The HiZELS/UKIRT large area survey for bright Lyman-alpha emitters at z~9

We present the largest area survey to date (1.4 deg2) for Lyman-alpha emitters (LAEs) at z~9, as part of the Hi-z Emission Line Survey (HiZELS). The survey, which primarily targets H-alpha emitters at z < 3, uses the Wide Field CAMera on the United Kingdom Infrared Telescope and a custom narrow-band filter in the J band to reach a Lyman-alpha luminosity limit of ~10^43.8 erg/s over a co-moving volume of 1.12x10^6 Mpc^3 at z = 8.96+-0.06. Two candidates were found out of 1517 line emitters, but those were rejected as LAEs after follow-up observations. This improves the limit on the space density of bright Lyman-alpha emitters by 3 orders of magnitude and is consistent with suppression of the bright end of the Lyman-alpha luminosity function beyond z~6. Combined with upper limits from smaller but deeper surveys, this rules out some of the most extreme models for high-redshift Lyman-alpha emitters. The potential contamination of narrow-band Lyman-alpha surveys at z>7 by Galactic brown dwarf stars is also examined, leading to the conclusion that such contamination may well be significant for searches at 7.7 < z < 8.0, 9.1 < z < 9.5 and 11.7 < z < 12.2.Comment: To appear in proceedings of "UKIRT at 30: A British Success Story

A Submillimetre Survey of the Hubble Deep Field: Unveiling Dust-Enshrouded Star Formation in the Early Universe

The advent of sensitive sub-mm array cameras now allows a proper census of dust-enshrouded massive star-formation in very distant galaxies, previously hidden activity to which even the deepest optical images are insensitive. We present the deepest sub-mm survey, taken with the SCUBA camera on the James Clerk Maxwell Telescope (JCMT) and centred on the Hubble Deep Field (HDF). The high source density on this image implies that the survey is confusion-limited below a flux density of 2 mJy. However within the central 80 arcsec radius independent analyses yield 5 reproducible sources with S(850um) > 2 mJy which simulations indicate can be ascribed to individual galaxies. These data lead to integral source counts which are completely inconsistent with a no evolution model, whilst the combined brightness of the 5 most secure sources in our map is sufficient to account for 30-50% of the previously unresolved sub-mm background, and statistically the entire background is resolved at about the 0.3 mJy level. Four of the five brightest sources appear to be associated with galaxies which lie in the redshift range 2 < z < 4. With the caveat that this is a small sample of sources detected in a small survey area, these submm data imply a star-formation density over this redshift range that is at least five times higher than that inferred from the rest-frame ultraviolet output of HDF galaxies.Comment: to appear in the proceedings of `The Birth of Galaxies', Xth Rencontres de Blois, 4 pages, 1 postscript figure, uses blois.sty (included

Substrate selectivity of an isolated enoyl reductase catalytic domain from an iterative highly reducing fungal polyketide synthase reveals key components of programming

A cis-acting enoyl reductase (ER) catalytic domain was isolated from a fungal highly reducing iterative polyketide synthase (HR-iPKS) for the first time and studied in vitro. The ER from the squalestatin tetraketide synthase forms a discrete dimeric protein in solution. The ER shows broad substrate selectivity, reducing enoyl species including both natural and unnatural substrates. Pantetheine-bound substrate thiolesters reacted much faster than the corresponding SNAC thiolesters. The unnatural substrates included Z-olefins, 2-ethyl olefins and pentaketides. Methylation of the substrate modifies the activity of the ER such that the 2,4-dimethyl oct-2-enoyl substrate fits into the active site but cannot be reduced. A new NMR-based assay was developed for the direct observation of the stereochemical preferences at the 4′ position of the NADPH cofactor and the C-2 and C-3 positions of the substrates. The assay reveals that the fungal iPKS ER-catalysed reaction is stereochemically identical to that of the vertebrate FAS (vFAS) at the cofactor 4′ position and the substrate 3-position, but the high stereoselectivity displayed by intact SQTKS is lost such that reprotonation at the 2-position is unselective by the isolated ER. A 3D model of ER was consistent with these observations and showed that the ER may sequester its final substrate to prevent further chain extension. The results support a developing model for programming by HR-iPKS in which competition for substrates between restrictive and permissive catalytic domains chaperones the growing polyketide to completion, while allowing for errors and evolution

Unveiling Dust-enshrouded Star Formation in the Early Universe: a Sub-mm Survey of the Hubble Deep Field

