A submillimetre continuum survey of the galactic centre

Details A submillimetre continuum survey of the galactic centre A submillimetre continuum survey of the galactic centre

May 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002phdt.........8p&link_type=abstract

University of Cambridge : PhD. Dissertation.

Astronomy and Astrophysics

Astrophysics

2

Ism: Dust, Extinction, Galaxy: Center, Galaxy: Centre, Galactic Center, Galactic Centre, Ism: Clouds, Ism: Structure, Submillimeter, Submillimetre, Techniques: Image Processing

Scientific paper

The Galactic Centre is a site of exotic astrophysics on many scales, from the central black hole Sgr A* to the ~400 pc-wide Central Molecular Zone (CMZ). I present a submillimetre continuum survey at 850 micron and 450 micron of the CMZ made using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). The submillimetre continuum emission traces the temperature-weighted column density of dust grains, and hence molecular material, in a less biased way than molecular line maps.
This new survey covers a region 4 times larger and ~100 times deeper than earlier surveys. The SCUBA data form the first optically-thin map to trace essentially all the mass in the CMZ at high resolution and reveal that the CMZ is filled with filamentary dust structures. I attempt to characterise the mass spectrum of these structures with a clump-finding algorithm. I estimate the dust temperature throughout the CMZ by combining SCUBA data with IRAS far-infrared data, deriving a temperature ~20 K. I find that the 850 micron / 450 micron spectral index is alpha ~ 3--4, consistent with dust emission. I calculate a total molecular gas and dust mass in the CMZ of (53 +/- 10) x 10^6 solar masses. I also analyse the maps in conjunction with surveys at other wavelengths and characterise individual features. I measure the flux density of Sgr A* at both wavelengths and detect variability at 850 micron on ~year-timescales.
SCUBA scan map observations produce images convolved with a dual-beam function. I develop optimal techniques to reduce, mosaic, and deconvolve the survey. This leads to greatly improved image fidelity compared to previous such maps. I develop a Maximum Entropy technique for deconvolving SCUBA scan maps and discuss how it can be further improved.

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