SPECTROPOLARIMETRY CONFIRMS CENTRAL POWERING IN A Ly alpha NEBULA AT z=3.09

• We present a follow-up study to the imaging polarimetry performed by Hayes et al. on LAB1 in the SSA22 protocluster region. Arguably the most well-known Ly alpha blob, this radio-quiet emission-line nebula likely hosts a galaxy that. either is. undergoing significant star formation or hosts an active galactic nucleus, or both. We obtain deep, spatially resolved spectropolarimetry of the Ly alpha. emission and detect integrated linear polarization of 9%-13% +/- 2%-3% at a distance of approximately 15 kpc north and south of the peak of the Ly alpha. surface brightness with polarization vectors lying tangential to the galactic central source. In these same regions, we also detect a wavelength dependence in the polarization that. is low at the center of the Ly alpha. line profile and rises substantially in the wings of the profile. These polarization signatures are easily explained by a weak outflowing shell model. The spectral dependence of the polarization presented here provides a framework for future observations and interpretations of the southern portion of LAB1 in that any model for this system must be able to reproduce this particular spectral dependence. However, questions still remain for the northernmost spur of LAB1. In this region we detect total linear polarization of between 3% and 20% at the 5% significance level. Simulations predict that polarization should increase with radius for a symmetric geometry. That the northern spur does not suggests either that this region is not symmetric (which is likely) and exhibits variations in columns density. or that it is kinematically distinct from the rest of LAB1 and powered by another mechanism altogether.

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Nyckelord

galaxies: evolution

galaxies: formation

galaxies: high-redshift

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