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Galaxy spectra encode in their continuum and absorption/emission features a wealth of information on galaxy physics, mass assembly and chemical enrichment history. The 4MOST-StePS survey will collect high-quality spectra (with a median signal-to-noise ratio of about 30 Å–1, and resolution R ~ 5000) for a sample of about 3300 galaxies brighter than IAB = 20.5 within the RA-Dec-z footprint of the WAVES-Deep survey. These spectra will provide a precise empirical description of the evolutionary path of massive galaxies in the intermediate redshift range (0.3 < z < 0.7) between the LEGA-C and SDSS surveys. The locations of the galaxies within the cosmic web, unveiled by WAVES-Deep, will disclose the connection between galaxy properties and environment, down to the scales of galaxy pairs., Published in The Messenger vol. 190, pp. 22-24, March 2023.

WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges at $R\sim20\,000$. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for $\sim$3 million stars and detailed abundances for $\sim1.5$ million brighter field and open-cluster stars; (ii) survey $\sim0.4$ million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey $\sim400$ neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in $z1$ million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at $z>2$. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator., 41 pages, 27 figures, accepted for publication by MNRAS

Ultraluminous X-ray sources (ULXs) are end points of stellar evolution. They are mostly interpreted as binary systems with a massive donor. They are also the most probable progenitors for BH-BH, and even more, for BH-NS coalescence. Parameters of ULXs are not know and need to be better determined, in particular the link with the metallicity of the environment which has been invoked frequently but not proven strongly. We have tackled this problem by using a MUSE DEEP mosaic of the Cartwheel galaxy and applying a Monte Carlo code that jointly fits spectroscopy and photometry. We measure the metallicity of the emitting gas in the ring and at the positions of X-ray sources by constructing spatially resolved emission line ratio maps and BPT diagnostic maps. The Carthweel is the archetypal ring galaxy and the location and formation time of new stellar populations is easier to reconstruct than in more normal galaxies. It has the largest population of ULXs ever observed in a single galaxy (16 sources have been classified as ULXs in Chandra and XMM-Newton data). The Cartwheel galaxy is therefore the ideal laboratory to study the relation between Star Formation (SF Rates and SF History) and number of ULXs and also their final fate. We find that the age of the stellar population in the outer ring is consistent with being produced in the impact (≤300Myr) and that the metallicity is mostly sub-solar, even if solutions can be found with a solar metallicity that account for most observed properties. The findings for the Cartwheel will be a testbed for further modelisation of binary formation and evolution paths.

The formation of cosmic structure culminates with the assembly of galaxy clusters, a process quite different from cluster to cluster. We present the study of the structure and dynamics of the Lyra complex formed of the two clusters RXC J1825.3+3026 and CIZA J1824.1+3029, very recently studied using both X-ray and radio data. This is the first analysis based on kinematics of member galaxies. New spectroscopic data for 285 galaxies were acquired at the Italian Telescopio Nazionale Galileo and used in combination with PanSTARRS photometry. The result of our member selection is a sample of 198 galaxies. For RXCJ1825 and CIZAJ1824 we report the redshifts, z=0.0645 and z=0.0708, the first estimates of velocity dispersion, sigmav=995 and 700 km/s, and dynamical mass, M200=1.1E15 and 4E14 Msun. The past assembly of RXCJ1825 is traced by the two dominant galaxies, both aligned with the major axis of the galaxy distribution along the East-West direction, and by a minor North-East substructure. We also detect a quite peculiar high velocity field in the South-West region of the Lyra complex. This feature is likely related to a high velocity, very luminous galaxy, suggested to be the central galaxy of a group in interaction with RXCJ1825 by very recent studies based on X-ray and radio data. The redshift of the whole Lyra complex is z=0.067. Assuming that the redshift difference between RXCJ1825 and CIZAJ1824 is due to the relative kinematics, the projected distance between the cluster centers is 1.3 Mpc and the los velocity difference is 1750 km/s. A dynamical analysis of the system shows that the two clusters are likely to be gravitationally bound, in a pre-merger phase, with CIZAJ1824 in front of RXCJ1825 and going toward it. Our results corroborate a picture where the Lyra region is the place of a very complex scenario of cluster assembly., A&A accepted, 17 pages, 17 figures, minor revision

