共查询到20条相似文献，搜索用时 281 毫秒
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从Sloan数字巡天第2批释放的数据(SDSS DR2)中选择了395个在r波段亮于15等的面向晚型旋涡星系作为样本,研究了盘的颜色梯度与结构参数的关系.结果表明:盘的颜色梯度与盘的绝对星等(质量)无关;盘的颜色梯度与盘的尺度有关,越大的盘颜色梯度越陡;盘的颜色梯度与盘的颜色有关,越蓝的盘颜色梯度越陡;盘的颜色梯度与盘的表面亮度有关,越亮的盘颜色梯度越陡,并简单讨论了盘的颜色梯度与各结构参数的相关关系对晚型旋涡星系盘恒星形成历史的约束. 相似文献
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基于COSMOS(Cosmic Evolution Survey)/Ultra VISTA(Ultra-deep Visible and Infrared Survey Telescope for Astronomy)场中多波段测光数据,利用质量限选取了红移分布在0z3.5的星系样本.通过UVJ(U-V和V-J)双色图分类判据将星系分类成恒星形成星系(SFGs)和宁静星系(QGs).对于红移分布在0z1.5范围内且M*1011M⊙的QGs来说,该星系在样本中所占比例高于70%.在红移0z3.5范围内,恒星形成星系的恒星形成率(SFR)与恒星质量(M*)之间有着很强的主序(MS)关系.对于某一固定的恒星质量M*来说,星系的SFR和比恒星形成率(s SFR)会随着红移增大而增大,这表明在高红移处恒星形成星系更加活跃,有激烈的恒星形成.相对于低质量的星系来说,高质量的SFGs有较低的s SFR,这意味着低质量星系的增长更多的是通过星系本身的恒星形成.通过结合来自文献中数据点信息,发现更高红移(2z8)星系的s SFR随红移的演化趋势变弱,其演化关系是s SFR∝(1+z)0.94±0.17. 相似文献
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从观测上测定早型星系中恒星形成活动随红移的演化有助于理解这类星系的形成演化.结合GEMS（Galaxy Evolution from Morphology and SEDs）巡天的HST/ACS（Hubble Space Telescope/Advanced Camera for Surveys）高分辨图像和CDFS（ChandraDeep Field South）天区Spitzer、GALEX（Galaxy Evolution Explorer）等多波段数据,基于形态、颜色和恒星质量选出一个0.2≤z≤1.0红移范围的包含456个早型星系的完备样本.利用stacking技术测量了样本星系紫外与红外平均光度,估计早型星系的恒星形成率.结果显示,早型星系中的恒星形成率较低(<3 M⊙·yr-1),随红移递减而降低.在红移z=1以来的恒星形成贡献的质量小于15%.星族分析亦肯定大质量早型星系的主体星族形成于宇宙早期（z>2）. 相似文献
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利用赫歇尔空间望远镜的H-ATLAS(Herschel Astrophysical Terahertz Large Area Survey)SDP(Science Demonstration Phase)天区从紫外到亚毫米波段数据,结合星族合成方法和尘埃模型,计算了星系的红外总光度.在此基础上,分别针对强恒星形成星系和弱恒星形成星系,研究了利用紫外光度、红外光度和Hα谱线计算得到的恒星形成率(Star Formation Rate,SFR)的差异以及导致差异的内在物理起因.发现对于恒星形成活动强的星系,这3种恒星形成率指针给出的结果基本一致,弥散较小、只是在高恒星形成率端,利用紫外光度算得的恒星形成率比利用Hα谱线流量算得的恒星形成率略微偏小;而在低恒星形成率端,紫外光度指针偏大于Hα谱线指针;红外光度指针与Hα谱线指针在两端无明显偏差.对弱恒星形成星系,紫外光度、Hα谱线和红外光度3种恒星形成率指针存在明显的差异,且弥散较大.利用紫外光度和Hα谱线计算得到的恒星形成率的弥散和系统偏差随着星系年龄、质量的增加而增大.系统偏差增大的主要原因是利用紫外连续谱斜率β定标恒星形成活动较弱星系的消光时,高估了这些星系的紫外消光,使得消光改正后的紫外光度偏大.另外,MPA/JHU(Max Planck Institute for Astrophysics/Johns Hopkins University)数据库中弱恒星形成星系的恒星形成率SFR(Hα)比真实值偏低. 相似文献
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基于半解析模型和SDSS DR4(Sloan Digital Sky Survey Data Release 4),研究了环境对星系性质的影响.通过对以颜色、恒星形成率和恒星质量的带权重的相关函数的测量,发现半解析模型在颜色和恒星质量上与SDSS数据符合得比较好,而恒星形成率则在SDSS数据中表现为与环境无关.此结论证实了半解析模型对星系中部分性质与环境关系的预测,但对于恒星形成率为何与环境无关仍有待研究. 相似文献
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The local face-on disk galaxies are selected as galaxy sample from the main galaxy sample of the Seventh Data Release of Sloan Digital Sky Survey (SDSS DR7). The correlations between the colors and sizes of disk galaxies with equivalent total stellar masses are statistically investigated and their realities are tested. It is found that for the disk galaxies with equivalent masses, the correlation between u-r color and size is very weak. However, there are anticorrelations between g-r, r-i, r-z colors and sizes, i.e., the larger are the sizes of galaxies, the bluer are their colors. This result means that the mass distribution of disk galaxies has a significant influence on their star formation history. The galaxies with more extended mass distributions evolve more slowly. 相似文献
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X. Kong 《Astrophysics and Space Science》2003,284(2):905-908
We have observed the largest optical spectra sample of 97 blue compact galaxies. Stellar population properties of 74 star-forming BCGs of them were derived by comparing the equivalent widths of strong absorption features and continuum colors, using a method of empirical population synthesis based on star cluster sample. The results indicate that blue compact galaxies are typically age-composite stellar system, the continuum flux fractions at 5870Å due to old stellar components and young stellar components are both important for most of the galaxies. The stellar populations of blue compact galaxies present a variety of characteristics, and the contribution from different age and metallicity components is different. The star formation episodes are usually short, some galaxies maybe undergoing their first global episode of star formation, while for the most sample galaxies, older stars contribute to at most half the optical emission. Our results suggest that BCGs are old galaxies, in which star formation occurs in short intense burst separated by long quiescent phases. 相似文献
