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## ‣ Chemical similarities between Galactic bulge and local thick disk red giant stars

MELENDEZ, J.; ASPLUND, M.; ALVES-BRITO, A.; CUNHA, K.; BARBUY, B.; BESSELL, M. S.; CHIAPPINI, C.; FREEMAN, K. C.; RAMIREZ, I.; SMITH, V. V.; YONG, D.
Fonte: EDP SCIENCES S A Publicador: EDP SCIENCES S A
Tipo: Artigo de Revista Científica
Português
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Context. The evolution of the Milky Way bulge and its relationship with the other Galactic populations is still poorly understood. The bulge has been suggested to be either a merger-driven classical bulge or the product of a dynamical instability of the inner disk. Aims. To probe the star formation history, the initial mass function and stellar nucleosynthesis of the bulge, we performed an elemental abundance analysis of bulge red giant stars. We also completed an identical study of local thin disk, thick disk and halo giants to establish the chemical differences and similarities between the various populations. Methods. High-resolution infrared spectra of 19 bulge giants and 49 comparison giants in the solar neighborhood were acquired with Gemini/Phoenix. All stars have similar stellar parameters but cover a broad range in metallicity. A standard 1D local thermodynamic equilibrium analysis yielded the abundances of C, N, O and Fe. A homogeneous and differential analysis of the bulge, halo, thin disk and thick disk stars ensured that systematic errors were minimized. Results. We confirm the well-established differences for [O/Fe] (at a given metallicity) between the local thin and thick disks. For the elements investigated, we find no chemical distinction between the bulge and the local thick disk...

## ‣ A FIRST CONSTRAINT ON THE THICK DISK SCALE LENGTH: DIFFERENTIAL RADIAL ABUNDANCES IN K GIANTS AT GALACTOCENTRIC RADII 4, 8, AND 12 kpc

BENSBY, T.; ALVES-BRITO, A.; OEY, M. S.; YONG, D.; MELENDEZ, J.
Fonte: IOP PUBLISHING LTD Publicador: IOP PUBLISHING LTD
Tipo: Artigo de Revista Científica
Português
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Based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan telescopes, we present detailed elemental abundances for 20 red giant stars in the outer Galactic disk, located at Galactocentric distances between 9 and 13 kpc. The outer disk sample is complemented with samples of red giants from the inner Galactic disk and the solar neighborhood, analyzed using identical methods. For Galactocentric distances beyond 10 kpc, we only find chemical patterns associated with the local thin disk, even for stars far above the Galactic plane. Our results show that the relative densities of the thick and thin disks are dramatically different from the solar neighborhood, and we therefore suggest that the radial scale length of the thick disk is much shorter than that of the thin disk. We make a first estimate of the thick disk scale length of L(thick) = 2.0 kpc, assuming L(thin) = 3.8 kpc for the thin disk. We suggest that radial migration may explain the lack of radial age, metallicity, and abundance gradients in the thick disk, possibly also explaining the link between the thick disk and the metal-poor bulge.; Swedish Research Council[621-2009-3911]; National Science Foundation NSF[AST-0448900]; FONDECYT[3100013]; FAPESP[2010/50930-6]; USP (Novos Docentes); CNPq (Bolsa de produtividade)

## ‣ PLANETARY NEBULAE IN THE INNER MILKY WAY II: THE BULGE-DISK TRANSITION

CAVICHIA, O.; COSTA, R. D. D.; MACIEL, W. J.
Fonte: UNIV NACIONAL AUTONOMA MEXICO, INST DE ASTRONOMIA Publicador: UNIV NACIONAL AUTONOMA MEXICO, INST DE ASTRONOMIA
Tipo: Artigo de Revista Científica
Português
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In this work, a sample of planetary nebulae located in the inner-disk and bulge of the Galaxy is used in order to find the galactocentric distance which better separates these two populations, from the point of view of abundances. Statistical distance scales are used to study the distribution of abundances across the disk-bulge interface. A Kolmogorov-Smirnov test is used to find the distance at which the chemical properties of these regions better separate. The results of the statistical analysis indicate that, on the average, the inner population has lower abundances than the outer. Additionally, for the a-element abundances, the inner population does not follow the disk radial gradient towards the galactic center. Based on our results, we suggest a bulge-disk interface at 1.5 kpc, marking the transition between the bulge and inner-disk of the Galaxy as defined by the intermediate mass population.; FAPESP[05/03194-4]; FAPESP[07/07704-2]; CNPq

