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Title: Galaxy evolution by chemical and SED model
Authors: Fan, Xi Long
Keywords: galaxydust
Issue Date: 26-Mar-2012
Publisher: Università degli studi di Trieste
Abstract: In this thesis, we have studied the ISM, QSO, LGRB hosts and LBGs by galactic chemical evolution and spectro-photometric models. We also tested the so-called mono- lithic scenario of elliptical galaxies formation. Here we present the main results of this work: 1. The star formation history is the main driver of galaxy evolution. The predictions of elliptical chemical evolution models with the so-called monolithic scenario of elliptical galaxies formation are consistent with the data of high redshift LBGs and QSOs. Both the infall and the star formation timescale are suggested to decrease with galactic mass. This scenario is confirmed by the spectro-photometric models by reproducing the average SED of MIPS-LBGs. This so-called “ downsizing” of SFH is consistent with many observations. 2. Our M = 1012M⊙ elliptical model can reproduce super-massive BH mass, stellar mass, gas mass and dust mass of one of the most distant QSO ever observed J1148+5251 (z ≃ 6.4). The same model can also reproduce [N/C] versus [C/H] and [Si/C] versus [C/H] of the NLRs in QSO hosts. The very high C abundance observed in these QSOs can be explained only by assuming yields with mass loss from massive stars with a strong dependence on metallicity, as those of Maeder (1992) 3. Our elliptical models suggested the LBGs at hight redshift are likely to be young (age < 0.6 Gyr) ellipticals. This picture is consist with the results of spectro- photometric models. By chemical evolution models, we found that, LBGs in A- MAZE and LSD samples, CB 58, Clone and Cosmic Horseshoe are of intermediate mass(1010 − 3 · 1010M⊙). Our elliptical model for 3 · 1010M⊙ well reproduces the [O/H] abundance as a function of redshift for these LBGs. By spectro-photometric models, we found that theMIPS-LBGs are more massive (∼ 1011M⊙). Our spectro- photometric models for 1011M⊙ well reproduce the average SED of MIPS-LBGs. 4. Our elliptical models suggested that if the observed high-redshift LGRB-DLAs and local LGRB host galaxies belonged to an evolutionary sequence, they should be irregulars with a common galaxy-formation redshift as high as zf = 10, observed at different phases of their evolution. We cannot exclude, however, that they correspond to the outermost regions of spiral disks, since their properties are similar to those of irregulars. Elliptical galaxies cannot be LGRB host galaxies at low 111 redshift and that they are very unlikely hosts of LGRB-DLAs even at high redshift, because of their rapid chemical enrichment at high redshift following the occurrence of a galactic wind several Gyrs ago and subsequent passive evolution. 5. Our elliptical models suggested that a dust mass-stellar mass relation exists, with more massive galaxies attaining a higher dust content at earlier time. The dust evolution in ISM make the main contribution for the large amount of dust in high redshift QSOs. QSO itself produced dust but this production appears negligible compared to that from stellar sources, unless one focuses on the very central regions at times very close to the galactic wind onset. 6. The dust mass estimation in the average MIPS-LBGs based on the combination of our elliptical models and spectro-photometric models is not consistent with the one based on simple temperature grey-body fitting. The Milky Way dust parameters can not reproduce the average SED of MIPS-LBGs with the SFHs from chemical evolution models. The more dense dusty environments and flatter dust size distributions are needed to reproduce the average SED of MIPS-LBGs with these SFHs. 7. IGIMF of starburst galaxies can improve the [α/Fe] ratios, however it still can- not solve the discrepancy between predictions and data. Dust effect is the most plausible solution.
Description: 2010/2011
NBN: urn:nbn:it:units-9168
Rights: An error occurred on the license name.
Appears in Collections:Scienze fisiche

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