Context. The upcoming new generation of optical spectrographs on four-meter-class telescopes, with their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage, will provide invaluable information for reconstructing the history of star formation in individual galaxies up to redshifts of about 0.7. Aims. We aim at defining simple but robust and meaningful physical parameters that can be used to trace the coexistence of widely diverse stellar components: younger stellar populations superimposed on the bulk of older ones. Methods. We produced spectra of galaxies closely mimicking data from the forthcoming Stellar Populations at intermediate redshifts Survey (StePS), a survey that uses the WEAVE spectrograph on the William Herschel Telescope. First, we assessed our ability to reliably measure both ultraviolet and optical spectral indices in galaxies of different spectral types for typically expected signal-to-noise ratios. We then analyzed such mock spectra with a Bayesian approach, deriving the probability density function of r- and u-band light-weighted ages as well as of their difference. Results. We find that the ultraviolet indices significantly narrow the uncertainties in estimating the r- and u-band light-weighted ages and their difference in individual galaxies. These diagnostics, robustly retrievable for large galaxy samples even when observed at moderate signal-to-noise ratios, allow us to identify secondary episodes of star formation up to an age of ∼0.1 Gyr for stellar populations older than ∼1.5 Gyr, pushing up to an age of ∼1 Gyr for stellar populations older than ∼5 Gyr. Conclusions. The difference between r-band and u-band light-weighted ages is shown to be a powerful diagnostic to characterize and constrain extended star-formation histories and the presence of young stellar populations on top of older ones. This parameter can be used to explore the interplay between different galaxy star-formation histories and physical parameters such as galaxy mass, size, morphology, and environment.© ESO 2019., L. C. wish to acknowledge financial support from Premiale 2015 MITiC, program 1.05.06.10 and Comunidad de Madrid under Atraccion de Talento grant 2018-T2/TIC-11612. A. I., S. Z., M. L., A. G., A. M., and C. T. acknowledge the financial support from the INAF PRIN-SKA 2017 program 1.05.01.88.04.ESKAPE-HI. I. L. acknowledges financial support from INAF-WEAVE funds, program 1.05.03.04.05. R. G. B. acknowledges support from the Spanish Ministry of Economy and Competitiveness through grant 205 AYA2016-77846-P and the State Agency for Research of the Spanish MCIU through the >Center of Excellence Severo Ochoa> award to 2017 the Instituto de Astrofisica de Andalucia (SEV-2017-0709). A. F. M. has received financial support through the Postdoctoral Junior Leader Fellowship Programme from >La Caixa> Banking Foundation (LCF/BQ/LI18/11630007). B. V. acknowledges the financial support from INAF Main Stream 2018 (P. I.: B. Vulcani).

We analyse publicly available, individual spectra of four, massive ($M>10^{11}M_{\odot}$) early-type galaxies with redshifts in the range 1.4 < z < 2 to determine their stellar content, extending our previous work up to z~2. The wide wavelength range of the VLT/X-Shooter spectroscopic data in the UV-Optical-NIR arms along with the availability of spectro-photometry allows us to explore different techniques to obtain the stellar population properties, namely through age/metallicity sensitive spectral indices, full spectral fitting and broad-band photometric fitting. Moreover, together with the widely used optical Lick indices we consider further indices in the UV rest-frame, and demonstrate that UV indices significantly help the accuracy of the resulting population parameters. We find galaxy ages ranging from 0.2 to 4 Gyr, where the oldest galaxy is found at the lowest redshift, with an excellent agreement between ages determined via indices, full spectral fitting or broad-band colours. These ages are in perfect agreement with ages of local galaxies at the same velocity dispersion when we assume pure passive evolution. Total metallicities derived from indices show some scatter (between less than half-solar to very high values, ([Z/H]~0.6]). We speculate on possible mechanisms explaining these values, but given the sample size and low S/N of the spectra no conclusion can be made. Indices in the UV-rest frame generally lead to similar conclusions as optical indices. For the oldest galaxy (4 Gyr) we show that its UV-indices can only be explained by stellar population models including a UV contribution from old stellar populations, suggesting that old, UV bright populations start to inhabit mature galaxies of a few Gyr of age. This is the highest redshift (z~1.4) detection of the UV-upturn up to date., 23 pages, Accepted for publication in MNRAS

We present F850LP-F160W color gradients for 11 early-type galaxies (ETGs) at 1.0 R_e we have found that the fraction of high-z ETGs with negative F850LP-F160W color gradients rises up to 100%. For each galaxy, we investigate the origin of the radial color variation with a technique based on the matching of both the spatially resolved color and the global spectral energy distribution (SED) to predictions of composite stellar population models. In fact, we find that the age of the stellar populations is the only parameter whose radial variation alone can fully account for the observed color gradients and global SEDs for half of the galaxies in our sample (6 ETGs), without the need of radial variation of any other stellar population property. For four out of these six ETGs, a pure metallicity variation can also reproduce the detected color gradients. Nonetheless, a minor contribution to the observed color gradients from radial variation of star-formation time scale, abundance of low-to-high mass stars and dust cannot be completely ruled out. For the remaining half of the sample, our analysis suggests a more complex scenario whereby more properties of the stellar populations need to simultaneously vary to generate the observed color gradients and global SED. Our results show that, despite the young mean age of our galaxies (

[Abridged] In this paper we derive the central stellar mass density within a fixed radius and the effective stellar mass density within the effective radius for a complete sample of 34 ETGs morphologically selected at 0.9 2. Also, we show that the small scatter of the central mass density of ETGs compared to the large scatter of the effective mass density is simply a peculiar feature of the Sersic profile hence, independent of redshift and of any assembly history experienced by galaxies. Thus, it has no connection with the possible inside-out growth of ETGs. Finally, we find a tight correlation between the central stellar mass density and the total stellar mass of ETGs in the sense that the central mass density increases with mass as M^{~0.6}. This implies that the fraction of the central stellar mass of ETGs decreases with the mass of the galaxy. These correlations are valid for the whole population of ETGs considered independently of their redshift suggesting that they originate in the early-phases of their formation.

We present a study based on a sample of 62 early-type galaxies (ETGs) at 0.9 5. Earlier stars, those formed at zform > 5, are assembled in compact and more massive ( M⊙) ETGs, while stars formed later (zform≲ 3) or resulting from subsequent episodes of star formation are assembled both in compact and in normal ETGs. Thus, the older the stellar population, the higher the mass of the hosting galaxy but not vice versa. This suggests that the epoch of formation may play a role in the formation of massive ETGs rather than the mass itself. We show that the possible general scheme in which normal ETGs at 〈z〉≃ 1.5 are descendants of compact spheroids assembled at higher redshift is not compatible with the current models. Indeed, we find that the number of dry mergers expected in a hierarchical model is almost two orders of magnitude lower than that needed to enlarge a compact ETG up to a normal-size ETG. Moreover, we do not find evidence supporting a dependence of the compactness of galaxies on their redshift of assembly, a dependence expected in the hypothesis that the compactness of a galaxy is due to the higher density of the Universe at earlier epochs. Finally, we propose a simple scheme of formation and assembly of the stellar mass of ETGs based on dissipative gas-rich merger, which can qualitatively account for the coexistence of normal and compact ETGs observed at 〈z〉≃ 1.5 in spite of the same stellar mass, the lack of normal ETGs with high zform and the absence of correlation between compactness, stellar mass and formation redshift.

