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GOODS 850-5 is a hyperluminous radio-faint submillimeter source in the GOODS-N. Although it is generally agreed that GOODS 850-5 is at a high redshift z>~4, its exact redshift is unknown. While its stellar SED suggests z~6, its radio/FIR SED suggests a lower redshift of z~4. To better constrain its stellar SED and redshift, we carried out nano-Jansky sensitivity ultradeep NIR observations between 1.2 and 2.1 um with the HST and the 8 m Subaru Telescope. Even with such great depths we did not detect GOODS 850-5, and the results show that it is an extremely curious source. Between the Ks and 3.6 um bands its spectral slope is >3x that of an ERO, and the flux ratio between the two bands is >8x that of Lyman breaks. It is quite challenging to explain this unusually red color without a Lyman break (which would imply z>17). It requires a large amount (M* ~ 10^11.5 Msun) of reddened old stars at z~6, coexisting with an even more extinguished violent ~2400-4400 Msun/yr starburst, which does not have any associated detectable rest-frame UV radiation. We discuss the discrepancy between the NIR and radio/FIR photometric redshifts. We conclude that GOODS 850-5 is at least at z>4 and is more likely at z>~6. We describe the unusual properties of GOODS 850-5, including its SED and formation history, and we discuss the implications of such massive z>6 galaxies.
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We report an SMA interferometric identification of a bright submillimeter source, GOODS 850-5. This source is one of the brightest 850 um sources in the GOODS-N but is extremely faint at all other wavelengths. It is not detected in the GOODS HST ACS images and only shows a weak 2 sigma signal at 1.4 GHz. It is detected in the Spitzer IRAC bands and the MIPS 24 um band, however, with very low fluxes. We present evidence in the radio, submillimeter, mid-IR, near-IR, and optical that suggest GOODS 850-5 may be a z>4 galaxy.
We present deep near-infrared (NIR) Js, H, and Ks-band ISAAC imaging of the WFPC2 field of the HDF-S. The 2.5x 2.5 high Galactic latitude field was observed with the VLT under the best seeing conditions with integration times amounting to 33.6 hours in Js, 32.3 hours in H, and 35.6 hours in Ks. We reach total AB magnitudes for point sources of 26.8, 26.2, and 26.2 respectively (3 sigma), which make it the deepest ground-based NIR observations to date, and the deepest Ks-band data in any field. The effective seeing of the coadded images is ~0.45 in Js, ~0.48 in H, and ~0.46 in Ks. Using published WFPC2 optical data, we constructed a Ks-limited multicolor catalog containing 833 sources down to Ks,tot ~< 26 (AB), of which 624 have seven-band optical-to-NIR photometry. These data allow us to select normal galaxies from their rest-frame optical properties to high redshift (z ~< 4). The observations, data reduction and properties of the final images are discussed, and we address the detection and photometry procedures that were used in making the catalog. In addition, we present deep number counts, color distributions and photometric redshifts of the HDF-S galaxies. We find that our faint Ks-band number counts are flatter than published counts in other deep fields, which might reflect cosmic variations or different analysis techniques. Compared to the HDF-N, we find many galaxies with very red V-H colors at photometric redshifts 1.95 < z < 3.5. These galaxies are bright in Ks with infrared colors redder than Js-Ks > 2.3 (in Johnson magnitudes). Because they are extremely faint in the observed optical, they would be missed by ultraviolet-optical selection techniques, such as the U-dropout method.
