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A. Feltre et al., In this work, we explore the impact of the presence of an active galactic nucleus (AGN) on the mid- and far-infrared (IR) properties of galaxies as well as the effects of simultaneous AGN and starburst activity in the same galaxies. To do this, we apply a multicomponent, multiband spectral synthesis technique to a sample of 250 μm selected galaxies of the Herschel Multitiered Extragalactic Survey (HerMES), with Infrared Spectrograph (IRS) spectra available for all galaxies. Our results confirm that the inclusion of the IRS spectra plays a crucial role in the spectral analysis of galaxies with an AGN component improving the selection of the best-fitting hot dust (torus) model. We find a correlation between the obscured star formation rate, SFRIR, derived from the IR luminosity of the starburst component, and SFRPAH, derived from the luminosity of the PAH features, LPAH, with SFRFIR taking higher values than SFRPAH. The correlation is different for AGN- and starburst-dominated objects. The ratio of LPAH to that of the starburst component, LPAH/LSB, is almost constant for AGN-dominated objects but decreases with increasing LSB for starburst-dominated objects. SFRFIR increases with the accretion luminosity, Lacc, with the increase less prominent for the very brightest, unobscured AGN-dominated sources. We find no correlation between the masses of the hot (AGN-heated) and cold (starburstheated) dust components. We interpret this as a non-constant fraction of gas driven by the gravitational effects to the AGN while the starburst is ongoing. We also find no evidenceof the AGN affecting the temperature of the cold dust component, though this conclusion is mostly based on objects with a non-dominant AGN component. We conclude that our findings do not provide evidence that the presence of AGN affects the star formation process in the host galaxy, but rather that the two phenomena occur simultaneously over a wide range of luminosities. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society., This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC, UKSA (UK); and NASA (USA).

We present a new SED-fitting based routine for redshift determination that is optimised for mid-infrared (MIR) low-resolution spectroscopy. Its flexible template scaling increases the sensitivity to slope changes and small scale features in the spectrum, while a new selection algorithm called Maximum Combined Pseudo-Likelihood (MCPL) provides increased accuracy and a lower number of outliers compared to the standard maximum-likelihood (ML) approach. Unlike ML, MCPL searches for local (instead of absolute) maxima of a 'pseudo-likelihood' (PL) function, and combines results obtained for all the templates in the library to weed out spurious redshift solutions. The capabilities of MCPL are demonstrated by comparing its results to those of regular ML and to the optical spectroscopic redshifts of a sample of 491 Spitzer/IRS spectra from sources at 0 0.02) is 14% for MCPL and 22% for ML. chi^2 values for ML solutions are found to correlate with the SNR of the spectra, but not with redshift accuracy. By contrast, the peak value of the normalised combined PL (gamma) is found to provide a good indication on the reliability of the MCPL solution for individual sources. The accuracy and reliability of the redshifts depends strongly on the MIR SED. Sources with significant polycyclic aromatic hydrocarbon emission obtain much better results compared to sources dominated by AGN continuum. Nevertheless, for a given gamma the frequency of accurate solutions and outliers is largely independent on their SED type. This reliability indicator for MCPL solutions allows to select subsamples with highly reliable redshifts. In particular, a gamma>0.15 threshold retains 79% of the sources with dz/(1+z)

We investigate the evolutionary connection between local IR-bright galaxies ($\log L_{\rm IR}\ge 11.4\,L_\odot$) and quasars. We use high angular resolution ($\sim$ 0.3-0.4 arcsec $\sim$ few hundred parsecs) $8-13\,\mu$m ground-based spectroscopy to disentangle the AGN mid-IR properties from those of star formation. The comparison between the nuclear $11.3\,\mu$m PAH feature emission and that measured with Spitzer/IRS indicates that the star formation is extended over a few kpc in the IR-bright galaxies. The AGN contribution to the total IR luminosity of IR-bright galaxies is lower than in quasars. Although the dust distribution is predicted to change as IR-bright galaxies evolve to IR-bright quasars and then to optical quasars, we show that the AGN mid-IR emission of all the quasars in our sample is not significantly different. In contrast, the nuclear emission of IR-bright galaxies with low AGN contributions appears more heavily embedded in dust although there is no clear trend with the interaction stage or projected nuclear separation. This suggests that the changes in the distribution of the nuclear obscuring material may be taking place rapidly and at different interaction stages washing out the evidence of an evolutionary path. When compared to normal AGN, the nuclear star formation activity of quasars appears to be dimming whereas it is enhanced in some IR-bright nuclei, suggesting that the latter are in an earlier star-formation dominated phase., Comment: Accepted for publication in MNRAS

