J/MNRAS/489/3625 Applying Chronostar to β Pictoris group (Crundall+, 2019)
Chronostar: a novel Bayesian method for kinematic age determination.
I. Derivation and application to the β Pictoris moving group.
Crundall T.D., Ireland M.J., Krumholz M.R., Federrath C., Zerjal M.,
Hansen J.T.
<Mon. Not. R. Astron. Soc., 489, 3625-3642 (2019)>
=2019MNRAS.489.3625C 2019MNRAS.489.3625C (SIMBAD/NED BibCode)
ADC_Keywords: Positional data ; Proper motions ; Spectral types ;
Radial velocities ; Associations, stellar ; Optical ; Models
Keywords: methods: statistical - stars: kinematics and dynamics -
stars: statistics - galaxy: kinematics and dynamics -
open clusters and associations: general
Abstract:
Gaia DR2 provides an unprecedented sample of stars with full 6D
phase-space measurements, creating the need for a self-consistent
means of discovering and characterizing the phase-space overdensities
known as moving groups or associations. Here we present Chronostar, a
new Bayesian analysis tool that meets this need. Chronostar uses the
Expectation-Maximization algorithm to remove the circular dependency
between association membership lists and fits to their phase-space
distributions, making it possible to discover unknown associations
within a kinematic data set. It uses forward-modelling of orbits
through the Galactic potential to overcome the problem of tracing
backward stars whose kinematics have significant observational errors,
thereby providing reliable ages. In tests using synthetic data sets
with realistic measurement errors and complex initial distributions,
Chronostar successfully recovers membership assignments and kinematic
ages up to ∼100Myr. In tests on real stellar kinematic data in the
phase-space vicinity of the β Pictoris Moving Group, Chronostar
successfully rediscovers the association without any human
intervention, identifies 10 new likely members, corroborates 48
candidate members, and returns a kinematic age of 17.8±1.2Myr. In
the process we also rediscover the Tucana-Horologium Moving Group, for
which we obtain a kinematic age of 36.3+1.3-1.4Myr.
Description:
In this paper we present the methodology for Chronostar, a new
kinematic analysis tool to identify and age unbound stars that share a
common origin. The tool requires no manual calibration or
pre-selection, and simultaneously and self-consistently solves the
problems of assigning stars to associations and determining the
properties of those associations. We test Chronostar extensively on
synthetic data sets, including ones containing multiple, overlapping
components and ones where the initial positions and velocities are
stars are drawn directly from a hydrodynamic simulation of star
formation, and show that it returns very accurate membership
assignments and kinematic ages. In tests on real data, we show that
Chronostar is capable of blindly recovering the β Pictoris and
Tucana-Horologium moving groups, with the kinematic data used to find
the latter originating solely from Gaia DR2 (Gaia Collaboration, 2018,
Cat. I/345).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table7.dat 1351 867 Astrometry and memberships to βPMG (Comp A)
as well as reference to previous work listing
star as member of βPMG
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJ/860/43 : BANYAN. XII. New members from Gaia-Tycho data (Gagne+, 2018)
Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Name Star name
25- 41 A17 --- 2MASS 2MASS identifier (JHHMMSSss+DDMMSSs)
43- 61 I19 --- GaiaDR2 ? Gaia DR2 identifier
63- 81 A19 --- AllWISE AllWISE identifier (JHHMMSS.ss+DDMMSS.s)
83- 108 A26 --- OName Other name
110- 114 A5 --- comp [True/False/ ] Companion flag
116- 134 F19.15 deg RAdeg Right ascension (J2000)
136- 152 F17.15 mas e_RAdeg ? Error on RAdeg
154- 172 F19.15 deg DEdeg Declination (J2000)
174- 190 F17.15 mas e_DEdeg ? Error on DEdeg
192- 210 F19.15 mas plx ? Parallax
212- 228 F17.15 mas e_plx ? Error on plx
230- 249 F20.15 mas/yr pmRA ? Proper motion in right ascension
251- 267 F17.15 mas/yr e_pmRA ? Error on pmRA
269- 288 F20.15 mas/yr pmDE ? Proper motion in declination
290- 306 F17.15 mas/yr e_pmDE ? Error on pmDE
308- 325 F18.15 --- RADEcor ? Correlation between right ascension
and declination
327- 344 F18.15 --- RAPlxcor ? Correlation between right ascension
