Chang You, Ann Zabludoff, Paul Smith, Yujin Yang, Eunchong Kim, Buell Jannuzi, Moire K.M. Prescott, Yuichi Matsuda, Myung Gyoon Lee

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Lyα nebulae, or "Lyα blobs," are extended (up to ∼100 kpc), bright (L Lyα1043 erg s-1) clouds of Lyα emitting gas that tend to lie in overdense regions at z ∼ 2-5. The origin of the Lyα emission remains unknown, but recent theoretical work suggests that measuring the polarization might discriminate among powering mechanisms. Here we present the first narrowband imaging polarimetry of a radio-loud Lyα nebula, B3 J2330+3927, at z = 3.09, with an embedded active galactic nucleus (AGN). The AGN lies near the blob's Lyα emission peak, and its radio lobes align roughly with the blob's major axis. With the SPOL polarimeter on the 6.5 m MMT telescope, we map the total (Lyα + continuum) polarization in a grid of circular apertures of a radius of 0.″6 (4.4 kpc), detecting a significant (>2σ) polarization fraction P % in nine apertures and achieving strong upper limits (as low as 2%) elsewhere. P % increases from <2% at ∼5 kpc from the blob center to 17% at ∼15-25 kpc. The detections are distributed asymmetrically, roughly along the nebula's major axis. The polarization angles θ are mostly perpendicular to this axis. Comparing the Lyα flux to that of the continuum and conservatively assuming that the continuum is highly polarized (20%-100%) and aligned with the total polarization, we place lower limits on the polarization of the Lyα emission P %,Lyα ranging from no significant polarization at ∼5 kpc from the blob center to 3%-17% at 10-25 kpc. Like the total polarization, the Lyα polarization detections occur more often along the blob's major axis.

Original languageEnglish (US)
Article number182
JournalAstrophysical Journal
Issue number2
StatePublished - Jan 10 2017


  • galaxies: active
  • galaxies: high-redshift
  • galaxies: individual (B3 J2330+3927)
  • intergalactic medium
  • polarization

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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