共查询到20条相似文献，搜索用时 15 毫秒
1.
A. Schurer F. Calura L. Silva A. Pipino G. L. Granato F. Matteucci R. Maiolino 《Monthly notices of the Royal Astronomical Society》2009,394(4):2001-2021
We present photometric evolution models of galaxies, in which, in addition to the stellar component, the effects of an evolving dusty interstellar medium have been included with particular care. Starting from the work of Calura et al., in which chemical evolution models have been used to study the evolution of both the gas and dust components of the interstellar medium in the solar neighbourhood, elliptical and irregular galaxies, it has been possible to combine these models with a spectrophotometric stellar code that includes dust reprocessing ( grasil ) to analyse the evolution of the spectral energy distributions (SEDs) of these galaxies. We test our models against observed SEDs both in the local universe and at high redshift, and use them to predict how the percentage of reprocessed starlight evolves for each type of galaxy. The importance of following the dust evolution is investigated by comparing our results with those obtained by adopting simple assumptions to treat this component. 相似文献
2.
M.G. Edmunds 《Monthly notices of the Royal Astronomical Society》2001,328(1):223-236
We give an elementary model for the evolution of dust in galaxies, based on abundance arguments. The model takes account of grain core production in both supernovae and giant stars, and includes mantle growth in the interstellar medium. Destruction of grain cores does not appear to be a dominant effect. We show that a self-consistent picture can be made in which the interstellar dust mass is an approximately constant fraction of the heavy element mass in the interstellar medium. This result is demonstrated to be essentially independent of outflow or inflow of interstellar material. 相似文献
3.
B. E. J. Pagel & L. Portinari 《Monthly notices of the Royal Astronomical Society》1998,298(3):747-752
The slope Δ Y /Δ Z is a quantity of interest in relation to stellar evolution, the initial mass function and the determination of the primordial helium abundance. In this paper we estimate Δ Y /Δ Z from fine structure in the main sequence of nearby stars from Hipparcos data for stars with Z ≤ Z⊙. We find a value of about 3, which is consistent with what has been found in extragalactic H II regions and with stellar models for suitable upper limits to the initial masses of supernovae according to the initial mass function slope adopted. 相似文献
4.
5.
6.
利用从斯隆数字巡天(Sloan Digital Sky Survey,简称SDSS)第4次释放的光谱数据中选取的10~5个发射线星系样本,研究了[O_Ⅱ]λ3727/Hα流量比与星系尘埃消光、气体电离态和金属丰度的关系.发现尘埃消光改正对[O_Ⅱ]λ3727/Hα谱线流量比影响显著,消光改正前、后的[O_Ⅱ]λ3727/Hα谱线流量比的中值分别为0.48和0.89;尘埃消光改正后,F([O_Ⅱ]λ3727)-F(Hα)的弥散显著减小.贫金属星系的[O_Ⅱ]λ3727/Hα谱线流量比随星系气体的电离度增高而减小,而富金属星系不存在这种关系.另外,[O_Ⅱ]λ3727/Hα流量比与星系金属丰度相关.当12+lg(O/H)8.5时,星系[O_Ⅱ]λ3727/Hα流量比随金属丰度增加而下降;12+lg(O/H)8.5的星系,谱线流量比与金属丰度正相关.最后,利用气体电离度参数和星系的金属丰度,给出了计算不同类型星系[O_Ⅱ]λ3727/Hα流量比的公式.LAMOST望远镜将观测到大量红移z0.4的星系光谱,利用该公式可以给出星系的[O_Ⅱ]λ3727/Hα流量比,从而可以利用[O_Ⅱ]λ3727谱线流量计算z0.4星系的恒星形成率. 相似文献
7.
8.
S.L. Ellison S.G. Ryan J.X. Prochaska 《Monthly notices of the Royal Astronomical Society》2001,326(2):628-636
The study of elemental abundances in damped Lyman alpha systems (DLAs) at high redshift represents one of our best opportunities to probe galaxy formation and chemical evolution at early times. By coupling measurements made in high- z DLAs with our knowledge of abundances determined locally and with nucleosynthetic models, we can start to piece together the star formation histories of these galaxies. Here, we discuss the clues to galactic chemical evolution that may be gleaned from studying the abundance of Co in DLAs. We present high resolution echelle spectra of two quasi-stellar objects (QSOs), Q2206−199 and Q1223+17, both already known to exhibit intervening damped systems. These observations have resulted in the first ever detection of Co at high redshift, associated with the z abs =1.92 DLA in the sightline towards Q2206−199. We find that the abundance of Co is approximately 1/4 solar and that there is a clear overabundance relative to iron, [Co/Fe]=+0.31±0.05 . From the abundance of Zn, we determine that this is a relatively metal-rich DLA, with a metallicity of approximately 1/3 Z⊙ . Therefore, this first detection of Co is similar to the marked overabundance relative to Fe seen in Galactic bulge and thick-disc stars. 相似文献
9.
