We investigate the relations between the properties of bars and their host galaxies in a sample of 77 nearby barred galaxies, spanning a wide range of morphological types and luminosities, with 34 ...SB0-SBa and 43 SBab-SBc galaxies. The sample includes all the galaxies with reliable direct measurement of their bar pattern speed based on long-slit or integral-field stellar spectroscopy using the Tremaine-Weinberg method. We limited our analysis to the galaxies with a relatively small relative error on the bar pattern speed (≤50%) and that do not host an ultrafast bar. For each galaxy, we collected the radius, strength, pattern speed, corotation radius, and rotation rate for the bar and we also collected the Hubble type and absolute SDSS
r
-band magnitude. We also used literature bulge-to-total luminosity ratios for a subsample of 53 galaxies with an available photometric decomposition. We confirmed earlier observational findings that longer bars rotate at lower bar pattern speeds, shorter bars are weaker, and bars with a low rate of bar rotation rotate at faster bar pattern speeds and have smaller corotation radii. In addition, we found that stronger bars rotate at lower bar pattern speeds, as predicted from the interchange of angular momentum during bar evolution, which in turn may depend on different galaxy properties. Moreover, we report that brighter galaxies host longer bars, which rotate at lower bar pattern speeds and have larger corotation radii. This result is in agreement with a scenario of downsizing in bar formation, if more massive galaxies formed earlier and had sufficient time to slow down, grow in length, and push corotation outwards.
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Context. Historically, galaxy bulges were thought to be single-component objects at the center of galaxies. However, this picture is now questioned since different bulge types with different ...formation paths, namely classical and pseudobulges, have been found coexisting within the same galaxy. Aims. We study the incidence and nature of composite bulges in a sample of 10 face-on barred galaxies to constrain the formation and evolutionary processes of the central regions of disk galaxies. Methods. We analyze the morphological, photometric, and kinematic properties of each bulge. Then, by using a case-by-case analysis we identify composite bulges and classify every component into a classical or pseudobulge. In addition, bar-related boxy/peanut (B/P) structures were also identified and characterized. Results. We find only three galaxies hosting a single-component bulge (two pseudobulges and one classical bulge). Thus, we demonstrate the high incidence of composite bulges (70%) in barred galaxies. We find evidence of composite bulges coming in two main types based on their formation: secular-built and merger- and secular-built. We denote as secular-built those composite bulges that are made up of structures associated with secular processes, such as pseudobulges, central disks, or B/P bulges. We find four composite bulges of this kind in our sample. On the other hand, merger- and secular-built bulges are those where structures with different formation paths coexist within the same galaxy, i.e., a classical bulge coexisting with a secular-built structure (pseudobulge, central disk, or B/P). Three bulges of this kind were found in the sample. We notice the importance of detecting kinematic structures such as σ-drops to identify composite bulges. A high percentage (~80%) of galaxies were found to host σ-drops or σ-plateaus in our sample, revealing their high incidence in barred galaxies. Conclusions. The high frequency of composite bulges in barred galaxies points toward a complex formation and evolutionary scenario. Moreover, the evidence of coexisting merger- and secular-built bulges reinforce this idea. We discuss how the presence of different bulge types with different formation histories and timescales can constrain current models of bulge formation.
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We present the stellar kinematic maps of a large sample of galaxies from the integral-field spectroscopic survey CALIFA. The sample comprises 300 galaxies displaying a wide range of morphologies ...across the Hubble sequence, from ellipticals to late-type spirals. This dataset allows us to homogeneously extract stellar kinematics up to several effective radii. In this paper, we describe the level of completeness of this subset of galaxies withrespect to the full CALIFA sample, as well as the virtues and limitations of the kinematic extraction compared to other well-known integral-field surveys. In addition, we provide averaged integrated velocity dispersion radial profiles for different galaxy types, which are particularly useful to apply aperture corrections for single aperture measurements or poorly resolved stellar kinematics of high-redshift sources. The work presented in this paper sets the basis for the study of more general properties of galaxies that will be explored in subsequent papers of the survey.
