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Aims. Our aim is to determine the distribution of stellar population parameters (extinction, age, metallicity, and star formation rates) of quiescent galaxies within the rest-frame stellar mass–colour diagrams and UVJ colour–colour diagrams corrected for extinction up to z ∼ 1. These novel diagrams reduce the contamination in samples of quiescent galaxies owing to dust-reddened galaxies, and they provide useful constraints on stellar population parameters only using rest-frame colours and/or stellar mass. Methods. We set constraints on the stellar population parameters of quiescent galaxies combining the ALHAMBRA multi-filter photo-spectra with our fitting code for spectral energy distribution, MUlti-Filter FITting (MUFFIT), making use of composite stellar population models based on two independent sets of simple stellar population (SSP) models. The extinction obtained by MUFFIT allowed us to remove dusty star-forming (DSF) galaxies from the sample of red UVJ galaxies. The distributions of stellar population parameters across these rest-frame diagrams are revealed after the dust correction and are fitted by LOESS, a bi-dimensional and locally weighted regression method, to reduce uncertainty effects. Results. Quiescent galaxy samples defined via classical UVJ diagrams are typically contaminated by a ∼20% fraction of DSF galaxies. A significant part of the galaxies in the green valley are actually obscured star-forming galaxies (∼30–65%). Consequently, the transition of galaxies from the blue cloud to the red sequence, and hence the related mechanisms for quenching, seems to be much more efficient and faster than previously reported. The rest-frame stellar mass–colour and UVJ colour–colour diagrams are useful for constraining the age, metallicity, extinction, and star formation rate of quiescent galaxies by only their redshift, rest-frame colours, and/or stellar mass. Dust correction plays an important role in understanding how quiescent galaxies are distributed in these diagrams and is key to performing a pure selection of quiescent galaxies via intrinsic colours. [ABSTRACT FROM AUTHOR]

Aims. We aim at constraining the stellar population properties of quiescent galaxies. These properties reveal how these galaxies evolved and assembled since z ∼ 1 up to the present time. Methods. Combining the ALHAMBRA multi-filter photo-spectra with the fitting code for spectral energy distribution MUFFIT (MUlti-Filter FITting), we built a complete catalogue of quiescent galaxies via the dust-corrected stellar mass vs. colour diagram. This catalogue includes stellar population properties, such as age, metallicity, extinction, stellar mass, and photometric redshift, retrieved from the analysis of composited populations based on two independent sets of simple stellar population (SSP) models. We developed and applied a novel methodology to provide, for the first time, the analytic probability distribution functions (PDFs) of mass-weighted age, metallicity, and extinction of quiescent galaxies as a function of redshift and stellar mass. We adopted different star formation histories to discard potential systematics in the analysis. Results. The number density of quiescent galaxies is found to increase since z ∼ 1, with a more substantial variation at lower stellar mass. Quiescent galaxies feature extinction AV <  0.6, with median values in the range AV = 0.15–0.3. At increasing stellar mass, quiescent galaxies are older and more metal rich since z ∼ 1. A detailed analysis of the PDFs reveals that the evolution of quiescent galaxies is not compatible with passive evolution and a slight decrease of 0.1–0.2 dex is hinted at median metallicity. The intrinsic dispersion of the age and metallicity PDFs show a dependence on stellar mass and/or redshift. These results are consistent with both sets of SSP models and assumptions of alternative star formation histories explored. Consequently, the quiescent population must undergo an evolutive pathway including mergers and/or remnants of star formation to reconcile the observed trends, where the "progenitor" bias should also be taken into account. [ABSTRACT FROM AUTHOR]

