Formation of intergroup and intragroup objects
Kenji Bekki (UNSW)
Origin of isolated massive clouds, intergalactic HII regions, intragroup GCs
etc….
Today’s topic
• Formation of intragroup HI gas, rings, and HII regions (Bekki, Koribalski, Kilborn, Ryan-Weber, Ryder, Couch, etc…).
• Evolution of compact group of galaxies (my old studies).
• Formation of intergroup and intragroup GCs (with Yahagi).
Formation of intracluster/intercluster (group) GCs. (Yahagi & Bekki 2005)
The large-scale structure of MPCs(MPC=Metal-poor globular cluster)
Evolution of extended gas disks in high M/L galaxies.
NGC 2915 (Meurer et al. 1996)
gasstars
RHI/ROPT~ 2.0
gas
Three roles of galaxy interaction and galaxy-
group interaction
• Morphological transformation (e.g., SpSB)• Triggering starbursts and AGNs (+ GC
formation).• Formation of intragroup stellar and gaseous
(e.g., isolated HI gas, drifting GCs).
Origin of intragroup HI (e.g., recent HIPASS results)
(1) Intergalactic rings. (2)IntragroupHI (NGC 2442)
Ryan-Weber et al. (2002) Ryder et al. (2002)
Dynamical fate of stripped gas in groups
• Formation of isolated HI gas around NGC 2442 (Bekki, Koribalski, Ryder, & Couch 2005)
• ``Dark galaxy formation’’ (Bekki, Kilborn, & Koribalski 2005).
• Intragroup HII regions from tidal compression of HI clouds (Bekki & Ryan-Weber 2005).
Formation of intragroup HI rings (Bekki et al. 2004)
Gas Stars
HI ring formation from a LSB
(A) Simulation. (B) Observation
Dependence of HI morphology on detection limit
1017 cm-2 4*1018 cm-2 2*1019 cm-2 N(HI)thres =
``Dark HI galaxy’’ in the Virgo cluster (Minchin et al. 2005)
``Dark HI galaxy’’ as tidal derbis (Bekki et al. 2005)
2D velocity fields of simulated ``dark HIclouds’’.
Isolated disk
Intragroup HII regions around NGC 1533 in the Dorado group (Ryan-
Weber et al. 2004)
NGC 1533 center
HI disk
Formation of intragroup HII region from tidal compression.
thres = 3 Msolar/pc2
Gas
New stars Formation ofStars withinStripped HI(Bekki et al. 2005)
Other objects: NGC 1490(Oosterloo et al. 2004)
Gemini GMOS observations by de Oliveira et al. (2004)
Evolution of compact groups into field Es (Barnes 1989)
MRC (Meta-rich GC)
MPC(Metal-poor GC)
How can we prove figure rotation of Es from GC kinematics ?
Multiple starbursts in multiple mergers (Bekki 2001)
Formation of starburst/AGN in collapasing CGs ?
HST morphologies of ULIRGs.
Tidal stripping and common (metal-poor) gaseous halos
Outer disk
Inner disk
Transformation from spiral-rich groups with no intragroup gas into E-dominated ones with intragroup HI (also with spiral companion).
Possible candidate of HI ?
``Selective stripping’’ of outer parts of galaxies in CGs.
• Formation of common HI envelopes in CGs ?• Formation of metal-poor stellar halos (or hot
metal-poor X-ray gas) after E formation ?• A new clue of ``E+A’’s environments (2dF,
6dF, SDSS etc….e.g., the origin of E+As with companion galaxies)
Formation of intergroup GCs. (Yahagi & Bekki 2005)
The large-scale structure of MPCs(MPC=Metal-poor globular cluster)
(Yahagi & Bekki 2005:Bekki & Yahagi 2005)
INGC: Intergroup (intercluster, intergalaxy) GCs that are not within any virialized halos.
INGC
HGC HGC: GCs that are within virialized halos.
Distance (mass) of the closest neighbor halos.
Rnei Mnei
Predictions of INGC properties.
(1) ~ 100 INGCs / Mpc3.(2) More metal-poor, slightly younger than
those HGC (i.e.., GCs within halos).(3) Immune from GC destruction by
galaxy-scale tidal fields: Do they retain fossil information on initial cluster MF ?
Conclusions.
(1) Stripped HI as intragroup HI objects (e.g. isolated clouds, rings, ``dark galaxy’’ etc).
(2) Metal-poor stellar/gaseous halo formation after transformation from CGs to Es.
(3) Formation of intergroup/intercluster GCs in the hierarchical clustering scenario.
Formation of young star clusters (super star
clusters) in interaction/merging
galaxies.
(SSC: Mv<-10, size <15pc)
Basic components of a galaxy
Globular clusters (GC) Dark matter halo
Bulge
Disk (thin + thick)
Stellar halo
108 1012
109
1011
109
Conclusions.
(1) Stripped HI as intragroup HI objects (e.g. isolated clouds, rings, ``dark galaxy’’ etc).
(2) Metal-poor stellar/gaseous halo formation after transformation from CGs to Es.
(3) Formation of intergroup/intercluster GCs in the hierarchical clustering scenario.