We have derived colour gradients for a sample of 20 early-type galaxies (ETGs) at 1 < z_spec < 2 selected from the GOODS-South field. The sample includes both normal ETGs (13) having effective radii comparable to the mean radius of local ones and compact ETGs (7) having effective radii from two to six times smaller. Colour gradients have been derived in the F606W-F850LP bands (UV-U rest-frame) taking advantage of the ultradeep HST-ACS observations covering this field and providing a spatial resolution of about 0.8 kpc at the redshift of the galaxies. Despite of the narrow wavelength baseline covered (1000 Angstrom), sampling approximatively the emission dominated by the same stellar population, we detect significant radial colour variations in 50 per cent of our sample. In particular, we find five ETGs with positive colour gradients (cores bluer than the external regions), and five galaxies with negative colour gradients (cores redder than the external regions), as commonly observed in the local Universe. These results show that at 1 < z < 2, when the Universe was only 3-4 Gyr old, ETGs constituted a composite population of galaxies whose different assembly histories have generated different stellar distributions with the bluest stellar population either in the center or in the outskirts as well as throughout the whole galaxy. Moreover, we find that compact galaxies seem to preferentially show a blue cores while moving towards normal galaxies, central stellar populations become progressively redder. Nonetheless, the narrow baseline covered together with the low statistics still prevent us to be conclusive about a possible physical connection between colour gradients and the degree of compactness of high-z ETGs.

Many of the early-type galaxies observed so far at z>1 turned out to have smaller radii with respect to that of a typical present-day early-type galaxy with comparable mass. This has generated the conviction that in the past early-type galaxies were more compact, hence denser, and that as a consequence, they should have increased their radius across the time to reconcile with the present-day ones. However, observations have not yet established whether the population of early-types in the early Universe was fully represented by compact galaxies nor if they were so much more numerous than in the present-day Universe to require an evolution of their sizes. Here we report the results of a study based on a complete sample of 34 early-type galaxies at 0.9 ~1.5 suggests that their build-up taken place in the first 3-4 Gyr, followed distinct paths. Also, we find that the number density of compact early-types at ~1.5 is consistent with the lower limits of the local number density of compact early-types derived from local clusters of galaxies. The similar number of compact early-types found in the early and in the present day Universe frustrates the hypothesized effective radius evolution while provides evidence that also compact ETGs were as we see them today 9-10 Gyr ago. Finally, the fact that (at least) most of the compact ETGs at high-z are accounted for by compact early-types in local cluster of galaxies implies that the former are the direct progenitors of the compact early-type cluster galaxies establishing a direct link between environment and early phases of assembly of ETGs.

We present the first estimate of age, stellar metallicity and chemical abundance ratios, for an individual early-type galaxy at high-redshift (z = 1.426) in the COSMOS field. Our analysis is based on observations obtained with the X-Shooter instrument at the VLT, which cover the visual and near infrared spectrum at high (R >5000) spectral resolution. We measure the values of several spectral absorptions tracing chemical species, in particular Magnesium and Iron, besides determining the age-sensitive D4000 break. We compare the measured indices to stellar population models, finding good agreement. We find that our target is an old (t > 3 Gyr), high-metallicity ([Z/H] > 0.5) galaxy which formed its stars at z_{form} > 5 within a short time scale ~0.1 Gyr, as testified by the strong [��/Fe] ratio ( > 0.4), and has passively evolved in the first > 3-4 Gyr of its life. We have verified that this result is robust against the choice and number of fitted spectral features, and stellar population model. The result of an old age and high-metallicity has important implications for galaxy formation and evolution confirming an early and rapid formation of the most massive galaxies in the Universe., 8 pages, 7 figures, accepted for publication in MNRAS

This paper aims at understanding if the normalization of the stellar initial mass function (IMF) of massive early-type galaxies (ETGs) varies with cosmic time and/or with mean stellar mass density Sigma (M*/2\pi Re^2). For this purpose we collected a sample of 18 dense (Sigma>2500 M_sun/pc^2) ETGs at 1.2 = 1.4 follow the same IMF-sigma_e trend of typical local ETGs, but with a lower mass-normalization. Nonetheless, once the IMF-sigma_e trend we have found for high-z dense ETGs is compared with that of local ETGs with similar Sigma and sigma_e, they turn out to be consistent. The similarity between the IMF-sigma_e trends of dense high-z and low-z ETGs over 9 Gyr of evolution and their lower mass-normalization with respect to the mean value of local ETGs suggest that, independently on formation redshift, the physical conditions characterizing the formation of a dense spheroid lead to a mass spectrum of new formed stars with an higher ratio of high- to low-mass stars with respect to the IMF of normal local ETGs., Comment: 9 pages, 4 figures, accepted for pubblication in A&A, updated to match final journal version

