Found 16 talks width keyword galactic bars

With the discovery of several massive, young clusters in the last five years, the area around the base of the Scutum-Crux arm (around l=28) has become one of the more intense stellar formation areas in the whole Galaxy. This is not totally unexpected, as it is just there where it was predicted that the long bar of the Milky Way would come into contact with the disk, triggering stellar formation. With this talk we review all these evidences and we bring others into light, as we try to obtain a clearer picture of what is happening in these areas and what does it tell us about the inner structure of the Galaxy, particularly of the bulge+bar complex.

(1) In this talk I will present a recent study of the bar fraction in the Coma Cluster galaxies based on a sample of 190 galaxies selected from the Sloan Digital Sky Survey Data Release 6 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 < Mr < -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 < Mr < -17) and masses (10⁹ < M/M? < 10¹¹). This result holds when compared with a sample of bright/massive field galaxies. 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. We discuss the implications of our results for the formation and evolution scenarios of bars and disks.

(2) The Herschel Space Observatory was launched on 14 May 2009. After a short commissioning and performance verification period, the science demonstration observations started in September 2009. Herschel is carrying out now routine science observations. The three instruments (SPIRE, PACS and HIFI) are working extremely well. The first results of the many Herschel Key Projects were presented at the ESLAB 2010 conference in ESTEC on May 4-7 2010 and will be published in a special issue of Astronomy and Astrophysics. In this talk I will introduce the observing capabilities of Herschel and will review some of the first results in extragalactic astronomy and in particular those of the Herschel Multi-tiered Extragalactic Survey (HerMES).

We test the theoretical prediction that the straightest dust lanes in bars are found in strongly barred galaxies, or more specifically, that the degree of curvature of the dust lanes is inversely proportional to the strength of the bar. The test uses archival images of barred galaxies for which a reliable non-axisymmetric torque parameter (Q_b) and the radius at which Q_b has been measured (r(Q_b)) have been published in the literature. Our results confirm the theoretical prediction but show a large spread that cannot be accounted for by measurement errors. We simulate 238 galaxies with different bar and bulge parameters in order to investigate the origin of the spread in the dust lane curvature versus Q_b relation. From these simulations, we conclude that the spread is greatly reduced when describing the bar strength as a linear combination of the bar parameters Q_b and the quotient of the major and minor axes of the bar, a/b. Thus, we conclude that the dust lane curvature is predominantly determined by the parameters of the bar.

I will propose a new theory to explain the formation and properties of rings and spirals in barred galaxies, focusing on a comparison of theoretical results to observations and giving some predictions for further comparisons. This theory can account for both spirals and rings, the latter both inner and outer. The model outer rings have the observed R₁, _{R_1'}, _{R_2}, _{R_2'} and _{R_1R_2} morphologies, including the dimples near the direction of the bar major axis. It explains why the vast majority of spirals in barred galaxies are two armed and trailing and I will discuss what it takes for higher multiplicity arms to form. The shapes of observed and theoretical spirals agree and the theory predicts that stronger non-axisymmetric forcings at and somewhat beyond corotation will drive more open spirals. I will compare the ratio of ring diameters in theory and in observations and predict that more elliptical rings will correspond to stronger forcings. This theory also provides the right building blocks for the rectangular-like bar outline and for ansae.