Found 70 talks width keyword galaxy evolution

Wednesday January 8, 2014
Dr. Ruben Sanchez-Janssen
NRC Herzberg Institute of Astrophysics


Two competing effects appear to govern galaxy multiplicity (pairs orgroups) at low masses: while associations of low-mass haloes are naturally expected in a LCDM cosmology, galaxy formation within these haloes is thought to be rendered inefficient due to the action of several ionizing agents. Yet associations of dwarf galaxies are known to exist in the Local Volume, and their frequency appears to be unexpectedly high for LCDM expectations even in our own Local Group. Unfortunately, it is not yet well understood what role do interactions between low-mass galaxies play in determining their star formation histories, structural properties, and neutral gas content. Here I will present an investigation of the impact of dwarf-dwarf galaxy tidal interactions on their morphological and star formation properties. The UGC5205 close pair consists of two low-mass (M* ~ 5E7 Msun), late-type galaxies with a relative projected distance of only 10 kpc, and no nearby massive companions. I will show that these equal-mass interactions can be an important 'pre-processing' mechanism that acts before dwarfs are affected by a more massive central galaxy, profoundly impacting their star formation histories and morphologies.

Tuesday December 3, 2013
Dr. Ignacio Trujillo


As early as 10 Gyr ago, galaxies with more than 10^11 M* in stars already existed. While most of these massive galaxies must have subsequently transformed through on-going star formation and mergers with other galaxies, a small fraction (<0.1%) may have survived untouched till today. Searches for such relic galaxies, useful windows to explore the early Universe, have been inconclusive to date. In this talk, we will present the first case of a nearby galaxy, NGC1277 (at a distance of 73 Mpc in the Perseus galaxy cluster), which fulfils many criteria to be considered a relic galaxy. Using deep optical spectroscopy, we derive the star formation history along the structure of the galaxy: the stellar populations are uniformly old (>10 Gyr) with no evidence for more recent star formation episodes. The metallicity of their stars is super-solar ([Fe/H]=0.20+-0.04 with a smooth decline towards the outer regions) and alpha enriched ([alpha/Fe]=0.4+-0.1). This suggests a very short formation time scale for the bulk of stars of this galaxy. This object also rotates very fast (V_{rot}~300 km/s) and has a large central velocity dispersion (sigma>300 km/s). NGC1277 allows the explorations in full detail of properties such as the structure, internal dynamics, metallicity and initial mass function at ~10-12 Gyr back in time when the first massive galaxies were built.

Thursday October 10, 2013
Dr. Alberto Molino


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.

Tuesday October 8, 2013
Dr. Heidi Lietzen


Galaxies in different environments have different properties. In dense environments galaxies are more likely to be red, passive ellipticals than in less dense environments. This difference can be detected both on small and large-scale environments. In this talk, I will present results on galaxy populations in different environments on two scales: the group scale and the supercluster scale. The goal of our project is to find out if there are differences between massive galaxies in similar groups, but different large-scale environments. The results will tell if the evolution of galaxies is fully determined by the mass of their dark matter halo, or if the large-scale environment also play a role. 

Tuesday July 30, 2013
Dr. Ezequiel Treister
Universidad de Concepción


It is now clear that supermassive black holes (M>1e6 Msun) live in the center of most (all) galaxies, including our own Milky Way. Furthermore, the energy released during the growth of this black hole is a critical ingredient in understanding galaxy formation and evolution. In this talk, I will show what we know about how, when and where these supermassive black holes are acquiring their masses. In particular, I will focus on the effects of obscuration, as it is now clear that the majority of this black hole growth is hidden from our view by large amounts of gas and dust. I will present statistical evidence suggesting that while most nuclear activity is triggered by internal secular processes, the most violent episodes are linked to major galaxy mergers. Finally, I will show how future data obtained combining observations with the ALMA radio telescope and the NuSTAR X-ray observatory will allow us to understand the physical details of the connection between black hole growth and galaxy evolution.

Wednesday June 19, 2013
Dr. Margaret Meixner
Space Telescope Science Institute (STScI)


The life cycle of baryonic matter in a galaxy is driven by the exchange of material between the interstellar medium (ISM) and stars, which are the agents of galaxy evolution. Dust is present at these key transition phases of matter: in the ISM, in the circumstellar environments of newly forming stars and in stellar ejecta of dying stars. The Spitzer and Herschel wavelengths provide a sensitive probe of circumstellar and interstellar dust and hence, allows us to study the physical processes of the ISM, the formation of new stars and the injection of mass by evolved stars and their relationships on a galaxy-wide scale. Due to their proximity, well constrained viewing angle, multi-wavelength information, and measured tidal interactions with the Milky Way (MW), the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are uniquely suited for surveying the agents of galaxy evolution (SAGE), the ISM and stars. In this talk, I will present some key results from the Spitzer SAGE and Herschel HERITAGE surveys including measurements of ISM mass estimates from dust emission, discoveries of thousands of young stellar object candidates, and precise measurements of dust mass loss rates from entire populations of evolved stars and w the mass budgets of these galaxies. I will end with a brief forward look to the future prospects with the James Webb Space Telescope Mission.

