Calar Alto Legacy Integral Field Area Research Articles

The Calar Alto Legacy Integral Field Area survey: extended and remastered data release

ABSTRACT This paper describes the extended data release (eDR) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. It comprises science-grade quality data for 895 galaxies obtained with the Potsdam Multi Aperture Spectograph/PPak instrument at the 3.5-m telescope at the Calar Alto Observatory along the last 12 yr, using the V500 setup [3700–7500 Å, 6 Å/full-width at half-maximum (FWHM)] and the CALIFA observing strategy. It includes galaxies of any morphological type, star formation stage, a wide range of stellar masses (∼107–1012 M⊙), at an average redshift of ∼0.015 (90 per cent within 0.005 < z < 0.05). Primarily selected based on the projected size and apparent magnitude, we demonstrate that it can be volume corrected resulting in a statistically limited but representative sample of the population of galaxies in the nearby Universe. All the data were homogeneous re-reduced, introducing a set of modifications to the previous reduction. The most relevant is the development and implementation of a new cube-reconstruction algorithm that provides with an (almost) seeing-limited spatial resolution (FWHMPSF ∼ 1.0 arcsec). To illustrate the usability and quality of the data, we extracted two aperture spectra for each galaxy (central 1.5 arcsec and fully integrated), and analyse them using pyFIT3D. We obtain a set of observational and physical properties of both the stellar populations and the ionized gas, that have been compared for the two apertures, exploring their distributions as a function of the stellar masses and morphologies of the galaxies, comparing with recent results in the literature.

Non-parametric galaxy morphology from stellar and nebular emission with the CALIFA sample

Aims. We present a non-parametric morphology analysis of the stellar continuum and nebular emission lines for a sample of local galaxies. We explore the dependence of the various morphological parameters on wavelength and morphological type. Our goal is to quantify the difference in morphology between the stellar and nebular components. Methods. We derived the non-parametric morphological indicators of 364 galaxies from the Calar Alto Legacy Integral Field Area (CALIFA) Survey. To calculate those indicators, we applied the StatMorph package on the high-quality integral field spectroscopic data cubes, as well as to the most prominent nebular emission-line maps, namely [O III]λ5007, Hα, and [N II]λ6583. Results. We show that the physical size of galaxies, M20 index, and concentration have a strong gradient from blue to red optical wavelengths. We find that the light distribution of the nebular emission is less concentrated than the stellar continuum. A comparison between the non-parametric indicators and the galaxy physical properties revealed a very strong correlation of the concentration with the specific star formation rate and morphological type. Furthermore, we explore how the galaxy inclination affects our results. We find that edge-on galaxies show a more rapid change in physical size and concentration with increasing wavelength due to the increase in the optical free path. Conclusions. We conclude that the apparent morphology of galaxies originates from the pure stellar distribution, but the morphology of the interstellar medium presents differences with respect to the morphology of the stellar component. Our analysis also highlights the importance of dust attenuation and galaxy inclination in the measurement of non-parametric morphological indicators, especially in the wavelength range 4000−5000 Å.

Mass–metallicity and star formation rate in galaxies: A complex relation tuned to stellar age

Context. In this work we study the stellar mass–metallicity relation (MZR) of an extended sample of star-forming galaxies in the local Universe and its possible dependence on the star formation rate (SFR). Aims. We selected a sample of approximately 195 000 Sloan Digital Sky Survey (SDSS) star-forming galaxies up to z = 0.22 with the aim of analysing the behaviour of the MZR with respect to SFR whilst taking into account the age of their stellar populations. Methods. For the first time, with this sample, we obtained aperture corrected oxygen and nitrogen-to-oxygen abundances (O/H and N/O, respectively) and SFR using the empirical prescriptions from the Calar Alto Legacy Integral Field Area (CALIFA) survey. To perform this study we also make use of the stellar mass of the galaxies and the parameter Dn(4000) as a proxy for the age of the stellar population. Results. We derive a robust MZR locus, which is found to be fully consistent with the ‘anchoring’ points of a selected set of well-studied nearby galaxies for which the chemical abundance has been derived using the direct method. We observe a complex relation between MZR and SFR across the whole range of galaxy mass and metallicity, where the slope changes seen in the O/H–SFR plane present a pattern that seems to be tuned to the stellar age of the galaxies, and therefore stellar age has to be taken into account in the stellar mass–metallicity–SFR relation. Conclusions. In order to provide an answer to the question of whether or not the MZR depends on the SFR, it is essential to take into account the age of the stellar populations of galaxies. A strong dependence of the MZR on SFR is observed mainly for star-forming galaxies with strong SFR values and low Dn(4000). The youngest galaxies of our SDSS sample show the highest SFR measured for their stellar mass.

