Myung Gyoon Lee Seoul National University, Korea 2014.11.6 The 6 th KIAS Workshop on Cosmology and...
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Transcript of Myung Gyoon Lee Seoul National University, Korea 2014.11.6 The 6 th KIAS Workshop on Cosmology and...
Formation of Mas-sive Early-type Gal-
axies
Myung Gyoon Lee Seoul National University, Korea
2014.11.6
The 6th KIAS Workshop on Cosmology and Structure Formation, Nov 4-7, 2014 , KIAS , Seoul
1
Massive ETGs are rare in the field.
2
Massive ETGs are abundant in massvie clusters!
3
Superclusters are an ideal lab for seeing galaxy evolution!
SDSS DR7 + WISE study of ETGs (red) and LTGs (blue) in A2199 (GH Lee, HS Hwang, MG Lee et al. 2014, ApJ, submitted , Poster)
three clus-ters + four groups +
something else
Morphology from KIAS VAGC
Galaxy evolution in the MIR C-L diagram
Late-type MIR SF sequence galaxies
Late-type MIR green valley galaxies
Early-type MIR green valley galaxies
Early-type MIR blue cloud galaxies
Star formation quenching
Morphology transformation
several Gyr
Opt GV
Various surveys & simulations lead to re-markable advances in understanding of formation and evolution of massive galax-ies.
Formation of Massive ETGs in 2014
6 However,
(NASA/STScI)
However, most methods are based on inte-grated stellar light! (Limits) 1) Observing mostly only the inner regions of galaxies, seeing only a tip of an iceberg!2) Difficult to distinguish multiple popula-tions!
Current limits for Massive ETG stud-ies
7
8
(1) Ghost light in galaxy clus-ters?
Intracluster light is also abundant in clus-ter!
It is bluer than massive galaxies! (Montes+2014: A2744)
Its origin? Heavy or light galaxies?
Stellar Halos! Not dark, but very faint!
1) Do massive ETGs have a single halo (spheroid) or multiple halos?2) How different are halos in E galaxies from bulges in disk galaxies?3) How did these halos form?
(2) Unknowns for Massive ETGs
9
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!
How to Study Stellar Halos?
10
Color distributions of GCs are bimodal, showing blue (metal-poor) GCs and red (metal-rich) GCs. Both may be older than 10 Gyr (corresponding to
z>2).
Globular Clusters in Massive ETGs in Virgo
11
Globular Clusters in M49 (Geisler, Lee, & Kim 1996, AJ, Lee et al
1998, AJ)
color
The blue GC system looks circular, while the red GC system is more elongated.
-Why both systems in a galaxy show difference?
-Is M49 special? -Is this common among
massive ETGs? -What does it tell about
galaxy formation?
An Old Mystery on GCs in M49
12
Globular Clusters in M49
(Lee, Kim & Geisler 1998 AJ)
Blue GC : Red GC
To answer these questions, we need
A systematic study for a large sample of ETGs! (Park & Lee 2013, ApJL, 773, L27)
13
An example: M59 (E5) Gray: GCs in 100 galax-
ies Color: M59
(Shapes of the GC sys-tems) The red GC system is more elongated than the blue GC system.
Gems in HST/ ACSVCS!
14
Data: homogeneous set of gz photometry of GCs in 100 Virgo ETGs (Cote+2004, Peng+2006, 2008, Jordan+2009) – gray map
Small field of view, but excellent quality!
Ellipticity of the red GC systems shows a tight 1:1 correlation with galaxy stellar light,
while the blue GC systems do much less.
Ellipticity of GC systems vs galaxy
15
Ellip
ticit
y (
GC
syste
m)
Ellipticity (galaxy stel-lar light)
Red GC systems show a strong correlation with Mv (galaxy): fainter galaxies have more elongated red GC systems.
Blue GC systems show little correlation with Mv.
Ellipticity (GC System) vs Mv(galaxy)
16
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)
17Rotational parameter (star)[AT-LAS 3D]
e(G
CS
-sta
r) e
llip
ticit
y
(GC
S)
18
What can we make it out of it?
Massive ETGs have dual halos!
A blue halo and a red halo. Yin & Yang model?
A new view for ETG structures!
19
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
20
Globular Clusters in M49
(Lee, Kim & Geisler 1998 AJ)
Blue halo : Red halo
A large scale map of the GCs in Virgo
21Lee, 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
22Lee, Park & Hwang (2010, Science): SDSS
Blue GCs : Red GCs
What about Stellar Halos?