Ignasi Ribas Carme Jordi Jordi Torra Álvaro Giménez 《Monthly notices of the Royal Astronomical Society》2000,313(1):99-111
The chemical enrichment law Y ( Z ) is studied by using detached double-lined eclipsing binaries with accurate absolute dimensions and effective temperatures. A sample of 50 suitable systems was collected from the literature, and their effective temperatures were carefully re-determined. The chemical composition of each of the systems was obtained by comparison with stellar evolutionary models, under the assumption that they should fit an isochrone to the observed properties of the components. Evolutionary models covering a wide grid in Z and Y were adopted for our study. An algorithm was developed for searching the best-fitting chemical composition (and the age) for the systems, based on the minimization of a χ 2 function. The errors (and biases) of these parameters were estimated by means of Monte Carlo simulations, with special care put on the correlations existing between the errors of both components. In order to check the physical consistency of the results, we compared our metallicity values with empirical determinations, obtaining excellent coherence. The independently derived Z and Y values yielded a determination of the chemical enrichment law via weighted linear least-squares fit. Our value of the slope, Δ Y /Δ Z =2.2±0.8, is in good agreement with recent results, but it has a smaller formal error and it is free of systematic effects. Linear extrapolation of the enrichment law to zero metals leads to an estimation of the primordial helium abundance of Y p =0.225±0.013, possibly affected by systematics in the effective temperature determination. 相似文献
10.
Leonid Pilyugin 《Astrophysics and Space Science》2003,284(2):775-778
Spiral galaxies with a reported bend in the slope of the oxygen abundance O/HR
23, derived with the traditionally used R23-method, are examined. It is shown that the artificial origin of the reported bends can be naturally explained. Two causes
of the false bend in the slope of O/HR
23 are indicated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
12.
Leticia Carigi Xavier Hernandez Gerard Gilmore 《Monthly notices of the Royal Astronomical Society》2002,334(1):117-128
We calculate chemical evolution models for four dwarf spheroidal (dSph) satellites of the Milky Way (Carina, Ursa Minor, Leo I and Leo II) for which reliable non-parametric star formation histories have been derived. In this way, the independently-obtained star formation histories are used to constrain the evolution of the systems we are treating. This allows us to obtain robust inferences on the history of such crucial parameters of galactic evolution as gas infall, gas outflows and global metallicities for these systems. We can then trace the metallicity and abundance ratios of the stars formed, the gas present at any time within the systems and the details of gas ejection, of relevance to enrichment of the galaxies environment. We find that galaxies showing one single burst of star formation (Ursa Minor and Leo II) require a dark halo slightly larger that the current estimates for their tidal radii, or the presence of a metal-rich selective wind that might carry away much of the energy output of their supernovae before this might have interacted and heated the gas content, for the gas to be retained until the observed stellar populations have formed. Systems showing extended star formation histories (Carina and Leo I), however, are consistent with the idea that their tidally-limited dark haloes provide the necessary gravitational potential wells to retain their gas. The complex time structure of the star formation in these systems remains difficult to understand. Observations of detailed abundance ratios for Ursa Minor strongly suggest that the star formation history of this galaxy might in fact resemble the complex picture presented by Carina or Leo I, but localized at a very early epoch. 相似文献
13.
Sara L. Ellison Luc Simard Nicolas B. Cowan Ivan K. Baldry David R. Patton Alan W. McConnachie 《Monthly notices of the Royal Astronomical Society》2009,396(3):1257-1272
Using a large (14 857), homogenously selected sample of cluster galaxies identified in the Sloan Digital Sky Survey Data Release 4, we investigate the impact of cluster membership and local density on the stellar mass–gas phase metallicity relation (MZR). We show that stellar metallicities are not suitable for this work, being relatively insensitive to subtle changes in the MZR. Accurate nebular abundances can be obtained for 1318 cluster galaxies in our sample and we show that these galaxies are drawn from clusters that are fully representative of the parent sample in terms of mass, size, velocity dispersion and richness. By comparing the MZR of the cluster galaxies with a sample of control galaxies matched in mass, redshift, fibre covering fraction and rest-frame g − r colour cluster galaxies are found to have, on average, higher metallicities by up to 0.04 dex. The magnitude of this offset does not depend strongly on galactic half-light radius or cluster properties such as velocity dispersion or cluster mass. The effect of local density on the MZR is investigated, using the presence of a near neighbour and both two- and three-dimensional density estimators. For all three metrics, it is found that the cluster galaxies in locally rich environments have higher median metallicities by up to ∼0.05 dex than those in locally poor environments (or without a near neighbour). Control (non-cluster) galaxies at locally high densities exhibit similar metal enhancements. Taken together, these results show that galaxies in clusters are, on average, slightly more metal rich than the field, but that this effect is driven by local overdensity and not simply cluster membership. 相似文献
14.
