J/MNRAS/510/3449 KOI planets and KIC stars from Kepler DR25 (Bashi+, 2022)
Exoplanets in the Galactic context: planet occurrence rates in the thin disc,
thick disc, and stellar halo of Kepler stars.
Bashi D., Zucker S.
<Mon. Not. R. Astron. Soc. 510, 3449-3459 (2022)>
=2022MNRAS.510.3449B 2022MNRAS.510.3449B (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Galactic plane ; Stars, dwarfs ; Stars, F-type ;
Stars, G-type ; Stars, K-type ; Exoplanets ; Positional data ;
Stars, diameters ; Effective temperatures ; Space velocities ;
Abundances, [Fe/H] ; Populations, stellar
Keywords: methods: statistical - planets and satellites: general -
stars: abundances - stars: fundamental parameters -
stars: kinematics and dynamics
Abstract:
In order to gain a better understanding of planet formation and
evolution, it is important to examine the statistics of exoplanets in
the Galactic context. By combining information on stellar elemental
abundances and kinematics, we constructed separate samples of Kepler
stars according to their affiliation to the Galactic components of
thin disc, thick disc, and stellar halo. Using a Bayesian analysis
with conjugate priors, we then investigated how planet occurrence
rates differ in different regions of planet properties. We find that
young, slow, and metal-rich stars, associated mainly with the thin
disc, host on average more planets (especially close-in super Earths)
compared to the old, fast, and metal-poor thick disc stars. We further
assess the dependence between stellar properties such as spectral type
and metallicity, and planet occurrence rates. The trends we find agree
with those found by other authors as well. We argue that in the
Galactic context, these are probably not the main properties that
affect planet occurrence rates, but rather the dynamical history of
stars, and especially stellar age and kinematics, impact the current
distribution of planets in the Galaxy.
Description:
In the current study, we aim to move one step forward by examing
planet occurrence rates in a well-defined sample of Kepler FGK dwarf
stars, in their Galactic context. In the literature, there is
currently no exact method to affiliate stars of the solar
neighbourhood to either the thin disc, thick disc, or the stellar
halo. Therefore, in this work, we will define our sample by combining
information on both kinematics and element abundance. Our purpose is to
check quantitatively whether there is a difference in the population
of planets orbiting stars of different Galactic components and to
further investigate the impact of the individual stellar properties
(e.g. size, temperature, and iron content) as compared to their
Galactic context properties (kinematics, age, and α-enhancement)
in determining planet occurrence rates, (refer to section Introduction).
We began by cross matching the LAMOST DR5 DD-Payne sample (Xiang et
al. 2019ApJS..245...34X 2019ApJS..245...34X, Cat. J/ApJS/245/34) with the Kepler input
catalogue (KIC) (Mathur et al. 2017ApJS..229...30M 2017ApJS..229...30M, Cat.
J/ApJS/229/30) and Gaia EDR3 (Gaia Collaboration 2021A&A...649A...1G 2021A&A...649A...1G,
Cat. I/350). We then excluded low quality S/N ratio and spectral fits,
also binary and multiple star system are not treated. We limited our
analysis to FGK dwarfs with logg > 4, Teff = 4500-6500 K and
excluded metal-poor ([Fe/H] < -1) stars as suggested by Xiang et al.
(2019ApJS..245...34X 2019ApJS..245...34X, Cat. J/ApJS/245/34) in order to avoid the bias
caused by the limited training set of metal-poor stars they had used
in this region. After applying these cuts, we were left with a sample
of 15881 KIC stars as the table1.dat shows with both Galactic space
velocities relative to the Local Standard of Rest (LSR; ULSR, VLSR,
WLSR) as well as [Fe/H] and [α/Fe]. Thus, we defined our sample
of stars in the Galactic context as (i) thin disc stars only if they
where found to be within our GMM solar-α cluster with Pα > 0.8
and TD/D < 0.1; (ii) thick disc stars if they where found to be
within the α-enriched cluster with Pα < 0.2, TD/D > 2,
and TD/H > 1, and (iii) halo stars, if, TD/D > 10 and TD/H < 1. Our
final stellar sample consisted of 11401 thin-disc stars, 472
thick-disc stars, and 11 halo stars, (i.e all these informations are
available in the section 2.2 Stellar sample.
