title: Power Spectrum Analysis of OMC1 in the Orion A Molecular Cloud at 1.1 mm

authors: Soyoung Youn and Sungeun Kim

abstract: We present a 1.1 mm emission map of the OMC1 region observed with AzTEC, a new
large-format array composed of 144 silicon-nitride micromesh bolometers that
was in use at the James Clerk Maxwell Telescope (JCMT). The AzTEC observations
of the OMC1 region at 1.1 mm reveal dozens of cloud cores and a tail of
filaments in a manner that is almost identical to the submillimeter continuum
emission of the entire OMC1 region at 450 and 850 micronm. We performed
Fourier analysis of the image with a modified periodogram and the density
power spectrum which provides the distribution of length scale of the structure is 
measured. The expected value of the periodogram converges to the
resulting power spectrum in the mean squared sense. From the present analysis
of the OMC1 filaments at the 1.1 mm emission, the power spectrum steepens at
relatively smaller scales. At largest scales, the power spectrum flattens and
the large scale power law becomes shallower. The power spectra of the 1.1 mm
emission show clear deviations from a single power law. We find that at least
three components of the power law might be fitted to the calculated power spectrum of 
the 1.1 mm emission. The slope of the best fit power law, $\gamma \approx - 2.7$ at 
intermediate scales is similar to those values in numerical
simulations. The effects of beam size and noise spectrum on the shape and the 
slope of the power spectrum are also included in the present analysis. The
slope of the power law changes significantly at higher spatial frequency as
the beam size increases.

We are grateful to the AzTEC team members. The James Clerk Maxwell Telescope
is operated by the Joint Astronomy Center on behalf of the Science and
Technology Facilities Council of the United Kingdom, the Netherlands
Organization for Scientific Research, and the National Research Council of
Canada. We appreciate for helpful comments from colleagues. This work was
supported in part by Mid-career Researcher Program through the National
Research Foundation of Korea (NRF) funded by the Ministry of Education,
Science and Technology 2011-0028001.