23
Standard E galaxy at 10 Mpc.
M105, E1 in Leo Group
24
M105-W
M105-SE Reff = 0’.93
Reff = 0’.55
14.9 kpc5’
+
+
12 Reff
Michel-Dansac+2010,CFHT/Megacam
M105 (Harris+ 2007 (SE field), Lee & Jang 2014)
Resolved stars show two RGB pops: Blue (metal-poor) RGB and Red (metal-rich)
RGBs!
Resolved Stars in Es
25Lee & Jang (2014, in prep)Blue: Red
RGB
Two components Metal-rich stars dom-
inate in the inner re-gion.
Metal-poor stars get significant in the outer region.
Radial Density Profiles of Stars in M105
26Lee & Jang (2014, in prep)
Two components Inner region(3-7 Reff): the red RGB domi-nates
Outer region(10-13Reff): the blue RGB gets stronger, while the peak metallicity of the red RGB remains con-stant.
Metallicity Distributions of Stars in M105
27
Metallicity, [M/H]
Showing two stellar ha-los: blue and red.
Consistent with GC ha-los!
Inner re-gion
Outer re-gion
Blue: Red RGB
Lee & Jang (2014, in prep)
Discovery of an ultra-faint dwarf galaxy (UFD) in the Virgo: a fossil of the first galaxies?
(Jang & Lee 2014 Nov 1, ApJL, 795, L6)
+
Virgo cluster
Mihos+2005
+
Virgo cluster
Mihos+2005
+
Virgo cluster
Mihos+2005
HST field (Williams+07)
F606W ~ 63000sF814W ~ 27000s
dSph-D07(Durrell+07)
+
Virgo cluster
Mihos+2005
HST field (Williams+07)
F606W ~ 63000sF814W ~ 27000s
dSph-D07(Durrell+07)
+
Virgo cluster
Mihos+2005
HST field (Williams+07)
F606W ~ 63000sF814W ~ 27000s
dSph-D07(Durrell+07)
New galaxy
8" × 8"
Color magnitude diagrams
20” x 20”
dSph-D07 (m-M)0 = 31.19± 0.05
(d = 17.3 ± 0.4 Mpc)
[Fe/H] = -2.4± 0.4
Existence of AGB
Color magnitude diagrams
20” x 20”
dSph-D07
10” x 10”
New galaxy
(m-M)0 = 31.19± 0.05
(d = 17.3 ± 0.4 Mpc)
[Fe/H] = -2.4± 0.4
Existence of AGB
(m-M)0 = 31.08± 0.05
(d = 16.4 ± 0.4 Mpc)
[Fe/H] = -2.4± 0.4
No AGB stars
Color magnitude diagrams
20” x 20”
dSph-D07
10” x 10”
Virgo-UFD1
(m-M)0 = 31.19± 0.05(d = 17.3 ± 0.4 Mpc)[Fe/H] = -2.4± 0.4Existence of AGB stars (m-M)0 = 31.08± 0.05(d = 16.4 ± 0.4 Mpc)[Fe/H] = -2.4± 0.4No AGB stars
A new galaxy is
a genuine member of Virgo cluster. very metal poor ([Fe/H] ~ -2.4). very old (age > 10 Gyr). ultra-faint (Mv= -6.5) dwarf small (R(eff) = 81 pc). UFDs (as well as dSphs) may be the origin of
the blue halos and ICL?
Formation of Massive ETGs
37
Two mode forma-tion!
1) Red halo mode◦ In situ formation via dissipative
collapse/merger ◦Mostly metal-rich stars◦Starting from a or more massive
progenitors with rotation
2) Blue halo mode◦Dissipationless merger/accre-
tion◦Mostly metal-poor stars ◦Mostly from dwarf galaxies
To be tested with simula-tions.
Implication for Size Evolution
38
Current idea to explain size evolution of ETGs: progenitors of massive ETGs formed at z>3 and grew via minor merger at z<2.
However, measured Reffs are based on metal-rich stars, i.e., the red halo! They do not recognize the existence of the blue halo.
Implication for Size Evolution
39
Current idea to explain size evolution of ETGs: progenitors of massive ETGs formed at z>3 and grew via minor merger at z<2.
However, measured Reffs are based on metal-rich stars, i.e., the red halo! They do not recognize the existence of the blue halo.
Possibilities: 1) dry merging of intermediate mass galaxies,
not of dwarf galaxies. 2) wet merging of gaseous galaxies 3) Two phase formation scenarios should be
three: two for red halos and one for blue halos.
Summary
40
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