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Title: Galaxy evolution by chemical and SED model
Authors: Fan, Xi Long
Supervisore/Tutore: Matteucci, Maria Francesca
Cosupervisore: Silva, Laura
Issue Date: 26-Mar-2012
Publisher: Università degli studi di Trieste
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
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
− 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
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.
Ciclo di dottorato: XXIV Ciclo
metadata.dc.subject.classification: SCUOLA DI DOTTORATO DI RICERCA IN FISICA
Keywords: galaxy
Language: en
Type: Doctoral Thesis
Settore scientifico-disciplinare: FIS/05 ASTRONOMIA E ASTROFISICA
NBN: urn:nbn:it:units-9168
Appears in Collections:Scienze fisiche

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