The Dynamical Structure and Ini3al Mass Func3on of the Arches - PowerPoint PPT Presentation

The Dynamical Structure and Ini3al Mass Func3on of the Arches Cluster Jessica Lu (UH/IfA), Jay Anderson (StSci), Ma;hew Hosek Jr. Andrea Ghez (UCLA), Mark Morris (UCLA), Will Clarkson (UMichigan-Dearborn), Tuan Do Graduate Student, UH/IfA (UCLA)

The Arches Cluster: A Young Massive Cluster Near the GalacKc Center Arches Cluster ~26 pc GC Stolte et al. (2008)

The Arches Cluster: A Young Massive Cluster Near the GalacKc Center • What impact does the GC Arches environment have on the Cluster dynamical structure of massive star clusters? ~26 pc GC Stolte et al. (2008)

The Arches Cluster: A Young Massive Cluster Near the GalacKc Center • What impact does the GC Arches environment have on the Cluster dynamical structure of massive star clusters? ~26 pc GC • How does the Ini3al Mass Func3on behave in extreme star- forma3on environments? Stolte et al. (2008)

The Arches Cluster: A Young Massive Cluster Near the GalacKc Center • What impact does the GC Arches environment have on the Cluster dynamical structure of massive star clusters? ~26 pc GC • How does the Ini3al Mass Func3on behave in extreme star- forma3on environments? Stolte et al. (2008)

Hosek et al. (2015): Measure the Radial Profile to Large Radii • Unknown Kdal radius, profile only measured to R = 0.4 pc (Espinoza+09) – Extra-Kdal stars? r t ? 1 pc HST WFC3IR image of the Arches Cluster

Hosek et al. (2015): Measure the Radial Profile to Large Radii High reddening • Unknown Kdal radius, profile only measured to R = 0.4 pc (Espinoza+09) – Extra-Kdal stars? • Challenge: Significant differenKal reddening – ΔA V ~ 10-15 mag (Habibi+13) – Cluster membership tricky! 1 pc HST WFC3IR image of the Low reddening Arches Cluster

SoluKon: HST Astrometry • HST WFC3IR: 3 epochs / 2 years in F153M, 1 epoch in F127M Advantages: (1) Proper moKons for improved cluster membership (2) Wide field of view: 120x120’’ (4.8 pc x 4.8 pc) (3) Deep: ~2.5 M � hgp://www.spacetelescope.org/

High-Precision Proper MoKons 0.65 mas/yr 24.7 km/s ~2.5 M � Hosek+15

High-Precision Proper MoKons 0.65 mas/yr 24.7 km/s Stars passing error cut: 6023 ~2.5 M � Hosek+15

Modeling Cluster and Field KinemaKcs: Gaussian Mixture Model Vector Point Diagram Cluster Hosek+15

Modeling Cluster and Field KinemaKcs: Gaussian Mixture Model Observed CMD Vector Point Diagram Probable Cluster Members (P > 0.7) Cluster Hosek+15

Modeling Cluster and Field KinemaKcs: Gaussian Mixture Model Diff. De-reddened CMD Vector Point Diagram Probable Cluster 2.5 Myr Members (P > 0.7) isochrone Cluster Hosek+15

The Extended Radial Profile of the Arches Cluster Model: Background Power-Law + Constant subtracted profile: 0.25 pc ≤ R ≤ 3 pc Best-Fit Params: Γ = 2.06 ± 0.17 b = 2.52 ± 1.32 stars/pc 2 A 0 = 23.09 ± 3.5 stars Field ContaminaKon: 2.52 stars/pc 2 Hosek+15

The Extended Radial Profile of the Arches Cluster Model: Background Background Power-Law + Constant subtracted profile: subtracted profile: Espinoza+09: 0.25 pc ≤ R ≤ 3 pc 0.25 pc ≤ R ≤ 3 pc R ≤ 0.4 pc Best-Fit Params: Γ = 2.06 ± 0.17 b = 2.52 ± 1.32 stars/pc 2 A 0 = 23.09 ± 3.5 stars Field ContaminaKon: 2.52 stars/pc 2 Hosek+15

The Extended Radial Profile of the Arches Cluster Model: Background Background Background Power-Law + Constant subtracted profile: subtracted profile: subtracted profile: Espinoza+09: Espinoza+09: 0.25 pc ≤ R ≤ 3 pc 0.25 pc ≤ R ≤ 3 pc 0.25 pc ≤ R ≤ 3 pc R ≤ 0.4 pc R ≤ 0.4 pc Best-Fit Params: Γ = 2.06 ± 0.17 b = 2.52 ± 1.32 stars/pc 2 A 0 = 23.09 ± 3.5 stars Field ContaminaKon: 2.52 stars/pc 2 Predicted Tidal Radius: 2.5 pc 3σ lower limit on 3dal radius: 2.8 pc Hosek+15

Mass SegregaKon Throughout Cluster 17 < F153M < 20 Γ = 1.75 Γ = 2.70 F153M < 17 Hosek+15 • KS test: not drawn from same parent populaKon – Stolte+05, Espinoza+09, Habibi+13

No Evidence of Tidal Tails Γ = 1.86 Γ = 2.32 Parallel to Orbit Perpendicular to Orbit Hosek+15 • KS test: cannot discount same parent populaKon

Unbroken Profile: ImplicaKons for Orbital History? Peñarrubia+09, Lokas+13: SimulaKons of dwarf galaxies on ellipKcal orbits show break in profile aser pericenter PosiKon of break related • to Kme since pericenter passage Fig. 2 of Peñarrubia+09

If Applicable to Arches… No pericenter passage between ~0.2 – 1 Myr ago • Possible Arches Orbits Black: Prograde Red: Retrograde (Stolte+08) Data courtesy of Andrea Stolte

If Applicable to Arches… No pericenter passage between ~0.2 – 1 Myr ago • Possible Arches Orbits Prograde Retrograde Black: Prograde Red: Retrograde (Stolte+08) Retrograde orbits • excluded Arches located in front • of GC sky plane NOT ALLOWED Data courtesy of Andrea Stolte

Next Step: Combine HST with AO Data HST/WFC3IR F153M

Next Step: Combine HST with AO Data HST/WFC3IR Keck/NIRC2 AO F153M K’-band Start of Keck/NIRC2 JHK’ observing campaign: 2006

Conclusions • HST WFC3IR study of Arches cluster – Proper moKons to idenKfy cluster members – Large FOV to measure radial profile to 3 pc – Depth: 2.5 M �� • Unbroken power-law profile – 3σ limit on King-like Kdal radius: 2.8 pc – Constrains orbit to prograde soluKons? • No evidence for Kdal tails • Next step: Combine HST with AO imaging of cluster core