Found 16 talks width keyword galactic bars

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Friday May 26, 2023
Universidad Nacional Autonoma de Mexico

Abstract

We present the extended data release of the Calar Alto Legacy Integral Field Area (CALIFA) survey (eDR). It comprises science-grade quality data for 895 galaxies obtained with the PMAS/PPak instrument at the 3.5 m telescope at the Calar Alto Observatory along the last 12 years, using the V500 setup (3700-7500Å, 6Å/FWHM) and the CALIFA observing strategy. It includes galaxies of any morphological type, star-formation stage, a wide range of stellar masses ( ∼10^7-10^12 Msun), at an average redshift of  ∼0.015 (90\% within 0.005 < z <0.05). Primarily selected based on the projected size and apparent magnitude, we demonstrate that it can be volume corrected resulting in a statistically limited but representative sample of the population of galaxies in the nearby Universe. All the data were homogeneously re-reduced, introducing a set of modifications to the previous reduction. The most relevant is the development and implementation of a new cube-reconstruction algorithm that provides an (almost) seeing-limited spatial resolution (FWHM PSF  ∼1.0").  Furthermore we present the analysis performed using the pyPipe3D pipeline for these dataset. We include a description of (i) the analysis performed by the pipeline, (ii) the adopted datamodel for the derived spatially resolved properties and (iii) the catalog of integrated, characteristics and slope of the radial gradients for a set of observational and physical parameters derived for each galaxy. All these data has been distributed through the following webpage: http://ifs.astroscu.unam.mx/CALIFA_WEB/public_html/


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Thursday December 1, 2022
Universidad de Atacama

Abstract

Bars are prominent features observed in most disc galaxies, having a crucial

role in the secular evolution of their hosts. Indeed, they redistribute material
within the galaxies, while rotating around the centre at a given angular frequency,
the bar pattern speed.
When formed in an isolated galaxy, a bar is expected to be born as fast rotating
with a bar rotation rate R (a parameter used to describe the bar pattern speed)
equal to 1.0 ≤ R ≤ 1.4. During its evolution, the bar can be slowed through the
exchange of angular momentum with the other components and/or when an efficient
dynamical friction is exerted by the dark matter (DM) halo. In this case, R is
shifted in the slow regime (R > 1.4), while the bar radius and strength are increasing.
On the other hand, ultrafast (UF) bars, with R < 1.0, are physically unstable.
Measuring the bar rotation rate becomes desirable both to investigate the secular
evolution of barred galaxies and to test whether the measured DM distribution matches
that predicted by cosmological simulations in the cold DM framework.
The only model-independent way to recover the bar pattern speed (and derive R) is
the Tremaine-Weinberg (TW) method, nowadays largely applied thanks to the advent
of integral-field spectroscopy: most of the analysed bars are compatible with the
fast regime, while a non-negligible fraction belongs to the unstable UF regime.
As a consequence, the question arises whether these results are biased by an
improper application of the method or instead they come from a not completely
theoretically understanding of the nature of slow/UF bars.
We explore the open questions on bar pattern speed with the TW method by
1. testing the reliability of the TW measurements which led to UF bars
2. pushing further the quest of slow bars applying the TW method to a sample of
dwarf galaxies, the best candidates to host slowly-rotating bars, since they are
commonly thought to host a massive and centrally-concentrated DM halo.
We measure the bar radius from the analysis of the maps tracing the transverse-to-radial
force ratio, showing that UF bars are no longer observed when the correct measurement
of the bar radius is adopted to derive R.
We apply the TW method to dedicated MUSE observations of a sample of 5 dwarf barred
galaxies from the Virgo cluster, showing that the analysed bars are slowly-rotating. This
suggests they could have been slowed down by a dense and massive DM halo.
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Zoom

https://rediris.zoom.us/j/88520341620?pwd=RldDYzFzeU8zYzlOckozbjloUmEwZz09

Meeting ID: 885 2034 1620     
Passcode: 818629

 

