Rapid dynamical processes in the cores of young LMC star...
Transcript of Rapid dynamical processes in the cores of young LMC star...
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