Investigating the link between inner gravitational potential and star-formation quenching in CALIFA galaxies

It has been suggested that gravitational potential can have a significant role in suppressing star formation in nearby galaxies. To establish observational constraints on this scenario, we investigated the connection between the dynamics – taking the circular velocity curves (CVCs) as a proxy for the inner gravitational potential – and star formation quenching in 215 non-active galaxies across the Hubble sequence from the Calar Alto Legacy Integral Field Area (CALIFA) survey. Our results show that galaxies with similar CVCs tend to have a certain star-formation quenching pattern. To explore these findings in more details, we constructed kiloparsec(kpc)-resolved relations of the equivalent width of the Hα (WHα) versus the amplitude (Vc) and shape (β = dlnVc/dlnR) of the circular velocity at given radii. We find that the WHα − Vc is a declining relationship, where the retired regions of the galaxies (the ones with WHα values of below 3 Å) tend to have higher Vc. Concurrently, WHα − β is a bimodal relationship, which is characterised by two peaks: concentration of the star forming regions at a positive β (rising CVC) and a second concentration of the retired regions with a negative β (declining CVC). Our results show that both the amplitude of the CVC – driven by the mass of the galaxies – and its shape – which reflects the internal structure of the galaxies – play an important role in the quenching history of a galaxy.

H ii regions in CALIFA survey: II. The relation between their physical properties and galaxy evolution

ABSTRACT We present here the exploration of the physical properties of the sample of H ii regions and aggregations of the last H ii regions catalogue of the Calar Alto Legacy Integral Field Area (CALIFA) survey. This sample comprises the optical spectroscopic properties of more than ∼26 000 ionized regions corresponding to 924 galaxies from the Integral Field Spectroscopy data, including the flux intensity and equivalent widths and the properties of their underlying stellar population. In the current study, we derive a set of physical quantities for all these regions based on those properties, including (i) the fraction of young stars; (ii) the ionization strength (using six different estimations); (iii) the oxygen abundance (using 25 different calibrators); (iv) the nitrogen and nitrogen-to-oxygen abundance; (v) the dust extinction; and (vi) the electron density. Using this data set, we explore how the loci in the classical diagnostic diagrams are connected with those quantities, the radial distributions of these parameters, and the interrelations between themselves and with the properties of the underlying stellar populations. We conclude that many properties of the H ii regions are tightly related to the galactic stellar evolution at the location where those regions are observed. Those properties are modulated only as a second-order effect by the properties of the ionizing stars and the ionized nebulae that do not depend on the astrophysical context in which they are formed. Our results highlight the importance of H ii regions to explore the chemical evolution in galaxies, clarifying which of their properties can be used as proxies of that evolution.

