Found 89 talks width keyword galaxy evolution

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Thursday November 23, 2023
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Oort Fellow and IAU Gruber Foundation Fellow, Leiden Observatory, Leiden University, The Netherlands

Abstract

From the time the first stars formed to the present-day, metals have witnessed the assembly of structure in the Universe in great detail. Although metals only form in stars and stellar remnants, they are ubiquitously present everywhere. However, we still do not understand how metals are effectively dispersed throughout the Universe, and the various roles they play in shaping galaxies. In this talk, I will present a multi scale approach to study the role of metals in galaxy evolution, from molecular clouds to galactic discs. On smaller scales, I will focus on physical processes that shape up the initial mass function (IMF, with a particular emphasis on metal-free and metal-poor environments) that directly set the integrated yield of metals in the first and early galaxies. I will discuss results from high resolution radiation chemo-magnetohydrodynamic simulations that study the impact of turbulence, radiation feedback and magnetic fields on the primordial IMF, and describe analytical models of dusty molecular clouds that explain the transition in the IMF as the metal abundance grows over cosmic time. On larger scales, the talk will cover the physics of gas-phase metal distribution in galaxies. Using a combination of spatially-resolved gas-phase metallicity measurements and novel semi-analytical models, I will present recent results that advance our understanding of metallicity gradients in (late type) galaxies. In particular, I will show how self-consistently incorporating metal dynamics into galaxy evolution models is key to explaining the observed trends in metallicity gradients with galaxy mass, metallicity, and kinematics. I will end by highlighting how ongoing/upcoming astronomical facilities will transform our understanding of metal evolution in galaxies.


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Friday May 26, 2023
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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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Tuesday April 18, 2023
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University of Oxford

Abstract

 

Nowadays, it is widely accepted that most galaxies undergo an active phase in their evolution. The impact of the energy released by active galactic nuclei (AGN) in the interstellar medium (ISM) of the host galaxy has been proposed as a key mechanism responsible for regulating star formation (SF). The mid-infrared (IR) is the ideal spectral range to investigate the nuclear/circumnuclear regions of AGN since dust extinction is significantly lower compared to the visible range. Furthermore, it provides unique tracers to study the AGN-SF connection such as H2 rotational lines, fine structure lines and Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are also a powerful tool to characterize the ISM in different environments.

Recently, we presented new JWST/MIRI MRS spectroscopy of three Seyfert AGN in which we compare their nuclear PAH emission with that of star-forming regions. This study represents the first of its kind to use sub-arcsecond angular resolution data of local luminous Seyferts (Lbol > 10^44.5 erg/s) with a wide wavelength coverage (4.9-28.1 μm). Our results showed that a suite of PAH features is present in the innermost parts of these Seyfert galaxies. We found that the nuclear regions of AGN lie at different positions of the PAH diagnostic diagrams, whereas the SF regions are concentrated around the average values of SF galaxies. Furthermore, we find that the nuclear PAH emission mainly originates in neutral PAHs while, in contrast, PAH emission originating in the star forming regions favours small ionised PAH grains. Therefore, our results provide evidence that the AGN have a significant impact on the ionization state and size of the PAH grains on scales of ~142-245 pc. This is fundamental since PAH bands are routinely used to measure star-formation activity in near and far SF and active galaxies.

Finally, I will summarise our ongoing JWST work within the GATOS (Galactic Activity, Torus and Outflow Survey) collaboration. In particular, I will focus on our recent study about the survival of PAH molecules in AGN-driven outflows.


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Tuesday April 11, 2023
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University of Florence and INAF-Arcetri - Italy

Abstract

 

The abundance of chemical elements across cosmic time provide unique information on the physical processes driving the evolution of galaxies. Current methods for measuring gas-phase metallicities, based on either direct measurements of electron temperature (Te) or calibrations from strong nebular emission line ratios, are based on simplifying assumptions and do not adequately describe the complexity of the emitting regions. We present a new approach based on fitting galaxy spectra with multi-cloud photoionisation models. Unlike current methods, based on comparisons with single-cloud models, our methodology is able to reproduce all observed emission lines to a very high accuracy, down to a few percent, thus allowing for accurate metallicity measurements. We further recover the well known trends between ionization parameter and metallicity, and between the Nitrogen and Oxygen abundances. Our models accurately reproduce the auroral-to-nebular line ratios, while the results of the standard Tmethod are sometimes very different from the best-fitting model metallity. We finally present newly calibrated metallicity estimators for galaxies based on ratios between strong emission lines.

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Tuesday March 28, 2023
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University of St. Andrew

Abstract

Galaxies and the dark matter halos in which they reside are intrinsically connected. That relationship holds information about key processes in galaxy and structure formation. In this talk, I will consider how the galaxy-halo connection depends on position within the cosmic web - the familiar decomposition of large-scale structure in filaments, knots and voids. Simulations demonstrate the various ways in which the cosmic web modulates the growth and dynamics of halos. The extent to which the cosmic web impacts on galaxies is more difficult to establish. For example, galaxies might be sensitive only to the evolution of the host halo, in which case any effect of the cosmic web on galaxies is secondary, and can be inferred from the halo's history. There is evidence, however - from simulations and observations - that the cosmic web also impacts on the evolution of galaxies via the effect it has on the broader gas ecosystem in which they are embedded, as well as through "pre-processing" effects on group scale. So, how should we think of the cosmic web in its role as a transformative agent of galaxies? And what physical processes can we convincingly constrain from observations and simulations? In this talk I highlight recent work that addresses these questions.


