A deep narrowband imaging search for Civand Heiiemission from Lyα blobs

Fabrizio Arrigoni Battaia, Yujin Yang, Joseph F. Hennawi, J. Xavier Prochaska, Yuichi Matsuda, Toru Yamada, Tomoki Hayashino

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13 Citations (Scopus)


We conduct a deep narrowband imaging survey of 13 Lyα blobs (LABs) located in the SSA22 proto-cluster at z ∼ 3.1 in the Civand Heiiemission lines in an effort to constrain the physical process powering the Lyα emission in LABs. Our observations probe down to unprecedented surface brightness (SB) limits of (2.1-3.4) × 10-18 erg s-1 cm-2 arcsec-2 per 1 arcsec2 aperture (5σ) for the Heiiλ1640 and Civλ1549 lines, respectively. We do not detect extended Heiiand Civemission in any of the LABs, placing strong upper limits on the He ii/Lyα and C iv/Lyα line ratios, of 0.11 and 0.16, for the brightest two LABs in the field. We conduct detailed photoionization modeling of the expected line ratios and find that, although our data constitute the deepest ever observations of these lines, they are still not deep enough to rule out a scenario where the Lyα emission is powered by the ionizing radiation from an obscured active galactic nucleus. Our models can accommodate He ii/Lyα and C iv/Lyα ratios as low as ≃0.05 and ≃0.07, respectively, implying that one needs to reach SB as low as (1-1.5) × 10-18 erg s-1 cm-2 arcsec-2 (at 5σ) in order to rule out a photoionization scenario. These depths will be achievable with the new generation of image-slicing integral field units such as the Multi Unit Spectroscopic Explorer (MUSE) on VLT and the Keck Cosmic Web Imager (KCWI). We also model the expected He ii/Lyα and C iv/Lyα in a different scenario, where Lyα emission is powered by shocks generated in a large-scale superwind, but find that our observational constraints can only be met for shock velocities vs 250 km s-1, which appear to be in conflict with recent observations of quiescent kinematics in LABs.

Original languageEnglish
Article number26
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2015 May 1


  • galaxies: formation
  • galaxies: high-redshift
  • intergalactic medium

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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