## ‣ Elemental abundance ratios in stars of the outer galactic disk. IV. A new sample of open clusters

Yong, D.; Carney, B.W.; Friel, E.D.
Fonte: The American Astronomical Society Publicador: The American Astronomical Society
Tipo: Artigo de Revista Científica
Português
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We present radial velocities and chemical abundances for nine stars in the old, distant open clusters Be18, Be21, Be22, Be32, and PWM4. For Be18 and PWM4, these are the first chemical abundance measurements. Combining our data with literature results produces a compilation of some 68 chemical abundance measurements in 49 unique clusters. For this combined sample, we study the chemical abundances of open clusters as a function of distance, age, and metallicity. We confirm that the metallicity gradient in the outer disk is flatter than the gradient in the vicinity of the solar neighborhood. We also confirm that the open clusters in the outer disk are metal-poor with enhancements in the ratios [$alpha$/Fe] and perhaps [Eu/Fe]. All elements show negligible or small trends between [X/Fe] and distance (<0.02dexkpc$^{-1}$), but for some elements, there is a hint that the local (R$_{GC}$< 13kpc) and distant (R$_{GC}$> 13kpc) samples may have different trends with distance. There is no evidence for significant abundance trends versus age (<0.04dex Gyr$^{-1}$). We measure the linear relation between [X/Fe] and metallicity, [Fe/H], and find that the scatter about the mean trend is comparable to the measurement uncertainties. Comparison with solar neighborhood field giants shows that the open clusters share similar abundance ratios [X/Fe] at a given metallicity. While the flattening of the metallicity gradient and enhanced [$alpha$/Fe] ratios in the outer disk suggest a chemical enrichment history different from that of the solar neighborhood...

## ‣ Chemical similarities between Galactic bulge and local thick disk red giants: O, Na, Mg, Al, Si, Ca, and Ti

ALVES-BRITO, A.; MELENDEZ, J.; ASPLUND, M.; RAMIREZ, I.; YONG, D.
Fonte: EDP SCIENCES S A Publicador: EDP SCIENCES S A
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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Context. The formation and evolution of the Galactic bulge and its relationship with the other Galactic populations is still poorly understood. Aims. To establish the chemical differences and similarities between the bulge and other stellar populations, we performed an elemental abundance analysis of alpha- (O, Mg, Si, Ca, and Ti) and Z-odd (Na and Al) elements of red giant stars in the bulge as well as of local thin disk, thick disk and halo giants. Methods. We use high-resolution optical spectra of 25 bulge giants in Baade's window and 55 comparison giants (4 halo, 29 thin disk and 22 thick disk giants) in the solar neighborhood. All stars have similar stellar parameters but cover a broad range in metallicity (-1.5 < [Fe/H] < +0.5). A standard 1D local thermodynamic equilibrium analysis using both Kurucz and MARCS models yielded the abundances of O, Na, Mg, Al, Si, Ca, Ti and Fe. Our homogeneous and differential analysis of the Galactic stellar populations ensured that systematic errors were minimized. Results. We confirm the well-established differences for [alpha/Fe] at a given metallicity between the local thin and thick disks. For all the elements investigated, we find no chemical distinction between the bulge and the local thick disk...

## ‣ Populações e evolução do bojo e região central da Galáxia; Populations and the evolution of the bulge and central region of the Galaxy

Moraes, Oscar Cavichia de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
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O presente trabalho propõe uma abordagem abrangente para descrever a evolução da região central da Via Láctea, compreendendo-se aí o bojo, a barra e as interfaces dos mesmos com o limite interno do disco e com a região central do halo. Pretende-se investigar as propriedades químicas e cinemáticas destas estruturas, que são interconectadas, com o objetivo de separá-las e aplicar os resultados daí obtidos a um modelo de formação e evolução do bojo e da região interna do disco que descreva simultaneamente distintos aspectos da evolução da região central da Galáxia. Na primeira parte do trabalho, uma amostra de nebulosas planetárias (NPs) localizadas no disco interno e no bojo da Galáxia é utilizada para encontrar a distância galactocêntrica que melhor separa estas duas populações, do ponto de vista das abundâncias. Foram utilizadas escalas de distâncias estatísticas para o estudo da distribuição das abundâncias na interface bojo-disco. A aplicação do teste Kolmogorov-Smirnov mostrou que, em média, a população interna não segue o gradiente radial de abundâncias do disco na direção do centro galáctico. Baseado neste estudo, propõe-se uma distância galactocêntrica de 1.5 kpc para definir a interface bojo-disco. Na segunda parte do trabalho...

