bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age and metallicity of star clusters in the Small Magellanic Cloud from integrated spectroscopy
Authors: Dias Bruno , Coelho Paula , Kerber Leandro , Barbuy Beatriz , Idiart Thais 
Published: April 2010

AbstractAnalysis of integrated spectra of star clusters in the Magellanic Clouds can bring important information for studies on the chemical evolution of the Clouds. The aim of the present work is to derive ages and metallicities from integrated spectra of 15 star clusters in the Small Magellanic Cloud (SMC), some of them not studied so far. Making use of a full spectrum fitting technique, we compared the integrated spectra of the sample clusters to three different sets of single stellar population models available in the literature. We derived ages and metallicities for the sample clusters employing the codes STARLIGHT and ULySS. Out of the 15 clusters in our sample, 9 are old/intermediate age clusters and 6 are young clusters. We point out the results for the newly identified as old/intermediate age clusters HW1, NGC 152, Lindsay 3 and 11. We also confirm old ages for NGC 361, NGC 419 and Kron 3, and the oldest well-known SMC cluster NGC 121.
Superdense massive galaxies in the nearby universe
Authors: Ferré-Mateu Anna , Trujillo Ignacio 
Published: April 2010

AbstractAt high-z the most superdense massive galaxies are supposed to be the result of gas-rich mergers resulting in compact remnant (Khochfar & Silk (2006); Naab et al. (2007)). After this, dry mergers are expected to be the mechanism that moves these very massive galaxies towards the current stellar mass size relation. Whitin these merging scenarios, a non-negligible fraction (1-10%) of these galaxies is expected to survive since that epoch retaining their compactness and presenting old stellar populations in the past universe.Using the NYU Value-Added Galaxy Catalog (DR6), we find only a tiny fraction of galaxies (~0.03%) with re ≤ 1.5 kpc and M* ≥ 8x1010M⊙ in the local Universe (z~0.2). Surprisingly, they are relatively young (~2Gyr) and metal rich ([Z/H]~0.2) These results have been published in Trujillo et al. (2009)
M32: Is there an Ancient and Metal-poor Stellar Population?
Authors: Fiorentino Giuliana , Monachesi Antonela , Trager Scott C. , Lauer Tod R. , Saha Abhijit , Mighell Kenneth J. , Freedman Wendy , Dressler Alan , Grillmair Carl , Tolstoy Eline 
Published: April 2010

AbstractWe observed two fields near M32 with the ACS/HRC (Program GO-10572, PI: T. Lauer) on board the Hubble Space Telescope, located at distances of about 1.8' and 5.4' (hereafter F1 and F2, respectively) from the center of M32. To obtain a very detailed and deep color-magnitude diagram (CMD) and to look for short period variability, we obtained time-series imaging of each field in 32-orbit-long exposures using the F435W (B) and F555W (V) filters, spanning a temporal range of 2 days per filter. We focus on our detection of variability on RR Lyrae variable stars, which represents the only way to obtain information about the presence of a very old population (larger than 10 Gyr) in M32 from optical data. Here we present results obtained from the detection of 31 RR Lyrae in these fields: 17 in F1 and 14 in F2. We claim we detected 7+4−3 RR Lyrae variables belonging to M32 in F1 thus indicating the presence of a metal-poor ancient population in M32.
Mass dependent Evolution of Field Early-Type Galaxies Since z=1
Authors: Fritz Alexander , Jørgensen Inger , Schiavon Ricardo P. 
Published: April 2010

AbstractWe present the Fundamental Plane (FP) of field early-type galaxies at 0.5 < z < 1.0. Our project is a continuation of our efforts to understand the formation and evolution of early-type galaxies in different environments. The target galaxies were selected from the comprehensive and homogeneous data set of the Gemini/HST Galaxy Cluster Project. The distant field early-type galaxies follow a steeper FP relation compared to the local FP. The change in the slope of the FP can be interpreted as a mass-dependent evolution. Similar results have been found for cluster early-type galaxies in high redshift galaxy clusters at 0.8 < z <1. Therefore, the slope change of the FP appears to be independent of the environment of the galaxies.
Stellar Populations in Luminous and Ultraluminous Infrared Galaxies
Authors: Delgado R. M. González , Cid Fernandes R. , Pérez E. , Rodríguez-Zaurín J. , Tadhunter C. , Dors O. , Marín V. Muñoz , Villar-Martín M. 
Published: April 2010