Galaxy evolution on resolved scales: ageing and quenching in CALIFA

ABSTRACT This work investigates the fundamental mechanism(s) that drive galaxy evolution in the local Universe. By comparing two proxies of star formation sensitive to different time-scales, such as EW($\rm H\,\alpha$) and colours like g − r, one may distinguish between smooth secular evolution (ageing) and sudden changes (quenching) in the recent star formation history of galaxies. Building upon the results obtained from a former study based on 80 000 Sloan Digital Sky Survey (SDSS) single-fibre measurements, we now focus on spatially resolved (on kpc scales) galaxies, comparing with a sample of 637 nearby objects observed by the Calar Alto Legacy Integral-Field Area survey. In general, galaxies cannot be characterized in terms of a single ‘evolutionary stage’. Individual regions within galaxies arrange along a relatively narrow ageing sequence, with some intrinsic scatter possibly due to their different evolutionary paths. These sequences, though, differ from one galaxy to another, although they are broadly consistent with the overall distribution found for the (central) SDSS spectra. We find evidence of recent quenching episodes (relatively blue colours and strong $\rm H\,\alpha$ absorption) in a small fraction of galaxies (most notably, low-mass ellipticals), on global scales and individual regions (particularly at high metallicity). However, we argue that most of the systems, over their entire extent, are compatible with a secular inside-out scenario, where the evolutionary stage correlates with both global (mass, morphology, and environment) and local (surface brightness and metallicity) properties.

α/Fe] traced by H II regions from the CALIFA survey

Context. Differential enrichment between α and Fe-peak elements is known to be strongly connected with the shape of the star formation history (SFH), the star formation efficiency (SFE), the inflow and outflow of material, and even the shape of the initial mass function (IMF). However, beyond the Local Group, detailed explorations are mostly limited to early-type galaxies due to the lack of a good proxy for [α/Fe] in late-type ones, limiting our understanding of the chemical enrichment process. Aims. We intent to extend the explorations of [α/Fe] to late-type galaxies in order to understand the details of the differential enrichment process. Methods. We compare the gas-phase oxygen abundance with the luminosity-weighted stellar metallicity in an extensive catalogue of ∼25 000 H II regions extracted from the Calar Alto Legacy Integral Field Area (CALIFA) survey, an exploration that uses the integral-field spectroscopy of ∼900 galaxies and covers a wide range of masses and morphologies. This way, we define [O/Fe] as the ratio between both parameters, proposing it as an indirect proxy of the [α/Fe] ratio. This procedure is completely different from the one adopted to estimate [α/Fe] from high-resolution spectroscopic data for stars in our Galaxy. Results. We illustrate how the [O/Fe] parameter describes the chemical enrichment process in spiral galaxies, finding that: (i) it follows the decreasing pattern with [Fe/H] reported for the [α/Fe] ratio and (ii) its absolute scale depends on the stellar mass and the morphology. We reproduce both patterns using two different chemical evolution models, considering that galaxies with different stellar masses and morphologies present either different SFHs, SFEs, and inflow and outflow rates or a different maximum stellar mass cut for the IMF. We will explore the differential chemical enrichment using this new proxy galaxy by galaxy and region by region in further studies.

The EDGE–CALIFA survey: the local and global relations between Σ*, ΣSFR, and Σmol that regulate star formation

ABSTRACT We present a new characterization of the relations between star-formation rate, stellar mass, and molecular gas mass surface densities at different spatial scales across galaxies (from galaxy-wide to kpc scales). To do so, we make use of the largest sample combining spatially resolved spectroscopic information with CO observations, provided by the Extragalactic Database for Galaxy Evolution (EDGE)–Calar Alto Legacy Integral Field Area (CALIFA) survey, together with new single-dish CO observations obtained by the Atacama Pathfinder Experiment (APEX). We show that these relations are the same at the different scales explored, sharing the same distributions for the explored data, with similar slope, intercept, and scatter (when characterized by a simple power law). From this analysis, we propose that these relations are the projection of a single relation between the three properties that follows a distribution described well by a line in three-dimensional parameter space. Finally, we show that observed secondary relations between the residuals and the parameters considered are explained fully by the correlation between the uncertainties, and therefore have no physical origin. We discuss these results in the context of the hypothesis of self-regulation of the star-formation process.

