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[edit] Emission from HVC in the GALEX fields

Fig.HVC-NUV. Correlation between HVC and the NUV emission.

Fig.HVC-FUV. Correlation between HVC and the FUV emission.

Fig.HVC-FOV. HVC HI map in the SFL field & GALEX FOV.

The HI map shown in Fig.4 is the integrated emission over all velocities in the field. Lockman and Condon (2005) extracted different components like LVC, IVC & HVC in the field and is shown in Fig. NHI. The High velocity cloud (HVC) present in this region is part of Complex C which has an extragalactic origin and is located between 4-10 kpc (Blitz et al 1999). The GALEX fields in the direction of HVC are over plotted in Figure HVC-FOV.

In Figure HVC-NUV, the GALEX FOV of the target SIRTFFL_00 (left), corresponding NUV bkgd image (center) and the profile cut (right) of the NUV image along the line shown in the HVC map are plotted. In Fig.HVC-FUV, FUV bkgd image of the region and corresponding profile cut through the line are shown. Since the local background HI (LVC) is not varying much in the field (see Fig.NHI), the HVC is clearly visible in the NUV background image but not clearly visible in the FUV image which might be due to the contamination of H2 emission from the molecular part which is not correlating with the N(HI) in the region.

Fig.7a. SF vs. FUV TEC_MIN.

Fig.7b. SF vs. NUV TEC_MIN.

[edit] UV Radiation from the Ridge

We extracted the amount of UV & IR emissions from the dust ridge by subtracting the actual background associated with the local ISM (corresponds to an N(HI) of 2.0 x 10²⁰ /cm²) around the ridge (Fig. 13) - which is calculated approximately as 363 PU in FUV, 408 PU in NUV & 1.14 MJy/sr in IR 100 micron - and is plotted in Fig. 11c. This shows that an excess emission of ~ 100 to 600 photon units in FUV, upto 200 photon units in NUV & a maximum of 1 MJy/sr in 100 micron are from the dust ridge. The N(HI) variation in the ridge is between (2.5 -- 3.2) x 10²⁰ /cm² (Lockman & Condon, 2005).

Fig.13a. Local background around the ridge from SIRTFFL_10.

Fig.13b. Local background around the ridge from SIRTFFL_03.

[edit] Dust Ridge Modeling

Assuming the ridge emission as the dust scattered radiation, we tried to model it using our three parameter (a,g,d) single scattering model (Sujatha et al 2009) and hence to derive the optical parameters of dust grains and the ridge distance. This model make use of stellar details from the Hipparcos catalog to predict the radiation field at the location dust from which the dust scattered light originates.

[edit] Dust Distribution

Considering all these points we have varied the distance of the HI sheet (dust ridge) from 50 pc to 90 pc in our model. The results from the chi-square analysis between the observed component and the model outputs for the dust ridge are tabulated below. On the basis of minimum chisq value obtained, we can reach the following conclusions:

1. The chi-sq minimum in FUV (χ²_min = 2.47) & NUV (χ²_min = 0.57) shows that the distance of the dust ridge is at 70 pc
2. Optical constants of the dust grains in the ridge corresponding to the chi-sq minimum are:
   1. FUV: a=0.3 & g=0.4
   2. NUV: a=0.2 & g=0.6

The 95% confidence limits of the parameters in the FUV and NUV bands are:

1. FUV: albedo => 0.3 -- 0.4; g => 0.3 -- 0.7
2. NUV: albedo => 0.2 -- 0.4; g => 0.3 -- 0.8
3. HI sheet Distance from FUV & NUV data => d(60 -- 90 pc)

Fig.10b. IR 100 vs FUV/NUV Ratio for the observations 0,2,5,6,7.

Fig.10c. IR 100 vs FUV/NUV Ratio for the observations 1,3,4,8,9,10.

[edit] Visits to be checked