We present an ultradeep Ks-band image that covers 0.5*0.5 deg^2 centered on the Great Observatories Origins Deep Survey-North (GOODS-N). The image reaches a 5 sigma depth of Ks(AB) = 24.45 in the GOODS-N region, which is as deep as the GOODS-N Spitzer Infrared Array Camera (IRAC) 3.6 mu m image. We present a new method of constructing IRAC catalogs that uses the higher spatial resolution Ks image and catalog as priors and iteratively subtracts fluxes from the IRAC images to estimate the IRAC fluxes. Our iterative method is different from the chi^2 approach adopted by other groups. We verified our results using data taken in two different epochs of observations, as well as by comparing our colors with the colors of stars and with the colors derived from model spectral energy distributions (SEDs) of galaxies at various redshifts. We make available to the community our WIRCam Ks-band image and catalog (94951 objects in 0.25 deg^2), the Interactive Data Language (IDL) pipeline used for reducing the WIRCam images, and our IRAC 3.6 to 8.0 mu m catalog (16950 objects in 0.06 deg^2 at 3.6 mu m). With this improved Ks and IRAC catalog and a large spectroscopic sample from our previous work, we study the color-magnitude and color-color diagrams of galaxies. We compare the effectiveness of using Ks and IRAC colors to select active galactic nuclei (AGNs) and galaxies at various redshifts. We also study a color selection of z = 0.65--1.2 galaxies using the Ks, 3.6 mu m, and 4.5 mu m bands.
We present sensitive phase-referenced VLBI results on the radio continuum emission from the z=1.87 luminous submillimeter galaxy (SMG) GOODS 850-3. The observations were carried out at 1.4 GHz using the High Sensitivity Array (HSA). Our sensitive tapered VLBI image of GOODS 850-3 at 0.47 x 0.34 arcsec (3.9 x 2.9 kpc) resolution shows a marginally resolved continuum structure with a peak flux density of 148 pm 38 uJy/beam, and a total flux density of 168 pm 73 uJy, consistent with previous VLA and MERLIN measurements. The derived intrinsic brightness temperature is > 5 pm 2 x 10^3 K. The radio continuum position of this galaxy coincides with a bright and extended near-infrared source that nearly disappears in the deep HST optical image, indicating a dusty source of nearly 9 kpc in diameter. No continuum emission is detected at the full VLBI resolution (13.2 x 7.2 mas, 111 x 61 pc), with a 4-sigma point source upper limit of 26 uJy/beam, or an upper limit to the intrinsic brightness temperature of 4.7 x 10^5 K. The extent of the observed continuum source at 1.4 GHz and the derived brightness temperature limits are consistent with the radio emission (and thus presumably the far-infrared emission) being powered by a major starburst in GOODS 850-3, with a star formation rate of ~2500 M_sun/yr. Moreover, the absence of any continuum emission at the full resolution of the VLBI observations indicates the lack of a compact radio AGN source in this z=1.87 SMG.
In this first paper in the SUPER GOODS series on powerfully star-forming galaxies in the two GOODS fields, we present a deep SCUBA-2 survey of the GOODS-N at both 850 and 450 micron (central rms noise of 0.28 mJy and 2.6 mJy, respectively). In the central region the 850 micron observations cover the GOODS-N to near the confusion limit of ~1.65 mJy, while over a wider 450 arcmin^2 region---well complemented by Herschel far-infrared imaging---they have a median 4-sigma limit of 3.5 mJy. We present >4-sigma catalogs of 186 850 micron and 31 450 micron selected sources. We use interferometric observations from the SMA and the VLA to obtain precise positions for 114 SCUBA-2 sources (28 from the SMA, all of which are also VLA sources). We present new spectroscopic redshifts and include all existing spectroscopic or photometric redshifts. We also compare redshifts estimated using the 20 cm to 850 micron and the 250 micron to 850 micron flux ratios. We show that the redshift distribution increases with increasing flux, and we parameterize the dependence. We compute the star formation history and the star formation rate (SFR) density distribution functions in various redshift intervals, finding that they reach a peak at z=2-3 before dropping to higher redshifts. We show that the number density per unit volume of SFR>500 solar mass per year galaxies measured from the SCUBA-2 sample does not change much relative to that of lower SFR galaxies from UV selected samples over z=2-5, suggesting that, apart from changes in the normalization, the shape in the number density as a function of SFR is invariant over this redshift interval.
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