The rest-frame near infrared (NIR) is a key spectral range for understanding the physics of AGN, but progress has been hindered by the difficulty in defining the NIR spectrum of the accretion disk and removing contamination from stellar emission in the host galaxy. In this talk I will present the analysis of a sample of 85 luminous (L3µm>10^45.5 erg/s) quasars with rest-frame NIR spectroscopy from AKARI and Spitzer/IRS. Their high luminosity allows a direct determination of the NIR shape of the quasar spectrum clean from host galaxy emission. We find that the entire UV-to-MIR SED can be accurately reproduced with a semi-empirical disk+dust model that uses a single template for the accretion disk and two blackbody components (hot and warm) for the dust. The observed diversity in individual SEDs can be accounted for by varying levels of extinction affecting the disk component and differences in the relative luminosities of the disk and dust components. We present a new quasar template [0.1-10µm] as well as separate templates for the disk and dust components, and conclude that previous templates based on less luminous quasars suffer from contamination by stellar emission in the host galaxy, which accounts for up to ~30% of the flux at 1µm. We also perform the first ever measurement of the Paschen_α emission in a large sample of luminous quasars and find that the Paschen_α to optical continuum luminosity ratio is boosted in our sample compared to less luminous quasars.

We present results on low-resolution mid-infrared (MIR) spectra of 70 IR-luminous galaxies obtained with the infrared spectrograph (IRS) onboard Spitzer. We selected sources from the European Large Area Infrared Survey with S 15 > 0.8 mJy and photometric or spectroscopic z > 1. About half of the samples are quasi-stellar objects (QSOs) in the optical, while the remaining sources are galaxies, comprising both obscured active galactic nuclei (AGN) and starbursts. Redshifts were obtained from optical spectroscopy, photometric redshifts and the IRS spectra. The later turn out to be reliable for obscured and/or star-forming sources, thus becoming an ideal complement to optical spectroscopy for redshift estimation. We estimate monochromatic luminosities at several rest-frame wavelengths, equivalent widths and luminosities for the polycyclic aromatic hydrocarbon (PAH) features, and strength of the silicate feature in individual spectra. We also estimate integrated 8-1000 μm IR luminosities via spectral energy distribution fitting to MIR and far-IR (FIR) photometry from the Spitzer Wide-Area Infrared Extragalactic survey and the MIR spectrum. Based on these measurements, we classify the spectra using well-known IR diagnostics, as well as a new one that we propose, into three types of source: those dominated by an unobscured AGN, mostly corresponding to optical quasars (QSOs), those dominated by an obscured AGN and starburst-dominated sources. Starbursts concentrate at z ∼ 0.6-1.0 favoured by the shift of the 7.7-μm PAH band into the selection 15-μm band, while AGN spread over the 0.5 < z < 3.1 range. Star formation rates (SFR) are estimated for individual sources from the luminosity of the PAH features. An estimate of the average PAH luminosity in QSOs and obscured AGN is obtained from the composite spectrum of all sources with reliable redshifts. The estimated mean SFR in the QSOs is 50-100 M ⊙ yr -1, but the implied FIR luminosity is 3-10 times lower than that obtained from stacking analysis of the FIR photometry, suggesting destruction of the PAH carriers by energetic photons from the AGN. The SFR estimated in obscured AGN is two to three times higher than in QSOs of similar MIR luminosity. This discrepancy might not be due to luminosity effects or selection bias alone, but could instead indicate a connection between obscuration and star formation. However, the observed correlation between silicate absorption and the slope of the NIR to MIR spectrum is compatible with the obscuration of the AGN emission in these sources being produced in a dust torus. © 2009 RAS.

We present the distributions of the geometrical covering factors of the dusty tori (f2) of active galactic nuclei (AGNs) using an X-ray selected complete sample of 227 AGNs drawn from the Bright Ultra-hard XMM-Newton Survey. The AGNs have z from 0.05 to 1.7, 2-10 keV luminosities between 1042 and 1046 erg s-1, and Compton-thin X-ray absorption. Employing data from UKIDSS, 2MASS, and the Wide-field Infrared Survey Explorer in a previous work, we determined the rest-frame 1-20 ¿m continuum emission from the torus, which we model here with the clumpy torus models of Nenkova et al. Optically classified type 1 and type 2 AGNs are intrinsically different, with type 2 AGNs having, on average, tori with higher f2 than type 1 AGNs. Nevertheless, ~20% of type 1 AGNs have tori with large covering factors, while ~23%-28% of type 2 AGNs have tori with small covering factors. Low f2 are preferred at high AGN luminosities, as postulated by simple receding torus models, although for type 2 AGNs the effect is certainly small. f2 increases with the X-ray column density, which implies that dust extinction and X-ray absorption take place in material that share an overall geometry and most likely belong to the same structure, the putative torus. Based on our results, the viewing angle, AGN luminosity, and also f2 determine the optical appearance of an AGN and control the shape of the rest-frame ~1-20 ¿m nuclear continuum emission. Thus, the torus geometrical covering factor is a key ingredient of unification schemes., Funding for SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. S.M., F.J.C., X.B., A.H.-C., and A.A.-H. acknowledge financial support by the Spanish Ministry of Economy and Competitiveness through grants AYA2012-31447, which is partly funded by the FEDER programme, and AYA2015-64346-C2-1-P. S.M., F.J.C. and A. A.-H. acknowledge financial support from the ARCHES project (7th Framework of the European Union, No. 313146). C.R.A. acknowledges financial support from the Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-327934). A.A.R. acknowledges financial support through the Ramón y Cajal fellowship and projects AYA2014-60476-P and ConsoliderIngenio 2010 CSD2009-00038 from the Spanish Ministry of Economy and Competitiveness.

