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A equação de Lane-Emden-Fowler em teoria classica de campos e astrofisica estelar; The Lane-Emden-Fowler equation in classical field theory and stellar astrophysics

Marcelo Cristino Gama
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 15/07/2008 Português
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Neste trabalho buscamos soluções exatas não-triviais da Equação de LaneEmden-Fowler. Esta equação tem aplicações importantes em Teoria de Campos não-linear, bem como em Astrofísica Estelar. Inicialmente, a partir do formalismo da Integral Primeira, obtemos soluções para um modelo >.~n+1 com n = 2,3,5, utilizando Integrais Elípticas de Jacobi. Segue-se então o cálculo de flutuações no modelo >.~n+1 para um campo clássico ~ sujeito a um potencial da forma V(φ) = -1/2 m2φ2 + λ/n+1 φn+1, em torno de uma solução estática. Uma outra aplicação é no estudo das configurações de Equilíbrio Hidrostático de estrelas esféricas politrópicas. Mostramos que o método da Integral Primeira fornece uma série de soluções singulares na origem. Também é obtida a bem conhecida solução de Chandrasekhar, que é regular na origem.; In this work we search for non-trivial exact solutions to the Lane-Emden-Fowler’s Equation. That equation has important applications in Non-linear Field Theory, as well in Stellar Astrophysics. Initially, from the First Integral formalism, we obtain solutions for a λφn+1 model with n = 2, 3, 5, using Jacobian Elliptic Integrals. Follows the calculation of the fluctuations in the λφn+1 model for a classical field φ in a potential of the form..Another application is the study of the Hydrostatic Equilibrium configuration of politropic spherical stars. We show the First Integral Method gives solutions that are singular at the origin. In addition we obtain the well known Chandrasekhar’s solution...

Dating the formation of the counter-rotating stellar disc in the spiral galaxy NGC 5719 by disentangling its stellar populations

Coccato, Lodovico; Morelli, Lorenzo; Corsini, Enrico Maria; Buson, Lucio Maria; Pizzella, Alessandro; Vergani, Daniela; Bertola, Francesco
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We present the results of the VLT/VIMOS integral-field spectroscopic observations of the inner 28"x28" (3.1 kpc x 3.1 kpc) of the interacting spiral NGC 5719, which is known to host two co-spatial counter-rotating stellar discs. At each position in the field of view, the observed galaxy spectrum is decomposed into the contributions of the spectra of two stellar and one ionised-gas components. We measure the kinematics and the line strengths of the Lick indices of the two stellar counter-rotating components. We model the data of each stellar component with single stellar population models that account for the alpha/Fe overabundance. We also derive the distribution and kinematics of the ionised-gas disc, that is associated with the younger, less rich in metals, more alpha-enhanced, and less luminous stellar component. They are both counter-rotating with respect the main stellar body of the galaxy. These findings prove the scenario where gas was accreted first by NGC 5719 onto a retrograde orbit from the large reservoir available in its neighbourhoods as the result of the interaction with its companion NGC 5713, and subsequently fuelled the in situ formation of the counter-rotating stellar disc.; Comment: 5 pages, 4 figures. Accepted for publication in MNRAS letters. Reference list updated

Gamma-Ray Line Astrophysics and Stellar Nucleosynthesis: Perspectives for INTEGRAL

Prantzos, N.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/01/1999 Português
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Nuclear gamma-ray lines constitute the most genuine diagnostic tool of nuclear astrophysics, since they allow for an unambiguous identification of isotopic species. Continuous improvement in instrumentation led to the discovery of several radioactive species in the past 15 years (Al26, Co56, Co57, Ti44) in various astrophysical sites (SN1987A and SN1991T, Cas-A, the Milky Way disk). These discoveries boosted theoretical activity on the nucleosynthesis of these radioactive isotopes and on the refined modelling of the corresponding sites, improving our knowledge on stellar evolution, stellar explosions, galactic structure, etc. I review here the current status of gamma-ray line astrophysics and present some perspectives related to stellar nucleosynthesis, in view of future missions like INTEGRAL.; Comment: Invited Review Paper in : Third INTEGRAL Workshop "The Extreme Universe", Taormina-Italy (1998), 8 pages

