Integral Field Spectroscopy of (U) LIRGs and Post-Starburst QSOs: the role of mergers in galaxy evolution
Metadatos
Mostrar el registro completo del ítemAutor
Cortijo Ferrero, ClaraEditorial
Universidad de Granada
Director
González Delgado, Rosa MaríaDepartamento
Universidad de Granada. Programa Oficial de Doctorado en: Física y Ciencias del Espacio; Consejo Superior de Investigaciones Científicas (CSIC). Instituto de Astrofísica de AndalucíaMateria
Evolución Galaxias Espectroscopia Espacio Galaxias estallantes Astrofísica nuclear
Materia UDC
520.62 520.84 364.2 210104
Fecha
2016Fecha lectura
2015-12-02Referencia bibliográfica
Cortijo Ferrero, C. Integral Field Spectroscopy of (U) LIRGs and Post-Starburst QSOs: the role of mergers in galaxy evolution. Granada: Universidad de Granada, 2016. [http://hdl.handle.net/10481/41364]
Patrocinador
Tesis Univ. Granada. Programa Oficial de Doctorado en: Física y Ciencias del EspacioResumen
In this thesis we have characterized and compared the star formation histories, average stellar population
properties and ionized gas properties in two small samples of galaxies in different stages across the merger
sequence, three LIRGs (the two pre-mergers IC 1623 and NGC 6090 and the merger NGC 2623) and nine
PSQSOs, by analysing high quality Integral Field Spectroscopy (IFS) data in the rest-frame optical range
3700 - 7000 °A, and high resolution HST imaging. Additionally, for NGC 2623 we have narrow band imaging
in Hα and [NII]λ6583 from OSIRIS@GTC Tunable Filters, that allow us to study the outer parts of the
tidal tails. The results from the LIRGs and PSQSOs have been compared with control Sbc and Sc galaxies
from CALIFA survey. The methodology applied has been the same for all, a full spectral fitting analysis was
performed using the Starlight code with a combination of single stellar population (SSP) models from the
literature.
With our data we find a evolutionary sequence related to the merger progression that is in agreement
with recent simulations. In the initial stages (pre-mergers) the induced star formation (SF) is extended, and
enhanced, on average, by a factor ∼ 4 with respect to the control spirals. When we resolve it spatially we
find that for IC 1623 W the enhancement is the same in the central region and in the disk (by a factor 7),
while for NGC 6090 NE the enhancement is higher in the central region (by a factor 9), still significant at one
half light radius (by a factor 5) and less significant in the ”disk” (only enhanced by a factor 1.5). Attending
to the importance of stellar populations ∼ 300 Myr, we find that the merger-induced star formation started
earlier in IC 1623 W than in NGC 6090 NE.
In more advanced mergers, as NGC 2623, we find that most of the young SF is concentrated in the
central region, enhanced by a factor 9 with respect to control spirals. However, there exists also lower level of
star formation in the outer parts, enhanced by . 3 in comparison to spirals. From the global average across
the whole galaxy we find than is a factor ∼ 3 higher than in spirals. In addition, in NGC 2623 we detect
fossil emission of an extended merger-induced burst occurred ∼ 1.5 Gyr ago, probably when it was at the
pre-merger stage. The mass formed during this first burst is enhanced by a factor 2 both in the center and
in the outer parts with respect to the mass formed in the same period in isolated spirals.
From the average of the nine PSQSOs we find that, both in terms of light and mass, the SFHs are
comparable to NGC 2623 ones. Attending to the average ages we found that they are ∼ 400 Myr older than
NGC 2623. It seems that PSQSOs are slightly more evolved, however, given the uncertainties related to the
model base choice, and the heterogeneity of the sample, we can not confirm exactly to what degree. We
note, however, that both present a significant contribution to mass of stellar populations younger than 1.5
Gyr, which is not present in the pre-merger LIRGs. However, we think that the current starburst seen in
the pre-mergers is in fact forming this intermediate age mass that will look like NGC 2623 in . 1.5 Gyr.
The stellar mass in SSPs younger than 1.5 Gyr is ∼ 6.6 × 109 M⊙ (Chabrier IMF) in NGC 2623 and ∼ 1010
M⊙ in the PSQSOs, hence, we find that if the pre-merger LIRGs keep forming stars at the current rate ∼
16 M⊙ yr−1 during ∼ 400 - 600 Myr, then they can account for the mass in NGC 2623 and PSQSOs. This
time is approximately consistent with the 500 Myr upper limit expected for the duration of merger triggered
starbursts from numerical simulations of mergers.
With respect to the evolution from NGC 2623 to PSQSO, we note that in few 100 Myr molecular outflows
like the ones in some U/LIRGs would be able to remove dust from the core leaving the AGN uncovered. This
is in consistent with the average time delay of ∼ 400 Myr found by us between NGC 2623 and the PSQSOs.
Finally, given the stellar masses measured in the LIRGs and in the PSQSOs, most of them . 1011 M⊙,
we find that they will form ellipticals of intermediate mass (∼ 1011 M⊙), or the core of future giant ellipticals,
in agreement with the major-merger evolutionary scenario.