rapid dynamical processes in the cores of young lmc star...
TRANSCRIPT
Rapid dynamical processes in the cores of young LMC star clusters
Main collaborators: Chengyuan Li (KIAA, PKU; China), Yi Hu, Licai Deng
(NAOC, China), Aaron Geller (Northwestern Univ., USA)
Richard de Grijs | 何锐思 �Kavli Institute for Astronomy and Astrophysics
Peking University, China
(Chengyuan will soon apply for postdoc posi6ons…)
NGC 1818
log (t/yr) 7.25–7.65 [Fe/H] –0.4 dex Rcore 2.1 ± 0.4 pc Rhl 2.6 pc Mcl 2.8 x 104 M¤
NGC 1805 Our young LMC clusters
Single-star main sequence
Binary sequence
U–V
V
Primordial binaries?
(Elson et al. 1998, MNRAS, 300, 857)
Ble
nd
ing
fra
cti
on
(de Grijs et al. 2013a, ApJ, 765, 4; Li, de Grijs, & Deng 2013, MNRAS, 436, 1497)
NGC 1805
NGC 1818
Correcting for blends …
blending
2 pixel resoluMon = 0.05 pc SeparaMons < 10,000 AU
… and incompleteness (de Grijs et al. 2013a, ApJ, 765, 4;
Li, de Grijs, & Deng 2013, MNRAS, 436, 1497)
NGC 1805
NGC 1818
0.96
0.97
0.98
t = 0
0.75
0.76
0.77
0.78
0.79
f bin (
<=
R)
t = 30 Myr
0 5 10 15 20R (pc)
0.68
0.70
0.72
0.74 t = 2.2 Gyr
0 5 10 15 20R (pc)
0.24
0.26
0.28
0.30
0.32
f bin (
<=
R)
3D
2D projecMons
(Geller, de Grijs, Li & Hurley, 2013, ApJ, 779, 30)
• We have shown that the compact, 15–30 Myr-‐old Large Magellanic Cloud cluster NGC 1818 exhibits an increasing frac6on of F-‐star binary systems with increasing radius
• This offers support of the theoreMcally predicted but thus far unobserved dynamical disrup6on processes of the significant populaMon of ‘soC’ binary systems in star clusters; “normal” dynamical evoluMon occurs on longer Mme-‐scales
• The (approximately) equally old LMC cluster NGC 1805 exhibits the opposite behaviour
• This likely implies a significant difference in dynamical age (rather than chronological age)
Pre-‐announcement: IAU Symposium on the “Forma;on, evolu;on, and survival of massive star clusters”
SOC: Corinne Charbonnel (co-‐chair), Antonella Nota (co-‐chair),
Holger Baumgardt, Peter Coirell, Richard de Grijs, Bruce Elmegreen, Yasuo Fukui, Patrick Hennebelle, Eva Noyola, Jan Palous,
Margarita Sharina, Nicole St Louis, Elena Terlevich