On the lack of stellar bars in Coma dwarf galaxies

We present a study of the bar fraction in the Coma cluster galaxies based on a sample of ~190 galaxies selected from the SDSS-DR6 and observed with the Hubble Space Telescope (HST) Advanced Camera for Survey (ACS). The unprecedented resolution of the HST-ACS images allows us to explore the presence of bars, detected by visual classification, throughout a luminosity range of 9 mag (-23 < M_r < -14), permitting us to study the poor known region of dwarf galaxies. We find that bars are hosted by galaxies in a tight range of both luminosities (-22 < M_r < -17) and masses (10^9 < M*/Msun < 10^11). In addition, we find that the bar fraction does not vary significantly when going from the center to the cluster outskirts, implying that cluster environment plays a second-order role in bar formation/evolution. The shape of the bar fraction distribution with respect to both luminosity and mass is well matched by the luminosity distribution of disk galaxies in Coma, indicating that bars are good tracers of cold stellar disks.Comment: 2 pages, 1 figure, to appear in the proceedings of the conference "A Universe of Dwarf Galaxies" (Lyon, June 14-18, 2010

The origin of bulges and discs in the CALIFA survey – I. Morphological evolution

JMA acknowledge support from the Spanish Ministerio de Economia y Competitividad (MINECO) by the grant AYA2017-83204-P and the Programa Operativo FEDER Andalucia 2014-2020 in collaboration with the Andalucian Office for Economy and Knowledge. AdLC acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) under grants AYA201677237-C3-1-P and RTI2018-096188-B-I00, the latter is partly funded by the European Regional Development Fund (ERDF). SFS thanks the projects ConaCyt CB-285080, FC-2016-01-1916, and PAPIIT IN100519. This paper is based on data from the Calar Alto Legacy Integral Field Area Survey, CALIFA, funded by the Spanish Ministry of Science under grant ICTS-2009-10, and the Centro Astronomico Hispano-Aleman. This paper is based on observations collected at the Centro Astronomico Hispano Aleman (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut fur Astronomie and the Instituto de Astrofisica de Andalucia.This series of papers aims at understanding the formation and evolution of non-barred disc galaxies. We use the new spectro-photometric decomposition code, C2D, to separate the spectral information of bulges and discs of a statistically representative sample of galaxies from the CALIFA survey. Then, we study their stellar population properties analysing the structure-independent datacubes with the PIPE3D algorithm. We find a correlation between the bulge-to-total (B/T) luminosity (and mass) ratio and galaxy stellar mass. The B/T mass ratio has only a mild evolution with redshift, but the bulge-to-disc (B/D) mass ratio shows a clear increase of the disc component since redshift z 10.5). The relation holds for bulges but not for discs when using their individual stellar masses. We find a negligible evolution of the mass-size relation for both the most massive (log(M-star,M-b,M-d/M-circle dot) > 10) bulges and discs. For lower masses, discs show a larger variation than bulges. We also find a correlation between the Sersic index of bulges and both galaxy and bulge stellar mass, which does not hold for the disc mass. Our results support an inside-out formation of nearby non-barred galaxies, and they suggest that (i) bulges formed early-on and (ii) they have not evolved much through cosmic time. However, we find that the early properties of bulges drive the future evolution of the galaxy as a whole, and particularly the properties of the discs that eventually form around them.Spanish Government AYA2017-83204-PPrograma Operativo FEDER Andalucia 2014-2020Andalucian Office for Economy and KnowledgeEuropean CommissionConsejo Nacional de Ciencia y Tecnologia (CONACyT) CB-285080Spanish Government ICTS-2009-10Centro Astronomico Hispano-AlemanPrograma de Apoyo a Proyectos de Investigacion e Innovacion Tecnologica (PAPIIT) IN100519Spanish Government AYA201677237-C3-1-P RTI2018-096188-B-I00 FC-2016-01-191

Properties of bars in the local universe

We studied the fraction and properties of bars in a sample of about 3000 galaxies extracted from SDSS-DR5. This represents a volume limited sample with galaxies located between redshift 0.01-20, and inclination i < 60. Interacting galaxies were excluded from the sample. The fraction of barred galaxies in our sample is 45%. We found that 32% of S0s, 55% of early-type spirals, and 52% of late-type spirals are barred galaxies. The bars in S0s galaxies are weaker than those in later-type galaxies. The bar length and galaxy size are correlated, being larger bars located in larger galaxies. Neither the bar strength nor bar length correlate with the local galaxy density. On the contrary, the bar properties correlate with the properties of their host galaxies. Galaxies with higher central light concentration host less and weaker bars.Comment: 2 pages, 1 figure to appear in the proceedings of "Formation and Evolution of Galaxy Disks", Rome, October 2007, Eds. J. Funes and E. M. Corsin

