DanceDance ofof thethe Stars:Stars:
AnAn AnalysisAnalysis ofof thethe SpatialSpatial EvolutionEvolution ofof TwoTwo ClustersClusters
Anne Buckner (University of Leeds) & the SFM Collaboration
Image Credit: Wikimedia Commons TalkTalk OutlineOutline
Stellar Association
INDICATE A B C Carina Nebula D
Upper Scorpius
StellarStellar AssociationAssociation
● Point processes – intensity – correlation – spatial distribution
StellarStellar AssociationAssociation
● Point processes – intensity – correlation – spatial distribution
Q. How “clustered” are stars?
WhyWhy isis studyingstudying stellarstellar associationassociation important?important?
WhyWhy isis studyingstudying stellarstellar associationassociation important?important?
● Define the distribution and clustering of stars
● Trace morphological features → variation in degree of clustering of stars in regions (as a function of e.g. age, mass, position)
● Discriminate between different modes of Massive SF
MeasuringMeasuring StellarStellar AssociationAssociation
MeasuringMeasuring StellarStellar AssociationAssociation
1. Global measures
MeasuringMeasuring StellarStellar AssociationAssociation
1. Global measures
– 2-point correlation function – Hopkins Statistic
== xx
MeasuringMeasuring StellarStellar AssociationAssociation
1. Global measures
– 2-point correlation function – Hopkins Statistic
2. Local measures
MeasuringMeasuring StellarStellar AssociationAssociation
1. Global measures X X 6 7 X – 2-point correlation function 8 – X X Hopkins Statistic X 5 9 X X 4 2 3 X X 10 11 X X X 18 12 1 X 19 X X 2. Local measures 17 X 13 X 14 16 X – INDICATE 15
INDICATE INdex to Define Inherent Clustering And TEndencies
INDICATE INdex to Define Inherent Clustering And TEndencies
● Local measure of degree of stellar association ● Any parameter space ● 2+D
INDICATE INdex to Define Inherent Clustering And TEndencies
● Local measure of degree of stellar association ● Any parameter space ● 2+D
● Assigns a clustering index to each star ● Comparison of number of nearest neighbours with an evenly spaced control field ● Meaningful index values → calibrated against random distributions
INDICATE INdex to Define Inherent Clustering And TEndencies
I = 20/5 = 4 I = 3/5 = 0.6
Carina Nebula
Typical A ~ 0.5-3 mag v (< 10 mag)
Age < 6 Myr
D ~ 2.3 kpc
M > 105 M .
130+ OB Stars
Image Credit: Wikipedia/ Harel Boren Carina Nebula Khun et al. (2014)
Buckner et al. 2018 (in review) Carina Nebula
Sig level: I > I random + 3σ 5 5
Buckner et al. 2018 (in review) OB Stars
Sig level: I > I random + 3σ 5 5
Buckner et al. 2018 (in review) OB Stars: self-clustering
Sig level: I > I random + 3σ 5 5
Buckner et al. 2018 (in review) OB Stars OB Stars
OB Stars
Buckner et al. 2018 (in review) Upper Scorpius
Age ~5-10 Myr
D ~ 145 pc
OB association
~1300 candidate members
Image Credit: WIkipedia Galli et al. 2018 5 I
Buckner et al. 2018 (in prep) Members clustered above random
90 80 70 60 Column B 50 40 30 20 % star's significantly star's % clustered 10 0 All G<12 mag G>12 mag
Index ranges
All
G<12 mag
G>12 mag
0 5 10 15 20 25 30 35 40 45 Buckner et al. 2018 (in prep) I 5 Self-clustering
90
80
70
60 Column B 50
40
30 % star's significantly star's % clustered
20
10
0 G<12 mag G>12 mag
Buckner et al. 2018 (in prep) Summary
INDICATE → powerful local measure of degree of “clustering” of stars
2+D, any parameter space
Trace morphological features in SF regions
Buckner et al. (2018, A&A, in review)
Image from Pixabay.com Summary
INDICATE → powerful local measure of degree of “clustering” of stars
2+D, any parameter space
Trace morphological features in SF regions
Buckner et al. (2018, A&A, in review)
Clustering tendencies in NW and SE regions of Carina different
More pronounced for OB stars
No mass segregation in SE region
Image from Pixabay.com Summary
INDICATE → powerful local measure of degree of “clustering” of stars
2+D, any parameter space
Trace morphological features in SF regions
Buckner et al. (2018, A&A, in review)
Clustering tendencies in NW and SE regions of Carina different
More pronounced for OB stars
No mass segregation in SE region
Upper Scorpius is centrally concentrated
Higher mass population more spatially dispersed than lower mass
Signature of SF history
Image from Pixabay.com