A Survey of Galaxy Redshifts from Low-resolution Slitless Spectra: Suggestion of Large-scale Structures

We have conducted a galaxy survey based on low-resolution slitless spectra taken from the automated CFHT-Laval survey. We present redshift distributions for 522 galaxies distributed in 4 distinct regions of the sky. Redshifts are determined from the shifted positions of the 4000 Å stellar break using an automated break-finding algorithm. The redshifts so obtained have a precision of < 3000 km s-1, good enough to trace the large-scale distribution of galaxies. The most striking feature of the survey is an apparent excess of galaxies at z ~ 0.1 in 8 of the 10 fields probed. Although the statistical significance of the peaks appears marginal (~ 2.5σ per field) after taken in account the small-scale galaxy clustering, the peaks may nevertheless reveal the existence of large-scale structures at z ~ 0.1, indicating that the known large structures in the local universe are not unusual.