Effect of bars on the galaxy properties

Aims: With the aim of assessing the effects of bars on disc galaxy properties, we present an analysis of different characteristics of spiral galaxies with strong, weak and without bars. Method: We identified barred galaxies from the Sloan Digital Sky Survey. By visual inspection, we classified the face-on spiral galaxies brighter than g<16.5 mag into strong-bar, weak-bar and unbarred. In order to provide an appropiate quantification of the influence of bars on galaxy properties, we also constructed a suitable control sample of unbarred galaxies with similar redshift, magnitude, morphology, bulge sizes, and local density environment distributions to that of barred galaxies. Results: We found 522 strong-barred and 770 weak-barred galaxies, representing a 25.82% of the full sample of spiral galaxies, in good agreement with previous studies. We also found that strong-barred galaxies show less efficient star formation activity and older stellar populations compared to weak-barred and unbarred spirals from the control sample. In addition, there is a significant excess of strong barred galaxies with red colors. The color-color and color-magnitude diagrams show that unbarred and weak-barred galaxies are more extended towards the blue zone, while strong-barred objects are mostly grouped in the red region. Strong-barred galaxies present an important excess of high metallicity values, compared to the other types, showing similar 12+log(O/H) distributions. Regarding the mass-metallicity relation, we found that weak-barred and unbarred galaxies are fitted by similar curves, while strong-barred ones show a curve which falls abruptly, with more significance in the range of low stellar masses (log[Mstar/Msun] < 10.0). These results would indicate that prominent bars produced an accelerating effect on the gas processing, reflected in the significant changes in the physical properties of their host

AGN spiral galaxies in groups: effects of bars

We explore properties of barred active spiral galaxies in groups selected from the SDSS-DR7, with the aim of assessing the effects of bars on AGN and the role of the high density environment. We identified barred active galaxies that reside in groups from SDSS-DR7 group catalog. To provide a suitable quantification of the effects of bars, a reliable control sample of unbarred active galaxies in high density environments with similar redshift, magnitude, morphology, and bulge size distributions was constructed. We found that the fraction of barred AGN galaxies in groups (~ 38 %) is higher than those in the total barred AGN sample ( ~ 28 %), indicating that AGN spiral galaxies in groups are more likely to be barred than those in the field. We also found that barred AGN galaxies are more concentrated towards the group centers than the other unbarred AGN group members. In addition, barred AGN host galaxies show an excess of population dominated by red colors suggesting that bars produce an importanteffect on galaxy colors of AGN hosts. The host groups of the barred AGN exhibit a larger fraction of red colors than the host groups of the corresponding unbarred active galaxies. Color-magnitude relations of both host groups of AGN differ significantly: the host group colors of barred active galaxies display distributions spreading toward red populations, with respect to the host groups of the unbarred AGN objects. Barred active galaxies show an excess of nuclear activity compared to galaxies without bars. We found that barred active galaxies located farther from the group-center have stronger Lum[OIII]. Our findings suggest that the efficiency of bars to transport material towards the more central regions of the AGN galaxies in high density environments reveals an important dependence on the localization of objects within the group and on the host group colors.Comment: 10 pages, 10 figures. Accepted for Astronomy & Astrophysic

AGN spiral galaxies in groups: effects of bars

AIMS: We explore properties of barred active spiral galaxies in groups and clusters selected from the Sloan Digital Sky Survey data release 7 (SDSS-DR7), with the aim of assessing the effects of bars on active galactic nuclei (AGN) and the role of the high density environment. METHODS: We identified barred active galaxies that reside in groups and clusters by cross-correlating the total barred AGN sample with the SDSS-DR7 group catalog. With the goal of providing a suitable quantification of the effects of bars, a reliable control sample of unbarred active galaxies in high density environments with similar redshift, magnitude, morphology, and bulge size distributions was also constructed. RESULTS: We found that the fraction of barred AGN galaxies in groups and clusters (≈38%) is higher than those in the total barred AGN sample (≈28%), indicating that AGN spiral galaxies in groups are more likely to be barred than those in the field. We also found that barred AGN galaxies are more concentrated towards the group centers than the other unbarred AGN group members. In addition, barred AGN host galaxies show an excess of population dominated by red colors, with respect to the control sample, suggesting that bars produce an important effect on galaxy colors of AGN hosts. The groups of AGN galaxies with and without bars show similar virial masses; however, the host groups of the barred AGN exhibit a larger fraction of red colors than the host groups of the corresponding unbarred active galaxies in the control sample. Color-magnitude relations of both host groups of AGN differ significantly: the host group colors of barred active galaxies display distributions spreading toward red populations, at the same (Mr)Group, with respect to the host groups of the unbarred AGN objects. This trend is more significant in less massive groups than in groups with MVirial> 1013.5M⊙. Barred active galaxies show an excess of nuclear activity compared to galaxies without bars in the control sample. We found that barred active galaxies located farther from the group-center have stronger Lum[OIII], while the nuclear activity in AGN galaxies without bars remain approximately constant with the group-centric distance. In addition, for both AGN samples, nuclear activity increases in bluer host groups however, barred active objects systematically show higher Lum[OIII] values, irrespective of the global group colors. Our findings suggest that the efficiency of bars to transport material towards the more central regions of the AGN galaxies in high density environments reveals an important dependence on the localization of objects within the group/cluster and on the host group colors.Fil: Alonso Giraldes, Maria Sol. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Coldwell Lloveras, Georgina Vanesa. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garcia Lambas, Diego Rodolfo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; Argentin

