Concentra)on of dusty starbursts and AGNs at a z=3.09 proto- cluster core

Transcription

1 September 9,2015 at Soverato, Italy Concentra)on of dusty starbursts and AGNs at a z=3.09 proto- cluster core Hideki Umehata (ESO, U. Tokyo) Kotaro Kohno, Yoichi Tamura (U. Tokyo), et al 1

2 Outlines Introduction - Our target: Submillimeter galaxies (SMGs) - SMGs and Environmental Dependence Previous studies in the SSA22 field - a protocluster at z= SMG surveys in SSA22 ALMA Deep Field in SSA22 - Discovery of SMG cluster at the center of the protocluster - High X-ray AGN fraction for these SMGs Summary 2

3 SMGs: Submillimeter Selected Galaxies What re SMGs? - First Discovery: < 20 years ago SCUBA 850 um (e.g., Smail+1997, Hughes+1998) - Properties: Luminous in rest-frame FIR bands ( Lsun) High SFR (a few Msun/yr) Large gas reservoir ( Msun) Large stellar mass ( Msun) AGN-host (a few x 10 %?) high-z population (<z> =2.5~3.0?) (For review; e.g., Casey+2014) Redshifts of SMGs 100 (Hughes+1998) Massive Dusty Starbursts in the early universe. (Simpson+2014) 3

4 The importance of dust- obscured star forma)on? SFRD (Madau ea 2014) Dust obscured star formation plays a main role in the early universe. We are still ignorant in the obscured part of star formation at z 3. 4

5 The Importance A Burst of SMGs: Phase 3. of A Burst Massive Phase Ellip)cals of Massive? Ellipticals? Are SMGs a most active starburst phase of the most massive galaxies (e.g., Eales+1999; Lilly+1999;? Toft +2014)? Stellar archaeology suggests that massive ellipticals must have short formation timescales (<1 Gyr e.g., Thomas et al. 2005). (Madau ea 2014) Obscured Star Formation History What s the contribution of SMGs to SFRD? (~20% at z=2.5? (Swinbank ea 2014) z~2 z 3 We are still ignorant in the obscured part of star formation at z>3. z~0 NASA, ESA, S. Toft, A. Feild 5

6 SMGs and Environment Previous studies (except for SSA22) SMGs are in biased field AzTEC3 field (z~5.3 galaxies) - COSMOS-AzTEC3 (z=5.3)(e.g., Capak ea 2011) - HDF850.1 (z=5.2) (e.g., Walter ea 2012) - GN20 (z=4.05) (e.g., Daddi ea 2009) SMGs are in less overdense fields - GOODS-N (z=1.99) (Chapman ea 2009) - Cl (z=1.62) (Smail ea 2014) A great many of SMGs have no information about environment. (Capak ea 2011) => The situation is still unclear. - Where are SMGs formed in each era? - Which kind of environmental dependence? (or no dependence?) 6

7 The Unique Laboratory: SSA22 Proto- cluster at z=3.09 (Yamada+2012) (Matsuda+2005) Large-scale Structure traced by LAEs (~1deg) 8-10sigma overdensity for central 100 Mpc 2 (comoving) Enhancement of LBGs, LABs, DRGs, X-ray sources, K-selected galaxies, etc are found around the density peak. 7

8 SSA22 AzTEC SMG Survey ASTE 10m + AzTEC 8 (Umehata ea 2014)

9 Correla)on between bright SMGs and LAEs Using two-point angular cross-correlation function, Tamura et al. (2009) found that bright SMGs are likely to be correlated with LAEs. - But there were no redshift information. 9

10 ALMA Surveys in SSA Dec (J2000) ADF NLAE (arcmin 2 ) Background: LAE Density Blue circles: AzTEC SMGs Mpc 10 Mpc Red circles ALMA Targets s 18 m s s s RA (J2000) 22 h 17 m s Our ALMA Survey - 1. ALMA imaging of 45 AzTEC sources - 2. ALMA Deep Field (<- Today s Talk) 10

11 ALMA Deep Field in SSA Dec (J2000) ADF NLAE (arcmin 2 ) Mpc s 18 m s s s RA (J2000) 22 h 17 m s What is ALMA Deep Field in SSA22? - A 2 x 3 region has been observed contiguously. - One of the largest deep and wide images taken by ALMA. Why such deep field needed? - Deeper, more precise submm/mm observation. - Due to source confusion, some fraction of SMGs might be missed. 11

