Galaxy Evolution Workshop 2018
@ Ehime University© Ehime Prefecture
みきゃん

Cross-Correlation Lyα Intensity
Mapping with z=5.7 and 6.6 LAEs:
Investigating Diffuse Lyα Emission
in the Extremely Large Scale
Lyα Cross-Correlation
at ~30-1000 kpc
Kakuma et al. in prep

Ryota Kakuma
The University of Tokyo
School of Science
Department of Astronomy

nulltest©NAOJ/HSC ProjectINTRODUCTION

Faint Galaxies and HI gas
Bright Galaxies

CGMØ Individually detected

Faint Galaxies

H Gas

Ø NOT Individually detectable

Hydrogen Gas
IGM
Faint Gal.

21cmLyαØ NOT detected z > 1with 21cm lineH Gas❑ Galaxy formation, evolution❑ Cosmic Reionization
Ø Surrounding Bright (detected) Galaxies©NAOJ

ü Cross-Correlation
Ryota Kakuma

Galaxy Evolution Workshop 2018/06/08

2

INTRODUCTION

Cross-Correlation Intensity MappingSource
Position

Cross
Correlation

not resolve

Intensity
Fluctuation
Breysse+16e.g.) ❏ Croft et al. 2016
− SDSS QSOs (𝑧%&' ∼ 2.55)

In thisstudy

LAEs (z~6)

Lyα ➔ Detect large scale signal

Lyα Cross Correlation

Ø First study using Intensity Mapping for the End of Reionization! To detect large scale Lyα signal or put an upper limit.

We want to "detect" Faint galaxies and/or Hydrogen gas
at z~6 with Intensity Mapping
Ryota Kakuma

Galaxy Evolution Workshop 2018/06/08

3

ANALYSIS

Data
The Hyper-Suprime-Cam Strategic Subaru Program

Area : 4 deg2

=×32 !!

UD COSMOS~2deg2

Source position

Intensityz = 5.7 LAEs

NB816
Image

z = 6.6 LAEs

NB921
Image

(N = 425)(N = 396)

Ryota Kakuma

UD SXDS~2deg2

Galaxy Evolution Workshop 2018/06/08

4ANALYSIS

Method (Cross-Correlation)

Mask
Image

Ryota Kakuma

Galaxy Evolution Workshop 2018/06/08

u Bad pixelu Cosmic ray
u S/N > 5 e.t.c...

5

ANALYSIS

Method (Cross-Correlation)

Mask
Masked Image

Ryota Kakuma

Galaxy Evolution Workshop 2018/06/08

u Bad pixelu Cosmic ray
u S/N > 5 e.t.c...

6

ANALYSIS

Method (Cross-Correlation)
LAEr
pixel
f
Uncertainty : σ(Systematics + Statistics)

Masked Image

w = 1/σ2f

Ryota Kakuma

Correlation between
random point and image

Galaxy Evolution Workshop 2018/06/08

7

RESULTS

Intensity Mapping

Errors are estimatedby jack-knife methodz = 5.7

z = 6.6

Kakuma et al. in prepExtended to ~1000 kpc ??
Any systematics mimicking the signals ?
Ryota Kakuma

Galaxy Evolution Workshop 2018/06/08

8RESULTS

Test for All systematic errors (null test)
Same mag
distribution

Source position

Non-LAEs

From G-dropout
samples in Ono+18

×100 times
LAEs

Cross
Correlation

Intensity

NB Images(NB816, NB921)

l PSF (atmosphere, instrument)l sky subtraction systematics
l unknown systematics

z = 5.7

LAEs

z = 6.6

Kakuma et al. in prep

Non-LAEs(null test)
Ryota Kakuma

Galaxy Evolution Workshop 2018/06/08

Non-LAEs(null test)
9zLyα5.6z = 5.7 LAEsz = 6.6 LAEs
NB(Lyα)Intensity

Z Image

Y Imagez = 5.7

During the last decades, Suprime-Cam (SCam) on theSubaru telescope has led the world on identifying such rare
Lyα-emitting populations at z >∼ 6 (LEW LAEs; e.g., Nagaoet al. 2008; Kashikawa et al. 2012; LABs; e.g., Ouchi et al.
2009; Sobral et al. 2015). However, the formation mechanismsof these rare Lyα-emitting populations are still controversial
due to the small statistics. While LEW LAEs and LABs atz ≃ 2 − 5 have been studied intensively with a sample of >∼ 100sources, only a few sources have been found so far at z >∼ 6.
Large-area NB data are required to carry out a statistical study
on LEW LAEs and LABs at z >∼ 6.

