第3回銀河進化研究会: 2016/6/1-3 @東北大学

Cosmic Galaxy-IGM HI Relation at z~2-3
probed in the COSMOS/UltraVISTA
Shiro Mukae(ICRR),
Masami Ouchi(ICRR), Koki Kakiichi(MPA), Nao Suzuki(Kavli IPMU),
Yoshiaki Ono(ICRR), Zheng Cai(Arizona Univ.),

Akio K. Inoue(Osaka Sangyo Univ.), Yi-Kuan Chiang(Texas Univ.),
Takatoshi Shibuya(ICRR), Yuichi Matsuda(NAOJ)

Baryonic processes in the large scale structures• baryonic processes

between galaxies and the intergalactic medium (IGM)

in the large scale structures(LSSs)

is a clue to understand the galaxy formation

Gas Density

R.Cen22

HI is probed with Lyα forest absorptions• Neutral hydrogen HI in IGM is probed with Lyα forest absorptionsin spectra of background quasars (+bright star-forming galaxies)• Multiple sightlines provide the spatial distribution of HI gas

̶>Recent active studies illustrate the distribution of HI in LSSs

Lyα forest tomography (KG. Lee+14,+16) —> KG’s talkWe would like to know;what is galaxy-HI relation in large-scale like?
MAMMOTH (Cai+15)

3What is galaxy-HI relation in large-scale like?
• We investigate spatial correlations of galaxies and HI

in the COSMOS/UltraVISTA ﬁeld covering the 1.62deg2• Compiled photo-z galaxies & Background quasars from SDSS
credit:BOSS

Background QSOs
from the SDSS-III

1.62deg2
search for absorption lines

Galaxies fromCOSMOS/UltraVISTA

credit:BOSS
credit:SDSS.org

credit:esa

Data• COSMOS/UltraVISTA(1.62deg2)• 13,415 photo-z galaxies at z~2-3⚫zgal~2-3 ⚫zQSO~2.3-3.5

with Ks < 23.4 (Muzzin+13)• 9 (out of 26) background quasar spectrafrom BOSS&SDSS (KG+13, Alam+15)• We do not use spectra with damped Lyαsystems(DLAs)
broad absorption lines(BALs)

❌DLA
Lyβ
contamination

proximity
effectLyα forest wavelength range: 1041-1185Å in the quasar rest frame

Galaxy and HI Overdensity Estimation
Noemalized flux

Example spectra of background QSO

HI absorption Estimation:: cosmic mean flux (FG+08)〈Ｆ〉dz
Background QSO: Galaxyr = 5 arcmin(~2.5 pMpc at z~2.5)

Chiang+14zabsdz = σz = 0.025(1+z)

Galaxy Overdensity Estimation:

The height of the cylinder along the line of sight is given by
the average photometric redshift uncertainty

Galaxy and HI Overdensity Estimation
Noemalized flux

Example spectra of background QSO

HI absorption Estimation:: cosmic mean flux (FG+08)

〈Ｆ〉dz

〈Ｆ〉dz

〈Ｆ〉dz

〈Ｆ〉dz
Background QSO: Galaxyr = 5 arcmin(~2.5 pMpc at z~2.5)

Chiang+14

zabs

zabs

zabszabs

dz = σz = 0.025(1+z)

Galaxy Overdensity Estimation:

The height of the cylinder along the line of sight is given by
the average photometric redshift uncertainty

Galaxy-IGM HI Correlation: cosmic mean flux (FG+08)

Strong HI Absorption

HI absorption Estimation:

Observations

Galaxy Overdensity• a spatial anti-correlation betweenand• Spearmanʼs rank correlation coeﬃcients= - 0.39 (~90% c.l.)• high-z galaxies exist around an excess of HI gas in the Lyα forest

10Strong HI Absorption

Simulated Galaxy-IGM HI Correlationsightline

Simulations: z=2.4-2.5
Galaxy Overdensity••

Volume (80 h-1cMpc)3 5123cells
DM halo̶> mock galaxy:
Abundance Matching & SHMR
Lyα transmitted ﬂux: FGPA

Cosmological hydrodynamical simulation with the RAMSES codea weak anti-correlation agreeing with the observational results

11Strong HI Absorption

Simulated Galaxy-IGM HI Correlation

Galaxy Overdensity•We ﬁnd 4 cosmic volumes that have extremely large(small) values

12Simulated Galaxy-IGM HI Correlation
Strong HI Absorption

Simulations

Galaxy Overdensity⚫ mock galaxy
Background color: projected• We use the simulations and search for cylinders whose

value are similar to the 4 cylinders from observation results-13Four Cylinders with an extreme value:
Physical origin?
Cylinder A:

Aobs coincides with one of the proto-cluster candidates (Chiang+14)

a large galaxy overdensity is associated with the large amount of HI gas

Asim penetrates
a galaxy overdensity

Four Cylinders with an extreme value:
Physical origin?
Cylinder A:

Aobs coincides with one of the proto-cluster candidates (Chiang+14)

a large galaxy overdensity is associated with the large amount of HI gasA

map investigated by photo-z (Chiang+14)

Four Cylinders with an extreme value:
Physical origin?
Cylinder B:

Bsim goes through gas ﬁlaments

Bobs would penetrate gas ﬁlaments with moderate number of galaxies

Bsim penetrates
gas filaments

Four Cylinders with an extreme value:
Physical origin?
Cylinder C:

Csim penetrates a large void of LSSs and goes across a gas ﬁlament
Cobs would penetrate large void and go across a gas ﬁlament

photo-z is catastrophic

Csim penetrates
a large void of LSSs
and goes across gas filaments

Four Cylinders with an extreme value:
Physical origin?
Cylinder D:

Dsim penetrates low density ﬁlaments

Dobs would through the orthogonal low-density ﬁlaments

Dsim penetrates
orthogonal low density filaments

Possible physical pictures
filamentary large-scale structures••

simulations suggest that the observations would penetrate...
a galaxy overdensity like a proto-cluster, gas ﬁlaments, a large void,and orthogonal low-density ﬁlaments
ﬁlamentary large-scale structures and observations sightline eﬀects

19Summary
We investigate spatial correlations of galaxies and IGM HI
in the COSMOS/UltraVISTA 1.62 deg2 ﬁeld at z~2-3
1. an weak anti-correlation between δgal and δ〈F〉
conﬁrmed by both observation and simulations

2. 4 cosmic volumes that have extremely large(small) values:
sightlines would penetrate a galaxy overdensity/ﬁlaments/a large void/orthogonal low-density ﬁlaments
Ongoing Work:HETDEX(Hobby Eberly Telescope Dark Energy Experiment)
2434deg , z=1.9-3.5, 0.8M LAEs
“Correlation studies of z~2-3 LAEs and HI/metal absorbers“
from Taft’s slides (Mukae, Ouchi, Schulze, HETDEX Collaboration)