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Spatially Resolved Gas Kinematics within a Ly$alpha$ Nebula: Evidence for Large-scale Rotation | Moire K. M. Prescott
; Crystal L. Martin
; Arjun Dey
; | Date: |
10 Nov 2014 | Abstract: | We use spatially extended measurements of Ly$alpha$ as well as less
optically thick emission lines from an $approx$80 kpc Ly$alpha$ nebula at
$zapprox1.67$ to assess the role of resonant scattering and to disentangle
kinematic signatures from Ly$alpha$ radiative transfer effects. We find that
the Ly$alpha$, CIV, HeII, and CIII] emission lines all tell a similar story in
this system, and that the kinematics are broadly consistent with large-scale
rotation. First, the observed surface brightness profiles are similar in extent
in all four lines, strongly favoring a picture in which the Ly$alpha$ photons
are produced in situ instead of being resonantly scattered from a central
source. Second, we see low kinematic offsets between Ly$alpha$ and the less
optically thick HeII line ($sim$100-200 km s$^{-1}$), providing further
support for the argument that the Ly$alpha$ and other emission lines are all
being produced within the spatially extended gas. Finally, the full velocity
field of the system shows coherent velocity shear in all emission lines:
$approx$500 km s$^{-1}$ over the central $approx$50 kpc of the nebula. The
kinematic profiles are broadly consistent with large-scale rotation in a gas
disk that is at least partially stable against collapse. These observations
suggest that the Ly$alpha$ nebula represents accreting material that is
illuminated by an offset, hidden AGN or distributed star formation, and that is
undergoing rotation in a clumpy and turbulent gas disk. With an implied mass of
M(<R=20 kpc)$sim3 imes10^{11}$ $M_{odot}$, this system may represent the
early formation of a large Milky Way mass galaxy or galaxy group. | Source: | arXiv, 1411.2589 | Services: | Forum | Review | PDF | Favorites |
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