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We examine the far-infrared (FIR) properties of a sample of 5391 optically selected QSOs in the 0.5 < z < 2.65 redshift range down to log [ν L ν, 2500(erg s−1)] > 44.7, using SPIRE data from Herschel -ATLAS. We split the sample in a grid of 74 luminosity–redshift bins and compute the average optical–IR spectral energy distribution (SED) in each bin. By normalizing an intrinsic active galactic nucleus (AGN) template to the AGN optical power (at 5100 Å), we decompose the total IR emission (L IR; 8–1000 µm) into an AGN (L IR, AGN) and star-forming component (L IR, SF). We find that the AGN contribution to L IR increases as a function of AGN power, manifesting as a reduction of the 'FIR bump' in the average QSO SEDs. We note that L IR, SF does not correlate with AGN power; the mean star formation rates (SFRs) of AGN host galaxies are a function of redshift only and they range from ∼6 M⊙ yr−1 at z ∼ 0 to a plateau of ≲ 200 M⊙ yr−1 at z ∼ 2.6. Our results indicate that the accuracy of FIR emission as a proxy for SFR decreases with increasing AGN luminosity. We show that, at any given redshift, observed trends between IR luminosity (whether monochromatic or total) and AGN power (in the optical or X-rays) can be explained by a simple model which is the sum of two components: (i) the IR emission from star formation, uncorrelated with AGN power and (ii) the IR emission from AGN, directly proportional to AGN power in the optical or X-rays. [ABSTRACT FROM AUTHOR]

We describe a far-infrared survey of the Coma cluster and the galaxy filament it resides within. Our survey covers an area of ~150 deg² observed by Herschel H-ATLAS (Herschel Astrophysical Terahertz Large Area Survey) in five bands at 100, 160, 250, 350 and 500 μm. The SDSS spectroscopic survey (mr ≤ 17.8) is used to define an area (within the virial radius) and redshift selected (4268 < v < 9700 km s-1) sample of 744 Coma cluster galaxies - the Coma Cluster Catalogue. For comparison, we also define a sample of 951 galaxies in the connecting filament - the Coma Filament Catalogue. The optical positions and parameters are used to define appropriate apertures to measure each galaxy's far-infrared emission. We have detected 99 of 744 (13 per cent) and 422 of 951 (44 per cent) of the cluster and filament galaxies in the SPIRE 250 μm band. We consider the relative detection rates of galaxies of different morphological types finding that it is only the S0/Sa population that shows clear differences between the cluster and filament. We find no differences between the dust masses and temperatures of cluster and filament galaxies with the exception of early-type galaxy dust temperatures, which are significantly hotter in the cluster than in the filament (X-ray heating?). From a chemical evolution model, we find no evidence for different evolutionary processes (gas loss or infall) between galaxies in the cluster and filament. [ABSTRACT FROM AUTHOR]

We present the Herschel Extragalactic Legacy Project (HELP). This project collates, curates, homogenizes, and creates derived data products for most of the premium multiwavelength extragalactic data sets. The sky boundaries for the first data release cover 1270 deg2 defined by the Herschel SPIRE extragalactic survey fields; notably the Herschel Multi-tiered Extragalactic Survey (HerMES) and the Herschel Atlas survey (H-ATLAS). Here, we describe the motivation and principal elements in the design of the project. Guiding principles are transparent or 'open' methodologies with care for reproducibility and identification of provenance. A key element of the design focuses around the homogenization of calibration, meta data, and the provision of information required to define the selection of the data for statistical analysis. We apply probabilistic methods that extract information directly from the images at long wavelengths, exploiting the prior information available at shorter wavelengths and providing full posterior distributions rather than maximum-likelihood estimates and associated uncertainties as in traditional catalogues. With this project definition paper, we provide full access to the first data release of HELP; Data Release 1 (DR1), including a monolithic map of the largest SPIRE extragalactic field at 385 deg2 and 18 million measurements of PACS and SPIRE fluxes. We also provide tools to access and analyse the full HELP data base. This new data set includes far-infrared photometry, photometric redshifts, and derived physical properties estimated from modelling the spectral energy distributions over the full HELP sky. All the software and data presented is publicly available. [ABSTRACT FROM AUTHOR]

A correction to the article "Submillimetre photometry of 323 nearby galaxies from the Herschel Reference Survey" that was published in a previous issue of the journal is presented.

