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.

We present a detailed analysis of the far-infrared (-IR) properties of the bright, lensed, z = 2.3, submillimetre-selected galaxy (SMG), SMM J2135−0102 (hereafter SMM J2135), using new observations with Herschel, SCUBA-2 and the Very Large Array (VLA). These data allow us to constrain the galaxy's spectral energy distribution (SED) and show that it has an intrinsic rest-frame 8−1000-μm luminosity, L bol , of (2.3 ± 0.2) × 10 12 L and a likely star-formation rate (SFR) of ∼400 M yr −1 . The galaxy sits on the far-IR/radio correlation for far-IR-selected galaxies. At > ∼ 70 μm, the SED can be described adequately by dust components with dust temperatures, T d ∼ 30 and 60 k. Using SPIRE's Fouriertransform spectrometer (FTS) we report a detection of the [C ii] 158 μm cooling line. If the [C ii], CO and far-IR continuum arise in photodissociation regions (PDRs), we derive a characteristic gas density, n ∼ 10 3 cm −3 , and a far-ultraviolet (-UV) radiation field, G 0 , 10 3 × stronger than the Milky Way. L [CII] /L bol is significantly higher than in local ultra-luminous IR galaxies (ULIRGs) but similar to the values found in local star-forming galaxies and starburst nuclei. This is consistent with SMM J2135 being powered by starburst clumps distributed across ∼2 kpc, evidence that SMGs are not simply scaled-up ULIRGs. Our results show that SPIRE's FTS has the ability to measure the redshifts of distant, obscured galaxies via the blind detection of atomic cooling lines, but it will not be competitive with ground-based CO-line searches. It will, however, allow detailed study of the integrated properties of high-redshift galaxies, as well as the chemistry of their interstellar medium (ISM), once more suitably bright candidates have been found.

We present FIR[50 − 300 µm]−CO luminosity relations (i.e., log L FIR = α log L CO + β) for the full CO rotational ladder from J = 1 − 0 up to J = 13 − 12 for a sample of 62 local (z ≤ 0.1) (Ultra) Luminous Infrared Galaxies (LIRGs; L IR[8−1000 µm] > 10 11 L ) using data from Herschel SPIRE-FTS and ground-based telescopes. We extend our sample to high redshifts (z > 1) by including 35 (sub)millimeter selected dusty star forming galaxies from the literature with robust CO observations, and sufficiently well-sampled FIR/sub-millimeter spectral energy distributions (SEDs) so that accurate FIR luminosities can be deduced. The addition of luminous starbursts at high redshifts enlarge the range of the FIR−CO luminosity relations towards the high-IR-luminosity end while also significantly increasing the small amount of mid-J/high-J CO line data (J = 5 − 4 and higher) that was available prior to Herschel. This new data-set (both in terms of IR luminosity and J-ladder) reveals linear FIR−CO luminosity relations (i.e., α 1) for J = 1 − 0 up to J = 5 − 4, with a nearly constant normalization (β ∼ 2). In the simplest physical scenario this is expected from the (also) linear FIR−(molecular line) relations recently found for the dense gas tracer lines (HCN and CS), as long as the dense gas mass fraction does not vary strongly within our (merger/starburst)-dominated sample. However from J = 6 − 5 and up to the J = 13 − 12 transition we find an increasingly sub-linear slope and higher normalization constant with increasing J. We argue that these are caused by a warm (∼ 100 K) and dense (> 10 4 cm −3 ) gas component whose thermal state is unlikely to be maintained by star formation powered far-UV radiation fields (and thus is no longer directly tied to the star formation rate). We suggest that mechanical heating (e.g., supernova driven turbulence and shocks), and not cosmic rays, is the more likely source of energy for this component. The global CO spectral line energy distributions (SLEDs), which remain highly excited from J = 6 − 5 up to J = 13 − 12, are found to be a generic feature of the (U)LIRGs in our sample, and further support the presence of this gas component.

