All Tables

Table 1: Overview of the observed LMC targets. The targets Sk -67 5 and Sk -70 120 are comparison stars used for telluric correction and stellar line identification. Adopted $\ensuremath {E_{B-V}}$ values are corrected for Galactic foreground extinction (see Table 3). The final magnitudes and colour indices are on the photometric system defined by Landolt (1992). The ${\it UBV}$ optical photometry for the remainder of the LMC stars was taken from Misselt et al. (1999) and Gordon et al. (2003).
Table 2: Diffuse interstellar bands investigated in this study. Equivalent widths ( EW) and associated statistical errors $\sigma _{\it EW}$ are quoted in mÅ. For non-detected DIBs upper limits are given; EW $_{\rm upper\ limit} = 3 \times \sigma _{\rm continuum} \times {\it FWHM}_{\rm DIB}$ , with $\sigma _{\rm continuum}$ the noise on the adjacent continuum, and FWHM $_{\rm DIB}$ the expected full width at half maximum of the respective DIB. The $\ensuremath {E_{B-V}}$ values were derived by subtracting the Milky Way foreground contamination from the line of sight reddening (see Sect. 4.1 and Tables 1 and 3). The " $\times$ '' signifies DIBs that were not covered by the spectral setting, and the (B) indicates possible blending with stellar or instrumental features. We have derived upper limits for DIB strengths towards the low reddened target Sk -67 5. Sk -70 120 has been used as the reference star ( $\ensuremath {E_{B-V}}$ = 0.0 mag).
Table 3: Colour and extinction characteristics for the LMC lines of sight. The B and V photometric data were combined with intrinsic colours for LMC supergiants (Fitzpatrick 1988) to obtain the total $\ensuremath {E_{B-V}}$ for the line of sight towards the LMC targets. To derive the reddening within the LMC ( $\ensuremath {E_{B-V}}$ $_{\rm , LMC}$ ) the combined foreground contribution of both the Milky Way (MW) and intermediate velocity clouds (VC) were subtracted. All values are in magnitudes. Fitzpatrick & Savage (1984) derive $\ensuremath {E_{B-V}}$ $_{\rm , total} = 0.34$ mag, and $\ensuremath {E_{B-V}}$ $_{\rm , LMC} = 0.27$ mag for Sk -69 243, consistent with the value derived below. Smith et al. (1990) derive $\ensuremath {E_{B-V}}$ $_{\rm , total} = 0.39$ and 0.41 mag for Sk -69 223 and Sk -69 243, respectively.
Table 4: $R{_{\rm V}}$ values derived from optical and infrared photometry based on three different methods. The one but last column lists previously reported values for $R{_{\rm V}}$ . In Col. 2 we list the comparison stars (or spectral type) adopted to compute $R{_{\rm V}}$ for the targets in Col. 1 as discussed in the main text. Together with the reddening (Col. 3) three methods were used to derive $R{_{\rm V}}$ (Cols. 5-7). The average $R{_{\rm V}}$ is given in Col. 8, and a literature value is given in Col. 9 when available. The last Col. 10 gives the spectral type of the adopted comparison target or the foreground reddening based on the Galactic extinction curve ( $R_{\rm V} = 3.1$ ) that is subtracted from the constructed "total'' extinction curve.
Table 5: Total column density of Na I, K I, Ca II, Ti II and H I (for the Milky Way (MW), intervening high velocity clouds (VC) and Large Magellanic Cloud (LMC) components) derived from fitting the profiles with the splot task in IRAF. The column density of the individual components of the interstellar atomic line profile (as shown in Figs. 4 and 6) is given in Tables 11 to 15 (on-line only). For Sk -67 2 and Sk -68 135 the Na I D doublet is saturated and we used the Na I UV line at 3302 Å instead. The error in column density log N is about 0.02 to 0.05 dex for K I, Ca II, Ti II and about 0.03 and 0.08 dex for Na I D and Na I (UV), respectively. The apparent optical depth method picks up more unresolved structure and therefore gives slightly higher values of N than other methods (like Gaussian profile fitting). Nevertheless, the obtained column densities for Ca II and Na I (from 3302.6 Å line) agree well, within the error bars, with preliminary results obtained by Welty (private communication) for the targets Sk -69 243, Sk -68 135 and Sk -67 5.
Table 6: Atomic column density line ratios, titanium depletion level and electron densities for the LMC sightlines. Column density ratios are calculated for the total integrated LMC profiles (from 200 to 300 km s^-1). n_e is computed via Eq. (1) in Sect. 5.3, and for the titanium depletion (log $\delta _{\rm Ti}$ ) a logarithmic Ti II metallicity of 0.3 dex less than the solar abundance is assumed.
Table 7: Total-to-selective visual extinction $R{_{\rm V}}$ , visual extinction $A_{\rm V}$ and atomic gas-to-dust ratio N(H I)/ $A_{\rm V}$ for the four reddened LMC lines of sight.
Table 8: Physical properties and conditions of the interstellar medium in the lines of sight towards the LMC target Sk -69 223 (Tables 2, 5-7) and the Galactic targets HD 144217 ( $\sigma$ -type) and HD 149757 ( $\zeta$ -type).
Table 9: Optical and infrared photometry ( ${\it UBVJHK}$ ). Values for ${\it JHK}$ are from the 2MASS Point Source Catalogue (Cutri et al. 2003). The invariance of the infrared part of the extinction curve is utilised to compute $R{_{\rm V}}$ (Sect. 4.2). For all adopted methods we need colour excesses which can be derived using intrinsic colours for the corresponding spectral type, or by finding a spectral type match between the reddened and comparison target. Errors are 0.02, 0.02, and 0.04 for V, B-V, and U-B, respectively.
Table 10: Local standard of rest (LSR) velocity v (km s^-1), column density N (cm^-2) and Gaussian width g (km s^-1) for the atomic species Na I D, Ca II, Ti II, K I and H I observed toward Sk -69 223. * = not optical depth corrected due to erroneous data. The bottom two lines give the total LMC column densities for the respective atoms.
Table 11: Local standard of rest (LSR) velocity v (km s^-1), column density N (cm^-2) and Gaussian width g (km s^-1) for the atomic species Na I D, Ca II, Ti II, K I and H I observed toward Sk -69 243. * = Not optical depth corrected due to problematic data. The bottom two lines give the total LMC column densities for the respective atoms.
Table 12: Local standard of rest (LSR) velocity v (km s^-1), column density N (cm^-2) and Gaussian width g (km s^-1) for the atomic species Na I (D and UV), Ca II, Ti II and H I observed toward Sk -67 2. The bottom two lines give the total LMC column densities for the respective atoms.
Table 13: Local standard of rest (LSR) velocity v (km s^-1), column density N (cm^-2) and Gaussian width g (km s^-1) for the atomic species Na I (D and UV), Ca II, Ti II, K I and H I observed toward Sk -68 135. The bottom two lines give the total LMC column densities for the respective atoms.
Table 14: Local standard of rest (LSR) velocity v (km s^-1), column density N (cm^-2) and Gaussian width g (km s^-1) for the atomic species Na I D, Ca II, Ti II, K I and H I observed toward Sk -67 5. The bottom two lines give the total LMC column densities for the respective atoms.
Table 15: Local standard of rest (LSR) velocity v (km s^-1), column density N (cm^-2) and Gaussian width g (km s^-1) for the atomic species Na I D, Ca II, Ti II and H I observed toward Sk -70 120. The bottom two lines give the total LMC column densities for the respective atoms.