We investigated the mass-to-light vs. color relations (MLCRs) derived from the spatially resolved star formation history of a sample of 452 galaxies observed with integral field spectroscopy in the CALIFA survey. We derived the stellar mass (M⋆) and the stellar mass surface density (Σ⋆) from the combination of full spectral fitting (using different sets of stellar population models) with observed and synthetic colors in optical broad bands. This method allows obtaining the radial structure of the mass-to-light ratio (M/L) at several wavelengths and studying the spatially resolved MLCRs. Our sample covers a wide range of Hubble types from Sc to E, with stellar masses ranging from M⋆ ∼ 108.4 to 1012 M⊙. The scatter in the MLCRs was studied as a function of morphology, stellar extinction, and emission line contribution to the colors. The effects of the initial mass function (IMF) and stellar population models in the MLCRs were also explored. Our main results are that (a) the M/L ratio has a negative radial gradient that is steeper within the central 1 half-light-radius (HLR). It is steeper in Sb-Sbc than in early-type galaxies. (b) The MLCRs between M/L and optical colors were derived with a scatter of ∼0.1 dex. The smallest dispersion was found for the combinations (i, g − r) and (R, B − R). Extinction and emission line contributions do not affect the scatter of these relations. Morphology does not produce a significant effect, except if the general relation is used for galaxies redder than (u − i) > 4 or bluer than (u − i)< 0. (c) The IMF has a large effect on MLCRs, as expected. The change from a Chabrier to a Salpeter IMF produces a median shift of ∼0.29 dex when mass loss from stellar evolution is also taken into account. (d) These MLCRs are in agreement with previous results, in particular for relations with g and r bands and the B and V Johnson systems. [ABSTRACT FROM AUTHOR]

We present a technique that permits the analysis of stellar population gradients in a relatively low-cost way compared to integral field unit (IFU) surveys. We developed a technique to analyze unresolved stellar populations of spatially resolved galaxies based on photometric multi-filter surveys. This technique allows the analysis of vastly larger samples and out to larger galactic radii. We derived spatially resolved stellar population properties and radial gradients by applying a centroidal Voronoi tessellation and performing a multicolor photometry spectral energy distribution fitting. This technique has been successfully applied to a sample of 29 massive (M⋆ >1010.5M⊙) early-type galaxies at z < 0.3 from the ALHAMBRA survey. We produced detailed 2D maps of stellar population properties (age, metallicity, and extinction), which allow us to identify galactic features. Radial structures were studied, and luminosity-weighted and mass-weighted gradients were derived out to 2–3.5 Reff. We find that the spatially resolved stellar population mass, age, and metallicity are well represented by their integrated values. We find the gradients of early-type galaxies to be on average flat in age (∇log AgeL = 0.02 ± 0.06 dex/Reff) and negative in metallicity (∇[Fe/H]L = −0.09 ± 0.06 dex/Reff). Overall,the extinction gradients are flat (∇Av = −0.03 ± 0.09 mag/Reff ) with a wide spread. These results are in agreement with previous studies that used standard long-slit spectroscopy, and with the most recent IFU studies. According to recent simulations, these results are consistent with a scenario where early-type galaxies were formed through major mergers and where their final gradients are driven by the older ages and higher metallicity of the accreted systems. We demonstrate the scientific potential of multi-filter photometry to explore the spatially resolved stellar populations of local galaxies and confirm previous spectroscopic trends from a complementary technique. [ABSTRACT FROM AUTHOR]

The Calar Alto Legacy Integral Field Area (CALIFA) survey, a pioneer in integral field spectroscopy legacy projects, has fostered many studies exploring the information encoded on the spatially resolved data on gaseous and stellar features in the optical range of galaxies. We describe a value-added catalogue of stellar population properties for CALIFA galaxies analysed with the spectral synthesis code STARLIGHT and processed with the PYCASSO platform. Our public database (http://pycasso.ufsc.br/, mirror at http://pycasso.iaa.es/) comprises 445 galaxies from the CALIFA Data Release 3 with COMBO data. The catalogue provides maps for the stellar mass surface density, mean stellar ages and metallicities, stellar dust attenuation, star formation rates, and kinematics. Example applications both for individual galaxies and for statistical studies are presented to illustrate the power of this data set. We revisit and update a few of our own results on mass density radial profiles and on the local mass–metallicity relation. We also show how to employ the catalogue for new investigations, and show a pseudo Schmidt–Kennicutt relation entirely made with information extracted from the stellar continuum. Combinations to other databases are also illustrated. Among other results, we find a very good agreement between star formation rate surface densities derived from the stellar continuum and the Hα emission. This public catalogue joins the scientific community's effort towards transparency and reproducibility, and will be useful for researchers focusing on (or complementing their studies with) stellar properties of CALIFA galaxies. [ABSTRACT FROM AUTHOR]

