-
HerMES Collaboration,
S. J. Oliver,
J. Bock,
B. Altieri,
A. Amblard,
V. Arumugam,
H. Aussel,
T. Babbedge,
A. Beelen,
M. Béthermin, [......],
I. Valtchanov,
J. D. Vieira,
M. Viero,
L. Vigroux,
L. Wang, R. Ward,
J. Wardlow,
G. Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: The Herschel Multi-tiered Extragalactic Survey, HerMES, is a legacy program
designed to map a set of nested fields totalling ~380 deg^2. Fields range in
size from 0.01 to ~20 deg^2, using Herschel-SPIRE (at 250, 350 and 500 \mu m),
and Herschel-PACS (at 100 and 160 \mu m), with an additional wider component of
270 deg^2 with SPIRE alone. These bands cover the peak of the redshifted
thermal spectral energy distribution from interstellar dust and thus capture
the re-processed optical and ultra-violet radiation from star formation that
has been absorbed by dust, and are critical for forming a complete
multi-wavelength understanding of galaxy formation and evolution.
The survey will detect of order 100,000 galaxies at 5\sigma in some of the
best studied fields in the sky. Additionally, HerMES is closely coordinated
with the PACS Evolutionary Probe survey. Making maximum use of the full
spectrum of ancillary data, from radio to X-ray wavelengths, it is designed to:
facilitate redshift determination; rapidly identify unusual objects; and
understand the relationships between thermal emission from dust and other
processes. Scientific questions HerMES will be used to answer include: the
total infrared emission of galaxies; the evolution of the luminosity function;
the clustering properties of dusty galaxies; and the properties of populations
of galaxies which lie below the confusion limit through lensing and statistical
techniques.
This paper defines the survey observations and data products, outlines the
primary scientific goals of the HerMES team, and reviews some of the early
results.
03/2012;
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M J Page,
M Symeonidis,
J D Vieira,
B Altieri,
A Amblard,
V Arumugam,
H Aussel,
T Babbedge,
A Blain,
J Bock, [......],
K E Tugwell,
M Vaccari,
I Valtchanov,
M Viero,
L Vigroux,
L Wang, R Ward,
G Wright,
C K Xu,
M Zemcov
[show abstract]
[hide abstract]
ABSTRACT: The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expelling the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time.
Nature 01/2012; 485(7397):213-6. · 36.28 Impact Factor
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A J Smith,
L Wang,
S. J. Oliver,
R. Auld,
J. Bock,
D. Brisbin,
D. Burgarella,
P. Chanial,
E. Chapin,
D. L. Clements, [......],
Douglas Scott,
N. Seymour,
M. Symeonidis,
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
L. Vigroux, R Ward,
G Wright,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: We describe the generation of single-band point source catalogues from
submillimetre Herschel-SPIRE observations taken as part of the Science
Demonstration Phase of the Herschel Multi-tiered Extragalactic Survey (HerMES).
Flux densities are found by means of peak-finding and the fitting of a Gaussian
point-response function. With highly-confused images, careful checks must be
made on the completeness and flux density accuracy of the detected sources.
This is done by injecting artificial sources into the images and analysing the
resulting catalogues. Measured flux densities at which 50 per cent of injected
sources result in good detections at (250, 350, 500) {\mu}m range from (11.6,
13.2, 13.1) mJy to (25.7, 27.1, 35.8) mJy, depending on the depth of the
observation (where a `good' detection is taken to be one with positional offset
less than one full-width half-maximum of the point-response function, and with
the measured flux density within a factor of 2 of the flux density of the
injected source). This paper acts as a reference for the 2010 July HerMES
public data release.
09/2011;
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M Rowan-Robinson,
I ~G Roseboom,
M Vaccari,
A Amblard,
V Arumugam,
R Auld,
H Aussel,
T Babbedge,
A Blain,
J Bock, [......],
M Symeonidis,
M Trichas,
K ~E Tugwell,
I Valtchanov,
L Vigroux,
L Wang, R Ward,
G Wright,
C ~K Xu,
M Zemcov
VizieR Online Data Catalog. 08/2011; 740:90002.