Effects of environment on stellar metallicity profiles of late-type galaxies in the CALIFA survey

Aims. We explore the effects of environment in the evolution of late-type galaxies by studying the radial profiles of light- and mass-weighted metallicities of galaxies in two discrete environments: field and groups. Methods. We used a sample of 167 late-type galaxies with stellar masses of 9 ≤ log(M⋆/M⊙) ≤ 12 drawn from the Calar Alto Legacy Integral Field Area (CALIFA) survey. Firstly, we obtained light- and mass-weighted stellar metallicity profiles and stellar mass density profiles of these galaxies using publicly available data. We then classified them according to their environment into field and group galaxies. Finally, we studied the metallicity of galaxies in these two environments, including a comparison of the metallicity as a function of radius, at a characteristic scale, and as a function of stellar mass surface density. As metallicity depends on galaxy mass, we took special care throughout the study to compare, in all cases, subsamples of galaxies in groups and in the field that have similar masses. Results. We find significant differences between group and field late-type galaxies in terms of their metallicity: group galaxies are systematically higher in metallicity than their field counterparts. We find that field galaxies, in general, have metallicity profiles that show a negative gradient in their inner regions and a shallower profile at larger radii. This is in contrast to the metallicity profiles of galaxies in groups, which tend to be flat in the inner regions and to have a negative gradient in the outer parts. Regarding the metallicity at the characteristic radius of the luminosity profiles, we consistently find that it is higher for group galaxies irrespective of galaxy mass. At fixed local stellar surface mass density, group galaxies are again higher in metallicity, also the dependence of metallicity on surface density is less important for group galaxies. Conclusions. The evidence of a clear difference in metallicity between group and field galaxies as a function of mass, spatial scale, and local stellar mass density is indicative of the different evolutionary paths followed by galaxies in groups and in the field. We discuss some possible implications of the observed differences.

Ionized gas kinematics of massive elliptical galaxies in CALIFA and in cosmological zoom-in simulations

Context.Powerful active galactic nuclei (AGN) are supposed to play a key regulatory role on the evolution of their host galaxies by shaping the thermodynamic properties of their gas component. However, little is known as to the nature and the visibility timescale of the kinematical imprints of AGN-driven feedback. Gaining theoretical and observational insights into this subject is indispensable for a thorough understanding of the AGN-galaxy coevolution and could yield empirical diagnostics for the identification of galaxies that have experienced a major AGN episode in the past.Aims.We present an investigation of kinematical imprints of AGN feedback on the warm ionized gas medium (WIM) of massive early-type galaxies (ETGs). To this end, we take a two-fold approach that involves a comparative analysis of Hαvelocity fields in 123 local ETGs from the CALIFA (Calar Alto Legacy Integral Field Area Survey) integral field spectroscopy survey with 20 simulated galaxies from high-resolution hydrodynamic cosmological SPHgal simulations. The latter were resimulated for two modeling setups, one with and another without AGN feedback.Methods.In order to quantify the effects of AGN feedback on gas kinematics, we measured three parameters that probe deviations from simple regular rotation by using the kinemetry package. These indicators trace the possible presence of distinct kinematic components in Fourier space (k3, 5/k1), variations in the radial profile of the kinematic major axis (σPA), and offsets between the stellar and gas velocity fields (Δϕ). These quantities were monitored in the simulations from a redshift 3 to 0.2 to assess the connection between black hole accretion history, stellar mass growth, and the kinematical perturbation of the WIM.Results.Observed local massive galaxies show a broad range of irregularities, indicating disturbed warm gas motions, which is irrespective of being classified via diagnostic lines as AGN or not. Simulations of massive galaxies with AGN feedback generally exhibit higher irregularity parameters than without AGN feedback, which is more consistent with observations. Besides AGN feedback, other processes like major merger events or infalling gas clouds can lead to elevated irregularity parameters, but they are typically of shorter duration. More specifically,k3, 5/k1is most sensitive to AGN feedback, whereas Δϕis most strongly affected by gas infall.Conclusions.We conclude that even if the general disturbance of the WIM velocity is not a unique indicator for AGN feedback, irregularity parameters that are high enough to be consistent with observations can only be reproduced in simulations with AGN feedback. Specifically, an elevated value for the deviation from simple ordered motion is a strong sign for previous events of AGN activity and feedback.