The stellar host in star-forming low-mass galaxies: Evidence for two classes

The morphological evolution of star-forming galaxies provides important clues to understand their physical properties, as well as the triggering and quenching mechanisms of star formation. We aim at connecting morphology and star-formation properties of low-mass galaxies (median stellar mass $\sim$ 10$^{8.5}$ M$_{\odot}$) at low redshift ($z<0.36$). We use a sample of medium-band selected star-forming galaxies from the GOODS-North field. H$\alpha$ images for the sample are created combining both spectral energy distribution fits and HST data. Using them, we mask the star forming regions to obtain an unbiased two-dimensional model of the light distribution of the host galaxies. For this purpose we use $\texttt{PHI}$, a new Bayesian photometric decomposition code. We apply it independently to 7 HST bands assuming a S\'ersic surface brightness model. Star-forming galaxy hosts show low S\'ersic index (with median $n$ $\sim$ 0.9), as well as small sizes (median $R_e$ $\sim$ 1.6 kpc), and negligible change of the parameters with wavelength (except for the axis ratio, which grows with wavelength). Using a clustering algorithm, we find two different classes of star-forming galaxies: A more compact, redder, and high-$n$ (class A) and a more extended, bluer and lower-$n$ one (class B). We also find evidence that the first class is more spheroidal-like. In addition, we find that 48% of the analyzed galaxies present negative color gradients (only 5% are positive). The host component of low-mass star-forming galaxies at $z<0.36$ separates into two different classes, similar to what has been found for their higher mass counterparts. The results are consistent with an evolution from class B to class A. Several mechanisms from the literature, like minor and major mergers, and violent disk instability, can explain the physical process behind the likely transition between the classes. [abridged]Comment: Accepted for publication in Astronomy & Astrophysics. 13 pages, 11 figure

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

A photometric analysis of Abell 1689: two-dimensional multi-structure decomposition, morphological classification, and the Fundamental Plane

We present a photometric analysis of 65 galaxies in the rich cluster Abell 1689 at $z=0.183$, using the Hubble Space Telescope Advanced Camera for Surveys archive images in the rest-frame $V$-band. We perform two-dimensional multi-component photometric decomposition of each galaxy adopting different models of the surface-brightness distribution. We present an accurate morphological classification for each of the sample galaxies. For 50 early-type galaxies, we fit both a de Vaucouleurs and S\'ersic law; S0s are modelled by also including a disc component described by an exponential law. Bars of SB0s are described by the profile of a Ferrers ellipsoid. For the 15 spirals, we model a S\'ersic bulge, exponential disc, and, when required, a Ferrers bar component. We derive the Fundamental Plane by fitting 40 early-type galaxies in the sample, using different surface-brightness distributions. We find that the tightest plane is that derived by S\'ersic bulges. We find that bulges of spirals lie on the same relation. The Fundamental Plane is better defined by the bulges alone rather than the entire galaxies. Comparison with local samples shows both an offset and rotation in the Fundamental Plane of Abell 1689.Comment: 53 pages, 71 figures, MNRAS in pres

Starburst galaxies in the COSMOS field : clumpy star-formation at redshift 0 < z <0.5

This work has been funded by the Spanish MINECO, Grant ESTALLIDOS, AYA2013-47742-C4-2P and AYA2010-21887-C04-04. J.M.A. acknowledges support from the European Research Council Starting Grant SEDMorph (P.I. V. Wild). R.H.G. acknowledges the FPI grant from MINECO within ESTALLIDOS project.Context. At high redshift, starburst galaxies present irregular morphologies with 10-20% of their star formation occurring in giant clumps. These clumpy galaxies are considered the progenitors of local disk galaxies. To understand the properties of starbursts at intermediate and low redshift, it is fundamental to track their evolution and the possible link with the systems at higher z. Aims. We present an extensive, systematic, and multiband search and analysis of the starburst galaxies at redshift (0 1010. We classify galaxies into three main types, depending on their HST morphology: single knot (Sknot), single star-forming knot plus diffuse light (Sknot+diffuse), and multiple star-forming knots (Mknots/clumpy) galaxy. We found a fraction of Mknots/clumpy galaxy fclumpy = 0.24 considering out total sample of starburst galaxies up to z ∼ 0.5. The individual star-forming knots in our sample follows the same L(Hα) vs. size scaling relation as local giant HII regions. However, they slightly differ from the one provided using samples at high redshift. This result highlights the importance of spatially resolving the star-forming regions for this kind of study. Star-forming clumps in the central regions of Mknots galaxies are more massive, and present higher star formation rates, than those in the outskirts. This trend is less clear when we consider either the mass surface density or surface star formation rate. Sknot galaxies do show properties similar to both dwarf elliptical and irregulars in the surface brightness (μ) versus Mhost diagram in the B-band, and to spheroidals and ellipticals in the μ versus Mhost diagram in the V-band. Conclusions. The properties of our star-forming knots in Sknot+diffuse and Mknots/clumpy galaxies support the predictions of recent numerical simulations claiming that they have been produced by violent disk instabilities. We suggest that the evolution of these knots means that large and massive clumps at the galaxy centers represent the end product of the coalescence of surviving smaller clumps from the outskirts. Our results support this mechanism and make it unlikely that mergers are the reason behind the observed starburst knots. Sknot galaxies might be transitional phases of the Blue Compact Dwarfs (BCD) class, with their properties consistent with spheroidal-like, but blue structures.Publisher PDFPeer reviewe