1. Seong-Kook Lee
Center for the Exploration of the Origin of the Universe (CEOU),
Seoul National University (SNU)
(Myungshin Im, Jae-Woo Kim, Minhee Hyun, Bomi Park, Jennifer Lotz, Conor McPartland, Michael Peth, Anton Koekemoer)
Star-formation properties and large scale structures of high-redshift galaxies

2. Q : How and when did galaxies become quiescent?

3. Quenching of SF in galaxies
What makes galaxies stop forming stars?
1. Mass quenching : virial shocks slowing down the cooling rate (Birnboim+07)
2. Feedbacks : AGN/stellar (Croton+06; Somerville+08; Hopkins+14)
3. Morphological quenching : (Gavazzi+15; Zolotov+15; Tacchella+16)

4. Quenching of SF in galaxies
4. Environmental quenching : (Peng+10; Woo+13)
Strangulation (Larson+80; Balogh+00, Peng+15)
Ram pressure stripping (Gunn&Gott 72; Abadi+99)
Credit: Peng+15
Galaxy harassment (Moore+96,98)
Credit: Univ. of Zurich
Credit: A.Chung

5. Effects of Environment
Clear environment-dependent bi-modality in galaxy properties at local (Lewis et al. 2002; Kauffmann et al. 2004; Blanton et al. 2005)
In clusters,
galaxies are …
red color , early-type morphology, old stellar
population, no
star-formation
(quiescent)
In field,
galaxies are …
blue color , late-type morphology, young stellar population,
star-forming

6. Effects of Environment
Clear environment-dependent bi-modality in galaxy properties at local (Lewis et al. 2002; Kauffmann et al. 2004; Blanton et al. 2005)
This environmental dependence weakens with increasing redshift

7. Effects of Environment
Clear environment-dependent bi-modality in galaxy properties at local (Lewis et al. 2002; Kauffmann et al. 2004; Blanton et al. 2005)
This environmental dependence weakens with increasing redshift
Still, its detailed evolution is not conclusive :

8. Effects of Environment
z~1
Clear environment-dependent bi-modality in galaxy properties at local (Lewis et al. 2002; Kauffmann et al. 2004; Blanton et al. 2005)
This environmental dependence weakens with increasing redshift
Still, its detailed evolution is not conclusive : e.g. SF-density relation: reversal (Elbaz+07, Cooper+08) or not (Patel+09, Muzzin+12, Quadri+12) at z~1 ?
field

9. Effects of Environment
Clear environment-dependent bi-modality in galaxy properties at local (Lewis et al. 2002; Kauffmann et al. 2004; Blanton et al. 2005)
This environmental dependence weakens with increasing redshift
Still, its detailed evolution is not conclusive : e.g. SF-density relation: reversal (Elbaz+07, Cooper+08) or not (Patel+09, Muzzin+12, Quadri+12) at z~1 ?
investigation at higher redshift
well beyond z~1 needed
(⇒ need deep (NIR) data)

10. Effects of Environment
Clear environment-dependent bi-modality in galaxy properties at local (Lewis et al. 2002; Kauffmann et al. 2004; Blanton et al. 2005)
This environmental dependence weakens with increasing redshift
Still, its detailed evolution is not conclusive : e.g. SF-density relation: reversal (Elbaz+07, Cooper+08) or not (Patel+09, Muzzin+12, Quadri+12) at z~1 ?
investigation at higher redshift
well beyond z~1 needed
(⇒ need deep (NIR) data)
UKIDSS/UDS : ~0.8 sq. deg.
Subaru B,V,R,i,z (optical), UKIRT J,H,Ks (NIR), Spitzer/IRAC channel 1,2,3,4 (MIR)

11. Method: cluster finding
z-range : ±0.028(1+z)
step size : ∆z = 0.02

12. Method: cluster finding
Redshift range : 0.5 – 2.0
z-range : ±0.028(1+z)
step size : ∆z = 0.02 4σ
Figures from Kang & Im 15

13. Quiescent galaxy fraction
Q.G.F. = Nquiescent / Ntotal
◆ : cluster
◆ : field
1. Q.G.F depends more strongly on stellar mass than environment
Lee,S.-K., Im, M. et al.
2015, ApJ, 810,90

14. Quiescent galaxy fraction
Q.G.F. = Nquiescent / Ntotal
◆ : cluster
◆ : field
1. Q.G.F depends more strongly on stellar mass than environment
2. Environmental dependence becomes significant at z < (for low-mass galaxies)

15. Quiescent galaxy fraction
Variation among clusters at similar epoch

16. Quiescent galaxy fraction
Variation among clusters at similar epoch
cluster 3
cluster 2
cluster 1

17. Summary
Quiescent galaxy fraction (Q.G.F) shows stong stellar-mass dependence within the redshift range (0.5 < z < 2.0)
Environmental dependence of Q.G.F. becomes significant at z < 1.3 & for low-mass galaxies
There exists large variation among individual clusters (at similar epoch) in their Q.G.F.
The Q.G.F. seems to be related with the LSS to which the galaxy clusters belong