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 μm, and an imaging Fourier-transform spectrometer (FTS) which covers simultaneously its whole operating range of 194-671 μm (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 × 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. Key words. instrumentation: photometers -instrumentation: spectrographs -space vehicles: instruments -submillimeter: generalHerschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

The Herschel Multi‐tiered Extragalactic Survey (HerMES) is a legacy programme designed to map a set of nested fields totalling ∼380 deg2. Fields range in size from 0.01 to ∼20 deg2, using the Herschel‐Spectral and Photometric Imaging Receiver (SPIRE) (at 250, 350 and 500 μm) and the Herschel‐Photodetector Array Camera and Spectrometer (PACS) (at 100 and 160 μm), with an additional wider component of 270 deg2 with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the reprocessed optical and ultraviolet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multiwavelength understanding of galaxy formation and evolution. The survey will detect of the order of 100 000 galaxies at 5σ 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.

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 μm, 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.

The extragalactic background light at far-infrared wavelengths 1-3 originates from opticallyfaint, dusty, star-forming galaxies in the universe with star-formation rates at the level of a few hundred solar masses per year 4 . Due to the relatively poor spatial resolution of farinfrared telescopes 5, 6 , the faint sub-millimetre galaxies are challenging to study individually. Instead, their average properties can be studied using statistics such as the angular power spectrum of the background intensity variations 7-10 . A previous attempt 11 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 12 . Here we report a clear detection of the 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 halos with a minimum mass of log[M min /M ⊙ ] = 11.5 +0.7 −0.2 at 350 µm. This minimum dark matter halo mass corresponds to the most efficient mass scale for star formation in the universe 13 , and is lower than that predicted by semi-analytical models for galaxy formation 14 .Despite recent successes in attributing most of the extragalactic background light at submillimetre wavelengths to known galaxy populations through stacking analyses 15-17 , we have not individually detected the faint galaxies that are responsible for more than 85% of the total extragalactic intensity at these wavelengths 18 . The faint star-forming galaxies are expected to trace the large-scale structure of the Universe, especially in models where galaxy formation and evolution is closely connected to dark matter halos. While not individually detected in low resolution observations, the clustering of galaxies is expected to leave a distinct signature in the total intensity variations at sub-millimetre wavelengths. The amplitude of the power spectrum of intensity vari-2 ations as a function of the angular scale provides details on the redshift distribution and the dark matter halo mass scale of dusty, star-forming galaxies in the universe 7 .For this analysis, we used data from the Herschel Multi-tiered Extra-galactic survey (HerMES 18 ), taken with the Spectral and Photometric Imaging Receiver (SPIRE 19 ) onboard the Herschel Space Observatory 20 , during the Science Demonstration Phase (SDP) of Herschel. The data are composed of a wide 218 ′ by 218 ′ area in the Lockman Hole complemented by a narrow, but very deep (30 repeated scans), map of the Great Observatories Origins Deep Survey (GOODS) North field covering 30 ′ by 30 ′ . These fields have been very well studied at other wavelengths and they are known to have a low Galactic dust density, making it easier to distinguish the extragalactic component we wish to study. The observing time to complete each of the two fields was about 13.5 hours, observing simultaneously at 250, 350, and 500 µm.To limit the influence of a few ...

We set out to determine the ratio, q IR , of rest-frame 8-1000-μm flux, S IR , to monochromatic radio flux, S 1.4 GHz , for galaxies selected at far-infrared (IR) and radio wavelengths, to search for signs that the ratio evolves with redshift, luminosity or dust temperature, T d , and to identify any far-IR-bright outliers -useful laboratories for exploring why the far-IR/radio correlation (FIRRC) is generally so tight when the prevailing theory suggests variations are almost inevitable. We use flux-limited 250-μm and 1.4-GHz samples, obtained using Herschel and the Very Large Array (VLA) in GOODS-North (-N). We determine bolometric IR output using ten bands spanning λ obs = 24−1250 μm, exploiting data from PACS and SPIRE (PEP; HerMES), 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 redshift, spanning log L IR = 11-12 L and z = 0−2, by stacking into the radio and far-IR images. For 1.4-GHz-selected galaxies in GOODS-N, we see tentative evidence of a break in the flux ratio, q IR , at L 1.4 GHz ∼ 10 22.7 W Hz −1 , where active galactic nuclei (AGN) are starting to dominate the radio power density, and of weaker correlations with redshift and T d . From our 250-μm-selected sample we identify a small number of far-IR-bright outliers, and see trends of q IR with L 1.4 GHz , L IR , T d and redshift, 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 ∝ (1 + z) γ , where γ = −0.04 ± 0.03 at z = 0 − 2; however, discounting the least reliable data at z < 0.5 we find γ = −0.26 ± 0.07, modest evolution which may be related to the radio background seen by ARCADE 2, perhaps driven by <10-μJy radio activity amongst ordinary star-forming galaxies at z > 1.