We analyze a pair of Suzaku shadowing observations in order to determine the X-ray spectrum of the Galaxy ’ s gaseous halo .
Our data consist of an observation toward an absorbing filament in the southern Galactic hemisphere and an observation toward an unobscured region adjacent to the filament .
We simultaneously fit the spectra with models having halo , local , and extragalactic components .
The intrinsic intensities of the halo O vii triplet and O viii Lyman \alpha emission lines are 9.98 ^ { +1.10 } _ { -1.99 } ~ { } \textnormal { LU } ( line unit ; ~ { } \textnormal { photons } ~ { } \textnormal { cm } ^ { -2 } ~ { } \textnormal { s } ^ { -1 } ~ { } % \textnormal { sr } ^ { -1 } ) and 2.66 ^ { +0.37 } _ { -0.30 } ~ { } \textnormal { LU } , respectively .
These results imply the existence of hot gas with a temperature of \sim 10 ^ { 6.0 } ~ { } \textnormal { K } to \sim 10 ^ { 7.0 } ~ { } \textnormal { K } in the Galactic halo .
Meanwhile , FUSE O vi observations for the same directions and SPEAR C iv observations for a nearby direction indicate the existence of hot halo gas at temperatures of \sim 10 ^ { 5.0 } ~ { } \textnormal { K } to \sim 10 ^ { 6.0 } ~ { } \textnormal { K } .
This collection of data implies that the hot gas in the Galactic halo is not isothermal , but its temperature spans a relatively wide range from \sim 10 ^ { 5.0 } ~ { } \textnormal { K } to \sim 10 ^ { 7.0 } ~ { } \textnormal { K } .
We therefore construct a differential emission measure ( DEM ) model for the halo ’ s hot gas , consisting of two components .
In each , d \textnormal { EM } / d \log T is assumed to follow a power-law function of the temperature and the gas is assumed to be in collisional ionizational equilibrium .
The low-temperature component ( LTC ) of the broken power-law DEM model covers the temperature range of 10 ^ { 4.80 } -10 ^ { 6.02 } ~ { } \textnormal { K } with a slope of 0.30 and the high-temperature component ( HTC ) covers the temperature range of 10 ^ { 6.02 } -10 ^ { 7.02 } ~ { } \textnormal { K } with a slope of -2.21 .
We compare our observations with predictions from models for hot gas in the halo .
The observed spatial distribution of gas with temperatures in the range of our HTC is smoother than that of the LTC .
We thus suggest that two types of sources contribute to our broken power-law model .
We find that a simple model in which hot gas accretes onto the Galactic halo and cools radiatively can not explain both the observed UV and X-ray portions of our broken power-law model .
It can , however , explain the intensity in the Suzaku bandpass if the mass infall rate is 1.35 \times 10 ^ { -3 } ~ { } \textnormal { M } _ { \odot } ~ { } \textnormal { yr } ^ { -1 } ~ { } % \textnormal { kpc } ^ { -2 } .
The UV and X-ray intensities and our broken power-law model can be well explained by hot gas produced by supernova explosions or by supernova remnants supplemented by a smooth source of X-rays .