The Herschel Reference Survey (HRS) is a guaranteed time Herschel key project aimed at studying the physical properties of the interstellar medium in galaxies of the nearby universe. This volume limited, K-band selected sample is composed of galaxies spanning the whole range of morphological types (from ellipticals to late-type spirals) and environments (from the field to the centre of the Virgo Cluster). We present flux density measurements of the whole sample of 323 galaxies of the HRS in the three bands of the Spectral and Photometric Imaging Receiver (SPIRE), at 250 μm, 350 μm and 500 μm. Aperture photometry is performed on extended galaxies and point spread function (PSF) fitting on timeline data for unresolved objects; we carefully estimate errors and upper limits. The flux densities are found to be in good agreement with those of the HeViCS and KINGFISH key projects in all SPIRE bands, and of the Planck consortium at 350 μm and 550 μm, for the galaxies in common. This submillimetre catalogue of nearby galaxies is a benchmark for the study of the dust properties in the local universe, giving the zero redshift reference for any cosmological survey. [ABSTRACT FROM AUTHOR]

Combining large-area optical quasar surveys with the new far-infrared (FIR) Herschel-ATLAS Data Release 1, we search for an observational signature associated with the minority of quasars possessing bright FIR luminosities. We find that FIR-bright quasars show broad C IV emission-line blueshifts in excess of that expected from the optical luminosity alone, indicating particularly powerful nuclear outflows. The quasars show no signs of having redder optical colours than the general ensemble of optically selected quasars, ruling out differences in line-of-sight dustwithin the host galaxies. We postulate that these objectsmay be caught in a special evolutionary phase, with unobscured, high black hole accretion rates and correspondingly strong nuclear outflows. The high FIR emission found in these objects is then either a result of star formation related to the outflow, or is due to dust within the host galaxy illuminated by the quasar. We are thus directly witnessing coincident small-scale nuclear processes and galaxy-wide activity, commonly invoked in galaxy simulations that rely on feedback from quasars to influence galaxy evolution. [ABSTRACT FROM AUTHOR]

We use new Band 3 CO(1-0) observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the physical conditions in the interstellar gas of a sample of 27 dusty main-sequence star-forming galaxies at 0:03 < z < 0:2 present in the Valparaíso ALMA Line Emission Survey (VALES). The sample is drawn from far-IR bright galaxies over ~160 deg2 in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), which is covered by high-quality ancillary data including Herschel [Cπ] 158 μm spectroscopy and far-infrared (FIR) photometry. The [Cπ] and CO(1-0) lines are both detected at >5σ in 26 sources. We find an average [Cπ] to CO(1-0) luminosity ratio of 3500 ± 1200 for our sample that is consistent with previous studies. Using the [Cπ], CO(1-0) and FIR measurements as diagnostics of the physical conditions of the interstellar medium, we compare these observations to the predictions of a photodissociation region (PDR) model to determine the gas density, surface temperature, pressure, and the strength of the incident far-ultraviolet (FUV) radiation field, G0, normalised to the Habing Field. The majority of our sample exhibit hydrogen densities of 4 < log n=cm³ < 5:5 and experience an incident FUV radiation field with strengths of 2 < logG0 < 3 when adopting standard adjustments. A comparison to galaxy samples at different redshifts indicates that the average strength of the FUV radiation field appears constant up to redshift z ~ 6:4, yet the neutral gas density increases as a function of redshift by a factor of ~100 from z = 0 to z = 0:2 that persists regardless of various adjustments to our observable quantities. Whilst this evolution could provide an explanation for the observed evolution of the star formation rate density with cosmic time, the result most likely arises from a combination of observational biases when using different suites of emission lines as diagnostic tracers of PDR gas. [ABSTRACT FROM AUTHOR]

