J/MNRAS/521/208 [M/H] of K/M dwarfs in SN kinematic structures (Medan+, 2023) ================================================================================ Chemodynamical ages of small-scale kinematic structures of the galactic disc in the solar neighbourhood from ~250000 K and M dwarfs. Medan I., Lepine S. =2023MNRAS.521..208M (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Stars, K-type ; Stars, M-type ; Stars, dwarfs ; Milky Way ; Stars, nearby ; Abundances ; Associations, stellar ; Positional data ; Space velocities Keywords: Galaxy: kinematics and dynamics - (Galaxy:) solar neighbourhood - stars: abundance Abstract: We combine photometric metallicities with astrometry from Gaia DR3 to examine the chemodynamic structure of ~250000 K dwarfs in the solar neighbourhood (SN). In kinematics, we observe ridges/clumps of 'kinematic groups', like studies of more massive main-sequence stars. Here, we note clear differences in both metallicity and vertical velocity as compared with the surrounding regions in velocity space and hypothesize this is due to differences in mean age. To test this, we develop a method to estimate the age distribution of subpopulations of stars. In this method, we use GALAH data to define probability distributions of W versus [M/H] in age bins of 2 Gyr and determine optimal age distributions as the best-fitting weighted sum of these distributions. This process is then validated using the GALAH subset. We estimate the probable age distribution for regions in the kinematic plane, where we find significant substructure that is correlated with the kinematic groups. Most notably, we find an age gradient across the Hercules streams that is correlated with birth radius. Finally, we examine the bending and breathing modes as a function of age. From this, we observe potential hints of an increase in the bending amplitude with age, which will require further analysis in order to confirm it. This is one of the first studies to examine these chemodynamics in the SN using primarily low-mass stars and we hope these findings can better constrain dynamical models of the Milky Way due to the increase in resolution the sample size provides. Description: For the purpose of our study, we firstly selected stars by photometric criteria such as G < 14 and RP < 14 with reliable radial-velocity measurements from GaiaDR3. Also, to have a colour consistent with a K or early M star (0.98 < BP-RP < 2.39) and M_G_ > 4. Then as detailed in section 2, with the help of 2MASS, AllWISE and PanSTARRS photometry of these stars we estimated accurate photometric metallicities of stars having {sigma}Plx/Plx <= 0.2 and RUWE < 1.4 to ensure well behaved astrometric solutions. More, we only kept stars that have required photometry from all surveys and stars with gPS1 > 13.5 to avoid PanSTARRS saturation issues. Before [M/H] estimations, all magnitudes are previously coorected from dust extinction. We then apply a calibrated photometric metallicity relationship and remove stars that appear overluminous and are likely to be unresolved pairs as fully explained in Medan et al (2021AJ....161..234M, Cat. J/AJ/161/234) and briefly discussed in our section 2. The resulting photometric metallicities do have the limitation of having larger uncertainties at lower metallicities ([M/H]<-1.5) and at the lower mass end of the calibration range, with the calibration valid only over the colour range 0.98 < BP-RP < 2.39. To account for this, we finally restrict the sample to stars with photometric metallicities that have an uncertainty <0.3 dex at the 95 per cent confidence level. This results in the final sample of 256381 stars. Next, we examined the kinematic groups present in our photometric metallicity sample, we transform Gaia 6D astrometric data into Galactic Cartesian coordinates: galactic radius R, galactic height z, velocity towards the galactic anticentre U, velocity in the direction of Galactic rotation V and velocity in the direction perpendicular to the Galactic plane W. Also, we provide a mixed coordinate x_mix_ to more clearly identify these clumps in orbital space. All these quantites are available for all our selected stars in table1.dat. Next, in section 3 and 4, with GALAH dr3 data we linked age distribution of a group of stars based on their distribution in W versus metallicity. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 97 256381 The K and early M dwarfs stars from Gaia DR3 stars with G < 14 and RP < 14 with reliable photometric metallicity estimates -------------------------------------------------------------------------------- See also: J/MNRAS/506/150 : The GALAH+ Survey DR3 (Buder+, 2021) J/MNRAS/478/3809 : TGAS distances (Schonrich+, 2018) J/MNRAS/473/2004 : TESS-HERMES Survey Data Release 1 catalog (Sharma+, 2018) J/MNRAS/440/3430 : SDSS-2MASS-WISE stellar colour locus (Davenport+, 2014) J/A+A/669/A104 : Stellar parameters from Gaia DR3 (Kordopatis+, 2023) J/A+A/619/A72 : Milky Way disk kinematic sub-structures (Ramos+, 2018) J/A+A/430/165 : Radial velocities for 6691 K and M giants (Famaey+, 2005) J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars (Pecaut+, 2013) J/AJ/161/234 : 1.7 million K and M dwarfs cross-matching (Medan+, 2021) J/AJ/133/694 : Abundances in the HR 1614 moving group (De Silva+, 2007) VII/233 : 2MASS All-Sky Extended Source Catalog (XSC) (IPAC-UMass, 2003-2006) V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020) V/117 : Geneva-Copenhagen Survey of Solar neighbourhood (Holmberg+, 2007) III/286 : APOGEE-2 DR17 final allStar catalog (Abdurro'uf+, 2022) III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020) II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+,2016) II/328 : AllWISE Data Release (Cutri+ 2013) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 19 I19 --- GaiaDR3 The GaiaDR3 source ID (source_id) 21- 35 F15.11 deg RAdeg Right ascension (ICRS) at Ep=2016.0 (ra) 37- 51 F15.11 deg DEdeg Declination (ICRS) at Ep=2016.0 (dec) 53- 57 F5.2 [Sun] [M/H] Photometric metallicity estimated with calibrated relationship from Medan et al. (2021AJ....161..234M, Cat. J/AJ/161/234) as described in sect. 2 ([M/H]) 59- 62 F4.2 [Sun] e_[M/H] Standard deviation on photometric metallicity ({sigma}[M/H]) 64- 71 F8.3 km/s U Galactic U velocity (U) 73- 80 F8.3 km/s V Galactic V velocity (V) 82- 89 F8.3 km/s W Galactic W velocity (W) 91- 97 F7.3 kpc xmix The xmix coordinate = R_G_*cos({phi}) as defined in eq. 2 of sect. 2.2 where {phi} is current azimuth of star and R_G_ is the guiding center defined in eq. 1 of sect. 2.2 (x_mix_) -------------------------------------------------------------------------------- History: From electronic version of the journal License: CC-BY-4.0 ================================================================================ (End) Luc Trabelsi [CDS] 19-May-2026