## ‣ ATLASGAL – The APEX telescope large area survey of the galaxy at 870 μm

Bronfman Aguiló, Leonardo Jaime; Contreras, Y.
Tipo: Artículo de revista
Português
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Context. Thanks to its excellent 5100 m high site in Chajnantor, the Atacama Pathfinder Experiment (APEX) systematically explores the southern sky at submillimeter wavelengths, in both continuum and spectral line emission. Studying continuum emission from interstellar dust is essential to locating the highest density regions in the interstellar medium, and deriving their masses, column densities, density structures, and large-scale morphologies. In particular, the early stages of (massive) star formation remain poorly understood, mainly because only small samples of high-mass proto-stellar or young stellar objects have been studied in detail so far. Aims. Our goal is to produce a large-scale, systematic database of massive pre- and proto-stellar clumps in the Galaxy, to understand how and under what conditions star formation takes place. Only a systematic survey of the Galactic Plane can provide the statistical basis for unbiased studies. A well characterized sample of Galactic star-forming sites will deliver an evolutionary sequence and a mass function of high-mass, star-forming clumps. This systematic survey at submillimeter wavelengths also represents a preparatory work for Herschel and ALMA. Methods. The APEX telescope is ideally located to observe the inner Milky Way. The Large APEX Bolometer Camera (LABOCA) is a 295-element bolometer array observing at 870 μm...

## ‣ Elemental Abundance Ratios in Stars of the Outer Galactic Disk. II. Field Red Giants

Carney, B W; Yong, David; Teixera de Almeida, M.L.; Seitzer, P
Fonte: University of Chicago Press Publicador: University of Chicago Press
Tipo: Artigo de Revista Científica
Português
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We summarize a selection process to identify red giants in the direction of the southern warp of the Galactic disk, employing VI C photometry and multiobject spectroscopy. We also present results from follow-up high-resolution, high signal-to-noise echell

## ‣ Elemental Abundance Ratios in Stars of the Outer Galactic Disk. III. Cepheids

Yong, David; Carney, B W; Teixera de Almeida, M.L.; Pohl, B.L.
Fonte: University of Chicago Press Publicador: University of Chicago Press
Tipo: Artigo de Revista Científica
Português
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We present metallicities, [Fe/H], and elemental abundance ratios, [X/Fe], for a sample of 24 Cepheids in the outer Galactic disk based on high-resolution echelle spectra. The sample members have galactocentric distances covering 12 kpc ≤ RGC ≤ 17.2 kp

## ‣ Stochastic 2-D Models of Galaxy Disk Evolution. The Galaxy M33

Tipo: Artigo de Revista Científica
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We have developed a fast numerical 2-D model of galaxy disk evolution (resolved along the galaxy radius and azimuth) by adopting a scheme of parameterized stochastic self-propagating star formation. We explore the parameter space of the model and demonstrate its capability to reproduce 1-D radial profiles of the galaxy M33: gas surface density, surface brightness in the i and GALEX FUV passbands, and metallicity.; Comment: 12 pages, 5 figures

## ‣ Mass-to-light ratios from the fundamental plane of spiral galaxy disks

Graham, Alister W.
Tipo: Artigo de Revista Científica
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The best-fitting 2-dimensional plane within the 3-dimensional space of spiral galaxy disk observables (rotational velocity v_{rot}, central disk surface brightness \mu_0 = -2.5log I_0, and disk scale-length h) has been constructed. Applying a three-dimensional bisector method of regression analysis to a sample of ~100 spiral galaxy disks that span more than four mag arcsec^{-2} in central disk surface brightness yields v_{rot} ~ I_0^{0.50+/-0.05}h^{0.77+/-0.07} (B-band) and v_{rot} ~ I_0^{0.43+/-0.04}h^{0.69+/-0.07} (R-band). Contrary to popular belief, these results suggest that in the B-band, the dynamical mass-to- light ratio (within 4 disk scale-lengths) is largely independent of surface brightness, varying as I_0^{0.00+/-0.10}h^{0.54+/-0.14}. Consistent results were obtained when the expanse of the analysis was truncated by excluding the low surface brightness galaxies. Previous claims that M/L_B varies with I_0^{-1/2} are shown to be misleading and/or due to galaxy selection effects. Not all low-surface-brightness disk galaxies are dark matter dominated. The situation is however different in the near-infrared where L_{K'} \~ v^4 and M/L_{K'} is shown to vary as I_0^{-1/2}. Theoretical studies of spiral galaxy disks should not assume a constant M/L ratio within any given passband. The B-band dynamical mass-to-light ratio (within 4 disk scale-lengths) has no obvious correlation with (B-R) disk colour...

