Global Properties of the Rich Cluster ABCG 209 at z~0.2. Spectroscopic and Photometric Catalogue

This paper is aimed at giving an overview of the global properties of the rich cluster of galaxies ABCG 209. This is achieved by complementing the already available data with new medium resolution spectroscopy and NIR photometry which allow us to i) analyse in detail the cluster dynamics, distinguishing among galaxies belonging to different substructures and deriving their individual velocity distributions, using a total sample of 148 galaxies in the cluster region, of which 134 belonging to the cluster; ii) derive the cluster NIR luminosity function; iii) study the Kormendy relation and the photometric plane of cluster early-type galaxies (ETGs). Finally we provide an extensive photometric (optical and NIR) and spectroscopic dataset for such a complex system to be used in further analyses investigating the nature, formation and evolution of rich clusters of galaxies. The observational scenario confirms that ABCG 209 is presently undergoing strong dynamical evolution with the merging of two or more subclumps. This interpretation is also supported by the detection of a radio halo (Giovannini et al. 2006) suggesting that there is a recent or ongoing merging. Cluster ETGs follow a Kormendy relation whose slope is consistent with previous studies both at optical and NIR wavelengths. We investigate the origin of the intrinsic scatter of the photometric plane due to trends of stellar populations, using line indices as indicators of age, metallicity and alpha/Fe enhancement. We find that the chemical evolution of galaxies could be responsible for the intrinsic dispersion of the Photometric Plane.Comment: 39 pages, 17 figures, MNRAS in pres

SPIDER - IV. Optical and NIR color gradients in Early-type galaxies: New Insights into Correlations with Galaxy Properties

We present an analysis of stellar population gradients in 4,546 Early-Type Galaxies with photometry in $grizYHJK$ along with optical spectroscopy. A new approach is described which utilizes color information to constrain age and metallicity gradients. Defining an effective color gradient, $\nabla_{\star}$, which incorporates all of the available color indices, we investigate how $\nabla_{\star}$ varies with galaxy mass proxies, i.e. velocity dispersion, stellar (M_star) and dynamical (M_dyn) masses, as well as age, metallicity, and alpha/Fe. ETGs with M_dyn larger than 8.5 x 10^10, M_odot have increasing age gradients and decreasing metallicity gradients wrt mass, metallicity, and enhancement. We find that velocity dispersion and alpha/Fe are the main drivers of these correlations. ETGs with 2.5 x 10^10 M_odot =< M_dyn =< 8.5 x 10^10 M_odot, show no correlation of age, metallicity, and color gradients wrt mass, although color gradients still correlate with stellar population parameters, and these correlations are independent of each other. In both mass regimes, the striking anti-correlation between color gradient and alpha-enhancement is significant at \sim 4sigma, and results from the fact that metallicity gradient decreases with alpha/Fe. This anti-correlation may reflect the fact that star formation and metallicity enrichment are regulated by the interplay between the energy input from supernovae, and the temperature and pressure of the hot X-ray gas in ETGs. For all mass ranges, positive age gradients are associated with old galaxies (>5-7 Gyr). For galaxies younger than \sim 5 Gyr, mostly at low-mass, the age gradient tends to be anti-correlated with the Age parameter, with more positive gradients at younger ages.Comment: Accepted for Publication in the Astronomical Journa

New insights into the structure of early-type galaxies: the Photometric Plane at z~0.3

We study the Photometric Plane (PHP), namely the relation between the effective radius re, the mean surface brightness within that radius e, and the Sersic index n, in optical (R and I) and near-infrared (K) bands for a large sample of early-type galaxies (ETGs) in the rich cluster MS1008-1224 at z=0.306. The PHP relation has an intrinsic dispersion of ~32% in re, and turns out to be independent of waveband. This result is consistent with the fact that internal colour gradients of ETGs can have only a mild dependence on galaxy luminosity (mass). There is no evidence for a significant curvature in the PHP. We show that this can be explained if this relation origins from a systematic variation of the specific entropy of ETGs along the galaxy sequence, as was suggested from previous works. The intrinsic scatter of the PHP is significantly smaller than for other purely photometric relations, such as the Kormendy relation and the photometric Fundamental Plane, which is constructed by using colours in place of velocity dispersions. The scatter does not depend on the waveband and the residuals about the plane do not correlate with residuals of the colour-magnitude relation. Finally, we compare the coefficients of the PHP at z~0.3 with those of ETGs at z~0, showing that the PHP is a valuable tool to constrain the luminosity evolution of ETGs with redshift. The slopes of the PHP do not change significantly with redshift, while the zero-point is consistent with cosmological dimming of the surface brightness in an expanding universe plus the passive fading of galaxy stellar populations with a high formation redshift (z_f >1-2).Comment: 21 pages, 10 figures, MNRAS in pres