AbstractThe goal of this work is to determine the properties of the stellar populations in a sample of LIRGs and ULIRGs. Using the ages as a clock we investigate: a) whether LIRGs-ULIRGs evolve into Radio Galaxies and QSOs; b) whether cool LIRGs-ULIRGs can evolve into warm LIRGs-ULIRGs; c) the merger sequence deduced from the morphological studies is reflected in the properties of the stellar populations. Using evolutionary synthesis models with high spectral resolution stellar libraries we have found that the intermediate age stellar population dominates at optical wavelengths. The stellar population in LIRGs is similar to ULIRGs and ULIRGs-QSOs transition objects.
Spectroscopic Hα and Hγ survey of field Be stars: 2004-2008
Authors: Grundstrom Erika , Aragona Christina , Boyajian Tabetha , Gies Douglas , Amber  , McSwain M. Virginia , Rachel  , Williams Stephen , Wingert David 
Published: April 2010

AbstractMassive O- and B-type stars are “cosmic engines” in the Universe and can be the dominant source of luminosity in a galaxy. Be stars are rapidly rotating B-type stars that lose mass in an equatorial, circumstellar disk (Porter & Rivinius 2003) and cause Balmer and other line emission. Currently, we are unsure as to why these stars rotate so quickly but three scenarios are possible: they may have been born as rapid rotators, spun up by binary mass transfer, or spun up during the main-sequence evolution of B stars. In order to investigate these scenarios for this population of massive stars, we have been spectroscopically observing a set of 115 field Be stars with the Kitt Peak Coudè Feed telescope in both the Hα and Hγ wavelength regimes since 2004. This time baseline allows for examination of variability properties of the circumstellar disks as well as determine candidates for closer examination for binarity.We find that 90% of the observed stars show some variability with only 4% showing significant variability over the 4-year baseline. Such values may be compared with the significant variability seen in some clusters such as NGC 3766 (McSwain 2008). Also, while 20% of the sample consists of known binaries, we find that another 15-30% of the sample shows indications of binarity.This work has been supported in part by a grant from the Vanderbilt University Learning Sciences Institute, NASA grant # NNX08AV70G, and NSF Career grant AST-0349075.
A rate study of Type Ia supernovae with Subaru/XMM-Newton Deep Survey
Authors: Ihara Yutaka , Doi Mamoru , Morokuma Tomoki , Pain Raynald , Takanashi Naohiro , Yasuda Naoki , Aldering Greg , Dawson Kyle , Goldhaber Gerson , Hook Isobel , Lidman Chris , Perlmutter Saul , Spadafora Anthony , Suzuki Nao , Wang Lifan 
Published: April 2010

AbstractWe present a measurement of the rate of high-z Type Ia supernovae (SNe Ia) using multi-epoch observations of Subaru/XMM-Newton Deep Field (SXDF) with Suprime-Cam on the Subaru Telescope. Although SNe Ia are regarded as a standard candle, progenitor systems of SNe Ia have not been resolved yet. One of the key parameters to show the progenitor systems by observations is the delay time distribution between the binary system formation and subsequent SN explosion. Recently, a wide range of delay time is studied by SN Ia rates compared with an assumed cosmic star formation history. If SNe Ia with short delay time are dominant, the cosmic SN Ia rate evolution should closely trace that of the cosmic star formation. In order to detect a lot of high-z SNe Ia and measure SN Ia rates, we repeatedly carried out wide and deep imaging observations in the í-band with Suprime-Cam in 2002 (FoV~1 deg2, mi < 25.5 mag). We obtained detailed light curves of the variable objects, and 50 objects are classified as SNe Ia using the light curve fitting method at the redshift range of 0.2 < z < 1.3. In order to check the completeness and contamination of the light curve classification method, we performed Monte Carlo simulations and generated ~100,000 light curves of SNe Ia and II from templates. The control time and detection efficiency of the SN survey are also calculated using the artificial light curves. We derived an increasing trend of rates at around z ~ 1.2. Our results are almost consistent with other SN Ia rate results from low-z to high-z. Our results are the first results of high-z SN Ia rates with large statistics using light curves obtained by ground based telescopes, and give us visions of the SN rate studies for the future.
Metallicity gradients in dwarf elliptical galaxies
Authors: Koleva Mina , Prugniel Philippe , De Rijcke Sven , Zeilinger Werner W. 
Published: April 2010

