The final product of galaxy evolution through cosmic time is the population of galaxies in the local universe. These galaxies are also those that can be studied in most detail, thus providing a stringent benchmark for our understanding of galaxy evolution. Through the huge success of spectroscopic single-fiber, statistical surveys of the Local Universe in the last decade, it has become clear, however, that an authoritative observational description of galaxies will involve measuring their spatially resolved properties over their full optical extent for a statistically significant sample. We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey, which has been designed to provide a first step in this direction. We summarize the survey goals and design, including sample selection and observational strategy. We also showcase the data taken during the first observing runs (June/July 2010) and outline the reduction pipeline, quality control schemes and general characteristics of the reduced data. This survey is obtaining spatially resolved spectroscopic information of a diameter selected sample of ∼600 galaxies in the Local Universe (0.005 < z < 0.03). CALIFA has been designed to allow the building of two-dimensional maps of the following quantities: (a) stellar populations: ages and metallicities; (b) ionized gas: distribution, excitation mechanism and chemical abundances; and (c) kinematic properties: both from stellar and ionized gas components. CALIFA uses the PPAK integral field unit (IFU), with a hexagonal field-of-view of ∼1.3 , with a 100% covering factor by adopting a three-pointing dithering scheme. The optical wavelength range is covered from 3700 to 7000 Å, using two overlapping setups (V500 and V1200), with different resolutions: R ∼ 850 and R ∼ 1650, respectively. CALIFA is a legacy survey, intended for the community. The reduced data will be released, once the quality has been guaranteed. The analyzed data fulfill the expectations of the original observing proposal, on the basis of a set of quality checks and exploratory analysis: (i) the final datacubes reach a 3σ limiting surface brightness depth of ∼23.0 mag/arcsec 2 for the V500 grating data (∼22.8 mag/arcsec 2 for V1200); (ii) about ∼70% of the covered field-of-view is above this 3σ limit; (iii) the data have a blue-to-red relative flux calibration within a few percent in most of the wavelength range; (iv) the absolute flux calibration is accurate within ∼8% with respect to SDSS; (v) the measured spectral resolution is ∼85 km s −1 for V1200 (∼150 km s −1 for V500); (vi) the estimated accuracy of the wavelength calibration is ∼5 km s −1 for the V1200 data (∼10 km s −1 for the V500 data); (vii) the aperture matched CALIFA and SDSS spectra are qualitatively and quantitatively similar. Finally, we show that we are able to carry out all measurements indicated above, recovering the properties of the stellar populations, the ionized gas and the kinematics of both components. The associated maps illustrate the spatial variation of...

The growth of galaxies is one of the key problems in understanding the structure and evolution of the universe and its constituents. Galaxies can grow their stellar mass by accretion of halo or intergalactic gas clouds, or by merging with smaller or similar mass galaxies. The gas available translates into a rate of star formation, which controls the generation of metals in the universe. The spatially resolved history of their stellar mass assembly has not been obtained so far for any given galaxy beyond the Local Group. Here we demonstrate how massive galaxies grow their stellar mass inside-out. We report the results from the analysis of the first 105 galaxies of the largest to date three-dimensional spectroscopic survey of galaxies in the local universe (CALIFA). We apply the fossil record method of stellar population spectral synthesis to recover the spatially and time resolved star formation history of each galaxy. We show, for the first time, that the signal of downsizing is spatially preserved, with both inner and outer regions growing faster for more massive galaxies. Further, we show that the relative growth rate of the spheroidal component, nucleus and inner galaxy, that happened 5-7 Gyr ago, shows a maximum at a critical stellar mass ∼ 7×10 10 M ⊙ . We also find that galaxies less massive than ∼ 10 10 M ⊙ show a transition to outside-in growth, thus connecting with results from resolved studies of the growth of low mass galaxies.

We present the largest and most homogeneous catalog of H ii regions and associations compiled so far. The catalog comprises more than 7000 ionized regions, extracted from 306 galaxies observed by the CALIFA survey. We describe the procedures used to detect, select, and analyze the spectroscopic properties of these ionized regions. In the current study we focus on characterizing of the radial gradient of the oxygen abundance in the ionized gas, based on the study of the deprojected distribution of H ii regions. We found that all galaxies without clear evidence of an interaction present a common gradient in the oxygen abundance, with a characteristic slope of α O/H = −0.1 dex/r e between 0.3 and 2 disk effective radii (r e ), and a scatter compatible with random fluctuations around this value, when the gradient is normalized to the disk effective radius. The slope is independent of morphology, the incidence of bars, absolute magnitude, or mass. Only those galaxies with evidence of interactions and/or clear merging systems present a significantly shallower gradient, consistent with previous results. The majority of the 94 galaxies with H ii regions detected beyond two disk effective radii present a flattening in the oxygen abundance. The flattening is statistically significant. We cannot provide a conclusive answer regarding the origin of this flattening. However, our results indicate that its origin is most probably related to the secular evolution of galaxies. Finally, we find a drop/truncation of the oxygen abundance in the inner regions for 26 of the galaxies. All of them are non-interacting, mostly unbarred Sb/Sbc galaxies. This feature is associated with a central star-forming ring, which suggests that both features are produced by radial gas flows induced by resonance processes. Our result suggests that galaxy disks grow inside-out, with metal enrichment driven by the local star formation history and with a small variation galaxy-by-galaxy. At a certain galactocentric distance, the oxygen abundance seems to be correlated well with the stellar mass density and total stellar mass of the galaxies, independently of other properties of the galaxies. Other processes, such as radial mixing and inflows/outflows seem to have a limited effect on shaping of the radial distribution of oxygen abundances, although they are not ruled out.

