The multiwavelength Survey by Yale-Chile (MUSYC): Deep medium-band optical imaging and high-quality 32-band photometric redshifts in the ECDF-S

We present deep optical 18-medium-band photometry from the Subaru telescope over the ∼30′ × 30′ Extended Chandra Deep Field-South, as part of the Multiwav elength Survey by Yale-Chile (MUSYC). This field has a wealth of ground- and space-based ancillary data, and contains the GOODS-South field and the Hubble Ultra Deep Field. We combine the Subaru imaging with existing UBVRIzJHK and Spitzer IRAC images to create a uniform catalog. Detecting sources in the MUSYC "BVR" image we find ∼40,000 galaxies with RAB < 25.3, the median 5σ limit of the 18 medium bands. Photometric redshifts are determined using the EAzY code and compared to ∼2000 spectroscopic red shifts in this field. The medium-band filters provide very accurate redshifts for the (bright) subset of galaxies with spectroscopic red shifts, particularly at 0.1 < z < 1.2 and at z ≳ 3.5. For 0.1 < z < 1.2, we find a 1σ scatter in Δz/(1 + z) of 0.007, similar to results obtained with a similar filter set in the COSMOS field. As a demonstration of the data quality, we show that the red sequence and blue cloud can be cleanly identified in rest-frame color-magnitude diagrams at 0.1 < z < 1.2. We find that ∼20% of the red sequence galaxies show evidence of dust emission at longer rest-frame wavelengths. The reduced images, photometric catalog, and photometric redshifts are provided through the public MUSYCWeb site.