1. Mass- and Environmental- dependence of Star-formation Properties of High-redshift Galaxies Seong-Kook Lee (CEOU/SNU) With Prof. Myungshin Im and Dr. Jaewoo Kim

2.  What stops (or lowers) SF activity in galaxies? 2015-02-11KASI

3.  What stops (or lowers) SF activity in galaxies?  How the environment affects the evolution of galaxies? 2015-02-11KASI

4.  galaxy clusters in Λ CDM? 2015-02-11KASI Galaxy Clusters as Dense Environment - Largest gravitationally bound structure - residing at the peak of DM density fluctuation ⇒ tracers of the most massive structure & densest environment Cluster specific physical processes affecting galaxy properties : ram pressure stripping, strangulation, galaxy harassment Study of galaxy clusters and properties of galaxies within it ⇒ insight about the structure formation and galaxy evolution (esp. environmental effects on it)

5.  At local, various galaxy properties strongly depend on environment 2015-02-11KASI Galaxy Properties in Clusters Dressler 80 density fraction early late lenticular Morphology – density relation - in dense environment, majority is early-type & lenticulars, while late-type galaxies dominate the low-density region

6.  At local, various galaxy properties strongly depend on environment 2015-02-11KASI Galaxy Properties in Clusters Gomez+03, SDSS SFR – density relation - SFRs are, on average, lower in higher density region, and star-forming galaxies prefer the low-density environment 75% 25% median SFR cumulative fraction Cluster (core) field SFR Balogh+97

7.  At local, various galaxy properties (morphology, optical color, SFR) strongly depend on their environment how or why ? what makes this environmental dependence ? when ? epoch/timescale for the emergence of the environmental effect? 2015-02-11KASI Galaxy Properties in Clusters Need to study high-redshift (z ~1 or higher) galaxy clusters and cluster galaxies : becomes available thanks to the powerful facilities, including CHFT, Subaru, UKIRT…

8.  At high-z (z~1), 2015-02-11KASI Galaxy Properties in Clusters Cooper+08 Elbaz+07 density SFR z~0 z~1 density SFR field Reversal of SFR-density relation ?

9.  At high-z (z~1), 2015-02-11KASI Galaxy Properties in Clusters van der Wel+07 No Reversal : morphology Early-type fraction decreases with redshift, but still high in clusters than field at z~1

10.  At high-z (z~1), 2015-02-11KASI Galaxy Properties in Clusters No Reversal : color Both of color & red galaxy fraction increase at high-density environment up to z < 1 Grutzbauch+11

11.  At high-z (z~1), 2015-02-11KASI Galaxy Properties in Clusters Muzzin+12 No Reversal : (S)SFR SF fraction/SFR/SSFR lower in cluster core than field even at z~1 Mass-bin

12.  At high-z (z~1), 2015-02-11KASI Galaxy Properties in Clusters - Difference between cluster & field reduced in terms of galaxy color/SFR/morphology - But, controversy remains yet : reversal or not or disappearing ? - also, we want to see the relative importance of environment and mass on galaxy (SF) properties We want to study galaxy properties in galaxy clusters 1. at z~1 and beyond 2. down to low stellar mass limit 3. not biased against clusters with active SF members ⇒ need deep multi-band (esp. NIR) data

13.  Cluster Finding 2015-02-11KASI Methods 1. Divide galaxy samples in redshift bin (bin size : Δ z = 0.02) and RA/Dec bin (grid size: Δθ = 12”) 2. At each grid point, count galaxies within radius ≤ 500/h kpc 3. Find grid points with count, N (galaxy) ≥ 4 σ (count) 4. Identify over-dense regions (= clusters) with conditions (1) ≥ 10 connected grid points with ≥ 4 σ, and (2) detected in ≥ 3 successive redshift bins ⇒ (proto-)cluster candidates 5. Find member galaxies belonging to these candidates within r ≤ 1 Mpc, Δ z/(1+z) ≤ 0.032

14.  UKIDSS (UKIRT Infrared Deep Sky Survey) 2015-02-11KASI Galaxy Clusters in UDS SurveyAreaDepth (5 σ ) Large Area Survey (LAS)4000 sq. degsK=18.4 Galactic Plane Survey (GPS)1800 sq. degsK=19.0 Galactic Clusters Survey (GCS)1400 sq. degsK=18.7 Deep Extragalactic Survey (DXS) 35 sq. degsK=21.0 Ultra Deep Survey (UDS) 0.77 sq. degsK=23.0 DATA Optical : Subaru B (28.4), V (27.8), R (27.7), i (27.7), z (26.7) NIR : UKIRT J (24.9), H (24.2), K (24.6) MIR : Spitzer/IRAC ch1-ch4 (~24)

15.  (proto-)cluster candidates at 0.5 < z < 2 2015-02-11KASI Results 4 Mpc 3 Mpc 5.5 Mpc 3.5 Mpc 46 cluster candidates within 0.5<z<2 Subaru images of z~1 clusters

