Spiral galaxies with large optical warps

As a result of our statistical study of 540 edge-on galaxies, we present here the images and preliminary statistical analysis of a sub-sample of 60 galaxies, that were selected to be S-type warped spirals. Computing the average volumic density of galaxies from available redshift surveys, a first analysis suggests that warped galaxies are found in denser environments. Only the clearest and strongest warps have been extracted here, and therefore this sample of 60 objects gather the best candidates for future HI or optical works on galaxy warps.Comment: 7 pages, 6 figures, accepted in Astronomy and Astrophysics Su

Molecular content of polar-ring galaxies

We have searched for CO lines in a sample of 21 new morphologically determined polar-ring galaxies (of which nine are kinematically confirmed), obtained from a wide search in the Galaxy Zoo project by Moiseev and collaborators. Polar-ring galaxies (PRG) are a unique class of objects, tracing special episodes in the galaxy mass assembly: they can be formed through galaxy interaction and merging, but also through accretion from cosmic filaments. Furthermore, they enable the study of dark matter haloes in three dimensions. The polar ring itself is a sub-system rich in gas, where molecular gas is expected, and new stars are formed. Among the sample of 21 PRG, we have detected five CO-rich systems, that can now be followed up with higher spatial resolution. Their average molecular mass is 9.4 10**9 Mo, and their average gas fraction is 27% of their baryonic mass, with a range from 15 to 43%, implying that they just accreted a large amount of gas. The position of the detected objects in the velocity-magnitude diagram is offset from the Tully-Fisher relation of normal spirals, as was already found for PRGs. This work is part of our multi-wavelength project to determine the detailed morphology and dynamics of polar-ring galaxies, test through numerical models their formation scenario, and deduce their dark matter content and 3D-shape.Comment: 7 pages, 4 figures, accepted in Astronomy and Astrophysic

The luminosity function of ringed galaxies

We perform an analysis of the luminosity functions (LFs) of two types of ringed galaxies -- polar-ring galaxies and collisional ring galaxies -- using data from the Sloan Digital Sky Survey (SDSS). Both classes of galaxies were formed as a result of interaction with their environment and they are very rare objects. We constructed LFs of galaxies by different methods and found their approximations by the Schechter function. The luminosity functions of both types of galaxies show a systematic fall-off at low luminosities. The polar structures around bright ($M_r \leq -20^m$) and red ($g-r > +0.8$) galaxies are about twice as common as around blue ones. The LF of collisional rings is shifted towards brighter luminosities compared to polar-ring galaxies. We analysed the published data on the ringed galaxies in several deep fields and confirmed the increase in their volume density with redshift: up to z$\sim$1 their density grows as $(1+z)^m$, where $m \gtrsim 5$.Comment: 10 pages, accepted for publication in MNRA

Polar-ring galaxies in the Illustris TNG50 simulation

Polar-ring galaxies (PRGs) are an outstanding example of galaxies with misaligned kinematics where a typically red central galaxy is surrounded by a large-scale ring or disk of stars, gas and dust oriented almost perpendicular to the main body. It is believed that polar structures are formed in a secondary event after the assembly of a central galaxy, but due to their scarcity, their formation paths are not well constrained yet. We present a study of PRGs from TNG50 cosmological simulations, focusing on the origin of their polar structures. Based on the synthetic images and baryonic mass distribution, we found 6 galaxies with stellar polar rings. Using Supplementary Data Catalogues and available particle data, we confirm that the selected galaxies are direct analogs of real PRGs. In our sample, the polar structures are a result of the close interaction between the host galaxy and its companion. We track two formation paths for the stellar polar rings in our sample: (i) star formation in the accreted gas, (ii) tidal disruption of the satellite's stellar component. Rings formed during the first scenario are, on average, bluer and younger than ones formed due to the satellite disruption. We report a steady increase of the ring's inclination around the two most massive galaxies across a few billion years with a rate of $\approx8^{\circ}$/Gyr. The formation of a polar structure in some cases can increase the nuclear activity of the central galaxy and/or turn the active nucleus off completely.Comment: 19 pages, 18 figures, accepted for publication in MNRA