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 thenumber of galaxies exhibiting star formation (SF) activity is greater thanaverage. We used Kiso ultraviolet-excess galaxies (KUGs) as our SF-enhancedsample. By statistically comparing the KUG and non-KUG distributions, wediscovered four KUG-rich regions with a size of $\sim 10^\circ \times10^\circ$. One of these regions corresponds spatially to a filament of length$\sim 60 h^{-1}$ Mpc in the Lynx-Ursa Major region ($\alpha \sim 9^{\rm h} -10^{\rm h}, \delta \sim 42^\circ - 48^\circ$). We call this ``the Lynx-UrsaMajor (LUM) filament''. We obtained $V(RI)_{\rm C}$ surface photometry of 11 ofthe KUGs in the LUM filament and used these to investigate the integratedcolors, distribution of SF regions, morphologies, and local environments. Wefound that these KUGs consist of distorted spiral galaxies and compact galaxieswith blue colors. Their star formation occurs in the entire disk, and is notconfined to just the central regions. The colors of the SF regions imply thatactive star formation in the spiral galaxies occurred $10^{7 - 8}$ yr ago,while that of the compact objects occurred $10^{6-7}$ yr ago. Though thephotometric characteristics of these KUGs are similar to those of interactinggalaxies or mergers, most of these KUGs do not show direct evidence of mergerprocesses.Comment: 39 pages LaTeX, using aasms4.sty, 20 figures, ApJS accepted. The Title of the previous one was truncated by the author's mistake, and is corrected. Main body of the paper is unchange