Tese
Formação estelar e emissão de poeira em núcleos ativos de galáxias
Fecha
2018-12-20Autor
Hennig, Moiré Gonçalves
Institución
Resumen
The energy coming from Active Nuclei of Galaxies (AGN) is attributed to the process of
accretion of matter to a central Supermassive Black Hole (SMBH). The gases that flow towards
the center of the galaxies (inflows of gas) can give rise to AGN but may also represent the
accumulation of matter in the central region necessary to trigger star formation on scales of
hundreds of parsecs. This work presents a study on the circumnuclear star formation for the
Seyfert 1 Mrk 42 galaxy and a characterization of the dust emission in the nucleus of a sample
of 15 Seyfert galaxies, in this way, relates intrinsic processes of AGN with properties of star
formation regions. We use near-infrared spectroscopy data (J, H and K-band), obtained with
the Near Infrared Integral Field Spectrograph (NIFS) installed on the Gemini North telescope.
The Mrk 42 galaxy shows a ring of star-forming regions around the nucleus with a radius of
≈300 pc, clearly observed in the flux distributions of the infrared emission lines. Two main
scenarios were proposed for the star formation rings in galaxies: the pop corn scenario, where
material arriving in the central region is accumulated in the ring and forms stellar clusters at
random positions without a sequence of ages and the pearls on the string scenario, for which
the gas accumulates in the ring forming regions of high densities and there is movement of
the star formation along the ring, observing a sequence of ages for the formed regions. Based
on measurements for the equivalent width of Br
we found evidence of age gradients for
the star formation regions along the ring of Mrk 42, favoring the pearls on a string scenario.
The full width at half maximum (FWHM) of the broad component of the Pa emission line
measured in the nuclear spectrum is ∼1 480 kms−1, implying a mass of ≈ 2, 5 × 106 M⊙ for
the central SMBH. Based on the ratios of emission lines we conclude that besides the active
galactic nucleus, Mrk 42 has stellar formation activity in the nucleus. The kinematics of the
gas are dominated by rotation in the plane of the galaxy, being well reproduced by a rotating
disk model. However, for the central region (internal to the ring) we observe an additional
component, probably originated by outflows of the AGN. In order to study the emission of
nuclear dust from Seyferts galaxies, we fitted the nuclear continuum to 15 Seyferts galaxies
from observations in the J and K bands. From the fits we obtain the contribution due to the
components of law of power and black body function, attributed to the emission of accretion
disk and the toroid of dust, respectively. We obtained values for the temperature ranging from
800 to 1 350 K and we derive masses of hot dust between 3,19×10−4 to 5,38×10−1 M⊙. There
is a small tendency to have a larger number of Seyfert 1 galaxies with higher values for the hot
dust than in Seyfert 2 galaxies. A correlation between the AGN bolometric luminosity and the
hot dust mass, indicating that the AGN is responsible for heating the dust. The sample used
to study the emission of dust is small and should be complemented in future works, as well as
a better comparison with results of the literature is necessary.