S. L. Tufte

We quantify the level of foreground contamination in the QMAP cosmic microwave background data with two objectives: (1) to measure the level to which the QMAP power spectrum measurements need to be corrected for foregrounds and (2) to use this data set to further refine current foreground models. We cross-correlate the QMAP data with a variety of foreground templates. The 30 GHz Ka-band data are found to be significantly correlated with the Haslam 408 MHz and Reich & Reich 1420 MHz synchrotron maps but not with the Diffuse Infrared Background Experiment 240, 140, and 100 μm maps or the Wisconsin H-Alpha Mapper survey. The 40 GHz Q band has no significant template correlations. We discuss the constraints that this places on synchrotron, free-free, and dust emission. We also reanalyze the foreground-cleaned Ka-band data and find that the two band power measurements are lowered by 2.3% and 1.3%, respectively.

Spatial variations of the [S II]/H-Alpha and [N II]/H-Alpha line intensity ratios observed in the gaseous halo of the Milky Way and other galaxies are inconsistent with pure photoionization models. They appear to require a supplemental heating mechanism that increases the electron temperature at low densities n_e. This would imply that in addition to photoionization, which has a heating rate per unit volume proportional to n_e^2, there is another source of heat with a rate per unit volume proportional to a lower power of n_e. One possible mechanism is the dissipation of interstellar plasma turbulence, which according to Minter & Spangler (1997) heats the ionized interstellar medium in the Milky Way at a rate ~ 1x10^-25 n_e ergs cm^-3 s^-1. If such a source were present, it would dominate over photoionization heating in regions where n_e < 0.1 cm^-3, producing the observed increases in the [S II]/H-Alpha and [N II]/H-Alpha intensity ratios at large distances from the galactic midplane, as well as accounting for the constancy of [S II]/[N II], which is not explained by pure photoionization. Other supplemental heating sources, such as magnetic reconnection, cosmic rays, or photoelectric emission from small grains, could also account for these observations, provided they supply to the warm ionized medium ~ 10^-5 ergs s^-1 per cm^2 of Galactic disk.

A large portion of the Galaxy (l \ 123¡¨164¡, b \( 6¡ to (35¡), which samples regions of the Local (Orion) spiral arm and the more distant Perseus arm, has been mapped with the Wisconsin Ha Mapper (WHAM) in the (S II) j6716 and (N II) j6583 lines. By comparing these data with the maps from the WHAM Ha Sky Survey, we begin an investigation of the global physical properties of the warm ionized medium (WIM) in the Galaxy. Several trends noticed in emission-line investigations of diÜuse gas in other galaxies are con—rmed in the Milky Way and extended to much fainter emission. We —nd that the (S II)/Ha and (N II)/Ha ratios increase as absolute Ha intensities decrease. For the more distant Perseus arm emission, the increase in these ratios is a strong function of Galactic latitude, b, and thus of height, z, above the Galactic plane, while the (S II)/(N II) ratio is relatively independent of Ha intensity. Scatter in this ratio appears to be physically signi—cant, and maps of (S II)/(N II) suggest that regions with similar ratios are spatially correlated. The Perseus arm (S II)/(N II) ratio is systematically lower than local emission by 10%¨20%. With (S II)/(N II) fairly constant over a large range of Ha intensities, the increase of (S II)/Ha and (N II)/Ha with o z o seems to re—ect an increase in temperature. Such an inter- pretation allows us to estimate the temperature and ionization conditions in our large sample of obser- vations. We —nd that WIM temperatures range from 6000 to 10,000 K, with temperature increasing from bright to faint Ha emission (low to high (S II)/Ha and (N II)/Ha), respectively. Changes in (S II)/(N II) appear to re—ect changes in the local ionization conditions (i.e., the S'/S'' ratio). We also measure the electron scale height in the Perseus arm to be 1.0 ^ 0.1 kpc, con—rming earlier, less accurate determi- nations. Subject headings: Galaxy: haloH II regionsISM: atomsISM: structure

A large portion of the Galaxy (l = 123 deg to 164 deg, b = -6 deg to -35 deg), which samples regions of the Local (Orion) spiral arm and the more distant Perseus arm, has been mapped with the Wisconsin H-Alpha Mapper (WHAM) in the H-Alpha, [S II] 6716, and [N II] 6583 lines. Several trends noticed in emission-line investigations of diffuse gas in other galaxies are confirmed in the Milky Way and extended to much fainter emission. We find that the [S II]/H-Alpha and [N II]/H-Alpha ratios increase as absolute H-Alpha intensities decrease. For the more distant Perseus arm emission, the increase in these ratios is a strong function of Galactic latitude and thus, of height above the Galactic plane. The [S II]/[N II] ratio is relatively independent of H-Alpha intensity. Scatter in this ratio appears to be physically significant, and maps of it suggest regions with similar ratios are spatially correlated. The Perseus arm [S II]/[N II] ratio is systematically lower than Local emission by 10%-20%. With [S II]/[N II] fairly constant over a large range of H-Alpha intensities, the increase of [S II]/H-Alpha and [N II]/H-Alpha with |z| seems to reflect an increase in temperature. Such an interpretation allows us to estimate the temperature and ionization conditions in our large sample of observations. We find that WIM temperatures range from 6,000 K to 9,000 K with temperature increasing from bright to faint H-Alpha emission (low to high [S II]/H-Alpha and [N II]/H-Alpha) respectively. Changes in [S II]/[N II] appear to reflect changes in the local ionization conditions (e.g. the S+/S++ ratio). We also measure the electron scale height in the Perseus arm to be 1.0+/-0.1 kpc, confirming earlier, less accurate determinations.

During the initial data reduction of the Wisconsin H-Alpha Mapper (WHAM) H-Alpha Sky Survey, we have discovered several very long (~30--80 deg) filaments superimposed on the diffuse H-Alpha background. These features have no clear correspondence to the other phases of the interstellar medium revealed by 21 cm, X-ray, IR, or radio continuum surveys, and they have no readily identifiable origin or source of ionization. In this letter, the data for two of these faint (I_{H-Alpha} = 0.5--1.5 R) structures are presented. The first is an 80 deg-long, 2 deg-wide arch that extends nearly perpendicular to the Galactic plane at l = 225 deg and attains a maximum latitude of +51 deg near l = 240 deg. Where this feature appears to meet the Galactic plane near l = 225 deg, it is directly above the H II region surrounding CMa R1/OB1. A second filament consists of a ~25--30 deg-long arc spanning l = 210--240 deg at b = +30 deg to +40 deg. Both features have measurable velocity trends with position. However, they have rather constant intensities along their entire lengths, ranging from 0.5--1.5 R (EM = 1--3 cm^{-6} pc) with no obvious trends.