Planets Across Space and Time (PAST). II. Catalog and Analyses of the LAMOST–Gaia–Kepler Stellar Kinematic Properties

Abstract

The Kepler telescope has discovered over 4000 planets (candidates) by searching ∼200,000 stars over a wide range of distance (order of kpc) in our Galaxy. Characterizing the kinematic properties (e.g., Galactic component membership and kinematic age) of these Kepler targets (including the planet candidate hosts) is the first step toward studying Kepler planets in the Galactic context, which will reveal fresh insights into planet formation and evolution. In this paper, the second part of the Planets Across the Space and Time (PAST) series, by combining the data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and Gaia and then applying the revised kinematic methods from PAST I, we present a catalog of kinematic properties (i.e., Galactic positions, velocities, and the relative membership probabilities among the thin disk, thick disk, Hercules stream, and the halo) as well as other basic stellar parameters for 35,835 Kepler stars. Further analyses of the LAMOST–Gaia–Kepler catalog demonstrate that our derived kinematic age reveals the expected stellar activity-age trend. Furthermore, we find that the fraction of thin (thick) disk stars increases (decreases) with the transiting planet multiplicity (N p = 0, 1, 2 and 3+) and the kinematic age decreases with N p, which could be a consequence of the dynamical evolution of planetary architecture with age. The LAMOST–Gaia–Kepler catalog will be useful for future studies on the correlations between the exoplanet distributions and the stellar Galactic environments as well as ages.

Planets Across Space and Time (PAST). III. Morphology of the Planetary Radius Valley as a Function of Stellar Age and Metallicity in the Galactic Context Revealed by the LAMOST-Gaia-Kepler Sample

“…Using the LAMOST-Gaia-Kepler kinematic catalogs provided by PAST II (Chen et al 2021b), we explored the radius valley morphology of small planets (1-6 R ⊕ ) in the Galactic context. Specifically, we define a set of metrics to quantify the radius valley morphology (Section 2.2) and investigate whether and how they are correlated with the properties of host stars, i.e., the relative membership probability between thick-and thin-disk stars (TD/D), the kinematic age, and metallicity, i.e., [Fe/H] and [α/Fe] (Section 3).…”

“…The observation biases, caused by the detection efficiency, also need to be considered. For example, the stellar activity and noise are anticorrelated to TD/D and age (Figures 5 and 6 of PAST II; Chen et al 2021b) and may affect the detection ability of planets. To control the stellar detection ability and noise level, here we In each panel, p denotes the p-value of the two-sample K-S test for the distributions of neighboring stars belonging to the last three bins compared to the first bins.…”

“…We initialized our stellar sample from the LAMOST-Gaia-Kepler catalog from PAST II (Chen et al 2021b), a total of 35,835 Kepler stars, including stellar hosts of 1060 Kepler planets (candidates). In addition to some basic stellar parameters (e.g., mass, radius, effective temperature, [Fe/H], [α/Fe]), the catalog provides stellar kinematic properties, such as the Galactic velocities and the derived relative membership probabilities among different Galactic components (TD/D, TD/H, Herc/D, Herc/TD), where D, TD, Herc, and H denote the thin disk, the thick disk, the Hercules stream, and the halo of the Milky Way, respectively.…”

“…In this paper, we address the age dependence from a different angle of view by using the kinematic age based on the LAMOST-Gaia-Kepler catalog (Chen et al 2021b). By defining a series of metrics, we systematically investigated how the radius valley morphology evolves with age.…”

“…In the first paper of PAST (hereafter PAST I; Chen et al 2021a), we extended the applicable range of the kinematic method for classification of Galactic components from the solar neighborhood (∼100-200 pc) to ∼1500 pc to cover most of planet hosts, and we refined the age-velocity dispersion relation (AVR) to derive kinematic ages of planet hosts with a typical uncertainty of ∼10%-20%. Applying the methods of PAST I, we constructed a LAMOST-Gaia-Kepler stellar catalog in the second paper of PAST (hereafter PAST II; Chen et al 2021b), which provides kinematic properties and other basic stellar properties of 35,835 Kepler stars, including hosts of 1061 Kepler planets (candidates). The LAMOST-Gaia-Kepler stellar catalog of PAST II allows us to reveal the effects of various stellar properties ([Fe/H], [α/Fe], and age) on the radius valley, respectively.…”