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We compute the chemical evolution of the Galactic bulge to explain the existence of two main stellar populations recently observed. After comparing model results and observational data we suggest that the old more metal poor stellar…

Astrophysics of Galaxies · Physics 2015-06-11 V. Grieco , F. Matteucci , A. Pipino , G. Cescutti

We compare the stellar population properties in the central regions of visually classified non-starforming spiral and elliptical galaxies from Galaxy Zoo and SDSS DR7. The galaxies lie in the redshift range $0.04<z<0.1$ and have stellar…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 Aday R. Robaina , Ben Hoyle , Anna Gallazzi , Raul Jimenez , Arjen van der Wel , Licia Verde

We discuss the formation and evolution of boxy/peanut bulges (B/Ps) and present new simulations results. Orbital structure studies show that B/Ps are parts of bars seen edge-on, they have their origin in vertical instabilities of the disc…

Astrophysics · Physics 2015-05-13 E. Athanassoula , I. Martinez-Valpuesta

We have obtained long-slit spectroscopy for a sample of 20 early-type barred galaxies to study the influence of bars in the building of galaxy bulges. Line strength indices were measured and used to derive age and metallicity gradients in…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 Isabel Perez , Patricia Sanchez-Blazquez

Boxy/peanut bulges are considered to be part of the same stellar structure as bars and both could be linked through the buckling instability. The Milky Way is our closest example. The goal of this letter is determining if the mass assembly…

We have conducted a spectroscopic analysis of the bulges of a sample of 31 spiral galaxies, spanning the Hubble sequence from S0 to Scd type, in order to study the radial distribution of their stellar population properties.

Astrophysics · Physics 2009-11-07 P. Jablonka , J. Gorgas , P. Goudfrooij

We explore trends in the morphology and line-of-sight (los) velocity of stellar populations in the inner regions of disc galaxies, using N-body simulations with both a thin (kinematically cold) and a thick (kinematically hot) disc which…

Astrophysics of Galaxies · Physics 2017-10-11 F. Fragkoudi , P. Di Matteo , M. Haywood , A. Gómez , F. Combes , D. Katz , B. Semelin

After presenting three ways of defining a bulge component in disc galaxies, we introduce the various types of bulges, namely the classical bulges, the boxy/peanut bulges and the disc-like bulges. We then discuss three specific topics linked…

Astrophysics · Physics 2007-10-09 E. Athanassoula , I. Martinez-Valpuesta

We use stellar dynamical bulge/disk/halo simulations to study whether barlenses (lens-like structures embedded in the narrow bar component) are just the face-on counterparts of Boxy/Peanut/X-shapes (B/P/X) seen in edge-on bars, or if some…

Astrophysics of Galaxies · Physics 2017-02-08 Heikki Salo , Eija Laurikainen

The radial profiles of the Hb, Mg, and Fe line-strength indices are presented for a sample of eight spiral galaxies with a low surface-brightness stellar disc and a bulge. The correlations between the central values of the line-strength…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 L. Morelli , E. M. Corsini , A. Pizzella , E. Dalla Bontà , L. Coccato , J. Méndez-Abreu , M. Cesetti

Numerical simulations of double-barred galaxies predict the build-up of different structural components (e.g., bulges, inner discs) in the central regions of disc galaxies. In those simulations, inner bars have a prominent role in the…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 A. de Lorenzo-Cáceres , J. Falcón-Barroso , A. Vazdekis

We present a systematic observational study of the relationship between bars and boxy/peanut-shaped (B/PS) bulges. We first review and discuss proposed mechanisms for their formation, focussing on accretion and bar-buckling scenarios. Using…

Astrophysics · Physics 2009-10-31 M. Bureau , K. C. Freeman

Barred galaxies have interesting morphological features whose presence and properties set constraints on galactic evolution. Here we examine barlenses, i.e. lens-like components whose extent along the bar major axis is shorter than that of…

Astrophysics of Galaxies · Physics 2016-03-01 E. Athanassoula , E. Laurikainen , H. Salo , A. Bosma

Observational and theoretical evidence that internal, slow ("secular") evolution reshapes galaxy disks is reviewed in Kormendy & Kennicutt (2004, ARAA, 42, 603). This update has three aims. First, I emphasize that this evolution is very…

Astrophysics · Physics 2009-11-13 John Kormendy

The vertical profiles of disc galaxies are built by the material trapped around stable periodic orbits, which form their "skeletons". According to this, the knowledge of the stability of the main families of periodic orbits in appropriate…

Astrophysics · Physics 2009-11-11 P. A. Patsis , E. M. Xilouris

We seek to understand whether the stellar populations of galactic bulges show fingerprints of secular evolution triggered by the presence of the disc. For this purpose we re-analyse the sample of Proctor and Sansom, deriving stellar…

Astrophysics · Physics 2009-11-13 Daniel Thomas , Roger L. Davies

Selecting centrally quiescent galaxies from the Sloan Digital Sky Survey (SDSS) to create high signal-to-noise (>100) stacked spectra with minimal emission line contamination, we accurately and precisely model the central stellar…

We have obtained 2D spectral data for a sample of 58 nearby S0 galaxies with the Multi-Pupil Spectrograph of the 6m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The Lick indices H-beta, Mgb, and…

Astrophysics · Physics 2009-11-13 Olga K. Sil'chenko

We present a study of the broadband UBV color profiles for 257 Sbc barred and non-barred galaxies. In our sample, the color gradients are negative (reddish inward) in approximately 59% of the objects, are almost null in 27%, and are…

Astrophysics · Physics 2009-11-06 Dimitri Alexei Gadotti , Sandra dos Anjos

Recent ground-based photometric investigations suggest that central regions of late-type spirals are closely coupled to the inner disk and probably formed via secular evolution. Evidence presented in support of this model includes the…

Astrophysics · Physics 2016-01-27 Stephane Courteau