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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.

We present the results from adaptive optics (AO) assisted imaging in the Ksband of an area of $15\ \textrm{arcmin}^2$for SWAN (Survey of a Wide Area with NACO). We derive the high resolution near-IR morphology of ∼400 galaxies up to $K_{\rm s} \sim 23.5$in the first 21 SWAN fields around bright guide stars, carefully taking into account the survey selection effects and using an accurate treatment of the anisoplanatic AO PSF. The detected galaxies are sorted into two morphological classes according to their Sérsic index. The extracted morphological properties and number counts of the galaxies are compared with the predictions of different galaxy formation and evolution models, both for the whole galaxy population and separately for late-type and early-type galaxies. This is one of the first times such a comparison has been done in the near-IR, as AO observations and accurate PSF modeling are needed to obtain reliable morphological classification of faint field galaxies at these wavelengths. For early-type galaxies we find that a pure luminosity evolution model, without evidence for relevant number and size evolution, better reproduces the observed properties of our Ks-selected sample than current semi-analytic models based on the hierarchical picture of galaxy formation. In particular, we find that the observed flattening of elliptical galaxy counts at $K_{\rm s}\sim20$is quantitatively in good agreement with the prediction of the pure luminosity evolution model that was calculated prior to the observation. For late-type galaxies, while both models are able to reproduce the number counts, we find some hints of a possible size growth. These results demonstrate the unique power of AO observations to derive high resolution details of faint galaxies' morphology in the near-IR and drive studies of galaxy evolution.

Laser guide stars with adaptive optics allow astronomical image correction in the absence of a natural guide star. Single guide star systems with a star created in the earth's sodium layer can be used to correct the wavefront in the near infrared spectral regime for 8-m class telescopes. For possible future telescopes of larger sizes, or for correction at shorter wavelengths, the use of a single guide star is ultimately limited by focal anisoplanatism that arises from the finite height of the guide star. To overcome this limitation we propose to overlap coherently pulsed laser beams that are expanded over the full aperture of the telescope, traveling upwards along the same path which light from the astronomical object travels downwards. Imaging the scattered light from the resultant interference pattern with a camera gated to a certain height above the telescope, and using phase shifting interferometry we have found a method to retrieve the local wavefront gradients. By sensing the backscattered light from two different heights, one can fully remove the cone effect, which can otherwise be a serious handicap to the use of laser guide stars at shorter wavelengths or on larger telescopes. Using two laser beams multiconjugate correction is possible, resulting in larger corrected fields. With a proper choice of laser, wavefront correction could be expanded to the visible regime and, due to the lack of a cone effect, the method is applicable to any size of telescope. Finally the position of the laser spot could be imaged from the side of the main telescope against a bright background star to retrieve tip-tilt information, which would greatly improve the sky coverage of the system.

In this paper we present the approach we have used to determine and account for the anisoplanatic point spread function (PSF) in deep adaptive optics (AO) images for the Survey of a Wide Area with NACO (SWAN) at the ESO VLT. The survey comprises adaptive optics observations in the Ksband totaling ~$30~{\rm arcmin}^2$, assembled from 42 discrete fields centered on different bright stars suitable for AO guiding. We develop a parametric model of the PSF variations across the field of view in order to build an accurate model PSF for every galaxy detected in each of the fields. We show that this approach is particularly convenient, as it uses only easily available data and makes no uncertain assumptions about the stability of the isoplanatic angle during any given night. The model was tested using simulated galaxy profiles to check its performance in terms of recovering the correct morphological parameters; we find that the results are reliable up to $K_{\rm s} \sim 20.5$($K_{{\rm AB}}\sim22.3$) in a typical SWAN field. Finally, the model obtained was used to derive the first results from five SWAN fields, and to obtain the AO morphology of 55 galaxies brighter than $K_{\rm s} = 20$. These preliminary results demonstrate the unique power of AO observations to derive the details of faint galaxy morphologies and to study galaxy evolution.

