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We have observed 104 gravitationally-lensed quasars at $z\sim1-4$ with Herschel/SPIRE, the largest such sample ever studied. By targeting gravitational lenses, we probe intrinsic far-infrared (FIR) luminosities and star formation rates (SFRs) more typical of the population than the extremely luminous sources that are otherwise accessible. We detect 72 objects with Herschel/SPIRE and find 66 percent (69 sources) of the sample have spectral energy distributions (SEDs) characteristic of dust emission. For 53 objects with sufficiently constrained SEDs, we find a median effective dust temperature of $38^{+12}_{-5}$ K. By applying the radio-infrared correlation, we find no evidence for an FIR excess which is consistent with star-formation-heated dust. We derive a median magnification-corrected FIR luminosity of $3.6^{+4.8}_{-2.4}~\times 10^{11}~{\rm L_{\odot}}$ and median SFR of $120^{+160}_{-80}~{\rm M_{\odot}~yr^{-1}}$ for 94 quasars with redshifts. We find $\sim10$ percent of our sample have FIR properties similar to typical dusty star-forming galaxies at $z\sim2-3$ and a range of SFRs $<20-10000~{\rm M_{\odot}~yr^{-1}}$ for our sample as a whole. These results are in line with current models of quasar evolution and suggests a coexistence of dust-obscured star formation and AGN activity is typical of most quasars. We do not find a statistically-significant difference in the FIR luminosities of quasars in our sample with a radio excess relative to the radio-infrared correlation. Synchrotron emission is found to dominate at FIR wavelengths for $<15$ percent of those sources classified as powerful radio galaxies., Comment: 47 pages, 89 figures, accepted for publication in MNRAS

We present new CO and C^o line measurements of the compact circumnuclear disk in the center of NGC 128 (Centaurus~A) obtained with the Herschel Space Observatory, as well as SEST, JCMT, and APEX. The Cen A center CO ladder is quite different from those of either star-burst galaxies or AGNs. In addition, the relative intensity of the central Cen A [CI] emission lines is much greate than that in any other galaxy. The CO surface brightness of the compact circumnuclear disk (CND) is significantly higher than that of the much more extended thin disk (ETD) in the same line of sight. Our LVG and PDR/XDR models suggest that much of the CND gas is relatively cool (25 - 80 K) and not very dense (~ 300 cm^{-3}) if the heating is by UV photons, although there is some gas in both the CND and the ETD with a much higher density of ~30 000 cm^{-3}. Finally, there is also high-excitation, high-density phase in the CND (but not in the ETD), either in the form of an extreme PDR but more likely in the form of an XDR. The total gas mass of the Cen A CND is 8.4 x 10^{7} M(sun), uncertain by a factor of two. The CO-H2 conversion factor is 4 x 10^{20} K km/s, also within a factor of two., Comment: 14 pages, 5 figures; A&A in press

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 H2O rotational lines, and [CI] and [NII] 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 H2 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 H2 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 H2 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., Comment: Accepted by Astrophysical Journal Letters

The bright submillimetre (sub-mm) galaxy MM 18423+5938 at redshift 3.9296 has been predicted from mid-infrared and millimetre photometry to have an exceptionally large total infrared (IR) luminosity. We present new radio imaging at 1.4 GHz with the Westerbork Synthesis Radio Telescope that is used to determine a radio-derived total IR luminosity for MM 18423+5938 via the well established radio-far-infrared correlation. The flux density is found to be S_1.4 GHz = 217 +/- 37 \mu Jy, which corresponds to a rest-frame luminosity density of L_1.4 GHz = 2.32 +/- 0.40 x 10^25 / u W / Hz, where u is the magnification from a probable gravitational lens. The radio-derived total IR luminosity and star-formation rate are L_8-1000 \mu m = 5.6^+4.1_-2.4 x 10^13 / u L_sol and SFR = 9.4^+7.4_-4.9 x 10^3 / u M_sol / yr, respectively, which are ~9 times smaller than those previously reported. These differences are attributed to the IR spectral energy distribution of MM 18423+5938 being poorly constrained by the limited number of reliable photometric data that are currently available, and from a previous misidentification of the object at 70 \mu m. Using the radio derived total IR luminosity as a constraint, the temperature of the cold dust component is found to be T ~ 24^+7_-5 K for a dust emissivity of \beta = 1.5 +/- 0.5. The radio-derived properties of this galaxy are still large given the low excitation temperature implied by the CO emission lines and the temperature of the cold dust. Therefore, we conclude that MM 18423+5938 is probably gravitationally lensed., Comment: 5 pages, 2 figures, 1 table, accepted for publication in MNRAS Letters