The EDGE–CALIFA survey: using optical extinction to probe the spatially resolved distribution of gas in nearby galaxies

ABSTRACT We present an empirical relation between the cold gas surface density (Σgas) and the optical extinction (AV) in a sample of 103 galaxies from the Extragalactic Database for Galaxy Evolution (EDGE) survey. This survey provides CARMA interferometric CO observations for 126 galaxies included in the Calar Alto Legacy Integral Field Area (CALIFA) survey. The matched, spatially resolved nature of these data sets allows us to derive the Σgas–AV relation on global, radial, and kpc (spaxel) scales. We determine AV from the Balmer decrement (H α/H β). We find that the best fit for this relation is $\Sigma _{\rm gas}\,(\rm {M_\odot \,pc}^{-2}) \sim 26 \times {\rm \mathit{ A}_\mathit{ V}} \,(\rm mag)$, and that it does not depend on the spatial scale used for the fit. However, the scatter in the fits increases as we probe smaller spatial scales, reflecting the complex relative spatial distributions of stars, gas, and dust. We investigate the Σgas/AV ratio on radial and spaxel scales as a function of $\mathrm{EW(H\,\alpha)}$. We find that at larger values of $\mathrm{EW({H\,\alpha })}$ (i.e. actively star-forming regions) this ratio tends to converge to twice the value expected for a foreground dust screen geometry (∼30 $\mathrm{M_{\odot } \, pc^{-2} \, mag^{-1}}$). On radial scales, we do not find a significant relation between the Σgas/AV ratio and the ionized gas metallicity. We contrast our estimates of Σgas using AV with compilations in the literature of the gas fraction on global and radial scales as well as with well-known scaling relations such as the radial star formation law and the Σgas–Σ* relation. These tests show that optical extinction is a reliable proxy for estimating Σgas in the absence of direct sub/millimeter observations of the cold gas.

Mysterious Coherence in Several-megaparsec Scales between Galaxy Rotation and Neighbor Motion

Abstract In our recent report, observational evidence supports that the rotational direction of a galaxy tends to be coherent with the average motion of its nearby neighbors within 1 Mpc. We extend the investigation to neighbors at farther distances in order to examine if such dynamical coherence is found even in large scales. The Calar Alto Legacy Integral Field Area (CALIFA) survey data and the NASA-Sloan Atlas (NSA) catalog are used. From the composite map of velocity distribution of “neighbor” galaxies within 15 Mpc from the CALIFA galaxies, the composite radial profiles of the luminosity-weighted mean velocity of neighbors are derived. These profiles show unexpectedly strong evidence of the dynamical coherence between the rotation of the CALIFA galaxies and the average line-of-sight motion of their neighbors within several-megaparsec distances. Such a signal is particularly strong when the neighbors are limited to red ones: the luminosity-weighted mean velocity at 1 < D ≤ 6 Mpc is as large as 30.6 ± 10.9 km s−1 (2.8σ significance to random spin-axis uncertainty) for central rotation (R ≤ R e ). In the comparison of several subsamples, the dynamical coherence tends to be marginally stronger for the diffuse or kinematically well-aligned CALIFA galaxies. For this mysterious coherence in large scales, we cautiously suggest a scenario in which it results from a possible relationship between the long-term motion of a large-scale structure and the rotations of galaxies in it.

The stellar velocity dispersion in nearby spirals: radial profiles and correlations

Abstract The stellar velocity dispersion, σ, is a quantity of crucial importance for spiral galaxies, where it enters fundamental dynamical processes such as gravitational instability and disc heating. Here we analyse a sample of 34 nearby spirals from the Calar Alto Legacy Integral Field Area (CALIFA) spectroscopic survey, deproject the line-of-sight σ to σR and present reliable radial profiles of σR as well as accurate measurements of ⟨σR⟩, the radial average of σR over one effective (half-light) radius. We show that there is a trend for σR to increase with decreasing R, that ⟨σR⟩ correlates with stellar mass (M⋆) and tested correlations with other galaxy properties. The most significant and strongest correlation is the one with M⋆: $\langle \sigma _{R}\rangle \propto M_{\star }^{0.5}$. This tight scaling relation is applicable to spiral galaxies of type Sa–Sd and stellar mass M⋆ ≈ 109.5–1011.5 M⊙. Simple models that relate σR to the stellar surface density and disc scale length roughly reproduce that scaling, but overestimate ⟨σR⟩ significantly.

