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...

We present the first public data release (DR1) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. It consists of science-grade optical datacubes for the first 100 of eventually 600 nearby (0.005 < z < 0.03) galaxies, obtained with the integral-field spectrograph PMAS/PPak mounted on the 3.5 m telescope at the Calar Alto observatory. The galaxies in DR1 already cover a wide range of properties in color-magnitude space, morphological type, stellar mass, and gas ionization conditions. This offers the potential to tackle a variety of open questions in galaxy evolution using spatially resolved spectroscopy. Two different spectral setups are available for each galaxy, (i) a low-resolution V500 setup covering the nominal wavelength range 3745-7500 Å with a spectral resolution of 6.0 Å (FWHM), and (ii) a medium-resolution V1200 setup covering the nominal wavelength range 3650-4840 Å with a spectral resolution of 2.3 Å (FWHM). We present the characteristics and data structure of the CALIFA datasets that should be taken into account for scientific exploitation of the data, in particular the effects of vignetting, bad pixels and spatially correlated noise. The data quality test for all 100 galaxies showed that we reach a median limiting continuum sensitivity of 1.0 × 10 −18 erg s −1 cm −2 Å −1 arcsec −2 at 5635 Å and 2.2 × 10 −18 erg s −1 cm −2 Å −1 arcsec −2 at 4500 Å for the V500 and V1200 setup respectively, which corresponds to limiting r and g band surface brightnesses of 23.6 mag arcsec −2 and 23.4 mag arcsec −2 , or an unresolved emission-line flux detection limit of roughly 1 × 10 −17 erg s −1 cm −2 arcsec −2 and 0.6 × 10 −17 erg s −1 cm −2 arcsec −2 , respectively. The median spatial resolution is 3. 7, and the absolute spectrophotometric calibration is better than 15% (1σ). We also describe the available interfaces and tools that allow easy access to this first public CALIFA data at http://califa.caha.es/DR1.

We use the Sloan Digital Sky Survey to investigate the properties of massive elliptical galaxies in the local Universe (z ≤ 0.08) that have unusually blue optical colors. Through careful inspection, we distinguish elliptical from non-elliptical morphologies among a large sample of similarly blue galaxies with high central light concentrations (c r ≥ 2.6). These blue ellipticals comprise 3.7 per cent of all c r ≥ 2.6 galaxies with stellar masses between 10 10 and 10 11 h −2 M . Using published fiber spectra diagnostics, we identify a unique subset of 172 non-star-forming ellipticals with distinctly blue urz colors and young (< 3 Gyr) lightweighted stellar ages. These recently quenched ellipticals (RQEs) have a number density of 2.7 − 4.7 × 10 −5 h 3 Mpc −3 and sufficient numbers above 2.5 × 10 10 h −2 M to account for more than half of the expected quiescent growth at late cosmic time assuming this phase lasts 0.5 Gyr. RQEs have properties that are consistent with a recent merger origin (i.e., they are strong 'first-generation' elliptical candidates), yet few involved a starburst strong enough to produce an E+A signature. The preferred environment of RQEs (90 per cent reside at the centers of < 3 × 10 12 h −1 M groups) agrees well with the 'small group scale' predicted for maximally efficient spiral merging on to their halo center and rules out satellite-specific quenching processes. The high incidence of Seyfert and LINER activity in RQEs and their plausible descendants may heat the atmospheres of small host halos sufficiently to maintain quenching.

We study the role of cold gas in quenching star formation in the green valley by analyzing ALMA 12 CO (1-0) observations of three galaxies with resolved optical spectroscopy from the MaNGA survey. We present resolution-matched maps of the star formation rate and molecular gas mass. These data are used to calculate the star formation efficiency (SFE) and gas fraction ( f gas ) for these galaxies separately in the central "bulge" regions and outer disks. We find that, for the two galaxies whose global specific star formation rate (sSFR) deviates most from the star formation main sequence, the gas fraction in the bulges is significantly lower than that in their disks, supporting an "inside-out" model of galaxy quenching. For the two galaxies where SFE can be reliably determined in the central regions, the bulges and disks share similar SFEs. This suggests that a decline in f gas is the main driver of lowered sSFR in bulges compared to disks in green valley galaxies. Within the disks, there exist common correlations between the sSFR and SFE and between sSFR and f gas on kiloparsec scales-the local SFE or f gas in the disks declines with local sSFR. Our results support a picture in which the sSFR in bulges is primarily controlled by f gas , whereas both SFE and f gas play a role in lowering the sSFR in disks. A larger sample is required to confirm if the trend established in this work is representative of the green valley as a whole.

We analyze a high-resolution N-body simulation of a live stellar disk perturbed by the recent passage of a massive dwarf galaxy that induces a wobble, in-plane rings and phase spirals in the disk. The implications of the phase-space structures and the estimate of the matter density through traditional Jeans modeling are investigated. The dwarf satellite excites rapid time-variations in the potential, leading to a significant bias of the local matter surface density determined through such a method. In particular, while the Jeans modelling gives reasonable estimates for the surface density in the most overdense regions of the disk, we show that it fails elsewhere. Our results show that the spiralshape feature in the z − v z plane is visible preferentially in the under-dense regions and vanishes more quickly in the inner parts of the stellar disk or in high-density regions of the disk. While this prediction can be verified with Gaia DR3 our finding is highly relevant for future attempts in determining the dynamical surface density of the outer Milky Way disk as a function of radius. The outer disk of the Milky Way is indeed heavily perturbed, and Gaia DR2 data have clearly shown that such phase-space perturbations are even present locally. While our results show that traditional Jeans modelling should give reliable results in overdense regions of the disk, the important biases in underdense regions call for the development of non-equilibrium methods to estimate the dynamical matter density locally and in the outer disk.