We present subarcsecond resolution mid-infrared (MIR) images obtained with 8-10 m-class ground-based telescopes of a complete volume-limited (DL, 27 pages, 12 figures, accepted by MNRAS

We present far-infrared (FIR) $70-500\,\mu$m imaging observations obtained with Herschel/PACS and SPIRE of 33 nearby (median distance of 30 Mpc) Seyfert galaxies from the Revised Shapley-Ames (RSA) catalogue. We obtain the FIR nuclear ($r=1\,$kpc and $r=2\,$kpc) and integrated spectral energy distributions (SEDs). We estimate the unresolved nuclear emission at 70 $\mu$m and we fit the nuclear and integrated FIR SEDs with a grey body model. We find that the integrated FIR emission of the RSA Seyferts in our sample is dominated by emission from the host galaxy, with dust properties similar to those of normal galaxies (non AGN). We use four criteria to select galaxies whose nuclear $70\,\mu$m emission has a significant AGN contribution: (1) elevated 70/160 $\mu$m flux ratios, (2)spatially resolved, high dust temperature gradient, (3) $70\,\mu$m excess emission with respect to the fit of the FIR SEDs with a grey body, and (4) excess of nuclear SFR obtained from $70\,\mu$m over SFR from mid-infrared indicators. 16 galaxies (48 per cent of the initial sample) satisfy at least one of these conditions, whereas 10 satisfy half or more. After careful examination of these, we select six bona fide candidates (18 per cent of the initial sample) and estimate that $\sim 40-70$ per cent of their nuclear ($r=1-2\,$kpc) $70\,\mu$m emission is contributed by dust heated by the AGN., Comment: 20 pages, 16 figures, 12 tables, Accepted for publication in MNRAS

et al., We present an analysis of the nuclear infrared (IR, 1.6-18 μm) emission of the ultraluminous IR galaxy UGC5101 to derive the properties of its active galactic nucleus (AGN) and its obscuring material. We use new mid-IR high angular resolution (0.3-0.5 arcsec) imaging using the Si-2 filter (λ = 8.7 μm) and 7.5-13 μm spectroscopy taken with CanariCam (CC) on the 10.4 m Gran Telescopio CANARIAS. We also use archival Hubble Space Telescope/NICMOS and Subaru/COMICS imaging and Spitzer/IRS spectroscopy. We estimate the near- and mid-IR unresolved nuclear emission by modelling the imaging data with GALFIT. We decompose the Spitzer/IRS and CC spectra using a power-law component, which represents the emission due to dust heated by the AGN, and a starburst component, both affected by foreground extinction. We model the resulting unresolved near- and mid-IR, and the starburst subtracted CC spectrum with the CLUMPY torus models of Nenkova et al. The derived geometrical properties of the torus, including the large covering factor and the high foreground extinction needed to reproduce the deep 9.7 μm silicate feature, are consistent with the lack of strong AGN signatures in the optical.We derive an AGN bolometric luminosity L ~ 1.9 × 10 erg s that is in good agreement with other estimates in the literature., This work has been partly supported by Mexican CONACyT under research grant CB-2011-01-167291. MMP acknowledges support by the CONACyT PhD fellowship programme. AA-H and AH-C acknowledge financial support from the Spanish Plan Nacional de Astronomía y Astrofísica under grant AYA2012-31447, which is partly funded by the FEDER programme, and the Universidad de Cantabria through the Augusto G. Linares programme. CRA is supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-327934). IG-B ackowledges financial support from the Instituto de Astrofísica de Canarias through Fundacion La Caixa and from the Spanish Ministry of Science and Innovation (MICINN) through project PN AYA2013-47742-c4-2-P (Estallidos).

We present a panoramic atlas of Spitzer/IRS spectra of extragalactic sources collected from the recent literature, with value added measurements of their spectral features obtained in a homogeneous and concise manner. The atlas covers the full spectrum of the extragalactic universe and includes star forming galaxies, obscured and unobscured active galaxies, luminous and ultra-luminous infrared galaxies, and hybrid objects. Measured features such as the polycyclic aromatic hydrocarbons, the strength of the silicates in emission or absorption around 9.7 micron, rest-frame monochromatic luminosities or colours, combined with measurements derived from spectral decomposition, are used to establish diagnostics that allow for classification of sources, based on their infrared properties alone. Average templates of the various classes are also derived. The full atlas with the value added measurements and ancillary archival data are publicly available at this http URL, with full references to the original data.

