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arXiv 1906.10697astro-ph.GA
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矮星系中的AGN:频率、触发过程和AGN反馈的可解释性

AGN in dwarf galaxies: frequency, triggering processes and the plausibility of AGN feedback

Sugata Kaviraj, Garreth Martin, Joseph Silk

摘要:

虽然活动星系核被认为是大质量星系演化的关键驱动力,但它们在矮星系体系(M*< 10^9 MSun)中的潜在重要作用仍在很大程度上未被探索。我们结合来自超极凸轮(HSC)和宽视场红外探测器(WISE)的光学和红外数据,研究了低红移(z<0.3)矮星中~800活动星系核的性质。在矮星系中,被选中的活动星系核的比例约为10- 30%,对于合理的占空比,这表明BH占据比例很高。对深HSC图像的目视检查表明,矮活动星系核中的合并分数(约6%)与非活动星系核的对照样本相比没有过多,这表明活动星系核触发过程在本质上是长期的。能量参数表明,无论是矮星系还是大质量星系,活动星系核的辐射热光度(L_AGN)都明显大于超新星光度(L_SN)。事实上,在矮星中,L_AGN/L_SN更高,模拟的预测表明,这个比率只会随着红移而增加。再加上可能很高的黑洞占据率,这表明,如果活动星系核反馈是暗星系演化的重要驱动力,那么在矮星系中也可能是如此,这与我们的经典思想相反。

英文摘要:

While AGN are considered to be key drivers of the evolution of massive galaxies, their potentially significant role in the dwarf-galaxy regime (M*< 10^9 MSun) remains largely unexplored. We combine optical and infrared data, from the Hyper Suprime-Cam (HSC) and the Wide-field Infrared Explorer (WISE) respectively, to explore the properties of ~800 AGN in dwarfs at low redshift (z<0.3). Infrared-selected AGN fractions are ~10-30 per cent in dwarfs, which, for reasonable duty cycles, indicates a high BH-occupation fraction. Visual inspection of the deep HSC images indicates that the merger fraction in dwarf AGN (~6 per cent) shows no excess compared to a control sample of non-AGN, suggesting that the AGN-triggering processes are secular in nature. Energetic arguments indicate that, in both dwarfs and massive galaxies, bolometric AGN luminosities (L_AGN) are significantly greater than supernova luminosities (L_SN). L_AGN/L_SN is, in fact, higher in dwarfs, with predictions from simulations suggesting that this ratio only increases with redshift. Together with the potentially high BH-occupation fraction, this suggests that, if AGN feedback is an important driver of massive-galaxy evolution, the same is likely to be true in the dwarf regime, contrary to our classical thinking.

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