16.  Colour of cluster- and field-galaxies 2015-02-11KASI Results clusters field -At the highest z-bin (z~1.8), optical colour distribution similar in clusters and field -Difference between clusters and field shows up from z~1.3 and below At z~1, colour distribution different (more red dominated) in clusters compared to field (no reversal!!) (u-g) rest

17.  Colour evolution of blue galaxies 2015-02-11KASI Results Reddening (with decreasing redshift) of the blue galaxy population well explained by the aging of stellar population SFR peaks at z~1.7 Hopkins+06

18.  Colour vs. SF property 2015-02-11KASI Results Distributions of optical colour and of sSFR (SFR/M*) show slight difference : sSFR evolution somewhat slower & non-negligible fraction of red SF galaxies Q: what are these red SF galaxies ? - (merger-driven) starburst? - or galaxies in transition phase (i.e., fading)

19.  Properties of Red SF galaxies 2015-02-11KASI Results late-type early-type merger G : a statistic measuring how uniform the distribution of light within a galaxy is G=0 if uniform; G=1 if all light in one pixel (early-type > late-type; mergers have large value) M20 : ≈ inverse of concentration (<<0 if highly concentrated) Q: what are these red SF galaxies ? - (merger-driven) starburst? - or galaxies in transion phase (i.e., fading)

20.  optical colour distribution shows no (previously reported) reversal of environmental dependent trend at z~1  At the highest z-bin (z~1.8), the colour distributions in clusters and field similar (no environmental trend, yet)  Optical colour and sSFR behaves not exactly same : There are non-negligible fraction of SF galaxies among red population ⇒ will get different results whether we see colour or sSFR to investigate the environmental effects  morphological & SF properties suggest that majority of the red SF galaxies are in transition phase from blue SF to red passive galaxies (rather than dust starbursts) 2015-02-11KASI Conclusion I

21.  sSFR of cluster- and field-galaxies 2015-02-11KASI Results clusters field At z~1, no reversal of environmental dependence - Disappearance of environmental trends at z~1.8 (similar with colour-distribution) - Difference between clusters and field is milder than colour distribution (i.e. shows up later)

22.  Evolution of quiescent galaxy fraction 2015-02-11KASI Results quiescent galaxy fraction - Rapid increase of quiescent fraction - No significant difference between clusters and field - Clear difference between clusters and field - Increase of quiescent fraction slowed down (esp. in field) 1. Well consistent with previous results (open symbols) 2. Evolution of quiescent fraction seems to be divided into different epochs at z~1.4

23.  Evolution of quiescent galaxy fraction 2015-02-11KASI Results quiescent galaxy fraction 1. Well consistent with previous results (open symbols) 2. Evolution of quiescent fraction seems to be divided into different epochs at z~1.4 Δt ≈ 1 Gyr Typical timescale for environmental quenching? (e.g. strangulation vs. ram pressure stripping?)

24.  z~1.3-1.4 defines transition phase in terms of environmental quenching? 2015-02-11KASI Comparison with other work Alberts+13 (S)SFR ( ← Herschel/SPIRE 250um) Average SFRAverage SSFR

25.  Evolution of quiescent galaxy fraction 2015-02-11KASI Results quiescent galaxy fraction 1. Well consistent with previous results (open symbols) 2. Evolution of quiescent fraction seems to be divided into different epochs at z~1.4 3. Dependence on the mass-cut more significant than on the environment

26.  Evolution of quiescent fraction (mass bin) 2015-02-11KASI Results (quiescent fraction in clusters) (quiescent fraction in field) SDSS - quiescent fraction shows clear difference at different mass-bin (> env. difference) - massive : z~0.5 ≈ z~0 (earlier/faster growth) low-mass : z~0.5 << z~0 Environmental dependence more significant for low-mass galaxies at lower redshift

27.  Evolution of quiescent fraction (mass bin) 2015-02-11KASI Results (quiescent fraction in clusters) (quiescent fraction in field) SDSS - quiescent fraction shows clear difference at different mass-bin (> env. difference) - massive : z~0.5 ≈ z~0 (earlier/faster growth) low-mass : z~0.5 << z~0 Environmental dependence more significant for low-mass galaxies at lower redshift (Quadri+12)

28.  Environ. Quenching efficiency 2015-02-11KASI Results no clear stellar-mass dependence Then, why quiescent galaxy fraction shows clearer excess for low mass galaxies? excess of quiescent galaxy fraction in cluster over field compared to SF galaxy fraction in field ⇒ the fraction of SF galaxies in field that would become quiescent if they were in cluster (e.g. Quadri+12) high-mass : mass-quenching + environmental quenching low-mass : environmental quenching only (Peng+10, z~0.3-0.6)

