Search

Theoretical models and numerical simulations have established a framework of galaxy evolution in which galaxies merge and create dual supermassive black holes (with separations of one to ten kiloparsecs), which eventually sink into the centre of the merger remnant, emit gravitational waves and coalesce. The merger also triggers star formation and supermassive black hole growth, and gas outflows regulate the stellar content1–3. Although this theoretical picture is supported by recent observations of starburst-driven and supermassive black hole-driven outflows4–6, it remains unclear how these outflows interact with the interstellar medium. Furthermore, the relative contributions of star formation and black hole activity to galactic feedback remain unknown7–9. Here we report observations of dual outflows in the central region of the prototypical merger NGC 6240. We find a black-hole-driven outflow of [O iii] to the northeast and a starburst-driven outflow of Hα to the northwest. The orientations and positions of the outflows allow us to isolate them spatially and study their properties independently. We estimate mass outflow rates of 10 and 75 solar masses per year for the Hα bubble and the [O iii] cone, respectively. Their combined mass outflow is comparable to the star formation rate10, suggesting that negative feedback on star formation is occurring.

A STUDY of the distribution of trace elements in rocks, soils and plants in Snowdonia1, to be reported in detail elsewhere, has led to a realization of the relative importance of material borne in the atmosphere as a source for the trace elements in certain organic accumulations. Relevant analytical data are provided from two sources—first, from an investigation into the role of saxicolous lichens in the initial stages of pedogenesis and, second, from a routine survey of the trace element status of mountain topsoils.

A DEFINITIVE and important characteristic of soil is its heterogeneity in fabric. This is evident in the great variety of spatial arrangements of components that have been established by the microscopic study of soil in thin section1. Chemical methods of soil analysis, however, usually involve the homogenization of soil material and therefore the destruction of its fabric by drying, sieving and representative sampling. Microchemical and mineralogical analysis of undisturbed soil fabric, on a scale comparable with the smallest recognizable components (that is, at least at the micron level), is therefore desirable to complement the existing chemical approach.

DURING the course of some investigations of seasonal variations in the available cation content of soils in Denbighshire (North Wales), samples of the soil solution were needed. The soils are classed as loams and silty loams, and moisture contents ranged from 30 to 47 per cent.