Plot 1 - Sample Plot Alt Text
This plot aims to show the sample for the APO-K2 catalog as it appears on the sky. The plot is rectangular shaped with the x-axis about twice as long as the y-axis. The x-axis shows the Galactic Longitude, in units of degrees, between -150 and 150 degrees with 0 in the center of the x-axis. Similarly, the y-axis shows the Galactic Longitude, also in units of degrees, ranging from -75 at the bottom to 75 at the top; again, the center of the axis is 0. Both of the axes have text axis labels with 'Galactic Longitude (Degree)' on the x-axis and 'Galactic Latitude (Degree)' on the y-axis. None of the corners of the plot have numbers attached to them and the true scale of the x- and y-axis are a little more and a little less than the numbers stated.
There is a colorbar to the right-hand side of the plot, with vertical text reading 'Fe/H', corresponding to the metallicity of the stars shown in the plot. The scale runs from -1, right at the bottom of the colorbar, to 0.4 at the top, although the scale runs to 0.5. The lowest metallicity stars (at -1.0) correspond to a deep purple, this moves up through blue, teal, green, to yellow (at 0.5).
The plot itself shows a background of the Galactic plane, with the Galactic center at 0,0, in the center of the plot, and the Milky Way running from the left to right across the plot. The top and bottom of the image are black, corresponding to space outside the Galactic plane. As the y-axis moves closer to 0 at the center there is a line of dust, gas, and light as we reach the Galactic plane. The small and large Magellanic Clouds are seen to the bottom right of the Galactic center, about a third of the way between the plane and the bottom of the plot.
Overplotted on the background are the K2 campaigns, made up of points of color representing separate stars. Each campaign, loosely takes the shape of a Kepler field, which looks like an off-angle square with each corner having a smaller square removed. Each of the small points representing stars are colored consistent with their metallicity, represented by the colorbar.
The campaigns run from the left-hand to right-hand side of the plot, mostly equally spaced (with some overlapping) in the shape of a sine curve flipped on the x-axis. On the left, just below the Galactic plane are the campaign 13 stars, mostly made up of teal, slightly sub-solar metallicity stars. Campaign 13 is half off the plot, the other side of it being shown on the right-hand side. Overlapping the bottom right-hand corner of campaign 13 is campaign 4. Both oriented so that the Kepler 'square' looks more like a diamond. Further below the plane and to the right is campaign 8, which is darker blue than the previous two. To the right of this, and at around the same Galactic latitude is campaign 12 and just above this to the right is campaign 3. These are both roughly the same color as campaign 8, but are closer together. As the reflected sine curve starts to curve upwards toward the Galactic plane, we get to campaign 7, which is sparsely populated, and with a generally higher metallicity. It appears to be the least populated campaign that shares no overlap with other campaigns. As we move through the Galactic plane in the middle of the plot, we see campaign 11, above this is campaign 2, and above this is campaign 15, all on a diagonal upwards toward the right. These campaigns all overlap, are relatively sparsely populated, and have fairly metal-rich stars (relative to the rest of the campaigns). Above this to the right, and out of the Galactic plane, we see campaigns 6 and 17, with 6 underneath and 17 directly above, almost completely overlapping. These have similar metallicities to campaigns 8, 12, and 3, and are at similar distances above the Galactic plane, as the aforementioned were below it. Next, almost at the same Galactic latitude but reasonably spaced are campaigns 10, 1, and 14, each more populated than the last and with low metallicity overall. Finally, more towards the galactic plane, but still above it, are campaigns 16, 5, and 8, which all overlap and show relatively low metallicity.
Just above the Galactic plane, about half way between the left-hand side of the plot and the Galactic center is the Kepler field, showing a relatively high metallicity when compared to the majority of the K2 campaigns. It is the most populated on the plot, as all CCD modules are working in this mission. Each campaign, and the Kepler field, are labeled with white text with their campaign number as C followed by the number. The Kepler field is also labelled as 'Kepler'.
Plot 2 - H-R Diagram Alt Text
Almost two square plots side by side. Both have the same x- and y-axis with roughly the same limits. The y-axis is labeled Luminosity [L_sun] and the scale is in a log-space from 0 to ~400. The x-axis is labeled Effective Temperature [K] and is on a linear scale ranging from just below 5400 K to above 4200 K. None of the numbers are explicitly on the corners of the plots, and these limits vary slightly over and under the tick labels. There is a colorbar to the right of the two plots labeled [M/H] and shows the metallicity of the stars from just below -2.0 at the bottom up to just above 0.5 at the top. The colors scale ranges from white to dark blue, following through hues of blue on the way. The filled circles are all outlined in black, so that the low metallicity stars can be seen on a white background.
The plot on the left has a title stating 'Red Clump Stars: 2446' and a legend in the bottom left corner, indicating that cross markers represent the red giant stars and filled circles correspond to the red clump stars. The filled circles are far more prominent on the plot as these are the stars we want to show. The crosses lie under the filled circles and run from almost the left-hand corner of the plot to the top right. They have a width corresponding to around 200 K and this gets slightly thicker as the sequence moves to the top right. The crosses are roughly evenly distributed, although a clump of them is visible under the bottom filled circles. This corresponds to the red bump stars. The filled circles indicating the red clump stars start about half way across the plot, and about half way up the sequence of crosses. The majority of the points form almost a triangular shape, fanning out towards the left-hand side of the plot. These points are more dispersed at the upper and lower areas. They are a collection of hues, with the darker points (corresponding to more metal-rich stars) more towards the center, and the more metal-poor stars generally towards the middle and left-hand side of the red clump. There are a few stars removed from this fan shape, further towards the left-hand side of the plot. The larger stars (indicated by the size of the points) are towards the top of the plot and the top left, with the smaller stars in the clump or on the right of it, overlapping with the crosses. There is a collection of stars below the fan shape, indicative of the secondary red clump. Next to the legend at the bottom of the plot is a text box stating 'Point Sizes Indicative of Stellar Mass [M_sun]', and next to this is a representative error bar for the red clump stars, with spans ~10K in temperature and a couple of solar luminosities.
The left-hand plot shows the same as the right-hand plot, but in reverse, with the crosses indicating the red clump stars from the left-hand plot and the points representing the red giant stars, shown as crosses on the left. There is a similar legend in the bottom left corner showing that crosses are indicative of red clump stars and filled circles are indicative of red giant stars. There is also an error bar in the bottom right corner of the plot showing a smaller error for both luminosity and temperature for these stars. For the points themselves, the sequence is the same as described above but now the color and size of the points is evident. There is a larger abundance of metal-poor stars towards the warmer edge of the sequence. There is a clear edge to the sequence on the right with more scattering on the left, and a couple of points dotted about to the top right and to the right of the sequence. The bottom of the sequence is also very sharp. The sizes of the points are less varied that on the Red Clump plot but do show high mass stars toward the top left. There are also low metallicity stars in this area. The title of this plot reads 'Red Giant Stars: 4053', indicating the number of stars in the red giant sample shown on this plot.