We present a Hubble Space Telescope (HST) study of the nuclear region of the E4 radio galaxy NGC 7052, which has a nuclear disk of dust and gas. The Second Wide Field and Planetary Camera (WFPC2) was used to obtain B, V, and I broadband images and an Hα + [N II] narrowband image. The images yield the stellar surface brightness profile, the optical depth of the dust, and the flux distribution of the ionized gas. The Faint Object Spectrograph was used to obtain Hα + [N II] spectra at six different positions along the major axis, using a 026 diameter circular aperture. The emission lines yield the rotation curve of the ionized gas and the radial profile of its velocity dispersion. The observed rotation velocity at r = 02 from the nucleus is V = 155 ± 17 km s-1. The Gaussian dispersion of the emission lines increases from σ ≈ 70 km s-1 at r = 1'' to σ ≈ 400 km s-1 on the nucleus. To interpret the gas kinematics, we construct axisymmetric models in which the gas and dust reside in a disk in the equatorial plane of the stellar body and are viewed at an inclination of 70°. It is assumed that the gas moves on circular orbits, with an intrinsic velocity dispersion due to turbulence (or otherwise nongravitational motion). The latter is required to fit the observed increase in the line widths toward the nucleus and must reach a value in excess of 500 km s-1 in the central 01. The circular velocity is calculated from the combined gravitational potential of the stars and a possible nuclear black hole. Models without a black hole predict a rotation curve that is shallower than observed (Vpred = 92 km s-1 at r = 02) and are ruled out at greater than 99% confidence. Models with a black hole of mass Ma = 3.3 × 108 M☉ provide an acceptable fit. The best-fitting model with a black hole adequately reproduces the observed emission-line shapes on the nucleus, which have a narrower peak and broader wings than a Gaussian. NGC 7052 can be added to the list of active galaxies for which HST spectra of a nuclear gas disk provide evidence for the presence of a central black hole. The black hole masses inferred for M87, M84, NGC 6251, NGC 4261, and NGC 7052 span a range of a factor of 10, with NGC 7052 falling on the low end. By contrast, the luminosities of these galaxies are identical to within ~25%. Any relation between black hole mass and luminosity, as suggested by independent arguments, must therefore have a scatter of at least a factor of 10.
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机译：我们提出了哈勃太空望远镜（HST）对E4射电星系NGC 7052的核区域的研究，该星系具有尘埃和气体的核盘。第二个广角和行星相机（WFPC2）用于获取B，V和I宽带图像以及Hα+ [N II]窄带图像。这些图像产生了恒星表面的亮度分布，灰尘的光学深度以及电离气体的通量分布。使用026直径的圆形孔径，使用微弱物体光谱仪获得沿主轴的六个不同位置处的Hα+ [N II]光谱。发射线产生电离气体的旋转曲线及其速度分散的径向分布。从原子核在r = 02处观察到的旋转速度为V = 155±17 km s-1。发射线的高斯色散从r = 1''处的σ≈70 km s-1增加到原子核上的σ≈400 km s-1。为了解释气体运动学，我们构建了轴对称模型，其中气体和尘埃位于恒星体赤道平面的圆盘中，并以70°的倾斜角观察。假设气体在圆形轨道上运动，由于湍流（或非重力运动）而具有固有的速度分散。后者需要适合观察到的朝向核的线宽增加，并且必须在中心01处达到500 km s-1以上的值。圆周速度是根据恒星的重力总和和核黑洞。没有黑洞的模型预测的旋转曲线比观察到的要浅（在r = 02时Vpred = 92 km s-1），并且排除了大于99％的置信度。黑洞质量为Ma = 3.3×108M☉的模型提供了可接受的配合。具有黑洞的最佳拟合模型可以在核上充分再现观察到的发射线形状，与高斯相比，该发射线具有更窄的峰和更宽的翅膀。 NGC 7052可以添加到活动星系列表中，为此，核气盘的HST光谱可提供存在中心黑洞的证据。推断出的M87，M84，NGC 6251，NGC 4261和NGC 7052的黑洞质量范围是10的范围，而NGC 7052则位于低端。相比之下，这些星系的发光度在〜25％以内是相同的。独立论点表明，黑洞质量和光度之间的任何关系都必须具有至少10倍的散射。
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