We spectroscopically identified 7 massive evolved galaxies with magnitudes 17.8~1.5, a factor 1.5 lower than the density (8.4(+-1) x 10^{-5} Mpc^{-3}) of early-types with comparable masses at z=0. The incompleteness (30%) of our spectroscopic observations accounts for this discrepancy. Thus, our data do not support a decrease of the comoving density of early-type galaxies with masses comparable to the most massive ones in the local Universe up to z~1.7. This suggests that massive evolved galaxies do not play an important role in the evolution of the mass density outlined by recent surveys in this redshift range, evolution which instead has to be ascribed to the accretion of the stellar mass in late-type galaxies. Finally, the presence of such massive evolved galaxies at these redshifts suggests that the assembly of massive spheroids has taken place at z>2 supporting a high efficiency in the accretion of the stellar mass in massive halos in the early Universe., Comment: Accepted for publication in MNRAS Letters, 5 pages, 3 figures

[abr] We report the analysis of three galaxies selected in the Hubble Deep Field South at Ks 3. We have used population synthesis models to constrain their redshifts and their stellar masses. One galaxy is at redshift z_p~2.4 while the other two are at z_p~2.9-3.0. All three galaxies have already assembled a stellar mass of about 10^{11} M_sun at the observed redshift placing the possible merging event of their formation at z>3.5. The inferred mass weighted age of their stellar populations implies that the bulk of the stars formed at z_f>3.5. The resulting co-moving density of M_{stars}>10^{11} M_sun galaxies at ~2.7 is rho=1.2(+-0.7)x10^{-4} Mpc^{-3}, about a factor two higher than the predictions of hierarchical models. The comparison with the local density of galaxies implies that the three galaxies must have already formed most of their stellar mass and that they cannot follow an evolution significantly different from a passive aging.The comparison with the density of local L>L* early types (passively evolved galaxies) suggests that their co-moving density cannot decrease by more than a factor 2.5-3 from z=0 to z~3 and that up to 40% of the stellar mass content of bright (L>L*) local early type galaxies was already in place at z>2.5.

We present a spectroscopic analysis based on measurements of two mainly age-dependent spectrophotometric indices in the 4000A rest frame region, i.e. H+K(CaII) and Delta4000, for a sample of 15 early-type galaxies (ETGs) at 0.7 < z_{spec} < 1.1, morphologically selected in the GOODS-South field. Ages derived from the two different indices by means of the comparison with stellar population synthesis models, are not consistent with each other for at least nine galaxies (60 per cent of the sample), while for the remaining six galaxies, the ages derived from their global spectral energy distribution (SED) fitting are not consistent with those derived from the two indices. We then hypothesized that the stellar content of many galaxies is made of two stellar components with different ages. The double-component analysis, performed by taking into account both the index values and the observed SED, fully explains the observational data and improves the results of the standard one-component SED fitting in 9 out of the 15 objects, i.e. those for which the two indices point towards two different ages. In all of them, the bulk of the mass belongs to rather evolved stars, while a small mass fraction is many Gyr younger. In some cases, thanks to the sensitivity of the H+K(CaII) index, we find that the minor younger component reveals signs of recent star formation. The distribution of the ages of the younger stellar components appears uniformly in time and this suggests that small amounts of star formation could be common during the evolution of high-z ETGs. We argue the possibility that these new star formation episodes could be frequently triggered by internal causes due to the presence of small gas reservoir., 18 pages, 12 figures. Accepted for publication in MNRAS

The aim of our analysis is twofold. On the one hand we are interested in addressing whether a sample of ETGs morphologically selected differs from a sample of passive galaxies in terms of galaxy statistics. On the other hand we study how the relative abundance of galaxies, the number density and the stellar mass density for different morphological types change over the redshift range 0.6=10^(11) M_sol) galaxies, with the fraction of massive ETGs rising up to 40% and the fraction of massive LTGs decreasing down to 60%. Moreover, we find that the number density and the stellar mass density of the whole population of massive galaxies increase almost by a factor of ~10 between 0.63-4x10^(11) M_sol) both ETGs and LTGs do not increase since z~2.5, contrary to the lower mass galaxies. This suggests that the population of the most massive galaxies formed at z>2.5-3 and that the assembly of such high-mass galaxies is not effective at lower redshift., Comment: 15 pages, 14 figures. Published in A&A

[Abridged] We studied the size-surface brightness and the size-mass relations of a sample of 16 cluster elliptical galaxies in the mass range 10^{10}-2x10^{11} M_sun which were morphologically selected in the cluster RDCS J0848+4453 at z=1.27. Our aim is to assess whether they have completed their mass growth at their redshift or significant mass and/or size growth can or must take place until z=0 in order to understand whether elliptical galaxies of clusters follow the observed size evolution of passive galaxies. To compare our data with the local universe we considered the Kormendy relation derived from the early-type galaxies of a local Coma Cluster reference sample and the WINGS survey sample. The comparison with the local Kormendy relation shows that the luminosity evolution due to the aging of the stellar content already assembled at z=1.27 brings them on the local relation. Moreover, this stellar content places them on the size-mass relation of the local cluster ellipticals. These results imply that for a given mass, the stellar mass at z~1.3 is distributed within these ellipticals according to the same stellar mass profile of local ellipticals. We find that a pure size evolution, even mild, is ruled out for our galaxies since it would lead them away from both the Kormendy and the size-mass relation. If an evolution of the effective radius takes place, this must be compensated by an increase in the luminosity, hence of the stellar mass of the galaxies, to keep them on the local relations. We show that to follow the Kormendy relation, the stellar mass must increase as the effective radius. However, this mass growth is not sufficient to keep the galaxies on the size-mass relation for the same variation in effective radius. Thus, if we want to preserve the Kormendy relation, we fail to satisfy the size-mass relation and vice versa., Accepted for publication in A&A, updated to match final journal version