## ‣ Comparing the Evolution of the Galaxy Disk Sizes with CDM Models: The Hubble Deep Field

Giallongo, E.; Menci, N.; Poli, F.; D'Odorico, S.; Fontana, A.
Tipo: Artigo de Revista Científica
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The intrinsic sizes of the field galaxies with I<26 in the Hubble and ESO-NTT Deep Fields are shown as a function of their redshifts and absolute magnitudes using photometric redshifts derived from the multicolor catalogs and are compared with the CDM predictions. Extending to lower luminosities and to higher z our previous analysis performed on the NTT field alone, we find that the distribution of the galaxy disk sizes at different cosmic epochs is within the range predicted by typical CDM models. However, the observed size distribution of faint (M_B>-19) galaxies is skewed with respect to the CDM predictions and an excess of small-size disks (R_d<2 kpc) is already present at z~ 0.5. The excess persists up to z~3 and involves brighter galaxies . Such an excess may be reduced if luminosity-dependent effects, like starburst activity in interacting galaxies, are included in the physical mechanisms governing the star formation history in CDM models.; Comment: 9 pages, 3 figures, ApJ Letters in press

## ‣ The Disk and Dark Halo Mass of the Barred Galaxy NGC 4123. II. Fluid-Dynamical Models

Weiner, Benjamin J.; Sellwood, J. A.; Williams, T. B.
Tipo: Artigo de Revista Científica
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We report a dynamical determination of the separate contributions of disk and dark halo masses to the rotation curve of a spiral galaxy. We use fluid-dynamical models of gas flow in the barred galaxy NGC 4123 to constrain the dynamical properties of the galaxy: disk M/L, bar pattern speed, and the central density and scale radius of the dark halo. We derive a realistic barred potential directly from the light distribution. For each model we assume a value of the stellar M/L and a bar pattern speed Omega_p and add a dark halo to fit the rotation curve. We then compute the gas flow velocities with a 2-D gas dynamical code, and compare the model flow patterns to a 2-D velocity field derived from Fabry-Perot observations. The strong shocks and non-circular motions in the observed gas flow require a high stellar M/L and a fast-rotating bar. Models with I-band disk M/L of 2.0 -- 2.5 h_75, or 80 -- 100% of the maximum disk value, are highly favored. The corotation radius of the bar must be <= 1.5 times the bar semi-major axis. These results contradict some recent claimed universal'' galaxy disk/halo relations, since NGC 4123 is of modest size (rotation curve maximum 145 km/sec, and V_flat = 130 km/sec) yet is quite disk-dominated. The dark halo of NGC 4123 is less concentrated than favored by current models of dark halos based on cosmological simulations. Since some 30% of bright disk galaxies are strongly barred and have dust lanes indicating shock morphology similar to that of NGC 4123...

## ‣ Astrometric Microlensing of Distant Sources due to the Stars in the Galaxy

Honma, Mareki; Kurayama, Tomoharu
Tipo: Artigo de Revista Científica
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We investigate properties of astrometric microlensing of distant sources (such as QSOs and radio galaxies) caused by stars in the Galaxy, mainly focusing on application to the VERA (VLBI Exploration of Radio Astrometry) project. Assuming typical parameters for the Galaxy disk and bulge, we show that the maximum optical depth for astrometric shift of 10 micro-arcsec level is 8.9x10^{-2} for QSO-disk lensing case and 3.8x10^{-2} for QSO-bulge lensing case. We also find that the maximum optical depth for QSO-disk lensing is larger by an order of magnitude than that for disk-disk or bulge-disk lensing case (assuming a typical source distance of 8 to 10 kpc). In addition to optical depth, we also calculate the event rate and find that the maximum event rate for QSO-disk lensing case is 1.2x10^{-2} event per year, which is about 30 times greater than that for disk-disk lensing case. This high event rate implies that if one monitors 10 QSOs behind the Galactic center region for 10 years, at least one astrometric microlensing event should be detected. Therefore, monitoring distant radio sources with VERA can be a new tool to study astrometric microlensing caused by stars in the Galaxy. We discuss the implications of astrometric microlensing for VERA by focusing on estimating the lens mass...