We present the properties of the first 250 μm blind sample of nearby galaxies (15 < D < 46 Mpc) containing 42 objects from the Herschel Astrophysical Terahertz Large Area Survey. Herschel's sensitivity probes the faint end of the dust luminosity function for the first time, spanning a range of stellar mass (7.4 < M⋆ < 11.3 log10 M⊙), star formation activity (-11.8 < SSFR < -8.9 log10 yr-1), gas fraction (3-96 per cent), and colour (0.6 < FUV-KS < 7.0 mag). The median cold dust temperature is 14.6 K, colder than in the Herschel Reference Survey (18.5 K) and Planck Early Release Compact Source Catalogue (17.7 K). The mean dust-to-stellar mass ratio in our sample is higher than these surveys by factors of 3.7 and 1.8, with a dust mass volume density of (3.7 ± 0.7) × 105 M⊙ Mpc-3. Counter-intuitively, we find that the more dust rich a galaxy, the lower its UV attenuation. Over half of our dust-selected sample are very blue in FUV-KS colour, with irregular and/or highly flocculent morphology; these galaxies account for only 6 per cent of the sample's stellar mass but contain over 35 per cent of the dust mass. They are the most actively star-forming galaxies in the sample, with the highest gas fractions and lowest UV attenuation. They also appear to be in an early stage of converting their gas into stars, providing valuable insights into the chemical evolution of young galaxies. [ABSTRACT FROM AUTHOR]

We examined variations in the 160/250 and 250/350 μm surface brightness ratios within 24 nearby (<30 Mpc) face-on spiral galaxiesobserved with the Herschel Space Observatory to identify the heating mechanisms for dust emitting at these wavelengths. The analysis consisted of both qualitative and quantitative comparisons of the 160/250 and 250/350 μm ratios to Hα and 24 μm emission, which trace the light from star-forming regions, and 3.6 μm emission, which traces the light from the older stellar populations of the galaxies. We find broad variations in the heating mechanisms for the dust. In one subset of galaxies, we found evidence that emission at ≤160 μm (and in rare cases potentially at ≤350 μm) originates from dust heated by star-forming regions. In another subset, we found that the emission at ≥250 μm (and sometimes at ≥160 μm) 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 do 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. [ABSTRACT FROM AUTHOR]

We examine the relation between polycyclic aromatic hydrocarbon (PAH) emission at 8 μm and far-infrared emission from hot dust grains at 24 μm and from large dust grains at 160 and 250 μm in the nearby spiral galaxies NGC 2403 and M83 using data from the Spitzer Space Telescope and Herschel Space Observatory. We find that the PAH emission in NGC 2403 is better correlated with emission at 250 μm from dust heated by the diffuse interstellar radiation field (ISRF) and that the 8/250-μm surface brightness ratio is well correlated with the stellar surface brightness as measured at 3.6 μm. This implies that the PAHs in NGC 2403 are intermixed with cold large dust grains in the diffuse interstellar medium (ISM) and that the PAHs are excited by the diffuse ISRF. In M83, the PAH emission appears more strongly correlated with 160 μm emission originating from large dust grains heated by star-forming regions. However, the PAH emission in M83 is low where the 24-μm emission peaks within star-forming regions, and enhancements in the 8/160-μm surface brightness ratios appear offset relative to the dust and the star-forming regions within the spiral arms. This suggests that the PAHs observed in the 8 μm band are not excited locally within star-forming regions but either by light escaping non-axisymmetrically from star-forming regions or locally by young, non-photoionizing stars that have migrated downstream from the spiral density waves. The results from just these two galaxies show that PAHs may be excited by different stellar populations in different spiral galaxies. [ABSTRACT FROM PUBLISHER]

