We present Herschel SPIRE-FTS observations of Arp 220, a nearby ultraluminous infrared galaxy. The FTS provides continuous spectral coverage from 1 The SPIRE beam shapes are not gaussian; the effective beam solid angle can be found in the Herschel Observer's manual.

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.

The Herschel Reference Survey is a Herschel guaranteed time key project and will be a benchmark study of dust in the nearby universe. The survey will complement a number of other Herschel key projects including large cosmological surveys that trace dust in the distant universe. We will use Herschel to produce images of a statistically-complete sample of 323 galaxies at 250, 350, and 500 ??m. The sample is volume-limited, containing sources with distances between 15 and 25 Mpc and flux limits in the K band to minimize the selection effects associated with dust and with young high-mass stars and to introduce a selection in stellar mass. The sample spans the whole range of morphological types (ellipticals to late-type spirals) and environments (from the field to the center of the Virgo Cluster) and as such will be useful for other purposes than our own. We plan to use the survey to investigate (i) the dust content of galaxies as a function of Hubble type, stellar mass, and environment; (ii) the connection between the dust content and composition and the other phases of the interstellar medium; and (iii) the origin and evolution of dust in galaxies. In this article, we describe the goals of the survey, the details of the sample and some of the auxiliary observing programs that we have started to collect complementary data. We also use the available multifrequency data to carry out an analysis of the statistical properties of the sample

We present the observations of the starburst galaxy M82 taken with the Herschel SPIRE Fourier-transform spectrometer. The spectrum (194-671 μm) shows a prominent CO rotational ladder from J = 4-3 to 13-12 emitted by the central region of M82. The fundamental properties of the gas are well constrained by the high J lines observed for the first time. Radiative transfer modeling of these high-S/N 12 CO and 13 CO lines strongly indicates a very warm molecular gas component at ∼500 K and pressure of ∼3 × 10 6 K cm −3 , in good agreement with the H 2 rotational lines measurements from Spitzer and ISO. We suggest that this warm gas is heated by dissipation of turbulence in the interstellar medium (ISM) rather than X-rays or UV flux from the straburst. This paper illustrates the promise of the SPIRE FTS for the study of the ISM of nearby galaxies.

The Ultra luminous infrared galaxy (ULIRG) Mrk 231 reveals up to seven rotational lines of water (H 2 O) in emission, including a very high-lying (E upper = 640 K) line detected at a 4σ level, within the Herschel/SPIRE wavelength range (190 < λ(μm) < 640), whereas PACS observations show one H 2 O line at 78 μm in absorption, as found for other H 2 O lines previously detected by ISO. The absorption/emission dichotomy is caused by the pumping of the rotational levels by far-infrared radiation emitted by dust, and subsequent relaxation through lines at longer wavelengths, which allows us to estimate both the column density of H 2 O and the general characteristics of the underlying far-infrared continuum source. Radiative transfer models including excitation through both absorption of far-infrared radiation emitted by dust and collisions are used to calculate the equilibrium level populations of H 2 O and the corresponding line fluxes. The highest-lying H 2 O lines detected in emission, with levels at 300−640 K above the ground state, indicate that the source of far-infrared radiation responsible for the pumping is compact (radius = 110−180 pc) and warm (T dust = 85−95 K), accounting for at least 45% of the bolometric luminosity. The high column density, N(H 2 O) ∼ 5 × 10 17 cm −2 , found in this nuclear component, is most probably the consequence of shocks/cosmic rays, an XDR chemistry, and/or an "undepleted chemistry" where grain mantles are evaporated. A more extended region, presumably the inner region of the 1-kpc disk observed in other molecular species, could contribute to the flux observed in low-lying H 2 O lines through dense hot cores, and/or shocks. The H 2 O 78 μm line observed with PACS shows hints of a blue-shifted wing seen in absorption, possibly indicating the occurrence of H 2 O in the prominent outflow detected in OH (Fischer et al. 2010, A&A, 518, L41). Additional PACS/HIFI observations of H 2 O lines are required to constrain the kinematics of the nuclear component, as well as the distribution of H 2 O relative to the warm dust.