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Alexandre Amblard,
Asantha Cooray,
Paolo Serra,
B Altieri,
V Arumugam,
H Aussel,
A Blain,
J Bock,
A Boselli,
V Buat, [......],
M Vaccari,
E Valiante,
I Valtchanov,
J D Vieira,
L Vigroux,
L Wang, R Ward,
G Wright,
C K Xu,
M Zemcov
[show abstract]
[hide abstract]
ABSTRACT: The extragalactic background light at far-infrared wavelengths comes from optically faint, dusty, star-forming galaxies in the Universe with star formation rates of a few hundred solar masses per year. These faint, submillimetre galaxies are challenging to study individually because of the relatively poor spatial resolution of far-infrared telescopes. Instead, their average properties can be studied using statistics such as the angular power spectrum of the background intensity variations. A previous attempt at measuring this power spectrum resulted in the suggestion that the clustering amplitude is below the level computed with a simple ansatz based on a halo model. Here we report excess clustering over the linear prediction at arcminute angular scales in the power spectrum of brightness fluctuations at 250, 350 and 500 μm. From this excess, we find that submillimetre galaxies are located in dark matter haloes with a minimum mass, M(min), such that log(10)[M(min)/M(⊙)] = 11.5(+0.7)(-0.2) at 350 μm, where M(⊙) is the solar mass. This minimum dark matter halo mass corresponds to the most efficient mass scale for star formation in the Universe, and is lower than that predicted by semi-analytical models for galaxy formation.
Nature 02/2011; 470(7335):510-2. · 36.28 Impact Factor
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M. Rowan-Robinson,
I. G. Roseboom,
M. Vaccari,
A. Amblard,
V. Arumugam,
R. Auld,
H. Aussel,
T. Babbedge,
A. Blain,
J. Bock, [......],
M. Symeonidis,
M. Trichas,
K. E. Tugwell,
I. Valtchanov,
L. Vigroux,
L. Wang, R. Ward,
G. Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: We present spectral energy distributions (SEDs) for 68 Herschel sources detected at 5σ at 250, 350 and 500 μm in the HerMES SWIRE-Lockman field. We explore whether existing models for starbursts, quiescent star-forming galaxies and active galactic nucleus dust tori are able to model the full range of SEDs measured with Herschel. We find that while many galaxies (∼56 per cent) are well fitted with the templates used to fit IRAS, Infrared Space Observatory (ISO) and Spitzer sources, for about half the galaxies two new templates are required: quiescent (‘cirrus’) models with colder (10–20 K) dust and a young starburst model with higher optical depth than Arp 220. Predictions of submillimetre fluxes based on model fits to 4.5–24 μm data agree rather poorly with the observed fluxes, but the agreement is better for fits to 4.5–70 μm data. Herschel galaxies detected at 500 μm tend to be those with the highest dust masses.
Monthly Notices of the Royal Astronomical Society 11/2010; 409(1):2 - 11. · 4.90 Impact Factor
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D. Brisbin,
M. Harwit,
B. Altieri,
A. Amblard,
V. Arumugam,
H. Aussel,
T. Babbedge,
A. Blain,
J. Bock,
A. Boselli, [......],
M. Trichas,
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
L. Vigroux,
L. Wang, R. Ward,
G. Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: The Spectral and Photometric Imaging Receiver on-board Herschel has been carrying out deep extragalactic surveys, one of the aims of which is to establish spectral energy distributions of individual galaxies spanning the infrared/submillimetre (IR/SMM) wavelength region. We report observations of the IR/SMM emission from the Lockman North field and Great Observatories Origins Deep Survey Field-North. Because galaxy images in the wavelength range covered by Herschel generally represent a blend with contributions from neighbouring galaxies, we present sets of galaxies in each field, especially free of blending at 250, 350 and 500 μm. We identify the cumulative emission of these galaxies and the fraction of the FIR cosmic background radiation they contribute. Our surveys reveal a number of highly luminous galaxies at redshift z≲ 3 and a novel relationship between IR and visible emission that shows a dependence on luminosity and redshift.
