Madhu Sudan Paudel
In this work I have studied the far infrared spectra of the dust structure around the White Dwarf 0352-049 available in Sky view virtual observatory (http://skyview.gsfc.nasa.gov) in Infrared Astronomical Satellite map. There is Gaussian like distribution of relative flux density in both 100 micron and 60 micron FITS image. The temperature of the whole dust structure lies between maximum 24.09 K to minimum 21.87 K with fluctuation of 2.22K and average value 23.09 K. The distribution of temperature is also Gaussian in nature. The small fluctuation and Gaussian distribution of temperature suggests the dust structure is evolving independently and the less disturbance from external sources. The total dust mass of the structure is found to be 0.07 times Solar mass and that of gas is 13.66 times Solar mass. The Jeans mass of the structure is 5.25 times Solar mass, less than the total mass of gas in the structure, suggesting the possibility of formation of star by gravitational collapse in future. The size of structure is 24.48 parsec × 8.10 parsec. Also the study of inclination angle suggests that the three-dimensional shape of structure is uniform and regularly shaped.
1. Contour Map
The FITS image at 60 μm and 100 μm taken from Sky view virtual observatory is processed in ALADIN 9.0 software. We draw two contours with level 47 and 20, all 792 pixels inside outer contour 47 are included for study. The relative infrared flux at 60 and 100 μm are extracted using ALADIN 9.0.
2. Contour Plot: Relative Flux Density
The variation of relative infrared flux is studied using contour plot. Separate plots are drawn for 60 μm and 100 μm image. A linear relationship between these two fluxes can give the average temperature of the structure. The similarities observed in the relative flux at 60 and 100 μm might be due to the blackbody emission from large dust presence within the structure.
3. Dust Color Temperature and Mass Estimation
The dust color temperature and mass of each pixels are calculated by following Schnee et al. (2005) and Hildebrand et al. (1983) respectively. The temperature and mass distribution within the structure is observed. The maximum and minimum temperature within the structure is found 24.09 K and 21.87 K, with range 2.22.K and average value 23.09 K.
The slope linear plot between for 60 μm and 100 μm flux can also gives the average temperature of the structure, which is 23.69 K. The average value of temperature from both method are nearly equal.
For the calculation of dust mass we use the distance to the structure 1219 pc using SIMBAD. The total dust mass of all pixels with the structure is 1.36 × 10^29 kg (0.07 Solar Mass) and mass of gas is 2.72 × 10^31 kg (13.66 Solar Mass).
3. Gaussian Plot of Flux, Temperature and Mass
There are 792 pixels within the dust structure. The data of flux, temperature and mass of each pixels are binned in appropriate size to study the nature of data. The graph for Gaussian fit of flux at 60 μm and temperature show Gaussian nature and flux at 100 μm and mass are slightly deviated from Gaussian nature.
From Gaussian fit of temperature, we can conclude that the temperature distribution is symmetric and effect of external radiation sources in background is very small.
4. Size, Inclination Angle and Jeans Mass
The angular dimension of the structure (69.0 arcsec × 22.84 arcsec) is converted into linear dimension by using the formula of circle; l=d×θ, where, l is the linear and θ is angular size and d is the distance, 1219 pc. The size of structure is; 24.48 pc × 8.10 pc.
The inclination angle is calculated using Holmberg (1946) formula. Which varies uniform and regular manner from inside to outside representing the dust structure is uniformly shaped and regularly structured.
The Jeans mass of the structure is 1.04 × 10^31 kg (5.25 Solar Mass), which is less than the total mass of gas (13.66 Solar Mass) within the structure. This suggest the possibility of the star formation activity in future.