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We empirically MD test the relation between the SFR(LIR) derived from the infrared luminosity, LIR, and the SFR(Ha) derived from the Ha emission line luminosity using simple conversion relations. We use a sample of 474 galaxies at z = 0.060.46 with both Ha detection [from 20k redshift Cosmological Evolution (zCOSMOS) survey] and new far-IR Herschel data (100 and 160 mu m). We derive SFR(Ha) from the Ha extinction corrected emission line luminosity. We find a very clear trend between E(B - V) and LIR that allows us to estimate extinction values for each galaxy even if the H beta emission line measurement is not reliable. We calculate the LIR by integrating from 8 up to 1000 mu m the spectral energy distribution (SED) that is best fitting our data. We compare the SFR(Ha) with the SFR(LIR). We find a very good agreement between the two star formation rate (SFR) estimates, with a slope of m = 1.01 +/- 0.03 in the log SFR(LIR) versus log SFR(Ha) diagram, a normalization constant of a = -0.08 +/- 0.03 and a dispersion of s = 0.28 dex. We study the effect of some intrinsic properties of the galaxies in the SFR(LIR)SFR(Ha) relation, such as the redshift, the mass, the specific star formation rate (SSFR) or the metallicity. The metallicity is the parameter that affects most the SFR comparison. The mean ratio of the two SFR estimators log[SFR(LIR)/SFR(Ha)] varies by similar to 0.6 dex from metal-poor to metal-rich galaxies [8.1

We present the first results of a multiwavelength survey, incorporating Herschel-, Spitzer, GALEX and Australian Telescope Compact Array (ATCA) observations, of a 1 degrees x 1 degrees field centred on Centaurus A. As well as detecting the inner lobes of the active galactic nucleus (AGN) jet and counterjet, we have found two clouds, bright at submillimetre wavelengths, similar to 15 kpc from the centre of Cen A that are co-aligned with the jets. Flux measurements at Herschel wavelengths have proved vital in constraining fits to the spectral energy distributions (SEDs). The clouds are well fitted by a single-temperature, modified blackbody spectrum (beta= 2) indicating that we are looking at two cold dust clouds on the outskirts of Cen A. The temperature and masses of the clouds are K, K; , and the gas-dust ratio for both clouds is similar to 100. The measured values for the northern dust cloud are consistent with previous measurements from ISO while the southern cloud is a new submillimetre detection. The two dust clouds are located at the termini of the partial H i ring that surrounds Cen A which is also where the gas column density peaks. The Herschel survey encompasses the partial H i ring yet we find no evidence of dust emission in any other part of the ring. Assuming that the gasdust ratio is the same in the rest of the ring, dust mass upper limits in the H i ring are consistent with low column density dust being present but falling below the SPIRE detection limit. We have discussed the origin of these clouds and various possible heating mechanisms. The observations favour a scenario in which the gas and dust were once part of a late-type galaxy, which has since merged with Cen A. The dominant heating mechanism which adequately explains the observed temperatures in both clouds is heating from the evolved stellar population within Cen A.

We examined variations in the 160/250 and 250/350 micron surface brightness ratios within 24 nearby (=250 microns (and sometimes at >=160 microns) originates from dust heated by the older stellar population. In the rest of the sample, either the results are indeterminate or both of these stellar populations may contribute equally to the global dust heating. The observed variations in dust heating mechanisms does not necessarily match what has been predicted by dust emission and radiative transfer models, which could lead to overestimated dust temperatures, underestimated dust masses, false detections of variability in dust emissivity, and inaccurate star formation rate measurements., Accepted for publication in MNRAS

Interstellar dust in galaxies can be traced either through its extinction effects on the star light, or through its thermal emission at infrared wavelengths. Recent radiative transfer studies of several nearby edge-on galaxies have found an apparent inconsistency in the dust energy balance: the radiative transfer models that successfully explain the optical extinction underestimate the observed fluxes by an average factor of three. We investigate the dust energy balance for IC4225 and NGC5166, two edge-on spiral galaxies observed by the Herschel Space Observatory in the frame of the H-ATLAS survey. We start from models which were constrained from optical data and extend them to construct the entire spectral energy distribution of our galaxies. These predicted values are subsequently compared to the observed far-infrared fluxes. We find that including a young stellar population in the modelling is necessary as it plays a non-negligible part in the heating of the dust grains. While the modelling approach for both galaxies is nearly identical, we find two very different results. As is often seen in other edge-on spiral galaxies, the far-infrared emission of our radiative transfer model of IC4225 underestimates the observed fluxes by a factor of about three. For NGC5166 on the other hand, we find that both the predicted spectral energy distribution as well as the simulated images match the observations particularly well. We explore possible reasons for this difference and conclude that it is unlikely that one single mechanism is the cause of the dust energy balance problem in spiral galaxies. We discuss the different approaches that can be considered in order to get a conclusive answer on the origin this discrepancy., 12 pages, 4 figures, accepted for publication in MNRAS

We discuss the panchromatic properties of 99 088 galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 1 'main' spectroscopic sample ( a flux-limited sample for 1360 deg(2)). These galaxies are positionally matched to sources detected by ROSAT, Galaxy Evolution Explorer (GALEX), two-Micron All-Sky Survey (2MASS), Infrared Astronomical Satellite ( IRAS), Green Bank GB6 survey ( GB6), Faint Images of the Radio Sky at Twenty-centimetres ( FIRST), NRAO VLA Sky Survey (NVSS) and Westerbork Northern Sky Survey (WENSS). The matching fraction varies from