arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1502.02032astro-ph.GAastro-ph.CO
收藏

巨大的室女座星系M87的外围区域。恒星晕和团内光的运动学分离

The outer regions of the giant Virgo galaxy M87. Kinematic separation of stellar halo and intracluster light

Alessia Longobardi, Magda Arnaboldi, Ortwin Gerhard, Reinhard Hanuschik

摘要:

我们对室女座A的BCG M87周围总面积约为0. 4度^2的287个行星状星云(PNs)进行了光谱研究。利用这些数据,我们可以区分恒星晕和同空间的团内光(ICL)。PN从其窄且对称的红移λ 5007\4959埃[OIII]发射线以及不存在显著的连续谱来识别。我们实现了一个强大的技术来测量从投影相空间的晕速度色散,以确定PN与M87晕和ICL。光谱证实PN的速度分布是双峰的,包含一个狭窄的组件集中在系统的BCG速度和偏心的更广泛的组件,我们确定为晕和ICL,分别。Halo和ICPN具有不同的空间分布:Halo PN跟随星系的光,而ICPN的特征是较浅的幂律分布。复合PN数密度分布图显示了与M87晕和ICL相关的不同PN种群的叠加,其特征在于不同的PN α参数,ICL每单位光贡献的PN约为3倍。当m_5007=28.8时,M87晕PN光度函数(PNLF)比IC PNLF有更陡的倾斜度,而两者都比M31隆起的标准PNLF更陡。此外,IC PNLF有一个比明亮截止暗1-1.5等的倾角,让人想起具有延长恒星形成历史的系统的PNLF。M87晕和室女座ICL是动力学上不同的两个分量,具有不同的密度剖面和速度分布。晕和ICL的不同α值和PNLF形状表明不同的母恒星星族,与大半径处存在向蓝颜色的梯度相一致。这些结果反映了室女星系团的等级结构。

英文摘要:

We present a spectroscopic study of 287 Planetary Nebulas (PNs) in a total area of ~0.4 deg^2 around the BCG M87 in Virgo A. With these data we can distinguish the stellar halo from the co-spatial intracluster light (ICL). PNs were identified from their narrow and symmetric redshifted lambda 5007\4959 Angstrom [OIII] emission lines, and the absence of significant continuum. We implement a robust technique to measure the halo velocity dispersion from the projected phase-space to identify PNs associated with the M87 halo and ICL. The velocity distribution of the spectroscopically confirmed PNs is bimodal, containing a narrow component centred on the systemic velocity of the BCG and an off-centred broader component, that we identify as halo and ICL, respectively. Halo and ICPN have different spatial distributions: the halo PNs follow the galaxy's light, whereas the ICPNs are characterised by a shallower power-law profile. The composite PN number density profile shows the superposition of different PN populations associated with the M87 halo and the ICL, characterised by different PN alpha-parameters, the ICL contributing ~3 times more PNs per unit light. Down to m_5007=28.8, the M87 halo PN luminosity function (PNLF) has a steeper slope towards faint magnitudes than the IC PNLF, and both are steeper than the standard PNLF for the M31 bulge. Moreover, the IC PNLF has a dip at ~1-1.5 mag fainter than the bright cutoff, reminiscent of the PNLFs of systems with extended star formation history. The M87 halo and the Virgo ICL are dynamically distinct components with different density profiles and velocity distribution. The different alpha values and PNLF shapes of the halo and ICL indicate distinct parent stellar populations, consistent with the existence of a gradient towards bluer colours at large radii. These results reflect the hierarchical build-up of the Virgo cluster.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