Exploring Sites of Galaxy Formation: Large Lya Nebulae at z~2-3
Moire Prescott (University of Arizona)
Large (>100 kpc) Lya nebulae or 'Lya blobs' are likely sites of ongoing massive galaxy formation. They have been found in small numbers around z~2-3, a key epoch of galaxy and black hole growth, but many fundamental questions remain about their environments, space density, and excitation mechanisms. While many Lya nebulae have been discovered via narrowband imaging of known overdensities, one of the largest Lya nebulae was discovered in the NOAO Deep Wide-Field Survey (NDWFS) without any a priori knowledge of its environment, offering an unbiased test of the association between Lya nebulae and overdensities. Using deep intermediate-band imaging we find that this Lya nebula is sitting within a factor of 3 overdensity of Lya-emitting galaxies and rule out a chance coincidence at the <1% level. To constrain the space density of these rare sources, we conducted a systematic search for other large Lya nebulae within the 9 square degree NDWFS broadband imaging. The survey covers a large redshift range (z=1.9-2.9) and has yielded the first strong lower limit on the space density of large Lya nebulae. Detailed multi-wavelength analysis of two individual sources - including the first Lya nebula discovered with strong, spatially-extended HeII emission - reveals complex systems that contain obscured AGN, young galaxies, evidence for spatially-extended star formation, and in at least one case, the possibility of low metallicity gas. Studying the detailed physical conditions within these sources will greatly inform our understanding of the physics of massive galaxy formation.
Contact: J. Rigby
Moire Prescott (University of Arizona)
Large (>100 kpc) Lya nebulae or 'Lya blobs' are likely sites of ongoing massive galaxy formation. They have been found in small numbers around z~2-3, a key epoch of galaxy and black hole growth, but many fundamental questions remain about their environments, space density, and excitation mechanisms. While many Lya nebulae have been discovered via narrowband imaging of known overdensities, one of the largest Lya nebulae was discovered in the NOAO Deep Wide-Field Survey (NDWFS) without any a priori knowledge of its environment, offering an unbiased test of the association between Lya nebulae and overdensities. Using deep intermediate-band imaging we find that this Lya nebula is sitting within a factor of 3 overdensity of Lya-emitting galaxies and rule out a chance coincidence at the <1% level. To constrain the space density of these rare sources, we conducted a systematic search for other large Lya nebulae within the 9 square degree NDWFS broadband imaging. The survey covers a large redshift range (z=1.9-2.9) and has yielded the first strong lower limit on the space density of large Lya nebulae. Detailed multi-wavelength analysis of two individual sources - including the first Lya nebula discovered with strong, spatially-extended HeII emission - reveals complex systems that contain obscured AGN, young galaxies, evidence for spatially-extended star formation, and in at least one case, the possibility of low metallicity gas. Studying the detailed physical conditions within these sources will greatly inform our understanding of the physics of massive galaxy formation.
Contact: J. Rigby
