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We use spatially resolved spectroscopy from the Calar Alto Legacy Integral Field Area (CALIFA) survey to study the nature of the line emitting gas in galaxies of different Hubble types, focusing on the separation of star-forming (SF) regions from those better characterized as diffuse ionized gas (DIG). The diagnosis is carried out in terms of the equivalent width of Hα (WHα). Three nebular regimes are identified. Regions where WHα < 3 Å define what we call the hDIG, the component of the DIG where photoionization is dominated by hot, low-mass, evolved stars. Regions where WHα > 14 Å trace SF complexes. WHα values in the intermediate 3-14 Å range reflect a mixed regime (mDIG) where more than one process contributes. This three-tier scheme is inspired both by theoretical and empirical considerations. Its application to CALIFA galaxies of different types and inclinations leads to the following results: (i) the hDIG component is prevalent throughout ellipticals and S0's as well as in bulges, and explains the strongly bimodal distribution of WHα both among and within galaxies. (ii) Early-type spirals have some hDIG in their discs, but this component becomes progressively less relevant for later Hubble types. (iii) hDIG emission is also present above and below galactic discs, as seen in several edge-on spirals in our sample. (iv) The SF/mDIG proportion grows steadily from early- to late-type spirals, and from inner to outer radii. (v) Besides circumventing basic inconsistencies in conventional DIG/SF separation criteria based on the Hα surface brightness, our WHα-based method produces results in agreement with a classical excitation diagram analysis. [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 a spectroscopic atlas of active galactic nuclei covering the region around thecalcium triplet (CaT). The sample comprises 78 objects, divided into 43 Seyfert 2s, 26 Seyfert 1s, three starburst and six normal galaxies. The spectra pertain to the inner∼300 pc in radius, and thus sample the central kinematics and stellar populations of active galaxies. The data are used to measure stellar velocity dispersionswith both cross-correlation and direct fitting methods. These measurements are found to be in good agreement with each other and with those in previous studies for objects in common. The CaT equivalent width is also measured. We find average values and sample dispersions ofWCaT ofandfor Seyfert 1s, Seyfert 2s and normal galaxies, respectively. We further present an atlas of[S iii]λ9069 emission-line profiles for a subset of 40 galaxies. These data are analysed in a companion paper which addresses the connection between stellar and narrow-line region kinematics, the behaviour of the CaT equivalent width as a function ofσ★, activity type and stellar population properties. [ABSTRACT FROM AUTHOR]

ABSTRACT We use high signal-to-noise ratio long-slit spectra in the λλ3600–4700 range of the 20 brightest northern Seyfert 2 galaxies to study the variation of the stellar population properties as a function of distance from the nucleus. In order to characterize the stellar population and other continuum sources (e.g. featureless continuum, FC) we have measured the equivalent width, W, of six absorption features, four continuum colours and their radial variations, and performed spectral population synthesis as a function of distance from the nucleus. About half of the sample has Ca iiK and G band W values smaller at the nucleus than at 1 kpc from it, owing to a younger population and/or FC. The stellar population synthesis shows that, while at the nucleus, 75 per cent of the galaxies present contribution >20 per cent of ages ≤100 Myr and/or of an FC, this proportion decreases to 45 per cent at 3 kpc. In particular, 55 per cent of the galaxies have a contribution >10 per cent of the 3-Myr/FC component (a degenerate component in which one cannot separate what is caused by an FC or by a 3-Myr stellar population) at the nucleus, but only 25 per cent of them have this contribution at 3 kpc. As a reference, the stellar population of 10 non-Seyfert galaxies, spanning the Hubble types of the Seyfert (from S0 to Sc) was also studied. A comparison between the stellar population of the Seyferts and that of the non-Seyferts shows systematic differences: the contribution of ages younger than 1 Gyr is in most cases larger in the Seyfert galaxies than in non-Seyferts, not only at the nucleus but up to 1 kpc from it. [ABSTRACT FROM AUTHOR]