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 (n), projected distance (rp), and tidal index (T I) 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 n, 1/rp, and T I, 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 n, they show a fairly clear dependence on rp with a high frequency of SB galaxies at small rp. The arm class also exhibits a stronger correlation with rp than n and T I, whereas the Hubble type exhibits similar correlations with n and rp. 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.

ABSTRACT
1. INTRODUCTION
2. OBSERVATIONAL DATA
3. LOCAL BACKGROUND DENSITY AS A MEASURE OF ENVIRONMENT
    3.1 Effect of Mr* and ΔV* on Neighbor Search
    3.2 Local Background Density from the nth Nearest Neighbor
    3.3 Disk Morphology and Local Background Densities
4. OTHER MEASURES OF LOCAL ENVI-RONMENT
    4.1 Projected Distance to the Nearest Neigh-bor
    4.2 Tidal Index
5. DISCUSSION
6. CONCLUSIONS
REFERENCES

• HONG BAE ANN(Department of Earth Science Education, Pusan National University)