The Dark Energy Camera Plane Survey 2 (DECaPS2): More Sky, Less Bias, and Better Uncertainties

TL;DR

DECaPS2 provides an extensive, improved optical and near-infrared survey of the southern Galactic plane, with enhanced data reduction techniques, better bias correction, and publicly available catalogs, aiding Galactic structure studies.

Contribution

The paper introduces new data reduction and bias correction methods for the DECaPS2 survey, improving photometric accuracy and uncertainty estimates over previous releases.

Findings

Survey covers 6.5% of the sky with 3.32 billion objects.

Implemented synthetic source injection tests for validation.

Applied new de-biasing techniques to improve flux uncertainties.

Abstract

Deep optical and near-infrared imaging of the entire Galactic plane is essential for understanding our Galaxy's stars, gas, and dust. The second data release of the DECam Plane Survey (DECaPS2) extends the five-band optical and near-infrared survey of the southern Galactic plane to cover $6.5\%$ of the sky, |b| < 10{\deg} and 6{\deg} > l > -124{\deg}, complementary to coverage by Pan-STARRS1. Typical single-exposure effective depths, including crowding effects and other complications, are 23.5, 22.6, 22.1, 21.6, and 20.8 mag in $g$, $r$, $i$, $z$, and $Y$ bands, respectively, with around 1 arcsecond seeing. The survey comprises 3.32 billion objects built from 34 billion detections in 21.4 thousand exposures, totaling 260 hours open shutter time on the Dark Energy Camera (DECam) at Cerro Tololo. The data reduction pipeline features several improvements, including the addition of synthetic source injection tests to validate photometric solutions across the entire survey footprint. A convenient functional form for the detection bias in the faint limit was derived and leveraged to characterize the photometric pipeline performance. A new post-processing technique was applied to every detection to de-bias and improve uncertainty estimates of the flux in the presence of structured backgrounds, specifically targeting nebulosity. The images and source catalogs are publicly available at http://decaps.skymaps.info/.