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

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 $3 times 10^{10}$M$_odot$. 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.