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J.C. Vega Beltrán E. Pignatelli W.W. Zeilinger A. Pizzella E.M. Corsini F. Bertola J.E. Beckman 《Astrophysics and Space Science》2001,276(2-4):509-516
We present a comparison between the ionized gas and stellar kinematics for a sample of five early-to-intermediate disc galaxies.
We measured the major axis V and σ radial profiles for both gas and stars, and the h
3 and h
4 radial profiles of the stars. We also derived from the R-band surface photometry of each galaxy the light contribution of their bulges and discs. In order to investigate the differences
between the velocity fields of the sample galaxies we adopted the self-consistent dynamical model by Pignatelli and Galletta
(1999), which takes into account the asymmetric drift effects, the projection effects along the line of sight and the non-Gaussian
shape of the line profiles due to the presence of different components with distinct dynamical behaviour. We find for the
stellar component a sizeable asymmetric drift effect in the inner regions of all the sample galaxies, as results from comparing
their stellar rotation curves with the circular velocity predicted by the models. The galaxy sample is not wide enough to
draw general conclusions. However, we have found a possible correlation between the presence of slowly rising gas rotation
curves and the ratio of the bulge/disc half-luminosity radii, while there is no obvious correlation with the key parameter
represented by the morphological classification, namely the bulge/disc luminosity ratio. Systems with a diffuse, dynamically
hot component (bulge or lens) with a scale length comparable to that of the disc are characterized by slowly rising gas rotation
curves. On the other hand, in systems with a small bulge the gas follows almost circular motions, regardless of the luminosity
of the bulge itself. We noticed a similar behaviour also in the gas and stellar kinematics of the two early-type spiral galaxies
modelled by Corsini et al.(1998).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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M. Mouhcine † I. K. Baldry S. P. Bamford 《Monthly notices of the Royal Astronomical Society》2007,382(2):801-808
We use a 0.040 < z < 0.085 sample of 37 866 star-forming galaxies from the Fourth Data Release of the Sloan Digital Sky Survey to investigate the dependence of gas-phase chemical properties on stellar mass and environment. The local density, determined from the projected distances to the fourth and fifth nearest neighbours, is used as an environment indicator. Considering environments ranging from voids, i.e. log Σ≲−0.8 , to the periphery of galaxy clusters, i.e. log Σ≈ 0.8 , we find no dependence of the relationship between galaxy stellar mass and gas-phase oxygen abundance, along with its associated scatter, on local galaxy density. However, the star-forming gas in galaxies shows a marginal increase in the chemical enrichment level at a fixed stellar mass in denser environments. Compared with galaxies of similar stellar mass in low-density environments, they are enhanced by a few per cent for massive galaxies to about 20 per cent for galaxies with stellar masses ≲109.5 M⊙ . These results imply that the evolution of star-forming galaxies is driven primarily by their intrinsic properties and is largely independent of their environment over a large range of local galaxy density. 相似文献
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《天文和天体物理学研究(英文版)》2019,(12)
