We recently proposed the Keck Planet Imager and Characterizer Concept and a phased implementation plan approved by the Keck Science Steering Committee. More details can be found in this white paper, and SPIE paper.

KPIC science cases

Exoplanets around late-type stars. M dwarfs constitute a promising reservoir to survey in order to advance our understanding of planetary formation and evolution. Indeed, M dwarfs outnumber all earlier-type stars together. Their abundance, low close binary fraction, and the ubiquitous presence of massive protoplanetary disks at young ages imply that they are common sites of planet formation. Close separations (< 1 AU) have been extensively probed by Doppler and transit surveys with the following results: the frequency of close-in giant planets (1 − 10MJup) is only 2.5 ± 0.9%, consistent with core accretion plus migration models.2 On the other hand, the Kepler survey indicates that Earth- to Neptune-sized planets might be as common as one per star.3–5 The outskirts of young M-dwarf systems (10 − 100 AU) have been probed by first-generation direct imaging instruments, and results show that massive planets are rare: fewer than 10.6% of M-dwarf systems surveyed harbor 1−13MJup giant planets in their outer regions.6 Disk instability does not seem to be a common mechanism of giant planet formation. The 1 − 10 AU parameter space is thus believed to be the overwhelmingly favored region for planet formation. Across the entire range of sensitivity (10M⊕ −10MJup), the occurrence rates measured by microlensing survey imply an average 1.6+0.7 planets per star7! Microlensing probes the full range of −0.9 planetary masses in this region, but the masses and metallicities of the host stars are usually poorly constrained and so are of limited value for statistical studies. Moreover, one-shot microlensing-detected objects can not be followed up. High contrast imaging with a good knowledge of the host star distance and age is therefore the perfect complement to indirect techniques, and holds the promise of filling in this untouched parameter space, and provide excellent characterization opportunities. Last but not least, M dwarfs provide the best star-planet contrast ratios among all stellar masses.

Planetary systems in star forming regions (SFR). Sky coverage with an IR WFS is typically 50% higher than with a classical visible WFS.12 In obscured areas such as SFR, the gain is much more dramatic. The population of young stars in Taurus, 140 pc away, is dominated by M stars and very late K stars,13 making IR WFS essential for these very red stars. Indeed, an R-band WFS sensitivity rolloff at R ≃ 10 currently provides access to only a handful of T Tauri stars, while a rolloff at J/H ≃ 10 mags would enable high contrast on a hundred young stars in Taurus alone. Thus, IR wavefront sensing enables high contrast imaging studies of extrasolar planetary systems (both disk + protoplanets) in their infancy.

Galactic center (GC). IR WFS has proven to be very robust to study the GC with VLT-NACO: IRS 7 (H = 9.3, K = 6.5) is only 6” North of SgrA∗. An IR WFS ExAO would boost the Strehl ratio (SR) by a factor of a few compared to current LGS assisted observations (10 − 30% SR at K), therefore enhancing SNR, enabling shorter wavelengths, and thus improving resolution and astrometric precision (reduced confusion).

Here we give a short overview of KPIC’s main modules:

© Dimitri Mawet 2017