We based our planet sample on the KOI catalogue from the 25th data
release (DR25) of Kepler (Thompson et al. 2018ApJS..235...38T 2018ApJS..235...38T, Cat.
J/ApJS/235/38). We kept only KOIs that were associated with our parent
stellar catalogue, and that were designated as planet candidates with
a disposition score higher than 0.9. Out of this sample, we excluded
objects flagged as false positives. Using updated stellar radii from
Gaia DR2 (Gaia Collaboration 2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345) and the
transit depths listed in Kepler DR25, we revised the KOI planet radii.
Furthermore, we excluded from our sample grazing transiting planets with
b > 1 - Rp/R* as listed in the KOI catalogue (from NEA :
https://exoplanetarchive.ipac.caltech.edu/cgi-bin
/TblView/nph-tblView?app=ExoTbls&config=q1q17dr25_koi), and also
limited our sample to include only planet candidates with periods
P < 400 d and radii in the range Rp = 0.5 - 12 R⊕. In total as
presented in the table2.dat, our sample included 506 planet candidates
orbiting 369 planet-host stars, out of which 402 planets and 292 host
stars included in the thin-disc sample, eight planets and seven host
stars in the thick-disc sample and no detected planets in our stellar
halo sample, (i.e more informations in section 2.3 Planet sample).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 338 15881 KIC stellar sample properties
table2.dat 63 506 KOI planet candidates sample
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See also:
J/ApJS/229/30 : Revised stellar properties of Q1-17 Kepler targets
(Mathur+, 2017)
J/ApJS/235/38 : Kepler planetary cand. VIII. DR25 reliability
(Thompson+, 2018)
J/A+A/643/A106 : 55 close-in (P<100days) small planets list (Bashi+, 2020)
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/MNRAS/478/4513 : GALAH Survey DR2 (Buder+, 2018)
III/286 : APOGEE-2 DR17 final allStar catalog (Abdurro'uf+, 2022)
V/164 : LAMOST DR5 catalogs (Luo+, 2019)
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
J/ApJ/790/146 : Planets in Kepler's multi-transiting systems
(Fabrycky+, 2014)
J/ApJ/909/115 : Planets Across Space and Time (PAST). I. (Chen+, 2021)
J/ApJS/210/19 : Kepler planetary candidates. IV. 22 months (Burke+, 2014)
J/ApJS/245/34 : Abundances for 6 million stars from LAMOST DR5 (Xiang+,2019)
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView
/nph-tblView?app=ExoTbls&config=q1q17dr25_koi : NEA updated KOI catalogue
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 I8 --- KIC Kepler Input Catalog ID (kic) (1)
10- 20 F11.7 deg RAdeg Right ascension (J2000) (ra)
22- 32 F11.8 deg DEdeg Declination (J2000) (dec)
34- 40 F7.4 mas plx Parallax (parallax)
42- 47 F6.4 mas e_plx Mean error of plx (eparallax)
49- 59 F11.6 pc Rg Radius in galactocentric
coordinates (R_gal)
61- 73 F13.9 pc Z Z height in galactocentric coordinates
(Z_gal)
75- 79 F5.3 Rsun R* Star radius (R_s)
81- 85 F5.3 Rsun e_R* Mean error if R* (eR_s)
87- 95 F9.7 [cm/s2] logg Surface gravity (logg)
97- 107 F11.9 [cm/s2] e_logg Mean error of logg (elogg)
109- 117 F9.4 K Teff Effective temperature (Teff)
119- 128 F10.7 K e_Teff Mean error on Teff (eTeff)
130- 143 F14.9 km/s U The velocity component directed toward
the Galactic center (U_lsr) (2)
145- 156 F12.9 km/s e_U Mean error of U (dU_lsr)
158- 171 F14.9 km/s V The velocity component directed along the
direction of Galactic rotation
(V_lsr) (2)
173- 184 F12.9 km/s e_V Mean error of V (dV_lsr)
186- 197 E12.9 km/s W The velocity component directed
perpendicular to the Galactic plane
(W_lsr) (3)
199- 209 F11.9 km/s e_W Mean error of W (dW_lsr)
211- 221 E11.9 --- TD/D Probability for a star being classified
as a thick-disc star relative to it being
classified as a thin-disc star (TD_D)
223- 233 E11.9 --- e_TD/D Mean error of TD/D (eTD_D)
235- 249 F15.9 --- TD/H Probability for a star being classified
as a thick-disc star relative to it being
classified as a halo star (TD_H)
251- 264 F14.9 --- e_TD/H Mean error of TD/H (eTD_H)
266- 277 E12.9 [Sun] [Fe/H] Fe to H abundance [Fe/H] (Fe_H)
279- 289 F11.9 [Sun] e_[Fe/H] Mean error of [Fe/H] (eFe_H)
291- 302 E12.9 [Sun] [alpha/Fe] Abundance of alpha-elements (Alpha_Fe)
304- 314 F11.9 [Sun] e_[alpha/Fe] Mean error of [alpha/Fe] (eAlpha_Fe)
316- 326 E11.9 --- Palpha Elemental cluster affiliation
probabilities (P_Alpha) (4)
328- 338 E11.9 --- e_Palpha Mean error of Palpha (eP_Alpha)
--------------------------------------------------------------------------------
Note (1): Taken from Kepler Input Catalog KIC (Kepler Mission Team, Cat. V/133)
and Revised Stellar Properties of Kepler Targets DR25 (Mathur et al.
