13 research outputs found
Molecular ions in L1544. II. The ionization degree
The maps presented in Paper I are here used to infer the variation of the
column densities of HCO+, DCO+, N2H+, and N2D+ as a function of distance from
the dust peak. These results are interpreted with the aid of a crude chemical
model which predicts the abundances of these species as a function of radius in
a spherically symmetric model with radial density distribution inferred from
the observations of dust emission at millimeter wavelengths and dust absorption
in the infrared. Our main observational finding is that the N(N2D+)/N(N2H+)
column density ratio is of order 0.2 towards the L1544 dust peak as compared to
N(DCO+)/N(HCO+) = 0.04. We conclude that this result as well as the general
finding that N2H+ and N2D+ correlate well with the dust is caused by CO being
depleted to a much higher degree than molecular nitrogen in the high density
core of L1544. Depletion also favors deuterium enhancement and thus N2D+, which
traces the dense and highly CO-depleted core nucleus, is much more enhanced
than DCO+. Our models do not uniquely define the chemistry in the high density
depleted nucleus of L1544 but they do suggest that the ionization degree is a
few times 10^{-9} and that the ambipolar diffusion time scale is locally
similar to the free fall time. It seems likely that the lower limit which one
obtains to ionization degree by summing all observable molecular ions is not a
great underestimate of the true ionization degree. We predict that atomic
oxygen is abundant in the dense core and, if so, H3O+ may be the main ion in
the central highly depleted region of the core.Comment: 31 pages, 8 figures, to be published in Ap
Nazi Punks Folk Off: Leisure, Nationalism, Cultural Identity and the Consumption of Metal and Folk Music
Far-right activists have attempted to infiltrate and use popular music scenes to propagate their racialised ideologies. This paper explores attempts by the far right to co-opt two particular music scenes: black metal and English folk. Discourse tracing is used to explore online debates about boundaries, belonging and exclusion in the two scenes, and to compare such online debates with ethnographic work and previous research. It is argued that both scenes have differently resisted the far right through the policing of boundaries and communicative choices, but both scenes are compromised by their relationship to myths of whiteness and the instrumentality of the pop music industry