The Apparent and Absolute Magnitude Distributions of the Kuiper Belt from Single-Night Detections in DEEP

The DECam Ecliptic Exploration Project (DEEP) is a deep survey of the trans-Neptunian solar system being carried out on the 4-meter Blanco telescope at Cerro Tololo Inter-American Observatory in Chile using the Dark Energy Camera (DECam).

This work reports results from an analysis of 20 half-nights of data covering 60 sq. deg. of sky. By combining a shift-and-stack technique with convolutional neural networks, we have achieved a mean limiting magnitude of r ~ 26.3. We characterize the efficiency and false-positive rates for our moving-object detection pipeline, and use this information to construct a Bayesian signal probability for each detected source. Importantly, this allows us to treat all of the KBO detections statistically, simultaneously accounting for efficiency and false positives. We report more than 2000 single-night candidate Kuiper Belt Object (KBO) detections with S/N > 6.5.

DEEP’s combination of survey area and depth is unprecedented, enabling quantitative leaps forward in our understanding of the Kuiper Belt populations. Our rich and uniform data set of single-night detections contains more than an order of magnitude increase in KBOs fainter than r ~ 25 over previous state-of-the-art deep searches in the literature. As such, we have unique constraining power over the faint-and-small ends of the KBO luminosity and size distributions. We use our detections to compute the luminosity function of the Kuiper Belt as a whole, as well as the Cold Classical population. We also provide an updated estimate of the absolute magnitude distribution of the Cold Classicals.