ON THE OFFSET OF BARRED GALAXIES FROM THE BLACK HOLE MBH–σ RELATIONSHIP
ON THE OFFSET OF BARRED GALAXIES FROM THE BLACK HOLE MBH–σ RELATIONSHIP
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DOI：
10.1088/0004-637x/778/2/151
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发表时间：
2013-05
期刊：
影响因子：
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通讯作者：
Jonathan S. Brown;M. Valluri;Juntai Shen;V. Debattista
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文献类型：
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作者：
Jonathan S. Brown;M. Valluri;Juntai Shen;V. Debattista
我们使用无碰撞N体模拟来确定超大质量黑洞（SMBH）的生长如何影响棒星系和非棒星系的核运动学。在存在棒的情况下，由于SMBH的增长，速度色散σ（在有效半径内）的增加平均为10%，而在无棒星系中，这种增加仅为10%。在棒星系中，这种增加是由三个独立因素共同作用的结果：（1）方向和倾角效应;（2）棒的角动量传输导致中心质量密度增加;（3）SMBH附近恒星的垂直和径向速度各向异性增加。相比之下，在一个无棒星系的SMBH的增长导致在核的内部的速度分布变得不那么径向各向异性。SMBH生长后σ的增加对SMBH最终质量的10倍变化不敏感，表明是生长过程而不是实际SMBH质量以增加σ的方式改变了棒的演化。我们认为，使用轴对称恒星动力学模拟代码来测量棒星系中的SMBH质量可能会导致稍微高估的派生MBH，特别是如果一个恒定的M/L比假设。我们的结论是，在存在棒的情况下，黑洞的增长可能导致σ的增加，比轴对称系统中发生的增加大约大4%-8%。虽然在棒星系中由于SMBH增长而导致的σ的增加可能部分地解释了从椭圆星系和无棒星系中的经典凸起获得的MBH-σ关系中声称的棒星系和伪凸起的偏移，但它不足以解释所有的偏移。
We use collisionless N-body simulations to determine how the growth of a supermassive black hole (SMBH) influences the nuclear kinematics in both barred and unbarred galaxies. In the presence of a bar, the increase in the velocity dispersion σ (within the effective radius) due to the growth of an SMBH is on average ≲ 10%, whereas the increase is only ≲ 4% in an unbarred galaxy. In a barred galaxy, the increase results from a combination of three separate factors: (1) orientation and inclination effects; (2) angular momentum transport by the bar that results in an increase in the central mass density; and (3) an increase in the vertical and radial velocity anisotropy of stars in the vicinity of the SMBH. In contrast, the growth of the SMBH in an unbarred galaxy causes the velocity distribution in the inner part of the nucleus to become less radially anisotropic. The increase in σ following the growth of the SMBH is insensitive to a variation of a factor of 10 in the final mass of the SMBH, showing that it is the growth process rather than the actual SMBH mass that alters bar evolution in a way that increases σ. We argue that using an axisymmetric stellar dynamical modeling code to measure SMBH masses in barred galaxies could result in a slight overestimate of the derived MBH, especially if a constant M/L ratio is assumed. We conclude that the growth of a black hole in the presence of a bar could result in an increase in σ that is roughly 4%–8% larger than the increase that occurs in an axisymmetric system. While the increase in σ due to SMBH growth in a barred galaxy might partially account for the claimed offset of barred galaxies and pseudo bulges from the MBH–σ relation obtained for elliptical galaxies and classical bulges in unbarred galaxies, it is inadequate to account for all of the offset.