Deep Extragalactic VIsible Legacy Survey (DEVILS): First Data Release Covering The D10 (COSMOS) Region

TL;DR

DEVILS DR1 presents the first public data release for the D10/COSMOS region, delivering 4,859 new high-quality spectroscopic redshifts and a master redshift catalogue that, when combined with external redshift data, yields 7,946 robust redshifts and greatly improved completeness to $Y_{AB}\approx21$. The release includes a comprehensive suite of data products (photometry, SED fits, morphologies, structural parameters, and group environments) plus standardized imaging and 1D spectra, all accessible via Data Central. A key science result demonstrates ubiquitous environmental quenching at intermediate redshift ($0.2<z<0.5$), with suppressed star formation across stellar mass and morphology in denser environments, highlighting the power of a highly complete spectroscopic survey to study environment-driven galaxy evolution. By aligning DEVILS with GAMA and preparing for WAVES, the DR1 data provide a robust foundation for cross-survey comparisons and future deep, wide-area spectroscopic programs.

Abstract

The Deep Extragalactic VIsible Legacy Survey (DEVILS) is a deep, high-completeness multi-wavelength survey based around spectroscopic observations using the Anglo-Australian Telescope's AAOmega spectrograph. The survey covers $\sim4.5$deg$^{2}$ over three extragalactic fields to Y$_{AB}<21.2$mag and probes sources at $0<z<1.2$, with a median redshift of $z=0.53$. Here we describe the DEVILS spectroscopic observations, data reduction and redshift analysis. We then describe and release to the community all DEVILS data in the 10h (D10, COSMOS) region including: i) catalogues of redshifts, photometry, SED fitting for physical properties, visual morphologies, structural decompositions and group environments/halo masses, ii) matched imaging in 28 bands from x-rays to radio continuum, and iii) reduced 1D spectra. All data are made publicly available through Data Central. Within D10 we obtain 5,442 new high-quality spectroscopic redshifts. When combined with existing, lower-quality, redshift information ($i.e.$ photometric redshifts) this is increased to 7,946. Of these, 3,122 have a spectroscopic redshift from another source (many that was not available at the time of the DEVILS observations). As such, DEVILS provides new unique high-quality spectroscopic redshifts for 4,824 faint sources in COSMOS. This increases the spectroscopic completeness at Y-mag$\sim$21 from $\sim$50% in other samples to $\sim$90% in DEVILS. Finally, we show the power of this dataset by exploring the suppression of star formation in over-dense environments, split by morphology and stellar mass, and highlighting the ubiquitous nature of environmental quenching.

Figures (19)

• Figure 1: Left: The colour-magnitude density of all targets in the D10 region. Right: The colour-magnitude completeness of sources with pre-DEVILS robust spectroscopic redshifts. Targets without a spectroscopic redshift are typically faint, but span a broad range of rest-frame colours. In existing spectroscopic samples, there is a higher fraction of blue galaxies that have a spectroscopic redshift at faint magnitudes - as expected.
• Figure 2: Left: The spatial source density of targets in the D10 region. Middle: The spatial completeness of sources with pre-DEVILS robust spectroscopic redshifts - completeness is patchy and higher in the central region of the field. Right: The pre-DEVILS photometric redshift distribution of targets in the D10 region taken from Laigle16, all targets are shown in blue, and those with a pre-DEVILS robust spectroscopic redshifts shown in red. Pre-DEVILS completeness to our target sample is $\sim0.5$ at all redshifts.
• Figure 3: Examples of 1D DEVILS spectra for source UID=101501853032307936 indicating the DEVILS inverse variance-weighted stacking procedure. Faint grey lines show the raw AAOmega spectrum, solid green lines show a Hanning smoothed version of this spectrum. Key emission (blue), absorption (green) and AGN (light blue) lines at the final source redshift are shown as vertical dashed lines. Panels from top to bottom show successive stacks of data building up exposure time and increasing signal-to-noise. The last observation date, number of observations, total exposure time, SNR (measured as a median SNR/pixel between 6500-7000Å), best-fit redshift and redshift probability, P($z$), are given in the legend. In the top panel the source is too low signal-to-noise for the correct redshift to be obtained. In the second/third panels the correct redshift is found, but the P($z$) is too low for this to be secure. In the bottom row, the correct redshift is found at a high probability and the source stops being observed.
• Figure 4: Examples of 1D DEVILS spectra from our final reduced sample. Here we show random examples for faint sources at a range of redshift and requiring a range of exposure times to obtain a secure redshift (given in the top left legend). Faint grey lines show the raw AAOmega spectrum, solid green lines show a Hanning smoothed version of this spectrum, red lines show the sky spectrum offset for clarity. Key emission (blue), absorption (green) and AGN (light blue) lines at the source's redshift are shown as vertical dashed lines.
• Figure 5: Secure, P($z$)$>$0.95, redshift accumulation rate in the D10 as a function of time. Grey shaded region shows the period when the D10 field was observable from the AAT for $>$4h/night. The 2020 observing block was significantly affected by COVID shutdowns and instrument failures.