bluuebunny/crossref_metadata_2025_split huggingface dataset:
TP-AGB stars in population synthesis models
Authors: Marigo Paola , Girardi Léo , Bressan Alessandro , Aringer Bernhard , Gullieuszik Marco , Held Enrico V. , Groenewegen Martin A.T. , Silva Laura , Granato Gian Luigi 
Published: April 2010

AbstractIn spite of its relevance, the Thermally Pulsing Asymptotic Giant Branch (TP-AGB) phase is one of the most uncertain phases of stellar evolution, and a major source of disagreement between the results of different population synthesis models of galaxies. I will briefly review the existing literature on the subject, and recall the basic prescriptions that have been used to fix the contribution of TP-AGB stars to the integrated light of stellar populations. The simplicity of these prescriptions greatly contrasts with the richness of details provided by present-day databases of AGB stars in the Magellanic Clouds, which are now being extended to other nearby galaxies. I will present the first results of an ongoing study aimed at simulating photometry, chemistry, pulsation, mass loss, dust properties of AGB star populations in resolved and un-resolved galaxies. We test our predictions against observations from various surveys of the Magellanic Clouds (DENIS, 2MASS, OGLE, MACHO, Spitzer, and AKARI). I will discuss the implications and outline the plan of future developments.
Testing evolutionary synthesis models: Empirical feedback to model makers
Authors: Cid Fernandes Roberto , Delgado Rosa M. González 
Published: April 2010

AbstractIntegrated spectra of star clusters are the best test beds for predictions of evolutionary synthesis models. We present spectral fits of star cluster using a variety of recent models. All models allow good spectral fits, but newer ones tend to be better. Ages estimated through spectral fits are not strongly model dependent, but metallicities can differ a lot from one model to another. For some clusters, multi-population fits suggest a combination of very old (1010 yr) and very young (< 108) populations, an artifact of the lack of old and blue stars in the models.
Nebular abundances in galaxies: Beware of biases
Authors: Stasińska Grażyna 
Published: April 2010

AbstractThe derivation of nebular abundances in galaxies using strong line methods is simple and quick. Various indices have been designed and calibrated for this purpose, and they are widely used. However, abundances derived with such methods may be significantly biased, if the objects under study have different structural properties (hardness of the ionizing radiation field, morphology of the nebulae) than those used to calibrate the methods. Special caution is required when comparing the metallicities of different samples, like, for example, blue compact galaxies and other emission line dwarf galaxies, or samples at different redshifts.
Revealing infrared populations of nearby galaxies using the Spitzer Space Telescope
Authors: Matsuura Mikako 
Published: April 2010

AbstractDue to their brightness in infrared, asymptotic giant branch (AGB) stars are in important evolutionary stage to be understood at this wavelength. In particular, in next decades, when the infrared optimised telescopes, such as the JWST and the ELT are in operation, it will be essential to include the AGB phase more precisely into the population synthesis models. However, the AGB phase is still one of the remaining major problems in the stellar evolution. This is because the AGB stellar evolution is strongly affected by the mass-loss process from the stars. It is important to describe mass loss more accurately so as to incorporate it into stellar evolutionary models. Recent observations using the Spitzer Space Telescope (SST) enabled us to make a significant progress in understanding the mass loss from AGB stars. Moreover, the SST large surveys contributed to our understanding of the role of AGB stars in chemical enrichment process in galaxies. Here we present the summary of our recent progress.
Metallicity Mapping with gri Photometry: The Virgo Overdensity and the Halos of the Galaxy
Authors: Beers Timothy C. , An Deokkeun , Johnson Jennifer A. , Pinsonneault Marc H. , Terndrup Donald M. , Delahaye Franck , Lee Young Sun , Masseron Thomas , Carollo Daniela , Yanny Brian 
Published: April 2010

