Low-scale mirror standard model dark matter and its detection via gravitational waves and the Guitar Nebula

What if the dark matter sector is truly dark, self-interacting, and unreachable by terrestrial experiments? How could we find hints of such dark sector if it is experimentally unreachable by any terrestrial experiment? In this work we study a low-scale mirror standard model that can act as a model for dark matter, which interacts only gravitationally with the standard model particles. The mirror standard model sector particles are stable particles that can comprise a measurable part of the dark matter of the Universe. These mirror standard model particles acquire mass through a low-temperature dark first order phase transition. We examine in detail this dark phase transition and we indicate how stochastic gravitational waves can be generated through this transition. Such a phase transition can generate stochastic gravitational waves that can be detected by the future gravitational wave experiments. For the model we use, the produced energy spectrum of the gravitational waves can be detected by the Square Kilometer Array. Moreover, we propose a possible way to detect effects of the particle nature of dark matter, using observational data coming from the Guitar Nebula, which can work if dark matter is collisional, so interacting dark matter. Without specifying a model for interacting dark matter, thus choosing an agnostic approach for interacting dark matter, we assume that the Guitar Nebula bow shock is generated by the interaction of the high-speed neutron star that passes through the interstellar medium, which is assumed to be composed of interacting dark matter and hydrogen. Our main proposal is that the opening angle of the bow shock can be directly related to the speed of sound of the dark matter particles, and a large angle of the bow shock could be a strong indicator that the interstellar medium is comprised by collisional dark matter and hydrogen gas. This is motivated by the Bosma effect, which indicates that hydrogen is always in correlation with dark matter, and hydrogen gas is strongly present in the Guitar Nebula.