Bent-double radio sources as probes of intergalactic gas

As the most common environment in the universe, groups of galaxies are likely to contain a significant fraction of the missing baryons in the form of intergalactic gas. The density of this gas is an important factor in whether ram pressure stripping and strangulation affect the evolution of galaxies in these systems. We present a method for measuring the density of intergalactic gas using bent-double radio sources that is independent of temperature, making it complementary to current absorption-line measurements. We use this method to probe intergalactic gas in two different environments, inside a small group of galaxies as well as outside of a larger group at a 2 Mpc radius, and measure total gas densities of 4 +/- 1(-2)(+6) x 10(-3) cm(-3) and 9 +/- 3(-5)(+10) x 10(-4) cm(-3) (random and systematic errors), respectively. We use X-ray data to place an upper limit of 2 x 10(6) K on the temperature of the intragroup gas in the small group.