Astro Data Lab

Description

The Dark Energy Camera Plane Survey (DECaPS) is a multi-band imaging survey obtained with the Dark Energy Camera (DECam) to map the Galactic Plane. Browse these pages to learn more about DECaPS and to access the data. The DECaPS DR2 overview paper (Saydjari et al. 2022) and the DECaPS DR1 overview paper (Schlafly et al. 2017) describe the survey in detail, including its goals, survey strategy, reduction, and calibration. More information is also available on the DECaPS team website.

The decaps_dr2.object table and decaps_dr1.object table have been crossmatched against our default reference datasets within a 1.5 arcsec radius, nearest neighbor only. These tables will appear with x1p5 in their name in our table browser. Example: decaps_dr2.x1p5__object__gaia_dr3__gaia_source.

Data Releases

Second Data Release (DECaPS DR2)

DECaPS DR2 is a five-band optical and near-infrared survey of the southern Galactic plane with the Dark Energy Camera (DECam) on the 4.0m Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile. The survey is designed to reach past the main-sequence turn-off at the distance of the Galactic center through a reddening E(B-V) of 1.5 mag and with average seeing around 1''. The footprint covers |b| ≤ 10 deg and 6 deg > l > −124 deg, complementary to coverage by Pan-STARRS1. DECaPS DR2 simultaneously solves for the positions and fluxes of all the sources in each image, delivering positions and fluxes of 3.32 billion stars with up to 5 mmag repeatability. Most of these objects are highly reddened and deep in the Galactic disk, probing the structure and properties of the Milky Way and its interstellar medium.

The table below lists the tables available in the decaps_dr2 database. A few important notes about the object table are mentioned in the DECaPS Catalogs website and copied below for reference:

For quantities with an additional "_OK" field, the first is an average over all detections and the "_OK" field is limited to only "OK" detections. Detections are "OK" if no bad flag bits were set for the center pixel, the quality factor and RCHI2 pass a cut, and the flux uncertainty is nonzero. See the DECaPS DR2 release paper for these cuts and bad flag lists.

The obj_id for DECaPS DR2 has no relation to the obj_id for objects that also appear in DECaPS DR1.

All fluxes are reported in "maggies" (Mgy) which are equivalent to 3631 Jy and are a convenient unit so that -2.5*log10(flux) is in AB magnitudes.

First Data Release (DECaPS DR1)

The DECaPS first data release took place in October 2017. It was published on the DECaPS team website, and described in an accompanying paper (Schlafly et al. 2017). The data release was also featured in a NOAO Currents article.

The DECaPS data were released in two stages at the Astro Data Lab. First, we released the object table, which corresponds to the band-merged catalogs loaded into a database table, as well as the survey tables (ccds, depth, imdb, zps). Second, we have released a measurement table consisting of the individual-image catalogs (meas). The measurement table was modified relative to the current version available on the DECaPS team website to include the obj_id allowing to join directly with the object table.

The table below lists the tables available in the decaps_dr1 database. A few important notes about the object table are listed on the DECaPS Catalogs webpage, and copied below for reference:

A "good" detection in these catalogs means that the detection's central pixel had no "bad" flags set in the Community Pipeline data quality image, and that at least 85% of the source's flux (according to the model PSF and model location of the source) lands in a pixel with non-zero weight, according to the Community Pipeline inverse variance image.

All fluxes are in units of "3631 Jy," so that the AB magnitudes of the stars are given by -2.5*log10(flux)

The absolute calibration is based on the Tonry et al. (2012) absolute calibration of PS1. Subsequent analyses (Scolnic et al., 2014, 2015) of the PS1 survey found offsets relative to AB. To shift the DECaPS magnitudes to the Scolnic et al. (2015) absolute calibration, offsets of 0.020, 0.033, 0.024, 0.028, and 0.011 mag must be added to the DECaPS grizY magnitudes, respectively.