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Search Results: 1 - 10 of 190087 matches for " G. Cristiani "
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Early-type Galaxies in the Hubble Deep Field. The -r_e relation and the lack of large galaxies at high redshift
G. Fasano,S. Cristiani,S. Arnouts,M. Filippi
Physics , 1998, DOI: 10.1086/300280
Abstract: We present the results of the detailed surface photometry of a sample of early-type galaxies in the Hubble Deep Field. Effective radii, surface brightnesses and total V_606 magnitudes have been obtained, as well as U_300, B_450, I_814, J, H and K colors, which are compared with the predictions of chemical-spectrophotometric models of population synthesis. Spectroscopic redshifts are available for 23 objects. For other 25 photometric redshifts are given. In the -r_e plane the early-type galaxies of the HDF, once the appropriate K+E corrections are applied, turn out to follow the `rest frame' Kormendy relation. This evidence, linked to the dynamical information gathered by Steidel et al.(1996), indicates that these galaxies, even at z~2-3, lie in the Fundamental Plane, in a virial equilibrium condition. At the same redshifts a statistically significant lack of large galaxies [i.e. with Log r_e(kpc) > 0.2] is observed.
The Fashion of Chinoiserie in the European Courts: Metastasio’s Le cinesi La moda delle cineserie nelle Corti Europee: Le cinesi di Metastasio
Chiara Cristiani
Between , 2011,
Abstract: This essay proposes an overview of the chinoiserie trend that exploded across Europe in the eighteenth century, influencing tastes in dress, painting, furniture, and theatre, with a particular reference to the European courts, among which the Court of Vienna held a place of absolute relevance. Le cinesi, a celebrative short play by Metastasio, official poet of the House of Haupsburg, is a libretto that shows how the trend affected the social life at the emperors’ parties, offering also an important document of how European aristocrats and literary men imagined the Chinese way of life, people and costumes, often not actually in relation to the truth of that world, which lay so far away from them. With a strict textual analysis, this paper demonstrates how, in the end, Metastasio paints a wonderful picture of an allegorical representation of dramatic genres, creating a mirror effect between the European spectators and the Chinese characters, via which the author outlines a connection that binds the audience to the stage and leads them to reflect not only on themselves, but also on issues of the theatre itself. Il presente saggio propone una panoramica della moda cosiddetta delle “Cineserie” che esplose in Europa nel corso del diciottesimo secolo, influenzando i gusti nel vestiario, nella pittura, nel mobilio e nel teatro, con particolare riferimento alle corti europee, tra cui la Corte di Vienna occupava un posto di assoluta rilevanza. Le cinesi, una festa teatrale di valore celebrativo ad opera di Metastasio, Poeta Cesareo della Casata d’Asburgo, è un libretto che mostra come la moda influenzò la vita mondana durante le feste dell’Imperatore, offrendo anche un importante documento di come gli aristocratici e i letterati europei dovevano immaginare lo stile di vita cinese, il popolo e i suoi costumi, spesso non realmente in relazione alla verità di quel mondo, tanto distante da loro. Attraverso una rigorosa analisi del testo, si dimostra come, infine, Metastasio dipinga una meravigliosa immagine di una rappresentazione allegorica riguardante i generi drammatici, creando un gioco di specchi tra gli spettatori europei e i personaggi cinesi, grazie al quale l’autore sottolinea una connessione che mette in relazione il pubblico con la scena, guidandolo verso una riflessione non solo su di sé, ma anche sulle istanze del teatro stesso.
Cosmological Adventures in the Lyman Forest
S. Cristiani
Physics , 1995,
Abstract: The properties of the Lyman-$\alpha$ absorptions observed in the spectra of QSOs are reviewed: the distribution of column densities and Doppler widths, the redshift evolution, the ``inverse effect'', the clustering. By interpreting the statistics of the line parameters insight is gained about the nature of the absorbers, their sizes, temperatures, confining agents. On the basis of the ``inverse effect'' it is possible to estimate the ultraviolet background radiation at high redshift and, linking this information with the limits on the Gunn-Peterson optical depth, the density of the diffuse part of the intergalactic medium is derived. Future prospects are briefly discussed.
Probing the Large Scale Structure with QSOs and radio-galaxies
S. Cristiani
Physics , 1998,
Abstract: QSOs and radio-galaxies, together with the CMB, ``normal'' galaxies and clusters, represent the main source of information about the origin and evolution of the Large Scale Structure. They can be used either directly, as tracers of the density peaks, or as cosmic lighthouses, probing the Universe along the line of sight with their conspicuous flow of photons. The amplitude of the QSO clustering has been measured to be $r_o \simeq 6 \hmpc$ at $z\sim 2$ and appears to increase with redshift. These properties are consistent with a scenario in which the quasars, with a lifetime of $t \sim 10^8 yr$, sparsely sample halos of mass greater than $M_{min} \sim 10^{12}-10^{13} h^{-1}$ M$_{\odot}$. Radio-galaxies are found to cluster on similar scales. The study of QSO and radio-galaxy environments is in qualitative agreement with their clustering properties. Absorption-line systems observed in high-resolution spectra of QSOs show structure, including voids/underdensities and overdensities, from the smallest scales to tens of Mpc. QSO pairs, groups and lenses allow us to get a 3-D glimpse of the absorbers, providing invaluable information about their size, ionization, mass. Great progress in this field is expected from the new instrumentation coming into operation at the 8-m class telescopes.
