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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.
