The ASTRODEEP Frontier Fields catalogues

Abstract

Context. The Frontier Fields survey is a pioneering observational program aimed at collecting photometric data, both from space (Hubble Space Telescope and Spitzer Space Telescope) and from ground-based facilities (VLT Hawk-I), for six deep fields pointing at clusters of galaxies and six nearby deep parallel fields, in a wide range of passbands. The analysis of these data is a natural outcome of the Astrodeep project, an EU collaboration aimed at developing methods and tools for extragalactic photometry and creating valuable public photometric catalogues. Aims. We produce multiwavelength photometric catalogues (from B to 4.5 µm) for the first two of the Frontier Fields, Abell-2744 and MACS-J0416 (plus their parallel fields). Methods. To detect faint sources even in the central regions of the clusters, we develop a robust and repeatable procedure that uses the public codes Galapagos and Galfit to model and remove most of the light contribution from both the brightest cluster members, and the intra-cluster light. We perform the detection on the processed HST H160 image to obtain a pure H-selected sample, which is the primary catalogue that we publish. We also add a sample of sources which are undetected in the H160 image but appear on a stacked infrared image. Photometry on the other HST bands is obtained using SExtractor, again on processed images after the procedure for foreground light removal. Photometry on the Hawk-I and IRAC bands is obtained using our PSF-matching deconfusion code t-phot. A similar procedure, but without the need for the foreground light removal, is adopted for the Parallel fields.Results. The procedure of foreground light subtraction allows for the detection and the photometric measurements of ∼2500 sources per field. We deliver and release complete photometric H-detected catalogues, with the addition of the complementary sample of infrared-detected sources. All objects have multiwavelength coverage including B to H HST bands, plus K-band from Hawk-I, and 3.6−4.5 µm from Spitzer. full and detailed treatment of photometric errors is included. We perform basic sanity checks on the reliability of our results. Conclusions. The multiwavelength photometric catalogues are available publicly and are ready to be used for scientific purposes. Our procedures allows for the detection of outshone objects near the bright galaxies, which, coupled with the magnification effect of the clusters, can reveal extremely faint high redshift sources. Full analysis on photometric redshifts is presented in Paper II.

Paving the way for the JWST: witnessing globular cluster formation at z > 3

“…The optical counterpart is well detected in the HFF deep photometry with a F105W magnitude of 28.33 ± 0.09 (Castellano et al 2016b;Merlin et al 2016). The object is located at 27 kpc from GC1 in the source plane, and is therefore distinct from system 2 but plausibly part of the same environment of GC1 and D1.…”

“…All the objects lensed by the HFF cluster MACS J0416 benefit from the Astrodeep photometric catalog (Merlin et al 2016) and the redshift measurements from MUSE observations. SED-fitting of the Astrodeep sources in MACS J0416 was presented in Castellano et al (2016b) on the basis of photometric redshifts: here we update that analysis by fixing the redshift at the spectroscopic value and allowing also for very young ages (1-10 Myrs) that were not previously considered.…”

The Frontier Fields: Survey Design and Initial Results

“…Deep Spitzer IRAC imaging at 3.6 and 4.5 μm places additional constraints on galaxy redshifts (Table 3, Figure 7). Fitting of the spectral energy distribution of the multi-wavelength photometry from the combined HST and Spitzer imaging (e.g., Merlin et al 2016) provides photometric redshifts and estimates of the galaxies' stellar masses and recent star formation histories (e.g., .…”

“…However, the intrinsic depths for background galaxies lensed by the clusters are deeper than the parallel fields (considering the contribution to the foreground by the intracluster light and galaxies in the cluster; see Livermore et al (2017) and Merlin et al (2016) for strategies for subtracting the intracluster light), with typical magnifications across the cluster pointings of ∼1.5-2 and small areas magnified by factors as large as 10-100.…”

“…All of the public HFF lensing models provide a range of possible realizations from which the statistical uncertainty of a given model set may be calculated (typically 100 but no fewer than 30). We plot the cumulative distribution of the galaxy magnification uncertainties σ(model)/ ( ) m á ñ model , for the galaxies and photometric redshifts provided by the ASTRO-DEEP catalogs (Merlin et al 2016;Castellano et al 2016a) for Abell 2744 (Figure 9) and MACSJ0416.1-2403 (Figure 10). Generally, the statistical uncertainties are reduced for the models computed with the new HFF data sets, with more dramatic reductions for the methods that rely strongly upon the strong-lensing constraints.…”