Monthly Notices of the Royal Astronomical Society 11/2010; 409(1):66 - 74. · 4.90 Impact Factor
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H. S. Hwang,
D. Elbaz,
G. Magdis,
E. Daddi,
M. Symeonidis,
B. Altieri,
A. Amblard,
P. Andreani,
V. Arumugam,
R. Auld, [......],
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
J. D. Vieira,
L. Vigroux,
L. Wang, R. Ward,
G. Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: We study the dust properties of galaxies in the redshift range 0.1 ≲z≲ 2.8 observed by the Herschel Space Observatory in the field of the Great Observatories Origins Deep Survey-North as part of the PACS Extragalactic Probe (PEP) and Herschel Multi-tiered Extragalactic Survey (HerMES) key programmes. Infrared (IR) luminosity (LIR) and dust temperature (Tdust) of galaxies are derived from the spectral energy distribution fit of the far-IR (FIR) flux densities obtained with the PACS and SPIRE instruments onboard Herschel. As a reference sample, we also obtain IR luminosities and dust temperatures of local galaxies at z < 0.1 using AKARI and IRAS data in the field of the Sloan Digital Sky Survey. We compare the LIR–Tdust relation between the two samples and find that the median Tdust of Herschel-selected galaxies at z≳ 0.5 with LIR≳ 5 × 1010 L⊙ appears to be 2–5 K colder than that of AKARI-selected local galaxies with similar luminosities, and the dispersion in Tdust for high-z galaxies increases with LIR due to the existence of cold galaxies that are not seen among local galaxies. We show that this large dispersion of the LIR−Tdust relation can bridge the gap between local star-forming galaxies and high-z submillimetre galaxies (SMGs). We also find that three SMGs with very low Tdust (≲20 K) covered in this study have close neighbouring sources with similar 24-μm brightness, which could lead to an overestimation of FIR/(sub)millimetre fluxes of the SMGs.
Monthly Notices of the Royal Astronomical Society 11/2010; 409(1):75 - 82. · 4.90 Impact Factor
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J. Glenn,
A. Conley,
M. Bethermin,
B. Altieri,
A. Amblard,
V. Arumugam,
H. Aussel,
T. Babbedge,
A. Blain,
J. Bock, [......],
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
J. D. Vieira,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: 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. Comment: Accepted for publication in MNRAS
09/2010;
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I. G. Roseboom,
S. J. Oliver,
M. Kunz,
B. Altieri,
A. Amblard,
V. Arumugam,
R. Auld,
H. Aussel,
T. Babbedge,
M. Béthermin, [......],
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
J. D. Vieira,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: We present the cross-identification and source photometry techniques used to process Herschel SPIRE imaging taken as part of the Herschel Multi-Tiered Extragalactic Survey (HerMES). Cross-identifications are performed in map-space so as to minimise source blending effects. We make use of a combination of linear inversion and model selection techniques to produce reliable cross-identification catalogues based on Spitzer MIPS 24 micron source positions. Testing on simulations and real Herschel observations show that this approach gives robust results for even the faintest sources S250~10 mJy. We apply our new technique to HerMES SPIRE observations taken as part of the science demostration phase of Herschel. For our real SPIRE observations we show that, for bright unconfused sources, our flux density estimates are in good agreement with those produced via more traditional point source detection methods (SussExtractor; Savage & Oliver et al. 2006) by Smith et al. 2010. When compared to the measured number density of sources in the SPIRE bands, we show that our method allows the recovery of a larger fraction of faint sources than these traditional methods. However this completeness is heavily dependant on the relative depth of the existing 24 micron catalogues and SPIRE imaging. Using our deepest multi-wavelength dataset in GOODS-N, we estimate that the use of shallow 24 micron in our other fields introduces an incompleteness at faint levels of between 20-40 per cent at 250 micron. Comment: Accepted for publication in MNRAS, 19 pages, 11 figures
