Thesis Figures


Chapter 4: Scattering Investigation



A map of the WISP1/IRAS 100µm color ratio, with a resolution of ~6' (7x7 smoothing for WISP). Values have been scaled arbitrarily. High ratios are shown in blue, corresponding to blue colors, and low ratios are shown in red, corresponding to red colors. While data values within the inner WISP PSF regions around the major stars have been masked out, noisy data has not. Noise combined with background subtraction difficulties in the lower left quadrant of the WISP1 data (see Fig. \ref{Fig:wisp_snr_mskd}) make colors in this area very unreliable. In general, S/N grows poorer as distance from the cluster center increases.



A map of the WISP2/IRAS 100µm color ratio, with a resolution of ~6' (7x7 smoothing for WISP). Values have been scaled arbitrarily. High ratios are shown in blue, corresponding to blue colors, and low ratios are shown in red, corresponding to red colors. While data values within the inner WISP PSF regions around the major stars have been masked out, noisy data has not. In general, S/N grows poorer as distance from the cluster center increases.



A map of the Bj/IRAS 100µm color ratio, with a resolution of ~6' (7x7 smoothing for WISP). Values have been scaled arbitrarily. High ratios are shown in blue, corresponding to blue colors, and low ratios are shown in red, corresponding to red colors. Data values within the inner WISP PSF regions around the major stars have been masked out. In this case, both the Schmidt and IRAS observations had adequate sensitivity to keep noise from being a real concern. Uncertainties in these colors are dominated instead by systematic effects, principally low-level background matching errors between Schmidt fields.



A map of the WISP1/WISP2 color ratio in the nebula, with a resolution of ~6' (7x7 smoothing for WISP). Values have been scaled arbitrarily. High ratios are shown in blue, corresponding to blue colors, and low ratios are shown in red, corresponding to red colors. While data values within the inner WISP PSF regions around the major stars have been masked out, noisy data has not. Noise combined with background subtraction difficulties in the lower left quadrant of the WISP1 data (see Fig. \ref{Fig:wisp_snr_mskd}) make colors in this area very unreliable. In general, S/N grows poorer as distance from the cluster center increases.



A map of the WISP2/Bj color ratio, with a resolution of ~6' (7x7 smoothing for WISP). Values have been scaled arbitrarily. High ratios are shown in blue, corresponding to blue colors, and low ratios are shown in red, corresponding to red colors. While data values within the inner WISP PSF regions around the major stars have been masked out, noisy data has not. In general, S/N grows poorer as distance from the cluster center increases.



Grid positions indicating the subregions where data are extracted to produce color-color scatterplots (Figs. \ref{Fig:w1_w2_vs_w2_bj_grid} & \ref{Fig:w2_bj_vs_bj_ir_grid}). The maps overplotted by the grid are: Top Left: WISP1/WISP2 ratio map; Top Right: WISP2/Bj; Bottom Left: Bj/IRAS 100µm; and Bottom Right: Bj alone, for basic identification of stars and nebular features. All three ratio maps have a resolution of ~10' (15x15 smoothing for WISP).



(WISP1/WISP2) vs. (WISP2/Bj) color-color scatterplots for each region of the grid shown in Fig. \ref{Fig:gridloc}. The ratio values are scaled arbitrarily. All points plotted meet a S/N >= 3 criterion at their location in the WISP images. The top and right axes are labeled in [1950] Right Ascension (hours) and Declination (degrees) to indicate the approximate center coordinates of each grid region.



(WISP2/Bj) vs. (Bj/IRAS 100µm) color-color scatterplots for each region of the grid shown in Fig. \ref{Fig:gridloc}. The ratio values are scaled arbitrarily. All points plotted meet a S/N >= 3 criterion at their location in the WISP images. The top and right axes are labeled in [1950] Right Ascension (hours) and Declination (degrees) to indicate the approximate center coordinates of each grid region.



Phase function values for the WISP2 data, calculated from a single-scattering model. Values shown range linearly from 0.0 to 0.1, and represent the fraction of total scattered light which is scattered toward the observer at each position, integrated over the solid angle of each pixel. Contours are plotted from 0.0 to 0.1, at intervals of 0.01. The values shown here are typically a factor of ~3 less than those calculated for the Schmidt data, shown in Figure \ref{Fig:bj_alpha}. WISP1 phase function values are in the same approximate range.



Phase function values for the Bj data, calculated from a single-scattering model. Values shown range linearly from 0.0 to 0.3, and represent the fraction of total scattered light which is scattered toward the observer at each position, integrated over the solid angle of each pixel. Contours are plotted from 0.0 to 0.3, at intervals of 0.01. Note the contour interval in this figure is the same as that in Figure \ref{Fig:w2_alpha}, but the data range is three times larger. The values shown here are typically a factor of 3 greater than those calculated for the WISP1 and WISP2 data.



theta values for the Bj data, calculated with extinction cross-sections, albedos, and phase function asymmetries from the MRN grain model (Mathis, Rumpl, & Nordsieck 1977; White 1979). Values shown range linearly from 0° (no deflection) to 180° (complete backscatter), with the color red marking scattering angles of >~90°. Contours are plotted from 0° to 180° at 10° intervals, with the theta = 70° contour being the smallest enclosing Alcyone with several other bright Pleiads to the northwest.



Depth (line-of-sight displacement) values for the Bj data, calculated from theta map (Fig. \ref{Fig:bj_theta}) and assumed illuminator position. Values shown range linearly from 0 to 1 parsec, measured out from the illuminating star(s) back toward the observer. For reference, the area of the named Pleiades stars is ~2.5 pc from east to west. Contours are plotted from 0.0 to 1.0 pc at intervals of 0.1 pc. Top: Depth calculated assuming Alcyone is the sole illuminator. Bottom: Depth calculated assuming the area corresponding to a given pixel is illuminated solely by the named Pleiad (16, 17, 18, 19, 20, 21, 22, 23, 25, 27, or 28 Tauri) which appears brightest from that position. Note in neither case are outlying regions such as those to the northeast producing depths similar to what is found in the cluster; it thus appears that the majority of the light in these areas is scattered from local sources.