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Abstract
We study a sample of 28 S0 galaxies extracted from the integral field spectroscopic (IFS) survey Calar Alto Legacy Integral Field Area. We combine an accurate two-dimensional (2D) ...multicomponent photometric decomposition with the IFS kinematic properties of their bulges to understand their formation scenario. Our final sample is representative of S0s with high stellar masses (M⋆/M⊙ > 1010). They lay mainly on the red sequence and live in relatively isolated environments similar to that of the field and loose groups. We use our 2D photometric decomposition to define the size and photometric properties of the bulges, as well as their location within the galaxies. We perform mock spectroscopic simulations mimicking our observed galaxies to quantify the impact of the underlying disc on our bulge kinematic measurements (λ and v/σ). We compare our bulge corrected kinematic measurements with the results from Schwarzschild dynamical modelling. The good agreement confirms the robustness of our results and allows us to use bulge deprojected values of λ and v/σ. We find that the photometric (n and B/T) and kinematic (v/σ and λ) properties of our field S0 bulges are not correlated. We demonstrate that this morpho-kinematic decoupling is intrinsic to the bulges and it is not due to projection effects. We conclude that photometric diagnostics to separate different types of bulges (disc-like versus classical) might not be useful for S0 galaxies. The morpho-kinematics properties of S0 bulges derived in this paper suggest that they are mainly formed by dissipational processes happening at high redshift, but dedicated high-resolution simulations are necessary to better identify their origin.
The early-type galaxy (ETG) mass-size relation has largely been studied to understand how these galaxies assembled their mass. One key observational result of the last years is that massive galaxies ...increased their size by a factor of a few at fixed stellar mass from z ~ 2. Hierarchical models favor minor mergers as a plausible driver of this size growth. Some of these models predict a significant environmental dependence in the sense that galaxies residing in more massive halos tend to be larger than galaxies in lower mass halos, at fixed stellar mass and redshift. At present, observational results of this environmental dependence are contradictory. In this paper we revisit this issue in the local universe, by investigating how the sizes of massive ETGs depend on a large-scale environment using an updated and accurate sample of ETGs in different environments-field, group, and clusters-from the Sloan Digital Sky Survey DR7. Our analysis does not show any significant environmental dependence of the sizes of central and satellite ETGs at fixed stellar mass at z ~ 0. The size-mass relation of early-type galaxies at z ~ 0 seems to be universal, i.e., independent of the mass of the host halo and of the position of the galaxy in that halo (central or satellite). The result is robust to different galaxy selections based on star formation, morphology, or central density. Considering our observational errors and the size of the sample, any size ratio larger than 30%-40% between massive galaxies (log(M sub(*)/M sub(middot in circle)) > 11) living in clusters and in the field can be ruled out at 3sigma level.
We present an automated morphological classification in 4 types (E, S0, Sab, Scd) of ~700 000 galaxies from the SDSS DR7 spectroscopic sample based on support vector machines. The main new ...property of the classification is that we associate a probability to each galaxy of being in the four morphological classes instead of assigning a single class. The classification is therefore better adapted to nature where we expect a continuous transition between different morphological types. The algorithm is trained with a visual classification and then compared to several independent visual classifications including the Galaxy Zoo first-release catalog. We find a very good correlation between the automated classification and classical visual ones. The compiled catalog is intended for use in different applications and is therefore freely available through a dedicated webpage⋆ and soon from the CasJobs database.
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The dynamics of globular cluster systems (GCSs) around galaxies are often used to assess the total enclosed mass, and even to constrain the dark matter distribution. The GCS of a galaxy is typically ...assumed to be in dynamical equilibrium within the potential of the host galaxy. However cluster galaxies are subjected to a rapidly evolving and, at times, violently destructive tidal field. We investigate the impact of the harassment on the dynamics of GCs surrounding early-type cluster dwarfs, using numerical simulations. We find that the dynamical behaviour of the GCS is strongly influenced by the fraction of bound dark matter f
DM remaining in the galaxy. Only when f
DM falls to ∼15 per cent do stars and GCs begin to be stripped. Still the observed GC velocity dispersion can be used to measure the true enclosed mass to within a factor of 2, even when f
DM falls as low as ∼3 per cent. This is possible partly because unbound GCs quickly separate from the galaxy body. However even the distribution of bound GCs may spatially expand by a factor of 2-3. Once f
DM falls into the <3 per cent regime, the galaxy is close to complete disruption, and GCS dynamics can no longer be used to reliably estimate the enclosed mass. In this regime, the remaining bound GCS may spatially expand by a factor of 4 to 8. It may be possible to test if a galaxy is in this regime by measuring the dynamics of the stellar disc. We demonstrate that if a stellar disc is rotationally supported, it is likely that a galaxy has sufficient dark matter that the dynamics of the GCS can be used to reliably estimate the enclosed mass.
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