This paper is the first of a series (Longhetti et al. 1997a,b) dedicated to the study of the star formation history in early-type galaxies which show fine structures and/or signatures of interaction . It presents nuclear line–strength indices for a sample composed of 21 shell galaxies, from the the Malin & Carter (1983) southern survey, and 30 members of isolated interacting pairs, from the Reduzzi & Rampazzo (1995) catalogue, located in low density environments . The spectral range covers 3700 A 5700 A at 2.1 A FWHM resolution. We measure 16 red ( 4200 A) indices defined by the Lick Group. Measures have been transformed into the Lick-IDS "standard” system. The procedure has been tested on a set of 5 elliptical galaxies selected from the Gonzalez (1993) sample. We derive also three blue ( 4200) indices, namely Δ (4000 A) defined by by Hamilton (1985), H+K(CaII) and Hδ /FeI defined by Rose (1984, 1985). Blue indices are correlated to the age of the last starburst occurred in a galaxy (Leonardi & Rose 1996). The determination of these indices, the estimate of the measurement errors and the correction for the galaxies velocity dispersions are discussed in detail. In the Appendix A we present the indices for a set of hot stars ( K) which may be used for extending W92 fitting functions toward high temperatures.

We present a work aimed at quantifying the reliability and systematics affecting the mass estimates obtained by means of the best fitting technique applied to the photometric SEDs of early‐type galaxies at 1

[Abridged]We present the morphological analysis based on HST-NICMOS observations in the F160W filter of a sample of 32 early-type galaxies (ETGs) at 1, Comment: Accepted for publication in MNRAS; 16 pages, 10 figures 2 tables

We briefly describe the main features of the Brera Multi-Wavelet (BMW) survey of serendipitous X-ray clusters, based on the still unexploited ROSAT-HRI archival observations. Cluster candidates are selected from the general BMW catalogue of 20,000 sources based exclusively on their X-ray extension. Contrary to common wisdom, a clever selection of the HRI energy channels allows us to significantly reduce the background noise, thus greatly improving the ability to detect low surface-brightness sources as clusters. The resulting sample of ~250 candidates shows a very good sky coverage down to a flux \~3x10^-14 erg/s/cm^2 ([0.5-2.0] keV band), i.e comparable to existing PSPC-based deep survey, with a particularly interesting area of ~100 sq.deg. around fluxes ~10^-13 erg/s/cm^2, i.e. where highly-luminous, rare systems at z~0.6-1 can be detected. At the same time, the superior angular resolution of the instrument should avoid biases against intrinsically small systems, while easing the identification process (e.g. by spotting blends and AGN contaminants). While about 20% of the candidates are already identified with groups/clusters at z 0.5) bonafide cluster counterpart for ~80% of the targets.

A census of massive galaxies at redshift increasingly higher than $z\sim$1 may provide strong constraints on the history of mass assembly and of star formation. Here we report on the analysis of three galaxies selected in the Hubble Deep Field South on the basis of their unusually red near-IR color J-K$\ge$3. These objects result to be massive (M$_{star}\sim 10^{11}$M$_{\odot}$) galaxies at redshift 2.5$ 5) at 1$ $4) on the basis of which we identified 4 massive evolved galaxies at 1.5$

We present the preliminary results of an on-going near-IR low resolution spectroscopic follow-up of a complete sample of 30 bright (K' 1.

The optical rest-frame sizes of 10 of the most massive (~5x10^{11}h_{70}^{-2}M_sun) galaxies found in the near-infrared MUNICS survey at 1.2, Comment: 5 pages, 2 figures, 1 table, accepted for publication in MNRAS letters

We present the morphological analysis based on HST-NIC2 (0.075 arcsec/pixel) images in the F160W filter of a sample of 9 massive field (> 10^{11} M_\odot) galaxies spectroscopically classified as early-types at 1.2 within R_e of our galaxies and we compared them with those of early-types at lower redshifts. We find that the surface brightness of our galaxies should get fainter by 2.5 mag from z~1.5 to z~0 to match the surface brightness of the local ellipticals with comparable R_e, i.e. the local Kormendy relation. Luminosity evolution without morphological changes can only explain half of this effect, as the maximum dimming expected for an elliptical galaxy is ~1.6 mag in this redshift range. Thus, other parameters, possibly structural, may undergo evolution and play an important role in reconciling models and observations. Hypothesizing an evolution of the effective radius of galaxies we find that R_e should increase by a factor 1.5 from z~1.5 to z~0., Comment: Accepted for publication in MNRAS, 15 pages, 8 figures

We present the analysis of 10 massive early-type galaxies at $z\sim1.5$. They have been identified by means of a near-IR low resolution spectroscopic follow-up of a complete sample of 36 bright (K' $$ 5) selected from the Munich Near-IR ClusterSurvey (MUNICS; Drory et al. 2001). The low resolution near-IR spectra constrain their redshift at $1.2 2$ for all the galaxies and $z_{f} \geq 4$ for the oldest ones. The comparison of the 4000\AA break and of the overall spectral shape of the average spectrum of the 10 galaxies at $z\sim1.5$ with those of their local counterpartsconfirms that field massive early-type galaxies formed the bulk of their stellar mass at $2, Comment: 11 pages, 6 figures, accepted for publication in MNRAS