We present an extended version of the spectral synthesis code starlight designed to incorporate both λ-by-λ spectra and photometric fluxes in the estimation of stellar population properties of galaxies. The code is tested with simulations and data for 260 galaxies culled from the CALIFA survey, spatially matching the 3700-7000 Å optical datacubes to GALEX near and far UV images. The sample spans E-Sd galaxies with masses from 109 to 1012M⊙ and stellar populations all the way from star-forming to old, passive systems. Comparing results derived from purely optical fits with those which also consider the NUV and FUV data we find that: (1) The new code is capable of matching the input UV data within the errors while keeping the quality of the optical fit essentially unchanged. (2) Despite being unreliable predictors of the UV fluxes, purely optical fits yield stellar population properties which agree well with those obtained in optical+UV fits for nearly 90% of our sample. (3) The addition of UV constraints has little impact on properties such as stellar mass and dust optical depth. Mean stellar ages and metallicities also remain nearly the same for most galaxies, the exception being low-mass, late-type galaxies, which become older and less enriched due to rearrangements of their youngest populations. (4) The revised ages are better correlated with observables such as the 4000 Å break index, and the NUV - r and u - r colours, an empirical indication that the addition of UV constraints helps mitigating the effects of age-metallicity-extinction degeneracies. [ABSTRACT FROM AUTHOR]

We present deep long-slit optical spectra for a sample of 36 ultraluminous infrared galaxies (ULIRGs), taken with the William Herschel Telescope on La Palma with the aim of investigating the star formation histories and testing evolutionary scenarios for such objects. Here we present the sample, the analysis techniques and a general overview of the properties of the stellar populations; a more detailed discussion will be presented in a forthcoming paper. Spectral synthesis modelling has been used in order to estimate the ages of the stellar populations found in the diffuse light sampled by the spectra in both the nuclear and extended regions of the target galaxies. We find that adequate fits can be obtained using combinations of young stellar populations (YSPs; Gyr), with ages divided into two groups: very young stellar populations (VYSPs; Myr) and intermediate-young stellar populations (IYSPs; Gyr). Our results show that YSPs are present at all locations of the galaxies covered by our slit positions, with the exception of the northern nuclear region of the ULIRG IRAS 23327+2913. Furthermore, VYSPs are present in at least 85 per cent of the 133 extraction apertures used for this study, being more significant in the nuclear regions of the galaxies. Old stellar populations (OSPs; Gyr) do not make a major contribution to the optical light in the majority of the apertures extracted. In fact they are essential for fitting the spectra in only 5 per cent (seven) of the extracted apertures. The estimated total masses for the YSPs (VYSPs + IYSPs) are in the range . We have also estimated the bolometric luminosities associated with the stellar populations detected at optical wavelengths, finding that they fall in the range . In addition, we find that reddening is significant at all locations in the galaxies. This result emphasizes the importance of accounting for reddening effects when modelling the stellar populations of star-forming galaxies. [ABSTRACT FROM AUTHOR]

We present long-slit, optical spectra of the merging system Arp220, obtained using the William Herschel Telescope (WHT) on La Palma. These data were taken as a part of a large study of ultraluminous infrared galaxies (ULIRGs) with the aim of investigating the evolution and star formation histories of such objects. Spectral synthesis modelling has been used to estimate the ages of the stellar populations found in the diffuse light sampled by the spectra. As the closest ULIRG, it proved possible to perform a detailed study of the stellar populations over the entire body of the object. The data show a remarkable uniformity in the stellar populations across the full 65 arcsec covered by our slit positions, sampling the measurable extent of the galaxy. The results are consistent with a dominant intermediate-age stellar population (ISP) with age Gyr that is present at all locations, with varying contributions from a young (≤0.1 Gyr) stellar population (YSP) component. However, it is notable that while the flux contribution of the YSP component in the extended regions is relatively small (≤40 per cent), adequate fits in the nuclear region are only found for combinations with a significant contribution of a YSP component (22–63 per cent). Moreover, while a low intrinsic reddening ( E( B− V) ≲ 0.3) is found for the ISPs in the extended regions, intrinsic reddening values as high as E( B− V) ∼ 1.0 are required in the galactic centre. This clearly reflects the presence of a reddening gradient, with higher concentrations of gas and dust towards the nuclear regions, coinciding with dust lanes in the Hubble Space Telescope images. Overall, our results are consistent with models that predict an epoch of enhanced star formation coinciding with the first pass of the merging nuclei (represented by the ISP), with a further episode of star formation occurring as the nuclei finally merge together (represented by the YSP and ULIRG). [ABSTRACT FROM AUTHOR]