The stellar mass-to-light ratio(M_*/L) of galaxies in a given wave band shows tight correlations with optical colors, which have been widely applied as cheap estimators of galaxy stellar masses. These estimators are usually calibrated using either broadband spectral energy distributions(SEDs) or spectroscopy at galactic centers. However, it is unclear whether the same estimators provide unbiased M_*/L for different regions within a galaxy. In this work we employ integral field spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory(Ma NGA) survey. We also examine the correlations of spatially resolved M_*/L obtained from full spectral fitting, with different color indices, as well as galaxy morphology types, distances to the galactic center, and stellar population parameters such as stellar age and metallicity.We find that the(g-r) color is better than any other color indices, and it provides almost unbiased M_*/L for all the SDSS five bands and for all types of galaxies or regions, with only slight biases depending on stellar age and metallicity. Our analysis indicates that combining multiple colors and/or including other properties to reduce the systematics and scatters of the estimator does not work better than a single color index defined by two bands. Therefore, we have obtained a best estimator with the(g-r) color and applied it to the Ma NGA galaxies. Both the two-dimensional map and radial profile of M_*/L are reproduced well in most cases. Our estimator may be applied to obtain surface mass density maps for large samples of galaxies from imaging surveys at both low and high redshifts. 相似文献
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The non‐linear dynamics of bending instability and vertical structure of a galactic stellar disc embedded into a spherical halo are studied with N‐body numerical modelling. Development of the bending instability in stellar galactic disc is considered as the main factor that increases the disc thickness. Correlation between the disc vertical scale height and the halo‐to‐disc mass ratio is predicted from the simulations. The method of assessment of the spherical‐to‐disc mass ratio for edge‐on spiral galaxies with a small bulge is considered. Modelling of eight edge‐on galaxies: NGC 891, NGC 4738, NGC 5170, UGC 6080, UGC 7321, UGC 8286, UGC 9422 and UGC 9556 is performed. Parameters of stellar discs, dark haloes and bulges are estimated. The lower limit of the dark‐to‐luminous mass ratio in our galaxies is of the order of one within the limits of their stellar discs. The dark haloes dominate by mass in the galaxies with very thin stellar discs (NGC 5170, UGC 7321 and UGC 8286) (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Rachel Mandelbaum † Cheng Li Guinevere Kauffmann Simon D. M. White 《Monthly notices of the Royal Astronomical Society》2009,393(2):377-392
We compute two-point correlation functions and measure the shear signal due to galaxy–galaxy lensing for 80 000 optically identified and 5700 radio-loud active galactic nuclei (AGN) from Data Release 4 of the Sloan Digital Sky Survey. Halo occupation models are used to estimate halo masses and satellite fractions for these two types of AGN. The large sample size allows us to separate AGN according to the stellar mass of their host galaxies. We study how the halo masses of optical and radio AGN differ from those of the parent population at fixed M * . Halo masses deduced from clustering and from lensing agree satisfactorily. Radio AGN are found in more massive haloes than optical AGN: in our samples, their mean halo masses are 1.6 × 1013 and 8 × 1011 h −1 M⊙ , respectively. Optical AGN follow the same relation between stellar mass and halo mass as galaxies selected without regard to nuclear properties, but radio-loud AGN deviate significantly from this relation. The dark matter haloes of radio-loud AGN are about twice as massive as those of control galaxies of the same stellar mass. This boost is independent of radio luminosity, and persists even when our analysis is restricted to field galaxies. The large-scale gaseous environment of the galaxy clearly plays a crucial role in producing observable radio emission. The dark matter halo masses that we derive for the AGN in our two samples are in good agreement with recent models in which feedback from radio AGN becomes dominant in haloes where gas cools quasi-statically. 相似文献
