arXiv subjects

Alessandro Pizzella

Publications and source records attributed to Alessandro Pizzella.

21 records · Page 2Linked to original sources

arXiv2013

The external origin of the polar gaseous disk of the S0 galaxy IC 5181

Galaxies accrete material from the environment through acquisition and merging events. We study the nearby S0 galaxy IC 5181 to address the origin of the ionized-gas component orbiting the galaxy on polar orbit ionized gas of IC 5181 from broad and narrow-band imaging. We measure the ionized-gas and stellar kinematics and the line strengths of the Lick indices of the stellar component along both the major and minor axis. The age, metallicity, and [alpha/Fe] enhancement of the stellar populations are derived using single stellar population models with variable element abundance ratios. The ionized-gas metallicity is obtained from the equivalent width of the emission lines. IC 5181 is a morphologically undisturbed S0 galaxy with a classical bulge made by old stars with super solar metallicity and overabundance. Stellar age and metallicity decrease in the disk region. The galaxy hosts a geometrically and kinematically decoupled component of ionized gas. It is elongated along the galaxy minor axis and in orthogonal rotation with respect to the galaxy disk. We interpret the kinematical decoupling as suggestive of a component of gas, which is not related to the stars and having an external origin. It was accreted by IC 5181 on polar orbits from the surrounding environment.

astro-ph.CO↗

arXiv2011

Dating the formation of the counter-rotating stellar disc in the spiral galaxy NGC 5719 by disentangling its stellar populations

We present the results of the VLT/VIMOS integral-field spectroscopic observations of the inner 28"x28" (3.1 kpc x 3.1 kpc) of the interacting spiral NGC 5719, which is known to host two co-spatial counter-rotating stellar discs. At each position in the field of view, the observed galaxy spectrum is decomposed into the contributions of the spectra of two stellar and one ionised-gas components. We measure the kinematics and the line strengths of the Lick indices of the two stellar counter-rotating components. We model the data of each stellar component with single stellar population models that account for the alpha/Fe overabundance. We also derive the distribution and kinematics of the ionised-gas disc, that is associated with the younger, less rich in metals, more alpha-enhanced, and less luminous stellar component. They are both counter-rotating with respect the main stellar body of the galaxy. These findings prove the scenario where gas was accreted first by NGC 5719 onto a retrograde orbit from the large reservoir available in its neighbourhoods as the result of the interaction with its companion NGC 5713, and subsequently fuelled the in situ formation of the counter-rotating stellar disc.

astro-ph.GA↗

arXiv2000

Kinematics and photometry as complementary tools in the study of barred galaxies

Recent advances in observational techniques and theoretical modelling of galaxy kinematics allow us to use more than just optical morphology to discern the structure and dynamics of galaxies. Here, we show for three barred galaxies (UGC 10205, NGC 6221 and NGC4340) that both kinematics and photometry are necessary to fully understand the properties of these galaxies. Kinematic and spectrophotometric data enable us to detect structures such as bars and gas shocks that are not directly visible in the images; conversely, imaging can be crucial for understanding the kinematic and dynamical behavior of a galaxy.

astro-ph↗