On the mass density distribution of the inner galaxy

Extract

Based on current 2.4-micron observations of the Galaxy (see Okuda et al. in this Symposium), we have proposed a specific model for the bulge component. This model is a concentric spheroid with an axial ratio of ∼0.5; ρ(a)∞(a²+a_c²)⁻¹exp(-(a/a_o)²), where a_o = 2.5 kpc and a_c = 0.14 kpc respectively. A constant mass-to-luminosity ratio M/L_v≃7.6 is assumed, which yields the relevant rotational velocity in the inner region (Figure 1); the absolute velocity is normalized to 250 km s⁻¹. This value of M/L_v is likely to meet with giant-rich synthetic models for the nuclear bulge of M31.