TY - JOUR

T1 - Two-component gravitational instability in spiral galaxies

AU - Marchuk, A. A.

AU - Sotnikova, N. Y.

PY - 2018/4/21

Y1 - 2018/4/21

N2 - We applied a criterion of gravitational instability, valid for two-component and infinitesimally thin discs, to observational data along the major axis for seven spiral galaxies of early types. Unlike most papers, the dispersion equation corresponding to the criterion was solved directly without using any approximation. The velocity dispersion of stars in the radial direction σR was limited by the range of possible values instead of a fixed value. For all galaxies, the outer regions of the disc were analysed up to R ≤ 130 arcsec. The maximal and sub-maximal disc models were used to translate surface brightness into surface density. The largest destabilizing disturbance stars can exert on a gaseous disc was estimated. It was shown that the two-component criterion differs a little from the one-fluid criterion for galaxies with a large surface gas density, but it allows to explain large-scale star formation in those regions where the gaseous disc is stable. In the galaxy NGC 1167 star formation is entirely driven by the self-gravity of the stars. A comparison is made with the conventional approximations which also include the thickness effect and with models for different sound speed cg. It is shown that values of the effective Toomre parameter correspond to the instability criterion of a two-component disc Qeff < 1.5-2.5. This result is consistent with previous theoretical and observational studies.

AB - We applied a criterion of gravitational instability, valid for two-component and infinitesimally thin discs, to observational data along the major axis for seven spiral galaxies of early types. Unlike most papers, the dispersion equation corresponding to the criterion was solved directly without using any approximation. The velocity dispersion of stars in the radial direction σR was limited by the range of possible values instead of a fixed value. For all galaxies, the outer regions of the disc were analysed up to R ≤ 130 arcsec. The maximal and sub-maximal disc models were used to translate surface brightness into surface density. The largest destabilizing disturbance stars can exert on a gaseous disc was estimated. It was shown that the two-component criterion differs a little from the one-fluid criterion for galaxies with a large surface gas density, but it allows to explain large-scale star formation in those regions where the gaseous disc is stable. In the galaxy NGC 1167 star formation is entirely driven by the self-gravity of the stars. A comparison is made with the conventional approximations which also include the thickness effect and with models for different sound speed cg. It is shown that values of the effective Toomre parameter correspond to the instability criterion of a two-component disc Qeff < 1.5-2.5. This result is consistent with previous theoretical and observational studies.

KW - Galaxies: ISM

KW - Galaxies: kinematics and dynamics

KW - Galaxies: star formation

KW - Galaxies: structure

KW - Instabilities

KW - ISM: kinematics and dynamics

KW - NEARBY GALAXIES

KW - IRREGULAR GALAXIES

KW - DISC GALAXIES

KW - SURFACE PHOTOMETRY

KW - VELOCITY DISPERSION

KW - STAR-FORMATION THRESHOLDS

KW - GALACTIC DISKS

KW - galaxies: star formation

KW - instabilities

KW - galaxies: structure

KW - galaxies: ISM

KW - CENTRAL REGION

KW - galaxies: kinematics and dynamics

KW - H-ALPHA

KW - STABILITY PARAMETER

UR - http://www.scopus.com/inward/record.url?scp=85046082403&partnerID=8YFLogxK

UR - http://www.mendeley.com/research/twocomponent-gravitational-instability-spiral-galaxies

U2 - 10.1093/mnras/sty100

DO - 10.1093/mnras/sty100

M3 - Article

AN - SCOPUS:85046082403

VL - 475

SP - 4891

EP - 4910

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 4

ER -