We derive the properties of dusty tori in active galactic nuclei from the comparison of observed spectral energy distributions (SEDs) of SDSS quasars and a precomputed grid of torus models. The observed SEDs comprise SDSS photometry, Two-Micron All-Sky Survey J, H and K data, whenever available, and mid-infrared (mid-IR) data from the Spitzer Wide-area InfraRed Extragalactic Survey. The adopted model is that of Fritz, Franceschini & Hatziminaoglou. The fit is performed by standard χ2-minimization; the model, however, can be a multicomponent comprising a stellar and a starburst component, whenever necessary. Models with low equatorial optical depth, τ9.7, were allowed as well as ‘traditional’ models with τ9.7≥ 1.0, corresponding to AV≥ 22 and the results were compared. Fits using high optical depth tori models only produced dust more compactly distributed than in the configuration where all τ9.7 models were permitted. Tori with decreasing dust density with the distance from the centre were favoured while there was no clear preference for models with or without angular variation of the dust density. The computed outer radii of the tori are of some tens of parsecs large but can reach, in a few cases, a few hundreds of parsecs. The mass of dust, MDust, and IR luminosity, LIR, integrated in the wavelength range between 1 and 1000 μm, do not show significant variations with redshift, once the observational biases are taken into account. Objects with 70-μm detections, representing 25 per cent of the sample, are studied separately and the starburst contribution (whenever present) to the IR luminosity can reach, in the most extreme but very few cases, 80 per cent.

We present an atlas of mid-infrared (mid-IR) ~7.5-13 μm spectra of 45 local active galactic nuclei (AGN) obtained with CanariCam on the 10.4 m Gran Telescopio CANARIAS (GTC) as part of an ESO/GTC large programme. The sample includes Seyferts and other lowluminosity AGN (LLAGN) at a median distance of 35 Mpc and luminous AGN, namely PG quasars, (U)LIRGs, and radio galaxies (RG) at a median distance of 254 Mpc. To date, this is the largest mid-IR spectroscopic catalogue of local AGN at sub-arcsecond resolution (median 0.3 arcsec). The goal of this work is to give an overview of the spectroscopic properties of the sample. The nuclear 12 μm luminosities of the AGN span more than four orders of magnitude, νL ~ 3 × 10-10 erg s. In a simple mid-IR spectral index versus strength of the 9.7 μm silicate feature diagram most LLAGN, Seyfert nuclei, PG quasars, and RGs lie in the region occupied by clumpy torus model tracks. However, the mid-IR spectra of some might include contributions from other mechanisms. Most (U)LIRG nuclei in our sample have deeper silicate features and flatter spectral indices than predicted by these models suggesting deeply embedded dust heating sources and/or contribution from star formation. The 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature is clearly detected in approximately half of the Seyfert nuclei, LLAGN, and (U)LIRGs. While the RG, PG quasars, and (U)LIRGs in our sample have similar nuclear νL, we do not detect nuclear PAH emission in the RGs and PG quasars., AA-H acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) under the 2011 Severo Ochoa Programme MINECO SEV-2011-0187. AA-H and AH-C acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through grant AYA2012-31447, which is party funded by the FEDER programme, PE from grant AYA2012-31277, and LC from grant AYA2012-32295. CRA acknowledges financial support from the Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-327934). T.D-S. acknowledges support from ALMA-CONICYT project 31130005 and FONDECYT 1151239.

