arXiv subjects

Rosa Calvi

Publications and source records attributed to Rosa Calvi.

14 recordsLinked to original sources

arXiv2026

Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra-I cluster. VI. A star-forming UDG in Hydra I: a rare UDG or a transition phase?

This paper presents a detailed analysis of a gas-rich star-forming ultra-diffuse galaxy (UDG) as part of the ESO Large Programme 'Looking into the faintEst WIth MUSE (LEWIS)'. Among the UDGs in the LEWIS sample, UDG 6 is the only galaxy that hosts a significant amount of ionised gas with evidence of emission lines, suggesting recent star-forming activity. The main goal of this work is to constrain the formation history of this UDG by comparing its properties with the main formation scenarios proposed for this extreme class of galaxies. We adopted integral field spectroscopy from MUSE to derive the morphology and the structural properties of the stellar and gas components of UDG 6. We applied spectral fitting and Voronoi tessellation algorithms to the MUSE data-cube to derive the kinematics and properties of the gas and stellar component. Moreover, we derived the GCs populations' properties by applying a multi-band spectrophotometric analysis. We confirmed that UDG 6 is a member of Hydra I cluster. It is characterised by a regular and elongated shape and contains a significant dust content, a metal-poor ionised gas fraction and an underlying old-to-intermediate stellar component. Evidence of local and clumpy star-forming activity has been revealed through the analysis of emission line, and an arc-like tidal feature was discovered from unsharp masking analysis. UDG 6 might originate from a 'puffed-up dwarf' whose stellar content has been stretched out to larger radii, passively evolving into a more diffuse galaxy. Being located in a dynamically active region of the cluster, characterised by tidal features and stripping phenomena, we suggest that the environmental processes have played a role in shaping the properties of UDG 6. A tidal interaction with a nearby galaxy might have triggered recent star-formation activity, without dramatically altering the coherent gas rotation in UDG 6.

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arXiv2025

Arp@VST: Legacy Survey of the Arp Peculiar Galaxies with the VST

Arp@VST is a public observing programme, conducted at the VLT Survey Telescope (VST) hosted at ESO's Paranal Observatory. It aims to revisit the Arp catalogue by creating a public survey. The Atlas of Peculiar Galaxies was produced by Halton Arp in 1966 and contains 338 galaxies with distorted morphologies and/or interacting systems. Given the excellent capabilities of the VST to map the galaxies' structure down to low surface brightness levels, for this project we will acquire deep, multi-band (g, r, i, H{\alpha}) images for all the Arp galaxies visible from Paranal Observatory (Declination < +10 deg). Being a public survey, the reduced data will be released via the ESO Science Archive as soon as they are processed.

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arXiv2024

Galaxy populations in the Hydra I cluster from the VEGAS survey III. The realm of low surface brightness features and intra-cluster light

In this paper, we analyse the light distribution in the Hydra I cluster of galaxies to explore their low surface brightness features, measure the intra-cluster light, and address the assembly history of the cluster. For this purpose, we used deep wide-field g- and r-band images obtained with the VST as part of the VEGAS project. The VST mosaic covers ~0.4 times the virial radius around the core of the cluster, which enabled us to map the light distribution down to faint surface brightness levels of mu_g ~ 28 mag/arcsec^2. In this region of the cluster, 44 cluster members are brighter than m_B<16 mag, and the region includes more than 300 dwarf galaxies. Similar to the projected distribution of all cluster members (bright galaxies and dwarfs), we find that the bulk of the galaxy light is concentrated in the cluster core, which also emits in the X-rays, and there are two overdensities: in the north (N) and south-east (SE) with respect to the cluster core. We present the analysis of the light distribution of all the bright cluster members. After removing foreground stars and other objects, we measured the diffuse intra-cluster light and compared its distribution with that of the globular clusters and dwarf galaxies in the cluster. We find that most of the diffuse light low surface brightness features, and signs of possible gravitational interaction between galaxies reside in the core and in the group in the N, while ram-pressure stripping is frequently found to affect galaxies within the SE group. All these features confirm that the mass assembly in this cluster is still ongoing. By combining the projected phase-space with these observed properties, we trace the different stages of the assembly history. We also address the main formation channels for the intra-cluster light detected in the cluster, which contributes ~ 12% to the total luminosity of the cluster.