12 ALMA Observations Observa)ons Dates Cycle 2 high priority project Date: June 6 10, 2014 (April, 2015) Conditions Number of antennas: Baseline length: m (C34-4) Configuration... 2 years and 3 months. Precipitable water vapers: mm Observing time: 6 hours (temporary) 12

13 ALMA 1.1mm Image Number of pointing: 80 Resolution: 0.53 x 0 50 Wavelength: 1.1mm Noise level: ujy (1σ) (We had additional observations this April.) 2 arcmin 13

14 AzTEC/ASTE ALMA 14

15 Resolu)on: 30 => 0.5 Sensi)vity : 0.7 mjy => 0.06 mjy AzTEC/ASTE ALMA 15

16 ALMA 1.1mm Image Number of pointing: 80 Resolution: 0.53 x 0 50 Wavelength: 1.1mm Noise level: ujy (1σ) (-> SFR_IR~60 Msun/yr) Detected ALMA sources >5σ 12 sources 4-5σ 34 sources (Some of 4-5σ sources are likely to be fake ones.) 2 arcmin 16

17 ALMA 1.1mm Image Number of pointing: 80 Resolution: 0.53 x 0 50 Wavelength: 1.1mm Noise level: ujy (1σ) (-> SFR_IR~60 Msun/yr) (photo- z) Detected ALMA sources >5σ 12 sources 4-5σ 34 sources (Some of 4-5σ sources are likely to be fake ones.) 8 SMGs w/ spec-z= (L_IR = 10^ Lsun) a few more z=3.09 candidates arcmin 17

18 SMGs and SMGs Large and Scale Large Structure scale structure at z=3.09 Circles: LAEs Crosses: SMGs 18

19 SMGs and SMGs Large and Scale Large Structure scale structure at z=3.09 Circles: LAEs Crosses: SMGs - > SMGs are likely to be at the node - > ~x30 overdense - > We might be seeing the burst phase of massive ellip)cals. 19

20 Global SF- Density Rela)on SFR-Environmental density Relation (Scoville+2013) Less Dense Dense z=2-3 z= They didn t consider dusty starbursts such as SMGs at z>2. 20

21 Global SF- Density Rela)on Less Dense Dense z~3.1 This work (Smail ea 2014) At a z=1.6 Cluster, SMGs are NOT located at the core. 21

22 Global SF- Density Rela)on : SMGs / ULIRGs : QGs / Ellipticals z~3.1 z~1.6 We suggest The site of the most active starbursts would move from center to outer parts as decreasing redshift. 22

23 SMGs as a growth phase of SMBHs X- ray Sog B: Blue Hard B: Red (Lehmer+2009) ALMA 23

24 AGN SMGs as a growth phase of SMBHs z=3.09 X- ray AGN w/o ALMA detec)on 3.086, 3.086(tenta)ve) AGN AGN (photo- z) AGN AGN AGN X- ray Sog B: Blue Hard B: Red (Lehmer+2009) ALMA 24

25 SMGs as a growth phase of SMBHs Results of ADF22 4 out of 8 SMGs at z=3.09 SMGs host X-ray luminous AGNs (there are two X-ray luminous SMGs at z~3.09, additionally). Lx ~ 10^44 erg/s (Lehmer et al. 2009) Results of general fields (ECDF-S) X-ray AGN fraction is about 17 % as a whole. (there field is deeper than ours.) There is only 1 X-ray SMGs at z>3 in ECDF-S. => AGN fraction of SMGs is high at the node. => The growth of SMBH is also promoted. 25

26 Summary Environmental Dependence on SMG formation has been controversial. We observed the SSA22 protocluster at z=3.09 by ALMA. We found a rich cluster of SMGs at the node of the largescale structure traced by LAEs. The vigorous star-formation activity as well as the growth of super massive black holes (SMBHs) simultaneously occurred at the density peak at z=3. 26

27 Summary Environmental Dependence on SMG formation has been controversial. We observed the SSA22 protocluster at z=3.09 by ALMA. We found a rich cluster of SMGs at the node of the largescale structure traced by LAEs. The vigorous star-formation activity as well as the growth of super massive black holes (SMBHs) simultaneously occurred at the density peak at z=3. 27

28 SMGs as a growth phase of SMBHs Results of ADF22 x30 overdense compared to general fields (cf: Swinbank+14) >x2-3 high X-ray AGN fraction of SMGs (cf: Wang+2013) Averaged growth ratio => Rela)vely High Growth ra)o Absorp)on- corrected X- ray Luminosity SSA22 Protocluster ECDF- S (General Field) 28