5 research outputs found
The fragility of thin discs in galaxies -- II. Thin discs as tracers of the assembly history of galaxies
Thin galactic discs and nuclear stellar discs (NSDs) are fragile structures
that can be easily disturbed by merger events. By studying the age of the
stellar populations in present-day discs, we can learn about the assembly
history of galaxies and place constraints on their past merger events.
Following on the steps of our initial work, we explore the fragility of such
disc structures in intermediate-mass-ratio dry encounters using the previously
constructed -body model of the Fornax galaxy NGC 1381 (FCC 170), which hosts
both a thin galactic disc and a NSD. We dismiss major and minor encounters, as
the former were previously shown to easily destroy thin-disc structures,
whereas the latter take several Hubble times to complete in the specific case
of FCC 170. The kinematics and structure of the thin galactic disc are
dramatically altered by the mergers, whereas the NSD shows a remarkable
resilience, exhibiting only a smooth increase of its size when compared to the
model evolved in isolation. Our results suggest that thin galactic discs are
better tracers for intermediate-mass-ratio mergers, while NSDs may be more
useful for major encounters. Based on our simulations and previous analysis of
the stellar populations, we concluded that FCC 170 has not experienced any
intermediate-mass-ratio dry encounters for at least 10 Gyr, as indicated
by the age of its thin-disc stellar populations.Comment: 11 pages, 10 figure
The fragility of thin discs in galaxies – II. Thin discs as tracers of the assembly history of galaxies
Thin galactic discs and nuclear stellar discs (NSDs) are fragile structures that can be easily disturbed by merger events. By studying the age of the stellar populations in present-day discs, we can learn about the assembly history of galaxies and place constraints on their past merger events. Following on the steps of our initial work, we explore the fragility of such disc structures in intermediate-mass-ratio dry encounters using the previously constructed N-body model of the Fornax galaxy NGC 1381 (FCC 170), which hosts both a thin galactic disc and an NSD. We dismiss major and minor encounters, as the former were previously shown to easily destroy thin-disc structures, whereas the latter take several Hubble times to complete in the specific case of FCC 170. The kinematics and structure of the thin galactic disc are dramatically altered by the mergers, whereas the NSD shows a remarkable resilience, exhibiting only a smooth increase of its size when compared to the model evolved in isolation. Our results suggest that thin galactic discs are better tracers for intermediate-mass-ratio mergers, while NSDs may be more useful for major encounters. Based on our simulations and previous analysis of the stellar populations, we concluded that FCC 170 has not experienced any intermediate-mass-ratio dry encounters for at least ∼10 Gyr, as indicated by the age of its thin-disc stellar populations
The fragility of thin discs in galaxies - I. Building tailored N-body galaxy models
International audienceThin stellar discs on both galactic and nuclear, sub-kpc scales are believed to be fragile structures that would be easily destroyed in major mergers. In turn, this makes the age-dating of their stellar populations a useful diagnostics for the assembly history of galaxies. We aim at carefully exploring the fragility of such stellar discs in intermediate- and low-mass encounters, using high-resolution N-body simulations of galaxy models with structural and kinematic properties tailored to actually observed galaxies. As a first but challenging step, we create a dynamical model of FCC 170, a nearly edge-on galaxy in the Fornax cluster with multiple galactic components and including both a galactic scale and nuclear stellar disc (NSD), using detailed kinematic data from the Multi Unit Spectroscopic Explorer and a novel method for constructing distribution function-based self-consistent galaxy models. We then create N-body realisations of this model and demonstrate that it remains in equilibrium and preserves its properties over many Gyr, when evolved with a sufficiently high particle number. However, the NSD is more prone to numerical heating, which gradually increases its thickness by up to 22 per cent in 10 Gyr even in our highest-resolution runs. Nevertheless, these N-body models can serve as realistic representations of actual galaxies in merger simulations
The fragility of thin discs in galaxies – I. Building tailored <i>N</i>-body galaxy models
Thin stellar discs on both galactic and nuclear, sub-kpc scales are believed to be fragile structures that would be easily destroyed in major mergers. In turn, this makes the age dating of their stellar populations a useful diagnostics for the assembly history of galaxies. We aim at carefully exploring the fragility of such stellar discs in intermediate- and low-mass encounters, using high-resolution N-body simulations of galaxy models with structural and kinematic properties tailored to actually observed galaxies. As a first but challenging step, we create a dynamical model of FCC 170, a nearly edge-on galaxy in the Fornax cluster with multiple galactic components and including both galactic-scale and nuclear stellar discs (NSDs), using detailed kinematic data from the Multi Unit Spectroscopic Explorer and a novel method for constructing distribution function-based self-consistent galaxy models. We then create N-body realizations of this model and demonstrate that it remains in equilibrium and preserves its properties over many Gyr, when evolved with a sufficiently high particle number. However, the NSD is more prone to numerical heating, which gradually increases its thickness by up to 22 per cent in 10 Gyr even in our highest resolution runs. Nevertheless, these N-body models can serve as realistic representations of actual galaxies in merger simulations
NGC 1436: the making of a lenticular galaxy in the Fornax cluster
We study the evolutionary path of the Fornax cluster galaxy NGC1436, which
is known to be currently transitioning from a spiral into a lenticular
morphology. This galaxy hosts an inner star-forming disc and an outer quiescent
disc, and we analyse data from the MeerKAT Fornax Survey, ALMA, and the
Fornax3D survey to study the interstellar medium and the stellar populations of
both disc components. Thanks to the combination of high resolution and
sensitivity of the MeerKAT data, we find that the
is entirely confined within the inner
star-forming disc, and that its kinematics is coincident with that of the CO.
The cold gas disc is now well settled, which suggests that the galaxy has not
been affected by any environmental interactions in the last Gyr. The
star formation history derived from the Fornax3D data shows that both the inner
and outer disc experienced a burst of star formation Gyr ago, followed
by rapid quenching in the outer disc and by slow quenching in the inner disc,
which continues forming stars to this day. We claim that NGC1436 has begun
to effectively interact with the cluster environment 5Gyr ago, when a
combination of gravitational and hydrodynamical interactions caused the
temporary enhancement of the star-formation rate. Furthermore, due to the
weaker gravitational binding was stripped
from the outer disc, causing its rapid quenching. At the same time, accretion
of gas onto the inner disc stopped, causing slow quenching in this region.Comment: Monthly Notices of the Royal Astronomical Society (MNRAS), accepted
for publication. Data available at the MeerKAT Fornax Survey website
https://sites.google.com/inaf.it/meerkatfornaxsurve