Pérez-González et al., We present the Survey for High-z Absorption Red and Dead Sources (SHARDS), an ESO/GTC Large Program carried out using the OSIRIS instrument on the 10.4 m Gran Telescopio Canarias (GTC). SHARDS is an ultra-deep optical spectro-photometric survey of the GOODS-N field covering 130 arcmin2 at wavelengths between 500 and 950 nm with 24 contiguous medium-band filters (providing a spectral resolution R ∿ 50). The data reach an AB magnitude of 26.5 (at least at a 3σ level) with sub-arcsec seeing in all bands. SHARDS' main goal is to obtain accurate physical properties of intermediate- and high-z galaxies using well-sampled optical spectral energy distributions (SEDs) with sufficient spectral resolution to measure absorption and emission features, whose analysis will provide reliable stellar population and active galactic nucleus (AGN) parameters. Among the different populations of high-z galaxies, SHARDS' principal targets are massive quiescent galaxies at z > 1, whose existence is one of the major challenges facing current hierarchical models of galaxy formation. In this paper, we outline the observational strategy and include a detailed discussion of the special reduction and calibration procedures which should be applied to the GTC/OSIRIS data. An assessment of the SHARDS data quality is also performed. We present science demonstration results on the detection and study of emission-line galaxies (star-forming objects and AGNs) at z = 0-5. We also analyze the SEDs for a sample of 27 quiescent massive galaxies with spectroscopic redshifts in the range 1.0 < z ≲ 1.4. We discuss the improvements introduced by the SHARDS data set in the analysis of their star formation history and stellar properties. We discuss the systematics arising from the use of different stellar population libraries, typical in this kind of study. Averaging the results from the different libraries, we find that the UV-to-MIR SEDs of the massive quiescent galaxies at z = 1.0-1.4 are well described by an exponentially decaying star formation history with scale Ï„ = 100-200 Myr, age around 1.5-2.0 Gyr, solar or slightly sub-solar metallicity, and moderate extinction, A(V) ∿ 0.5 mag. We also find that galaxies with masses above M* are typically older than lighter galaxies, as expected in a downsizing scenario of galaxy formation. This trend is, however, model dependent, i.e., it is significantly more evident in the results obtained with some stellar population synthesis libraries, and almost absent in others. © 2013. The American Astronomical Society. All rights reserved., We acknowledge support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2009-07723-E and AYA2009-10368. SHARDS has been funded by the Spanish MICINN/MINECO under the Consolider-Ingenio 2010 Program grant CSD2006-00070: First Science with the GTC. O.G.-M., C.M.-T., J.M.R.-E., and J.R.-Z. wish to acknowledge support from grant AYA2010-21887-C04-04. A.A.-H. and A.H.-C. acknowledge financial support from the Universidad de Cantabria through the Augusto G. Linares Program.

We present a study of galaxies showing mid-infrared variability in data taken in the deepest Spitzer/MIPS 24 μm surveys in the Great Observatory Origins Deep Survey South field. We divide the data set in epochs and subepochs to study the long-term (months–years) and the short-term (days) variability. We use a χ2-statistics method to select active galactic nucleus (AGN) candidates with a probability ≤1 per cent that the observed variability is due to statistical errors alone. We find 39 (1.7 per cent of the parent sample) sources that show long-term variability and 55 (2.2 per cent of the parent sample) showing short-term variability. That is, 0.03 sources × arcmin−2 for both, long-term and short-term variable sources. After removing the expected number of false positives inherent to the method, the estimated percentages are 1.0 and 1.4 per cent of the parent sample for the long term and short term, respectively. We compare our candidates with AGN selected in the X-ray and radio bands, and AGN candidates selected by their IR emission. Approximately, 50 per cent of the MIPS (Multiband Imaging Photometer for Spitzer) 24 μm variable sources would be identified as AGN with these other methods. Therefore, MIPS 24 μm variability is a new method to identify AGN candidates, possibly dust obscured and low-luminosity AGN, that might be missed by other methods. However, the contribution of the MIPS 24 μm variable identified AGN to the general AGN population is small (≤13 per cent) in GOODS-South., JG-G, AA-H, and AH-C acknowledge support from the Augusto G. Linares research programme of the Universidad de Cantabria and from the Spanish Plan Nacional through grant AYA2012-31447. PGP-G acknowledges support from MINECO grant AYA2012-31277.

We present a comprehensive study of the silicate features at 9.7 and 18 μm of a sample of almost 800 active galactic nuclei (AGNs) with available spectra from the Spitzer InfraRed Spectrograph (IRS). We measure the strength of the silicate feature at 9.7 μm, S , before and after subtracting the host galaxy emission from the IRS spectra. The number of type 1 and 2 AGNs with the feature in emission increases by 20 and 50%, respectively, once the host galaxy is removed, while 35% of objects with this feature originally in absorption exhibit it in even deeper absorption. The peak of S9.7, λpeak, has a bimodal distribution when the feature is in emission, with about 65% of the cases showing λpeak > 10.2 μm. Silicates can appear in emission in objects with mid-infrared (MIR) luminosity spanning over six orders of magnitude. The derived distributions of the strength of the silicate features at 9.7 and 18 μm provide a solid test bed for modeling the dust distribution in AGNs. Clumpiness is needed in order to produce absorption features in unobscured AGNs and can also cause the silicates to be in absorption at 9.7 μm and in emission at 18 μm in type 1 sources. We find the >cosmic> silicates of Ossenkopf et al. to be more consistent with the observations than Draine's >astronomical> silicates. Finally, we discuss the possibility of a foreground absorber to explain the deep silicate absorption features in the MIR spectra of some type 2 AGNs., A.H.C. acknowledges funding from the Spanish Ministry of Economy and Competitiveness under grant AYA2012-31447, which is partly funded by the FEDER Program. A.F. acknowledges support from the ERC via an Advanced Grant under grant Agreement No. 321323-NEOGAL.

