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An orbiting object in a gas rich environment creates a gravitational densitywake containing information about the object and its orbit. Using linearperturbation theory, we analyze the observable properties of the gravitationalwake due to the object circularly moving in a static homogeneous gaseousmedium, in order to derive the Bondi accretion radius $r_B$, the orbitaldistance $r_p$, and the Mach number of the object. Supersonic motion, producinga wake of spiral-onion shell structure, exhibits a single-armed Archimedesspiral and two-centered circular arcs with respect to the line of sight. Thepitch angle, arm width, and spacing of the spiral pattern are entirelydetermined by the orbital distance $r_p$ and Mach number of the object. Thearm-interarm density contrast is proportional to the Bondi accretion radius,decreasing as a function of distance with a power index of -1. The backgrounddensity distribution is globally changed from initially uniform to centrallyconcentrated. The vertical structure of the wake is manifested as circular arcswith the center at the object location. The angular extent of the arcs isdetermined by the Mach number of the object motion. Diagnostic probes ofnonlinear wakes such as a detached bow shock, an absence of the definite innerarm boundary, the presence of turbulent low density eddies, and elongatedshapes of arcs are explained in the extension of the linear analysis. Thedensity enhancement at the center is always $r_B/r_p$ independent of thenonlinearity, suggesting that massive objects can substantially modify thebackground distribution. These detailed understanding of the wakecharacteristics will provide an interpretative framework for both furthertheoretical works under more complicated situations and future observations todetect the gravitational wakes of hidden objects.

Gravitationally Induced Density Wake of a Circularly Orbiting Object As an Interpretative Framework of Ubiquitous Spirals and Arcs