AbstractWe describe the methodology required for estimation of photometric estimates of metallicity based on the SDSS gri passbands, which can be used to probe the properties of main-sequence stars beyond ~10 kpc, complementing studies of nearby stars from more metallicity-sensitive color indices that involve the u passband. As a first application of this approach, we determine photometric metal abundance estimates for individual main-sequence stars in the Virgo Overdensity, which covers almost 1000 deg2 on the sky, based on a calibration of the metallicity sensitivity of stellar isochrones in the gri filter passbands using field stars with well-determined spectroscopic metal abundances. Despite the low precision of the method for individual stars, internal errors of σ[Fe/H]~0.1 dex can be achieved for bulk stellar populations. The global metal abundance of the Virgo Overdensity determined in this way is 〈[Fe/H]〉 = −2.0±0.1 (internal) ±0.5 (systematic), from photometric measurements of 0.7 million stars with heliocentric distances from ~10 kpc to ~20 kpc. A preliminary metallicity map, based on results for 2.9 million stars in the northern SDSS DR-7 footprint, exhibits a shift to lower metallicities as one proceeds from the inner- to the outer-halo population, consistent with recent interpretation of the kinematics of local samples of stars with spectroscopically available metallicity estimates and full space motions.
The current status on the UV upturn
Authors: Yi Sukyoung K. 
Published: April 2010

AbstractThe UV upturn phenomenon found in giant elliptical galaxies through space observations has been a mystery. Recent GALEX observations have revealed new facts. The most notable is the rarity of UV upturn galaxies. Unlike previous beliefs, UV upturn is found only in less than 10 percent of giant ellitpical galaxies. Another notable finding is that the UV flux has been increasing for the last couple of billion years. This is consistent with the theoretical predictions that suggest hot horizontal branch stars are the main UV sources. Remaining theoretical and observational issues on this topic can be found in another recent review of mine (Yi 2008).
Dissecting the Formation Histories of Galaxies with Stellar Populations Models
Authors: Labbé Ivo 
Published: April 2010

AbstractHow did galaxies evolve from primordial fluctuations to the well-ordered but diverse population of disk and elliptical galaxies that we observe today? Stellar populations synthesis models have become a crucial tool in addressing this question by helping us to interpret the spectral energy distributions of present-day galaxies and their high redshift progenitors in terms of fundamental characteristics such as stellar mass and age. I will review our current knowledge on the evolution of stellar populations in early- and late type galaxies atz< 1 and the tantalizing – but incomplete – view of the stellar populations in galaxies at 1 <z< 3, during the global peak of star formation. Despite great progress, many fundamental questions remain: what processes trigger episodes of galaxy-scale star formation and what quenches them? To what degree does the star formation history of galaxies depend on the merger history, (halo) mass, or local environment? I will discuss some of the challenges posed in interpreting current data and what improved results might be expected from new observational facilities in the near- and more distant future.
Probing the stellar population of seyfert galaxies: a near infrared perspective
Authors: Riffel Rogério , Pastoriza Miriani G. , Rodríguez-Ardila Alberto , Bonatto Charles 
Published: April 2010

AbstractWe employ IRTF SpeX NIR (0.8–2.4μm) spectra to investigate the stellar population (SP), active galactic nuclei (AGN), featureless continuum (FC) and hot dust properties in 9 Sy 1 and 15 Sy 2 galaxies. Both the starlight code and the hot dust as an additional base element were used for the first time in this spectral range. Our synthesis shows significant differences between Sy 1 and Sy 2 galaxies: the hot dust component is required to fit the K-band spectra of ~90% of the Sy 1 galaxies, and only of ~25% of the Sy 2; about 50% of the Sy 2 galaxies require an FC component contribution ≳20%; this fraction increases to about 60% in the Sy 1. In about 50% of the Sy2, the combined FC and young components contribute with more than 20%, while this occurs in 90% of the Sy1, suggesting recent star formation in the central region. The central few hundred parsecs of our galaxy sample contain a substantial fraction of intermediate-age SPs with a mean metallicity near solar. Our SP synthesis confirms that the 1.1μm CN band can be used as a tracer of intermediate-age stellar populations.
DEEP, AEGIS, & CATS - Pathfinding Surveys to the Next Generation of Distant Galaxy Stellar Population Research
Authors: Koo David C. ,   DEEP2,   AEGIS,   CATS Teams
Published: April 2010

AbstractDEEP, AEGIS, and CATS are examples of spectroscopic, multiwavelength, and adaptive optics surveys, respectively, that are pushing the frontiers of stellar population studies of distant galaxies. Together, these surveys affirm the unprecedented richness of high quality information that can already be gathered using today's generation of ground and space telescopes. We highlight several results in extracting the stellar and dynamical masses, chemical abundances, ages, and frequency of galactic winds for galaxies at redshifts up to z ~ 1.4.
What have we learned from large spectroscopic surveys?
Authors: Blanton Michael R. 
Published: April 2010

