Deconstructing double-barred galaxies in 2D and 3D. II. Two distinct groups of inner bars

The intrinsic photometric properties of inner and outer stellar bars within 17 double-barred galaxies are thoroughly studied through a photometric analysis consisting of: i) two-dimensional multi-component photometric decompositions, and ii) three-dimensional statistical deprojections for measuring the thickening of bars, thus retrieving their 3D shape. The results are compared with previous measurements obtained with the widely used analysis of integrated light. Large-scale bars in single- and double-barred systems show similar sizes, and inner bars may be longer than outer bars in different galaxies. We find two distinct groups of inner bars attending to their in-plane length and ellipticity, resulting in a bimodal behaviour for the inner/outer bar length ratio. Such bimodality is related neither to the properties of the host galaxy nor the dominant bulge, and it does not show a counterpart in the dimension off the disc plane. The group of long inner bars lays at the lower end of the outer bar length vs. ellipticity correlation, whereas the short inner bars are out of that relation. We suggest that this behaviour could be due to either a different nature of the inner discs from which the inner bars are dynamically formed, or a different assembly stage for the inner bars. This last possibility would imply that the dynamical assembly of inner bars is a slow process taking several Gyr to happen. We have also explored whether all large-scale bars are prone to develop an inner bar at some stage of their lives, possibility we cannot fully confirm or discard.Comment: 14 pages, 8 figures, 1 table. Accepted for publication in MNRA

Stellar kinematics in double-barred galaxies: the sigma-hollows

We present SAURON integral-field stellar velocity and velocity dispersion maps for four double-barred early-type galaxies: NGC2859, NGC3941, NGC4725 and NGC5850. The presence of the inner bar does not produce major changes in the line-of-sight velocity, but it appears to have an important effect in the stellar velocity dispersion maps: we find two sigma-hollows of amplitudes between 10 and 40 km/s on either side of the center, at the ends of the inner bars. We have performed numerical simulations to explain these features. Ruling out other possibilities, we conclude that the sigma-hollows are an effect of the contrast between two kinematically different components: the high velocity dispersion of the bulge and the more ordered motion (low velocity dispersion) of the inner bar.Comment: 5 pages, 2 figures. Accepted for publication in ApJ Letter

CATÁLOGO DE LAS PLANTAS VASCULARES ESPONTÁNEAS Y CULTIVADAS DE LA REGIÓN DE MURCIA. II. MAGNOLIACEAE-PAPAVERACEAE

This publication is the second issue of a check list of wild and relevant cultivate plants in the Region of Murcia (South-eastern Spain). The model of exposition and all the data about the format of the presented catalogue come explained in a precedent paper (ALCARAZ et al. 1993). The present paper includes a catalogue of 69 taxa of vascular plants.Esta publicación constituye la segunda entrega de una serie sobre el catálogo provisional de las plantas vasculares silvestres, así como las más destacadas de las ornamentales y agrícolas de la Región de Murcia. El modelo de exposición y todos los datos concernientes al formato del catálogo se presentaron en la entrega anterior (ALCARAZ et al., 1993). En total se incluyen en este trabajo 69 táxones de Angiospermae

Superdense massive galaxies in the Nearby Universe

Superdense massive galaxies (r_e~1 kpc; M~10^{11} Msun) were common in the early universe (z>1.5). Within some hierarchical merging scenarios, a non-negligible fraction (1-10%) of these galaxies is expected to survive since that epoch retaining their compactness and presenting old stellar populations in the present universe. Using the NYU Value-Added Galaxy Catalog from the SDSS Data Release 6 we find only a tiny fraction of galaxies (~0.03%) with r_e<1.5 kpc and M_*>8x10^{10} Msun in the local Universe (z<0.2). Surprinsingly, they are relatively young (~2 Gyr) and metal-rich ([Z/H]~0.2). The consequences of these findings within the current two competing size evolution scenarios for the most massive galaxies ("dry" mergers vs "puffing up" due to quasar activity) are discussed.Comment: Accepted for publication in ApJ Letters; 3 figure

Smooth kinematic and metallicity gradients between the Milky Way's nuclear star cluster and nuclear stellar disc. Different components of the same structure?

The innermost regions of most galaxies are characterised by the presence of extremely dense nuclear star clusters. Nevertheless, these clusters are not the only stellar component present in galactic nuclei, where larger stellar structures known as nuclear stellar discs, have also been found. Understanding the relation between nuclear star clusters and nuclear stellar discs is challenging due to the large distance towards other galaxies which limits their analysis to integrated light. The Milky Way's centre, at only 8 kpc, hosts a nuclear star cluster and a nuclear stellar disc, constituting a unique template to understand their relation and formation scenario. We aim to study the kinematics and stellar metallicity of stars from the Milky Way's nuclear star cluster and disc to shed light on the relation between these two Galactic centre components. We used publicly available photometric, proper motions, and spectroscopic catalogues to analyse a region of $\sim2.8'\times4.9'$ centred on the Milky Way's nuclear star cluster. We built colour magnitude diagrams, and applied colour cuts to analyse the kinematic and metallicity distributions of Milky Way's nuclear star cluster and disc stars with different extinction along the line of sight. We detect kinematics and metallicity gradients for the analysed stars along the line of sight towards the Milky Way's nuclear star cluster, suggesting a smooth transition between the nuclear stellar disc and cluster. We also find a bi-modal metallicity distribution for all the analysed colour bins, which is compatible with previous work on the bulk population of the nuclear stellar disc and cluster. Our results suggest that these two Galactic centre components might be part of the same structure with the Milky Way's nuclear stellar disc being the grown edge of the nuclear star cluster.Comment: Submitted to A&A. 13 pages, 9 figure