Tuesday June 11, 2013
Dr. Jorge Sánchez Almeida


The direct accretion of pristine gas streams is predicted to be the main mode of galaxy disk growth in the early universe (cold-flows). We (think we) have discovered this physical process at work in the local Universe. The finding is one of the outcomes of our in-depth study of local extremely metal poor (XMP) galaxies. I will explain the main observational properties of XMPs, in particular, their tendency to have cometary or tadpole morphology, with a bright peripheral clump (the head) on a faint tail. Tadpole galaxies are rare in the nearby universe but turn out to be very common at high redshift, where they are usually interpreted as disk galaxies in early stages of assembling. We have found the heads to be giant HII regions displaced with respect to the rotation center, with the galaxy metallicity being smallest at the head and larger elsewhere. The resulting chemical abundance gradient is opposite to the one observed in local spirals, and suggests a recent gas accretion episode onto the head. Thus, local XMP galaxies seem to be primitive disks, with their star formation sustained by accretion of external metal poor gas. I will argue how the same mechanism may be driving the star formation in many other local galaxies. Ongoing observational projects to confirm these findings and conjectures will be briefly mentioned.

Tuesday May 28, 2013
Dr. Enrique Pérez Montero



 Chemical abundances derived using emission-line spectra in ionized gaseous nebulae are between the most useful properties that can be derived to understand the evolution of galaxies from the local Universe up to very high redshifts. Since nitrogen is one of the most abundant metals in the gas-phase of galaxies and its emission-lines can be measured many times instead of those emitted by oxygen, it is important to be aware of the implications of the variations in the nitrogen-to-oxygen ratio for the derivation of total metallicity and what are the advantages of using this abundance ratio to derive other evolutionary properties in different emission-line objects. We will also see the utility of some observational techniques, such integral field spectroscopy, to disentangle between different processes implied in the excess of observed nitrogen as derived from integrated observations.

Tuesday April 23, 2013
Dr. Ignacio Trujillo


Taking advantage of the ultra-deep near-infrared imaging obtained with the Hubble Space Telescope on the Hubble Ultra Deep Field, we detect and explore for the first time the properties of the stellar haloes of two Milky Way-like galaxies at z~1. We find that the structural properties of those haloes (size and shape) are similar to the ones found in the local universe. However, these high-z stellar haloes are approximately three magnitudes brighter and exhibit bluer colours ((g-r)<0.3 mag) than their local counterparts. The stellar populations of z~1 stellar haloes are compatible with having ages <1 Gyr. This implies that the stars in those haloes were formed basically at 1<z<2. This result matches very well the theoretical predictions that locate most of the formation of the stellar haloes at those early epochs. A pure passive evolutionary scenario, where the stellar populations of our high-z haloes simply fade to match the stellar halo properties found in the local universe, is consistent with our data.

Tuesday March 19, 2013
Dr. Nicolas Laporte


Evolution of galaxies is relatively well known up to z ~ 5, but beyond this limit and regarding the few number of galaxies confirmed by spectroscopy, their evolution is still uncertain. In the last five years, many projects and instruments aiming at pushing the limits of the Universe have emerged. Among them, the WIRCam Ultra Deep Survey (WUDS), a very large (~400 arcmin^2 field of view) and deep (m_H=27.00 AB) survey covering wavelength from Y to Ks bands, dedicated to select the brightest sources at z > 4.5, has just been finished.This survey takes benefit from the deep images from the CFHT-LS (Groth Strip) in u, g, r, i and z-band to improve the wavelength coverage and thus the determination of photometric redshift in each sample. The evolution of galaxies has been studied through the evolution of the UV Luminosity Function from z~5 up to z~9. During this talk I will present you the WIRCam Ultra Deep Survey and the most popular method used to select the very high-redshift sources. Then I will focus on the determination of the luminosity function and on the implications of this evolution on the Epoch of Reionization. I will finish this presentation by giving some perspectives, and especially the results that we can expected from futures instruments and telescopes (e.g. EMIR @ GTC, KMOS and MUSE @ VLT, JWST, E-ELT).

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