2009ApJ...699..716C

The distribution of the H166α radio recombination line emission at the end of the first quadrant is obtained and compared with the distribution of H I and other young objects. The data analyzed lie in the Galactic longitude range between l = 60° and l = 91° and was observed with single dish antenna at 1.4 GHz. The extended low-density warm ionized medium (ELDWIM) is used to trace the Local Spur (LS), which is strongly correlated with neutral hydrogen and low-brightness H II regions. The Galactic distribution of gas in the (X, Y, z) Galactic coordinates yields the location of ionized hydrogen in an arclike structure at an almost constant distance of 8 kpc from the galactic center. The ELDWIM and the low-brightness H II region define the LS; it is located between r ≃ 0.5 and 5 kpc from the Sun. We found sources of ionized gas at larger distances; they are probably located in the Perseus arm. The structure of the LS does not seem to join the Perseus arm at farther distances, a fact gleaned from the H I emission. The LS is very thick between 2 and 5 kpc, where the ionized gas spreads from z ≃ -150 to +250 pc. The z distribution of the ionized gas appears tilted with respect to the Galactic plane, which starts at 3 kpc from the Sun and runs toward higher galactocentric radii on the Perseus arm.