and parallax
346- 363 F18.15 --- RApmRAcor ? Correlation between right ascension
and proper motion in right ascension
365- 382 F18.15 --- RApmDEcor ? Correlation between right ascension
and proper motion in right declination
384- 401 F18.15 --- DEPlxcor ? Correlation between declination and
parallax
403- 420 F18.15 --- DEpmRAcor ? Correlation between declination and
proper motion in right ascension
422- 439 F18.15 --- DEpmDEcor ? Correlation between declination and
proper motion in declination
441- 458 F18.15 --- PlxpmRAcor ? Correlation between parallax and
proper motion in right ascension
460- 477 F18.15 --- PlxpmDEcor ? Correlation between parallax and
proper motion in declination
479- 496 F18.15 --- pmRApmDEcor ? Correlation between proper motion in
right ascension and proper motion in
declination
498- 517 F20.15 --- Rplx ? Ratio between parallax and its error
519- 524 F6.1 yr Epoch ? Epoch of observations
526- 544 F19.15 deg GLON ? Galactic longitude (l)
546- 564 F19.15 deg GLAT ? Galactic longitude (b)
566- 584 F19.15 deg ELON ? Ecliptic longitude
586- 604 F19.15 deg ELAT ? Ecliptic latitude
606- 624 F19.15 pc X ? X position in Galactic cartesian
coordinates
626- 644 F19.15 pc Y ? Y position in Galactic cartesian
coordinates
646- 664 F19.15 pc Z ? Z position in Galactic cartesian
coordinates
666- 683 F18.15 km/s U ? U component of space velocity
685- 702 F18.15 km/s V ? V component of space velocity
704- 721 F18.15 km/s W ? W component of space velocity
723- 730 A8 --- SpType Spectral type
732- 736 F5.3 Msun Mass ? Approximate mass
738 I1 --- APF [0/1] Primary or secondary (1)
740- 750 F11.6 K Teff ? Effective temperature
752- 759 F8.5 mag BPmag ? Gaia DR2 BP magnitude
761- 780 E20.18 e-/s FBP ? Gaia DR2 BP band flux
782- 789 F8.5 mag RPmag ? Gaia DR2 RP magnitude
791- 798 F8.5 mag Gmag ? Gaia DR2 G magnitude
800- 817 F18.15 mag GMAG ? Absolute G magnitude
819- 826 F8.6 mag BP-RP ? Gaia DR2 BP-RP colour
828 A1 --- phcons [YN ] Photometric consistency
830- 831 I2 --- r_RV Reference for radial velocity (2)
833- 836 A4 --- refmb Reference for membership (3)
838- 854 F17.15 pc e_X ? Error on X
856- 872 F17.15 pc e_Y ? Error on Y
874- 890 F17.15 pc e_Z ? Error on Z
892- 909 F18.15 km/s e_U ? Error on U
911- 928 F18.15 km/s e_V ? Error on V
930- 946 F17.15 km/s e_W ? Error on W
948- 965 F18.15 --- XYcor ? Correlation between X and Y
967- 984 F18.15 --- XZcor ? Correlation between X and Z
986-1006 E21.18 --- XUcor ? Correlation between X and U
1008-1025 F18.15 --- XVcor ? Correlation between X and V
1027-1044 F18.15 --- XWcor ? Correlation between X and W
1046-1063 F18.15 --- YZcor ? Correlation between Y and Z
1065-1082 F18.15 --- YUcor ? Correlation between Y and U
1084-1101 F18.15 --- YVcor ? Correlation between Y and V
1103-1120 F18.15 --- YWcor ? Correlation between Y and W
1122-1139 F18.15 --- ZUcor ? Correlation between Z and U
1141-1158 F18.15 --- ZVcor ? Correlation between Z and V
1160-1177 F18.15 --- ZWcor ? Correlation between Z and W
1179-1196 F18.15 --- UVcor ? Correlation between U and V
1198-1215 F18.15 --- UWcor ? Correlation between U and W
1217-1234 F18.15 --- VWcor ? Correlation between V and W
1236-1254 F19.15 km/s RV ? Radial velocity
1256-1273 F18.15 km/s e_RV ? Error on RV
1275-1281 F7.5 --- compA ? Membership probability of the star to
component A (4)
1283-1289 F7.5 --- compB ? Membership probability of the star to
component B (4)
1291-1297 F7.5 --- compC ? Membership probability of the star to
component C (4)
1299-1305 F7.5 --- compD ? Membership probability of the star to
component D (4)
1307-1313 F7.5 --- compE ? Membership probability of the star to
component E (4)
1315-1321 F7.5 --- compF ? Membership probability of the star to
component F (4)
1323-1329 F7.5 --- compbkg ? Membership probability to the
background field distribution
1331-1351 A21 --- bayanass Assignment of star to groups and
associations in the banyan catalogue (5)
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Note (1): Flag indicating if this source was used as a primary source (1) or
secondary source (0). Only primary sources contribute to the
estimation of attitude, calibration, and global parameters. The
estimation of source parameters is otherwise done in exactly the same
way for primary and secondary sources.
