Radial gradients in initial mass function sensitive absorption features in the Coma brightest cluster galaxies
Radial gradients in initial mass function sensitive absorption features in the Coma brightest cluster galaxies
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DOI：
10.1093/mnras/stw2712
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发表时间：
2016-11
影响因子：
4.8
通讯作者：
S. Zieleniewski;R. Houghton;N. Thatte;R. Davies;S. Vaughan
中科院分区：
文献类型：
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作者：
S. Zieleniewski;R. Houghton;N. Thatte;R. Davies;S. Vaughan
利用Oxford短波积分场光谱仪，我们跟踪了后发座星系团中三个星系的初始质量函数（IMF）敏感吸收特征的径向变化。我们获得了两个中央最亮星系团（BCGs）NGC4889、NGC4874和西南星系团NGC4839中的BCG的中央5kpc的分辨光谱，以及作为低σ* 对照的NGC4873的未分辨数据。钠Na I SDSS、钙三重态CaT和氢化铁FeH 0.99，沿着镁Mg I 0.88和氧化钛TiO 0.89特征。我们采用两种不同的方法，大地校正和天空扣除周围微弱的FeH功能，以验证我们的分析。在NGC4889中，我们发现Na I SDSS和CaT的梯度很强，但FeH的轮廓很平坦，与恒星群体合成模型相比，这表明一个古老的，α增强的群体具有Chabrier，甚至是底光IMF。年龄和丰度与以前的研究是一致的，但正常的IMF是在最近的结果表明，随着速度dispersion.We增加IMF斜率增加测量平坦的Na I SDSS和FeH的配置文件内NGC4874，并确定一个老的，可能略有α增强和Chabrier IMF人口。我们在NGC4873中发现了α增强的Chabrier IMF种群。在NGC4839中，我们测量了强Na I SDSS和强FeH，尽管具有较大的系统不确定性，表明可能存在较重的IMF。我们推断这些星系的IMF得到了已发表的动力学模型的支持。我们强调，国际货币基金组织的限制应进一步证实光谱覆盖和独立的方法对星系的基础上。
Using the Oxford ShortWavelength Integral Field specTrograph, we trace radial variations of initial mass function (IMF)-sensitive absorption features of three galaxies in the Coma cluster. We obtain resolved spectroscopy of the central 5 kpc for the two central brightest cluster galaxies (BCGs) NGC4889, NGC4874, and the BCG in the south-west group NGC4839, as well as unresolved data for NGC4873 as a low-σ* control.We present radial measurements of the IMF-sensitive features: sodium Na I SDSS , calcium triplet CaT, and iron-hydride FeH0.99, along with the magnesium Mg I0.88 and titanium oxide TiO0.89 features. We employ two separate methods for both telluric correction and sky subtraction around the faint FeH feature to verify our analysis. Within NGC4889 we find strong gradients of Na I SDSS and CaT but a flat FeH profile, which, from comparing to stellar population synthesis models, suggests an old, α-enhanced population with a Chabrier, or even bottom-light IMF. The age and abundance are in line with previous studies but the normal IMF is in contrast to recent results suggesting an increased IMF slope with increased velocity dispersion.We measure flat Na I SDSS and FeH profiles within NGC4874, and determine an old, possibly slightly α-enhanced and Chabrier IMF population. We find an α-enhanced, Chabrier IMF population in NGC4873. Within NGC4839 we measure both strong Na I SDSS and strong FeH, although with a large systematic uncertainty, suggesting a possible heavier IMF. The IMFswe infer for these galaxies are supported by published dynamical modelling. We stress that IMF constraints should be corroborated by further spectral coverage and independent methods on a galaxy-by-galaxy basis.