We have developed and tested a novel method, based on LIDAR, of measuring the height and profile of the mesospheric sodium layer using a continuous wave laser. It is more efficient than classical LIDAR as the laser is on for 50% of the time, and so can in principle be used during laser guide star adaptive optics observations. It also has significant advantages over direct imaging techniques because it does not require a second telescope, is almost independent of the atmospheric conditions, and avoids triangulation problems in determining the height. In the long term, regular monitoring using this method would allow a valuable database of sodium layer profiles, heights, and return flux measurements to be built up which would enable observatory staff astronomers to schedule observations optimally. In this paper we describe the original experiment carried out using the ALFA laser guide star system at Calar Alto Observatory in Spain. We validate the method by comparing the LIDAR results with those obtained from simultaneous imaging from an auxiliary telescope. Models are presented of a similar system to be implemented in the Very Large TelescopeLaser Guide Star Facility, which will enable the initial focus setting for the adaptive optics systems to be determined with an accuracy of less than 200 m on a timescale of 1 min.

Adaptive optics with laser guide stars is mandatory in order to make use of the full capabilities of 8-m class telescopes. However, progress has been slow in two particular areas: techniques for spectroscopy at diffraction limited resolution and wavefront sensing on laser guide stars. ALFA – currently the only European laser guide star adaptive optics system, and the only one in the world open to guest observers – has made significant advances in both of these. In this paper we report on our first results from summer 1998, representing significant improvements over previous performance. We report on observations using natural guide stars which demonstrate that for bright stars (${m_V}\lesssim 8$) ALFA can now reach K-band Strehl ratios in excess of 60% and easily resolve binaries at the diffraction limit of the telescope. We then present some of the first integral field spectroscopy at diffraction limited scales, showing we are able to distinguish spectra of binary stars with a separation of only 0.26″. We also discuss results from a wide field image, which indicate that useful correction (allowing binary stars and circumstellar dust shells to be resolved) can be achieved from a relatively faint star to a radius of at least 1′. Our last set of results include a correction on a galaxy using the laser guide staras the reference. The best result to date is of the galaxy UGC 1347 in Abell 262. Correcting tip-tilt on a star 41″ away and higher orders on the laser, we achieved an increase in peak intensity of 2.5, and a reduction in FWHM from 1.07″ to 0.40″.

In order to better characterise the usefulness of PAH emission as a tracer of star formation, we have undertaken a programme of 3 $\mu$m narrowband imaging of a sample of nearby template galaxies covering a wide range of metallicity, star formation activity, and nuclear activity. In the present paper we present first results of this programme: high spatial resolution images of PAH feature emission and the adjacent continuum emission from the central regions of the nearby starburst galaxies NGC 253 and NGC 1808, taken with ISAAC at the VLT-UT1. Globally, the feature emission is seen to peak on the central starburst regions of both sources. On smaller scales, however, we see no general spatial correlation or anti-correlation between the PAH feature emission and the location of sites of recent star formation, suggesting that the degree to which PAH feature emission traces starburst activity is more complicated than previously hypothesized based on results from data with lower spatial resolution. We do find spatial correlations, though, when we consider the feature-to-continuum ratio, which is low at the positions of known super star clusters in NGC 1808 as well as at the position of the IR peak in NGC 253. We take this to imply a decrease in the efficiency of PAH emission induced by the star formation, caused either by mechanical energy input into the ISM, photoionisation of the PAH molecules, or photodissociation of the PAH molecules. All three hypotheses are discussed. In addition, for the first time we present observations of PAH feature emission in the superwind of a starbursting system (NGC 253), providing strong support that winds are heavily mass-loaded and entrain substantial amounts of ambient ISM. We have also found a plausible connection between observed NaD absorption, H$_2$, and PAHs above the plane of NGC 253. This observation has important implications for enriching galaxy halos and possibly the intergalactic medium with small dust grains.

Electron probe microanalysis has been used to follow the distribution of phosphorus and associated elements within soil features to establish the composition of the immediate root environment. Various qualitative analytical modes of using the instrument are described involving either specimen traverse or spectrometer scanning with a static beam, line scanning, one‐dimensional scanning, area scanning, or successive rast counting. By these means phosphorus has been found to occur variously as discrete grains of rare‐earth phosphates, in preferential association with iron in iron/manganese concretions, as concentrations within undifferentiated soil matrix and ferrans at void surfaces, and to be associated with calcium in a fresh root and possibly with iron rather than calcium, aluminium, or potassium in an old root.

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.

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.

