Statistical properties of di ff use Ly haloes around star-forming - - PowerPoint PPT Presentation

Rieko Momose（NTHU → U. Tokyo from next week）

Ouchi, M., Nakajima, K., Ono, Y., Shibuya, T., Shimasaku, K., Suraphong, Y., Mori, M., Umemura, M.

Momose+16, MNRAS, 457, 2318

Statistical properties of diffuse Lyα haloes around star-forming galaxies at z ~ 2

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY Cont. Lyα

2

New questions for the LAHs’ study

Steidel+11; Matsuda+12; MR+14; Wisotzki+16

What is the origin of LAHs? Which physical parameters of LAEs determine LAHs’ size?

param. Y N LUV

Zheng+11, Feldmeier+13, Xue+17, Leclercq+17 Steidel+11, Matsuda+12

LLyα

Xue+17, Zheng+11 Leclercq+17

MDH

Zheng+11

rs_cont

Leclercq+17 LAHs’ scale-length （kpc） LAE surface density mUV (ABmag)

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

3

Methodology of this study

Data

~ 3,500 LAEs at z = 2.2

Method

Make 5 subsamples as a function of LAEs’

• Lyα luminosity
• MUV
• EW0 (Lyα)
• UV-slope β

stack

Physical parameters (ex Lyα luminosity) LAH’s size

investigate the relation

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

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2 4 6 8 10 Radius [arcsec] 1 2 3 4 5 10 20 30 40 50 60 70 80

β = 0.68 β = −0.54 β = −1.4 β = −2.0 β = −2.6

2 4 6 8 10 Radius [arcsec] 1 2 3 4 5

log log log log log

10 20 30 40 50 60 70 80 Radius [kpc]

EW0 = 22 EW0 = 30 EW0 = 40 EW0 = 63 EW0 = 150

LLyα(r) / LLyα(r=1 arcsec) 2 4 6 8 10 Radius [arcsec] 1 2 3 4 5 10 20 30 40 50 60 70 80 Radius [kpc]

log(LLyα) = 42.6 log(LLyα) = 42.3 log(LLyα) = 42.1 log(LLyα) = 41.9 log(LLyα) = 41.7

LLyα(r) / LLyα(r=1 arcsec) 2 4 6 8 10 Radius [arcsec] 1 2 3 4 5 10 20 30 40 50 60 70 80

MUV= −21.1 MUV= −20.5 MUV= −20.1 MUV= −19.7 MUV= −18.9

LLyα(r) / LLyα(r=1 arcsec)

Lyα luminosity normalized in 2” aperture

Trend from all subsamples

LLyα increases in LAHs

LLyα, EW0

More extend in faint LLyα and small EW0 subsamples

MUV

More extend in bright MUV (if exclude two subsamples with large error-bars)

β

No clear trend

Cumulative radial profile of LLyα

log(LLyα) = 42.6 log(LLyα) = 42.3 log(LLyα) = 42.1 log(LLyα) = 41.9 log(LLyα) = 41.7

log log log log log EW0 = 22 EW0 = 30 EW0 = 40 EW0 = 63 EW0 = 150 MUV= −21.1 MUV= −20.5 MUV= −20.1 MUV= −19.7 MUV= −18.9 β = 0.68 β = −0.54 β = −1.4 β = −2.0 β = −2.6

LLyα EW0 MUV β

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

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LLyα

p = -0.9 (96%)

EW0

p = -0.7 (93%)

MUV

p = -0.2 (45%)

β

p = 0.7 (81%) Strong Corr. Corr. No clear Corr. Corr.

LAHs’ size

−3 −2 −1 1

UV slope β

5 10 15 20

rn (Lyα) [kpc]

Best Fit This Study

in a 1 arcsec radius 20 40 60 80 100 120 140 160

EW0(Lyα) [Å]

5 10 15 20

rn (Lyα) [kpc]

Best-fit This Study Matsuda et al. 2012

in a 1 arcsec radius

41.0 41.5 42.0 42.5 43.0

logL(Lyα)

5 10 15 20

rn(Lyα) [kpc]

Best Fit This Study Momose et al. 2014

in a 1 arcsec radius

[erg s-1]

−25 −24 −23 −22 −21 −20 −19 −18

M UV [mag]

5 10 15 20

rn (Lyα) [kpc]

Best-fit This Study Matsuda et al. 2012

in a 1 arcsec radius

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

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Origin of LAHs

LAE LAE

(a) Scattered light in the CGM (b) Cold streams (c) Satellite galaxies

・Stars ・ Lyα emission LAE

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

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We cannot rule out this scenario.