Spotting the differences between active and non-active twin galaxies on kpc-scales: a pilot study

We present a pilot study aimed to identify large-scale galaxy properties that could play a role in activating a quiescent nucleus. To do so, we compare the properties of two isolated nearby active galaxies and their non-active twins selected from the Calar Alto Legacy Integral Field Area (CALIFA) survey. This pilot sample includes two barred and two unbarred galaxies. We characterise the stellar and ionised gas kinematics and also their stellar content. We obtain simple kinematic models by fitting the full stellar and ionised gas velocity fields and just the approaching/receding sides. We find that the analysed active galaxies present lopsided disks and higher values of the global stellar angular momentum ($\lambda_{R}$) than their non-active twins. This could be indicating that the stellar disks of the AGN gained angular momentum from the inflowing gas that triggered the nuclear activity. The inflow of gas could have been produced by a twisted disk instability in the case of the unbarred AGN, and by the bar in the case of the barred AGN. In addition, we find that the central regions of the studied active galaxies show older stellar populations than their non-active twins. The next step is to statistically explore these galaxy properties in a larger sample of twin galaxies.

Galaxy Rotation Coherent with the Motions of Neighbors: Discovery of Observational Evidence

Abstract We present our discovery of observational evidence for the coherence between galaxy rotation and the average line-of-sight motion of neighbors. We use the Calar Alto Legacy Integral Field Area (CALIFA) survey data analyzed with the Python CALIFA STARLIGHT Synthesis Organizer platform, and the NASA-Sloan Atlas catalog. After estimating the projected angular momentum vectors of 445 CALIFA galaxies, we build composite maps of their neighbor galaxies on the parameter space of line-of-sight velocity versus projected distance. The composite radial profiles of the luminosity-weighted mean velocity of neighbors show striking evidence for dynamical coherence between the rotational direction of the CALIFA galaxies and the average moving direction of their neighbor galaxies. The signal of such dynamical coherence is significant for the neighbors within 800 kpc from the CALIFA galaxies, for which the luminosity-weighted mean velocity is as large as 61.7 ± 17.6 km s−1 (3.5σ significance to the bootstrap uncertainty) when the angular momentum is measured at R e < R ≤ 2R e of each CALIFA galaxy. In the comparison of the subsamples, we find that faint, blue, or kinematically misaligned galaxies show stronger coherence with neighbor motions than bright, red, or kinematically well-aligned galaxies do. Our results indicate that (1) the rotation of a galaxy (particularly at its outskirt) is significantly influenced by interactions with its neighbors up to 800 kpc, (2) the coherence is particularly strong between faint galaxies and bright neighbors, and (3) galaxy interactions often cause internal kinematic misalignment or possibly even kinematically distinct cores.

Barlenses in the CALIFA survey: Combining photometric and stellar population analyses

Aims: It is theoretically predicted that, at low galaxy inclinations, boxy/peanut bar components have a barlens appearance of a round central component embedded in the narrow bar. We investigate barlenses in the Calar Alto Legacy Integral Field Area (CALIFA) survey galaxies, studying their morphologies, stellar populations, and metallicities. We show that, when present, barlenses account for a significant portion of light of photometric bulges, i.e., the excess light on top of the disks, which highlights the importance of bars in accumulating central galaxy mass concentrations in the cosmic timescale. Methods: We made multi-component decompositions for a sample of 46 barlens galaxies drawn from the CALIFA survey, where M⋆/M⊙ = 109.7 − 1011.4 and z = 0.005 − 0.03. Unsharp masks of the Sloan Digital Sky Survey (SDSS) r′-band mosaics were used to identify the boxy/peanut or X-shaped features. Barlenses are identified in the images using our simulation snapshots as an additional guide. Our decompositions with GALFIT include bulges, disks, and bars as well as barlenses as a separate component. For 26 of the decomposed galaxies the CALIFA DR2 V500 grating data cubes were used to explore stellar ages and metallicities at the regions of various structure components. Results: We find that 25 ± 2% of the 1064 galaxies in the whole CALIFA sample show either X-shaped or barlens features. In the decomposed galaxies with barlenses, on average 13% ± 2% of the total galaxy light belongs to this component, leaving less than 10% for possible separate bulge components. Most importantly, bars and barlenses are found to have similar cumulative stellar age and metallicity distributions. The metallicities in barlenses are on average near solar, but exhibit a large range. In some of the galaxies barlenses and X-shaped features appear simultaneously, in which case the bar origin of the barlens is unambiguous. Conclusion: This is the first time that a combined morphological and stellar population analysis is used to study barlenses. We show that their stars are accumulated in a prolonged time period concurrently with the evolution of the narrow bar.