AbstractWe discuss the relations between the metallicity gradients and the other characteristics of a set of dwarf elliptical galaxies in different environments. We suggest that dEs have typically metallicity gradients of −0.30 ± 0.25 dex/re, unrelated to their mass. Dwarf elliptical galaxies with embedded disks, or dS0, may have flat metallicity gradients.
GALEV evolutionary synthesis on the web – current state and future plans
Authors: Kotulla Ralf , Anders Peter , Weilbacher Peter , Fritze Uta 
Published: April 2010

AbstractGALEV evolutionary synthesis models describe the evolution of stellar populations in general, of star clusters as well as of galaxies, both in terms of resolved stellar populations and of integrated light properties over cosmological timescales of >13 Gyr from the onset of star formation shortly after the Big Bang until today. A new web-interface now allows to run customized GALEV models with user-defined parameters. This web-interface, all data, and many more features to come, can be found at http://www.galev.org.
What does the IMF really tell us about star formation?
Authors: Kouwenhoven M. B. N. , Goodwin S. P. 
Published: April 2010

AbstractObtaining accurate measurements of the initial mass function (IMF) is often considered to be the key to understanding star formation, and a universal IMF is often assumed to imply a universal star formation process. Here, we illustrate that different modes of star formation can result in the same IMF, and that, in order to truly understand star formation, a deeper understanding of the primordial binary population is necessary. Detailed knowledge on the binary fraction, mass ratio distribution, and other binary parameters, as a function of mass, is a requirement for recovering the star formation process from stellar population measurements.
Comparing six evolutionary population synthesis models
Authors: Liang Y. C. , Chen X. Y. , Hammer F. , Rodrigues M. , Zhao Y. H. , Zhong G. H. 
Published: April 2010

AbstractWe compare six evolutionary population synthesis (EPS) models, which have been popularly used in stellar populations analyses for galaxies. The resulted stellar populations of star-forming galaxies and E+A galaxies from these EPS models show that the dominated contribution (fraction) from young, intermediate and old populations to their lights are consistent, although the individual numbers may change significantly, 3-30%, which could relate to the different ingredients in EPS models, such as the stellar library, the stellar evolution tracks etc.
Stellar populations in brightest cluster galaxies
Authors: Loubser S. I. , Sánchez-Blázquez P. , Soechting I. K. , Sansom A. E. 
Published: April 2010

AbstractWe present the results of an investigation of a large sample of brightest cluster galaxies (BCGs), their kinematic and stellar population properties and the relationships between these and the properties of the host clusters. We have obtained high signal-to-noise, long-slit spectra of 49 BCGs in the nearby Universe with the Gemini and WHT telescopes. From this, we have measured the radial velocity and velocity dispersion profiles, and used the Lick system of absorption indices to derive Single Stellar Population (SSP)-equivalent ages, metallicities and α-abundance ratios. The results were systematically compared with those of large samples of ordinary elliptical galaxies in the same mass range. In addition, the derived properties were tested for possible correlations with the internal properties of the galaxies (mass, rotation and luminosity) and the properties of the host clusters (density, mass, distance to X-ray peak and cooling flows). We address the following questions: how the kinematic and stellar population properties differ from those of ordinary giant elliptical galaxies; and whether these properties are more influenced by the internal parameters of the BCGs or the properties of the clusters.
Ages and metallicities of early-type galaxies
Authors: Ogando Ricardo , Maia Marcio , Pellegrini Paulo , da Costa Luiz 
Published: April 2010

AbstractThe study of stellar populations in early-type galaxies give us clues on how they form and evolve. We calculate age, [Z/H], and [α/Fe] ratio for 162 early-type galaxies using the SSP models from Thomas, Maraston, & Bender (2003) applied to Lick indices measurements, such as Hβ, Mgb, Fe5270 and Fe5335. Those were obtained from longslit spectra observed in the ESO 1.52m telescope as described in Ogando et al. (2008). We study the relations between the SSP parameters and velocity dispersion, as well as the influence of environment on these relations. We find that age, [Z/H], and [α/Fe] correlate well with velocity dispersion, so that more massive galaxies, have on average, higher metallicities, ages and abundance ratios than that of the low-mass ones. Galaxies in high density regions are older and more metal-rich than those in regions with low number of neighbors. These results are not consistent with standard predictions of hierarchical clustering. In the last decade, this “anti-hierarchical” behavior has also been generally tagged as downsizing and has challenged the current theoretical framework of galaxy formation, calling for new ways of star formation regulation in early-type galaxies.
HI-selected Galaxies As a Probe of Quasar Absorption Systems
Authors: Okoshi K. , Nagashima M. , Gouda N. , Minowa Y. 
Published: April 2010