Spectroscopic evidence of distinct stellar populations in the counter-rotating stellar disks of NGC 3593 and NGC 4550

Coccato, L.; Morelli, L.; Pizzella, A.; Corsini, E. M.; Buson, L. M.; Bonta', E. Dalla
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/10/2012 Português
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We present the results of integral-field spectroscopic observations of the two disk galaxies NGC 3593 and NGC 4550 obtained with VIMOS/VLT. Both galaxies are known to host 2 counter-rotating stellar disks, with the ionized gas co-rotating with one of them. We measured in each galaxy the ionized gas kinematics and metallicity, and the surface brightness, kinematics, mass surface density, and the stellar populations of the 2 stellar components to constrain the formation scenario of these peculiar galaxies. We applied a novel spectroscopic decomposition technique to both galaxies, to separate the relative contribution of the 2 counter-rotating stellar and one ionized-gas components to the observed spectrum. We measured the kinematics and the line strengths of the Lick indices of the 2 counter-rotating stellar components. We modeled the data of each stellar component with single stellar population models that account for the alpha/Fe overabundance. In both galaxies we successfully separated the main from the secondary stellar component that is less massive and rotates in the same direction of the ionized-gas component. The 2 stellar components have exponential surface-brightness profiles. In both galaxies, the two counter-rotating stellar components have different stellar populations: the secondary stellar disk is younger...

Stellar populations of galaxies in the ALHAMBRA survey up to $z \sim 1$. I. MUFFIT: A Multi-Filter Fitting code for stellar population diagnostics

Díaz-García, L. A.; Cenarro, A. J.; López-Sanjuan, C.; Ferreras, I.; Varela, J.; Viironen, K.; Cristóbal-Hornillos, D.; Moles, M.; Marín-Franch, A.; Arnalte-Mur, P.; Ascaso, B.; Cerviño, M.; González-Delgado, R. M.; Márquez, I.; Masegosa, J.; Moli
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/05/2015 Português
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We present MUFFIT, a new generic code optimized to retrieve the main stellar population parameters of galaxies in photometric multi-filter surveys, and we check its reliability and feasibility with real galaxy data from the ALHAMBRA survey. Making use of an error-weighted $\chi^2$-test, we compare the multi-filter fluxes of galaxies with the synthetic photometry of mixtures of two single stellar populations at different redshifts and extinctions, to provide through a Monte Carlo method the most likely range of stellar population parameters (mainly ages and metallicities), extinctions, redshifts, and stellar masses. To improve the diagnostic reliability, MUFFIT identifies and removes from the analysis those bands that are significantly affected by emission lines. We highlight that the retrieved age-metallicity locus for a sample of $z \le 0.22$ early-type galaxies in ALHAMBRA at different stellar mass bins are in very good agreement with the ones from SDSS spectroscopic diagnostics. Moreover, a one-to-one comparison between the redshifts, ages, metallicities, and stellar masses derived spectroscopically for SDSS and by MUFFIT for ALHAMBRA reveals good qualitative agreements in all the parameters. In addition, and using as input the results from photometric-redshift codes...

Stellar population and the origin of intra-cluster stars around brightest cluster galaxies: the case of NGC 3311

Coccato, L.; Gerhard, O.; Arnaboldi, M.; Ventimiglia, G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/08/2011 Português
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Context. We investigate the stellar population and the origin of diffuse light around brightest cluster galaxies. Aims. We study the stellar population of the dynamically hot stellar halo of NGC 3311, the brightest galaxy in the Hydra I cluster, and that of photometric substructures in the diffuse light to constrain the origin of these components. Methods. We analyze absorption lines in medium-resolution, long-slit spectra in the wavelength range 4800-5800 angstrom obtained with FORS2 at the Very Large Telescope. We measure the equivalent width of Lick indices out to 20 kpc from the center of NGC 3311 and fit them with stellar population models that account for the [alpha/Fe] overabundance. Results. Stars in the dynamically hot halo of NGC 3311 are old (age > 13 Gyr), metal-poor ([Z/H] ~ -0.35), and alpha-enhanced ([alpha/Fe] ~ 0.48). Together with the high velocity dispersion, these measurements indicate that the stars in the halo were accreted from the outskirts of other early-type galaxies, with a possible contribution from dwarf galaxies. We identify a region in the halo of NGC 3311 associated with a photometric substructure where the stellar population is even more metal-poor ([Z/H] ~ -0.73). In this region, our measurements are consistent with a composite stellar population superposed along the line of sight...