Cosmic evolution of the spatially resolved star formation rate and stellar mass of the CALIFA survey

We investigate the cosmic evolution of the absolute and specific star formation rate (SFR, sSFR) of galaxies as derived from a spatially resolved study of the stellar populations in a set of 366 nearby galaxies from the Calar Alto Legacy Integral Field Area (CALIFA) survey. The sample spans stellar masses from M⋆ ~ 109 to 1012M⊙ and a wide range of Hubble types. The analysis combines images obtained with the Galaxy Evolution Explorer (GALEX; far-ultraviolet and near-ultraviolet) and Sloan Digital Sky Survey (SDSS; u, g, r, i, z) with the 4000 Å break, Hβ, and [MgFe]′ indices measured from the CALIFA data cubes to constrain parametric models for the star formation history (SFH), which are then used to study the cosmic evolution of the SFR density (ρSFR), the sSFR, the main sequence of star formation (MSSF), and the stellar mass density (ρ⋆). Several SFH laws are used to fit the observational constrains. A delayed-τ model, SFR ∝ (t0 − t)exp(−(t0 − t)∕τ), provides the best results, in good agreement with those obtained from cosmological surveys. Our main results from this model are that (a) the mass currently in the inner (≤0.5 half-light radius, HLR) regions formed at earlier epochs than the mass in the outer (1–2 HLR) regions of galaxies. The time since the onset of the star formation is longer in the inner regions (t0 ~ 13−10 Gyr) than in the outer ones (t0 ~ 11−9 Gyr) for all the morphologies, while the e-folding timescale τ in the inner region is similar to or shorter than in the outer regions. These results confirm that galaxies of any Hubble type grow inside-out. (b) The sSFR declines rapidly as the Universe evolves, and faster for early- than for late-type galaxies, and for the inner than for the outer regions of galaxies. (c) The evolution of ρSFR and ρ⋆ agrees well with results from cosmological surveys, particularly with the recent results from the Galaxy And Mass Assembly (GAMA), the G10-Cosmological Evolution Survey (COSMOS), and the 3D Hubble Space Telescope (HST) survey. At low redshift, z ≤ 0.5, most star formation takes place in the outer regions of late spiral galaxies, while at z > 2, the inner regions of the progenitors of the current E and S0 are the main contributors to ρSFR. (d) Similarly, the inner regions of galaxies are the main contributor to ρ⋆ at z > 0.5, growing their mass faster than the outer regions, with a lookback time at 50% ρ⋆ of t50 ~ 9 and 6 Gyr for the inner and outer regions. (e) The MSSF follows a power law at high redshift, with the slope evolving with time but always remaining sub-linear, in good agreement with the Illustris simulation. (f) In agreement with galaxy surveys at different redshifts, the average SFH of CALIFA galaxies indicates that galaxies grow their mass mainly in a mode that is well represented by a delayed-τ model, with the peak at z ~ 2 and an e-folding time of ~3.9 Gyr.

