Environment Dependence of Disk Morphology of Spiral Galaxies

Abstract

We analyze the dependence of disk morphology (arm class, Hubble type, bar type) of nearby spiral galaxies on the galaxy environment by using local background density ($\Sigma_{n}$), projected distance ($r_{p}$), and tidal index ($TI$) as measures of the environment. There is a strong dependence of arm class and Hubble type on the galaxy environment, while the bar type exhibits a weak dependence with a high frequency of SB galaxies in high density regions. Grand design fractions and early-type fractions increase with increasing $\Sigma_{n}$, $1/r_{p}$, and $TI$, while fractions of flocculent spirals and late-type spirals decrease. Multiple-arm and intermediate-type spirals exhibit nearly constant fractions with weak trends similar to grand design and early-type spirals. While bar types show only a marginal dependence on $\Sigma_{n}$, they show a fairly clear dependence on $r_{p}$ with a high frequency of SB galaxies at small $r_{p}$. The arm class also exhibits a stronger correlation with $r_{p}$ than $\Sigma_{n}$ and $TI$, whereas the Hubble type exhibits similar correlations with $\Sigma_{n}$ and $r_{p}$. This suggests that the arm class is mostly affected by the nearest neighbor while the Hubble type is affected by the local densities contributed by neighboring galaxies as well as the nearest neighbor.