第4回 銀河進化研究会＠大阪大学 2017.06.07-09

Evolutionary phases of gas-rich galaxies
in a galaxy cluster at z=1.46
赤方偏移1.46の銀河団におけるガスリッチ銀河の進化段階
Hayashi et al., 2017, ApJL, 841, L21

Masao Hayashi (NAOJ)
林 将央 (国立天文台)
児玉忠恭(東北大), 河野孝太郎, 山口裕貴(東京大),但木謙一(国立天文台), 廿日出文洋(東京大),小山佑世(国立天文台), 嶋川里澄(Lick Observatory),
田村陽一(名古屋大), 鈴木智子(国立天文台)

Higher density

Quenching of star formationin galaxies
High density regions such as galaxy clusters
must play a vital role in quenching the starformation activity.

Possible mechanisms••••Major or minor mergers
Ram-pressure stripping
Strangulation………

When and how does cluster galaxies
quench the star formation activity?
Peng et al. 2010

Red Fraction“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)

From Koyama-san’s slideStar-formation in high-z galaxy clusters MAHALO-Subaru(Hayashi+10, 11)

Hα
z=0.4
CL0939 (Koyama+11)

Hα
z=0.8
RXJ1716 (Koyama+10)

Hα
[OII]

z=2.2

z=1.5
XCSJ2215

PKS1138(Koyama+13)(Tadaki+12)

[OII]
z=1.6
CL0218“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”Hαz=2.5
USS1558(Hayashi+12)

Masao Hayashi (NAOJ)

Role of gas in galaxy evolution
Gas-regulated model

Madau & Dickinson (2014)

Lilly et al. 2013

• Gas amount ?
• Efficiency to convert gas to stars ?
Saintonge et al. 2013

“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)

From Kodama-san’s slideGalaxy cluster: XMMXCS J2215.9-1738• z = 1.457• Extended X-ray emission• R200 = 0.8 Mpc• sv = 720 +/- 110 km/s
• Mcl = 2.8 x 1014 Msun

Stanford et al. (2006)

Hilton et al. (2010)“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)

Active star formation in the central region[OII] emission line galaxies detected bySubaru/Suprime-Cam narrowband imaging

850um sources detected by
JCMT/SCUBA-2 imaging

Hayashi et al. (2010, 2014)

Ma et al. (2015)

Several 24um sources are also detected by Spitzer/MIPS imaging (Hilton et al. 2010)“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)

ALMA observations
Band-3: 93-95 GHzCO(2-1) emission line from galaxies at z=1.430-1.478• Cycle 3• May 2016

• 3 pointings (2.33 arcmin2)• 1.04 hour integration
per each pointing“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)

Detection of CO(2-1) emission lines
from 17 cluster member galaxies“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)

Intensity map of CO(2-1) emission lines
All of the 17 CO(2-1) emitters have optical-NIR counterparts
 5 galaxies are sBzKs
 11 galaxies are [OII] emitters- 6 galaxies have spec-z- 5 galaxies have redshifts from NB912/NB921“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

A pair of two galaxies

Masao Hayashi (NAOJ)

Spatial distribution of galaxies with CO(2-1) emission line detectedclustercenter“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)

virialized

Phase space diagram

infalling“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)

Implications for the evolution of cluster galaxies• ram pressure stripping

Assumption:• strangulation
Stop feeding the fuel to the infalling galaxies

L’CO(2-1)/L’CO(1-0)=1
aCO = 4.36

MH2 = 2-9 x 1010 Msun

SFR([OII]) ~ 100 Msun / yr
Depletion time ~ 109 yr• Star formation

Exhaust the fuel for forming new stars“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)

SummaryHayashi et al., 2017, ApJL, 841, L21• XMMXCS J2215.9-1738 galaxy cluster at z=1.457• ALMA cycle-3 observations in Band 3• 17 CO(2-1) emission lines from the member galaxies• Phase space diagram CO emitters disappear from the very center of the cluster

 The gas-rich galaxies enter into the cluster more
recently than gas-poor SF galaxies or passive galaxies“Evolutionary Phases of Gas-rich Galaxies in a Galaxy Cluster at z = 1.46”

Masao Hayashi (NAOJ)