The Tully-Fisher Relation of Barred Galaxies

We present new data exploring the scaling relations, such as the Tully-Fisher relation (TFR), of bright barred and unbarred galaxies. A primary motivation for this study is to establish whether barredness correlates with, and is a consequence of, virial properties of galaxies. Various lines of evidence suggest that dark matter is dominant in disks of bright unbarred galaxies at 2.2 disk scale lengths, the point of peak rotation for a pure exponential disk. We test the hypothesis that the TF plane of barred high surface brightness galaxies is offset from the mean TFR of unbarred galaxies, as might be expected if barred galaxies are ``maximal'' in their inner parts. We use existing and new TF data to search for basic structural differences between barred and unbarred galaxies. Our new data consist of 2-dimensional Halpha velocity fields derived from SparsePak integral field spectroscopy (IFS) and V,I-band CCD images collected at the WIYN Observatory for 14 strongly barred galaxies. We use WIYN/SparsePak (2-D) velocity fields to show that long-slit (1-D) spectra yield reliable circular speed measurements at or beyond 2.2 disk scale lengths, far from any influence of the bar. This enables us to consider line width measurements from extensive TF surveys which include barred and nonbarred disks and derive detailed scaling relation comparisons. We find that for a given luminosity, barred and unbarred galaxies have comparable structural and dynamical parameters, such as peak velocities, scale lengths, or colors. In particular, the location of a galaxy in the TF plane is independent of barredness. In a global dynamical sense, barred and unbarred galaxies behave similarly and are likely to have, on average, comparable fractions of luminous and dark matter at a given radius. (abridged)Comment: Accepted for publication in the ApJ (September 1, 2003 issue, v594). Appendix figures with I-band image and superimposed 2-D velocity field plus rotation curves must be downloaded separately (due to size constraints) from http://www.astro.ubc.ca/people/courteau/public/courteau03_TFbars.ps.g

The imprints of bars on the vertical stellar population gradients of galactic bulges

This is the second paper of a series aimed to study the stellar kinematics and population properties of bulges in highly-inclined barred galaxies. In this work, we carry out a detailed analysis of the stellar age, metallicity and [Mg/Fe] of 28 highly-inclined ($i > 65^{o}$) disc galaxies, from S0 to S(B)c, observed with the SAURON integral-field spectrograph. The sample is divided into two clean samples of barred and unbarred galaxies, on the basis of the correlation between the stellar velocity and h$_3$ profiles, as well as the level of cylindrical rotation within the bulge region. We find that while the mean stellar age, metallicity and [Mg/Fe] in the bulges of barred and unbarred galaxies are not statistically distinct, the [Mg/Fe] gradients along the minor axis (away from the disc) of barred galaxies are significantly different than those without bars. For barred galaxies, stars that are vertically further away from the midplane are in general more [Mg/Fe]--enhanced and thus the vertical gradients in [Mg/Fe] for barred galaxies are mostly positive, while for unbarred bulges the [Mg/Fe] profiles are typically negative or flat. This result, together with the old populations observed in the barred sample, indicates that bars are long-lasting structures, and therefore are not easily destroyed. The marked [Mg/Fe] differences with the bulges of unbarred galaxies indicate that different formation/evolution scenarios are required to explain their build-up, and emphasizes the role of bars in redistributing stellar material in the bulge dominated regions.Comment: 22 pages, 7 main body figures +8 appendix figures, 2 tables. Accepted by MNRA

Galaxy Zoo: The Environmental Dependence of Bars and Bulges in Disc Galaxies

We present an analysis of the environmental dependence of bars and bulges in disc galaxies, using a volume-limited catalogue of 15810 galaxies at z<0.06 from the Sloan Digital Sky Survey with visual morphologies from the Galaxy Zoo 2 project. We find that the likelihood of having a bar, or bulge, in disc galaxies increases when the galaxies have redder (optical) colours and larger stellar masses, and observe a transition in the bar and bulge likelihoods, such that massive disc galaxies are more likely to host bars and bulges. We use galaxy clustering methods to demonstrate statistically significant environmental correlations of barred, and bulge-dominated, galaxies, from projected separations of 150 kpc/h to 3 Mpc/h. These environmental correlations appear to be independent of each other: i.e., bulge-dominated disc galaxies exhibit a significant bar-environment correlation, and barred disc galaxies show a bulge-environment correlation. We demonstrate that approximately half (50 +/- 10%) of the bar-environment correlation can be explained by the fact that more massive dark matter haloes host redder disc galaxies, which are then more likely to have bars. Likewise, we show that the environmental dependence of stellar mass can only explain a small fraction (25 +/- 10%) of the bar-environment correlation. Therefore, a significant fraction of our observed environmental dependence of barred galaxies is not due to colour or stellar mass dependences, and hence could be due to another galaxy property. Finally, by analyzing the projected clustering of barred and unbarred disc galaxies with halo occupation models, we argue that barred galaxies are in slightly higher-mass haloes than unbarred ones, and some of them (approximately 25%) are satellite galaxies in groups. We also discuss implications about the effects of minor mergers and interactions on bar formation.Comment: 20 pages, 18 figures; references updated; published in MNRA