Myung Gyoon Lee Seoul National University, Korea The 6 th 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 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 clusters + 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 remarkable advances in understanding of formation and evolution of massive galaxies. 6  However, (NASA/STScI)

However, most methods are based on integrated stellar light! (Limits) 1) Observing mostly only the inner regions of galaxies, seeing only a tip of an iceberg! 2) Difficult to distinguish multiple populations! 7

8  Intracluster light is also abundant in cluster!  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? 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! 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). 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? 12 Globular Clusters in M49 (Lee, Kim & Geisler 1998 AJ) Blue GC : Red GC

 To answer these questions, we need 13

 An example: M59 (E5)  Gray: GCs in 100 galaxies  Color: M59 (Shapes of the GC systems) The red GC system is more elongated than the blue GC system. 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.  15 Ellipticity (GC system) Ellipticity (galaxy stellar light)

 Red GC systems show a strong correlation with M v (galaxy): fainter galaxies have more elongated red GC systems.  Blue GC systems show little correlation with M v. 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. 17 Rotational parameter (star)[ATLAS 3D]  e(GCS-star) ellipticity (GCS)

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 Massive ETGs have dual halos!  A blue halo and a red halo.  Yin & Yang model? 19 Old viewNew 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? 20 Globular Clusters in M49 (Lee, Kim & Geisler 1998 AJ) Blue halo : Red halo

21 Lee, 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) 22 Lee, Park & Hwang (2010, Science): SDSS Blue GCs : Red GCs

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 Standard E galaxy at 10 Mpc. 24 M105-W M105-SE R eff = 0’.93 R eff = 0’ kpc 5’ R eff Michel-Dansac+2010,CFHT/Megacam

 M105 (Harris (SE field), Lee & Jang 2014)  Resolved stars show two RGB pops:  Blue (metal-poor) RGB and Red (metal-rich) RGBs! 25 Lee & Jang (2014, in prep) Blue: Red RGB

 Two components  Metal-rich stars dominate in the inner region.  Metal-poor stars get significant in the outer region. 26 Lee & Jang (2014, in prep)

 Two components  Inner region(3-7 R eff ): the red RGB dominates  Outer region(10-13R eff ): the blue RGB gets stronger, while the peak metallicity of the red RGB remains constant. 27 Metallicity, [M/H]  Showing two stellar halos: blue and red.  Consistent with GC halos! Inner region Outer region Blue: Red RGB Lee & Jang (2014, in prep)

+ Mihos+2005

+

+ HST field (Williams+07) F606W ~ 63000s F814W ~ 27000s dSph-D07 (Durrell+07)

+ Mihos+2005 HST field (Williams+07) F606W ~ 63000s F814W ~ 27000s dSph-D07 (Durrell+07)

+ Mihos+2005 HST field (Williams+07) F606W ~ 63000s F814W ~ 27000s dSph-D07 (Durrell+07) New galaxy 8" × 8"

20” x 20” dSph-D07 (m-M) 0 = ± 0.05 (d = 17.3 ± 0.4 Mpc) [Fe/H] = -2.4 ± 0.4 Existence of AGB

20” x 20” dSph-D07 10” x 10” New galaxy (m-M) 0 = ± 0.05 (d = 17.3 ± 0.4 Mpc) [Fe/H] = -2.4 ± 0.4 Existence of AGB (m-M) 0 = ± 0.05 (d = 16.4 ± 0.4 Mpc) [Fe/H] = -2.4 ± 0.4 No AGB stars

20” x 20” dSph-D07 10” x 10” Virgo-UFD1 (m-M) 0 = ± 0.05 (d = 17.3 ± 0.4 Mpc) [Fe/H] = -2.4 ± 0.4 Existence of AGB stars (m-M) 0 = ± 0.05 (d = 16.4 ± 0.4 Mpc) [Fe/H] = -2.4 ± 0.4 No 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?

37  Two mode formation! 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/accretion ◦ Mostly metal-poor stars ◦ Mostly from dwarf galaxies  To be tested with simulations.

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 R eff s are based on metal-rich stars, i.e., the red halo! They do not recognize the existence of the blue halo.

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 R eff s 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.

40  Massive galaxies have dual halos!  We are seeing mostly the red halos embedded in much larger blue halos!  Massive galaxies formed in red and blue modes. New view