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arXiv2022

Signs of environmental effects on star-forming galaxies in the Spiderweb protocluster at z=2.16

We use multi-object near-infrared (NIR) spectroscopy with VLT/KMOS to investigate the role of the environment in the evolution of the ionized gas properties of narrow-band selected H$\alpha$ emitters (HAEs) in the Spiderweb protocluster at $z=2.16$. Based on rest-frame optical emission lines, H$\alpha$ and [NII]$\lambda$6584, we confirm the cluster membership of 39 of our targets (i.e. 93% success rate), and measure their star-formation rates (SFR), gas-phase oxygen abundances and effective radius. We parametrize the environment where our targets reside by using local and global density indicators based on previous samples of spectroscopic and narrow-band cluster members. We find that star-forming galaxies embedded in the Spiderweb protocluster display SFRs compatible with those of the main sequence and morphologies comparable to those of late-type galaxies at $z=2.2$ in the field. We also report a mild gas-phase metallicity enhancement ($0.6\pm0.3$ dex) at intermediate stellar masses. Furthermore, we identify two UVJ-selected quiescent galaxies with residual H$\alpha$-based star formation and find signs of extreme dust obscuration in a small sample of SMGs based on their FIR and H$\alpha$ emission. Interestingly, the spatial distribution of these objects differs from the rest of HAEs, avoiding the protocluster core. Finally, we explore the gas fraction-gas metallicity diagram for 7 galaxies with molecular gas masses measured by ATCA using CO(1-0). In the context of the gas-regulator model, our objects are consistent with relatively low mass-loading factors, suggesting lower outflow activity than field samples at the cosmic noon and thus, hinting at the onset of environmental effects in this massive protocluster.

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arXiv2021

Is the Bremer Deep Field ionised, at z~7?

We show herein that the population of star forming galaxies in the Bremer Deep Field (BDF) have enough ionising power to form two large ionised bubbles which could be in the process of merging into a large one with a volume of 14000 cMpc3. The sources identified in the BDF have been completed with a set of expected low luminosity sources at z $\approx$ 7. We have estimated the number of ionising photons per second produced by the different star forming galaxies in the BDF. This number has been compared with the number that would be required to ionise the bubbles around the two overdense regions. We have used, as reference, ionising emissivities derived from the AMIGA cosmological evolutionary model. We find that even using the most conservative estimates, with a Lyman continuum escape fraction of 10\% the two regions we have defined within the BDF would be reionised. Assuming more realistic estimates of the ionising photon production efficiency, both bubbles would be in the process of merging into a large reionised bubble, such as those that through percolation completed the reionisation of the universe by z = 6. The rather small values of the escape fraction required to reionise the BDF are compatible with the low fraction of faint Lyα emitters identified in the BDF. Finally, we confirm that the low luminosity sources represent indeed the main contributors to the BDF ionising photon production.

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arXiv2019

MOS spectroscopy of protocluster candidate galaxies at z=6.5

The epoch corresponding to a redshift of z $\sim 6.5$ is close to full re-ionisation of the Universe, and early enough to provide an intriguing environment to observe the early stage of large-scale structure formation. It is also en epoch that can be used to verify the abundance of a large population of low luminosity star-forming galaxies, that are deemed responsible for cosmic re-ionisation. Here, we present the results of follow-up multi-object spectroscopy using OSIRIS at Gran Telescopio Canarias (GTC) of 16 Ly$α$ emitter (LAE) candidates discovered in the Subaru/XMM Newton Deep Survey. We have securely confirmed 10 LAEs with sufficient signal-to-noise ratio of the Ly$α$ emission line. The inferred star formation rates of the confirmed LAEs are on the low side, within the range 0.9-4.7 M$_{\odot}$ yr$^{-1}$. However, they show relatively high Ly$α$ rest frame equivalent widths. Finally we have shown that the mechanical energy released by the star formation episodes in these galaxies is enough to create holes in the neutral hydrogen medium such that Lyman continuum photons can escape to the intergalactic medium, thus contributing to the re-ionisation of the Universe.

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arXiv2015

The star formation history of galaxies: the role of galaxy mass, morphology and environment

We analyze the star formation history (SFH) of galaxies as a function of present-day environment, galaxy stellar mass and morphology. The SFH is derived by means of a non-parametric spectrophotometric model applied to individual galaxies at z ~ 0.04- 0.1 in the WINGS clusters and the PM2GC field. The field reconstructed evolution of the star formation rate density (SFRD) follows the values observed at each redshift (Madau & Dickinson 2014), except at z > 2 where our estimate is ~ 1.7x higher than the high-z observed value. The slope of the SFRD decline with time gets progressively steeper going from low mass to high mass haloes. The decrease of the SFRD since z = 2 is due to 1) quenching - 50% of the SFRD in the field and 75% in clusters at z > 2 originated in galaxies that are passive today - and 2) the fact that the average SFR of today's star-forming galaxies has decreased with time. We quantify the contribution to the SFRD(z) of galaxies of today's different masses and morphologies. The current morphology correlates with the current star formation activity but is irrelevant for the past stellar history. The average SFH depends on galaxy mass, but galaxies of a given mass have different histories depending on their environment. We conclude that the variation of the SFRD(z) with environment is not driven by different distributions of galaxy masses and morphologies in clusters and field, and must be due to an accelerated formation in high mass haloes compared to low mass ones even for galaxies that will end up having the same galaxy mass today.