[Abridged] We present the rest-frame Js-band and Ks-band luminosity function of a sample of about 300 galaxies selected in the HDF-S at Ks0.8 suggests that a significant fraction of them increases their stellar mass at 13. Thus, our results suggest that the assembly of high-mass galaxies is spread over a large redshift range and that the increase of their stellar mass has been very efficient also at very high redshift at least for a fraction of them., Comment: 18 pages, 21 figures, Accepted for publication in MNRAS

With the aim of building a data-set of spectral properties of well studied early-type galaxies showing emission lines, we present intermediate resolution spectra of 50 galaxies in the nearby Universe. The sample, which covers several of the E and S0 morphological sub-classes, is biased toward objects that might be expected to have ongoing and recent star formation, at least in small amounts, because of the presence of the emission lines. The emission are expected to come from the combination of active galactic nuclei and star formation regions within the galaxies. Sample galaxies are located in environments corresponding to a broad range of local galaxy densities, although predominantly in low density environments. Our long-slit spectra cover the 3700 - 7250 A wavelength range with a spectral resolution of about 7.6 A at 5550 A. The specific aim of this paper, and our first step on the investigation, is to map the underlying galaxy stellar population by measuring, along the slit, positioned along the galaxy major axis, line--strength indices at several, homogeneous galacto-centric distances. For each object we extracted 7 luminosity weighted apertures corrected for the galaxy ellipticity and 4 gradients and we measured 25 line-strength indices. The paper introduces the sample, presents the observations, describes the data reduction procedures, the extraction of apertures and gradients, the determination and correction of the line--strength indices, the procedure adopted to transform them into the Lick-IDS System and the procedures adopted for the emission correction. We finally discuss the comparisons between our dataset and line-strength indices available in the literature., A&A accepted. Electronic tables will be available at the CDS when the printed version will appear

We present XMM-Newton data centered on one of the MUNICS Near Infrared Cluster Survey fields (S2F1) and we discuss the X-ray properties of the 6 X-ray emitting EROs found. For one of them we have already obtained the redshift using near-infrared spectroscopic data, while for the remaining 5 EROs the analysis is based on photometric redshifts. We find evidence for the presence of an X-ray obscured QSO in at least 5 out of the 6 X-ray emitting EROs. For these 5 objects we derive intrinsic (2-10 keV) luminosities in excess of 10^44 erg/s and intrinsic column densities higher than 10^22 cm^-2. These values have been obtained through a basic X-ray spectral analysis for the three brightest sources and through the analysis of the hardness ratios for the remaining two. All of these 5 X-ray emitting EROs appear extended in the optical/near-infrared bands indicating that the host galaxy emission dominates at these wavelengths. This suggests that the hosted AGNs are likely to be absorbed also in the optical/near-infrared bands: i.e. they are likely X-ray obscured possible type 2 QSOs. For the remaining ERO the presence of an AGN is suggested both by its high 0.5-2 keV luminosity (L(0.5-2 keV)~10^43 erg/s) and by its X-ray-to-optical flux ratio. In this case the quality of the present data prevents us from placing firm constraints on the AGN type hosted. Finally, the near-IR spectrum obtained for one of the 6 EROs classifies the host galaxy as an elliptical at z~1.7 with a stellar mass well in excess of 10^11 M_\odot. This result corroborates the possible link between the QSO activity and the formation of massive spheroids., Comment: Accepted for publication on A&A; 10 pages, 5 figures

We present the preliminary results of an on-going near-IR low resolution spectroscopic follow-up of a complete sample of 30 bright (K'1., Comment: 2 pages, 1 figure. To appear in the proceedings of the Venice conference "Multiwavelength Mapping of Galaxy Formation and Evolution"

In this paper we study the iron content of a sample of 22 nearby hot clusters observed with BeppoSAX. We find that the global iron mass of clusters is tightly related to the cluster luminosity and that the relatively loose correlation between the iron mass and the cluster temperature follows from the combination of the iron mass vs. luminosity and luminosity vs. temperature correlations. The iron mass is found to scale linearly with the intracluster gas mass, implying that the global iron abundance in clusters is roughly constant. This result suggests that enrichment mechanisms operate at a similar rate in all clusters. By employing population synthesis and chemical enrichment models, we show that the iron mass associated to the abundance excess which is always found in the centre of cool core clusters can be entirely produced by the brightest cluster galaxy (BCG), which is always found at the centre of cool core clusters. The iron mass associated to the excess, the optical magnitude of the BCG and the temperature of the cluster are found to correlate with one another suggesting a link between the properties of the BCG and the hosting cluster. These observational facts lends strength to current formation theories which envisage a strong connection between the formation of the giant BCG and its hosting cluster., 12 pages, tables and figures included. Accepted for publication in A&A

A census of massive galaxies at redshift increasingly higher than $z\sim$1 may provide strong constraints on the history of mass assembly and of star formation. Here we report on the analysis of three galaxies selected in the Hubble Deep Field South on the basis of their unusually red near-IR color J-K$\ge$3. These objects result to be massive (M$_{star}\sim 10^{11}$M$_{\odot}$) galaxies at redshift 2.5$5) at 1$$4) on the basis of which we identified 4 massive evolved galaxies at 1.5$, Comment: 2 pages, 1 figure. To appear in the proceedings of the Venice conference "Multiwavelength Mapping of Galaxy Formation and Evolution"

We present the results of TNG near-IR low resolution spectroscopy of two (S7F5-254 and S7F5-45) sources belonging to a complete sample of 15 EROs with K'5 selected from the MUNICS Survey. Both the spectra show a sharp drop in the continuum which can be ascribed only to the Balmer break. This places them at 1.23.5 and z_f>2 for the two EROs respectively., Comment: Accepted for publication on A&A; 7 pages, 5 figures