We use 10 387 galaxies from the Herschel Astrophysical TeraHertz Large Area Survey (H-ATLAS) to probe the far-infrared radio correlation (FIRC) of star-forming galaxies as a function of redshift, wavelength, and effective dust temperature. All of the sources in our 250 μm-selected sample have spectroscopic redshifts, as well as 1.4 GHz flux density estimates measured from the Faint Images of the Radio Sky at Twenty centimetres (FIRST) survey. This enables us to study not only individual sources, but also the average properties of the 250 μm-selected population using median stacking techniques. We find that individual sources detected at ≥5σ in both the H-ATLAS and FIRST data have logarithmic flux ratios (i.e. FIRC qλ parameters) consistent with previous studies of the FIRC. In contrast, the stacked values show larger qλ, suggesting excess far-IR flux density/luminosity in 250 μm-selected sources above what has been seen in previous analyses. In addition, we find evidence that 250 μm sources with warm dust spectral energy distributions have a larger 1.4 GHz luminosity than the cooler sources in our sample. Though we find no evidence for redshift evolution of the monochromatic FIRC, our analysis reveals significant temperature dependence. Whilst the FIRC is reasonably constant with temperature at 100 μm, we find increasing inverse correlation with temperature as we probe longer PACS and SPIRE wavelengths. These results may have important implications for the use of monochromatic dust luminosity as a star formation rate indicator in star-forming galaxies, and in the future, for using radio data to determine galaxy star formation rates. [ABSTRACT FROM AUTHOR]

We have constructed a sample of radio-loud and radio-quiet quasars from the Faint Images Radio Sky at Twenty-one centimetres and the Sloan Digital Sky Survey Data Release 7, over the Herschel-ATLAS Phase 1 area (9h, 12h and $14{^{h}_{.}}5$). Using a stacking analysis, we find a significant correlation between the far-infrared (FIR) luminosity and 1.4-GHz luminosity for radio-loud quasars. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution, while for radio-quiet quasars, no partial correlation is found. Using a single-temperature grey-body model, we find a general trend of lower dust temperatures in case of radio-loud quasars compared to radio-quiet quasars. Also, radio-loud quasars are found to have almost constant mean values of dust mass along redshift and optical luminosity bins. In addition, we find that radio-loud quasars at lower optical luminosities tend to have on average higher FIR and 250-μm luminosity with respect to radio-quiet quasars with the same optical luminosites. Even if we use a two-temperature grey-body model to describe the FIR data, the FIR luminosity excess remains at lower optical luminosities. These results suggest that powerful radio jets are associated with star formation especially at lower accretion rates. [ABSTRACT FROM AUTHOR]

Although it accounts only for a small fraction of the baryonic mass, dust has a profound impact on the physical processes at play in galaxies. Thus, to understand the evolution of galaxies, it is essential not only to characterize dust properties per se, but also in relation to global galaxy properties. To do so, we derive the dust properties of galaxies in a volume limited, K-band selected sample, the Herschel Reference Survey (HRS). We gather infrared photometric data from 8 m to 500 m from Spitzer, WISE, IRAS, and Herschel for all of the HRS galaxies. Draine & Li (2007, ApJ, 663, 866) models are fit to the data from which the stellar contribution has been carefully removed. We find that our photometric coverage is su cient to constrain all of the parameters of the Draine & Li models and that a strong constraint on the 20􀀀60 m range is mandatory to estimate the relative contribution of the photo-dissociation regions to the infrared spectral energy distribution (SED). The SED models tend to systematically underestimate the observed 500 m flux densities, especially for low-mass systems. We provide the output parameters for all of the galaxies, i.e., the minimum intensity of the interstellar radiation field, the fraction of polycyclic aromatic hydrocarbon (PAH), the relative contribution of PDR and evolved stellar population to the dust heating, the dust mass, and the infrared luminosity. For a subsample of gas-rich galaxies, we analyze the relations between these parameters and the main integrated properties of galaxies, such as stellar mass, star formation rate, infrared luminosity, metallicity, H and H-band surface brightness, and the far-ultraviolet attenuation. A good correlation between the fraction of PAH and the metallicity is found, implying a weakening of the PAH emission in galaxies with low metallicities and, thus, low stellar masses. The intensity of the diffuse interstellar radiation field and the H-band and Hα surface brightnesses are correlated, suggesting that the diffuse dust component is heated by both the young stars in star-forming regions and the diffuse evolved population. We use these results to provide a new set of infrared templates calibrated with Herschel observations on nearby galaxies and a mean SED template to provide the z = 0 reference for cosmological studies. For the same purpose, we place our sample on the S FR􀀀M* diagram. The templates are compared to the most popular infrared SED libraries, enlightening a large discrepancy between all of them in the 20􀀀100m range. [ABSTRACT FROM AUTHOR]

