Chromodynamical analysis of lenticular galaxies using globular clusters and planetary nebulae

Abstract

Recovering the origins of lenticular galaxies can shed light on the understanding of galaxy formation and evolution, since they present properties that can be found in both elliptical and spiral galaxies. In this work we study the kinematics of the globular cluster (GC) systems of three lenticular galaxies located in low density environments (NGC 2768, NGC 3115 and NGC 7457), and compare them with the kinematics of planetary nebulae (PNe). The PNe and GC data come from the Planetary Nebulae Spectrograph and the SLUGGS Surveys. Through photometric spheroid-disc decomposition and PNe kinematics we find the probability for a given GC to belong to either the spheroid or the disc of its host galaxy or be rejected from the model. We find that there is no correlation between the components that the GCs are likely to belong to and their colours. Particularly, for NGC 2768 we find that its red GCs display rotation preferentially at inner radii (Re < 1). In the case of the GC system of NGC 3115 we find a group of GCs with similar kinematics that are not likely to belong to either its spheroid nor disc. For NGC 7457 we find that 70% of its GCs are likely to belong to the disc. Overall, our results suggest that these galaxies assembled into S0s through different evolutionary paths. Mergers seem to have been very important for NGC 2768 and NGC 3115 while NGC 7457 is more likely to have experienced secular evolution.

Recovering the origins of the lenticular galaxy NGC 3115 using multiband imaging

“…For example, by recovering the galaxy kinematics using Planetary Nebulae, Cortesi et al (2013) showed that the disc of NGC 3115 is rotationally supported, but that the value of V/σ is lower than what found for spiral galaxies, suggesting that this galaxy is not simply a faded spiral. Similar results are found by studying the globular cluster population (Zanatta et al 2018) and integrated stellar light (Arnold et al 2011).…”

“…The same result was obtained by studying the globular clusters kinematics (Zanatta et al 2018). Reinforcing this point, Falcón-Barroso et al (2019) show, using CALIFA data of 300 galaxies across the Hubble sequence, that spiral galaxies hardly fade into S0s, unless specific conditions of light concentration, angular momentum and V/σ are satisfied (as for Sa galaxies).…”

“…We propose a formation scenario for NGC 3115 that incorporates results from previous works (Guérou et al 2016;Poci et al 2019;Arnold et al 2011Arnold et al , 2014Dolfi et al 2020;Zanatta et al 2018;Cortesi et al 2013;Peacock et al 2015) with new findings from this work, as explained at the end of the Section 6.3 and summarised in Fig. 12.…”

The complex globular cluster system of the S0 galaxy NGC 4382 in the outskirts of the Virgo Cluster

“…In the Milky Way, stars of accreted dwarf galaxies present different kinematics depending on their in-fall time, where recently acquired satellites have a larger difference to the galaxy systemic velocity and extend to larger radii (Rocha et al 2012). Similar results are found for the GC systems of NGC 1023 and NGC 3115 (Cortesi et al 2016;Zanatta et al 2018), where accreted GCs were encountered on the basis of their kinematics. In the case of NGC 1023, the majority of rejected GCs are consistent with having blue colours.…”

NGC 7457: evidence for merger-driven cylindrical rotation in disc galaxies

“…This is in agreement with Sil'chenko et al (2002) who also proposed a a merger-driven evolution in this galaxy. Zanatta et al (2018) in contrast, using the same approach, found that NGC 7457 has a disc dominated GC population. They claimed that, considering the estimated halo assembly epoch of this galaxy, along with the low density environment of this system and discy distribution of its GCs, a secular evolution scenario is the best mechanism to explain the observed properties of this system.…”