We have determined the relation between the AGN luminosities at rest-frame 6 μm associated with the dusty torus emission and at 2–10 keV energies using a complete, X-ray-flux-limited sample of 232 AGN drawn from the Bright Ultra-hard XMM-Newton Survey. The objects have intrinsic X-ray luminosities between 1042 and 1046 erg s−1 and redshifts from 0.05 to 2.8. The rest-frame 6 μm luminosities were computed using data from the Wide-field Infrared Survey Explorer and are based on a spectral energy distribution decomposition into AGN and galaxy emission. The best-fitting relationship for the full sample is consistent with being linear, L6 μm ∝ L0.99±0.032−10keVL2−10keV0.99±0.03, with intrinsic scatter, Δ log L6 μm ∼ 0.35 dex. The L6μm/L2−10keVL6μm/L2−10keV luminosity ratio is largely independent of the line-of-sight X-ray absorption. Assuming a constant X-ray bolometric correction, the fraction of AGN bolometric luminosity reprocessed in the mid-IR decreases weakly, if at all, with the AGN luminosity, a finding at odds with simple receding torus models. Type 2 AGN have redder mid-IR continua at rest-frame wavelengths, SM, FJC, XB, AH-C and AA-H acknowledge funding from the Spanish Ministry of Economy and Competitiveness under grant AYA2012-31447, which is partly funded by the FEDER programme. SM, FJC and AA-H acknowledge financial support from the ARCHES project (7th Framework of the European Union, no. 313146). AA-H acknowledges support from the Universidad de Cantabria through the Augusto G. Linares programme. AC, RDC and PS acknowledge financial support from the Italian Ministry of Education, Universities and Research (PRIN2010-2011, grant no. 2010NHBSBE) and from ASI (grant no. I/088/06/0).

et al., In this paper, we present a comprehensive analysis of star-forming galaxies (SFGs) at intermediate redshifts (z ∼ 1). We combine the ultra-deep optical spectro-photometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) with deep UV-to-FIR observations in the GOODS-N field. Exploiting two of the 25 SHARDS medium-band filters, F687W17 and F823W17, we select [O ii] emission line galaxies at z ∼ 0.84 and z ∼ 1.23 and characterize their physical properties. Their rest-frame equivalent widths (EW([O ii])), line fluxes, luminosities, star formation rates (SFRs), and dust attenuation properties are investigated. The evolution of EW([O ii]) closely follows the SFR density evolution of the universe, with a trend of EW([O ii]) (1 + z) up to redshift z ≃ 1, followed by a possible flattening. The SF properties of the galaxies selected on the basis of their [O ii] emission are compared with complementary samples of SFGs selected by their MIR and FIR emission, and also with a general mass-selected sample of galaxies at the same redshifts. We demonstrate observationally that the UVJ diagram (or, similarly, a cut in the specific SFR) is only partially able to distinguish the quiescent galaxies from the SFGs. The SFR-M relation is investigated for the different samples, yielding a logarithmic slope ∼1, in good agreement with previous results. The dust attenuations derived from different SFR indicators (UV(1600), UV(2800), [O ii], IR) are compared and show clear trends with respect to both the stellar mass and total SFR, with more massive and highly star-forming galaxies being affected by stronger dust attenuation., The work of A.C. is supported by the STARFORM Sinergia Project funded by the Swiss National Science Foundation, and also benefited from a MERAC Funding and Travel Award. P.G.P.-G. acknowledges support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2012-31277. A.V.G. acknowledges support from the ERC via an Advanced Grant under grant agreement no. 321323-NEOGAL. N.C. acknowledges support from the Spanish Ministry of Economy and Competitiveness under grant AYA2013-46724-P. A.A.H. and A.H.C. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through grant AYA2012-31447, which is partly funded by the FEDER program. A.J.C. is a Ramón y Cajal Fellow of the Spanish Ministry of Science and Innovation and acknowledges financial support from the Spanish Ministry of Economy and Competitiveness through grant AYA2012-30789, partly funded by the FEDER program.

We present the results of a morphological analysis of a small subset of the Spitzer Wide-Area Infrared Extragalactic survey (SWIRE) galaxy population. The analysis is based on public Advanced Camera for Surveys (ACS) data taken inside the SWIRE N1 field, which are the deepest optical high-resolution imaging available within the SWIRE fields as of today. Our reference sample includes 156 galaxies detected by both ACS and SWIRE. Among the various galaxy morphologies, we disentangle two main classes, spheroids (or bulge-dominated galaxies) and disc-dominated ones, for which we compute the number counts as a function of flux. We then limit our sample to objects with Infrared Array Camera (IRAC) fluxes brighter than 10 μJy, estimated ~90 per cent completeness limit of the SWIRE catalogues, and compare the observed counts to model predictions. We find that the observed counts of the spheroidal population agree with the expectations of a hierarchical model while a monolithic scenario predicts steeper counts. Both scenarios, however, underpredict the number of late-type galaxies. These observations show that the large majority (close to 80 per cent) of the 3.6- and 4.5-μm galaxy population, even at these moderately faint fluxes, is dominated by spiral and irregular galaxies or mergers.