YouTube: https://youtu.be/8yLu_LHWuxc


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Thursday May 23, 2019
Universidad Autónoma de Madrid

Abstract

The Time Inference with MUSE in Extragalactic Rings, TIMER, is a project dedicated to study the central regions
of 24 nearby galaxies with the integral field spectrograph MUSE. The spatial resolution of this instruments
allows the detailed study of the different structural components in these galaxies and, therefore, disentangle
their star formation histories, kinematics and dynamics of both, the gaseous and the stellar constituents.
In this talk, I will give an overview of the project as well as some details on  how the  dataset can be used for a plethora of scientific applications, like
understanding the stellar and AGN feedback, the role of primary and secondary bars, the dynamics of nuclear
spiral arms, barlenses, box/peanuts and bulges.


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Thursday May 22, 2014
IAA

Abstract

Different components of galaxies are the result of internal and environmental processes during their lifetimes. Disentangling these processes is an important issue for understanding how galaxies form and evolve. In this context isolated galaxies provide a fruitful sample for exploring galaxies which have evolved mainly by internal processes (minimal merger/accretion/tidal effects). I will present the structural analysis performed as part of the AMIGA (Analysis of the interstellar Medium of Isolated GAlaxies; http://www.amiga.iaa.es) project. The analysis of the stellar mass-size relation of our spiral galaxies reveals a larger size for disks in low-density environments, as well as a dependence of disk size on the number of satellites. A 2D bulge/disk/bar decomposition of SDSS i-band images was performed in order to identify the pseudobulges in our sample. We derived (g-i) bulge colors and find a large fraction of pseudobulges in the red sequence of early-type galaxies. The bluer pseudobulges in our sample tend to be located in those galaxies more affected by tidal interactions. The properties of the majority of bulges in isolated galaxies suggest that pseudobulges formed most of their mass at an early epoch, and that specific environmental events may rejuvenate pseudobulges.


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Wednesday February 12, 2014
University of Oulu (Finland)

Abstract

The ΛCDM model predicts that galaxies originate in dark matter haloes, undergoing in their early age a process of continuous merges with other galaxies that determines the first part of their evolution. The frequency of these events decreases with time and their gradual change turns to be internally driven, becoming much slower. Bars, elongated stellar structures in the central regions of galaxies, are known to play an active role in this phase of their evolution, so-called secular.

Bars are fundamentally responsible for the redistribution of matter and the angular momentum of the baryonic and dark matter components of disc galaxies. Different simulations predict that bars get stronger and longer in time, slowing down their rotation speed.

Based on the Spitzer Survey of Stellar Structure in Galaxies (S4G) 3.6 μm imaging, we aim to study the secular evolution of disc galaxies by focusing on their stellar bar parameters. We take a large well-defined sample of about 650 nearby barred galaxies and we infer the gravitational potential from 3.6 μm images. We calculate gravitational torques, the ratio of the maximal tangential force to the mean axisymmetric radial force, in order to obtain a quantitative measure of the bar-induced perturbation strengths. In addition, we estimate the bar strength from the m=2 normalized Fourier density amplitudes and determine bar lengths both visually and by using an ellipse fitting method. Bar morphology and the interplay with spiral arms are studied via image-stacking methods as well.

In this talk I will present the statistical results derived from our measurements, providing observational evidence for the evolution of bars in accordance with the current theoretical predictions. We study bar parameters as a function of the Hubble type, addressing how the different measurements of the bar strength correlate with each other and with the galactic mass. The quality of our data allows us to probe the properties of bars in the Local Universe and connect them to the evolution of other galactic structures.


