Predicting halo formation time using machine learning

Open Access

Table 2

Properties for the BCG and ICL region identified using the 50 h⁻¹ kpc aperture radius for training the RF regressor.

Property	Description	Units
$\frac{M_{B C G}}{I C L}$ $\frac{M_{BCG}}{ICL}$	The ratio between the total BCG mass computed within the 50 h⁻¹ kpc aperture 3D cut and the ICL stellar mass.	-
M_bh	The total mass of black hole particles at the center of the BCG.	h⁻¹ M_⊙
$M_{12} = \log_{10} (\frac{M_{B C G}}{M_{sub 2}})$ $M_{12} = \log_{10}\left(\frac{M_{BCG}}{M_{\text{sub}2}}\right)$	The logarithmic mass difference between the total BCG mass computed within the 50 h⁻¹ kpc aperture 3D cut and the most massive substructure. This is akin to the magnitude gap definition M 12.	-
$M_{14} = \log_{10} (\frac{M_{B C G}}{M_{sub 4}})$ $M_{14} = \log_{10}\left(\frac{M_{BCG}}{M_{\text{sub}4}}\right)$	The logarithmic mass difference between the total BCG mass computed within the 50 h⁻¹ kpc aperture 3D cut and the fourth massive substructure. This is akin to the magnitude gap definition M 14.	-
$\frac{M_{B C G}}{M_{s a t}}$ $\frac{M_{BCG}}{M_{sat}}$	The ratio between the total BCG stellar mass computed within the 50 h⁻¹ kpc aperture and the total satellite stellar mass of the halo.	-
dist	The three-dimensional distance between the center of the BCG and the center of mass calculated from all the satellite galaxies in terms of their stellar masses.	h⁻¹ kpc

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