29.  Possible origin(s) - Halo quenching due to virial shock heating (Birnboim & Dekel03; Dekel & Birnboim06) - AGN Feedback (Hopkins+05; Di Matteo+08; Cattaneo+09) - Morphological quenching (Martig+09) - Earlier/faster gas consumption? 2015-02-11KASI Mass Quenching? (Peng+10, z~0.3-0.6) No environmental dependence

30.  sSFR distribution also shows no reversal of environmental trend at z~1 & while the trend weakened/disappear at the highest z-bin  Stellar mass plays more significant role than the environment in determining the SF status of galaxies  at z~1.4, the SF properties of galaxies show a transition in terms of quiescent fraction increase as well as environmental dependence  Low-mass galaxies show more clear difference in quiescent fraction between clusters and field, esp. at z<1.4  Environmental quenching efficiency shows no clear mass- dependence, but the effect more significant for low-mass galaxies which are not affected by mass quenching 2015-02-11KASI Conclusion II

31.  What stops (or lowers) the SF activity in galaxies?  How the environment affects the evolution of galaxies? 2015-02-11KASI Can we answer these questions now?

32.  What stops (or lowers) the SF activity in galaxies?  How the environment affects the evolution of galaxies?  We have shown that both mass & environment affect SF activity, while mass plays more significant role  Environmental effects appears to be significant at lower redshift (z < 1.4)  But, physical process(es) for mass- or environmental-quenching still should be investigated 2015-02-11KASI Can we answer these questions now?

33.  More high-z clusters 1. in SA22 field (UKIDSS/DXS + IMS: 8+12 deg 2 ) (lead by Dr. Jaewoo Kim) 2015-02-11KASI On-going (team) work Infrared Medium-deep Survey (IMS) - ~150 deg 2 extragalactic fields (7 separate fields) - to 23 AB mag (5- σ ) - J-band imaging from UKIRT WFCAM (9-years) - Y-band imaging from Maidanak, McDonald and other facilities

34.  More high-z clusters 2. in ELAIS-N1,N2 field (IMS) (lead by Minhee Hyun) 2015-02-11KASI On-going (team) work

35.  Spectroscopic follow-up - with Magellan/IMACS (Inamori Magellan Areal Camera and Spectrograph) - during October 2014, January 2015 and more - FoV : d=27.4 arcmin (~ 13 Mpc at z~1) - can observe ≥ 10 galaxy clusters as well as field galaxies at the same redshift range - provides halo mass & accurate SFR/age measure 2015-02-11KASI On-going (team) work

36.  Medium/broad-band follow-up - with SQUEAN at McDonald - new filter sets (including medium bands) are being installed - can provide… - better SED resolution => improved photo-z & SFR through SED-fitting - [OII]-emission or 4000 break for spectroscopically confirmed galaxies - additional broad-band data for wider SED coverage (esp. for Elais fields) 2015-02-11KASI On-going (team) work

37.  Hunting for proto-clusters at very high-z : searching for the LSS with LBG population at z ≥ 3 - motivation: 1. we have detected galaxy cluster up to z~2 2. we expect SF galaxies dominate the galaxy clusters at z ≥ 3 ⇒ looking for where SF galaxies are concentrated (sharp contrast in strategy compared to lower-z cluster search) ⇒ LBGs are good candidates for this search, because LBGs are more common than other extreme objects (SMGs or quasars) 2015-02-11KASI On-going (team) work

38.  Spectroscopic Follow-up with GMT (Giant Magellan Telescope)/GMACS - can reach down to R~25.5 (SNR~10) with moderate exposure time of ~4 hours - with current best facility (e.g., VLT FORS2), only can reach ~24 (SNR~5) with similar exposure time - therefore, we can observe lower mass galaxies, thus can confirm the stellar-mass dependent environmental effects in galaxy clusters - with optional IR-arm, we can reach higher redshift (z≤2) 2015-02-11KASI long-term future

39.  More high-z clusters - with LSST & JWST deep (& very wide) multi-color imaging data ⇒ identify cluster candidates ⇒ follow-up with GMT 2015-02-11KASI long-term future

40.  We have found 46 galaxy clusters at 0.5 < z < 2 using multi- wavelength data (Subaru + UKIRT + Spitzer) in the UDS field  We confirm no reversal of environmental dependence in colour and in sSFR at z~1  At the highest z-bin (z~1.8), environmental dependence weakens or disappears  Stellar mass plays more significant role in determining SF status of galaxies than environment, especially at z≥1.4  z~1.4 defines a transition epoch in build-up of quiescent galaxies : z > 1.4 : rapid build-up, little environment-dep. z < 1.4 : slowed down, environment-quenching  Environmental quenching becomes more significant for low-mass galaxies at low-z with timescale ~ 1 Gyr  Environmental quenching efficiency shows no mass dependence  Further search of high-z galaxy clusters as well as spectroscopic and photometric follow-up is going on 2015-02-11KASI Summary