Spatially Resolved Stellar Kinematics from LEGA-C: Increased Rotational Support in z ∼ 0.8 Quiescent Galaxies

Abstract We present stellar rotation curves and velocity dispersion profiles for 104 quiescent galaxies at z = 0.6–1 from the Large Early Galaxy Astrophysics Census (LEGA-C) spectroscopic survey. Rotation is typically probed across 10–20 kpc, or to an average of 2.7R e . Combined with central stellar velocity dispersions (σ 0) this provides the first determination of the dynamical state of a sample selected by a lack of star formation activity at large lookback time. The most massive galaxies (M ⋆ > 2 × 1011 M ⊙) generally show no or little rotation measured at 5 kpc ( ∣ V 5 ∣ / σ 0 < 0.2 in eight of ten cases), while ∼64% of less massive galaxies show significant rotation. This is reminiscent of local fast- and slow-rotating ellipticals and implies that low- and high-redshift quiescent galaxies have qualitatively similar dynamical structures. We compare ∣ V 5 ∣ / σ 0 distributions at z ∼ 0.8 and the present day by re-binning and smoothing the kinematic maps of 91 low-redshift quiescent galaxies from the Calar Alto Legacy Integral Field Area (CALIFA) survey and find evidence for a decrease in rotational support since z ∼ 1. This result is especially strong when galaxies are compared at fixed velocity dispersion; if velocity dispersion does not evolve for individual galaxies then the rotational velocity at 5 kpc was an average of 94 ± 22% higher in z ∼ 0.8 quiescent galaxies than today. Considering that the number of quiescent galaxies grows with time and that new additions to the population descend from rotationally supported star-forming galaxies, our results imply that quiescent galaxies must lose angular momentum between z ∼ 1 and the present, presumably through dissipationless merging, and/or that the mechanism that transforms star-forming galaxies also reduces their rotational support.

The EDGE–CALIFA survey: validating stellar dynamical mass models with CO kinematics

Abstract Deriving circular velocities of galaxies from stellar kinematics can provide an estimate of their total dynamical mass, provided a contribution from the velocity dispersion of the stars is taken into account. Molecular gas (e.g. CO), on the other hand, is a dynamically cold tracer and hence acts as an independent circular velocity estimate without needing such a correction. In this paper, we test the underlying assumptions of three commonly used dynamical models, deriving circular velocities from stellar kinematics of 54 galaxies (S0-Sd) that have observations of both stellar kinematics from the Calar Alto Legacy Integral Field Area (CALIFA) survey, and CO kinematics from the Extragalactic Database for Galaxy Evolution (EDGE) survey. We test the asymmetric drift correction (ADC) method, as well as Jeans, and Schwarzschild models. The three methods each reproduce the CO circular velocity at 1Re to within 10 per cent. All three methods show larger scatter (up to 20 per cent) in the inner regions (R < 0.4Re) that may be due to an increasingly spherical mass distribution (which is not captured by the thin disc assumption in ADC), or non-constant stellar M/L ratios (for both the JAM and Schwarzschild models). This homogeneous analysis of stellar and gaseous kinematics validates that all three models can recover Mdyn at 1Re to better than 20 per cent, but users should be mindful of scatter in the inner regions where some assumptions may break down.

Spiral arms in CALIFA galaxies traced by non-circular velocities, abundances and extinctions

We derive maps of the observed velocity of ionized gas, the oxygen abundance, and the extinction (Balmer decrement) across the area of the four spiral galaxies NGC36, NGC180, NGC6063, and NGC7653 from integral field spectroscopy obtained by the Calar Alto Legacy Integral Field Area (CALIFA) survey. We searched for spiral arms through Fourier analysis of the spatial distribution of three tracers (non-circular motion, enhancement of the oxygen abundance, and of the extinction) in the discs of our target galaxies. The spiral arms (two-armed logarithmic spirals in the deprojected map) are shown in each target galaxy for each tracer considered. The pitch angles of the spiral arms in a given galaxy obtained with the three different tracers are close to each other. The enhancement of the oxygen abundance in the spiral arms as compared to the abundance in the interarm regions at a given galactocentric distance is small; within a few per cent. We identified a metallicity gradient in our target galaxies. Both barred galaxies in our sample show flatter gradients than the two galaxies without bars. Galactic inclination, position angle of the major axis, and the rotation curve were also obtained for each target galaxy using the Fourier analysis of the two-dimensional velocity map.