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

 What stops (or lowers) SF activity in galaxies? KASI

 What stops (or lowers) SF activity in galaxies?  How the environment affects the evolution of galaxies? KASI

 galaxy clusters in Λ CDM? KASI 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)

 At local, various galaxy properties strongly depend on environment KASI 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

 At local, various galaxy properties strongly depend on environment KASI 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

 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? KASI 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…

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

 At high-z (z~1), KASI 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

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

 At high-z (z~1), KASI 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

 At high-z (z~1), KASI 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

 Cluster Finding KASI 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

 UKIDSS (UKIRT Infrared Deep Sky Survey) KASI 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)

 (proto-)cluster candidates at 0.5 < z < KASI 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

 Colour of cluster- and field-galaxies KASI 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

 Colour evolution of blue galaxies KASI 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

 Colour vs. SF property KASI 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)

 Properties of Red SF galaxies KASI 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)

 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) KASI Conclusion I

 sSFR of cluster- and field-galaxies KASI 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)

 Evolution of quiescent galaxy fraction KASI 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

 Evolution of quiescent galaxy fraction KASI 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?)

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

 Evolution of quiescent galaxy fraction KASI 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~ Dependence on the mass-cut more significant than on the environment

 Evolution of quiescent fraction (mass bin) KASI 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

 Evolution of quiescent fraction (mass bin) KASI 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)

 Environ. Quenching efficiency KASI 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~ )

 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? KASI Mass Quenching? (Peng+10, z~ ) No environmental dependence

 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 KASI Conclusion II

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

 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 KASI Can we answer these questions now?

 More high-z clusters 1. in SA22 field (UKIDSS/DXS + IMS: 8+12 deg 2 ) (lead by Dr. Jaewoo Kim) KASI 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

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

 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 KASI On-going (team) work

 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) KASI On-going (team) work

 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) KASI On-going (team) work

 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) KASI long-term future

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

 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 KASI Summary