C.C. Thne J. Fynbo P. Goldoni A. de Ugarte Postigo S. Covino S. Campana the X‐shooter GRB collaboration 《Astronomische Nachrichten》2011,332(3):281-282
GRB 100219A at z = 4.667 has been the highest redshift gamma‐ray burst observed with the X‐shooter spectrograph up to now. The spectrum covering the range from 5000 to 24000 Å and a large number of absorption lines allows to make a detailed study of the interstellar medium in a high redshift galaxy. The ISM in the low ionisation state and the kinematics of the absorption line components reveal a complex velocity field. The metallicity measured from different absorption lines is around 0.1 solar. Other GRB hosts at redshift beyond ∼3 have similar metallicities albeit with a large scatter in the metallicity distribution. X‐shooter will allow us to determine metallicities of a larger number of GRB hosts beyond redshift 5, to probe the early chemical enrichment of the Universe and to study its evolution from redshift 2 to beyond 10 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
Enrique Pérez-Montero Thierry Contini 《Monthly notices of the Royal Astronomical Society》2009,398(2):949-960
We study the relation between nitrogen and oxygen abundances as a function of metallicity for a sample of emission-line objects for which a direct measurement of the metallicity has been possible. This sample is representative of the very different conditions in ionization and chemical enrichment that we can find in the Universe. We first construct the N/O versus O/H ratio diagram, and discuss its large dispersion at all metallicity regimes. Using the same sample and a large grid of photoionization models covering very different values of the N/O ratio, we then study the most widely used strong-line calibrators of metallicity based on [N ii ] emission lines, such as N2 and O3N2. We demonstrate that these parameters underestimate the metallicity at low N/O ratios and vice versa. We also investigate the effect of the N/O ratio on different diagnostic diagrams used to discriminate narrow-line active galactic nuclei from star-forming regions, such as the [O iii ]/Hβ versus [N ii ]/Hα, and show that a large fraction of the galaxies catalogued as composite in this diagram can be, in fact, star-forming galaxies with a high value of the N/O ratio. Finally, using strong-line methods sensitive to the N/O abundance ratio, like N2O2 and N2S2, we investigate the relation between this ratio and the stellar mass for the galaxies of the Sloan Digital Sky Survey. We find, as in the case of the mass–metallicity relation, a correlation between these two quantities and a flattening of the relation for the most massive galaxies, which could be a consequence of the enhancement of the dispersion of N/O ratio in the high-metallicity regime. 相似文献
16.
17.
Leonid S. Pilyugin Trinh X. Thuan José M. Vílchez 《Monthly notices of the Royal Astronomical Society》2007,376(1):353-360
We search for the maximum oxygen abundance in spiral galaxies. Because this maximum value is expected to occur in the centres of the most luminous galaxies, we have constructed the luminosity – central metallicity diagram for spiral galaxies, based on a large compilation of existing data on oxygen abundances of H ii regions in spiral galaxies. We found that this diagram shows a plateau at high luminosities (−22.3 ≲ M B ≲−20.3) , with a constant maximum value of the gas-phase oxygen abundance 12 + log (O/H) ∼ 8.87 . This provides strong evidence that the oxygen abundance in the centres of the most luminous metal-rich galaxies reaches the maximum attainable value of oxygen abundance. Since some fraction of the oxygen (about 0.08 dex) is expected to be locked into dust grains, the maximum value of the true gas + dust oxygen abundance in spiral galaxies is 12 + log(O/H) ∼ 8.95. This value is a factor of ∼2 higher than the recently estimated solar value. Based on the derived maximum oxygen abundance in galaxies, we found the oxygen yield to be about 0.0035, depending on the fraction of oxygen incorporated into dust grains. 相似文献
18.
19.