Context: Molecular data of extreme environments, such as Arp 220, but also NGC 253, show evidence for extremely high cosmic ray (CR) rates (10^3-10^4 * Milky Way) and mechanical heating from supernova driven turbulence. Aims: The consequences of high CR rates and mechanical heating on the chemistry in clouds are explored. Methods: PDR model predictions are made for low, n=10^3, and high, n=10^5.5 cm^-3, density clouds using well-tested chemistry and radiation transfer codes. Column densities of relevant species are discussed, and special attention is given to water related species. Fluxes are shown for fine-structure lines of O, C+, C, and N+, and molecular lines of CO, HCN, HNC, and HCO+. A comparison is made to an X-ray dominated region model. Results: Fine-structure lines of [CII], [CI], and [OI] are remarkably similar for different mechanical heating and CR rates, when already exposed to large amounts of UV. HCN and H2O abundances are boosted for very high mechanical heating rates, while ionized species are relatively unaffected. OH+ and H2O+ are enhanced for very high CR rates zeta > 5 * 10^-14 s^-1. A combination of OH+, OH, H2O+, H2O, and H3O+ trace the CR rates, and are able to distinguish between enhanced cosmic rays and X-rays., Comment: 13 pages, 8 figures, A&A accepted

We present high resolution HIFI spectroscopy of the nucleus of the archetypical starburst galaxy M82. Six 12CO lines, 2 13CO lines and 4 fine-structure lines are detected. Besides showing the effects of the overall velocity structure of the nuclear region, the line profiles also indicate the presence of multiple components with different optical depths, temperatures and densities in the observing beam. The data have been interpreted using a grid of PDR models. It is found that the majority of the molecular gas is in low density (n=10^3.5 cm^-3) clouds, with column densities of N_H=10^21.5 cm^-2 and a relatively low UV radiation field (GO = 10^2). The remaining gas is predominantly found in clouds with higher densities (n=10^5 cm^-3) and radiation fields (GO = 10^2.75), but somewhat lower column densities (N_H=10^21.2 cm^-2). The highest J CO lines are dominated by a small (1% relative surface filling) component, with an even higher density (n=10^6 cm^-3) and UV field (GO = 10^3.25). These results show the strength of multi-component modeling for the interpretation of the integrated properties of galaxies., Comment: Accepted for publication in A&A Letters

The Ultra Luminous InfraRed Galaxy Mrk 231 reveals up to seven rotational lines of water (H2O) in emission, including a very high-lying (E_{upper}=640 K) line detected at a 4sigma level, within the Herschel/SPIRE wavelength range, whereas PACS observations show one H2O line at 78 microns in absorption, as found for other H2O 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 H2O 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 H2O and the corresponding line fluxes. The highest-lying H2O 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(H2O)~5x10^{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 H2O lines through dense hot cores, and/or shocks. The H2O 78 micron line observed with PACS shows hints of a blue-shifted wing seen in absorption, possibly indicating the occurrence of H2O in the prominent outflow detected in OH (Fischer et al., this volume)., Comment: 5 pages, 3 figures

We present a full high resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk231. In total 25 lines are detected, including CO J=5-4 through J=13-12, 7 rotational lines of H2O, 3 of OH+ and one line each of H2O+, 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 Mrk231 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 Mrk231. 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 Mrk231 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 Mrk231. The extraordinary luminosity of the OH+ and H2O+ lines reveals the signature of X-ray driven excitation and chemistry in this region., Comment: 5 pages, 2 figures, accepted for publication in Astronomy & Astrophysics Special Issue on Herschel first results

Molecules that trace the high-density regions of the interstellar medium may be used to evaluate the changing physical and chemical environment during the ongoing nuclear activity in (Ultra-)Luminous Infrared Galaxies. The changing ratios of the HCN(1-0), HNC(1-0), HCO+(1-0), CN(1-0) and CN(2-1), and CS(3-2) transitions were compared with the HCN(1-0)/CO(1-0) ratio, which is proposed to represent the progression time scale of the starburst. These diagnostic diagrams were interpreted using the results of theoretical modeling using a large physical and chemical network to describe the state of the nuclear ISM in the evolving galaxies. Systematic changes are seen in the line ratios as the sources evolve from early stage for the nuclear starburst (ULIRGs) to later stages. These changes result from changing environmental conditions and particularly from the lowering of the average density of the medium. A temperature rise due to mechanical heating of the medium by feedback explains the lowering of the ratios at later evolutionary stages. Infrared pumping may affect the CN and HNC line ratios during early evolutionary stages. Molecular transitions display a behavior that relates to changes of the environment during an evolving nuclear starburst. Molecular properties may be used to designate the evolutionary stage of the nuclear starburst. The HCN(1-0)/CO(1-0) and HCO+(1-0)/HCN(1-0) ratios serve as indicators of the time evolution of the outburst., Comment: To be published in Astronomy and Astrophysics - 11 pages, 9 figures, 1 table