Kakuma et al. in prep

BB(cont.)

In March 2014, the Subaru telescope has started a largearea NB survey using a new wide field of view (FoV) camera, Hyper Suprime-Cam (HSC) in a Subaru strategic program(SSP; Aihara et al. 2017b). In the five-year project, HSCequipped with four NB filters of NB387, NB 816, NB921,
and NB 101 will survey for LAEs at z ≃ 2.2, 5.7, 6.6, and7.3, respectively. The HSC SSP NB survey data consist oftwo layers; Ultradeep (UD), and Deep (D), covering 2 fields(UD-COSMOS, UD-SXDS), and 4 fields (D-COSMOS, DD-DEEP2-3, D-ELAIS-N1), respectively. The NB816,
Galaxy EvolutionSXDS,
Workshop
2018/06/08
NB 921, and NB 101 images will be taken for the UD fields. The

Weaker than Lyα emission
Ryota Kakuma

Throughput

Source position

66.2Zz

i

0.4

0.2

6.4

6.6

NB921

Broad Band (Continuum)

0.6

5.8

NB816

ANALYSIS

2004; Prescott et al. 2009; Matsuda et al. 2009; Matsuda et al.
2011; Prescott et al. 2012a; Prescott et al. 2012b; Prescottet al. 2013; Cantalupo et al. 2014; Arrigoni Battaia et al.
2015b; Hennawi et al. 2015; Prescott et al. 2015; Arrigoni
Battaia et al. 2015a; Cai et al. 2017). The origins of LABs
(LAEs with a diameter ≃ 20 − 400 kpc) are also explained byseveral mechanisms: (1) resonant scattering of Lyα photons
Crossemitted from central sources in dense and extended neutral hyCorrelation
drogen clouds (e.g., Hayes et al. 2011), (2) cooling radiationfrom gravitationally heated gas in collapsed halos (e.g., Haimanet al. 2000), (3) shock heating by galactic superwind originatedfrom starbursts and/or AGN activity (e.g., Taniguchi & Shioya2000), (4) galaxy major mergers (e.g., Yajima et al. 2013), and(5) photoionization by external UV sources (QSO fluorescence;
e.g., Cantalupo et al. 2005). Moreover, LABs have been often
discovered in over-density regions at z ≃ 2 − 3 (e.g., Yang et al.
2009; Yang et al. 2010; Matsuda et al. 2011). Thus, such LABs
could be closely related to the galaxy environments, and might
be liked to the formation mechanisms of central massive galaxies in galaxy protoclusters.

6.8

YyContinuum

08000

8500

90009500λ [Å]Fig. 1. Filter transmission curves of the NB and BB filters. The red and blue
curves represent the NB921 and NB816 filters, respectively. The red and blueticks show the NB central wavelengths with the same color coding as for theNB filter transmission curves. The black solid curves indicate the i, z, andy-band filters, from left to right. The gray line denotes the OH sky lines
The bandpass of these NB and BB filters corresponds to the area-weighted
mean transmission curves1 . The transmission curves are derived by taking
into account 1) the quantum efficiency of CCD, the transmittance of 2) thedewar window and 3) the HSC primary focus unit (POpt2), 4) the reflectivityof the primary mirror, and 5) the sky transparency (see Aihara et al. 2017a)
The upper x-axis corresponds to the redshift of Lyα.

NB(Lyα)z = 6.6BB(cont.)

troscopic properties of bright LAEs (Shibuya et al. 2017b)
Lyα luminosity functions (Konno et al. 2017), and LAE overdensity (R. Higuchi et al. in preparation). The LAE survey strategy is given by Ouchi et al. (2017). This program is
one of the twin programs. Another program is the study for
dropouts, Great Optically Luminous Dropout Research Using
Subaru HSC (GOLDRUSH), that is detailed in Ono et al(2017), Harikane et al. (2017), and Toshikawa et al. (2017).

