Deep Extragalactic VIsible Legacy Survey: Data Release 1 blended spectra search for candidate strong gravitational lenses

Here, we present a catalogue of blended spectra in Data Release 1 of the Deep Extragalactic VIsible Legacy Survey (DEVILS) on the Anglo-Australian Telescope. Of the 23 197 spectra, 181 showed signs of a blend of redshifts and spectral templates. We examine these blends in detail for signs of either a candidate strong lensing galaxy or a useful overlapping galaxy pair. One of the three DEVILS target fields, COSMOS (D10), is close to complete and it is fully imaged with Hubble Space Telescope Advanced Camera for Surveys, and we visually examine the 57 blended spectra in this field in the F814W postage stamps. Nine are classical strong lensing candidates with an elliptical as the lens, out to higher redshifts than any previous search with spectroscopic surveys such as Sloan Digital Sky Survey (SDSS) or Galaxy And Mass Assembly. The gravitational lens candidate success rate is similar to earlier such searches (0.1 per cent). Strong gravitational lenses identified with blended spectroscopy have typically shown a high success rate (\u3e70 per cent), which make these interesting targets for future higher resolution lensing studies, monitoring for supernova cosmography, or searches for magnified atomic hydrogen signal

From rest-frame luminosity functions to observer-frame colour distributions: tackling the next challenge in cosmological simulations

Galaxy spectral energy distributions (SEDs) remain among the most challenging yet informative quantities to reproduce in simulations due to the large and complex mixture of physical processes that shape the radiation output of a galaxy. With the increasing number of surveys utilising broadband colours as part of their target selection criteria, the production of realistic SEDs in simulations is necessary for assisting in survey design and interpretation of observations. The recent success in reproducing the observed luminosity functions (LF) from far-UV to far-IR, using the state-of-the-art semi-analytic model \shark\ and the SED generator \prospect, represents a critical step towards better galaxy colour predictions. We show that with \shark\ and \prospect\ we can closely reproduce the optical colour distributions observed in the panchromatic GAMA survey. The treatment of feedback, star formation, central-satellite interactions and radiation re-processing by dust are critical for this achievement. The first three processes create a bimodal distribution, while dust attenuation defines the location and shape of the blue and red populations. While a naive comparison between observation and simulations displays the known issue of over-quenching of satellite galaxies, the introduction of empirically-motivated observational errors and classification from the same group finder used in GAMA greatly reduces this tension. The introduction of random re-assignment of $\sim 15\%$ of centrals/satellites as satellites/centrals on the simulation classification closely resembles the outcome of the group finder, providing a computationally less intensive method to compare simulations with observations.Comment: Accepted for publication in MNRAS after minor corrections (20 pages, 19 figures

Deep Extragalactic VIsible Legacy Survey: Data Release 1 blended spectra search for candidate strong gravitational lenses

Here, we present a catalogue of blended spectra in Data Release 1 of the Deep Extragalactic VIsible Legacy Survey (DEVILS) on the Anglo-Australian Telescope. Of the 23 197 spectra, 181 showed signs of a blend of redshifts and spectral templates. We examine these blends in detail for signs of either a candidate strong lensing galaxy or a useful overlapping galaxy pair. One of the three DEVILS target fields, COSMOS (D10), is close to complete and it is fully imaged with Hubble Space Telescope Advanced Camera for Surveys, and we visually examine the 57 blended spectra in this field in the F814W postage stamps. Nine are classical strong lensing candidates with an elliptical as the lens, out to higher redshifts than any previous search with spectroscopic surveys such as Sloan Digital Sky Survey (SDSS) or Galaxy And Mass Assembly. The gravitational lens candidate success rate is similar to earlier such searches (0.1 per cent). Strong gravitational lenses identified with blended spectroscopy have typically shown a high success rate (\u3e70 per cent), which make these interesting targets for future higher resolution lensing studies, monitoring for supernova cosmography, or searches for magnified atomic hydrogen signal

The Hyper Suprime-Cam extended Point Spread Functions and applications to measuring the intra-halo light