AbstractAn essential use of stellar population synthesis methods is to interpret the observations of galaxies, to infer their star-formation and assembly histories. I describe here some of the uses of these techniques over the past few years, primarily in the context of local galaxy redshift surveys. For this purpose, such surveys have both advantages and disadvantages relative to higher signal-to-noise but smaller studies, which I discuss. After discussing general issues, I describe how the substantial model uncertainties impact the analysis of galaxy spectra. Then, I discuss the special case of elliptical galaxies, arguing that investigators have made interesting discoveries even in the absence of perfect (or even good) models. I then describe the desiderata for massive higher redshift surveys and the trade-offs that must be made between cosmological and galaxy-focused science, in qualitative terms.
The Promise of Multiwavelength and IFU Observations
Authors: Kennicutt Robert C. , Hao Cai-Na , Johnson Benjamin D. , Rosales-Ortega Fabian , Díaz Angeles , Pasquale Anna , Sánchez Sebastian F. 
Published: April 2010

AbstractMany of the advances of the last decade in this subject have been the result of large spectroscopic surveys of galaxies on the one hand, and multi-wavelength surveys of galaxies on the other. This talk highlights applications that exploit a combination of spectroscopic and multi-wavelength diagnostics. Most applications to date have been based on spatially integrated measurements of galaxies, but the introduction of wide-field integral field spectrometers promises to extend ths approach to spatially-resolved analyses of galaxies.
Building the red sequence through gas-rich major mergers
Authors: Wild Vivienne , Walcher C. Jakob , Johansson Peter H. 
Published: April 2010

AbstractUnderstanding the details of how the red sequence is built is a key question in galaxy evolution. What are the relative roles of gas-rich vs. dry mergers, major vs. minor mergers or galaxy mergers vs. gas accretion? In a recent paper (Wild et al. 2009), we compare hydrodynamic simulations with observations to show how gas-rich major mergers result in galaxies with strong post-starburst spectral features, a population of galaxies easily identified in the real Universe using optical spectra. Using spectra from the VVDS deep survey with <z> = 0.7, and a principal component analysis technique to provide indices with high enough SNR, we find that 40% of the mass flux onto the red-sequence could enter through a strong post-starburst phase, and thus through gas-rich major mergers. The deeper samples provided by next generation galaxy redshift surveys will allow us to observe the primary physical processes responsible for the shut-down in starformation and build-up of the red sequence.
The Slow Growth of Massive Galaxies in Rapidly Growing Dark Matter Halos
Authors: Brown Michael J. I. ,   the Boötes Field Collaborations
Published: April 2010

AbstractIn cold dark matter cosmologies, the most massive dark matter halos are predicted to undergo rapid growth at z < 1. While there is the expectation that massive galaxies will also rapidly grow via merging, recent observational studies conclude that the stellar masses of the most massive galaxies grow by just ~ 30% at z < 1. We have used the observed space density and clustering of z < 1 red galaxies in Boötes to determine how these galaxies populate dark matter halos. In the most massive dark matter halos, central galaxy stellar mass is proportional to halo mass to the power of a ~1/3 and much of the stellar mass resides within satellite galaxies. As a consequence, the most massive galaxies grow slowly even though they reside within rapidly growing dark matter halos.
Modeling high-redshift galaxies: what can we learn from high and ultra-high resolution hydrodynamical simulations?
Authors: Devriendt J. , Slyz A. , Powell L. , Pichon C. , Teyssier R. 
Published: April 2010

AbstractWe present results from a high resolution cosmological galaxy formation simulation called Mare Nostrum and a ultra-high resimulation of the first 500 million years of a single, Milky Way (MW) sized galaxy. Using the cosmological run, we measure UV luminosity functions and assess their sensitivity to both cosmological parameters and dust extinction. We find remarkably good agreement with the existing data over the redshift range 4 < z < 7 provided we adopt the favoured cosmology (WMAP 5 year parameters) and a self-consistent treatment of the dust. Cranking up the resolution, we then study in detail a z = 9 protogalaxy sitting at the intersection of cold gas filaments. This high-z MW progenitor grows a dense, rapidly spinning, thin disk which undergoes gravitational fragmention. Star formation in the resulting gas clumps rapidly turns them into globular clusters. A far reaching galactic wind develops, co-powered by the protogalaxy and its cohort of smaller companions populating the filaments. Despite such an impressive blow out, the smooth filamentary material is hardly affected at these redshifts.
Testing star formation rate indicators using galaxy merger simulations and radiative transfer
Authors: Hayward Christopher C. , Jonsson Patrik , Noeske Kai , Wuyts Stijn , Cox T. J. , Narayanan Desika , Groves Brent , Hernquist Lars 
Published: April 2010