Reconstructing the stellar mass distributions of galaxies using S4G IRAC 3.6 and 4.5 micron images: II. The conversion from light to mass

Meidt, Sharon E.; Schinnerer, Eva; van de Ven, Glenn; Zaritsky, Dennis; Peletier, Reynier; Knapen, Johan; Sheth, Kartik; Regan, Michael; Querejeta, Miguel; Munoz-Mateos, Juan-Carlos; Kim, Taehyun; Hinz, Joannah L.; de Paz, Armando Gil; Athanassoula, E.; B
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/02/2014 Português
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476.87%
We present a new approach for estimating the 3.6 micron stellar mass-to-light ratio in terms of the [3.6]-[4.5] colors of old stellar populations. Our approach avoids several of the largest sources of uncertainty in existing techniques. By focusing on mid-IR wavelengths, we gain a virtually dust extinction-free tracer of the old stars, avoiding the need to adopt a dust model to correctly interpret optical or optical/NIR colors normally leveraged to assign M/L. By calibrating a new relation between NIR and mid-IR colors of GLIMPSE giant stars we also avoid discrepancies in model predictions for the [3.6]-[4.5] colors of old stellar populations due to uncertainties in molecular line opacities. We find that the [3.6]-[4.5] color, which is driven primarily by metallicity, provides a tight constraint on M/L_3.6, which varies intrinsically less than at optical wavelengths. The uncertainty on M/L_3.6 of ~0.07 dex due to unconstrained age variations marks a significant improvement on existing techniques for estimating the stellar M/L with shorter wavelength data. A single M/L_3.6=0.6 (assuming a Chabrier IMF), independent of [3.6]-[4.5] color, is also feasible as it can be applied simultaneously to old, metal-rich and young, metal-poor populations...

Halo Mass and Assembly History Exposed in the Faint Outskirts: the Stellar and Dark Matter Haloes of Illustris Galaxies

Pillepich, Annalisa; Vogelsberger, Mark; Deason, Alis; Rodriguez-Gomez, Vicente; Genel, Shy; Nelson, Dylan; Torrey, Paul; Sales, Laura V.; Marinacci, Federico; Springel, Volker; Sijacki, Debora; Hernquist, Lars
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We use the Illustris Simulations to gain insight into the build-up of the outer, low-surface brightness regions which surround galaxies. We characterize the stellar haloes by means of the logarithmic slope of the spherically-averaged stellar density profiles, alphaSTARS at z=0, and we relate these slopes to the properties of the underlying Dark-Matter (DM) haloes, their central galaxies, and their assembly histories. We analyze a sample of ~5,000 galaxies resolved with more than 5x10^4 particles each, and spanning a variety of morphologies and halo masses (3x10^11 < Mvir < 10^14 Msun). We find a strong trend between stellar halo slope and total halo mass, where more massive objects have shallower stellar haloes than the less massive ones (-5.5 \pm 0.5 < alphaSTARS <-3.5 \pm 0.2 in the studied mass range). At fixed halo mass, we show that disk-like, blue, young, and more massive galaxies are surrounded by significantly steeper stellar haloes than elliptical, red, older, and less massive galaxies. Overall, the stellar density profiles fall off much more steeply than the underlying DM, and no clear trend holds between stellar slope and DM halo concentration. However, DM haloes which formed more recently, or which accreted larger fractions of stellar mass from infalling satellites...