The advent of sensitive sub-mm array cameras now allows a proper census of dust-enshrouded massive star-formation in very distant galaxies, previously hidden activity to which even the faintest optical images are insensitive. We present the deepest sub-mm survey of the sky to date, taken with the SCUBA camera on the James Clerk Maxwell Telescope and centred on the Hubble Deep Field. The high source density found in this image implies that the survey is confusion-limited below a flux density of 2 mJy. However, within the central 80 arcsec radius independent analyses yield 5 reproducible sources with S(850um) > 2 mJy which simulations indicate can be ascribed to individual galaxies. We give positions and flux densities for these, and furthermore show using multi-frequency photometric data that the brightest sources in our map lie at redshifts z~3. These results lead to integral source counts which are completely inconsistent with a no-evolution model, and imply that massive star-formation activity continues at redshifts > 2. The combined brightness of the 5 most secure sources in our map is sufficient to account for 30 - 50% of the previously unresolved sub-mm background, and we estimate statistically that the entire background is resolved at about the 0.3 mJy level. Finally we discuss possible optical identifications and redshift estimates for the brightest sources. One source appears to be associated with an extreme starburst galaxy at z~1, whilst the remaining four appear to lie in the redshift range 2 < z < 4. This implies a star-formation density over this redshift range that is at least five times higher than that inferred from the ultraviolet output of HDF galaxies.Comment: 19 pages, 6 figures (to appear as a Nature Article

HiZELS: the High Redshift Emission Line Survey with UKIRT

In these proceedings we report on HiZELS, the High-z Emission Line Survey, our successful panoramic narrow-band Campaign Survey using WFCAM on UKIRT to detect and study emission line galaxies at z~1-9. HiZELS employs the H2(S1) narrow-band filter together with custom-made narrow-band filters in the J and H-bands, with the primary aim of delivering large, identically-selected samples of H-alpha emitting galaxies at redshifts of 0.84, 1.47 and 2.23. Comparisons between the luminosity function, the host galaxy properties, the clustering, and the variation with environment of these H-alpha-selected samples are yielding unique constraints on the nature and evolution of star-forming galaxies, across the peak epoch of star-formation activity in the Universe. We provide a summary of the project status, and detail the main scientific results obtained so far: the measurement of the evolution of the cosmic star-formation rate density out to z > 2 using a single star-formation indicator, determination of the morphologies, environments and dust-content of the star-forming galaxies, and a detailed investigation of the evolution of their clustering properties. We also summarise the on-going work and future goals of the project.Comment: To appear in proceedings of "UKIRT at 30: A British Success Story"

Confirmation of the effectiveness of sub-mm source redshift estimation based on rest-frame radio to FIR photometry

We present a comparison between the published optical, IR and CO spectroscopic redshifts of 15 (sub-)mm galaxies and their photometric redshifts as derived from long-wavelength (radio-mm-FIR) photometric data. The redshift accuracy measured for 12 sub-mm galaxies with at least one robustly-determined colour in the radio-mm-FIR regime is dz=0.30 (r.m.s.). Despite the wide range of spectral energy distributions in the local galaxies that are used in an un-biased manner as templates, this analysis demonstrates that photometric redshifts can be efficiently derived for sub-mm galaxies with a precision of dz < 0.5 using only the rest-frame FIR to radio wavelength data.Comment: submitted to MNRAS (1 object removed from analysis, shortening of paper

Very compact millimeter sizes for composite star-forming/AGN submillimeter galaxies

We report the study of far-IR sizes of submillimeter galaxies (SMGs) in relation to their dust-obscured star formation rate (SFR) and active galactic nuclei (AGN) presence, determined using mid-IR photometry. We determined the millimeter-wave ($\lambda_{\rm obs}=1100 \mu$m) sizes of 69 ALMA-identified SMGs, selected with $\geq10$$\sigma$ confidence on ALMA images ($F_{\rm 1100 \mu m}=1.7$--7.4 mJy). We found that all the SMGs are located above an avoidance region in the millimeter size-flux plane, as expected by the Eddington limit for star formation. In order to understand what drives the different millimeter-wave sizes in SMGs, we investigated the relation between millimeter-wave size and AGN fraction for 25 of our SMGs at $z=1$--3. We found that the SMGs for which the mid-IR emission is dominated by star formation or AGN have extended millimeter-sizes, with respective median $R_{\rm c,e} = 1.6^{+0.34}_{-0.21}$ and 1.5$^{+0.93}_{-0.24}$ kpc. Instead, the SMGs for which the mid-IR emission corresponds to star-forming/AGN composites have more compact millimeter-wave sizes, with median $R_{\rm c,e}=1.0^{+0.20}_{-0.20}$ kpc. The relation between millimeter-wave size and AGN fraction suggests that this size may be related to the evolutionary stage of the SMG. The very compact sizes for composite star-forming/AGN systems could be explained by supermassive black holes growing rapidly during the SMG coalescing, star-formation phase.Comment: 9 pages, 4 figures, 1 table. Accepted for publication in ApJ Lette

