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\subsection{Fourier Statistics} VCA/VCS, delta variance, MVC, SPS/Bicoherence, wavelet
%Just %SSRO Just use the +Text to create a new separated text box for each category (here \subsubsection{}) into it.
\subsubsection{Velocity Channel Analysis and Velocity Coordinate Spectrum}
\label{VCA}
%SSRO Note power spectra - lower case; to cite text add label as \label{VCA} and then add (e.g., \ref{VCA}) in the text
Velocity Channel Analysis (VCA) and Velocity Coordinate Spectrum (VCS) are techniques that isolate how fluctuations in velocity contribute to differences between spectral
cubes (cite Authorea text?). cubes. VCA
yields (wc?) produces a 1D
Power Spectrum power spectrum as a function of spatial frequency, while VCS yields a 1D
Power Spectrum power spectrum as a function of velocity-channel frequency (frequency equivalent of velocity). For runs W1T2t0.2 and W2T2t0, we compute the three-dimensional
Power Spectrum power spectrum (of their Fourier transforms). To obtain the VCA, we calculate a one-dimensional
Power power spectrum by integrating the 3D
Power Spectrum power spectrum over the velocity
channels, channels and then radially averaging over the two-dimensional spatial frequencies. A portion (look back when you get a chance to see what this portion physically is) of the now
1-D Power Spectrum 1D power spectrum is then fit to a power law. We derive the VCS from different integration techniques. We reduce each
3-D Power Spectrum 3D power spectrum to one dimension by averaging over the spatial frequencies. The VCS yields two distinct power laws that correspond to certain (different?) simulation (cloud?) parameters driving gas motion at different scales. The fit at larger scales describes bulk gas velocity-dominated motion; the fit at smaller scales describes gas density-dominated motions (Chepurnov and Lazarian 2009). To
quanity quantity the VCS, we fit the 1D power spectrum to the segmented linear model used Koch et al. (2015) (or cite the paper describing the model?).
We Figures 5 and 6 show the VCA and VCS power law fits for runs W1T2t0.2 and
W2T2t0 in Figures 5 and 6. W2T2t0. VCA generates similarly sloped power laws for
our Power Spectra, both runs, but there is
also a constant horizontal
offset between them. At offset. This implies that at all spatial scales,
we find that run W1T2t0.2, our run with feedback,
generates has more energy than that of run W2T2t0, our run without feedback. The VCS also shows a horizontal offset between
our runs, the two curves, confirming that
there is more power in velocities at all scales
generate more energy in the case with
feedback than without it. feedback. We also note a difference in both VCS power-law fits, and, more
apparent, importantly, the break point between the two fits.
Our {\bf the breakpoint: what it means and how it is determined needs to be described. The specific position and how this corresponds to a spatial or velocity scale needs to be noted: e.g. box size ~ 1 = 5pc, so k=0.1 = 0.5 pc; velocity range = +/-20 km/s, so k=0.1 is ~ 2 km/s. }
The run without feedback (our purely turbulent run? Go back and denotes everything like this?) appears to
be more affected have a larger range over which it is dominated by
changes in bulk gas velocity
than it fluctuations ($k\simeq 1-0.05$). The velocity-dominated regime is
smaller for
changes in gas density. For our the run with
feedback, this appears to be less drastic, as feedback ($k\simeq 1-0.1$), such that changes in gas density affect a greater portion of the
cloud structure
in the cloud emission.% (here than in the other run...trying to be grammatically correct with comparisons while including sentence variation--not sure if this sentance is grammatically correct).
%SSRO Good job. made some small edits to address content.