The Tully-Fisher ( TF ) or the luminosity line-width relations of the galaxies in the Eridanus group are constructed using the H i rotation curves and the luminosities in the optical and in the near-infrared bands .
The slopes of the TF relations ( absolute magnitude vs log 2 V _ { flat } ) are -8.6 \pm 1.1 , -10.0 \pm 1.5 , -10.7 \pm 2.1 , and -9.7 \pm 1.3 in the R , J , H , and K bands respectively for galaxies having flat H i rotation curves .
These values of the slopes are consistent with those obtained from studies of other groups and clusters .
The scatter in the TF relations is in the range 0.5 - 1.1 mag in different bands .
This scatter is considerably larger compared to those observed in other groups and clusters .
It is suggested that the larger scatter in the TF relations for the Eridanus group is related to the loose structure of the group .
If the TF relations are constructed using the baryonic mass ( stellar + H i + Helium mass ) instead of the stellar luminosity , nearly identical slopes are obtained in the R and in the near-infrared bands .
The baryonic TF ( baryonic mass vs log 2 V _ { flat } ) slope is in the range 3.5 - 4.1 .