We present a mid-infrared (MIR) analysis of 35 quasars with spectroscopic redshifts selected from the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE). We discuss their optical and MIR colors and show that these quasars occupy well-defined regions in MIR color-color space. We examine the issue of type 1 active galactic nuclei candidate selection in detail and propose new selection methods based on MIR colors. The available multiband data allow us to construct two new, well-sampled quasar templates, covering wavelengths from the ultraviolet to the MIR.

A. Alonso-Herrero et al., We present Gran Telescopio CANARIAS CanariCam 8.7 μm imaging and 7.5-13 μm spectroscopy of six local systems known to host an active galactic nucleus (AGN) and have nuclear star formation. Our main goal is to investigate whether the molecules responsible for the 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature are destroyed in the close vicinity of an AGN. We detect 11.3 μm PAH feature emission in the nuclear regions of the galaxies as well as extended PAH emission over a few hundred parsecs. The equivalent width (EW) of the feature shows a minimum at the nucleus but increases with increasing radial distances, reaching typical star-forming values a few hundred parsecs away from the nucleus. The reduced nuclear EWs are interpreted as due to increased dilution from the AGN continuum rather than destruction of the PAH molecules. We conclude that at least those molecules responsible for the 11.3 μm PAH feature survive in the nuclear environments as close as 10 pc from the AGN and for Seyfert-like AGN luminosities. We propose that material in the dusty tori, nuclear gas discs, and/or host galaxies of AGN is likely to provide the column densities necessary to protect the PAH molecules from the AGN radiation field. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society., AA-H and AH-C are partly funded by the Universidad de Cantabria through the Augusto G. Linares programme. AA-H and AH-C acknowledge financial support from the Spanish Plan Nacional grant AYA2012-31447, AA-H and PE from grant AYA2009-05705-E, CRA from grant AYA2010-21887-C04.4 (Estallidos), PE from grant AYA2012-31277, and LC from grant AYA2012-32295. CRA acknowledges financial support from the Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-327934) and SFH from the Marie Curie International Incoming Fellowship within the 7th European Community Framework Programme (PIIFGA-2013-623804).

et al., We analyse the stellar populations in the host galaxies of 53 X-ray selected optically dull active galactic nuclei (AGN) at 0.34 < z < 1.07 with ultradeep (mAB = 26.5, 3σ) optical mediumband (R ~ 50) photometry from the Survey for High-z Absorption Red and Dead Sources (SHARDS). The spectral resolution of SHARDS allows us to consistently measure the strength of the 4000Å break, Dn(4000), a reliable age indicator for stellar populations.We confirm that most X-ray selected moderate-luminosity AGN (LX < 1044 erg s-1) are hosted by massive galaxies (typically M*>1010.5 M⊙) and that the observed fraction of galaxies hosting an AGN increases with the stellar mass. A careful selection of random control samples of inactive galaxies allows us to remove the stellar mass and redshift dependences of the AGN fraction to explore trends with several stellar age indicators. We find no significant differences in the distribution of the rest-frame U - V colour for AGN hosts and inactive galaxies, in agreement with previous results. However, we find significantly shallower 4000Å breaks in AGN hosts, indicative of younger stellar populations.With the help of a model-independent determination of the extinction, we obtain extinction-corrected U - V colours and light-weighted average stellar ages. We find that AGN hosts have younger stellar populations and higher extinction compared to inactive galaxies with the same stellar mass and at the same redshift. We find a highly significant excess of AGN hosts with Dn(4000) ~ 1.4 and light-weighted average stellar ages of 300-500 Myr, as well as a deficit of AGN in intrinsic red galaxies. We interpret failure in recognizing these trends in previous studies as a consequence of the balancing effect in observed colours of the age-extinction degeneracy. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society., AH-C and AA-H acknowledge funding by the Universidad de Cantabria Augusto González Linares programme and the Spanish Plan Nacional de Astronomía y Astrofísica under grant AYA2012-31447. PE and PGP-G acknowledge support from the Spanish Plan Nacional grant AYA2012-31277.