We investigate the connection between dust and gas in the nearby edge-on spiral galaxy NGC 891, a target of the Very Nearby Galaxies Survey. High resolution Herschel PACS and SPIRE 70, 100, 160, 250, 350, and 500 μm images are combined with JCMT SCUBA 850 μm observations to trace the far-infrared/submillimetre spectral energy distribution (SED). Maps of the Hi 21 cm line and CO(J = 3−2) emission trace the atomic and molecular hydrogen gas, respectively. We fit one-component modified blackbody models to the integrated SED, finding a global dust mass of (8.5 ± 2.0) × 107 M⊙ and an average temperature of 23 ± 2 K, consistent with results from previous far-infrared experiments. We also fit one-component modified blackbody models to pixel-by-pixel SEDs to produce maps of the dust mass and temperature. The dust mass distribution correlates with the total stellar population as traced by the 3.6 μm emission. The derived dust temperature, which ranges from approximately 17 to 24 K, is found to correlate with the 24 μm emission. Allowing the dust emissivity index to vary, we find an average value of β = 1.9±0.3.We confirm an inverse relation between the dust emissivity spectral index and dust temperature, but do not observe any variation of this relationship with vertical height from the mid-plane of the disc. A comparison of the dust properties with the gaseous components of the ISM reveals strong spatial correlations between the surface mass densities of dust (Σdust) and the molecular hydrogen (ΣH2 ) and total gas surface densities (Σgas). These observations reveal the presence of regions of dense, cold dust that are coincident with peaks in the gas distribution and are associated with a molecular ring. Furthermore, the observed asymmetries in the dust temperature, the H2-to-dust ratio and the total gas-to-dust ratio hint that an enhancement in the star formation rate may be the result of larger quantities of molecular gas available to fuel star formation in the NE compared to the SW. Whilst the asymmetry likely arises from dust obscuration due to the geometry of the line-of-sight projection of the spiral arms, we cannot exclude that there is also an enhancement in the star formation rate in the NE part of the disc. [ABSTRACT FROM AUTHOR]

Context. We present new photometric data from our Herschel guaranteed time key programme, the Dwarf Galaxy Survey (DGS), dedicated to the observation of the gas and dust in low-metallicity environments. A total of 48 dwarf galaxies were observed with the PACS and SPIRE instruments onboard the Herschel Space Observatory at 70, 100, 160, 250, 350, and 500 μm. Aims. The goal of this paper is to provide reliable far-infrared (FIR) photometry for the DGS sample and to analyse the FIR/submillimetre (submm) behaviour of the DGS galaxies. We focus on a systematic comparison of the derived FIR properties (FIR luminosity, LFIR, dust mass, Mdust, dust temperature, T, emissivity index, β) with more metal-rich galaxies and investigate the detection of a potential submm excess. Methods. The data reduction method is adapted for each galaxy in order to derive the most reliable photometry from the final maps. The derived PACS flux densities are compared with the Spitzer MIPS 70 and 160 μm bands. We use colour-colour diagrams to analyse the FIR/submm behaviour of the DGS galaxies and modified blackbody fitting procedures to determine their dust properties. To study the variation in these dust properties with metallicity, we also include galaxies from the Herschel KINGFISH sample, which contains more metal-rich environments, totalling 109 galaxies. Results. The location of the DGS galaxies on Herschel colour-colour diagrams highlights the differences in dust grain properties and/or global environments of low-metallicity dwarf galaxies. The dust in DGS galaxies is generally warmer than in KINGFISH galaxies (TDGS ~ 32 K and TKINGFISH ~ 23 K). The emissivity index, β, is ~1.7 in the DGS, however metallicity does not make a strong effect on β. The proportion of dust mass relative to stellar mass is lower in low-metallicity galaxies: Mdust/Mstar ~ 0:02% for the DGS versus 0.1% for KINGFISH. However, per unit dust mass, dwarf galaxies emit about six times more in the FIR/submm than higher metallicity galaxies. Out of the 22 DGS galaxies detected at 500 μμm, about 41% present an excess in the submm beyond the explanation of our dust SED model, and this excess can go up to 150% above the prediction from the model. The excess mainly appears in lower metallicity galaxies (12 + log(O/H) . 8.3), and the strongest excesses are detected in the most metal-poor galaxies. However, we also stress the need for observations longwards of the Herschel wavelengths to detect any submm excess appearing beyond 500 μm. [ABSTRACT FROM AUTHOR]