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Ignacio Ferreras Thorsten Lisker Anna Pasquali Sadegh Khochfar Sugata Kaviraj 《Monthly notices of the Royal Astronomical Society》2009,396(3):1573-1578
The evolution of number density, size and intrinsic colour is determined for a volume-limited sample of visually classified early-type galaxies selected from the Hubble Space Telescope /Advanced Camera for Surveys images of the Great Observatories Origins Deep Survey (GOODS) North and South fields (version 2). The sample comprises 457 galaxies over 320 arcmin2 with stellar masses above 3 × 1010 M⊙ in the redshift range 0.4 < z < 1.2 . Our data allow a simultaneous study of number density, intrinsic colour distribution and size. We find that the most massive systems (≳3 × 1011 M⊙ ) do not show any appreciable change in comoving number density or size in our data. Furthermore, when including the results from 2dF galaxy redshift survey, we find that the number density of massive early-type galaxies is consistent with no evolution between z = 1.2 and 0, i.e. over an epoch spanning more than half of the current age of the Universe. We find large discrepancies between the predictions of semi-analytic models. Massive galaxies show very homogeneous intrinsic colour distributions, with nearly flat radial colour gradients, but with a significant negative correlation between stellar mass and colour gradient, such that red cores appear predominantly in massive galaxies. The distribution of half-light radii – when compared to z ∼ 0 and z > 1 samples – is compatible with the predictions of semi-analytic models relating size evolution to the amount of dissipation during major mergers. 相似文献
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Current views consider shell structures as bona fide signatures of a recent minor/major merging event though also weak interaction models (WIM) could produce long lasting shells on host galaxies possessing a stellar thick disc.We present a B V band photometric study of a sample of 5 shell galaxies belonging to the Malin & Carter (1983) compilation. The structural properties and colors of the galaxies, as well as the colors of their shells are examined in detail. We did not find signatures of the presence of double nuclei. NGC 7585 is the only E galaxy in the sample and has a moderately boxy structure. The other galaxies have either a discy structure or are mixed E/S0 type galaxies. NGC 474 is a true lenticular. NGC 6776 shows a diffuse asymmetric outer structure and a system of tails of the the same color of the galaxy body; but not clear shells. In general, the color of the shells in our sample is similar or slightly redder than that of the host galaxy, whose color, in turn, is typical of the early‐type morphological class. One of the outer shells of NGC 474 is significantly bluer than the body of the galaxy. Since NGC 474 appears to be interacting with NGC 470, the color of this one shell could be explained as result of a recent acquisition of material through tidal interaction. The WIM hypothesis could explain both the red and the blue shells of NGC 474, this latter acquired from the fly‐by of the nearby companion NGC 470, but the lack of the constancy of shell surface brightness as a ratio of the underlying galaxy brightness argues against WIM. We speculate about evidence, which also comes from different observations, that suggests a merging/accretion origin of the shells. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献