On the spectral resolution of the MILES stellar library

Beifiori, A.; Maraston, C.; Thomas, D.; Johansson, J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/12/2010 Português
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Empirical stellar libraries are extensively used to extract stellar kinematics in galaxies and to build stellar population models. An accurate knowledge of the spectral resolution of these libraries is critical to avoid propagation errors and uncertain estimates of the intrinsic stellar velocity dispersion of galaxies. In this research note we re-assess the spectral resolution of the MILES stellar library and of the stellar population models based on it. This exercise was performed, because of a recent controversy over the exact MILES resolution. We perform our test through the comparison of MILES stellar spectra with three different sets of higher-resolution templates, one fully theoretical - the MARCS library - and two empirical ones, namely the Indo-U.S. and ELODIE v3.1 libraries. The theoretical template has a well-defined very high (R=20000) resolution. Hence errors on this theoretical value do not affect our conclusions. Our approach based on the MARCS library was crucial to constrain the values of the resolution also for the other two empirical templates. We find that the MILES resolution has previously been slightly overestimated. We derive a new spectral resolution of 2.54 A FWHM, instead of the nominal 2.3 A. The reason for this difference is due to an overestimation of the resolution for the Indo-U.S. library that was previously used for estimates of the MILES resolution. For the Indo-U.S. we obtain a new value of 1.35 A FWHM. Most importantly...

Constraining Satellite Galaxy Stellar Mass Loss and Predicting Intrahalo Light I: Framework and Results at Low Redshift

Watson, Douglas F.; Berlind, Andreas A.; Zentner, Andrew R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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477.421%
We introduce a new technique that uses galaxy clustering to constrain how satellite galaxies lose stellar mass and contribute to the diffuse "intrahalo light" (IHL). We implement two models that relate satellite galaxy stellar mass loss to the detailed knowledge of subhalo dark matter mass loss. Model 1 assumes that the fractional stellar mass loss of a galaxy is proportional to the fractional amount of dark matter mass loss of its subhalo. Model 2 accounts for a delay in the time that stellar mass is lost since the galaxy resides deep in the potential well of the subhalo which may experience dark matter mass loss for some time before the galaxy is affected. We use these models to predict the stellar masses of a population of galaxies and use abundance matching to predict the clustering of several r-band luminosity threshold samples from the Sloan Digital Sky Survey. Abundance matching assuming no stellar mass loss (akin to abundance matching at the time of subhalo infall) over-estimates the correlation function on small scales (<~ 1 Mpc), while allowing too much stellar mass loss leads to an under-estimate. For each sample, we are thus able to constrain the amount of stellar mass loss required to match the observed clustering. We find that less luminous satellite galaxies experience more efficient stellar mass loss than luminous satellites. From these models...

Galaxies on FIRE (Feedback In Realistic Environments): Stellar Feedback Explains Cosmologically Inefficient Star Formation

Hopkins, Philip F.; Keres, Dusan; Onorbe, Jose; Faucher-Giguere, Claude-Andre; Quataert, Eliot; Murray, Norm; Bullock, James S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We present a series of high-resolution cosmological simulations of galaxy formation to z=0, spanning halo masses ~10^8-10^13 M_sun, and stellar masses ~10^4-10^11. Our simulations include fully explicit treatment of both the multi-phase ISM (molecular through hot) and stellar feedback. The stellar feedback inputs (energy, momentum, mass, and metal fluxes) are taken directly from stellar population models. These sources of stellar feedback, with zero adjusted parameters, reproduce the observed relation between stellar and halo mass up to M_halo~10^12 M_sun (including dwarfs, satellites, MW-mass disks, and small groups). By extension, this leads to reasonable agreement with the stellar mass function for M_star<10^11 M_sun. We predict weak redshift evolution in the M_star-M_halo relation, consistent with current constraints to z>6. We find that the M_star-M_halo relation is insensitive to numerical details, but is sensitive to the feedback physics. Simulations with only supernova feedback fail to reproduce the observed stellar masses, particularly in dwarf and high-redshift galaxies: radiative feedback (photo-heating and radiation pressure) is necessary to disrupt GMCs and enable efficient coupling of later supernovae to the gas. Star formation rates agree well with the observed Kennicutt relation at all redshifts. The galaxy-averaged Kennicutt relation is very different from the numerically imposed law for converting gas into stars in the simulation...