09/2010;
-
H. S. Hwang,
D. Elbaz,
G. E. Magdis,
E. Daddi,
M. Symeonidis,
B. Altieri,
A. Amblard,
P. Andreani,
V. Arumugam,
R. Auld, [......],
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
J. D. Vieira,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: We study the dust properties of galaxies in the redshift range 0.1<z<2.8 observed by the Herschel Space Observatory in the field of the Great Observatories Origins Deep Survey-North as part of PEP and HerMES key programmes. Infrared (IR) luminosity (L_IR) and dust temperature (T_dust) of galaxies are derived from the spectral energy distribution (SED) fit of the far-infrared (FIR) flux densities obtained with PACS and SPIRE instruments onboard Herschel. As a reference sample, we also obtain IR luminosities and dust temperatures of local galaxies at z<0.1 using AKARI and IRAS data in the field of the Sloan Digital Sky Survey. We compare the L_IR-T_dust relation between the two samples and find that: the median T_dust of Herschel-selected galaxies at z>0.5 with L_IR>5x10^{10} L_\odot, appears to be 2-5 K colder than that of AKARI-selected local galaxies with similar luminosities; and the dispersion in T_dust for high-z galaxies increases with L_IR due to the existence of cold galaxies that are not seen among local galaxies. We show that this large dispersion of the L_IR-T_dust relation can bridge the gap between local star-forming galaxies and high-z submillimeter galaxies (SMGs). We also find that three SMGs with very low T_dust (<20 K) covered in this study have close neighbouring sources with similar 24-\mum brightness, which could lead to an overestimation of FIR/(sub)millimeter fluxes of the SMGs. Comment: 9 pages, 6 figures, To appear in MNRAS
09/2010;
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V. Buat,
E. Giovannoli,
D. Burgarella,
B. Altieri,
A. Amblard,
V. Arumugam,
H. Aussel,
T. Babbedge,
A. Blain,
J. Bock, [......],
K. E. Tugwell,
M. Vaccari,
E. Valiante,
I. Valtchanov,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: The reliability of infrared (IR) and ultraviolet (UV) emissions to measure star formation rates in galaxies is investigated for a large sample of galaxies observed with the SPIRE and PACS instruments on Herschel as part of the HerMES project. We build flux-limited 250 micron samples of sources at redshift z<1, cross-matched with the Spitzer/MIPS and GALEX catalogues. About 60 % of the Herschel sources are detected in UV. The total IR luminosities, L_IR, of the sources are estimated using a SED-fitting code that fits to fluxes between 24 and 500 micron. Dust attenuation is discussed on the basis of commonly-used diagnostics: the L_IR/L_UV ratio and the slope, beta, of the UV continuum. A mean dust attenuation A_UV of ~ 3 mag is measured in the samples. L_IR/L_UV is found to correlate with L_IR. Galaxies with L_IR > 10 ^{11} L_sun and 0.5< z<1 exhibit a mean dust attenuation A_UV about 0.7 mag lower than that found for their local counterparts, although with a large dispersion. Our galaxy samples span a large range of beta and L_IR/L_UV values which, for the most part, are distributed between the ranges defined by the relations found locally for starburst and normal star-forming galaxies. As a consequence the recipe commonly applied to local starbursts is found to overestimate the dust attenuation correction in our galaxy sample by a factor ~2-3 . Comment: accepted for publication in MNRAS, Herschel special issue
07/2010;
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M. J. Griffin,
A. Abergel,
A. Abreu,
P. A. R. Ade,
P. André,
J. L. Augueres,
T. Babbedge,
Y. Bae,
T. Baillie,
J.-P. Baluteau, [......],
N. Whitehouse,
C. D. Wilson,
B. Winter,
A. L. Woodcraft,
G. S. Wright,
C. K. Xu,
A. Zavagno,
M. Zemcov,
L Zhang,
E. Zonca
[show abstract]
[hide abstract]