We have derived star formation rates (SFRs), gas-phase oxygen abundances and effective dust absorption optical depths for a sample of galaxies drawn from the Stromlo-APM redshift survey using the new Charlot and Longhetti (2001; CL01) models, which provide a physically consistent description of the effects of stars, gas and dust on the integrated spectra of galaxies. Our sample consists of 705 galaxies with measurements of the fluxes and equivalent widths of Halpha, [OII], and one or both of [NII] and [SII]. For a subset of the galaxies, 60 and 100 micron IRAS fluxes are available. We compare the star formation rates derived using the models with those derived using standard estimators based on the Halpha, the [OII] and the far-infrared luminosities of the galaxies. The CL01 SFR estimates agree well with those derived from the IRAS fluxes, but are typically a factor of ~3 higher than those derived from the Halpha or the [OII] fluxes, even after the usual mean attenuation correction of A_Halpha=1 mag is applied to the data. We show that the reason for this discrepancy is that the standard Halpha estimator neglects the absorption of ionizing photons by dust in HII regions and the contamination of Halpha emission by stellar absorption. We also use our sample to study variations in star formation and metallicity as a function of galaxy absolute bJ magnitude. For this sample, the star formation rate per unit bJ luminosity is independent of magnitude. The gas-phase oxygen abundance does increase with bJ luminosity, although the scatter in metallicity at fixed magnitude is large., Comment: 17 pages, 8 figures, accepted for publication in MNRAS

We present a new model for computing consistently the line and continuum emission from galaxies, based on a combination of recent population synthesis and photoionization codes. We use effective parameters to describe the HII regions and the diffuse gas ionized by single stellar generations in a galaxy [...]. We calibrate the nebular properties of our model using the observed [OIII]/Hbeta, [OII]/[OIII], [SII]/Halpha, and [NII]/[SII] ratios of a representative sample of nearby spiral and irregular, starburst, and HII galaxies. To compute whole (line plus continuum) spectral energy distributions, we include the absorption by dust in the neutral interstellar medium (ISM) using a recent simple prescription, which is consistent with observations of nearby starburst galaxies. Our model enables us to interpret quantitatively the observed optical spectra of galaxies in terms of stars, gas, and dust parameters. We find that the range of ionized-gas properties spanned by nearby galaxies implies factors of 3.5 and 14 variations in the Halpha and [OII] luminosities produced per unit star formation rate (SFR). When accounting for stellar Halpha absorption and absorption by dust in the neutral ISM, the actual uncertainties in SFR estimates based on the emergent Halpha and [OII] luminosities are as high as several decades. We derive new estimators of the SFR, the gas-phase oxygen abundance, and the effective absorption optical depth of the dust in galaxies. We show that, with the help of other lines such as [OII], Hbeta, [OIII], [NII], or [SII], the uncertainties in SFR estimates based on Halpha can be reduced to a factor of only 2-3, even if the Halpha line is blended with the adjacent [NII] lines. Without Halpha, however, the SFR is difficult to estimate from the [OII], Hbeta, and [OIII] lines. (abridged), To appear in MNRAS; 17 pages with 10 embedded PS figures (mn.sty)

The present paper is a companion of two others dedicated one to the measurement of the line–strength indices (Longhetti et al. 1997a) and the second to trace back the star formation history of a sample of early–type galaxies by comparing observed indices to the predictions of new spectro–photometric models (Longhetti et al. 1997b). The sample of 51 early-type galaxies in low density environments is composed of two sub-sets of galaxies: 21 shell galaxies from the Malin & Carter (1983) catalogue (one of which shows double nucleous and has been considered as two separate objects) and 30 members of isolated interacting pairs from the Reduzzi & Rampazzo (1995) catalogue. Most of the objects show fine structures. The paper collects nuclear kinematic data together with the velocity and velocity dispersion curves of the stellar and gaseous components as a function of the distance from the galaxies centres. The galaxies heliocentric systemic velocity compares within km s-1 with RC3 data, while their central velocity dispersion compares within km s-1 , km s-1 and km s-1 with Gonzalez (1993), Davies et al. (1987) and Carter et al. (1988) respectively. The detailed comparison between our velocity and velocity dispersion curves and those from several authors is discussed. 9 out of 22 shell galaxies nuclei show emission lines, 4 of which, using data in the literature, have line ratios characteristic of LINERs. 10 members of pairs out of 30 show emission lines. RR 331a has a Seyfert like nucleus, while for the remaining galaxies the ([O III] λ 5007)/Hβ ratio is characteristic of low ionization regions. In a small fraction of the objects the emission component is detectable outside the central value. None of the objects in the sample shows counter-rotation of the gaseous versus the stellar component. The two components appear associated, although, in two cases there is evidence that gas and stars lie on different planes. This latter phenomenon could be associated to accretion events. Emission lines in the central part of the RR 331a show a secondary component in the emission lines profile. E 2400100 has two nuclei embedded in the main body of the galaxy. The U-shape profile of the stellar velocity profile shows the ongoing interaction of the two nuclei. profile of shell galaxies is, finally, discussed in relation to the hypothesis of the accretion/merging origin of these galaxies.