The Emission by Dust and Stars of Nearby Galaxies in the Herschel KINGFISH Survey

Skibba, Ramin A.; Engelbracht, Charles W.; Dale, Daniel; Hinz, Joannah; Zibetti, Stefano; Crocker, Alison; Groves, Brent; Hunt, Leslie; Johnson, Benjamin D.; Meidt, Sharon; Murphy, Eric J.; Appleton, Philip; Armus, Lee; Bolatto, Alberto; Brandl, Bernhard;
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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476.70824%
Using new far-infrared imaging from the Herschel Space Observatory with ancillary data from ultraviolet to submillimeter wavelengths, we estimate the total emission from dust and stars of 62 nearby galaxies in the KINGFISH survey in a way that is as empirical and model-independent as possible. We collect and exploit these data in order to measure from the spectral energy distributions (SEDs) precisely how much stellar radiation is intercepted and re-radiated by dust, and how this quantity varies with galaxy properties. By including SPIRE data, we are more sensitive to emission from cold dust grains than previous analyses at shorter wavelengths, allowing for more accurate estimates of dust temperatures and masses. The dust/stellar flux ratio, which we measure by integrating the SEDs, has a range of nearly three decades. The inclusion of SPIRE data shows that estimates based on data not reaching these far-IR wavelengths are biased low. We find that the dust/stellar flux ratio varies with morphology and total IR luminosity. We also find that dust/stellar flux ratios are related to gas-phase metallicity, while the dust/stellar mass ratios are less so. The substantial scatter between dust/stellar flux and dust/stellar mass indicates that the former is a poor proxy of the latter. Comparing the dust/stellar flux ratios and dust temperatures...

Galaxy formation with cold gas accretion and evolving stellar initial mass function

Kang, Xi; Lin, WeiPeng; Skibba, Ramin A.; Chen, Dongni
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/03/2010 Português
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The evolution of the galaxy stellar mass function is especially useful to test the current model of galaxy formation. Observational data have revealed a few inconsistencies with predictions from the $\Lambda {\rm CDM}$ model. For example, most massive galaxies have already been observed at very high redshifts, and they have experienced only mild evolution since then. In conflict with this, semi-analytical models of galaxy formation predict an insufficient number of massive galaxies at high redshift and a rapid evolution between redshift 1 and 0 . In addition, there is a strong correlation between star formation rate and stellar mass for star-forming galaxies, which can be roughly reproduced with the model, but with a normalization that is too low at high redshift. Furthermore, the stellar mass density obtained from the integral of the cosmic star formation history is higher than the measured one by a factor of 2. In this paper, we study these issues using a semi-analytical model that includes: 1) cold gas accretion in massive halos at high redshift; 2) tidal stripping of stellar mass from satellite galaxies; and 3) an evolving stellar initial mass function (bottom-light) with a higher gas recycle fraction. Our results show that the combined effects from 1) and 2) can predict sufficiently massive galaxies at high redshifts and reproduce their mild evolution at low redshift...

Stellar Ages and Metallicities of Central and Satellite Galaxies: Implications for Galaxy Formation and Evolution

Pasquali, Anna; Gallazzi, Anna; Fontanot, Fabio; Bosch, Frank C. van den; De Lucia, Gabriella; Mo, H. J.; Yang, Xiaohu
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/12/2009 Português
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Using a large SDSS galaxy group catalogue, we study how the stellar ages and metallicities of central and satellite galaxies depend on stellar mass and halo mass. We find that satellites are older and metal-richer than centrals of the same stellar mass. In addition, the slopes of the age-stellar mass and metallicity-stellar mass relations are found to become shallower in denser environments. This is due to the fact that the average age and metallicity of low mass satellite galaxies increase with the mass of the halo in which they reside. A comparison with the semi-analytical model of Wang et al. (2008) shows that it succesfully reproduces the fact that satellites are older than centrals of the same stellar mass and that the age difference increases with the halo mass of the satellite. This is a consequence of strangulation, which leaves the stellar populations of satellites to evolve passively, while the prolonged star formation activity of centrals keeps their average ages younger. The resulting age offset is larger in more massive environments because their satellites were accreted earlier. The model fails, however, in reproducing the halo mass dependence of the metallicities of low mass satellites, yields metallicity-stellar mass and age-stellar mass relations that are too shallow...