AbstractWe discuss our ongoing project analyzing N-body/smoothed-particle hydrodynamics simulations of isolated and merging galaxies, performed using GADGET-2 (Springel 2005), with the 3-D adaptive grid, polychromatic Monte Carlo radiative transfer code SUNRISE (Jonsson 2006). We apply commonly used UV, optical, and IR star formation rate (SFR) indicators to the integrated spectral energy distributions (SEDs) of the simulated galaxies in order to determine how well the SFR indicators recover the instantaneous SFR in the simulations. The models underlying each SFR indicator must necessarily make assumptions about physical properties of the galaxies, e.g., the star formation history (SFH), whereas all such properties are known in the simulations. This enables us to test and compare SFR indicators in a way that is complementary to observational studies. We present one preliminary result of interest: even after correcting the Hα luminosity for dust using the Calzetti et al. (2000) attenuation law the SFR is significantly underestimated for simulated galaxies with SFR ≳ 10 M⊙ yr−1.
The Shining Future of UV Spectral Synthesis
Authors: Pellerin Anne , Finkelstein Steven L. 
Published: April 2010

AbstractWith the coming generation of instruments and telescopes capable of spectroscopy of high redshift galaxies, the spectral synthesis technique in the rest-frame UV and Far-UV range will become one of a few number of tools remaining to study their young stellar populations in detail. The rest-frame UV lines and continuum of high redshift galaxies, observed with visible and infrared telescopes on Earth, can be used for accurate line profile fitting such as Pvλλ1118, 1128, Ciiiλ1176, and Civλ1550. These lines are very precise diagnostic tools to estimate ages, metallicities, and masses of stellar populations.Here we discuss the potential for spectral synthesis of rest-frame UV spectra obtained at the Keck telescope. As an example, we study the 8 o'clock arc, a lensed galaxy at z=2.7322. We show that the poor spectral type coverage of the actual UV empirical spectral libraries limits the age and metallicity diagnostic. In order to improve our knowledge of high redshift galaxies using spectral synthesis, UV stellar libraries need to be extended to obtain accurate age, metallicity, and mass estimates likely to be occuring in young stellar populations observed in the early universe.
Concluding Remarks: Recent Achievements and Future Challenges in Stellar Population Studies
Authors: Charlot Stephane 
Published: April 2010

AbstractTo conclude this exciting conference on Stellar Populations: Planning for the Next Decade, we have sacrificed the traditional ‘conference summary’ for an opinion poll among all invited speakers on two issues: the most important achievements in the field of stellar populations over the past few years; and the most important challenges for the coming decade. The answers to this poll were remarkably uniform, indicating that the field of stellar populations has a clear future in the era when several new major research facilities are coming online.
The Effects of Galactic Winds on the Chemical Evolution of Baryons
Authors: De Rossi María E. , Tissera Patricia B. 
Published: April 2010

AbstractDuring the last decade, the development of more sophisticated surveys allows the exploration of the chemical enrichment of galaxies and their environment at different cosmic times. In this context, it has been suggested that galactic winds play a fundamental role in the regulation of the star formation and the transportation of metals outside the galaxies. In this work, we study the influence of Supernovae winds in the chemical evolution of galaxies and the intergalactic medium by employing cosmological numerical simulations within a hierarchical Universe. We focus on the origin and evolution of the mass-metallicity relation (MZR).
The Tully-Fisher Relation in Numerical Simulations of Structure Formation
Authors: De Rossi María E. , Tissera Patricia B. , Pedrosa Susana E. 
Published: April 2010

