Electron temperature and electron density for the different regions of M2-42 are presented in Table 2. The electron temperatures and densities were obtained using the EQUIB code (Howarth & Adams, 1981) from the [NII] nebular to auroral line ratio and the [SII] doublet line ratio, respectively. The electron temperature ([NII]) was corrected for recombination contribution to the auroral line using the formula given by Liu et al. (2000) and the ionic abundance derived from the NII lines. The values of [SII]cm and [NII] K are in agreement with [SII]cm and [NII]K derived by Wang & Liu (2007). Additionally, we determined the physical conditions of the NE and SW jets. The jets show a mean electron temperature of K, which is 760K lower than that of the main shell, whereas their mean electron density of cm is by a factor of five lower than that of the main shell.
Table 2 also lists the ionic abundances X/H derived from collisionally excited lines (CELs) and optical recombination lines (ORLs). We used the EQUIB code to calculate the ionic abundances. We adopted the physical conditions, ( for the main shell) and , derived from CELs. The atomic data sets used for plasma diagnostics and abundances analysis are the same as those used by Danehkar (2014, Chapter 3).
Our value of He/H for the main shell is in good agreement with He/H = 0.107 derived by Wang & Liu (2007). However, they derived O/H = , which is twice our value. This could be due to the different atomic data used by them. Our values of N/H, S/H and Ar/H are in reasonable agreement with N/H = , S/H = and Ar/H = obtained by Wang & Liu (2007). Note that a slit with a width of used by Wang & Liu (2007) is not completely related to the main shell. We see that the abundance discrepancy factor for O, , is in agreement with (Wang & Liu, 2007). Moreover, our abundance ratio of (N/O derived from ORLs is in excellent agreement with (N/O obtained by Wang & Liu (2007). Although He/H and O/H derived from the jets are similar to those of the main shell, N/H and S/H derived from the jets are about three times higher than those of the main shell. These ionization features of the bipolar collimated jets are typical of fast, low-ionization emission regions (FLIERs; Balick et al., 1993; Balick et al., 1994; Balick et al., 1998).
|Parameter||Main Shell||NE Jet||SW Jet|