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Thursday May 23, 2013
University of St Andrews

Abstract

The general picture of galaxy formation and evolution includes bars as the main drivers of the internal secular processes affecting the lifetime of disc galaxies. Bars are present in a very high fraction of all the spiral galaxies found at different redshifts, and the processes inducing their formation or the effects they may have on their host galaxies are still under discussion. Particularly interesting is the case of double-barred galaxies: at least 20% of all spirals have turned out to host not only one but two bars embedded in them. These two bars appear randomly oriented and independently rotating. The formation of such a double-barred system has been the goal of several numerical simulations and the results obtained so far can be roughly divided in two big groups: gas-rich and gas-free formation scenarios. In the same way a single bar does, double-bar systems might also promote gas inflow and contribute to the internal secular evolution. Moreover, they have also been proposed as a very efficient mechanism for the feeding of the active galactic nuclei.

All the previous theoretical hypothesis on the formation and evolution of double-barred galaxies have not been tested due to the lack of observational works focused on these systems. With this motivation, during my PhD I observed a sample of double-barred galaxies in order to fully analyse their kinematics and stellar populations. Among the most interesting results, it is important to highlight the discovery of the sigma-hollows, which are the only known kinematical signature of the presence of inner bars, or the fact that inner bars are younger and more metal-rich than their surrounding regions. In this talk I will present the whole work and discuss the results in the framework of the different formation scenarios and the role that these inner bars may be playing in the evolution of their host galaxies.


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Thursday May 9, 2013
Max-Planck-Institute for Extraterrestrial Physics

Abstract

Among the different effects of secular evolution of galaxies we find how bars influence enormously their host galaxies. For many years now, it is known how the evolution of bars will produce different boxy/peanut and X-shape bulges. In this context our Milky Way is an example of a boxy bulge, and we will present a self consistent N-body simulation of a barred galaxy that will be compared with some of the Milky Way available data. We will compare the model in terms of morphology and structure, kinematics and finally metallicity gradients.


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Tuesday January 29, 2013
IAC

Abstract

The effects that environment produce on galaxy disks and how they modify the subsequent formation of bars need to be distinguished to fully understand the relationship between bars and environment. To shed light on this issue, we derive the bar fraction in three different environments ranging from the field to Virgo and Coma Clusters, covering an unprecedentedly large range of galaxy luminosities (or, equivalently, stellar masses). We confirm that the fraction of barred galaxies strongly depends on galaxy luminosity. We also show that the difference between the bar fraction distributions as a function of galaxy luminosity (and mass) in the field and Coma Cluster is statistically significant, with Virgo being an intermediate case. We interpret this result as a variation of the effect of environment on bar formation depending on galaxy luminosity. We speculate that brighter disk galaxies are stable enough against interactions to keep their cold structure, thus, the interactions are able to trigger bar formation. For fainter galaxies, the interactions become strong enough to heat up the disks inhibiting bar formation and even destroying the disks. Finally, we point out that the controversy regarding whether the bar fraction depends on environment could be resolved by taking into account the different luminosity ranges probed by the galaxy samples studied so far.


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Tuesday May 15, 2012
European Southern Observatory

Abstract

I will address the effects of bar-driven secular evolution in discs by comparing their properties in a sample of nearly 700 barred and unbarred massive galaxies. Through detailed structural decompositions I will show that, as a population, barred discs tend to have fainter central surface brightness and larger disc scale lengths than those of unbarred galaxies. Bars rarely occur in high-surface brightness discs and tend to reside in moderately blue discs. These results show that bars induce noticeable evolution in the structural properties of galaxy discs, in qualitative agreement with longstanding theoretical expectations.


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Thursday April 19, 2012
Universidad de Alicante, Spain

Abstract

Abstract: The study of the structure of our Galaxy, particularly its inner disc, has always been hindered by two factors: interstellar extinction dims even the brightest stars at optical wavelengths and the high source density prevents us, as the proverbial trees, to see the big galactic picture. 

With this talk we give a broad introduction of the historical efforts to alleviate these issues in the neverending quest to dig deeper into the Milky Way, followed by a overview of the first results obtained by the VVV-Vista survey, that maps the southern Galactic sky with unprecedent depth and resolution.

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    Prof. Kentaro Nagamine
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