ABSTRACT: The Spectral and Photometric Imaging Receiver (SPIRE), is the Herschel Space Observatory`s submillimetre camera and spectrometer. It contains a three-band imaging photometer operating at 250, 350 and 500 microns, and an imaging Fourier Transform Spectrometer (FTS) which covers simultaneously its whole operating range of 194-671 microns (447-1550 GHz). The SPIRE detectors are arrays of feedhorn-coupled bolometers cooled to 0.3 K. The photometer has a field of view of 4' x 8', observed simultaneously in the three spectral bands. Its main operating mode is scan-mapping, whereby the field of view is scanned across the sky to achieve full spatial sampling and to cover large areas if desired. The spectrometer has an approximately circular field of view with a diameter of 2.6'. The spectral resolution can be adjusted between 1.2 and 25 GHz by changing the stroke length of the FTS scan mirror. Its main operating mode involves a fixed telescope pointing with multiple scans of the FTS mirror to acquire spectral data. For extended source measurements, multiple position offsets are implemented by means of an internal beam steering mirror to achieve the desired spatial sampling and by rastering of the telescope pointing to map areas larger than the field of view. The SPIRE instrument consists of a cold focal plane unit located inside the Herschel cryostat and warm electronics units, located on the spacecraft Service Module, for instrument control and data handling. Science data are transmitted to Earth with no on-board data compression, and processed by automatic pipelines to produce calibrated science products. The in-flight performance of the instrument matches or exceeds predictions based on pre-launch testing and modelling: the photometer sensitivity is comparable to or slightly better than estimated pre-launch, and the spectrometer sensitivity is also better by a factor of 1.5-2. Comment: Accepted for publication in Astronomy & Astrophyics (Herschel first results special issue)
05/2010;
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D. Elbaz,
H. S. Hwang,
B. Magnelli,
E. Daddi,
H. Aussel,
B. Altieri,
A. Amblard,
P. Andreani,
V. Arumugam,
R. Auld, [......],
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
J. Vieira,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: The Herschel Space Observatory enables us to accurately measure the bolometric output of starburst galaxies and active galactic nuclei (AGN) by directly sampling the peak of their far-infrared (IR) emission. Here we examine whether the spectral energy distribution (SED) and dust temperature of galaxies have strongly evolved since z~2.5. We use Herschel deep extragalactic surveys from 100 to 500um to compute total IR luminosities in galaxies down to the faintest levels, using PACS and SPIRE in the GOODS-North field (PEP and HerMES key programs). We show that measurements in the SPIRE bands can be used below the statistical confusion limit if information at higher spatial resolution is used to identify isolated galaxies whose flux is not boosted by bright neighbors. Below z~1.5, mid-IR extrapolations are correct for star-forming galaxies with a dispersion of only 40% (0.15dex), therefore similar to z~0 galaxies. This narrow distribution is puzzling when considering the range of physical processes that could have affected the SED of these galaxies. Extrapolations from only one of the 160um, 250um or 350um bands alone tend to overestimate the total IR luminosity. This may be explained by the lack of far-IR constraints around and above ~150um (rest-frame) on local templates. We also note that the dust temperature of luminous IR galaxies around z~1 is mildly colder by 10-15% than their local analogs and up to 20% for ULIRGs at z~1.6. Above z=1.5, distant galaxies are found to exhibit a substantially larger mid- over far-IR ratio, which could either result from stronger broad emission lines or warm dust continuum heated by a hidden AGN. Two thirds of the AGNs identified in the field with a measured redshift exhibit the same behavior as purely star-forming galaxies. Hence a large fraction of AGNs harbor star formation at very high SFR and in conditions similar to purely star-forming galaxies. Comment: Astronomy and Astrophysics, Herschel Special Issue, in press as a Letter; 5 pages
05/2010;
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B. Schulz,
C. P. Pearson,
D. L. Clements,
