GeminiFocus January 2019 | Page 8

Figure 2. The non-detection of planetary candidates is interesting because it was unexpected. Using the occurrence rate of gi- ant planets on wide orbits that was inferred by pre- vious surveys — which assume that the mass function at wide separa- tion rises for lower mass- es as it does for closer-in planets found by radial velocity — we expected to discover between five to eight new planets. The survey’s null result is not due to a lack of sensitiv- ity, as the expected depth was reached. Example of a planetary candidate (circled) around a young star. Clockwise starting from upper left, we see an image at 0.9 µm (CFHT, MegaCam), at 1.2 µm (Gemini-S, F2), at 3.6 µm (Spitzer), and at 4.5 µm (Spitzer). This candidate turned out to be a background object. Credit: Frédérique Baron. Figure 3. Average completeness map for the WEIRD survey. Our results are shown in shades of magenta and the contours correspond to the probability of detecting a planet of a given mass and semi- major axis. The various boxes correspond to the range in masses and semi-major axes where the surveys from other teams were sensitive. All of the dotted boxes used high contrast imaging, while the solid boxes used deep seeing-limited imaging. Our observations probe larger semi-major axes than high contrast imaging surveys, but are insensitive to semi-major axes where high contrast observations are mostly sensitive. 6 but we identified all as background objects through follow-up proper motion observa- tions. Figure 2 shows an example of such a candidate, where you can see the very red color in z-J, as the candidate (circled) is bare- ly seen in z (top left image) but is very well detected in J (top right image). GeminiFocus Figure 3 shows in shades of magenta the average contrast map obtained for the sur- vey. It shows the probability of detecting a planet with a given mass between 1 and 13 M Jup as a function of the planet semi-major axis. The survey reaches good completeness for companions with masses down to 2 M Jup January 2019