AbstractThe Tully-Fisher Relation (TFR) is of fundamental importance for galaxy formation as it provides information about the relation between the baryonic content of galaxies and the depth of their dark halos potential wells. In recent years, it has been possible to study this relation at different redshifts. However, there are still controversies about its origin and evolution. In this work, we try to address the origin of the Tully-Fisher Relation by employing cosmological hydrodynamical simulations.
A near-infrared view of AGB stars in nearby dwarf galaxies
Authors: Gullieuszik M. , Held E. V. , Girardi L. , Rizzi L. , Marigo P. , Saviane I. , Momany Y. 
Published: April 2010

AbstractAs part of our near-infrared photometric survey of nearby dwarf galaxies, we present recent results for Leo I and Leo II dwarf spheroidal galaxies. We selected O- and C-rich AGB stellar populations using two-color diagrams and compared their luminosity functions and star counts with the predictions of the most recent AGB theoretical models.
Mid-UV Spectral Diagnostics
Authors: Heap Sara R. , Lindler Don 
Published: April 2010

AbstractThe mid-ultraviolet is an important diagnostic region due to its sensitivity to the hottest stars of a stellar population. Sources of mid-UV flux include main sequence turn-off stars, the basic clocks of stellar evolution, and also blue horizontal branch stars and blue stragglers. We describe some observed trends in mid-UV colors and spectral indices.
The star formation history of the Fornax dwarf spheroidal galaxy
Authors: Held Enrico V. , Tolstoy Eline , Rizzi Luca , Cesetti Mary , Cole Andrew A. , Battaglia Giuseppina , Da Costa Gary S. , Gullieuszik Marco , Mateo Mario , Olszewski Edward W. , Walker Matthew G. 
Published: April 2010

AbstractWe present the first results of a comprehensive HST study of the star-formation history of Fornax dSph, based on WFPC2 imaging of 7 Fornax fields. Our observations reach the oldest main-sequence turnoffs, allowing us to address fundamental questions of dwarf galaxy evolution, such as the spatial variations in the stellar content, and whether the old stellar population is made up of stars formed in a very early burst or the result of a more continuous star formation.
On the parameterization of single and binary stars
Authors: Malkov O. , Sichevskij S. , Kovaleva D. , Myakutin V. 
Published: April 2010

AbstractMany astrophysical problems in the theory of formation and evolution of stars and stellar groups require knowledge of the mass or age of individual stars. Stellar masses and ages are not directly observable parameters, and most of the methods used to determine them are based on the calibrating relations obtained from observations or from theoretical considerations. In most cases, the mass-luminosity relation, based on the masses of approximately two hundred well-studied binaries, is the only way to estimate the mass of single stars. Unfortunately, the statistical nature of the mass-luminosity relation means that the stellar masses determined with it may only be considered as approximate. The establishment of methods for estimating stellar masses and ages of stars with accuracy comparable to direct methods remains a challenging task. This work proposes a way to use the location of a star in the HR diagram to estimate its mass and age based on modern stellar models. The method is based on the geometric similarity of evolutionary tracks for the stars at the same evolutionary stage. To examine the proposed approach and involved assumptions, it has been applied to various test data sets.
Spiral triggering of star formation in normal galaxies
Authors: Martínez-García Eric E. , González-Lópezlira Rosa Amelia , Bruzual-A. Gustavo 
Published: April 2010

AbstractWe present results for 13 spiral galaxies from a sample of 31, where we have used the method developed by González & Graham 1996, to search for and analyze azimuthal color gradients across spiral arms (see figure 1 in Martínez-García et al. 2009). A total of 23 regions were analyzed in the spiral disks. Ten of the galaxies present regions that match theoretical predictions.
The nature of the LINER in the galaxy NGC 404
Authors: Menezes Roberto B. , Steiner João E. , Ricci Tiago V. , Oliveira Alexandre S. 
Published: April 2010

AbstractNGC 404, at a distance of 3.4 Mpc, is the nearest S0 galaxy. This galaxy harbors a LINER; however, since the spectrum does not show a broad Hα emission, it is not certain that this LINER is a low luminosity AGN and its nature is still an open question. HST observations show the existence of stellar populations with an age of 3 × 108 years in the galactic bulge and with an age of 6–15 × 109 years in the galactic disk. In this work, we present an analysis of the data cube of NGC 404 obtained with the IFU (Integral Field Unity) of the GMOS (Gemini Multi-Object Spectrograph) on the Gemini North telescope.