The paper by Ferrarese and Merritt explores the fundamental relationship between the masses of supermassive black holes (SMBHs) and the velocity dispersions of their host galaxies. They find a nearly perfect correlation, \( M_{\bullet} \propto \sigma^{\alpha} \), with \( \alpha = 4.8 \pm 0.5 \), where \( M_{\bullet} \) is the SMBH mass and \( \sigma \) is the central velocity dispersion of the host bulge. This correlation is much tighter than the relationship between \( M_{\bullet} \) and bulge luminosity, suggesting a strong link between black hole formation and the properties of the stellar bulge. The authors analyze two samples of galaxies: Sample A, which includes galaxies with well-determined SMBH masses, and Sample B, which includes less secure mass estimates. Sample A shows a tight linear relation with negligible intrinsic scatter, while Sample B defines a weaker correlation. The tight correlation in Sample A suggests that the central velocity dispersion may be the fundamental parameter regulating the evolution of SMBHs in galaxies. The paper also discusses the implications of this correlation, including the discrepancy between Magorrian et al.'s mass estimates and the tighter correlation found by Ferrarese and Merritt. They suggest that the discrepancy may be due to systematic biases in the Magorrian et al. estimates, particularly at high masses and large distances. The authors caution against extrapolating the correlation to dwarf elliptical galaxies or globular clusters, as the formation mechanisms of SMBHs in these systems might differ. Finally, the paper explores possible explanations for the tight correlation, including a fundamental connection between SMBH mass and bulge mass, and the influence of the potential well depth in which the SMBH formed. The authors conclude that the central velocity dispersion is a robust predictor of SMBH mass, providing valuable insights into the formation and evolution of both SMBHs and their host galaxies.The paper by Ferrarese and Merritt explores the fundamental relationship between the masses of supermassive black holes (SMBHs) and the velocity dispersions of their host galaxies. They find a nearly perfect correlation, \( M_{\bullet} \propto \sigma^{\alpha} \), with \( \alpha = 4.8 \pm 0.5 \), where \( M_{\bullet} \) is the SMBH mass and \( \sigma \) is the central velocity dispersion of the host bulge. This correlation is much tighter than the relationship between \( M_{\bullet} \) and bulge luminosity, suggesting a strong link between black hole formation and the properties of the stellar bulge. The authors analyze two samples of galaxies: Sample A, which includes galaxies with well-determined SMBH masses, and Sample B, which includes less secure mass estimates. Sample A shows a tight linear relation with negligible intrinsic scatter, while Sample B defines a weaker correlation. The tight correlation in Sample A suggests that the central velocity dispersion may be the fundamental parameter regulating the evolution of SMBHs in galaxies. The paper also discusses the implications of this correlation, including the discrepancy between Magorrian et al.'s mass estimates and the tighter correlation found by Ferrarese and Merritt. They suggest that the discrepancy may be due to systematic biases in the Magorrian et al. estimates, particularly at high masses and large distances. The authors caution against extrapolating the correlation to dwarf elliptical galaxies or globular clusters, as the formation mechanisms of SMBHs in these systems might differ. Finally, the paper explores possible explanations for the tight correlation, including a fundamental connection between SMBH mass and bulge mass, and the influence of the potential well depth in which the SMBH formed. The authors conclude that the central velocity dispersion is a robust predictor of SMBH mass, providing valuable insights into the formation and evolution of both SMBHs and their host galaxies.