This is the second paper in the SILVERRUSH project. In
this paper, we present LAE selection processes and machinereadable catalogs of the LAE candidates at z ≃ 5.7 − 6.6. Usingthe large LAE sample obtained with the first HSC NB data, we
examine the redshift evolutions of Lyα EW distributions andLAB number density. This paper has the following structure. In
10Section 2, we describe the details of the SSP HSC data. Section

Sorounding faint galaxies➔ also LAE like galaxies

DISCUSSION

Comparison with previous studies
Leclercq+17(MUSE)
Kakuma et al. in prep

Momose+14This Study
1stcomponent
rs ~ 0.4 pkpc
“Disk like”

Ryota Kakuma

2ndcomponent
rs ~ 6 pkpc
“LAH”

Galaxy Evolution Workshop 2018/06/08

3rd component“???”

11DISCUSSION

The origin of Lyα structure
Lyα

Hα

Scatteringby HI

Cold gas
Streams

UV (continuum)

FaintGalaxies

Fluorescent! Very sensitive to CGM, IGM (H gas) parameters

LAE like galaxies! No simulation which realizes Lyα emission
extending to ~1pMpc around LAEs with these

Kakuma et al. in prep

ü Need more information & Simulationcont.

Ryota Kakuma

Galaxy Evolution Workshop 2018/06/08

Lyα12

DISCUSSION

𝜉76

Faint LAEs Clustering

𝜖-23

𝜉76 = 𝑏-./ 𝑏0,-./ 𝜇-23 𝜉56
Ø 𝑏-./ : Bias for LAEs (~ 4)Ø 𝑏0.-./ : Bias for faint LAEs ➔ Assume same as 𝑏-./Ø 𝜇-23 : Mean surface brightness of Lyα emissionØ 𝜉56 : Dark Matter Auto Correlation Function

Came from faint LAEs
∵ Detected LAEs are
MaskedLyα Cross-Correlationz = 5.7
Kakuma et al. in prep

G-drop(null test)
Ryota Kakuma

Galaxy Evolution Workshop 2018/06/08

Kakuma et al. in prep
[erg/s/Å/cm2/arcsec2]
Kakuma et al. in prep

[erg/s/Mpc3]

Cosmic Lyαluminosity density
13

DISCUSSION

Comparing with Luminosity Functionu This study

LF
𝜖-23

u Konno +18 (same LAE sample)z = 5.7

Steep faint end (α)α = −2.56

Cross-Correlation
Intensity Mapping←extrapolate

α = −2
α = −1.5

Kakuma et al. in prep
[erg/s/Mpc3]

Comparable
Ryota Kakuma

39.5

42(obs. limit)

𝜖-23 ∼ 6.1 × 10?@ [erg/s/Mpc3]

Galaxy Evolution Workshop 2018/06/08

14DISCUSSION

Cosmic SFR density

𝜉76

𝜌BCD

𝜖-23𝜖-23= 𝜅-23I@IL[erg s I@ Mpc IL ]M⊙ yr Mpc
𝜌BCD

( 𝜅-23 = 9.1 × 10I?L )[M◉/yr/Mpc3] (z=5.7)
Kakuma et al. in prep
Madau +14

❑ 𝜿𝑳𝒚𝜶 is different for high-z, faint galaxies①
Ø Top heavy IMF, low metallicity, high escape fraction, etc.
− More Lyα (ionizing) photons are emitted❑ There is also②other contribution with HI

Ryota Kakuma

Scattering
Galaxy Evolution Workshop 2018/06/08

Cold Streams

Fluorescent15

SummaryLadies and gentlemen…

We did it !

© David Reitzl We detect Lyα Large scale structure(~ 1000 pkpc) @ z = 5.7 & 6.6
for the first time !
l The origin of this extended
Lyα is under debate− BothFaint LAEs & HI gas ??
Ryota Kakuma

Galaxy Evolution Workshop 2018/06/08

Lyα Cross-Correlation
Kakuma et al. in prepnulltest16