Age, metallicity and star formation history of spheroidal galaxies in cluster at z~1.2

We present the analysis, based on spectra collected at the Large Binocular Telescope, of the stellar populations in seven spheroidal galaxies in the cluster XLSSJ0223 at $z$$\sim$1.22. The aim is to constrain the epoch of their formation and their star formation history. Using absorption line strenghts and full spectral fitting, we derive for the stellar populations of the seven spheroids a median age =2.4$\pm$0.6 Gyr, corresponding to a median formation redshift $\sim2.6_{-0.5}^{+0.7}$ (lookback time = 11$_{-1.0}^{+0.6}$ Gyr). We find a significant scatter in age, showing that massive spheroids, at least in our targeted cluster, are not coeval. The median metallicity is [Z/H]=0.09$\pm$0.16, as for early-types in clusters at 0$<z$<0.9. This lack of evolution of [Z/H] over the range 0$<$$z$$<$1.3, corresponding to the last 9 billions years, suggests that no significant additional star formation and chemical enrichment are required for cluster spheroids to reach the present-day population. We do not detect significant correlation between age and velocity dispersion$\sigma_e$, or dynamical mass M$_{dyn}$, or effective stellar mass density$\Sigma_e$. On the contrary, the metallicity [Z/H] of the seven spheroids is correlated to their dynamical mass M$_{dyn}$, according to a relation similar to the one for local spheroids. [Z/H] is also anticorrelated to stellar mass density$\Sigma_e$because of the anticorrelation between M$_{dyn}$and$\Sigma_e$. Therefore, the basic trends observed in the local universe were already established at$z\sim1.3$, i.e. more massive spheroids are more metal rich, have lower stellar mass density and tend to be older than lower-mass galaxies.Comment: 16 pages, 6 figures, 6 tables, published on MNRA

Probing galaxy evolution through the internal colour gradients, the Kormendy relations and the Photometric Plane of cluster galaxies at z~0.2

We present a detailed analysis of the photometric properties of galaxies in the cluster \A2163B at redshift z~0.2. R-, I- and K-band structural parameters, (half light radius r_e, mean surface brightness _e within r_e and Sersic index n) are derived for N~60 galaxies, and are used to study their internal colour gradients. For the first time, we use the slopes of optical-NIR Kormendy relations to study colour gradients as a function of galaxy size, and we derive the Photometric Plane at z~0.2 in the K band. Colour gradients are negligible at optical wavelengths, and are negative in the optical-NIR, implying a metallicity gradient in galaxies of ~0.2 dex per radial decade. The analysis of the Kormendy relation suggests that its slope increases from the optical to the NIR, implying that colour gradients do not vary or even do become less steep in more massive galaxies. Such a result is not simply accomodated within a monolithic collapse scenario, while it can be well understood within a hierarchical merging framework. Finally, we derive the first NIR Photometric Plane at z~0.2, accounting for both the correlations on the measurement uncertainties and the selection effects. The Photometric Plane at z~0.2 is consistent with that at z~0, with an intrinsic scatter significantly smaller than the Kormendy relation but larger than the Fundamental Plane.Comment: 18 pages, 12 figures, A&A in pres

Correggere e tradurre la poesia: il caso del Parisinus Suppl. Gr. 388

The present work focuses on the peculiarity of the codex Parisinus Suppl. Gr. 388. This manuscript is marked by a 12th-century Latin translation, running above some Greek verses of Theognis’ Elegies and entirely above the poems by Pseudo-Phocylides’ Sentences and by Dionysius Periegetes’ Description of the Known World. Moreover, the translator reviewed the Greek poems too. Hence, in this study I will focus on the correc- tion and translation of Theognis’ Elegies and Pseudo-Phocylides’ Sentences. Firstly, I will carry out a palaeographic analysis of the scholar’s writing. Secondly, I will scrutinize the Latin translation. Finally, I will analyse the corrections on Greek texts