2017ApJS..229...30M 2017ApJS..229...30M, Cat. J/ApJS/229/30 .
Note (2): U, V, and W represent the three components of an object's space
velocity relative to the Local Standard of Rest (LSR). LSR is a frame
of reference that represents the average motion of stars in the solar
neighborhood, effectively the rotational velocity of the Milky Way
at the Sun's location. U is positive in the direction moving from
the Sun toward the center of the Galaxy, V positive means moving in
the same direction as the Galaxy's rotation and W is positive if
moving toward the north Galactic pole, (i.e refer to section 2.2
Stellar sample).
Note (3): We adopted the revised kinematic characteristics at different
Galactocentric radii (R) and heights (Z) as described in Chen et al.
(2021), and calculated the relative Galactic-component membership
probabilities of each individual star defined in equation 3 of the
section 2.2 Stellar sample like TD/D (thick-disc-to-thin-disc) and
TD/H (thick-disc-to-halo) using stellar populations Gaussian
distributions with velocities as the equation 1 of the same section
shows.
Note (4): From elemental abundance perspective, following Blancato et al.
(2019ApJ...883...34B 2019ApJ...883...34B) and Bashi et al. (2020A&A...643A.106B 2020A&A...643A.106B,
Cat. J/A+A/643/A106), we used a Gaussian Mixture Model (GMM)
classifier and fixed the number of clusters to two in order to
capture the bimodality in the [Fe/H]-[α/Fe] plane. Consequently,
each point is affiliated with one of the two clusters with some
probability Pα, where values closer to 1 suggest higher
probability to belong to the solar-α cluster while values closer
to 0 suggest higher probability to belong to the α-enriched
cluster. It is important to note that as we consider uncertainties in
the stellar elemental content in our final planet occurrence rate
estimates (as opposed to Bashi et al. 2020A&A...643A.106B 2020A&A...643A.106B,
Cat. J/A+A/643/A106), Pα is also accompanied by an uncertainty
estimate, (i.e refer to section 2.2 Stellar sample).
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- KOI Kepler Object of Interest identifier
as K0NNNN.NN (koi) (1)
14- 26 F13.9 d Period Orbital Period (period)
28- 38 F11.9 d e_Period Mean error of the period (eperiod)
40- 51 F12.9 Rgeo Rp Planetary radius revisited (rp) (2)
53- 63 F11.9 Rgeo e_Rp Mean error of Rp (erp)
--------------------------------------------------------------------------------
Note (1): Systems (integer part of KOI numbers) ordered by increasing
multiplicity, then numerically. Within each system, planets are
ordered by increasing orbital period. The decimal part of KOI
numbers (".01", ".02", etc.) refers to the order of discovery.
Names are made as <KOI-NNNN.NN> in Simbad.
Note (2): Using updated stellar radii from Gaia DR2 (Gaia Collaboration
2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345) and the transit depths listed in
Kepler DR25 (Thompson et al. 2018ApJS..235...38T 2018ApJS..235...38T, Cat. J/ApJS/235/38
and also see the updated KOI Q1-17 DR 25 tables from NEA :
https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView
/nph-tblView?app=ExoTbls&config=q1q17dr25_koi), we then revised
the KOI planet radii.
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 12-Nov-2024