SXDF-ALMA 2 Arcmin^2 Deep Survey: Resolving and Characterizing the Infrared Extragalactic Background Light Down to 0.5 mJy

We present a multi-wavelength analysis of five submillimeter sources (S_1.1mm = 0.54-2.02 mJy) that were detected during our 1.1-mm-deep continuum survey in the SXDF-UDS-CANDELS field (2 arcmin^2, 1sigma = 0.055 mJy beam^-1) using the Atacama Large Millimeter/submillimeter Array (ALMA). The two brightest sources correspond to a known single-dish (AzTEC) selected bright submillimeter galaxy (SMG), whereas the remaining three are faint SMGs newly uncovered by ALMA. If we exclude the two brightest sources, the contribution of the ALMA-detected faint SMGs to the infrared extragalactic background light is estimated to be ~ 4.1^{+5.4}_{-3.0} Jy deg^{-2}, which corresponds to ~ 16^{+22}_{-12}% of the infrared extragalactic background light. This suggests that their contribution to the infrared extragalactic background light is as large as that of bright SMGs. We identified multi-wavelength counterparts of the five ALMA sources. One of the sources (SXDF-ALMA3) is extremely faint in the optical to near-infrared region despite its infrared luminosity (L_IR ~ 1e12 L_sun or SFR ~ 100 M_sun yr^{-1}). By fitting the spectral energy distributions (SEDs) at the optical-to-near-infrared wavelengths of the remaining four ALMA sources, we obtained the photometric redshifts (z_photo) and stellar masses (M_*): z_photo ~ 1.3-2.5, M_* ~ (3.5-9.5)e10 M_sun. We also derived their star formation rates (SFRs) and specific SFRs (sSFRs) as ~ 30-200 M_sun yr^{-1} and ~ 0.8-2 Gyr^{-1}, respectively. These values imply that they are main-sequence star-forming galaxies.Comment: PASJ accepted, 15 pages, 6 figures, 2 table

Resolving debris discs in the far-infrared: early highlights from the DEBRIS survey

We present results from the earliest observations of DEBRIS, a Herschel Key Programme to conduct a volume- and flux-limited survey for debris discs in A-type through M-type stars. PACS images (from chop/nod or scan-mode observations) at 100 and 160 micron are presented toward two A-type stars and one F-type star: beta Leo, beta UMa and eta Corvi. All three stars are known disc hosts. Herschel spatially resolves the dust emission around all three stars (marginally, in the case of beta UMa), providing new information about discs as close as 11 pc with sizes comparable to that of the Solar System. We have combined these data with existing flux density measurements of the discs to refine the SEDs and derive estimates of the fractional luminosities, temperatures and radii of the discs.Comment: to be published in A&A, 5 pages, 2 color figure

SXDF-ALMA 1.5 arcmin^2 deep survey. A compact dusty star-forming galaxy at z=2.5

We present first results from the SXDF-ALMA 1.5 arcmin^2 deep survey at 1.1 mm using Atacama Large Millimeter Array (ALMA). The map reaches a 1sigma depth of 55 uJy/beam and covers 12 Halpha-selected star-forming galaxies at z = 2.19 or z=2.53. We have detected continuum emission from three of our Halpha-selected sample, including one compact star-forming galaxy with high stellar surface density, NB2315-07. They are all red in the rest-frame optical and have stellar masses of log (M*/Msun)>10.9 whereas the other blue, main-sequence galaxies with log(M*/Msun)=10.0-10.8 are exceedingly faint, <290 uJy (2sigma upper limit). We also find the 1.1 mm-brightest galaxy, NB2315-02, to be associated with a compact (R_e=0.7+-0.1 kpc), dusty star-forming component. Given high gas fraction (44^{+20}_{-8}% or 37^{+25}_{-3}%) and high star formation rate surface density (126^{+27}_{-30} Msun yr^{-1}kpc^{-2}), the concentrated starburst can within less than 50^{+12}_{-11} Myr build up a stellar surface density matching that of massive compact galaxies at z~2, provided at least 19+-3% of the total gas is converted into stars in the galaxy centre. On the other hand, NB2315-07, which already has such a high stellar surface density core, shows a gas fraction (23+-8%) and is located in the lower envelope of the star formation main-sequence. This compact less star-forming galaxy is likely to be in an intermediate phase between compact dusty star-forming and quiescent galaxies.Comment: 6 pages, 4 figures, 1 table, accepted for publication in ApJ