MAGNETIC-FIELD VERSUS GAS-DENSITY, IN DIFFERENT PHYSICAL CONDITIONS

A search is made here for possible variations in the behavior of magne tic field values B at various gas density values n, when comparing low density gas versus high density gas, and when comparing compressed ga s versus quiescent gas. (a) For the quiescent microturbulent interstel lar gas (e.g., clouds, interclumps - see Table I), the statistical rel ation B similar to n(k) yields k = 0.46 +/- 0.07 for high gas density n > 100 cm(-3), and k = 0.17 +/- 0.03 for low gas density n < 100 cm(- 3) (see Figure 1). (b) For the compressed macroturbulent interstellar gas (e.g., masers, expanding shells - see Table II), the statistical r elation B similar to n(K) yields K = 0.61 +/- 0.09 for high gas densit y n > 100 cm(-3) and K = 0.37 +/- 0.2 for low gas density n < 100 cm(- 3) (see Figure 2). (c) The separation between low density gas and high density gas is statistically significant. The 2 different physical be haviors (below and above the break at 100 cm(-3)) are confirmed statis tically (about 2 to 4 sigma away for the quiescent gas alone; about 3 to 6 sigma away for the combined quiescent plus compressed gas). (d) T he separation between compressed gas and quiescent gas is not statisti cally significant now (see Figure 3). At n > 100 cm(-3), a comparison of quiescent gas versus compressed gas shows no statistically signific ant differences in behavior (they are only about 1 sigma away). At n < 100 cm(-3) a comparison of quiescent versus compressed gas also shows no statistically significant differences in behavior (less than 1 sig ma away). (e) A relation between the density n and the galactic-wide S tar Formation Rate (SFR) can be made for galactic magnetic fields, i.e .: (SFR) similar to n(k/j). For galactic-wide parameters using quiesce nt, low density n < 100 cm(-3), and the known relationships B similar to n(k) with k = 0.17, B similar to (SFR)(j) with j = 0.13, then one g ets here a law SFR similar to n(k/j) with an exponent k/j = 1.3. This is in rough accord with known data for the Milky Way and for NGC6946.