Galaxies, along with their underlying dark matter halos, constitute the building blocks of structure in the Universe. Of all fundamental forces, gravity is the dominant one that drives the evolution ...of structures from small density seeds at early times to the galaxies we see today. The interactions among myriads of stars, or dark matter particles, in a gravitating structure produce a system with fascinating connotations to thermodynamics, with some analogies and some fundamental differences. Ignacio Ferreras presents a concise introduction to extragalactic astrophysics, with emphasis on stellar dynamics, and the growth of density fluctuations in an expanding Universe. Additional chapters are devoted to smaller systems (stellar clusters) and larger ones (galaxy clusters). Fundamentals of Galaxy Dynamics, Formation and Evolution is written for advanced undergraduates and beginning postgraduate students, providing a useful tool to get up to speed in a starting research career. Some of the derivations for the most important results are presented in detail to enable students appreciate the beauty of maths as a tool to understand the workings of galaxies. Each chapter includes a set of problems to help the student advance with the material.
At a fixed stellar mass, the size of low-redshift early-type galaxies is found to be a factor of 2 larger than that of their counterparts at z∼ 1, a result with important implications for galaxy ...formation models. In this paper, we have explored the buildup of the local mass-size relation of elliptical galaxies using two visually classified samples. At low redshift, we compiled a subsample of 2656 elliptical galaxies from the Sloan Digital Sky Survey, whereas at higher redshift (up to z∼ 1), we extracted a sample of 228 objects from the Hubble Space Telescope/Advanced Camera for Surveys images of the Great Observatories Origins Deep Survey. All the galaxies in our study have spectroscopic data, allowing us to determine the age and mass of the stellar component. Contrary to previous claims in the literature, using the fossil record information contained in the stellar populations of our local sample, we do not find any evidence for an age segregation at a given stellar mass, depending on the size of the galaxies. At a fixed dynamical mass, there is only a ≲9 per cent size difference in the two extreme age quartiles of our sample. Consequently, the local evidence does not support a scenario whereby the present-day mass-size relation has been progressively established via a bottom-up sequence, where older galaxies occupy the lower part of this relation, remaining in place since their formation. We do not find any age-segregation difference in our high-z sample either. Therefore, we find a trend in size that is insensitive to the age of the stellar populations, at least since z∼ 1. This result supports the idea that the stellar mass-size relation is formed at z∼ 1, with all galaxies populating a region which roughly corresponds to 1/2 of the present size distribution. We have explored two possible scenarios for size growth: puffing up or minor merging. The fact that the evolution in size is independent of the stellar age, together with the absence of an increase in the scatter of the relationship with redshift does not support the puffing-up mechanism. The observational evidence, however, cannot reject at this stage the minor-merging hypothesis. We have made an estimation of the number of minor-merger events necessary to bring the high-z galaxies into the local relation compatible with the observed size evolution. Since z= 0.8, if the mass ratio of the merger is 1:3, then we estimate ∼3 ± 1 minor mergers and if the ratio is 1:10, then we obtain ∼8 ± 2 events.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
At present, the main challenge to the interpretation of variations in gravity-sensitive line strengths as driven by a non-universal initial mass function (IMF) lies in understanding the effect of the ...other population parameters. Most notably, α/Fe-enhanced populations or even departures in the individual element abundances with respect to the solar-scaled ratio may lead to similar observational results. We combine various TiO-based, IMF-sensitive indicators in the optical and NIR spectral windows, along with the FeH-based Wing–Ford band to break this degeneracy. We obtain a significant radial trend of the IMF slope in XSG1, a massive early-type galaxy
(ETG), with velocity dispersion σ ∼ 300 km s−1, observed with the Very Large Telescope/X-shooter instrument. In addition, we constrain – for the first time – both the shape and normalization of the IMF, using only a stellar population analysis. We robustly rule out a single power law to describe the IMF, whereas a power law tapered off to a constant value at low masses (defined as a bimodal IMF) is consistent with all the observational spectroscopic data and with the stellar M/L constraints based on the Jeans anisotropic modelling method. The IMF in XSG1 is bottom-heavy in the central regions (corresponding to a bimodal IMF slope Γb ∼ 3, or a mass normalization mismatch parameter α ∼ 2), changing towards a standard Milky Way-like IMF (Γb ∼ 1.3; α ∼ 1) at around one half of the effective radius. This result, combined with previous observations of local IMF variations in massive ETGs, reflects the varying processes underlying the formation of the central core and the outer regions in this type of galaxies.
We combine near-ultraviolet (NUV), optical and IR imaging of the nearby starburst galaxy M82 to explore the properties of the dust both in the interstellar medium of the galaxy and the dust entrained ...in the superwind. The three NUV filters of Swift-Ultraviolet/Optical Telescope enable us to probe in detail the properties of the extinction curve in the region around the 2175 Å bump. The NUV colour-colour diagram strongly rules out a 'bump-less' Calzetti-type law, which can either reflect intrinsic changes in the dust properties or in the star formation history compared to starbursts well represented by such an attenuation law. We emphasize that it is mainly in the NUV region where a standard Milky Way-type law is preferred over the Calzetti law. The age and dust distribution of the stellar populations is consistent with the scenario of an encounter with M81 in the recent 400 Myr. The radial variation of NUV/optical/IR photometry in the galaxy region - including the polycyclic-aromatic-hydrocarbon-dominated emission at 8 μm - confirms the central location of the star formation. The radial gradients of the NUV and optical colours in the superwind region supports the hypothesis that the emission in the wind cone is driven by scattering from dust grains entrained in the ejecta. The observed wavelength dependence, ∝λ−1.5, reveals either a grain size distribution n(a) ∝ a
−2.5, or a flatter distribution with a maximum size cutoff, suggesting that only small grains are entrained in the supernova-driven wind.