## ‣ Stochastic 2-D galaxy disk evolution models. Resolved stellar populations in the galaxy M33

Mineikis, T.; Vansevičius, V.
Tipo: Artigo de Revista Científica
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We improved the stochastic 2-D galaxy disk models (Mineikis & Vansevi\v{c}ius 2014a) by introducing enriched gas outflows from galaxies and synthetic color-magnitude diagrams of stellar populations. To test the models, we use the HST/ACS stellar photometry data in four fields located along the major axis of the galaxy M33 (Williams et al. 2009) and demonstrate the potential of the models to derive 2-D star formation histories in the resolved disk galaxies.; Comment: 8 pages, 4 figures

## ‣ Disk Galaxies in the Outer Local Supercluster: Optical CCD Surface Photometry and Distribution of Galaxy Disk Parameters

Lu, Nanyao Y.
Tipo: Artigo de Revista Científica
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We report new B-band CCD surface photometry on a sample of 76 disk galaxies brighter than B_T = 14.5 mag in the Uppsala General Catalogue of Galaxies, which are confined within a volume located in the outer part of the Local Supercluster. With our earlier published I-band CCD and high S/N-ratio 21cm HI data (Lu et al. 1993), this paper completes our optical surface photometry campaign on this galaxy sample. As an application of this data set, the B-band photometry is used here to illustrate two selection effects which have been somewhat overlooked in the literature, but which may be important in deriving the distribution function of disk central surface brightness (CSB) of disk galaxies from a diameter or/and flux limited sample: a Malmquist-type bias against disk galaxies with small disk scale lengths (DSL) at a given CSB; and a disk inclination dependent selection effect that may, for example, bias toward inclined disks near the threshold of a diameter limited selection if disks are not completely opaque in optical. Taking into consideration these selection effects, we present a method of constructing a volume sampling function and a way to interpret the derived distribution function of CSB and DSL. Application of this method to our galaxy sample implies that if galaxy disks are optically thin...

## ‣ Connecting Galaxy Disk and Extended Halo Gas Kinematics

Kacprzak, G. G.; Churchill, C. W.; Steidel, C. C.; Ceverino, D.; Klypin, A. A.; Murphy, M. T.
Tipo: Artigo de Revista Científica
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We have explored the galaxy disk/extended halo gas kinematic relationship using rotation curves (Keck/ESI) of ten intermediate redshift galaxies which were selected by MgII halo gas absorption observed in quasar spectra. Previous results of six edge-on galaxies, probed along their major axis, suggest that observed halo gas velocities are consistent with extended disk-like halo rotation at galactocentric distances of 25-72 kpc. Using our new sample, we demonstrate that the gas velocities are by and large not consistent with being directly coupled to the galaxy kinematics. Thus, mechanisms other than co-rotation dynamics (i.e., gas inflow, feedback, galaxy-galaxy interactions, etc.) must be invoked to account for the overall observed kinematics of the halo gas. In order to better understand the dynamic interaction of the galaxy/halo/cosmic web environment, we performed similar mock observations of galaxies and gaseous halos in Lambda-CDM cosmological simulations. We discuss an example case of a z=0.92 galaxy with various orientations probing halo gas at a range of positions. The gas dynamics inferred using simulated quasar absorption lines are consistent with observational data.; Comment: To appear in the proceedings of "The Formation and Evolution of Galaxy Disks"...

## ‣ On the asymptotic behavior of the super sonic interstellar gas flow which is made by spiral density wave, propagating in rapidly rotating galaxy disk

Liverts, E. V.
Tipo: Artigo de Revista Científica
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Nonlinear solutions for the large-scale flow of interstellar gas in the presence of a spiral gravitational field have received considerable attention because this model allows to explain a lot of observations for galaxy disks. However this investigations were forced to limit by numerable analysis of the problem because of its nonlinearity. In this paper we wish to carry out the analytical expression which allows us to describe the super sonic nonlinear interstellar gas flow in rapidly rotating galaxy disk which is made by the spiral density wave. One of characteristic parameters of theory is the amplitude of spiral density wave potential corresponding to separatrix, which separates super sonic flows from flows containing the jump from super sonic flows to subsonic. We have defined the dependence of perturbing potential value, under which the galaxy shock wave appeared with respect to the parameters characterizing the gas disk (such as sound speed in gas, disk rotation speed, "spiral design" rotation speed).; Comment: 12 pages Latex, 2 figures, Talk given at The 15-th annual Pushchino meeting "The Modern Problems of Extragalactic Astronomy", Pushchino, May 26 - 29, 1998

## ‣ The Spiral Host Galaxy of the Double Radio Source 0313-192

Keel, William C.; White III, Raymond E.; Owen, Frazer N.; Ledlow, Michael J.
Tipo: Artigo de Revista Científica