Photometric Properties of Kiso Ultraviolet-Excess Galaxies in the Lynx-Ursa Major Region

We have performed a systematic study of several regions in the sky where the number of galaxies exhibiting star formation (SF) activity is greater than average. We used Kiso ultraviolet-excess galaxies (KUGs) as our SF-enhanced sample. By statistically comparing the KUG and non-KUG distributions, we discovered four KUG-rich regions with a size of ∼ 10×10. One of these regions corresponds spatially to a filament of length ∼ 60 h Mpc in the Lynx-Ursa Major region (α ∼ 9 − 10 , δ ∼ 42 − 48). We call this “the Lynx-Ursa Major (LUM) filament”. We obtained V (RI)C surface photometry of 11 of the KUGs in the LUM filament and used these to investigate the integrated colors, distribution of SF regions, morphologies, and local environments. We found that these KUGs consist of distorted spiral galaxies and compact galaxies with blue colors. Their star formation occurs in the entire disk, and is not confined to just the central regions. The colors of the SF regions imply that active star formation in the spiral galaxies occurred 10 yr ago, while that of the compact objects occurred 10 yr ago. Though the photometric characteristics of these KUGs are similar to those of interacting galaxies or mergers, most of these KUGs do not show direct evidence of merger processes. Subject headings: galaxies: KUG — galaxies: photometry — galaxies: starburst — galaxies: statistics