SDSS-IV MaNGA: Integral-field kinematics and stellar population of a sample of galaxies with counter-rotating stellar disks selected from about 4000 galaxies

Abstract

We present the kinematics and stellar population properties of a sample of 53 galaxies (50 are Early-Type galaxies, ETGs) with Counter-Rotating Disks (CRD) extracted from a sample of about 4000 galaxies of all morphological types in the MaNGA survey (DR16). The kinematic maps were used to select galaxies based on evidence of counter-rotation in the velocity maps or two peaks in the velocity dispersion maps. For about 1/3 of the sample, the counter-rotating components can also be separated spectroscopically. We then produced the age and metallicity maps, and compared the stellar population properties to those of the general ETGs population. We found that CRDs have similar trends in age and metallicity, but they are generally less metallic at low masses. The metallicity gradients are similar; instead, age gradients are typically flatter and confined within a smaller range of values. We compared the velocity fields of the ionized gas and the stars, and found that in 25 cases the gas corotates with either the inner (13 cases) or the outer (12 cases) disk, and in 9 cases the gaseous and stellar disks are misaligned. With one exception, all misaligned cases have stellar masses less than 3 × 10 10 M . We also compared stellar and gaseous disks with age maps and found that in most cases the gas corotates with the younger disk. We looked for evidences of multimodality in the stellar populations, and found it in 25 galaxies, plus 11 cases with evidences of ongoing star formation, and the latter are the youngest and least massive galaxies; 13 galaxies, instead, exhibit unimodality, and are the oldest and most massive CRDs. As a general result, our work supports different formation scenarios for the kinematic class of counter-rotators.

SDSS-IV MaNGA : spatial resolved properties of kinematically misaligned galaxies

“…In the last decade, especially since the development of large integral-field spectroscopic surveys, such as CALIFA (Sánchez et al 2012), SAMI (Croom et al 2012) and ATLAS 3D (Cappellari et al 2011), series of works have been developed in order to understand the origin of the kinematically misaligned gas components. These studies include morphologies/environments (Davis et al 2011;Barrera-Ballesteros et al 2014Jin et al 2016;Bassett et al 2017;Yu et al 2021), stellar populations (Chen et al 2016;Jin et al 2016;Bevacqua et al 2021), gas-phase metallicities (Chen et al 2016;Jin et al 2016), kinematics (Katkov et al 2014;Naab et al 2014;Bevacqua et al 2021). Following the development in the observations, gas-star misaligned galaxies are also found in cosmological simulation (Osman & Bekki 2017;Bassett et al 2017;Taylor et al 2018;Duckworth et al 2019;Starkenburg et al 2019;Duckworth et al 2020a,b;Khoperskov et al 2020;Khim et al 2021), in which we can trace back the formation histories of the misaligned galaxies, searching for the physical mechanisms responsible for misaligned gas-star kinematics.…”