AbstractWe investigate the properties of local HI-selected galaxies detected in blind radio surveys by using semi-analytic galaxy formation models in the hierarchical structure formation scenario. By drawing a detailed comparison between the properties of the HI-selected galaxies and the quasar absorption systems, we investigate a link between the local galaxy population and the quasar absorption systems, particularly for Damped Lymanα absorption (DLA) systems (NHI ≥ 1020.3 cm−2) and sub-DLA systems (1019 < NHI < 1020.3 cm−2).We find that DLA galaxies, in which the HI column densities are as high as those of DLA systems, contribute primarily to the population of local HI-selected galaxies at MHI ≥ 108M⊙. By contrast, in the low-mass range MHI ≤ 107M⊙, sub-DLA galaxies replace DLA galaxies as the dominant population. The HI-selected galaxies would be a strong probe of DLA/sub-DLA systems.
The stellar populations of the AGN/Starburst galaxy NGC7582
Authors: Ricci T. V. , Steiner J. E. , Menezes R. B. , Garcia-Rissmann A. , Cid Fernandes R. 
Published: April 2010

AbstractNGC 7582 is defined as a Starburst/AGN galaxy, since its optical and X-Ray spectra reveal both characteristics. In this work, we show the results of a stellar population modeling in a datacube taken with the Gemini South telescope. We found that ~ 90% of the light in the field of view is emitted by stars that are less than 1 billion years old. A strong burst occurred about ~ 6 million years ago and has nearly solar metallicity. We also found a Wolf-Rayet cluster.
A spectroscopic survey of FHB stars near the south galactic pole
Authors: Rossi Silvia , Ortiz Roberto , Wilhelm Ronald , Costa Roberto , Beers Timothy C. 
Published: April 2010

AbstractWe present the results of a medium-resolution spectroscopic survey of 43 field horizontal-branch (FHB) candidates carried out near the south galactic pole, selected from the original list of FHB candidates compiled by Beers et al. (2007). The observation list includes only stars classified as “high-probability” candidates, according to their 2MASS infrared colours. Atmospheric parameters of some stars have been obtained by comparing some spectral features with theoretical models provided by Kurucz (1993). A comparison between the grid of model atmospheres with some parameters of the Hδ line allowed the determination of log g, whilst [Fe/H] was estimated by the equivalent widths of the MgII 4481 and Caii lines. About 77% of the sample have been classified as FHB stars, 10% as subdwarfs, whilst the remaining 13% are probably main-sequence A-type stars far from the Galactic plane.
Stellar archeology of the nearby LINER galaxies NGC 4579 and NGC 4736
Authors: Steiner J. E. , Menezes R. B. , Ricci T. V. , de Oliveira A. S. 
Published: April 2010

AbstractStellar archeology of nearby LINER galaxies may reveal if there is a stellar young population that may be responsible for the LINER phenomenon. We show results for the classical LINER galaxies NGC 4579 and NGC 4736 and find no evidence of such populations.
CNO abundance pattern in the red clump stars of the Milky Way
Authors: Tautvaišienė G. , Puzeras E. , Chorniy Y. , Barisevičius G. , Ilyin I. 
Published: April 2010

AbstractHipparcos orbiting observatory has revealed a large number of helium-core- burning “clump” stars of the Galactic field. These low-mass stars exhibit signatures of extra-mixing processes that require modeling beyond the standard stellar theory. In this contribution we overview available results of 12C, 13C, N and O abundances obtained by high-resolution spectra for clump stars and discuss them in the light of current predictions of stellar evolution models.
Using stellar population studies to determine the progenitors of GRBs and SNe
Authors: Thöne Christina C. , Christensen Lise , Fynbo Johan P. U. 
Published: April 2010

AbstractWe present spatially resolved emission line studies of three nearby GRB and SN hosts with longslit and/or IFU observations. We compare the environment of the GRBs/SNe with those of other star-forming regions in the host galaxy and try to get informations on the progenitor from stellar population models and metallicities.
Disentangling Nitrogen and Carbon Abundances in Early-Type Galaxies
Authors: Toloba Elisa , Sánchez-Blázquez Patricia , Gorgas Javier , Gibson Brad K. 
Published: April 2010

