TY - JOUR

T1 - What determines the flatness of X-shaped structures in edge-on galaxies?

AU - Smirnov, Anton A.

AU - Sotnikova, Natalia Ya

PY - 2018/12/11

Y1 - 2018/12/11

N2 - Recent observational studies of X-shaped structures revealed that the values of their opening angles lie in a narrow range: from 20 to 43° with smaller X-shaped structures appearing to follow a characteristic opening angle ~27-31°. We use self-consistent numerical simulations to uncover which parameters of host galaxies govern the opening angle spread.We constructed a series of equilibrium models of galaxies with high spatial resolution, varying the dark halo and bulge contribution in the overall gravitational potential, the initial disc thickness of models and the Toomre parameter Q and followed their evolution for almost 8 Gyr. Each model demonstrated the formation of clear X-structures with different flatnesses.We have found that opening angles lie in the range from 25 to 42° throughout the entire evolution. These values are roughly consistent with observational data. The greatest variation in the opening angles is obtained by varying the mass of the dark halo. The initial thickness of the disc and the Toomre parameter are responsible for smaller variations of the angle and shorter X-structures. An increase of both parameters changes the morphology of in-plane bars and X-structures. In some cases we even observed double X-structures. The main effect of the bulge is to prevent buckling at intermediate and late stages of the disc evolution. Comparison of models with different halo masses indicates that the smallest observable values of opening angles can be associated with the presence of a heavy dark halo (more than three masses of the disc within the optical radius).

AB - Recent observational studies of X-shaped structures revealed that the values of their opening angles lie in a narrow range: from 20 to 43° with smaller X-shaped structures appearing to follow a characteristic opening angle ~27-31°. We use self-consistent numerical simulations to uncover which parameters of host galaxies govern the opening angle spread.We constructed a series of equilibrium models of galaxies with high spatial resolution, varying the dark halo and bulge contribution in the overall gravitational potential, the initial disc thickness of models and the Toomre parameter Q and followed their evolution for almost 8 Gyr. Each model demonstrated the formation of clear X-structures with different flatnesses.We have found that opening angles lie in the range from 25 to 42° throughout the entire evolution. These values are roughly consistent with observational data. The greatest variation in the opening angles is obtained by varying the mass of the dark halo. The initial thickness of the disc and the Toomre parameter are responsible for smaller variations of the angle and shorter X-structures. An increase of both parameters changes the morphology of in-plane bars and X-structures. In some cases we even observed double X-structures. The main effect of the bulge is to prevent buckling at intermediate and late stages of the disc evolution. Comparison of models with different halo masses indicates that the smallest observable values of opening angles can be associated with the presence of a heavy dark halo (more than three masses of the disc within the optical radius).

KW - Galaxies: bulges

KW - Galaxies: fundamental parameters

KW - Galaxies: haloes

KW - Galaxies: kinematics and dynamics

KW - Galaxies: structure

KW - INSTABILITY

KW - STELLAR DISKS

KW - galaxies: fundamental parameters

KW - BULGES

KW - galaxies: bulges

KW - PEANUT

KW - galaxies: structure

KW - MASS

KW - DARK-MATTER

KW - galaxies: kinematics and dynamics

KW - HALO

KW - BARS

KW - THICKNESS

KW - galaxies: haloes

KW - KINEMATICS

UR - http://www.scopus.com/inward/record.url?scp=85054203001&partnerID=8YFLogxK

U2 - 10.1093/mnras/sty2423

DO - 10.1093/mnras/sty2423

M3 - Article

AN - SCOPUS:85054203001

VL - 481

SP - 4058

EP - 4076

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 3

ER -