Found 20 talks width keyword early-type galaxies
I present a detailed analysis of the scaling relations of ETGs and suggest a way to predict the evolution of the distributions of galaxies in these planes. This new approach is able to account of several features observed in the FP projections and of the tilt of the Fundamental Plane.
In the local universe most of the stellar mass is in passive galaxies, where star formation is
absent or at very low levels. Understanding what are the mechanisms that have been
responsible for quenching star formation in galaxies, and transforming them into passive,
quiescent systems, is one of the main observational and theoretical challenges of extragalactic
astrophysics. I will give a brief overview of the several possible quenching causes and physical
processes that have been proposed so far, ranging from feedback from black hole accretion and
starburst activity, to effects associated with the large scale environment in which galaxies live.
Although most of these mechanisms and causes play a role in different classes of galaxies and
at different epochs, multi-band observations are providing growing evidences that just a few of
them play the key, dominant role.
I will conclude by providing prospects for further investigating these aspects and tackling open
questions with the next generation of observing facilities.
It has been claimed for decades that almost all galaxies in the local Universe host at their centre a supermassive black hole (SMBH) the mass of which appears to be tightly correlated with the stellar mass and the random motion ("velocity dispersion", sigma) of the stars in the host galaxy. In this talk I will first review the state of the art in this field. I will then highlight that significant biases affect local black hole-galaxy correlations. I will specifically show that the majority of quiescent early-type galaxies with central black hole dynamical mass estimates have significantly higher velocity dispersions than local typical galaxies of similar stellar mass. Through aimed Monte Carlo simulations, residual analysis, and the comparison with latest AGN clustering measurements, I will then illustrate that present data sets of active and quiescent galaxies strongly favour on average lower SMBH masses than previously thought, and point to velocity dispersion as more ``fundamental'' than galaxy stellar mass, galaxy size or Sérsic index. I will then move on discussing the main implications of these findings, in particular: 1) The implied black hole radiative efficiencies and obscured fractions; 2) the consequences on feedback from active black holes and SMBH binary gravitational waves; 3) the connection to cosmological models that rely on velocity dispersion, rather than stellar mass, as main driver of black hole growth.
Zoom link: https://rediris.zoom.us/j/97154760685
Stellar populations vary across the galaxy population. However, even within a single galaxy, there are stellar population gradients which spatially resolved spectroscopic studies are beginning to reveal. The MaNGA survey permits a study of gradients in a sample of early-type galaxies which is nearly two orders of magnitude larger than previous work. This allows us to quantify the effects of gradients on estimates of the stellar and dynamical masses of these galaxies, and to study how age and abundance gradients, and thus star formation and assembly histories, vary across the population. In this talk I will present results from our recent analysis.
zoom link: https://rediris.zoom.us/j/97614680345
Using deep photometry SBFs have been traditionally used to determine galaxy distances. We have recentlycomputed SBF spectra of stellar populations at moderately high resolution,which are fully based on empirical stellar spectral libraries. We show that the SBF spectraprovide new means to perform the stellar population studies, which, so far, have been tackled on the basis of the mean properties. We find that theSBFs are able to unveil very metal-poor components at the one percent level, which are not possible to disentangle with the standard analysis. In massive Early-Type Galaxies suchmetal-poor components correspond to the first stages in their chemicalenrichment and, therefore, the SBFs provide stringent constrains on their formation.
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.
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.
The ALHAMBRA (Advance Large Homogeneous Area Medium Band Redshift Astronomical; Moles et al. 2008) survey has observed 8 different regions of the sky, including sections of the COSMOS, DEEP2, ELAIS, GOODS-N, SDSS and Groth fields using a new photometric system with 20 contiguous, ~300A width, filters covering the optical range, plus deep JHKs imaging. The observations, carried out with the Calar Alto 3.5m telescope using the wide field (0.25 deg2 FOV) optical camera LAICA and the NIR instrument Omega-2000, correspond to ~700hrs of on-target science images. The photometric system was specifically designed to maximize the effective depth of the survey in terms of accurate spectral-type and photometric redshift estimation along with the capability of identification of relatively faint emission lines.
The ALHAMBRA Gold catalogue corresponds to a subsample of ~100k bright galaxies (+20.000 stars in the galactic halo and ~1000 AGN candidates), photometrically complete down to magnitude I=23AB, with very accurate and reliable photometric redshift estimations.
Considering that the Spanish community will have privileged access to the data until Nov15th 2013, this seminar is intended to be a brief introduction to the potential (doable) science with the ALHAMBRA-survey.
Massive early-type galaxies constitute an ideal test bed to probe our understanding of galaxy formation and evolution. Their high mass, spheroidal morphology and overly old stellar populations, along with their presence over a wide range of redshifts put to the test our current paradigm of formation via hierarchical growth. In this talk I will review recent work focused on the dark and bright sides of this problem. The former is tackled via gravitational lensing, comparing the dark matter and luminous components out to several effective radii, probing the efficiency of baryon collapse and ejection, and its feedback on the dark matter distribution (adiabatic compression). The bright side of early-type galaxies is approached via photo-spectroscopic analyses of the stellar populations, revealing a complex formation and assembly history with two well-defined phases of growth, and an intriguing connection with the "microphysics" of star formation.
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- TBDThursday December 14, 2023 - 10:30 GMT (Aula)
- GESCOPThursday January 18, 2024 - 10:30 GMT (Aula)