(a) Scattered light in the CGM

Origin of Lyα photons

• Produced in SF regions and/
• r AGNs
• Lyα escape mechanisms
• outflow
• clumpy clouds
• low column density

e.g. Neufeld 91, Verhamme+06, Dijkstra+12

Stellar Component

• f a galaxy

HI in CGM Observed Lyα emission

Observational evidences

• Spectroscopic observations have shown the evidence
• outflow
• low column density
• We cannot examine spectra or gas distribution from our data

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

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MDH~1011 MDH~1012 MDH~1013

Rosdahl & Blaizot 12

(b) Cold streams

Origin of Lyα photons

• Dense and clod gas (104 K) can emit in Lyα
• Produce an extended Lyα nebula around a galaxy
• size of the nebula depends on the dark halo mass MDH
• widely extend with 


MDH > 1012 M◉

• extend r ~ 20 kpc with


MDH ~ 1011 M◉

Comparison with our results 1

• MUV correlates with MDH
• Large LAHs are found in UV

luminous LAEs => consistent

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

8 Rosdahl & Blaizot 12

(b) Cold streams

Origin of Lyα photons

• Dense and clod gas (104 K) can emit in Lyα
• Produce an extended Lyα nebula around a galaxy
• size of the nebula depends on the dark halo mass MDH
• widely extend with 


MDH > 1012 M◉

• extend r ~ 20 kpc with


MDH ~ 1011 M◉

Comparison with our results 1

• MUV correlates with MDH
• Large LAHs are found in UV

luminous LAEs => consistent

2 4 6 8 10 Radius [arcsec] 1 2 3 4 5 10 20 30 40 50 60 70 80

MUV= −21.1 MUV= −20.5 MUV= −20.1 MUV= −19.7 MUV= −18.9

LLyα(r) / LLyα(r=1 arcsec)

Lyα luminosity normalized in 2” aperture

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

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(b) Cold streams

2 4 6 8 10 Radius [arcsec] 1 2 3 10 20 30 40 50 60 70 80 Radius [kpc] log EW0(Lyα) [Å]

MUV= −21.1 MUV= −20.5 MUV= −20.1

Comparison with our results 2

• EW0 of our MUV subsamples are 


lower than 77 Å => inconsistent

• maximum value for EW0 originating

from popII star formation is 240 Å

• if cold streams contributes LAHs,

EW0 at large radii should be larger than 240 Å

Our LAHs are not produced by cold streams.

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

satellite galaxy UV Lyα

Lake+15

(c) Satellite galaxies

Origin of Lyα photons

• Star forming regions in satellite

galaxies around LAEs

• If total radiation from satellite

galaxies is strong, they would produce extended Lyα emission

Comparison with our results

• If there are satellite galaxies, 


extended UV emission should 
 also exist in our stacked UV images

• Our stacked UV images 


suffer from sky-over subtraction

• It may cancel out the evidence 

• f satellite galaxies

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

satellite galaxy UV Lyα

Lake+15

(c) Satellite galaxies

Origin of Lyα photons

• Star forming regions in satellite

galaxies around LAEs

• If total radiation from satellite

galaxies is strong, they would produce extended Lyα emission

Comparison with our results

• If there are satellite galaxies, 


extended UV emission should 
 also exist in our stacked UV images

• Our stacked UV images 


suffer from sky-over subtraction

• It may cancel out the evidence 

• f satellite galaxies

We cannot rule out this scenario

INTRODUCTION METHODOLOGY RESULTS DISCUSSION SUMMARY

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Physical parameters of LAEs to determine LAHs’ size

LAHs’ sizes tend to be large with

• fainter in LLyα
• smaller in EW0
• brighter in MUV

Origin of LAHs

(a) Scattered light in the CGM ==> we cannot rule out (b) Cold streams ==> not the major contributor of our LAHs (c) Satellite galaxies ==> we cannot rule out

Summary

→ Haruka will discuss more details in her talk!

−1 1 2 3 4 5 6

δLAE

5 10 15 20 25 30 35

Matsuda+ 2012 Steidel+ 2011 This Study

rn (Lyα) [kpc]