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arXiv2014

From blue star-forming to red passive: galaxies in transition in different environments

Exploiting a mass complete (M_*>10^(10.25)M_sun) sample at 0.03<z<0.11 drawn from the Padova Millennium Galaxy Group Catalog (PM2GC), we use the (U-B)_rf color and morphologies to characterize galaxies, in particular those that show signs of an ongoing or recent transformation of their star formation activity and/or morphology - green galaxies, red passive late types, and blue star-forming early types. Color fractions depend on mass and only for M_*<10^(10.7)M_sun on environment. The incidence of red galaxies increases with increasing mass, and, for M_*<10^(10.7)M_sun, decreases toward the group outskirts and in binary and single galaxies. The relative abundance of green and blue galaxies is independent of environment, and increases monotonically with galaxy mass. We also inspect galaxy structural parameters, star-formation properties, histories and ages and propose an evolutionary scenario for the different subpopulations. Color transformations are due to a reduction and suppression of SFR in both bulges and disks which does not noticeably affect galaxy structure. Morphological transitions are linked to an enhanced bulge-to-disk ratio due to the removal of the disk, not to an increase of the bulge. Our modeling suggests that green colors might be due to star formation histories declining with long timescales, as an alternative scenario to the classical "quenching" processes. Our results suggest that galaxy transformations in star formation activity and morphology depend neither on environment nor on being a satellite or the most massive galaxy of a halo. The only environmental dependence we find is the higher fast quenching efficiency in groups giving origin to post-starburst signatures.

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arXiv2013

The impact of global environment on galaxy mass functions at low redshift

We study the galaxy stellar mass function in different environments in the local Universe, considering both the total mass function and that of individual galaxy morphological types. We compare the mass functions of galaxies with $\rm log_{10} M_{\star}/M_{\odot} \geq 10.25$ in the general field and in galaxy groups, binary and single galaxy systems from the Padova-Millennium Galaxy and Group Catalogue at $z=0.04-0.1$ with the mass function of galaxy clusters of the WIde-field Nearby Galaxy-Cluster Survey at $z=0.04-0.07$. Strikingly, the variations of the mass function with global environment, overall, are small and subtle. The shapes of the mass functions of the general field and clusters are indistinguishable, and only small, statistically insignificant variations are allowed in groups. Only the mass function of our single galaxies, representing the least massive haloes and comprising less than a third of the general field population, is proportionally richer in low-mass galaxies than other environments. The most notable environmental effect is a progressive change in the upper galaxy mass, with very massive galaxies found only in the most massive environments. This environment-dependent mass cut-off is unable to affect the Schechter parameters and the K-S test, and can only be revealed by an ad-hoc analysis. Finally, we show how, in each given environment, the mass function changes with morphological type, and that galaxies of the same morphological type can have different mass functions in different environments.

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arXiv2012

The evolution of galaxy sizes

We present a study of galaxy sizes in the local Universe as a function of galaxy environment, comparing clusters and the general field. Galaxies with radii and masses comparable to high-z massive and compact galaxies represent 4.4% of all galaxies more massive than 3 X 10^{10} M_sun in the field. Such galaxies are 3 times more frequent in clusters than in the field. Most of them are early-type galaxies with intermediate to old stellar populations. There is a trend of smaller radii for older luminosity-weighted ages at fixed galaxy mass. We show the relation between size and luminosity-weighted age for galaxies of different stellar masses and in different environments. We compare with high-z data to quantify the evolution of galaxy sizes. We find that, once the progenitor bias due to the relation between galaxy size and stellar age is removed, the average amount of size evolution of individual galaxies between high- and low-z is mild, of the order of a factor 1.6.

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arXiv2012

Superdense galaxies and the mass-size relation at low redshift

We search for massive and compact galaxies (superdense galaxies, hereafter SDGs) at z=0.03-0.11 in the Padova-Millennium Galaxy and Group Catalogue, a spectroscopically complete sample representative of the local Universe general field population. We find that compact galaxies with radii and mass densities comparable to high-z massive and passive galaxies represent 4.4% of all galaxies with stellar masses above 3 X 10^10 M_sun, yielding a number density of 4.3 X 10^-4 h^3 Mpc^-3. Most of them are S0s (70%) or ellipticals (23%), are red and have intermediate-to-old stellar populations, with a median luminosity-weighted age of 5.4 Gyr and a median mass-weighted age of 9.2 Gyr. Their velocity dispersions and dynamical masses are consistent with the small radii and high stellar mass estimates. Comparing with the WINGS sample of cluster galaxies at similar redshifts, the fraction of superdense galaxies is three times smaller in the field than in clusters, and cluster SDGs are on average 4 Gyr older than field SDGs. We confirm the existence of a universal trend of smaller radii for older luminosity-weighted ages at fixed galaxy mass. On top of the well known dependence of stellar age on galaxy mass, the luminosity-weighted age of galaxies depends on galaxy compactness at fixed mass, and, for a fixed mass and radius, on environment. This effect needs to be taken into account in order not to overestimate the evolution of galaxy sizes from high- to low-z. Our results and hierarchical simulations suggest that a significant fraction of the massive compact galaxies at high-z have evolved into compact galaxies in galaxy clusters today. When stellar age and environmental effects are taken into account, the average amount of size evolution of individual galaxies between high- and low-z is mild, a factor ~1.6. (abridged)