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Thursday February 23, 2023
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University of Padova

Abstract

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.

 


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Tuesday January 31, 2023
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INAF-Osservatorio Astronomico di Trieste

Abstract

Lithium is a key   element which plays an important role in  astronomy  as well as everyday human life.  Nevertheless it is probably the only element whose astronomical origin is still a mystery.  A fraction of  about 30% of what is measured today was  made in the first 3 minutes of the Universe and about 10% is  made  by spallation  reactions of  cosmic rays with the atoms in the interstellar medium. However, as stars burn  Li in their hot interiors and what makes the remaining ~60%  is still unknown.  The recent detections of   7Li and 7Be in the outburst of   classical novae is a landmark in the solution of this long standing mystery. The discovery   confirms a theoretical speculation  made about 50 years ago    but  which was never  supported by observations.   Since then  the  presence of Be-7 has been confirmed to be ubiquitous in about a dozen classical novae and very recently also in the  recurrent nova RS Oph that blew out in August 2021.  However, the observed values show  tension with theory  being one order of magnitude greater than predictions.  Detailed Li Galactic chemical evolution models   assuming the "observed" yields  show that indeed  Novae could  be the long sought  source for the Galactic  7Li. 


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Thursday December 15, 2022
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Univ. Genève

Abstract

In this talk, I will present recent results on a new sample of extremely UV-luminous star-forming galaxies at z=2-4 discovered within the 9000deg^2-wide Baryon Oscillation Spectroscopic Survey database of the Sloan Digital Sky Survey. These puzzling sources show apparent magnitudes rivaling those of bright QSOs, but without any hint of AGN activity or being magnified by gravitational lensing. Instead, these sources are characterized by very young stellar populations (~ 10 Myr) and compact morphologies. The two highest-redshift sources in our sample show very high Lyman continuum (LyC, with >13.6 eV) escape fractions, up to fesc(LyC)~90%, being the most powerful ionizing sources identified so far among the star-forming galaxy population, both in terms of the intrinsic LyC photon production rate and escape. With SFRs~1000 Msun/yr, but almost un-obscured, and specific star formation sSFR >50-100 Gyr^-1, these sources are very efficient star-forming galaxies, possibly representing a short-lived phase in the evolution of massive and compact galaxies. I will highlight some unique properties observed in these sources including LyC emission, complex Lyman-alpha profiles, strong wind lines, SEDs, among others. Finally, I discuss the properties of these UV-bright sources in the broad context of galaxy formation and evolution, and possible implications to cosmic reionization.


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Tuesday October 4, 2022
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National Centre for Nuclear Research, Warsaw, Poland

Abstract

Vimos Public Extragalactic Redshift Survey (VIPERS) is a spectroscopic survey designed to  investigate the spatial distribution of ~90k galaxies on redshift 0.4<z<1.2. The catalogue of spectroscopic observations, combined with auxiliary photometric data, is perfect for evolutionary studies of different types of galaxies. But also for tracing rare objects. One of them are the so-called “red nuggets”, progenitors of the most massive galaxies in the local Universe.  The discovery of red nuggets - highly massive, passive and extremely compact galaxies  -  at high redshift challenged the leading cosmological models, as they do not fit into the evolutionary paths of passive galaxies. Taking into account  that  the galaxies' mergers are stochastic events, it is possible that some red nuggets  remain relatively unaltered for billions of years. Those survivors constitute a group of unique galaxies in the local Universe,  commonly named “relics”. Despite numerous studies dedicated to red nuggets and relics, the link between the population of compact, massive, passive galaxies in the early Universe and their remnants in the local Universe, is still poorly understood.

In my talk I  will present the first spectroscopically selected catalogue of red nuggets at the intermediate redshift.  It is the most extensive catalogue of this kind of galaxies above redshift z > 0.5.  Selected under the most strict criteria, the group of 77 objects consists of a statistically important sample, which allows for analysis of physical properties of those rare passive giants. I will discuss the influence of compactness criteria on the sample size. Moreover I will present  VIPERS red nuggets number densities and discuss the environmental preferences of those exceptional galaxies.


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Thursday July 14, 2022
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IAC

Abstract

With the aim of detecting cosmological gas accretion onto galaxies of the local Universe, we examined the Ha emission in the halo of the 164 galaxies in the field of view of MUSE-Wide (Urrutia+19) with observable Ha (redshift < 0.42).  An exhaustive screening of the Ha images led us to select 118 reliable Ha emitting gas clouds. To our surprise, around 38 % of the time the Ha line profile shows a double peak centered at the rest-frame of the corresponding galaxy. We have explored several physical scenarios to explain this Ha emission, among which accretion disks around rogue  intermediate mass black holes (IMBHs) fit the observations best. I will describe the data analysis (to discard, e.g, instrumental artifacts and high redshift interlopers), the properties of the Ha emitting clumps (their fluxes, peak separation, and spatial distribution with respect to the central galaxy), and the arguments leading to the IMBH hypothesis rather than other alternatives (e.g., cosmological gas, expanding bubbles, or shocks in the circum galactic medium).


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