B. Altieri,
A. Amblard,
V. Arumugam,
R. Auld,
H. Aussel,
T. Babbedge,
A. Blain, [......],
K. E. Tugwell,
M. Vaccari,
E. Valiante,
I. Valtchanov,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: We present colours of sources detected with the Herschel/SPIRE instrument in deep extragalactic surveys of the Lockman Hole, Spitzer-FLS, and GOODS-N fields in three photometric bands at 250, 350 and 500 micrometers. We compare these with expectations from the literature and discuss associated uncertainties and biases in the SPIRE data. We identify a 500 micrometer flux limited selection of sources from the HerMES point source catalogue that appears free from neighbouring/blended sources in all three SPIRE bands. We compare the colours with redshift tracks of various contemporary models. Based on these spectral templates we show that regions corresponding to specific population types and redshifts can be identified better in colour-flux space. The redshift tracks as well as the colour-flux plots imply a majority of detected objects with redshifts at 1<z<3.5, somewhat depending on the group of model SEDs used. We also find that a population of S_250/S_350<0.8 at fluxes above 50 mJy as observed by SPIRE is not well represented by contemporary models and could consist of a mix of cold and lensed galaxies. Comment: 5 pages, 8 figures, for special Herschel issue
05/2010;
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S. J. Oliver,
L Wang,
A J Smith,
B. Altieri,
A. Amblard,
V. Arumugam,
R. Auld,
H. Aussel,
T. Babbedge,
A. Blain, [......],
K. E. Tugwell,
M. Vaccari,
E. Valiante,
I. Valtchanov,
J. D. Vieira,
L. Vigroux, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: Emission at far-infrared wavelengths makes up a significant fraction of the total light detected from galaxies over the age of Universe. Herschel provides an opportunity for studying galaxies at the peak wavelength of their emission. Our aim is to provide a benchmark for models of galaxy population evolution and to test pre-existing models of galaxies. With the Herschel Multi-tiered Extra-galactic survey, HerMES, we have observed a number of fields of different areas and sensitivity using the SPIRE instrument on Herschel. We have determined the number counts of galaxies down to ~20 mJy. Our constraints from directly counting galaxies are consistent with, though more precise than, estimates from the BLAST fluctuation analysis. We have found a steep rise in the Euclidean normalised counts at <100 mJy. We have directly resolved 15% of the infrared extra-galactic background at the wavelength near where it peaks. Comment: Astronomy and Astrophysics, Herschel Special Issue, in press as a Letter; 5 pages
05/2010;
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S. A. Eales,
G Raymond,
I. G. Roseboom,
B. Altieri,
A. Amblard,
V. Arumugam,
R. Auld,
H. Aussel,
T. Babbedge,
A. Blain, [......],
M. Trichas,
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: We have carried out two extremely deep surveys with SPIRE, one of the two cameras on Herschel, at 250 microns, close to the peak of the far-infrared background. We have used the results to investigate the evolution of the rest-frame 250-micron luminosity function out to z=2. We find evidence for strong evolution out to a redshift of around 1 but evidence for at most weak evolution beyond this redshift. Our results suggest that a significant part of the stars and metals in the Universe today were formed at z<1.4 in spiral galaxies. Comment: Astronomy and Astrophysics, Herschel Special Issue, in press as a Letter; 5 pages
http://dx.doi.org/10.1051/0004-6361/201014675. 05/2010;
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E. Hatziminaoglou,
A. Omont,
J. A. Stevens,
A. Amblard,
V. Arumugam,
R. Auld,
H. Aussel,
T. Babbedge,
A. Blain,
J. Bock, [......],
M. Trichas,
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
[show abstract]
[hide abstract]