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arXiv2011

The importance of the local density in shaping the galaxy stellar mass functions

Exploiting the capabilities of four different surveys --- the Padova-Millennium Galaxy and Group Catalogue (PM2GC), the WIde-field Nearby Galaxy-cluster Survey (WINGS), the IMACS Cluster Building Survey (ICBS) and the ESO Distant Cluster Survey (EDisCS) --- we analyze the galaxy stellar mass distribution as a function of local density in mass-limited samples, in the field and in clusters from low (z>0.04) to high (z<0.8) redshift. We find that at all redshifts and in all environments, local density plays a role in shaping the mass distribution. In the field, it regulates the shape of the mass function at any mass above the mass limits. In clusters, it seems to be important only at low masses (log M_ast/M_sun <10.1 in WINGS and log M_ast/M_sun < 10.4 in EDisCS), otherwise it seems not to influence the mass distribution. Putting together our results with those of Calvi et al. and Vulcani et al. for the global environment, we argue that at least at $z\leq 0.8$ local density is more important than global environment in determining the galaxy stellar mass distribution, suggesting that galaxy properties are not much dependent of halo mass, but do depend on local scale processes.

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arXiv2011

The distribution of galaxy morphological types and the morphology-mass relation in different environments at low redshift

We use \sim 2000 galaxies belonging to different environments to show how the fractions of different galaxy morphological types vary with global environment and as function of galaxy stellar mass at low redshift. Considering mass limited galaxy samples with log10 M\star/M\bigodot>= 10.25, we find a smooth increase/decline in the fraction of Es-S0s/late type galaxies going from single galaxies, to binaries, to groups. Considering all environments, the fractional variation is more conspicuous for S0s and late-types than for ellipticals solely due to a sharp enhancement/dearth of S0s/late-types in clusters compared to other environments. The morphological distribution of galaxies in the mass range 10.25 < log10 M\star/M\bigodot < 11 is rather independent both of galaxy stellar mass and global environment, except in clusters. The morphologies of galaxies more massive than log10 M\star/M\bigodot = 11 are instead a function of both galaxy mass and global environment. The morphology-mass relation therefore changes with global environment, showing that galaxy stellar mass cannot be the only parameter driving the morphological distribution of galaxies. The morphology-mass relations for S0 and late-type galaxies in clusters are peculiar compared to other environments, and this strongly suggests that cluster-specific effects act on these two types of galaxies, and that a significant number of S0s in clusters has a different origin with respect to S0s in other environments.

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arXiv2011

The Padova-Millennium Galaxy and Group Catalogue (PM2GC): the group-finding method and the PM2GC catalogues of group, binary and single field galaxies

We present the construction and describe the properties of the Padova-Millennium Galaxy and Group Catalogue (PM2GC), a galaxy catalogue representative of the general field population in the local Universe. We characterize galaxy environments by identifying galaxy groups at 0.04<=z<=0.1 with a Friends-of-Friends (FoF) algorithm using a complete sample of 3210 galaxies brighter than MB = -18.7 taken from the Millennium Galaxy Catalogue (MGC, Liske et al. (2003)), a 38deg^2 photometric and spectroscopic equatorial survey. We identified 176 groups with at least three members, comprising in total 1057 galaxies and representing ~43 per cent of the general field population in that redshift range. The median redshift and velocity dispersion of our groups are 0.0823 and 192 km s^-1, respectively. 88 per cent of the groups have fewer than ten members, and 63 per cent have fewer than five members. Nongroup galaxies were subdivided into "inary" systems of two bright close companions, and "single" galaxies with no companion, in order to identify different environments useful for future scientific analysis. We performed a detailed comparison with the 2PIGG catalogue to validate the effectiveness of our method and the robustness of our results. Galaxy stellar masses are computed for all PM2GC galaxies, and found to be in good agreement with Sloan Digital Survey Data Release 7 (SDSS-DR7) mass estimates. The catalogues of PM2GC groups, group properties and galaxy properties in all environments are publicly available on theWorld Wide Web.

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