Context. The bar pattern speed (Ω b ) is defined as the rotational frequency of the bar, and it determines the bar dynamics. Several methods have been proposed for measuring Ω b . The non-parametric method proposed by Tremaine & Weinberg (1984, ApJ, 282, L5; TW) and based on stellar kinematics is the most accurate. This method has been applied so far to 17 galaxies, most of them SB0 and SBa types. Aims. We have applied the TW method to a new sample of 15 strong and bright barred galaxies, spanning a wide range of morphological types from SB0 to SBbc. Combining our analysis with previous studies, we investigate 32 barred galaxies with their pattern speed measured by the TW method. The resulting total sample of barred galaxies allows us to study the dependence of Ω b on galaxy properties, such as the Hubble type. Methods. We measured Ω b using the TW method on the stellar velocity maps provided by the integral-field spectroscopy data from the CALIFA survey. Integral-field data solve the problems that long-slit data present when applying the TW method, resulting in the determination of more accurate Ω b . In addition, we have also derived the ratio R of the corotation radius to the bar length of the galaxies. According to this parameter, bars can be classified as fast (R < 1.4) and slow (R > 1.4). Results. For all the galaxies, R is compatible within the errors with fast bars. We cannot rule out (at 95% level) the fast bar solution for any galaxy. We have not observed any significant trend between R and the galaxy morphological type. Conclusions. Our results indicate that independent of the Hubble type, bars have been formed and then evolve as fast rotators. This observational result will constrain the scenarios of formation and evolution of bars proposed by numerical simulations.

This paper presents the mass assembly time scales of nearby galaxies observed by CALIFA at the 3.5m telescope in Calar Alto. We apply the fossil record method of the stellar populations to the complete sample of the 3rd CALIFA data release, with a total of 661 galaxies, covering stellar masses from 10 8.4 to 10 12 M and a wide range of Hubble types. We apply spectral synthesis techniques to the datacubes and process the results to produce the mass growth time scales and mass weighted ages, from which we obtain temporal and spatially resolved information in seven bins of galaxy morphology (E, S0, Sa, Sb, Sc, and Sd) and six bins of stellar mass and stellar mass surface density. We use three different tracers of the spatially resolved star formation history (mass assembly curves, ratio of half mass to half light radii, and mass-weighted age gradients) to test if galaxies grow inside-out, and its dependence with galaxy stellar mass, stellar mass surface density, and morphology. Our main results are as follows: (a) The innermost regions of galaxies assemble their mass at an earlier time than regions located in the outer parts; this happens at any given stellar mass (M ), stellar mass surface density (Σ ), or Hubble type, including the lowest mass systems in our sample. (b) Galaxies present a significant diversity in their characteristic formation epochs for lower-mass systems. This diversity shows a strong dependence of the mass assembly time scales on Σ and Hubble type in the lower-mass range (10 8.4 to 10 10.4 ), but a very mild dependence in higher-mass bins. (c) The lowest half mass radius (HMR) to half light radius (HLR) ratio is found for galaxies between 10 10.4 and 10 11.1 M , where galaxies are 25% smaller in mass than in light. Low-mass galaxies show the largest ratio with HMR/HLR∼ 0.89. Sb and Sbc galaxies present the lowest HMR/HLR ratio (0.74). The ratio HMR/HLR is always, on average, below 1, indicating that galaxies grow faster in mass than in light. (d) All galaxies show negative log age M gradients in the inner 1 HLR. The profile flattens (slope less negative) with increasing values of Σ . There is no significant dependence on M within a particular Σ bin, except for the lowest bin, where the gradients becomes steeper. (e) Downsizing is spatially preserved as a function of M and Σ , but it is broken for E and SO where the outer parts are assembled in later epochs than Sa galaxies. These results suggest that independently of their stellar mass, stellar mass surface density, and morphology, galaxies form inside-out on average.