SMC

From Tauwiki

1 Observations
2 Spectra of SMC diffuse observations
3 FUSE - FUSE Correlations
4 FUSE - UIT Correlations
5 Diffuse Fraction

[edit] Observations

There are 220 FUSE observations of SMC. We rejected all the observations in which point source observation is done by LWRS aperture. Then we were left with 46 observations. Finally, we checked the FWHM of the spectrum on the detector and left with 31 observations. For diffuse source FWHM is greater than 20 pixel.

All the 31 FUSE diffuse observations are shown (Figure 1) by circles with area proportional to the observed surface brightness (1A1 band flux of FUSE). The red circles are the UIT field of observations.

Figure 1 : R band image of SMC with diffuse observations

[edit] Spectra of SMC diffuse observations

The Data ID of the the 31 diffuse observations are here. A0750204, B1340202, C0830201, C0830302, C1580101, D9044301, D9044401, D9110901, E5110801, E5110802, F3210101, F3210103, F3210104, F3230101, F3230102, F3230103, F3230104, F3230105, F3230106, G0350101, G0350301, G9310201, G9310301, G9310401, G9310501, G9310601, G9310701, G9310801, G9310901, G9311002, P2030201, S4057101, S4057102.

Only 2 of the 4 detectors (1A and 1B) has been used for the measurement of the diffuse background as the sensitivity in 2B was too low to provide useful information and wavelength range of 2A overlaps with 1B. Both 1A and 1B covers the wave length range from 1085 A to 1180 A.

[edit] FUSE - FUSE Correlations

The are excellent correlations between the four FUSE bands: 1A1, 1A2, 1B1 and 1B2 (Figure : 2a, 2b, 2c, 2d) with correlation coefficients better that 0.95.

[edit] FUSE - UIT Correlations

Figure 3(a)

Figure 3(b)

Figure 3(c)

Figure 3(d)

31 diffuse targets are observed by FUSE and 9 of these are observed by the UIT B5 filter (1615 A). The UIT images are re binned to 27 x 27 pixel boxes to get the observed UIT flux and are compared with the FUSE bands. Figure 3(a, b, c, d) are the correlation plots of UIT-B5 band flux with FUSE 1A1, 1A2, 1B1 and 1B2 flux. The correlation coefficients, slopes of the best fits and offsets are mentioned on the top left corner of each plot. The four star clusters on the SMC Bar those are observed by UIT are NGC267, NGC292, NGC330 and NGC346 (shown in Figure 1). Number of stars whose FUV magnitudes derived from the PSF photometry by Cornet et al.(1997) are 1713 (ngc267), 2110 (NGC292), 2517 (NGC330), 4966 (NGC346).

[edit] Diffuse Fraction

Using the slope of the best fit line of the FUSE - UIT correlation, we have measured the fraction of the diffuse radiation which is diffuse radiation over the total radiation (diffuse + stellar). We have calculated this for each of the four UIT fields observed by Cornett et al.(1997). The stellar contribution to the total radiation field was calculated by summing the fluxes over all the UIT stars from Cornett et al.(1997) using Kurucz models (Kurucz 1992) to extend the stellar spectrum into the FUSE bands. We found the diffuse light is between 40% and 50% of the total light in this limited region of the SMC with an observed error of 20% - 30%.

Table containing diffuse fractions


Band		wavelength		n267		n346		n330		n292		SMC		LMC
1A1	---	1004	---	0.61	---	0.28	---	0.12	---	0.52	---	0.40	---	0.047
1A2	---	1058	---	0.66	---	0.33	---	0.15	---	0.57	---	0.45	---	0.071
1B1	---	1117	---	0.71	---	0.37	---	0.18	---	0.62	---	0.50	---	0.102
1B2	---	1157	---	0.69	---	0.36	---	0.17	---	0.61	---	0.48	---	0.122
UIT	---	1615	---	0.9	---	0.69	---	0.49	---	0.87	---	0.80	---	0.48

Diffuse fraction after subtraction the faint star contributions


Band		wavelength		n267		n346		n330		n292		SMC		LMC
1A1	---	1004	---	0.55	---	0.23	---	0.10	---	0.46	---	0.34	---	0.047
1A2	---	1058	---	0.6	---	0.28	---	0.12	---	0.51	---	0.39	---	0.071
1B1	---	1117	---	0.65	---	0.32	---	0.14	---	0.56	---	0.44	---	0.102
1B2	---	1157	---	0.64	---	0.30	---	0.13	---	0.55	---	0.39	---	0.122
UIT	---	1615	---	0.7	---	0.54	---	0.38	---	0.68	---	0.63	---	0.48