Clustering at High Redshift
S. Cristiani
Physics , 1999, DOI: 10.1007/10720961_24
Abstract: Together with the CMB, the three sources of information that astronomers have at high redshift as probes of the formation and evolution of the LSS are QSOs, galaxies and absorbers observed in the spectrum of distant background objects. In this contribution I try to give a hint of historical perspective, following how the technological advances have driven the emphasis from one class to another, in order to show what are the likely forthcoming milestones.
Blending Brownian motion and heat equation
Emiliano Cristiani
Physics , 2014,
Abstract: In this short communication we present an original way to couple the Brownian motion and the heat equation. More in general, we suggest a way for coupling the Langevin equation for a particle, which describes a single realization of its trajectory, with the associated Fokker-Planck equation, which instead describes the evolution of the particle's probability density function. Numerical results show that it is indeed possible to obtain a regularized Brownian motion and a Brownianized heat equation still preserving the global statistical properties of the solutions. The results also suggest that the more macroscale leads the dynamics the more one can reduce the microscopic degrees of freedom.
Early Results of the ESO VLT
S. Cristiani
Physics , 1999,
Abstract: The results of the FORS and ISAAC Science Verification of the FORS and ISAAC instruments at the VLT ANTU/UT1 are described. The following observations have been carried out: 1) the Cluster Deep Field MS1008.1-1224 2) the Antlia dwarf spheroidal Galaxy 3) multiple Object Spectroscopy of Lyman break galaxies in the AXAF and Hubble Deep Field South 4) ISAAC IR Spectroscopy of a gravitationally magnified galaxy at z=2.72. The data have been made public for the ESO community and, in the case of HDF-S, worldwide.
3D Printers: A new challenge for mathematical modeling
Emiliano Cristiani
Computer Science , 2014,
Abstract: This short communication aims at creating a bridge between 3D printing and advanced mathematical methods. We review some features of 3D printing in order to show how 3D printers' software can benefit from mathematical methods. To prove the feasibility of one possible PDE-based approach, we use a classical model for the Shape-from-Shading problem to create a 3D object starting from a single 2D photograph, and we 3D-print it!
The power spectrum of the flux distribution in the Lyman-alpha forest of a Large sample of UVES QSO Absorption Spectra (LUQAS)
T. -S. Kim,M. Viel,M. G. Haehnelt,R. F. Carswell,S. Cristiani
Physics , 2003, DOI: 10.1111/j.1365-2966.2004.07221.x
Abstract: The flux power spectra of the Lyman-alpha forest from a sample of 27 QSOs taken with the high resolution echelle spectrograph UVES on VLT are presented. We find a similar fluctuation amplitude at the peak of the ``3D'' flux power spectrum at k ~ 0.03 (km/sec)^(-1) as the study by Croft et al. (2002), in the same redshift range. The amplitude of the flux power spectrum increases with decreasing redshift if corrected for the increase in the mean flux level as expected if the evolution of the flux power spectrum is sensitive to the gravitational growth of matter density fluctuations. This is in agreement with the findings of McDonald et al. (2000) at larger redshift. The logarithmic slope of the "3D" flux power spectrum, P_F(k), at large scales k < 0.03 (km/sec)^(-1), is 1.4 +- 0.3, i.e. 0.3 shallower than that found by Croft et al. (2002) but consistent within the errors.
The Asiago-ESO/RASS QSO Survey II. The Southern Sample
A. Grazian,A. Omizzolo,C. Corbally,S. Cristiani,M. G. Haehnelt,E. Vanzella
Physics , 2002, DOI: 10.1086/343834
Abstract: This is the second paper of a series describing the Asiago-ESO/RASS QSO survey, a project aimed at the construction of an all-sky statistically well-defined sample of very bright QSOs (B_J < 15). Such a survey is required to remove the present uncertainties about the properties of the local QSO population and constitutes an homogeneous database for detailed evolutionary studies of AGN. We present here the complete Southern Sample, which comprises 243 bright (12.60 < B_J < 15.13) QSO candidates at high galactic latitudes (|b_{gal}| > 30^{\circ}). The area covered by the survey is 5660 sq. deg. Spectroscopy for the 137 still unidentified objects has been obtained. The total number of AGN turns out to be 111, 63 of which are new identifications. The properties of the selection are discussed. The completeness and the success rate for this survey at the final stage are 63% and 46%, respectively.
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