Aims: Molecular emission lines originating in the nuclei of luminous infra-red galaxies are used to determine the physical properties of the nuclear ISM in these systems. Methods: A large observational database of molecular emission lines is compared with model predictions that include heating by UV and X-ray radiation, mechanical heating, and the effects of cosmic rays. Results: The observed line ratios and model predictions imply a separation of the observedsystems into three groups: XDRs, UV-dominated high-density (n>=10^5 cm-3) PDRs, and lower-density (n=10^4.5 cm-3) PDRs that are dominated by mechanical feedback. Conclusions: The division of the two types of PDRs follows naturally from the evolution of the star formation cycle of these sources, which evolves from deeply embedded young stars, resulting in high-density (n>=10^5 cm-3) PDRs, to a stage where the gas density has decreased (n=10^4.5 cm-3) and mechanical feedback from supernova shocks dominates the heating budget., Comment: 4 pages, 3 figures, published as Letter to the Editor in A&A (see http://www.aanda.org/articles/aa/abs/2008/34/aa10327-08/aa10327-08.html)

Molecules that trace the high-density regions of the interstellar medium have been observed in (ultra-)luminous (far-)infrared galaxies, in order to initiate multiple-molecule multiple-transition studies to evaluate the physical and chemical environment of the nuclear medium and its response to the ongoing nuclear activity. The HCN(1-0), HNC(1-0), HCO+(1-0), CN(1-0) and CN(2-1), CO(2-1), and CS(3-2) transitions were observed in sources covering three decades of infrared luminosity including sources with known OH megamaser activity. The data for the molecules that trace the high-density regions have been augmented with data available in the literature. The integrated emissions of high-density tracer molecules show a strong relation to the far-infrared luminosity. Ratios of integrated line luminosities have been used for a first order diagnosis of the integrated molecular environment of the evolving nuclear starbursts. Diagnostic diagrams display significant differentiation among the sources that relate to initial conditions and the radiative excitation environment. Initial differentiation has been introduced between the FUV radiation field in photon-dominated-regions and the X-ray field in X-ray-dominated-regions. The galaxies displaying OH megamaser activity have line ratios typical of photon-dominated regions., Comment: 19 pages, 12 figures, accepted by A&A

The nuclei of ULIRGs harbor massive young stars, an accreting central black hole, or both. Results are presented for molecular gas that is exposed to X-rays (1-100 keV, XDRs) and far-ultraviolet radiation (6-13.6 eV, PDRs). Attention is paid to species like HCO+, HCN, HNC, OH, H2O and CO. Line ratios of HCN/HCO+ and HNC/HCN discriminate between PDRs and XDRs. Very high J (>10) CO lines, observable with HIFI/Herschel, discriminate very well between XDRs and PDRs. In XDRs, it is easy to produce large abundances of warm (T>100 K) H2O and OH. In PDRs, only OH is produced similarly well., Comment: 5 pages, 6 figures, to appear in: IAU Symposium 242 Astrophysical Masers and their Environments

The observed molecular properties of a sample of FIR-luminous and OH megamaser (OH-MM) galaxies have been investigated. The ratio of high and low-density tracer lines is found to be determined by the progression of the star formation in the system. The HCO+/HCN and HCO+/HNC line ratios are good proxies for the density of the gas, and PDR and XDR sources can be distinguished using the HNC/HCN line ratio. The properties of the OH-MM sources in the sample can be explained by PDR chemistry in gas with densities higher than 10^5.5 cm^-3, confirming the classical OH-MM model of IR pumped amplification with (variable) low gains., Comment: 5 pages, 2 figures, to appear in: IAU Symposium 242 Astrophysical Masers and their Environments

An evolutionary model of star formation in ULIRGs was created using existing star formation and radiative transfer codes (STARBURST99, RADMC and RADICAL) as building blocks. The results of the simulations are compared to data from two IRAS catalogs. From the simulations it is found that the dust surrounding the starburst region is made up from two components. There is a low optical depth (tau=0.1, which corresponds to 0.1% of the total dust mass), hot (T~400K) non-grey component close to the starburst (scale size 10pc) and a large scale, colder grey component (100pc, 75K) with a much larger column (tau=10). The simulations also show that starburst galaxies can be powered by massive star formation. The parameters for this star forming region are difficult to determine, since the IR continuum luminosity is only sensitive to the total UV input. Therefore, there is a degeneracy between the total starburst mass and the initial mass function (IMF) slope. A less massive star formation with a shallower IMF will produce the same amount of OB stars and therefore the same amount of irradiating UV flux. Assuming the stars are formed according to a Salpeter IMF (Psi(M) ~ M^-2.35), the star formation region should produce 10^9 Msun of stars (either in one instantaneous burst, or in a continuous process) in order to produce enough IR radiation., Comment: 37 pages, 32 figures, accepted by Astronomy and Astrophysics. Version with Appendices can be obtained from http://www.astro.rug.nl/~loenen/Loenen_et_al_2006.pdf