SHARDS is an ongoing ESO/GTC large program that is obtaining ultra-deep photometry of the GOODS-North field in 24 medium-band filters (reaching m=26.5 AB in all bands) in the 500-950 nm range with GTC/OSIRIS. It is designed to study the properties of high-z massive galaxies, but it can also provide very valuable information about the population of AGN at intermediate redshifts (z~0.5-2). Here we present preliminary results on a study of the stellar populations and star formation activity in the host galaxies of X-ray selected optically faint AGN at 0.610^10.5 Mo) and that the fraction of galaxies hosting an AGN increases with the stellar mass. AGN-hosts have restframe U-V and Dn(4000) comparable to those of non-active galaxies of the same mass, that is, they do not appear to have on average younger stellar populations, unlike in the Local Universe. Nevertheless, z~1 AGN hosts show an excess of IR emission at {\lambda}>3{\mu}m compared to non-AGN galaxies which might indicate increased star formation rates. In addition, the frequency of AGN in massive galaxies is about twice higher for the ones with young stellar populations compared to the older ones., Comment: 3 pages, 2 figures, to appear in "Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation", Proceedings of Science, Max-Planck-Institut f\"ur Radioastronomie, Bonn, Germany, November 6-8, 2012

Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of, This work was supported in part by the Spanish Plan Nacional de Astronomía y Astrofísica under grants AYA2009-05705-E and AYA2010-21161-C02-1 and by the Augusto Gonzalez Linares Program from the Universidad de Cantabria. M.P.-S. is funded by an ASI fellowship under contract I/005/11/0. A.M.D. acknowledges support from the Southern California Center for Galaxy Evolution, a multi-campus research program funded by the University of California Office of Research.

(Abridged) We probe the merging channel of massive galaxies over the z=0.3-1.3 redshift window by studying close pairs in a sample of 238 galaxies with stellar mass >1E11Msun, from the deep (m0.3, followed by a decrease in the fractional mass growth rate linearly proportional to log mu, at least down to mu~0.01, suggesting a decreasing role of mergers involving low-mass satellites, especially if dynamical friction timescales are taken into account. A simple model results in an upper limit for the average mass growth rate of massive galaxies of DM/M/Dt~ 0.08+-0.02 per Gyr, over the z0.3. The majority of the stellar mass contributed by mergers does not introduce significantly younger populations, in agreement with the small radial age gradients observed in present-day early-type galaxies., MNRAS in press, 14 pages, 10+1 figures, 3 tables

A. Hernán-Caballero et al., We report on results from the analysis of a stellar mass-selected (log (M*/M⊙) > 9.0) sample of 1644 galaxies at 0.65 11, in agreement with downsizing scenarios., AH-C and AA-H acknowledge funding by the Universidad de Cantabria Augusto González Linares program. We acknowledge support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2009-07723-E and AYA2009-10368. SHARDS has been funded by the Spanish MICINN/MINECO under the Consolider-Ingenio 2010 Program grant CSD2006-00070: First Science with the GTC.

Obtaining accurate redshifts from mid-infrared (MIR) low-resolution (R ~ 100) spectroscopy is challenging because the wavelength resolution is too low to detect narrow lines in most cases. Yet, the number of degrees of freedom and diversity of spectral features are too high for regular spectral energy distribution (SED) fitting techniques to be convenient. Here we present a new SED-fitting-based routine for redshift determination that is optimized for MIR low-resolution spectroscopy. Its flexible template scaling increases the sensitivity to slope changes and small-scale features in the spectrum, while a new selection algorithm called maximum combined pseudo-likelihood (MCPL) provides increased accuracy and a lower number of outliers compared to the standard maximum-likelihood (ML) approach. Unlike ML approach, the MCPL approach searches for local (instead of absolute) maxima of a 'pseudo-likelihood' (PL) function, and combines results obtained for all the templates in the library to weed out spurious redshift solutions. The capabilities of the MCPL approach are demonstrated by comparing its redshift estimates to those of the regular ML approach and to the optical spectroscopic redshifts of a sample of 491 Spitzer/Infrared Spectrograph spectra from extragalactic sources at 0 < z < 3.7. The MCPL approach achieves a redshift accuracy Δ(z)/(1 + z) < 0.005 for 78 per cent of the galaxies in the sample compared to 68 per cent for the ML approach. The rate of outliers [Δ(z)/(1 + z) > 0.02] is 14 per cent for the MCPL approach and 22 per cent for the ML approach. χ 2 values for ML solutions are found to correlate with the signal-to-noise ratio of the spectra, but not with redshift accuracy. By contrast, the peak value of the normalized combined PL (γ) is found to provide a good indication on the reliability of the MCPL solution for individual sources. The accuracy and reliability of the redshifts depend strongly on the MIR SED. Sources with significant polycyclic aromatic hydrocarbon emission obtain much better results compared to sources dominated by active galactic nucleus continua. Nevertheless, for a given γ the frequency of accurate solutions and outliers is largely independent of their SED type. This reliability indicator for MCPL solutions allows to select subsamples with highly reliable redshifts. In particular, a γ > 0.15 threshold retains 79 per cent of the sources with Δ(z)/(1 + z) < 0.005 while reducing the outlier rate to 3.8 per cent. © 2012 The Author Monthly Notices of the Royal Astronomical Society. © 2012 RAS., AH-C is funded by the Universidad de Cantabria Augusto González Linares programme.