We present extended point spread function (PSF) models for the Hyper Suprime-Cam Subaru Strategic Program Public Data Release 3 (HSC-SSP PDR3) in all $\textit{g,r,i,Z}$ and $\textit{Y}$-bands. Due to its 8.2m primary mirror and long exposure periods, HSC combines deep images with wide-field coverage, making it one of the most suitable observing facilities for low surface brightness (LSB) studies. By applying a median stacking technique of point sources with different brightnesses, we show how to construct the HSC-SSP PDR3 PSF models to an extent of R $\sim$ 5.6 arcmin. These new PSFs provide the community with a crucial tool to characterise LSB properties at large angles. We apply our HSC PSFs and demonstrate that they behave reasonably in two cases: first, to generate a 2-D model of a bright star, and second, to remove the PSF-scattered light from an Ultra Deep image of the 400020 Galaxy And Mass Assembly (GAMA) group in the SXDS field. Our main focus in this second application is characterising the $\textit{r}$-band intra-halo light (IHL) component of 400020. Building on advanced source extraction techniques with careful consideration of PSF flux, we measure the IHL surface brightness (SB) group profile up to $\sim$ 31 mag arcsec$^{-2}$ and R = 300 kpc. We estimate the IHL fraction ($\mathrm{f_{IHL}}$) profile, with a mean of $\mathrm{f_{IHL}}$ $\sim$ 0.13. Our results show that not removing the PSF light can overestimate the IHL SB by $\sim$ 1.7 mag arcsec$^{-2}$ and the $\mathrm{f_{IHL}}$ by $\sim$ 30%.Comment: 21 pages, 19 figures, submitted to MNRA

Galaxy And Mass Assembly (GAMA): the dependence of star formation on surface brightness in low-redshift galaxies

The star-formation rate in galaxies is well known to correlate with stellar mass (the ‘star-forming main sequence’). Here, we extend this further to explore any additional dependence on galaxy surface brightness, a proxy for stellar mass surface density. We use a large sample of low-redshift (z ≤ 0.08) galaxies from the Galaxy And Mass Assembly survey which have both spectral energy distribution (SED) derived star-formation rates and photometric bulge-disc decompositions, the latter providing measures of disc surface brightness and disc masses. Using two samples, one of galaxies fitted by a single component with Sérsic index below 2 and one of the discs from two-component fits, we find that once the overall mass dependence of star-formation rate is accounted for, there is no evidence in either sample for a further dependence on stellar surface density

Strategy for Dynamic Wisp Removal in James Webb Space Telescope NIRCam Images

The James Webb Space Telescope (JWST) near-infrared camera (NIRCam) has been found to exhibit serious wisp-like structures in four of its eight short-wavelength detectors. The exact structure and strength of these wisps is highly variable with the position and orientation of JWST, so the use of static templates is non-optimal. Here we investigate a dynamic strategy to mitigate these wisps using long-wavelength reference images. Based on a suite of experiments where we embed a worst-case scenario median-stacked wisp into wisp-free images, we define suitable parameters for our wisp removal strategy. Using this setup we re-process wisp-affected public Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) data in the North Ecliptic Pole Time Domain Field (NEP-TDF) field, resulting in significant visual improvement in our detector frames and reduced noise in the final stacked images.Comment: 16 pages, 10 figures, submitted to PASP, comments welcom

Galaxy quenching timescales from a forensic reconstruction of their colour evolution

The timescales on which galaxies move out of the blue cloud to the red sequence ($\tau^{}_\mathrm{Q}$) provide insight into the mechanisms driving quenching. Here, we build upon previous work, where we showcased a method to reconstruct the colour evolution of observed low-redshift galaxies from the Galaxy And Mass Assembly (GAMA) survey based on spectral energy distribution (SED) fitting with ProSpect, together with a statistically-driven definition for the blue and red populations. We also use the predicted colour evolution from the SHARK semi-analytic model, combined with SED fits of our simulated galaxy sample, to study the accuracy of the measured $\tau^{}_\mathrm{Q}$ and gain physical insight into the colour evolution of galaxies. In this work, we measure $\tau^{}_\mathrm{Q}$ in a consistent approach for both observations and simulations. After accounting for selection bias, we find evidence for an increase in $\tau^{}_\mathrm{Q}$ in GAMA as a function of cosmic time (from $\tau^{}_\mathrm{Q}\sim1$ Gyr to $\tau^{}_\mathrm{Q}\sim2$ Gyr in the lapse of $\sim4$ Gyr), but not in SHARK ($\tau^{}_\mathrm{Q}\lesssim1$ Gyr). Our observations and simulations disagree on the effect of stellar mass, with GAMA showing massive galaxies transitioning faster, but is the opposite in SHARK. We find that environment only impacts galaxies below $\sim10^{10}$ M$_\odot$ in GAMA, with satellites having shorter $\tau^{}_\mathrm{Q}$ than centrals by $\sim0.4$ Gyr, with SHARK only in qualitative agreement. Finally, we compare to previous literature, finding consistency with timescales in the order of couple Gyr, but with several differences that we discuss.Comment: 17 pages, 14 figures. Submitted to MNRAS. Updated to reflect changes addressing the referee's comment