We present a full high resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk 231. In total 25 lines are detected, including CO J = 5−4 through J = 13−12, 7 rotational lines of H 2 O, 3 of OH + and one line each of H 2 O + , CH + , and HF. We find that the excitation of the CO rotational levels up to J = 8 can be accounted for by UV radiation from star formation. However, the approximately flat luminosity distribution of the CO lines over the rotational ladder above J = 8 requires the presence of a separate source of excitation for the highest CO lines. We explore X-ray heating by the accreting supermassive black hole in Mrk 231 as a source of excitation for these lines, and find that it can reproduce the observed luminosities. We also consider a model with dense gas in a strong UV radiation field to produce the highest CO lines, but find that this model strongly overpredicts the hot dust mass in Mrk 231. Our favoured model consists of a star forming disk of radius 560 pc, containing clumps of dense gas exposed to strong UV radiation, dominating the emission of CO lines up to J = 8. X-rays from the accreting supermassive black hole in Mrk 231 dominate the excitation and chemistry of the inner disk out to a radius of 160 pc, consistent with the X-ray power of the AGN in Mrk 231. The extraordinary luminosity of the OH + and H 2 O + lines reveals the signature of X-ray driven excitation and chemistry in this region.

We present Herschel SPIRE FTS spectroscopy of the nearby luminous infrared galaxy NGC 6240. In total 20 lines are detected, including CO J = 4 − 3 through J = 13 − 12, 6 H 2 O rotational lines, and [C i] and [N ii] fine-structure lines. The CO to continuum luminosity ratio is 10 times higher in NGC 6240 than Mrk 231. Although the CO ladders of NGC 6240 and Mrk 231 are very similar, UV and/or X-ray irradiation are unlikely to be responsible for the excitation of the gas in NGC 6240. We applied both C and J shock models to the H 2 v = 1 − 0 S(1) and v = 2 − 1 S(1) lines and the CO rotational ladder. The CO ladder is best reproduced by a model with shock velocity v s = 10 km s −1 and a pre-shock density n H = 5 × 10 4 cm −3 . We find that the solution best fitting the H 2 lines is degenerate: The shock velocities and number densities range between v s = 17 − 47 km s −1 and n H = 10 7 − 5 × 10 4 cm −3 , respectively. The H 2 lines thus need a much more powerful shock than the CO lines. We deduce that most of the gas is currently moderately stirred up by slow (10 km s −1 ) shocks while only a small fraction ( 1 percent) of the ISM is exposed to the high velocity shocks. This implies that the gas is rapidly loosing its highly turbulent motions. We argue that a high CO line-to-continuum ratio is a key diagnostic for the presence of shocks. CO J = 1 − 0 a 2600.76 322 ± 29 4.3 × 10 5,d CO J = 2 − 1 a 1300.40 1490 ± 250 4.0 × 10 6 CO J = 3 − 2 a 866.963 3210 ± 640 1.2 × 10 7 CO J = 4 − 3 449.99 650.252 4630 ± 370 2.8 × 10 7 CO J = 5 − 4 562.41 520.231 5640 ± 150 3.8 × 10 7 CO J = 6 − 5 674.83 433.556 5910 ± 82 4.8 × 10 7 CO J = 7 − 6 787.25 371.650 6010 ± 60 5.6 × 10 7 CO J = 8 − 7 899.68 325.225 5830 ± 89 6.3 × 10 7 CO J = 9 − 8 1012.1 289.120 4770 ± 82 5.7 × 10 7 CO J = 10 − 9 1124.5 260.240 4160 ± 67 5.6 × 10 7 CO J = 11 − 10 1236.9 236.613 3160 ± 75 4.7 × 10 7 CO J = 12 − 11 1349.1 216.927 2590 ± 60 4.2 × 10 7 CO J = 13 − 12 1461.2 200.272 2080 ± 60 3.6 × 10 7 13 CO J = 6 − 5 b 645.21 453.498 < 112 ± 67 8.6 × 10 5 [C i] 3 P 1 − 3 P 0 480.27 609.135