Tracing the Evolution of High Redshift Galaxies Using Stellar Abundances

Crosby, Brian D.; O'Shea, Brian W.; Beers, Timothy C.; Tumlinson, Jason
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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This paper presents the first results from a model for chemical evolution that can be applied to N-body cosmological simulations and quantitatively compared to measured stellar abundances from large astronomical surveys. This model convolves the chemical yield sets from a range of stellar nucleosynthesis calculations (including AGB stars, Type Ia and II supernovae, and stellar wind models) with a user-specified stellar initial mass function (IMF) and metallicity to calculate the time-dependent chemical evolution model for a "simple stellar population" of uniform metallicity and formation time. These simple stellar population models are combined with a semi-analytic model for galaxy formation and evolution that uses merger trees from N-body cosmological simulations to track several $\alpha$- and iron-peak elements for the stellar and multiphase interstellar medium components of several thousand galaxies in the early ($z \geq 6$) universe. The simulated galaxy population is then quantitatively compared to two complementary datasets of abundances in the Milky Way stellar halo, and is capable of reproducing many of the observed abundance trends. The observed abundance ratio distributions are qualitatively well matched by our model, and the observational data is best reproduced with a Chabrier IMF...

Panchromatic Averaged Stellar Populations: PaasP

Riffel, Rogério; Bonatto, Charles; Fernandes Jr, Roberto Cid; Pastoriza, Miriani G.; Balbinot, and Eduardo
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/10/2010 Português
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We study how the spectral fitting of galaxies, in terms of light fractions derived in one spectral region translates into another region, by using results from evolutionary synthesis models. In particular, we examine propagation dependencies on Evolutionary Population Synthesis (EPS, {\sc grasil}, {\sc galev}, Maraston and {\sc galaxev}) models, age, metallicity, and stellar evolution tracks over the near-UV---near infrared (NUV---NIR, 3500\AA\ to 2.5\mc) spectral region. Our main results are: as expected, young ($t \lesssim$ 400 Myr) stellar population fractions derived in the optical cannot be directly compared to those derived in the NIR, and vice versa. In contrast, intermediate to old age ($t \gtrsim$ 500 Myr) fractions are similar over the whole spectral region studied. The metallicity has a negligible effect on the propagation of the stellar population fractions derived from NUV --- NIR. The same applies to the different EPS models, but restricted to the range between 3800 \AA\ and 9000 \AA. However, a discrepancy between {\sc galev}/Maraston and {\sc grasil}/{\sc galaxev} models occurs in the NIR. Also, the initial mass function (IMF) is not important for the synthesis propagation. Compared to {\sc starlight} synthesis results...

Triple Microlens OGLE-2008-BLG-092L: Binary Stellar System with a Circumprimary Uranus-type Planet

Poleski, Radosław; Skowron, Jan; Udalski, Andrzej; Han, Cheongho; Kozłowski, Szymon; Wyrzykowski, Łukasz; Dong, Subo; Szymański, Michał K.; Kubiak, Marcin; Pietrzyński, Grzegorz; Soszyński, Igor; Ulaczyk, Krzysztof; Pietrukowicz, Paweł; Gould, And
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We present the gravitational microlensing discovery of a 4 M_Uranus planet that orbits a 0.7 M_Sun star at ~18 AU. This is the first known analog of Uranus. Similar planets, i.e., cold ice-giants, are inaccessible to either radial velocity or transit methods because of the long orbital periods, while low reflected light prevents direct imaging. We discuss how similar planets may contaminate the sample of the very short microlensing events that are interpreted as free-floating planets with an estimated rate of 1.8 per main sequence star. Moreover, the host star has a nearby stellar (or brown dwarf) companion. The projected separation of the planet is only ~3 times smaller than that of the companion star, suggesting significant dynamical interactions.; Comment: published in ApJ; the photometry and the code used for fitting the double-lens extended-source (with limb darkening) microlensing model are attached as ancillary files

Probing baryonic processes and gastrophysics in the formation of the Milky Way dwarf satellites: I. metallicity distribution properties