Este artigo tem como objetivo apresentar ao violoncelista um guia para a construção da obra “Mutationen II für Violoncelo und Tonband” (1969) de Claudio Santoro, tanto para a performance instrumental ...quanto para a gravação da parte eletroacústica. Originalmente escrita para execução com fita magnética, hoje o processo de montagem dos sons eletrônicos faz uso de ferramentas de gravação digital. Como produtos da pesquisa, temos o registro em vídeo da obra bem como a edição da partitura em português, pois anteriormente só existia o manuscrito em língua alemã. O trabalho auxilia o processo de aprendizado da peça por possíveis novos intérpretes, bem como a realização de performances públicas, difundindo assim a obra, que é uma das primeiras do repertório eletroacústico internacional escrito para violoncelo.
To test modified Newtonian dynamics (MOND) on galactic scales, we study six strong gravitational lensing early-type galaxies from the CASTLES sample. Comparing the total mass (from lensing) with the ...stellar mass content (from a comparison of photometry and stellar population synthesis), we conclude that strong gravitational lensing on galactic scales requires a significant amount of dark matter, even within MOND. On such scales a 2 eV neutrino cannot explain the excess of matter in contrast with recent claims to explain the lensing data of the bullet cluster. The presence of dark matter is detected in regions with a higher acceleration than the characteristic MOND scale of approximately 10(-10) m/s(2). This is a serious challenge to MOND unless lensing is qualitatively different possibly to be developed within a covariant, such as Tensor-Vector-Scalar (TeVeS), theory.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
We extract from the Sloan Digital Sky Survey a sample of 347 systems involving early-type galaxies separated by less than 30 kpc, in projection, and 500 km s−1 in radial velocity. These close pairs ...are likely progenitors of dry mergers. The (optical) spectra are used to determine how the interaction affects the star formation history and nuclear activity of the galaxies. The emission lines (or lack thereof) are used to classify the sample into AGN, star forming or quiescent. Increased AGN activity and reduced star formation in early-type pairs that already appear to be interacting indicate that the merging process changes the nature of nebular activity, a finding that is also supported by an increase in AGN luminosity with decreasing pair separation. Recent star formation is studied on the absorption-line spectra, both through the principal component analysis and via a comparison of the spectra with composite stellar population models. We find that the level of recent star formation in close pairs is raised relative to a control sample of early-type galaxies. This excess of residual star formation is found throughout the sample of close pairs and does not correlate with pair separation or with visual signs of interaction. Our findings are consistent with a scenario whereby the first stage of the encounter (involving the outer parts of the haloes) triggers residual star formation, followed by a more efficient inflow towards the centre – switching to an AGN phase – after which the systems are quiescent.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
We analyse the Tully-Fisher relation at moderate redshift from the point of view of the underlying stellar populations, by comparing optical and NIR photometry with a phenomenological model that ...combines population synthesis with a simple prescription for chemical enrichment. The sample comprises 108 late-type galaxies extracted from the FORS Deep Field and William Herschel Deep Field surveys at z 1 (median redshift z = 0.45). A correlation is found between stellar mass and the parameters that describe the star formation history, with massive galaxies forming their populations early (z
FOR ∼ 3), with star formation time-scales, τ1 ∼ 4 Gyr, although with very efficient chemical enrichment time-scales (τ2 ∼ 1 Gyr). In contrast, the stellar-to-dynamical mass ratio - which, in principle, would track the efficiency of feedback in the baryonic processes driving galaxy formation - does not appear to correlate with the model parameters. On the Tully-Fisher plane, no significant age segregation is found at fixed circular speed, whereas at fixed stellar-to-dynamical mass fraction, age splits the sample, with older galaxies having faster circular speeds at fixed M
s/M
dyn. Although our model does not introduce any prior constraint on dust reddening, we obtain a strong correlation between colour excess and stellar mass.
Esta pesquisa examina os elementos estilísticos provenientes da música folclórica da Região da Puna, encontrados na Puneña n.º 2, Op. 45 para violoncelo solo de Alberto Ginastera, com o objetivo de ...embasar violoncelistas interessados no seu estudo e na sua performance. Como procedimento metodológico, foram estudados autores como Aretz (2003, 2008), Aguilar (2007) e Falú (2011), com o intuito de melhor compreender a música folclórica da Região da Puna e das culturas pré-hispânicas, e Suárez Urtubey (1967, 1972, 2003), que discorre sobre a vida e obra do compositor. A partir do levantamento bibliográfico, foram expostos ideias e conceitos que auxiliam o intérprete a decodificar aspectos relevantes da obra. Além disso, foi realizada uma análise detalhada de como o compositor coloca em jogo os recursos pesquisados ao compor para o violoncelo, destacando alguns aspectos idiomáticos.
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