FirstLMCpaper
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[edit] Observations of the Diffuse Background in the Large Magellanic Cloud
[edit] Introduction
The Magellanic Clouds provide a very different view of the interstellar medium than is possible from either within the Milky Way or from other, more distant, galaxies. Unlike the Milky Way, we can get an overall view of the interstellar medium without being confused by the small scale structure. At the same time, we can distinguish between the different sources, particularly between the stars and the dust which is not possible in more distant galaxies. This was used to great advantage by Cole et al. (1999) in developing a three-dimensional scattering code for the analysis of the observed radiation. They found a fairly complex relationship between the diffuse radiation in the LMC and the star and dust distribution. It is not sufficient to merely have bright stars or to have dust: both must be present to show scattered light.
The diffuse light escaping from galaxies is a diagnostic of the amount of dust and the interaction of the radiation field with the dust. It will affet the appearance of external galaxies and will affect the amount of radiation escaping to ionize the intergalactic medium (IGM)..
We have previously (Murthy & Sahnow 2005) shown that the Far Ultraviolet Spectroscopic Explorer (FUSE) can be used for observations of diffuse sources brighter than about 2000 photons cm-2 s-1 sr-1 A-1. As a result, we decided to look for serendipitous observations of the diffuse radiation in places where the signal may be expected to be bright. One such location was the Large Magellanic Cloud (LMC) where we identified a number of observations where the
The Large Magellanic Cloud provides an ideal location to probe the scattering of starlight by interstellar dust grains. It is far enough away that local effects are not one of the best studied galaxies in the Universe. It is a small irregular galaxy which is a companion to our own Milky Way. Because it is so close, the different components can be studied in great detail.
We have obtained the first diffuse observations in the far ultraviolet (FUV) of the radiation field in the LMC. We have obtained a total of 52 observations of xx locations. These are plotted on an optical map of the LMC in Fig. 1 with the UIT data overplotted as circles.
[edit] Observations and Data Analysis
We have obtained a total of 52 observations of 38 independent locations from the FUSE archives until xx. These observations are shown on an optical map of the LMC in Fig. 1. Most of these observations were as the result of MDRS pointings within the LMC but a few were calibration observations (S405/S505).
FUSE on IRAS:
Our data analysis has been fully discussed by Murthy & Sahnow (2002). We break up the FUSE focal plane into bands and extract the values from those bands. The presence of stars is revealed by the FWHM of the slit profile which is much less for a point source than for a diffuse source. We have excluded all such observations. The bands are listed in Table 1.
[edit] Results
We have discovered intense far ultraviolet emission from within the Large Magellanic Cloud. The values at 1156 A are superimposed on an IRAS image of the LMC in Figure 1. Because our observations are serendipitous, they are concentrated around "interesting regions" which are observed for other reasons.
[edit] Task List
Here is the list of things to do to complete the paper, I will note them here and update results in the upper draft for paper, and cancel the Tasks as we go along:
1. To get the plot of FUSE locations on an optical map of LMC.[This will be Fig. 1] The data should be circles with radius proportional to UV intensity.
2. Where are the locations of FUSE observations centered around?
3. Confirming match of our FUSE observations with NUV observations:- reading WISP paper and using fits file by Dr. Cole.
4. Making the list of FUSE bands. [This will be Table 1].