One of the key science goals for a diffraction limited imager on an extremely large telescope (ELT) is the resolution and accurate photometry of individual stars down to faint magnitudes in a range of environments. The aim of this study is to test the proposed capabilities of a multi-conjugate adaptive optics (MCAO) assisted imager working at the diffraction limit, in IJHKsfilters, on a 42 m diameter ELT to carry out accurate stellar photometry in crowded images in an elliptical-like galaxy at the distance of the Virgo cluster. As a basis for realistic simulations we have used the phase A studies of the European-ELT project, including the MICADO imager and the MAORY MCAO module. We convolved a complex resolved stellar population with the telescope and instrument performance expectations to create realistic images. We then tested the ability of the currently available photometric packages STARFINDER and DAOPHOT to handle these simulated images. Our results show that for a one hour exposure deep colour–magnitude diagrams (photometric error,  ± 0.25 at I≥ 27.2; H≥ 25. and Ks≥ 24.6) of old stellar populations in galaxies, at the distance of Virgo, are feasible at a maximum surface brightness, μV~ 17 mag/arcsec2(down to MI>  −4 and MH~ MK>  −6), and significantly deeper (photometric error,  ± 0.25 at I≥ 29.3; H≥ 26.6 and Ks≥ 26.2) for μV~  21 mag/arcsec2(down to MI≥  −2 and MH~ MK≥  −4.5). The photometric errors, and thus also the depth of the photometry could potentially be improved with photometry packages specifically designed for an ELT MCAO point spread function. We also make a simple comparison between these simulations and what can be expected from a single conjugate adaptive optics feed to MICADO and also the NIRCAM imager on the James Webb space telescope.

We present spatially resolved integral field spectroscopic K-band data at a resolution of 0.13″ (60 pc) and interferometric CO(2–1) line observations of the prototypical merging system NGC 6240. Despite the clear rotational signature, the stellar kinematics in the two nuclei are dominated by dispersion. We use Jeans modelling to derive the masses and the mass-to-light ratios of the nuclei. Combining the luminosities with the spatially resolved Brγequivalent width shows that only 1/3 of the K-band continuum from the nuclei is associated with the most recent star forming episode; and that less than 30% of the system’s bolometric luminosity and only 9% of its stellar mass is due to this starburst. The star formation properties, calculated from typical merger star formation histories, demonstrate the impact of different assumptions about the star formation history. The properties of the nuclei, and the existence of a prominent old stellar population, indicate that the nuclei are remnants of the progenitor galaxies’ bulges.

Aims. NGC 2992 is an intermediate Seyfert 1 galaxy showing outflows on kilo parsec scales which might be due either to AGN or starburst activity. We therefore aim at investigating its central region for a putative starburst in the past and its connection to the AGN and the outflows.Methods. Observations were performed with the adaptive optics near infrared integral field spectrograph SINFONI on the VLT, complemented by longslit observations with ISAAC on the VLT, as well as N- and Q-band data from the Spitzer archive. The spatial and spectral resolutions of the SINFONI data are 50 pc and 83 km s-1, respectively. The field of view of $3\arcsec$× $3\arcsec$corresponds to 450 pc × 450 pc. Brγequivalent width and line fluxes from PAHs were compared to stellar population models to constrain the age of the putative recent star formation. A simple geometric model of two mutually inclined disks and an additional cone to describe an outflow was developed to explain the observed complex velocity field in H21–0S(1).Results. The morphologies of the Brγand the stellar continuum are different suggesting that at least part of the Brγemission comes from the AGN. This is confirmed by PAH emission lines at 6.2 μm and 11.2 μm and the strength of the silicon absorption feature at 9.7 μm, which point to dominant AGN activity with a relatively minor starburst contribution. We find a starburst age of 40–50 Myr from Brγline diagnostics and the radio continuum; ongoing star formation can be excluded. Both the energetics and the timescales indicate that the outflows are driven by the AGN rather than the starburst. The complex velocity field observed in H21–0S(1) in the central 450 pc can be explained by the superposition of the galaxy rotation and an outflow.

Aims. NGC 2992 is an intermediate Seyfert 1 galaxy showing outflows on kilo parsec scales which might be due either to AGN or starburst activity. We therefore aim at investigating its central region for a putative starburst in the past and its connection to the AGN and the outflows.