Hou, Jun; Yu, Qingjuan; Lu, Youjun
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 16/06/2014 Português
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477.252%
In this paper, we study the chemical properties of the stars in the dwarf satellites around the MW-like host galaxies, and explore the possible effects of several baryonic processes, including supernova (SN) feedback, the reionization of the universe and H$_2$ cooling, on them and how current and future observations may put some constraints on these processes. We use a semi-analytical model to generate MW-like galaxies, for which a fiducial model can reproduce the luminosity function and the stellar metallicity--stellar mass correlation of the MW dwarfs. Using the simulated MW-like galaxies, we focus on investigating three metallicity properties of their dwarfs: the stellar metallicity--stellar mass correlation of the dwarf population, and the metal-poor and metal-rich tails of the stellar metallicity distribution in individual dwarfs. We find that (1) the slope of the stellar metallicity--stellar mass correlation is sensitive to the SN feedback strength and the reionization epoch; (2) the extension of the metal-rich tails is mainly sensitive to the SN feedback strength; (3) the extension of the metal-poor tails is mainly sensitive to the reionization epoch; (4) none of the three chemical properties are sensitive to the H$_2$ cooling process; and (5) comparison of our model results with the current observational slope of the stellar metallicity--stellar mass relation suggests that the local universe is reionized earlier than the cosmic average and local sources may have a significant contribution to the reionization in the local region...

New constraints on the evolution of the stellar-to-dark matter connection: a combined analysis of galaxy-galaxy lensing, clustering, and stellar mass functions from z=0.2 to z=1

Leauthaud, Alexie; Tinker, Jeremy; Bundy, Kevin; Behroozi, Peter S.; Massey, Richard; Rhodes, Jason; George, Matthew R.; Kneib, Jean-Paul; Benson, Andrew; Wechsler, Risa H.; Busha, Michael T.; Capak, Peter; Cortes, Marina; Ilbert, Olivier; Koekemoer, Anto
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/04/2011 Português
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476.67883%
Using data from the COSMOS survey, we perform the first joint analysis of galaxy-galaxy weak lensing, galaxy spatial clustering, and galaxy number densities. Carefully accounting for sample variance and for scatter between stellar and halo mass, we model all three observables simultaneously using a novel and self-consistent theoretical framework. Our results provide strong constraints on the shape and redshift evolution of the stellar-to-halo mass relation (SHMR) from z=0.2 to z=1. At low stellar mass, we find that halo mass scales as Mh M*^0.46 and that this scaling does not evolve significantly with redshift to z=1. We show that the dark-to-stellar ratio, Mh/M*, varies from low to high masses, reaching a minimum of Mh/M*~27 at M*=4.5x10^10 Msun and Mh=1.2x10^12 Msun. This minimum is important for models of galaxy formation because it marks the mass at which the accumulated stellar growth of the central galaxy has been the most efficient. We describe the SHMR at this minimum in terms of the "pivot stellar mass", M*piv, the "pivot halo mass", Mhpiv, and the "pivot ratio", (Mh/M*)piv. Thanks to a homogeneous analysis of a single data set, we report the first detection of mass downsizing trends for both Mhpiv and M*piv. The pivot stellar mass decreases from M*piv=5.75+-0.13x10^10 Msun at z=0.88 to M*piv=3.55+-0.17x10^10 Msun at z=0.37. Intriguingly...

On the origin of the stellar halo and multiple stellar populations in the globular cluster NGC 1851

Bekki, Kenji; Yong, David
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/09/2011 Português
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We propose that the observed stellar halo around the globular cluster (GC) NGC 1851 is evidence for its formation in the central region of its defunct host dwarf galaxy. We numerically investigate the long-term dynamical evolution of a nucleated dwarf galaxy embedded in a massive dark matter halo under the strong tidal field of the Galaxy. The dwarf galaxy is assumed to have a stellar nucleus (or a nuclear star cluster) that could be the progenitor for NGC 1851. We find that although the dark matter halo and the stellar envelope of the host dwarf of NGC 1851 can be almost completely stripped during its orbital evolution around the Galaxy, a minor fraction of stars in the dwarf can remain trapped by the gravitational field of the nucleus. The stripped nucleus can be observed as NGC 1851 with no/little dark matter whereas stars around the nucleus can be observed as a diffuse stellar halo around NGC 1851. The simulated stellar halo has a symmetric distribution with a power-law density slope of ~ -2 and shows no tidal tails within ~200pc from NGC 1851. We show that two GCs can merge with each other to form a new nuclear GC embedded in field stars owing to the low stellar velocity dispersion of the host dwarf. This result makes no assumption on the ages and/or chemical abundances of the two merging GCs. Thus the observed stellar halo and characteristic multiple stellar populations in NGC 1851 suggest that NGC 1851 could have formed initially in the central region of an ancient dwarf galaxy.; Comment: 15 pages...