myung gyoon lee with hong soo park & in sung jang seoul national university, korea...
TRANSCRIPT
A Globular Cluster View of Massive Galaxy For-
mation
Myung Gyoon LeeWith Hong Soo Park & In Sung Jang
Seoul National University, Korea
Multiwavelength surveys: Formation and Evolution of Galaxies from the Early Universe to Today, May 11-16, 2014, Dubrovnik, Croatia
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Multi-wavelength surveys lead to remark-able advances in understanding of forma-tion and evolution of massive galaxies.
However, most methods are based on inte-grated stellar light! (Limits) 1) Observing only the inner regions of gal-axies, seeing only a tip of an iceberg!2) Difficult to distinguish multiple popula-tions!
Knowns for Massive Galaxies
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Stellar Halos! Not dark, but very faint!
1) Do massive galaxies have a single halo or multiple halos?2) What about their structure, metallicity, kinematics?3) How different are halos in E galaxies from bulges in disk galaxies?4) How did these halos form?
Unknowns for Massive Gal-axies
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Note that stellar halos occupy not only the outer region but also the inner region of a galaxy!
(Two powerful probes)1) Globular clusters (GCs), tracing halos.2) Resolved stars, showing directly stellar halos! Working better for early-type galaxies
(ETGs)
How to Study Stellar Halos?
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Color distribution of GCs is bimodal, showing that there are two types:
blue (metal-poor) GCs and red (metal-rich) GCs. Both may be older than 10 Gyr (corresponding to
z>2).
Globular Clusters in a Massive E Galaxy in Virgo
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Globular Clusters in M49 (Geisler, Lee, & Kim 1996, AJ, Lee et al 1998, AJ)
color
An example: M59 (E5)
(Shapes of the GC sys-tems) The red GC system is more elongated than the blue GC system.
Estimation of Ellipticity(e) of the GC systems in 23 bright E/S0 galaxies.
(Park & Lee 2013, ApJL, 773,27)
Maps of Blue GCs and Red GCs: M59
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Data: homogeneous set of gz photometry of GCs in 100 Virgo ETGs in HST/ACSVCS (Cote+2004, Jordan+2009) – gray map
The ellipticity of the red GC systems show a tight correlation with galaxy stellar light, while the blue GC systems do much less.
Ellipticity of GC systems and galaxy
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Ellip
ticit
y (
GC
syste
m)
Ellipticity (galaxy stel-lar light)
Red GC systems show a strong correlation with Mv: fainter galaxies have more elon-gated red GC systems.
Blue GC systems show little correlation with Mv.
Ellipticity (GC System) vs Mv(galaxy)
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Ellipticity of the red GC systems shows a strong correlation with rotation of their host galaxy: the faster galaxies rotate, the more elongated their red GCSs are.
In contrast, the blue GC systems do little.
Ellipticity (GC system) vs Rotation (galaxy)
9Rotational parameter (star)[AT-LAS 3D]
e(G
CS
-sta
r) e
llip
ticit
y
(GC
S)
Massive ETGs have dual halos!
A blue halo and a red halo. Yin & Yang model?
Structure of ETGs: a new view
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Old view
New view
Lee+ (2013)
The blue halo (metal-poor)◦Rounder, More extended◦Non-rotating?
The red halo (metal-rich)◦Main body of ETGs◦Strong correlation with
stars◦Elongated, Compacter◦Rotating?
Dual Halos in ETGs
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Globular Clusters in M49
(Lee, Kim & Geisler 1998 AJ)
Blue halo : Red halo
A large scale map of the GCs in Virgo
12Lee, Park & Hwang (2010, Science):
SDSS
Number density maps of GCs
Substructures around massive galaxies
Diffuse large scale structure-Intracluster GCs (wandering GCs) !!!
The blue halos are much larger than the red halos!
(radial density profiles are flatter). Intracluster GCs are mostly blue GCs! (old &
metal-poor)
Blue GCs and Red GCs in Virgo
13Lee, Park & Hwang (2010, Science): SDSS
Blue GCs : Red GCs
What about Stellar Halos?
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M105, a standard E1 galaxy, at 10 Mpc in Leo.
(Harris+ 2007, Lee & Jang 2014)
Resolved stars show two RGB pops: Blue (metal-poor) RGB and Red (metal-rich)
RGBs!
Resolved Stars in Es
15Lee & Jang (2014, in prep)
Stars in M105(E1) Blue: Red
RGB
Two components Inner region(3-7 Reff):
red RGB dominates
Outer region(10-13Reff): lue RGB gets stronger, while the peak metallicity of thbe red RGB re-mains constant.
Metallicity Distributions of Stars in M105
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Metallicity, [M/H]
Showing two stellar ha-los: blue and red.
Inner region
Outer re-gion
Blue: Red RGB
Lee & Jang (2014, in prep)
Formation of Massive ETGs
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Two mode formation!1) Red halo mode
◦ In situ formation via dissipative col-lapse/merger
◦Mostly metal-rich stars◦Starting from a or more massive
progenitors with rotation
2) Blue halo mode◦Dissipationless merger/accretion◦Mostly metal-poor stars ◦Mostly from dwarf galaxies
To be tested with simulations.
Summary
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Massive galaxies have dual ha-los!
We are seeing mostly the red halos embedded in much larger blue halos!
Massive galaxies formed in red and blue modes.
New view