Galaxy ecology: groups and low-density environments in the SDSS and 2dFGRS
Galaxy ecology: groups and low-density environments in the SDSS and 2dFGRS
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DOI：
10.1111/j.1365-2966.2004.07453.x
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发表时间：
2003-11
影响因子：
4.8
通讯作者：
M. Balogh;V. Eke;C. Miller;I. Lewis;R. Bower;W. Couch;R. Nichol;J. Bland-Hawthorn;I. Baldry
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文献类型：
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作者：
M. Balogh;V. Eke;C. Miller;I. Lewis;R. Bower;W. Couch;R. Nichol;J. Bland-Hawthorn;I. Baldry
利用2dF星系红移巡天（M-bJ < -19.5）和Sloan数字巡天（M-r < -20.6）的24968个星系在0.05 < z < 0.095处的有限体积样本和星表，分析了星系环境与Halpha发射线强度之间的相关性。我们通过以下方式来表征环境：（1）Sigma（5），由到第五近邻的投影距离确定的星系表面数密度;（2）rho（1.1）和rho（5.5），分别通过将星系分布与色散为1.1和5.5 Mpc的高斯核卷积获得的三维密度估计。我们发现，恒星形成和静止的星系形成两个不同的人口，其特征在于他们的H等效宽度，W-0（H α）。恒星形成星系和静止星系的相对数量随着局部密度的变化而不断变化。然而，W-0（Halpha）在恒星形成群体中的分布与环境无关。恒星形成星系的比例对大尺度上的密度ρ（5.5）表现出很强的敏感性，这可能与局部密度ρ（1.1）的趋势无关。我们使用两个不同选择的群星表，以证明与星系密度的相关性是近似独立的群速度色散，为sigma = 200-1000 km s（-1）。即使在密度最低的环境中，也不超过70%的星系显示出明显的阿尔法辐射。基于这些结果，我们得出结论，当今的星星形成率和环境之间的相关性是一个短时间尺度的机制，优先发生在高红移，如恒星爆发引起的星系-星系相互作用的结果。
We analyse the observed correlation between galaxy environment and Halpha emission-line strength, using volume-limited samples and group catalogues of 24 968 galaxies at 0.05 < z < 0.095, drawn from the 2dF Galaxy Redshift Survey (M-bJ < -19.5) and the Sloan Digital Sky Survey (M-r < -20.6). We characterize the environment by: (1) Sigma(5), the surface number density of galaxies determined by the projected distance to the fifth nearest neighbour; and (2) rho(1.1) and rho(5.5), three-dimensional density estimates obtained by convolving the galaxy distribution with Gaussian kernels of dispersion 1.1 and 5.5 Mpc, respectively. We find that star-forming and quiescent galaxies form two distinct populations, as characterized by their H equivalent width, W-0(Halpha). The relative numbers of star-forming and quiescent galaxies vary strongly and continuously with local density. However, the distribution of W-0(Halpha) amongst the star-forming population is independent of environment. The fraction of star-forming galaxies shows strong sensitivity to the density on large scales, rho(5.5), which is likely independent of the trend with local density, rho(1.1). We use two differently selected group catalogues to demonstrate that the correlation with galaxy density is approximately independent of group velocity dispersion, for sigma = 200-1000 km s(-1). Even in the lowest-density environments, no more than similar to70 per cent of galaxies show significant Halpha emission. Based on these results, we conclude that the present-day correlation between star formation rate and environment is a result of short-time-scale mechanisms that take place preferentially at high redshift, such as starbursts induced by galaxy-galaxy interactions.