Present-Day Formation of Globular Clusters from Cooled Intracluster Gas

主讲人 (Speaker): 
Jeremy Lim
主讲人单位 (Speaker's Institute): 
香港大学
邀请人 (Invited by): 
张泳
时间 (Time): 
星期一, 2018/10/08 - 10:00 to 11:00
地点 (Location): 
珠海校区海滨红楼18栋217 (Rm 217, Red House 18)
摘要 (Abstract): 

Globular clusters (GCs) — compact and massive star clusters found ubiquitously around galaxies — are believed to be ancient relics (ages >∼10 Gyr) from the early formative phase of galaxies, although their physical origin remains a mystery. GCs are especially numerous in massive elliptical galaxies usually found at the centres of galaxy clusters, where they exhibit a broad and continuous range of colours – attributed to a broad and continuous range of metallicities. Here, I describe our discovery that many thousands of compact and massive star clusters have formed at an approximately steady rate over, at least, the past ∼1Gyr around the nearby giant elliptical galaxy, NGC1275, at the centre of the Perseus cluster. The number distribution of these young star clusters exhibits a similar dependence in luminosity and mass as the even more numerous but older GCs around NGC 1275. In just a few Gyr, these young star clusters will evolve to become indistinguishable in broadband optical colours from the older GCs, and their spread in age add to the dispersion in colour of these GCs. The spatial distribution of the young star clusters resembles the filamentary network of multiphase gas in the cluster core, implying that they formed from molecular gas amassed from cooling of the hot intracluster gas. The sustained formation of compact and massive star clusters from cooled intracluster gas constitutes a previously unrecognised but prodigious source of GCs over cosmic timescales, and contributes to both their enormous numbers and broad colour dispersion in massive elliptical galaxies. I close by discussing the curious fact that star clusters produced by ordinary galaxies, starbursts and mergers, cooled intracluster gas in massive elliptical galaxies, as well as GCs, all share the same initial mass functions despite the different environments under which they form.

主讲人简介 (Speaker's CV): 
AssociateProfessor–UniversityofHongKong,HongKong(2009-present) AdjunctResearch Fellow –Institute of Astronomy & Astrophysics (ASIAA),Taipei,Taiwan (2009– present) AssociateResearchFellow –ASIAA,Taipei,Taiwan(2000) AcademiaSinicaDistinguished PostdoctoralFellow – ASIAA,Taipei,Taiwan(1995) PostdoctoralFellow – ASIAA,Taipei,Taiwan(1994)