Interstellar H-Alpha Line Profiles toward HD 93521 and the Lockman Window

We have used the Wisconsin H-Alpha Mapper (WHAM) facility to measure the interstellar H-Alpha emission toward the high Galactic latitude O star HD 93521 (l = 183.1, b = +62.2). Three emission components were detected having radial velocities of -10 km s^{-1}, -51 km s^{-1}, and -90 km s^{-1} with respect to the local standard of rest (LSR) and H-Alpha intensities of 0.20 R, 0.15 R, and 0.023 R, respectively, corresponding to emission measures of 0.55 cm^{-6} pc, 0.42 cm^{-6} pc, and 0.06 cm^{-6} pc. We have also detected an H-Alpha emission component at -1 km s^{-1} (LSR) with an intensity of 0.20 R (0.55 cm^{-6} pc) toward the direction l = 148.5, b = +53.0, which lies in the region of exceptionally low H I column density known as the Lockman Window. In addition, we studied the direction l = 163.5, b = +53.5. Upper limits on the possible intensity of Galactic emission toward this direction are 0.11 R at the LSR and 0.06 R at -50 km s^{-1}. We also detected and characterized twelve faint (~0.03-0.15 R), unidentified atmospheric lines present in WHAM H-Alpha spectra. Lastly, we have used WHAM to obtain [O I] 6300 spectra along the line of sight toward HD 93521. We place an upper limit of 0.060 R on the [O I] intensity of the -51 km s^{-1} component. If the temperature of the gas is 10,000 K within the H-Alpha emitting region, the hydrogen ionization fraction n(H+)/n(H_total) > 0.6.Comment: 23 pages, 4 figures. Acccepted for publication in the 1 Feb issue of The Astronomical Journa

Sodium Atoms in the Lunar Exotail: Observed Velocity and Spatial Distributions

The lunar sodium tail extends long distances due to radiation pressure on sodium atoms in the lunar exosphere. Our earlier observations measured the average radial velocity of sodium atoms moving down the lunar tail beyond Earth (i.e., near the anti-lunar point) to be ~ 12.5 km/s. Here we use the Wisconsin H-alpha Mapper to obtain the first kinematically resolved maps of the intensity and velocity distribution of this emission over a 15 x 15 deg region on the sky near the anti-lunar point. We present both spatially and spectrally resolved observations obtained over four nights bracketing new Moon in October 2007. The spatial distribution of the sodium atoms is elongated along the ecliptic with the location of the peak intensity drifting 3 deg east along the ecliptic per night. Preliminary modeling results suggest the spatial and velocity distributions in the sodium exotail are sensitive to the near surface lunar sodium velocity distribution. Future observations of this sort along with detailed modeling offer new opportunities to describe the time history of lunar surface sputtering over several days

WHAM Observations of H-Alpha, [S II], and [N II] toward the Orion and Perseus Arms: Probing the Physical Conditions of the Warm Ionized Medium

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.Comment: 28 pages, 10 figures. Figures 2 and 3 are full color--GIFs provided here, original PS figures at link below. Accepted for publication in ApJ. More information about the WHAM project can be found at http://www.astro.wisc.edu/wham/ . REVISION: Figure 6, bottom panel now contains the proper points. No other changes have been mad