ABSTRACT: Nuclear and starburst activity are known to often occur concomitantly. Herschel-SPIRE provides sampling of the FIR SEDs of type 1 and type 2 AGN, allowing for the separation between the hot dust (torus) and cold dust (starburst) emission. We study large samples of spectroscopically confirmed type 1 and type 2 AGN lying within the Herschel Multi-tiered Extragalactic Survey (HerMES) fields observed during the science demonstration phase, aiming to understand their FIR colour distributions and constrain their starburst contributions. We find that one third of the spectroscopically confirmed AGN in the HerMES fields have 5-sigma detections at 250um, in agreement with previous (sub)mm AGN studies. Their combined Spitzer-MIPS and Herschel-SPIRE colours - specifically S(250)/S(70) vs. S(70)/S(24) - quite clearly separate them from the non-AGN, star-forming galaxy population, as their 24-um flux is dominated by the hot torus emission. However, their SPIRE colours alone do not differ from those of non-AGN galaxies. SED fitting shows that all those AGN need a starburst component to fully account for their FIR emission. For objects at z > 2, we find a correlation between the infrared luminosity attributed to the starburst component, L(SB), and the AGN accretion luminosity, L(acc), with L(SB) propto L(acc)^0.35. Type 2 AGN detected at 250um show on average higher L(SB) than type 1 objects but their number is still too low to establish whether this trend indicates stronger star-formation activity. Comment: Astronomy and Astrophysics, Herschel Special Issue, in press as a Letter; 5 pages
http://dx.doi.org/10.1051/0004-6361/201014679. 05/2010;
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M. Vaccari,
L. Marchetti,
A. Franceschini,
B. Altieri,
A. Amblard,
V. Arumugam,
R. Auld,
H. Aussel,
T. Babbedge,
A. Blain, [......],
M. Trichas,
K. E. Tugwell,
E. Valiante,
I. Valtchanov,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
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ABSTRACT: 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. Comment: Accepted for publication in the A&A Herschel Special Issue
http://dx.doi.org/10.1051/0004-6361/201014694. 05/2010;
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R. J. Ivison,
B. Magnelli,
E. Ibar,
P. Andreani,
D. Elbaz,
B. Altieri,
A. Amblard,
V. Arumugam,
R. Auld,
H. Aussel, [......],
K. E. Tugwell,
M. Vaccari,
I. Valtchanov,
J. Vieira,
L. Vigroux,
L Wang, R Ward,
G Wright,
C. K. Xu,
M. Zemcov
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ABSTRACT: We set out to determine the ratio, q(IR), of rest-frame 8-1000um flux, S(IR), to monochromatic radio flux, S(1.4GHz), for galaxies selected at far-IR and radio wavelengths, to search for signs that the ratio evolves with redshift, luminosity or dust temperature, and to identify any far-IR-bright outliers - useful laboratories for exploring why the far-IR/radio correlation is generally so tight when the prevailing theory suggests variations are almost inevitable. We use flux-limited 250-um and 1.4-GHz samples, obtained in GOODS-N using Herschel (HerMES; PEP) and the VLA. We determine bolometric IR output using ten bands spanning 24-1250um, exploiting data from PACS and SPIRE, as well as Spitzer, SCUBA, AzTEC and MAMBO. We also explore the properties of an L(IR)-matched sample, designed to reveal evolution of q(IR) with z, spanning log L(IR) = 11-12 L(sun) and z=0-2, by stacking into the radio and far-IR images. For 1.4-GHz-selected galaxies, we see tentative evidence of a break in the flux ratio, q(IR), at L(1.4GHz) ~ 10^22.7 W/Hz, where AGN are starting to dominate the radio power density, and of weaker correlations with z and T(d). From our 250-um-selected sample we identify a small number of far-IR-bright outliers, and see trends of q(IR) with L(1.4GHz), L(IR), T(d) and z, noting that some of these are inter-related. For our L(IR)-matched sample, there is no evidence that q(IR) changes significantly as we move back into the epoch of galaxy formation: we find q(IR) goes as (1+z)^gamma, where gamma = -0.04 +/- 0.03 at z=0-2; however, discounting the least reliable data at z<0.5 we find gamma = -0.26 +/- 0.07, modest evolution which may be related to the radio background seen by ARCADE2, perhaps driven by <10uJy radio activity amongst ordinary star-forming galaxies at z>1. Comment: A&A Herschel Special Issue, in press as a Letter. 5 pages
05/2010;