Note (2): Radial velocity references as follows:
1 = Gagne et al. (2018ApJ...856...23G 2018ApJ...856...23G, Cat. J/ApJ/856/23)
2 = Schlieder, Lepine & Simon (2010AJ....140..119S 2010AJ....140..119S, Cat. J/AJ/140/119)
3 = Alonso-Floriano et al. (2015A&A...583A..85A 2015A&A...583A..85A, Cat. J/A+A/583/A85)
4 = Moor et al. (2006ApJ...644..525M 2006ApJ...644..525M)
5 = Elliott et al. (2014A&A...568A..26E 2014A&A...568A..26E, Cat. J/A+A/568/A26)
6 = Moor et al. (2013MNRAS.435.1376M 2013MNRAS.435.1376M)
7 = Torres et al. (2008hsf2.book..757T 2008hsf2.book..757T)
8 = Gagne et al. (2018ApJ...860...43G 2018ApJ...860...43G, Cat. J/ApJ/860/43)
9 = Zuckerman et al. (2001ApJ...562L..87Z 2001ApJ...562L..87Z)
10 = Malo et al. (2013ApJ...762...88M 2013ApJ...762...88M, Cat. J/ApJ/762/88)
11 = Malo et al. (2014ApJ...788...81M 2014ApJ...788...81M, Cat. J/ApJ/788/81)
12 = Kiss et al. (2011MNRAS.411..117K 2011MNRAS.411..117K)
13 = Elliott et al. (2016A&A...590A..13E 2016A&A...590A..13E, Cat. J/A+A/590/A13)
29 = Gagne & Faherty (2018ApJ...862..138G 2018ApJ...862..138G, Cat. J/ApJ/862/138)
30 = Gagne, Faherty & Fontaine (2018RNAAS...2....9G 2018RNAAS...2....9G)
31 = Neuhauser & Forbrich (2008hsf2.book..735N 2008hsf2.book..735N)
Note (3): Membership references as follows:
14 = Torres et al. (2006A&A...460..695T 2006A&A...460..695T, Cat. J/A+A/460/695)
15 = Gaia Collaboration et al. (2018A&A...616A..11G 2018A&A...616A..11G, Cat. I/345)
16 = Kiss et al. (2011MNRAS.411..117K 2011MNRAS.411..117K)
17 = Allers et al. (2016ApJ...819..133A 2016ApJ...819..133A)
18 = Shkolnik et al. (2017AJ....154...69S 2017AJ....154...69S, Cat. J/AJ/154/69)
19 = Torres et al. (2009ApJ...698..242T 2009ApJ...698..242T)
20 = Gontcharov (2006AstL...32..759G 2006AstL...32..759G, Cat. III/252)
21 = Malo et al. (2014ApJ...788...81M 2014ApJ...788...81M, J/ApJ/788/81)
22 = Valenti & Fischer (2005ApJS..159..141V 2005ApJS..159..141V, J/ApJS/159/141)
23 = Anderson & Francis (2012AstL...38..331A 2012AstL...38..331A, Cat. V/137)
24 = Song et al. (2003ApJ...599..342S 2003ApJ...599..342S)
25 = Montes et al. (2001MNRAS.328...45M 2001MNRAS.328...45M, Cat. J/MNRAS/328/45)
27 = Shkolnik et al. (2012ApJ...758...56S 2012ApJ...758...56S, J/ApJ/758/56)
28 = Faherty et al. (2016ApJS..225...10F 2016ApJS..225...10F, Cat. J/ApJS/225/10)
Note (4): A component is a collection of stars with similar 6D phase-space
properties and similar age. A simple association may only require a
single component, whereas an association with complex substructure
like the Scorpius-Centaurus OB Association might be better described
with multiple components.
The Chronostar fit applied to our sample identifies six components,
which we denote A through F.
Note (5): Groups identified in the Banyan catalogue (Gagne et al.
2018ApJ...860...43G 2018ApJ...860...43G, Cat. J/ApJ/860/43): Carina (3 stars), Columba
(4 stars), TW Hya (1 star), Tucana-Horologium (20 stars), Upper
Centaurus Lupus (2 stars) and beta Pictoris (60 stars). The rest (777
stars) are not assigned to any group or association in the banyan
catalogue.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 13-Jan-2023