download report - Sapienza

More documents

Recommendations

Info

Scientific Report 2007-2009 Astronomy & Astrophysics of baryons Ω b , the density of dark energy Ω Λ ). The focus is now on the determination of the equation of state of dark energy, on the parameters of inflation, on neutrino masses, and in the forthcoming EUCLID satellite (ESA) to investigate dark matter: all these represent direct links between cosmology and fundamental physics (A16). Paolo de Bernardis <strong>Sapienza</strong> Università di Roma 147 Dipartimento di Fisica
Scientific Report 2007-2009 Astronomy & Astrophysics A1. Structure and Evolution of Galaxies This research is focused on the formation and evolution of spheroidal and largely-populated star systems, such as globular clusters and first-type elliptical galaxies, which cannot usually be ”resolved” into individual objects. For elliptical galaxies the issues concern the progressive metal enrichment (owing to stellar nucleosynthesis and supernovae explosions) and the spatial distribution of the stellar populations, that were being formed in time (with corresponding increasing metallicities). The topic is relevant to the population synthesis, which consists in computing the integrated brightness, spectrum and colours, and allows the comparison of models with observational data. Observations are obtained through rectangular slits or concentric circular apertures. They can produce projected (on the disk image of a galaxy) radial profiles of photometric and spectral indices. Information on the dynamical evolution of the stars in the various populations is not available in the literature at the levels needed to achieve an adequate comparison with observations, because of limits in the theoretical approach and difficulties in the numerical treatment. In order to reach a satisfactory spectro-photometric synthesis and compare the computed surface radial gradients with the observed profiles it is essential to account for the different galactic locations of the stars formed at different ages and with different metallicities and, hence, with differences in colours and spectra, Indeed, these data are produced by the cumulative contributions of all the stars of the galaxy located along the line of sight intersecting the disk at any specified projected radial distance. Angeletti and Giannone (2003, 2008, 2010a, 2010b) bypassed the lack of information on the stellar dynamics by modelling the spatial radial distribution of the galactic mass, as deduced from the observed surface brightness, and the stellar metallicity, as derived from the central progressive concentration of the star forming gas. The strategy consisted in relating the stellar metal abundances to the stellar binding energies and angular momenta, in the scheme of a dissipative contraction of the proto-galactic gas accompanied by the simultaneous formation of stars with the metal abundances equal to that of the ambient gas at the time of the star formation. The approach combined a set of different schemes, in particular the ”Concentration model” (CM) and the ”Best Accretion Model” (BAM) by Lynden-Bell (1975), and the ”Simple model” (SM) by Pagel and Patchett (1975). Models with a large set of choices for the free parameters (the exponent of the R 1/n law for the radial surface brightness, the concentration index c, the metal yield p , and the amount of the accreted mass M) have been computed. The results have been then compared with the observations of four spectroscopic indices (Mg 1 , Mg 2 , < F e >, Hβ) by Davies et al. (1993) and two photometric indices (B − R C ) and (U − R C ) by Peletier et al. (1990) for a sample of eleven galaxies. Figure 1: The distributions of the stellar metal abundances for the elliptical galaxy NGC 4278 from the CM+BAM (with n = 4, c = 0.70, p = 1.0Z sun, M = 3) along the lines of sight through the projected radii Re B , 0.5Re B , and 0.1Re B , from left to right (solid curves). The dashed curve gives the distribution within the circular aperture with projected radius 0.5Re B , and the lowest solid curve the distribution integrated on the whole galaxy. The numbers of the stars are normalized to 1. In the inset, the model radial profile of Mg 2 is compared to the observations (dots; those on the right of the cross are unaffected by the seeing). The radius R is in unit of the effective radius Re B = 32 ′′ .9 in the Johnson B band. The inset in Figure 1 shows how the observational data for index Mg 2 for the elliptical galaxy NGC 4278 are fitted by the model. In the figure the spatial (in the galaxy) radial distribution of the metal abundances Z is plotted for three surface radial distances, a circular aperture concentric to the galaxy image, and the whole galaxy. The best agreement of the models with the observational data of the studied galaxy sample indicates that the degrees of dissipation vary from moderate to large, the mean stellar metallicities range from the solar value to significantly oversolar values, the masses of the accreted matter can be relevant, the dispersions of velocities are isotropic in the majority of the selected galaxies, and their ages are not in disagreement with the age of 13 billion years. This is the age of the oldest globular clusters in our galaxy (estimated to be the lowest limit to the age of the Universe). References 1. L. Angeletti, et al., A.I.P. Conf.Proc. 1059, 103 (2008). Authors L. Angeletti, P. Giannone <strong>Sapienza</strong> Università di Roma 148 Dipartimento di Fisica
Page 2 and 3:
Sapienza Università di Roma Dipart
Page 4 and 5:
Scientific Report 2007-2009 Introdu
Page 6 and 7:
Page 8 and 9:
Page 10 and 11:
Scientific Report 2007-2009 Organiz
Page 12 and 13:
Page 14 and 15:
Page 16 and 17:
Page 18 and 19:
Page 20 and 21:
Scientific Report 2007-2009 Theoret
Page 22 and 23:
Page 24 and 25:
Page 26 and 27:
Page 28 and 29:
Page 30 and 31:
Page 32 and 33:
Page 34 and 35:
Page 36 and 37:
Page 38 and 39:
Page 40 and 41:
Page 42 and 43:
Page 44 and 45:
Page 46 and 47:
Page 48 and 49:
Scientific Report 2007-2009 Condens
Page 50 and 51:
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
Page 62 and 63:
Page 64 and 65:
Page 66 and 67:
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
Page 98 and 99: Scientific Report 2007-2009 Condens
Page 100 and 101: Scientific Report 2007-2009 Condens
Page 102 and 103: Scientific Report 2007-2009 Particl
Page 130 and 131: 2 2 2 Scientific Report 2007-2009 P
Page 144 and 145: Scientific Report 2007-2009 Astrono
Page 166 and 167: Scientific Report 2007-2009 Geophys
Page 172 and 173: Scientific Report 2007-2009 History
Page 174 and 175: Scientific Report 2007-2009 History
Page 176 and 177: Scientific Report 2007-2009 Laborat
Page 198 and 199:
Scientific Report 2007-2009 Laborat
Page 200 and 201:
Scientific Report 2007-2009 Laborat
Page 202 and 203:
Scientific Report 2007-2009 Grants
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Scientific Report 2007-2009 Dissemi
Page 212 and 213:
Page 214 and 215:
Page 216 and 217:
Page 218 and 219:
Page 220 and 221:
Page 222 and 223:
Page 224 and 225:
Page 226 and 227:
Page 228 and 229:
Page 230 and 231:
Page 232 and 233:
Page 234 and 235:
Page 236 and 237:
Page 238 and 239:
Page 240 and 241:
Page 242 and 243:
Page 244 and 245:
Page 246 and 247:
Page 248 and 249:
Page 250 and 251:
Page 252 and 253:
Page 254 and 255:
Page 256 and 257:
Page 258 and 259:
Page 260:
show all

download report - Sapienza

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?