Context. Edge-on spiral galaxies with prominent dust lanes provide us with an excellent opportunity to study the distribution and properties of the dust within them. The HEROES project was set up to observe a sample of seven large edge-on galaxies across various wavelengths for this investigation. Aims. Within this first paper, we present the Herschel observations and perform a qualitative and quantitative analysis on them, and we derive some global properties of the far infrared and submillimetre emission. Methods. We determine horizontal and vertical profiles from the Herschel observations of the galaxies in the sample and describe the morphology. Modified black-body fits to the global fluxes, measured using aperture photometry, result in dust temperatures and dust masses. The latter values are compared to those that are derived from radiative transfer models taken from the literature. Results. On the whole, our Herschel flux measurements agree well with archival values. We find that the exponential horizontal dust distribution model often used in the literature generally provides a good description of the observed horizontal profiles. Three out of the seven galaxies show signatures of extended vertical emission at 100 and 160 μm at the 5σ level, but in two of these it is probably due to deviations from an exactly edge-on orientation. Only for NGC4013, a galaxy in which vertically extended dust has already been detected in optical images, we can detect vertically extended dust, and the derived scaleheight agrees with the value estimated through radiative transfer modelling. Our analysis hints at a correlation between the dust scaleheight and its degree of clumpiness, which we infer from the difference between the dust masses as calculated from modelling of optical data and from fitting the spectral energy distribution of Herschel datapoints. [ABSTRACT FROM AUTHOR]

Aims. We examine whether dust mass can trace the total or molecular gas mass in late-type Virgo cluster galaxies, and how the environment affects the dust-to-gas ratio and the molecular fraction. Methods. Using the far-infrared emission, as observed by the Herschel Virgo Cluster Survey (HeViCS), and the integrated HI 21-cm and CO J = 1-0 line brightness, we infer the dust and total gas mass for a magnitude limited sample of 35 metal rich spiral galaxies. Environmental disturbances on each galaxy are considered by means of the HI deficiency parameter. Results. The CO flux correlates tightly and linearly with far-infrared fluxes observed by Herschel, especially with the emission at 160, 250 and 350 μm. Molecules in these galaxies are more closely related to cold dust rather than to dust heated by star formation or to optical/NIR brightness. We show that dust mass establishes a stronger correlation with the total gas mass than with the atomic or molecular component alone. The correlation is non-linear since lower mass galaxies have a lower dust-to-gas ratio. The dust-to-gas ratio increases as the HI deficiency increases, but in highly HI deficient galaxies it stays constant. Dust is in fact less affected than atomic gas by weak cluster interactions, which remove most of the HI gas from outer and high latitudes regions. Highly disturbed galaxies, in a dense cluster environment, can instead loose a considerable fraction of gas and dust from the inner regions of the disk keeping constant the dust-to-gas ratio. There is evidence that the molecular phase is also quenched. This quencing becomes evident by considering the molecular gas mass per unit stellar mass. Its amplitude, if confirmed by future studies, highlights that molecules are missing in Virgo HI deficient spirals, but to a somewhat lesser extent than dust. [ABSTRACT FROM AUTHOR]