We studied the scaling properties of a sample of 65 ETGs at 1 < z < 2 with spectroscopic confirmation of their redshift and spectral type. The sample collects proprietary (Longhetti et al. 2007) and archival HST data and it is composed of 30 ETGs with HST-NICMOS observations (see Saracco et al. 2009) and of 35 ETGs from the GOODS-South field covered by HST-ACS observations. The whole sample is covered also by ground-based optical and near-IR observations while complementary mid-IR data (Spitzer or AKARI) are available for 45 galaxies. The study of the Kormendy, the size-luminosity and the size-mass relations of these ETGs shows that a large fraction (~50%) of them follows the local relations. These ’normal’ ETGs are not smaller (denser) than their local counterparts with comparable stellar mass, luminosity and surface brightness and no size evolution is required for them. On the contrary, the remaining half of the sample is composed of very compact ETGs with sizes (densities) 2.5-3 (15-30) times smaller (higher) than the other ETGs and than local ETGs. Thus, not all the high-z ETGs are superdense and, consequently, only some of them must experience size evolution showing that the evolutionary path of ETGs at 0 < z < 2 is not univocal. We also find that the stellar population of normal ETGs formed at 1.5 < zform < 3 while it formed at 2 < zform < 9 in compact ETGs. This suggests that different histories of mass assembly must take place at high-z to produce both the normal and the superdense ETGs seen at 1 < z < 2 (Saracco et al. 2010).

A near-IR low-resolution spectroscopic follow-up of a complete sample of K1.2 and at estimating their spatial density to put constraints on the galaxy formation and evolution models. In this proceeding, the preliminary analysis of the first spectra obtained is presented., For the proceedings of the meeting "Galaxy Evolution: Theory and Observations", (Cozumel, April 2002), to be edited by V. Avila-Reese, C. Firmani, C. Frenk, & C. Allen, RevMexAA SC (2002)

We analyze the star formation properties of a sample of 21 shell galaxies and 30 early-type galaxies members of interacting pairs, located in low density environments (Longhetti et al 1998a, 1998b). The study is based on new models developed to interpret the information coming from `blue' H$\delta$/FeI, H+K(CaII) and \D4000 line-strength indices proposed by Rose (1984; 1985) and Hamilton (1985). We find that the last star forming event that occurred in the nuclear region of shell galaxies is statistically old (from 0.1 up to several Gyr) with respect to the corresponding one in the sub-sample of pair galaxies (, Comment: 12 pages, including 7 figures - Accepted for publication in A&A

In this paper we analyze the line-strength indices in the Lick-system measured by Longhetti et al. (1998a, b) for a sample of 51 early-type galaxies located in low density environments (LDE) and showing signatures of fine structures and/or interactions. The sample contains 21 shell-galaxies and 30 members of interacting pairs. Firstly we perform a preliminary comparison between three different sources of calibrations of the line strength indices, namely Buzzoni et al. (1992, 1994), Worthey (1992), Worthey et al. (1994) and Idiart et al. (1995), derived from stars with different effective temperature, gravity, and metallicity. Secondly, we discuss the properties of the galaxies in our sample by comparing them both with theoretical Single Stellar Populations (SSPs) and the {\sl normal} galaxies of the Gonz\'alez (1993: G93) sample. The analysis is performed by means of several diagnostic planes. In the H$\beta$ vs. [MgFe] plane, which is perhaps best suited to infer the age of the stellar populations, the peculiar galaxies in our sample show nearly the same distribution of the {\sl normal} galaxies in the G93 sample. There is however a number of peculiar galaxies with much stronger H$\beta$. Does this mean that the scatter in the H$\beta$ vs. [MgFe] plane, of normal, shell- and pair-galaxies has a common origin, perhaps a secondary episode of star formation? We suggest that, owing to their apparent {\sl youth}, shell- and pair-galaxies should have experienced at least one interaction event after their formation. The explanation comes natural for shell- and pair-galaxies where the signatures of interactions are evident. It is more intrigued in {\sl normal} galaxies (perhaps other causes may concur)., Comment: 14 pages, 5 figures, accepted for publication in A&A

We are carrying on a near-IR very low resolution spectroscopic follow-up in parallel with XMM-Newton observations of a complete sample of ~30 bright (K', 2 pages, "Multiwavelength Cosmology" Mykonos, June 2003, conference proceedings

Here we present the results obtained from the analysis of 75 ksec of XMM-Newton observations of a sample of EROs selected from one MUNICS field (K', 2 pages, 1 figure. To appear in the proceedings of the Venice conference "Multiwavelength Mapping of Galaxy Formation and Evolution"

We briefly describe the main features of the Brera Multi-Wavelet (BMW) survey of serendipitous X-ray clusters, based on the still unexploited ROSAT-HRI archival observations. Cluster candidates are selected from the general BMW catalogue of 20,000 sources based exclusively on their X-ray extension. Contrary to common wisdom, a clever selection of the HRI energy channels allows us to significantly reduce the background noise, thus greatly improving the ability to detect low surface-brightness sources as clusters. The resulting sample of ~250 candidates shows a very good sky coverage down to a flux \~3x10^-14 erg/s/cm^2 ([0.5-2.0] keV band), i.e comparable to existing PSPC-based deep survey, with a particularly interesting area of ~100 sq.deg. around fluxes ~10^-13 erg/s/cm^2, i.e. where highly-luminous, rare systems at z~0.6-1 can be detected. At the same time, the superior angular resolution of the instrument should avoid biases against intrinsically small systems, while easing the identification process (e.g. by spotting blends and AGN contaminants). While about 20% of the candidates are already identified with groups/clusters at z0.5) bonafide cluster counterpart for ~80% of the targets., 3 pages, 2 figures; to appear in Proc. of the ESO/ECF/STSCI workshop on "Deep Fields", Garching Oct 2000, (Publ: Springer)