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Register a new userHerMES: SPIRE Science Demonstration Phase Maps
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We describe the production and verification of sky maps of the five SPIRE fields observed as part of the Herschel Multi-tiered Extragalactic Survey (HerMES) during the Science Demonstration Phase (SDP) of the Herschel mission. We have implemented an iterative map-making algorithm (SHIM; The SPIRE-HerMES Iterative Mapper) to produce high fidelity maps that preserve extended diffuse emission on the sky while exploiting the repeated observations of the same region of the sky with many detectors in multiple scan directions to minimize residual instrument noise. We specify here the SHIM algorithm and outline the various tests that were performed to determine and characterize the quality of the maps and verify that the astrometry, point source flux and power on all relevant angular scales meets the needs of the HerMES science goals. These include multiple jackknife tests, determination of the map transfer function and detailed examination of the power spectra of both sky and jackknife maps. The map transfer function is approximately unity on scales from one arcminute to one degree. Final maps (v1.0), including multiple jackknives, as well as the SHIM pipeline, have been used by the HerMES team for the production of SDP papers.
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Dusty, star forming galaxies contribute to a bright, currently unresolved cosmic far-infrared background. Deep Herschel-SPIRE images designed to detect and characterize the galaxies that comprise this background are highly confused, such that the bulk lies below the classical confusion limit. We analyze three fields from the HerMES programme in all three SPIRE bands (250, 350, and 500 microns); parameterized galaxy number count models are derived to a depth of ~2 mJy/beam, approximately 4 times the depth of previous analyses at these wavelengths, using a P(D) (probability of deflection) approach for comparison to theoretical number count models. Our fits account for 64, 60, and 43 per cent of the far-infrared background in the three bands. The number counts are consistent with those based on individually detected SPIRE sources, but generally inconsistent with most galaxy number counts models, which generically overpredict the number of bright galaxies and are not as steep as the P(D)-derived number counts. Clear evidence is found for a break in the slope of the differential number counts at low flux densities. Systematic effects in the P(D) analysis are explored. We find that the effects of clustering have a small impact on the data, and the largest identified systematic error arises from uncertainties in the SPIRE beam.
We report on the sensitivity of SPIRE photometers on the Herschel Space Observatory. Specifically, we measure the confusion noise from observations taken during the Science Demonstration Phase of the Herschel Multi-tiered Extragalactic Survey. Confusion noise is defined to be the spatial variation of the sky intensity in the limit of infinite integration time, and is found to be consistent among the different fields in our survey at the level of 5.8, 6.3 and 6.8 mJy/beam at 250, 350 and 500 microns, respectively. These results, together with the measured instrument noise, may be used to estimate the integration time required for confusion-limited maps, and provide a noise estimate for maps obtained by SPIRE.
Local luminosity functions are fundamental benchmarks for high-redshift galaxy formation and evolution studies as well as for models describing these processes. Determining the local luminosity function in the submillimeter range can help to better constrain in particular the bolometric luminosity density in the local Universe, and Herschel offers the first opportunity to do so in an unbiased way by imaging large sky areas at several submillimeter wavelengths. We present the first Herschel measurement of the submillimeter 0<z<0.2 local luminosity function and infrared bolometric (8-1000 $mu$m) local luminosity density based on SPIRE data from the HerMES Herschel Key Program over 14.7 deg^2. Flux measurements in the three SPIRE channels at 250, 350 and 500 mum are combined with Spitzer photometry and archival data. We fit the observed optical-to-submillimeter spectral energy distribution of SPIRE sources and use the 1/V_{max} estimator to provide the first constraints on the monochromatic 250, 350 and 500 mum as well as on the infrared bolometric (8-1000 mum) local luminosity function based on Herschel data. We compare our results with modeling predictions and find a slightly more abundant local submillimeter population than predicted by a number of models. Our measurement of the infrared bolometric (8-1000 mum) local luminosity function suggests a flat slope at low luminosity, and the inferred local luminosity density, 1.31_-0.21^+0.24 x 10^8 Lsun Mpc^-3, is consistent with the range of values reported in recent literature.
The Herschel Multi-tiered Extragalactic Survey (HerMES) is the largest Guaranteed Time Key Programme on the Herschel Space Observatory. With a wedding cake survey strategy, it consists of nested fields with varying depth and area totalling ~380 deg^2. In this paper, we present deep point source catalogues extracted from Herschel-SPIRE observations of all HerMES fields, except for the later addition of the 270 deg^2 HeLMS field. These catalogues constitute the second Data Release (DR2) made in October 2013. A subset of these catalogues, which consists of bright sources extracted from Herschel-SPIRE observations completed by May 1, 2010 (covering ~ 74 deg^2) were released earlier in the first extensive Data Release (DR1) in March 2012. Two different methods are used to generate the point source catalogues, the SUSSEXtractor (SXT) point source extractor used in two earlier data releases (EDR and EDR2) and a new source detection and photometry method. The latter combines an iterative source detection algorithm, StarFinder (SF), and a De-blended SPIRE Photometry (DESPHOT) algorithm. We use end-to-end Herschel-SPIRE simulations with realistic number counts and clustering properties to characterise basic properties of the point source catalogues, such as the completeness, reliability, photometric and positional accuracy. Over 500, 000 catalogue entries in HerMES fields (except HeLMS) are released to the public through the HeDAM website (http://hedam.oamp.fr/herMES).
We present first results of a study of the submillimetre (rest frame far-infrared) properties of z~3 Lyman Break Galaxies (LBGs) and their lower-redshift counterparts BX/BM galaxies, based on Herschel-SPIRE observations of the Northern field of the Great Observatories Origins Deep Survey (GOODS-N). We use stacking analysis to determine the properties of LBGs well below the current limit of the survey. Although LBGs are not detected individually, stacking the infrared luminous LBGs (those detected with Spitzer at 24 microns yields a statistically significant submm detection with mean flux <S_{250}>= 5.9+/-1.4 mJy confirming the power of SPIRE in detecting UV-selected high-redshift galaxies at submillimetre wavelengths. In comparison, the Spitzer 24 microns detected BX/BM galaxies appear fainter with a stacked value of <S_{250}> = 2.7 +/-0.8 mJy. By fitting the Spectral Energy Distributions (SEDs) we derive median infrared luminosities, L_{IR}, of 2.8x10^{12} Lsun and 1.5x10^{11} Lsun for z~3 LBGs and BX/BMs, respectively. We find that $L_{IR} estimates derived from present measurements are in good agreement with those based on UV data for z~2 BX/BM galaxies, unlike the case for z~3 infrared luminous LBGs where the UV underestimates the true $L_{IR}. Although sample selection effects may influence this result we suggest that differences in physical properties (such as morphologies, dust distribution and extent of star-forming regions) between z ~3 LBGs and z~2 BX/BMs may also play a significant role.
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