ABSTRACT We examine the dust and gas properties of the nearby, barred galaxy M83, which is part of the Very Nearby Galaxy Survey. Using images from the Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging REceiver (SPIRE) instruments of Herschel, we examine the dust temperature and dust mass surface density distribution. We find that the nuclear, bar and spiral arm regions exhibit higher dust temperatures and masses compared to interarm regions. However, the distributions of dust temperature and mass are not spatially coincident. Assuming a trailing spiral structure, the dust temperature peaks in the spiral arms lie ahead of the dust surface density peaks. The dust mass surface density correlates well with the distribution of molecular gas as traced by CO ( J= 3→2) images (James Clerk Maxwell Telescope) and the star formation rate as traced by Hα with a correction for obscured star formation using 24- μm emission. Using H i images from The H i Nearby Galaxy Survey (THINGS) to trace the atomic gas component, we make total gas mass surface density maps and calculate the gas-to-dust ratio. We find a mean gas-to-dust ratio of 84 ± 4 with higher values in the inner region assuming a constant CO-to-H2 conversion factor. We also examine the gas-to-dust ratio using CO-to-H2 conversion factor that varies with metallicity. [ABSTRACT FROM AUTHOR]

ABSTRACT We present measurements of the mean mid-infrared to submillimetre flux densities of massive ( M★≳ 1011 M⊙) galaxies at redshifts 1.7 < z < 2.9, obtained by stacking positions of known objects taken from the GOODS NICMOS Survey (GNS) catalogue on maps at 24 m ( Spitzer/MIPS); 70, 100 and 160 m ( Herschel/PACS); 250, 350 and 500 m ( BLAST); and 870 m (LABOCA). A modified blackbody spectrum fit to the stacked flux densities indicates a median [interquartile] star formation rate (SFR) of SFR = 63[48, 81] M⊙ yr−1. We note that not properly accounting for correlations between bands when fitting stacked data can significantly bias the result. The galaxies are divided into two groups, disc-like and spheroid-like, according to their Sérsic indices, n. We find evidence that most of the star formation is occurring in n≤ 2 (disc-like) galaxies, with median [interquartile] SFR = 122[100, 150] M⊙ yr−1, while there are indications that the n > 2 (spheroid-like) population may be forming stars at a median [interquartile] SFR = 14[9, 20] M⊙ yr−1, if at all. Finally, we show that star formation is a plausible mechanism for size evolution in this population as a whole, but find only marginal evidence that it is what drives the expansion of the spheroid-like galaxies. [ABSTRACT FROM AUTHOR]

Aims. It is still not understood why star-forming galaxies deviate from the ultraviolet colour-attenuation relation of starburst galaxies. Previous work and models hint that the role of the shape of the attenuation curve and the age of stellar populations play an important role. In this paper we aim at understanding the fundamental reasons for this deviation. Methods. We have used the CIGALE spectral energy distribution fitting code to model the far ultraviolet to the far infrared emission of a set of 7 reasonably face-on spiral galaxies from the Herschel Reference Survey on a pixel-by-pixel basis. We explored the influence of a wide range of physical parameters to quantify their influence and impact on any accurate determination of the attenuation from the ultraviolet colour and to discover why normal galaxies do not follow the same relation as starburst galaxies. Results. We have found that the deviation from the starburst relation can be explained best by intrinsic ultraviolet colour differences between different regions in galaxies. Variations in the shape of the attenuation curve can also play a secondary role. Standard age estimators of the stellar populations, such as the D4000 index or the birthrate parameter, prove to be poor predictors of the intrinsic ultraviolet colour. These results are also retrieved on a sample of 58 spiral galaxies drawn from the Herschel Reference Survey sample when considering their integrated fluxes. Conclusions. When correcting the emission of normal star-forming galaxies for the attenuation, it is crucial to consider possible variations in both the intrinsic ultraviolet colour of the stellar populations and the shape of the attenuation curve. [ABSTRACT FROM AUTHOR]

The article focuses on a study that compares the results for dust-to-stellar ratios and metallicity for two Herschel samples. The study is undertaken through the computation of stellar masses. The results of the study show that stellar masses are constantly estimated for both samples particularly in observed correlations.

An abstract of the article "Submillimetre photometry of 323 nearby galaxies from the Herschel Reference Survey," by L. Ciesla and colleagues is presented.