; Radovich, M.; Saracco, P.; Scognamiglio, D.; Zibetti, S.
    Context. The project called INvestigating Stellar Population In RElics (INSPIRE) is based on VLT/X-shooter data from the homonymous on-going ESO Large Program. It targets 52 ultra-compact massive galaxies at 0.1 < z < 0.5 with the goal of constraining their kinematics and stellar population properties in great detail and of analysing their relic nature.
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    INSPIRE: INvestigating Stellar Population In RElics: I. Survey presentation and pilot study
    (2021) Spiniello, C.; Tortora, C.; D'Ago, G.; Coccato, L.; La Barbera, F.; Ferre-Mateu, A.; Napolitano, N. R.; Spavone, M.; Scognamiglio, D.; Arnaboldi, M.; Gallazzi, A.; Hunt, L.; Moehler, S.; Radovich, M.; Zibetti, S.
    Context. Massive elliptical galaxies are thought to form through a two-phase process. At early times (z> 2), an intense and fast starburst forms blue and disk-dominated galaxies. After quenching, the remaining structures become red, compact, and massive (i.e. red nuggets). Then, a time-extended second phase, which is dominated by mergers, causes structural evolution and size growth. Given the stochastic nature of mergers, a small fraction of red nuggets survive, without any interaction, massive and compact until today: these are relic galaxies. Since this fraction depends on the processes dominating the size growth, counting relics at low-z is a valuable way of disentangling between different galaxy evolution models.Aims. In this paper, we introduce the INvestigating Stellar Population In RElics (INSPIRE) Project, which aims to spectroscopically confirm and fully characterise a large number of relics at 0.1< z< 0.5. We focus here on the first results based on a pilot study targeting three systems, representative of the whole sample.Methods. For these three candidates, we extracted 1D optical spectra over an aperture of r=0.40 '', which comprises similar to 30% of the galaxies' light, and we obtained the line-of-sight integrated stellar velocity and velocity dispersion. We also inferred the stellar [alpha /Fe] abundance from line-index measurements and mass-weighted age and metallicity from full-spectral fitting with single stellar population models.Results. Two galaxies have large integrated stellar velocity dispersion values (sigma (star)similar to 250 km s(-1)), confirming their massive nature. They are populated by stars with super-solar metallicity and [alpha /Fe]. Both objects have formed >= 80% of their stellar mass within a short (similar to 0.5-1.0 Gyr) initial star formation episode occurred only similar to 1 Gyr after the Big Bang. The third galaxy has a more extended star formation history and a lower velocity dispersion. Thus we confirm two out of three candidates as relics.Conclusions. This paper is the first step towards assembling the final INSPIRE catalogue that will set stringent lower limits on the number density of relics at z< 0.5, thus constituting a benchmark for cosmological simulations, and their predictions on number densities, sizes, masses, and dynamical characteristics of these objects.