AbstractThe near-UV NH3360 feature has been measured in a sample of 35 early-type
galaxies in a wide range of masses and environments. We found that, contrary to
what is seen with Mg- and C-sensitive Lick-style indices, NH3360 does not vary
significantly with galaxy velocity dispersion. When compared with solar-scaled
stellar population models N/Fe appears mildly enhanced. We do not detect any
difference in the NH3360 index between galaxies in different environments. We
outline the important implications of these conclusions for our understanding of
the origin of carbon and nitrogen, and the star formation histories of
early-type galaxies.
Stellar populations in star forming galaxies in the Sloan Digital Sky Survey
Authors: Westera Pieter , Cuisinier François , Rabaça Carlos R. 
Published: April 2010

AbstractWe examine the star forming phenomenon as it can be encountered in galaxies in the Sloan Digital Sky Survey, which possibly contains the largest homogeneous sample of star forming galaxy spectra to date.After eliminating all spectra with an insufficient signal-to-noise ratio, without strong emission lines, and without the [OII] λ3727 Å line, which is necessary for the determination of the gas metallicity (which excludes galaxies with redshift ≲ 0.024–0.025), our sample contains ~6000 spectra of star forming galaxies.Through a detailed stellar population analysis employing evolutionary synthesis methods we determined the stellar composition of these galaxies, that is, the masses, ages and metallicities of their partial stellar populations.We find that most, possibly all, galaxies of our sample contain, apart from the presently bursting, ionising young generation (≤ 107 yrs), old (≥ 109 yrs) and intermediate (between 107 and 109 yrs) populations, whereas the old population dominates the stellar mass (but not the light).We also find that high (stellar) mass galaxies have higher gas metallicities and lower present star formation rates relative to their total (stellar) masses, than low mass galaxies, indicating a higher chemical evolution degree for high mass galaxies.Furthermore, we find that gas enrichment mechanisms in star forming galaxies do not vary with galactic mass, being the same for low- and high-mass galaxies on average. Gas enrichment mechanisms seem to present a greater variety at the high-mass end, though, indicating a more complex assembly history for high-mass galaxies.
HERMES – An instrument of the future
Authors: Wylie-de Boer Elizabeth , Freeman Kenneth 
Published: April 2010

AbstractHERMES is a new, multi-object high resolution spectrometer for the 3.9m Anglo Australian Telescope, using the existing 2dF positioner. The primary goal of the HERMES survey is to unravel the history of the Galaxy from detailed elemental abundances for about 1.2 million individual stars. The HERMES chemical tagging survey concentrates on the 5000 to 8000 Å window at a resolving power of 30,000 in order to identify dissolved star formation aggregates and ascertain the importance of mergers throughout the history of the Galaxy.
Constraining the chlorine monoxide (ClO)/chlorine peroxide (ClOOCl) equilibrium constant from Aura Microwave Limb Sounder measurements of nighttime ClO
Authors: Santee Michelle L. , Sander Stanley P. , Livesey Nathaniel J. , Froidevaux Lucien 
Published: April 2010

The primary ozone loss process in the cold polar lower stratosphere hinges on chlorine monoxide (ClO) and one of its dimers, chlorine peroxide (ClOOCl). Recently, analyses of atmospheric observations have suggested that the equilibrium constant, K
eq
, governing the balance between ClOOCl formation and thermal decomposition in darkness is lower than that in the current evaluation of kinetics data. Measurements of ClO at night, when ClOOCl is unaffected by photolysis, provide a useful means of testing quantitative understanding of the ClO/ClOOCl relationship. Here we analyze nighttime ClO measurements from the National Aeronautics and Space Administration Aura Microwave Limb Sounder (MLS) to infer an expression for K
eq
. Although the observed temperature dependence of the nighttime ClO is in line with the theoretical ClO/ClOOCl equilibrium relationship, none of the previously published expressions for K
eq
consistently produces ClO abundances that match the MLS observations well under all conditions. Employing a standard expression for K
eq
,
A
× exp(
B
/
T
), we constrain the parameter
A
to currently recommended values and estimate
B
using a nonlinear weighted least squares analysis of nighttime MLS ClO data. ClO measurements at multiple pressure levels throughout the periods of peak chlorine activation in three Arctic and four Antarctic winters are used to estimate
B
. Our derived
B
leads to values of K
eq
that are ∼1.4 times smaller at stratospherically relevant temperatures than currently recommended, consistent with earlier studies. Our results are in better agreement with the newly updated (2009) kinetics evaluation than with the previous (2006) recommendation.