Satellites around Edge-on Galaxies. I. Dynamical Masses

Abstract

We have undertaken a search for satellites around edge-on galaxies in the EGIPS catalog, which contains 16 551 objects with declinations above  \(-30^{\circ}\) . We searched for systems with a central galaxy dominating in brightness by at least \(1^{\textrm{m}}\) compared to its companions. As a result, we discovered 1097 candidate satellites around 764 EGIPS galaxies with projected distances less than 500 kpc and a radial velocity difference less than 300 km s \({}^{-1}\) . Of these, 757 satellites around 547 central galaxies have radial velocity accuracies higher than 20 km s \({}^{-1}\) and satisfy the gravitationally bound condition. The ensemble of satellites is characterized by an average projected distance of 84 kpc and an average radial velocity dispersion of 103 km s \({}^{-1}\) . Treating small satellites as test particles moving on isotropic orbits around central EGIPS galaxies, we determined the projected (orbital) masses of the edge-on galaxies. Within the luminosity range of \(1.3\times 10^{10}\) to \(42\times 10^{10}\)   \(L_{\odot}\) , the total mass of the systems is well described by a linear dependence \(\log M_{p}\propto 0.88\log\left\langle L_{K}\right\rangle_{\textrm{g}}\) with an average total mass-to- \(K\) -band luminosity equal to \((17.5\pm 0.8) M_{\odot}/L_{\odot}\) , which is typical for nearby spiral galaxies such as the Milky Way, M 31 and M 81.