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| Paper: |
Models Constraints from Observations of Active Galaxies |
| Volume: |
497, Why Galaxies Care about AGB Stars III: A Closer Look in Space and Time |
| Page: |
459 |
| Authors: |
Riffel, R.; Pastoriza, M. G.; Rodríguez-Ardila, A.; Dametto, N. Z.; Ruschel-Dutra, D.; Riffel, R. A.; Storchi-Bergmann, T.; Martins, L. P.; Mason, R.; Ho, L. C.; Palomar XD team |
| Abstract: |
Studying the unresolved stellar content of galaxies generally involves
disentangling the various components contributing to the spectral
energy distribution (SED), and fitting a combination of simple stellar
populations (SSPs) to derive information about age, metallicity, and
star formation history. In the near-infrared (NIR, 0.85–2.5 μm),
the thermally pulsing asymptotic giant branch (TP-AGB) phase – the
last stage of the evolution of intermediate-mass
(M ≲ 6 M☉) stars – is a particularly important
component of the SSP models. These stars can dominate the
emission of stellar populations with ages ∼ 0.2–2 Gyr, being
responsible for roughly half of the luminosity in the K band. In
addition, when trying to describe the continuum observed in active
galactic nuclei, the signatures of the central engine and from the
dusty torus cannot be ignored. Over the past several years we have
developed a method to disentangle these three components. Our synthesis
shows significant differences between Seyfert 1 (Sy 1) and Seyfert 2
(Sy 2) galaxies.
The central few hundred parsecs of our galaxy sample contain a
substantial fraction of intermediate-age populations with a mean
metallicity near solar. Two-dimensional mapping of the near-infrared
stellar population of the nuclear region of active galaxies suggests
that there is a spatial correlation between the intermediate-age
stellar population and a partial ring of low stellar velocity dispersion
(σ*). Such an age is consistent with a scenario in which
the origin of the low-σ* rings is a past event which
triggered an inflow of gas and formed stars which still keep the colder
kinematics of the gas from which they have formed. We also discuss
the fingerprints of features attributed to TP-AGB stars in the
spectra of the nuclear regions of nearby galaxies. |
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