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

1

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

2

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?

4

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