CHORUS. III. Photometric andSpectroscopic Properties of Ly𝛂Blobs at 𝑧=4.9-7.0
Haibin Zhang
University of Tokyo(Zhang et al. 2019; Submitted to ApJ)

2/13Introduction• Ly𝛂 blobs (LABs): luminous (log 𝐿'() ≳ 43.4) erg s-1) and spatiallyextended LAEs found at 𝑧 ≤ 6.6.
• Ly𝛂 halos (LAHs): around faint (log 𝐿'() ~42 − 43 erg s-1) LAEs
found at 𝑧 ~ 3 – 6 by VLT/MUSE (Leclercq+17).
• Connections between LABs and LAHs are unknown.

LABSame population

LAB Himiko at 𝑧 = 6.6(Ouchi+09)

LAH #547 at 𝑧 =5.98(Leclercq+17)(Leclercq+17)

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Data and Method• Imaging data: Subaru/HSC NB718 and NB973 from CHORUS
survey + NB and BB from SSP survey in COSMOS and SXDS fields.
• In total, 141 LAE candidates at 𝑧 = 4.9 selected by us + 34 LAE
candidates at 𝑧 = 7.0 from Itoh+18.
Two new LABs (z49-1 and z70-1) + five previously known LABs at𝑧 = 5.7 and 6.6.
z = 4.9z = 4.9 LAEz = 7.0

Data and Method

4/13• Snapshots of the 7 LABs:

Multiplecomponents
or mergers• NB (Ly𝛂) images are more extended than continuum images.
• Multiple components may be common among high-z LABs.

Data and Method

5/13• We unify the point spread functions (PSFs) to accurately extract
Ly𝛂 (NB − continuum) images, following

where FT means Fourier transform.

originalPSFs

PSFs aftermatchingData and Method

6/13• Two-component exponential function fitting:z57-2: offset between Ly𝛂and continuum centers
one-component fitting.

Data and Method• Spectra of the 7 LABs showing Ly𝛂 lines:• Redshifts of the 7 LABs are all confirmed.
• No other emission lines except CIV of z49-1.

7/13

Result and Discussion
1. Comparison of 𝑟6 between LABs and LAHs:• Typical high-z LABs are star-forming galaxies at the bright end.
• Our LABs do not have a significant redshift evolution of 𝑟6 .

8/13

Result and Discussion
2. Large scale structure around LABs
898:
• LAE overdensity 𝛿 = : , where 𝑛 is the number of LAEs in a8cylinder (𝑙=40 cMpc, 𝑟=10 cMpc).

• LABs in overdensed regions: 6/7.

9/13

Result and Discussion
2. Large scale structure around LABs
898:
• LAE overdensity 𝛿 = : , where 𝑛 is the number of LAEs in a
8cylinder (𝑙=40 cMpc, 𝑟=10 cMpc).

• LABs in overdensed regions: 6/7.
• No significant correlation between 𝑟6 and 𝛿.

9/13

Result and Discussion
3. Velocity gradients and FWHMs of the Ly𝛂 lines:• LAEs at 𝑧 = 5.7 and 6.6 have FWHMs of 100 – 400 km/s
(Ouchi+10, Shibuya+18b).
• Clearly z49-1 and z57-2 have relatively large velocity gradientsand FWHMs.
-> Possibly caused by AGNs (not likely for z57-2), mergers, and/ordense HI clouds.

10/13

Result and Discussion

11/13

4. AGN activity• No LAB shows X-ray and NV detections.
• CIV of z49-1: likely an AGN but can be
explained by a low-metallicity SFG.

(AGN and SFG Models from Nakajima+18)

5. H𝛂 Emission of z49-1• The 3.6 𝜇m band is not included in theSED fitting.
• H𝛂 luminosity: 3.6 ± 1.2 ×10BC erg s-1.
• Ly𝛂 escape fraction: 0.11 ± 0.04.

Result and Discussion

12/13

6. An Extremely Diffuse LAB at 𝑧=5.7• LAB z57-2 is more diffuse than theother LABs. Models cannot explain.
• Possibly caused by multiple clumps,mergers, or dense HI clouds.
(Halo-11 and Halo-12 from Yajima+17)

7. Physical origin of the extended Ly𝛂 emission around LABs(a) Resonant
scattering(b) Gravitationalcooling radiation(c) Satellite galaxies(d) Fluorescence(e) Outflows

Possible

Possible

Possible

Possible

Possible(Figures from Momose+16
and Fujimoto+19)

Summary13/13• We have identified 2 new LABs of z49-1 and z70-1, and z70-1 is themost distant LAB found to date.
• Typical high-z LABs are not special objects, but star-forming
galaxies at the bright end.
• We find that z49-1 and z57-2 have large Ly𝛂 velocity gradients andFWHMs, and that z57-2 is more diffuse than the other LABs.
• We find no evidence of AGNs in the 7 LABs except z49-1.
• The extended Ly𝛂 emission could be caused by resonant scattering,
gravitational cooling radiation, satellite galaxies, fluorescence, andoutflows.

Z70-1