The physical properties of Lyalpha emitting galaxies: not just primeval galaxies - AstrophysicsReport as inadecuate

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Abstract: We have analyzed a sample of LBGs from z =3.5 to z=6 selected from theGOODS-S field as B,V and i-dropouts, and with spectroscopic observationsshowing that they have the Lyalpha line in emission. Our main aim is toinvestigate their physical properties and their dependence on the emission linecharacteristics, to shed light on the relation between galaxies with Lyalphaemission and the general LBG population.The objects were selected from theircontinuum colors and then spectroscopically confirmed by the GOODScollaboration and other campaigns. From the spectra we derived the line fluxand EW. We then used U-band to mid-IR photometry from GOODS-MUSIC to derive thephysical properties of the galaxies, such as total stellar mass, age and so on,through standard SED fitting techniques.Although most galaxies are fit by youngstellar populations, a small but non negligible fraction has SEDs that requireconsiderably older stellar component, up to 1 Gyr. There is no apparentrelation between age and EW: some of the oldest galaxies have large EW, andshould be also selected in narrow band surveys. Therefore not all Lyalphaemitters are primeval galaxies in the very early stages of formation,as iscommonly assumed. We also find a large range of stellar populations, withmasses from 5x10^8 Msol to 5x10^10 Msol and SFR from few to 60 Msol-yr.Although there is no correlation between mass and EW, we find a significantlack of massive galaxies with high EW, which could be explained if the mostmassive galaxies were more dusty and-or contained more neutral gas than lessmassive objects. Finally we find that more than half of the galaxies containsmall but non negligible amounts of dust: the mean EB-V and the EW are wellcorrelated, although with a large scatter, as already found at lower redshift

Author: L.Pentericci, A. Grazian, A.Fontana, M. Castellano, E. Giallongo, S. Salimbeni, P. Santini


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