SummaryAccurate measurement of clonal genotypes, mutational processes, and replication states from individual tumor-cell genomes will facilitate improved understanding of tumor evolution. We have developed DLP+, a scalable single-cell whole-genome sequencing platform implemented using commodity instruments, image-based object recognition, and open source computational methods. Using DLP+, we have generated a resource of 51,926 single-cell genomes and matched cell images from diverse cell types including cell lines, xenografts, and diagnostic samples with limited material. From this resource we have defined variation in mitotic mis-segregation rates across tissue types and genotypes. Analysis of matched genomic and image measurements revealed correlations between cellular morphology and genome ploidy states. Aggregation of cells sharing copy number profiles allowed for calculation of single-nucleotide resolution clonal genotypes and inference of clonal phylogenies and avoided the limitations of bulk deconvolution. Finally, joint analysis over the above features defined clone-specific chromosomal aneuploidy in polyclonal populations.

We use Spitzer Space Telescope and Herschel Space Observatory far‐infrared data along with ground‐based optical and near‐infrared data to understand how dust heating in the nearby face‐on spiral galaxies M81, M83 and NGC 2403 is affected by the starlight from all stars and by the radiation from star‐forming regions. We find that 70/160 m surface brightness ratios tend to be more strongly influenced by star‐forming regions. However, the 250/350 m and 350/500 m surface brightness ratios are more strongly affected by the light from the total stellar populations, suggesting that the dust emission at >250 m originates predominantly from a component that is colder than the dust seen at <160 m and that is relatively unaffected by star formation activity. We conclude by discussing the implications of this for modelling the spectral energy distributions of both nearby and more distant galaxies and for using far‐infrared dust emission to trace star formation.

The evolution of present‐day fossil galaxy groups is studied in the Millennium simulation. Using the corresponding Millennium gas simulation and semi‐analytic galaxy catalogues, we select fossil groups at redshift zero according to the conventional observational criteria, and trace the haloes corresponding to these groups backwards in time, extracting the associated dark matter, gas and galaxy properties. The space density of the fossils from this study is remarkably close to the observed estimates and various possibilities for the remaining discrepancy are discussed. The fraction of X‐ray bright systems which are fossils appears to be in reasonable agreement with observations, and the simulations predict that fossil systems will be found in significant numbers (3–4 per cent of the population) even in quite rich clusters. We find that fossils assemble a higher fraction of their mass at high redshifts, compared to non‐fossil groups, with the ratio of the currently assembled halo mass to final mass, at any epoch, being about 10–20 per cent higher for fossils. This supports the paradigm whereby fossils represent undisturbed, early‐forming systems in which large galaxies have merged to form a single dominant elliptical.

We investigate the assembly of groups and clusters of galaxies using the Millennium dark matter simulation and the associated Millennium gas simulations, and semi-analytic catalogues of galaxies. In particular, in order to find an observable quantity that could be used to identify early-formed groups, we study the development of the difference in magnitude between their brightest galaxies to assess the use of magnitude gaps as possible indicators. We select galaxy groups and clusters at redshift z = 1 with dark matter halo mass M(R 200 ) ≥ 10 13 h −1 M , and trace their properties until the present time (z = 0). We consider only the systems with X-ray luminosity L X,bol ≥ 0.25 × 10 42 h −2 erg s −1 at redshift z = 0. While it is true that a large magnitude gap between the two brightest galaxies of a particular group often indicates that a large fraction of its mass was assembled at an early epoch, it is not a necessary condition. More than 90 per cent of fossil groups defined on the basis of their magnitude gaps (at any epoch between 0 < z < 1) cease to be fossils within 4 Gyr, mostly because other massive galaxies are assembled within their cores, even though most of the mass in their haloes might have been assembled at early times. We show that compared to the conventional definition of fossil galaxy groups based on the magnitude gap m 12 ≥ 2 (in the R-band, within 0.5 R 200 of the centre of the group), an alternative criterion m 14 ≥ 2.5 (within the same radius) finds 50 per cent more early-formed systems, and those that on average retain their fossil phase longer. However, the conventional criterion performs marginally better at finding earlyformed groups at the high-mass end of groups. Nevertheless, both criteria fail to identify a majority of the early-formed systems.