Decreto onorario della città di Ilio per il re Antioco I

With this decree Ilion’s demos honours king Antiochus I because he made peace in the region disturbed by several rebellions and because of royal evergetism toward the city. The decree first presents Antiochus’ credits and then the manners by which Ilion honours him. The honour seems to be a royal cult: Ilion is ordered to pray gods (Athena and Apollon) for the king, to build a gold statue of him, finally to celebrate him during Panathenee. Even though nowadays it is sure that the decree was issued by Ilion and not by Sigeum, scholars still do not agree on the king’s identity: Antiochus I, as traditionally claimed, or Antiochus III. The question implies a new dating and a new interpretation of the historical events presented in the decree.With this decree Ilion’s demos honours king Antiochus I because he made peace in the region disturbed by several rebellions and because of royal evergetism toward the city. The decree first presents Antiochus’ credits and then the manners by which Ilion honours him. The honour seems to be a royal cult: Ilion is ordered to pray gods, especially Athena and Apollon, for the king; to build a gold statue of him; finally to celebrate him during Panathenee. Even though nowadays it is sure that the decree was issued by Ilion and not by Sigeum, scholars still do not agree on the king’s identity (Antiochus I, as traditionally claimed, or Antiochus III). The question implies a new dating and a new interpretation of the historical events presented in the decree

A geostatistical approach to multisensor rain field reconstruction and downscaling

International audienceA rain field reconstruction and downscaling methodology is presented, which allows suitable integration of large scale rainfall information and rain-gauge measurements at the ground. The former data set is assumed to provide probabilistic indicators that are used to infer the parameters of the probability density function of the stochastic rain process at each pixel site. Rain-gauge measurements are assumed as the ground truth and used to constrain the reconstructed rain field to the associated point values. Downscaling is performed by assuming the a posteriori estimates of the rain figures at each grid cell as the a priori large-scale conditioning values for reconstruction of the rain field at finer scale. The case study of an intense rain event recently observed in northern Italy is presented and results are discussed with reference to the modelling capabilities of the proposed methodology. Keywords: Reconstruction, downscaling, remote sensing, geostatistics, Meteosa

The Different Environmental Dependencies of Star-formation for Giant and Dwarf Galaxies

We examine the origins of the bimodality observed in the global properties of galaxies around a stellar mass of 3x10^10 M_sun by comparing the environmental dependencies of star-formation for the giant and dwarf galaxy populations. The Sloan Digital Sky Survey DR4 spectroscopic dataset is used to produce a sample of galaxies in the vicinity of the supercluster centered on the cluster A2199 at z=0.03 that is ~90% complete to a magnitude limit of M*+3.3. From these we measure global trends with environment for both giant (M_r<-20 mag) and dwarf (-19<M_r<-17.8 mag) subsamples using the luminosity-weighted mean stellar age and H_alpha emission as independent measures of star-formation history. The fraction of giant galaxies classed as old (t>7 Gyr) or passive (EW[H_alpha]<4 A) falls gradually from ~80% in the cluster cores to ~40% in field regions beyond 3-4 R_virial, as found in previous studies. In contrast, we find that the dwarf galaxy population shows a sharp transition at ~1 R_virial, from being predominantly old/passive within the cluster, to outside where virtually all galaxies are forming stars and old/passive galaxies are only found as satellites to more massive galaxies. These results imply fundamental differences in the evolution of giant and dwarf galaxies: whereas the star-formation histories of giant galaxies are determined primarily by their merger history, star-formation in dwarf galaxies is much more resilient to the effects of major mergers. Instead dwarf galaxies become passive only once they become satellites within a more massive halo, by losing their halo gas reservoir to the host halo, or through other environment-related processes such as galaxy harassment and/or ram-pressure stripping.Comment: 4 pages, 4 figures, accepted for publication in ApJ