The Hawk-I UDS and GOODS Survey (HUGS): Survey design and deepK-band number counts

Abstract

We present the results of a new, ultra-deep, near-infrared imaging survey executed with the Hawk-I imager at the ESO VLT, of which we make all the data (images and catalog) public. This survey, named HUGS (Hawk-I UDS and GOODS Survey), provides deep, high-quality imaging in the K and Y bands over the portions of the UKIDSS UDS and GOODS-South fields covered by the CANDELS HST WFC3/IR survey. In this paper we describe the survey strategy, the observational campaign, the data reduction process, and the data quality. We show that, thanks to exquisite image quality and extremely long exposure times, HUGS delivers the deepest K-band images ever collected over areas of cosmological interest, and in general ideally complements the CANDELS data set in terms of image quality and depth. In the GOODS-S field, the K-band observations cover the whole CANDELS area with a complex geometry made of 6 different, partly overlapping pointings, in order to best match the deep and wide areas of CANDELS imaging. In the deepest region (which includes most of the Hubble Ultra Deep Field) exposure times exceed 80 hours of integration, yielding a 1 − σ magnitude limit per square arcsec of 28.0 AB mag. The seeing is exceptional and homogeneous across the various pointings, confined to the range 0.38-0.43 arcsec. In the UDS field the survey is about one magnitude shallower (to match the correspondingly shallower depth of the CANDELS images) but includes also Y-band band imaging (which, in the UDS, was not provided by the CANDELS WFC3/IR imaging). In the K-band, with an average exposure time of 13 hours, and seeing in the range 0.37-0.43 arcsec, the 1 − σ limit per square arcsec in the UDS imaging is 27.3 AB mag. In the Y-band, with an average exposure time 8 h, and seeing in the range 0.45-0.5 arcsec, the imaging yields a 1 − σ limit per square arcsec of 28.3 AB mag. We show that the HUGS observations are well matched to the depth of the CANDELS WFC3/IR data, since the majority of even the faintest galaxies detected in the CANDELS H-band images are also detected in HUGS. Finally we present the K-band galaxy number counts produced by combining the HUGS data from the two fields. We show that the slope of the number counts depends sensitively on the assumed distribution of galaxy sizes, with potential impact on the estimated extra-galactic background light.

z ≳ 7 GALAXIES WITH RED SPITZER/IRAC [3.6]–[4.5] COLORS IN THE FULL CANDELS DATA SET: THE BRIGHTEST-KNOWN GALAXIES AT z ∼ 7–9 AND A PROBABLE SPECTROSCOPIC CONFIRMATION AT z = 7.48

“…These observations are available over the CANDELS-UDS+COSMOS fields through HAWK-I and VISTA as part of the HUGS (Fontana et al 2014) and UltraVISTA (McCracken et al 2012) programs, respectively. A more detailed description of the observations we utilize in constructing our source catalogs, as well as our procedure for constructing these catalogs, is provided in Bouwens et al (2015)( see Table 1, Figure 2, and Section 3 from Bouwens et al 2015).…”

The role of galaxy mass on AGN emission: a view from the VANDELS survey

“…In these regions, the official photometric catalogues produced by the CANDELS team were used as master catalogues (Galametz et al 2013;Guo et al 2013). The only differences are that the Ks HAWKI photometry has been updated to include the final HUGS survey data (see Fontana et al 2014) and the photometry in the CTIO U band filter has been removed. Fluxes are corrected to total based on the ratio of F160W flux ISO and F160W flux AUTO (see Guo et al 2013 for more details).…”

EVIDENCE FOR REDUCED SPECIFIC STAR FORMATION RATES IN THE CENTERS OF MASSIVE GALAXIES AT z = 4

“…K-band imaging on the GOODS-S field is available from the HAWK-I UDS and GOODS Survey (HUGS) (Fontana et al 2014). HUGS is the deepest K-band survey using the VLT/HAWK-I, and the final seeing is less than 0 43.…”