Astronomy and Astrophysics – Astrophysics
Scientific paper
May 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006a%26a...451..539s&link_type=abstract
Astronomy and Astrophysics, Volume 451, Issue 2, May IV 2006, pp.539-549
Astronomy and Astrophysics
Astrophysics
20
Scientific paper
Context: .Characterizing the spatial and velocity structure of molecular clouds is a first step towards a better understanding of interstellar turbulence and its link to star formation. Aims: .We present observations and structure analysis results for a large-scale (~7.10 deg2) 13CO J = 2-1 and 12CO J = 3-2 survey towards the nearby Perseus molecular cloud observed with the KOSMA 3 m telescope. Methods: .We study the spatial structure of line-integrated and velocity channel maps, measuring the Δ-variance as a function of size scale. We determine the spectral index β of the corresponding power spectrum and study its variation across the cloud and across the lines. Results: .We find that the spectra of all CO line-integrated maps of the whole complex show the same index, β ≈ 3.1, for scales between about 0.2 and 3 pc, independent of isotopomer and rotational transition. A complementary 2MASS map of optical extinction shows a noticeably smaller index of 2.6. In contrast to the overall region, the CO maps of individual subregions show a significant variation of β. The 12CO 3-2 data provide e.g. a spread of indices between 2.9 in L 1455 and 3.5 in NGC 1333. In general, active star forming regions show a larger power-law exponent. We find that the Δ-variance spectra of individual velocity channel maps are very sensitive to optical depth effects clearly indicating self-absorption in the densest regions. When studying the dependence of the channel-map spectra as a function of the velocity channel width, the expected systematic increase of the spectral index with channel width is only detected in the blue line wings. This could be explained by a filamentary, pillar-like structure which is left at low velocities while the overall molecular gas is swept up by a supernova shock wave.
Bensch Frank
Kramer Carsten
Miller Matthew
Ossenkopf Volker
Stutzki Juergen
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