Letters

Cole, Jane

doi:10.2307/4016964

Cited by 60 publications

(84 citation statements)

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“…The most important result shown in this paper is that galaxy formation processes, both mass assembly and star formation, take place rapidly and are completed early in massive systems, while in the Kodama & Bower (2003) and the 2MASS local cluster data (solid curve) are taken from Balogh et al (2001). The 2dF field data (open squares) are taken from Cole et al (2000). The model predictions by the Mitaka semi-analytic model (Nagashima et al 2002) are shown for z = 0 (dotted curve) and z = 1 (dashed curve).…”

Section: Down-sizing In Galaxy Formationmentioning

confidence: 90%

Down-sizing in galaxy formation atz∼ 1 in the Subaru/XMM-NewtonDeep Survey (SXDS)

Kodama

Yamada

Akiyama

et al. 2004

Monthly Notices of the Royal Astronomical Society

164

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We use the deep wide‐field optical imaging data of the Subaru/XMM–Newton Deep Survey to discuss the luminosity‐ (mass‐)dependent galaxy colours down to z′= 25.0 (5 × 109h−270 M⊙) for z∼ 1 galaxies in colour‐selected high‐density regions. We find an apparent absence of galaxies on the red colour–magnitude sequence below z′∼ 24.2, corresponding to ∼M*+ 2 (∼ 1010 M⊙) with respect to passively evolving galaxies at z∼ 1. Galaxies brighter than M*− 0.5 (8 × 1010 M⊙), however, are predominantly red passively evolving systems, with few blue star‐forming galaxies at these magnitudes. This apparent age gradient, where massive galaxies are dominated by old stellar populations while less massive galaxies have more extended star formation histories, supports the ‘down‐sizing’ idea where the mass of galaxies hosting star formation decreases as the Universe ages. Combined with the lack of evolution in the shape of the stellar mass function for massive galaxies since at least z∼ 1, it appears that galaxy formation processes (both star formation and mass assembly) should have occurred in an accelerated way in massive systems in high‐density regions, while these processes should have been slower in smaller systems. This result provides an interesting challenge for modern cold dark matter based galaxy formation theories which predict later formation epochs of massive systems, commonly referred to as ‘bottom‐up’.

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Section: Down-sizing In Galaxy Formationmentioning

confidence: 90%

Down-sizing in galaxy formation atz∼ 1 in the Subaru/XMM-NewtonDeep Survey (SXDS)

Kodama

Yamada

Akiyama

et al. 2004

Monthly Notices of the Royal Astronomical Society

164

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“…Having demonstrated that our model can be used to calculate disc heating rates with reasonable accuracy, we now proceed to apply these calculations to galaxy formation in a cosmological setting. Specifically, we implement this model of disc heating in the GAL-FORM semi-analytic model of galaxy formation described by Cole et al (2000) and Benson et al (2002a), based on a standard CDM cosmology with 0 = 0.3 and 0 = 0.7. 4 This model follows the growth of galactic discs in a merging hierarchy of dark matter haloes.…”

Section: Scaleheight Distribution For Disc Galaxiesmentioning

confidence: 99%

Heating of galactic discs by infalling satellites

Benson

Lacey

Frenk

et al. 2004

Monthly Notices of the Royal Astronomical Society

114

145

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We develop an analytic model to calculate the rate at which galaxy discs are heated by dark matter substructures orbiting in their haloes. The model takes into account the internal structure, mass function and accretion rate of satellites expected in the ΛCDM cosmology, as well as the growth of the disc by accretion and mergers, but it ignores resonant heating of the disc and the dynamical effects of spiral arms and bars. We calibrate this model against N‐body simulations and demonstrate that it is able to reproduce the N‐body heating rates to within a factor of 3 in the majority of cases. Our model gives the distribution of disc scaleheights for galaxies of different luminosities. For L* spiral galaxies, it predicts a median disc thickness of only 5 per cent of the radial scalelength if substructure is the only source of heating. The median disc thickness increases to nearly 20 per cent of the radial scalelength when heating due to gravitational scattering of stars by molecular clouds is also included. The latter value is close to the thickness estimated observationally for the disc of the Milky Way galaxy. The distribution of disc thickness predicted by the model is also consistent with a recent observational determination for sub‐L* galaxies by Bizyaev & Mitronova. Thus, the observed thickness of the stellar discs of spiral galaxies seems to be entirely compatible with the abundance of substructure in dark matter haloes predicted by the standard Λ‐dominated cold dark matter model of structure formation. In an Ω0= 1 universe, our best model of galaxy formation produces similar scaleheights, a consequence of the fact that similar amounts of substructure are accreted by haloes during the lifetime of the disc in Ω0= 1 and 0.3, Λ0= 0.7 cold dark matter cosmologies.

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“…In our simplest models, a galaxy grows through two principal mechanisms: the gradual accretion of gas, which cools and forms a thin disk of stars; and the merging of existing stellar systems, which produces a spheroid. These two structural components thus form through disparate mechanisms, contain different stellar populations, and represent disjoint periods in a galaxy's history (e.g., Cole et al 2000;Cook et al 2009;Benson 2010). Using information regarding both the spatial distributions and SEDs of these components will clearly enable a more robust separation of their properties, when compared with trying to use just one of these pieces of information alone.…”

Section: Galaxy Componentsmentioning

confidence: 99%

Measuring SEDs for individual galaxy components

et al. 2011

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Abstract. Our project, 'MegaMorph', is developing a next-generation tool for decomposing galaxies, in terms of both their structures and stellar populations. By combining data from UV to NIR wavelengths, accounting for morphological peculiarities using non-parametric components, and utilising efficient likelihood sampling methods, we are working to significantly improve the robustness and accuracy of galaxy decomposition. Applying these new techniques to modern large surveys will provide us with a deeper understanding of galaxies.Keywords. galaxies: fundamental parameters, galaxies: structure, galaxies: photometry, methods: data analysis, techniques: image processing Galaxy componentsGalaxies comprise a complex mix of stars, gas, dust and dark matter, with their proportions, distributions and kinematics resulting from a wide variety of physical processes. Even considering just the stars, galaxies typically possess distinct stellar populations, which formed at different times, under varied conditions. To gain more than a superficial understanding of the galaxy population, and the processes that shape it, we need to disentangle these physical components within individual galaxies.This conference primarily focused on separating and characterising galaxy components through their spectral energy distributions. These SEDs are usually, with a few notable exceptions, integrated over the spatial extent of each galaxy. For separating components which dominate at different wavelength ranges, e.g., stars and dust, this approach works well. However, when dividing components with only subtle differences in their SEDs, e.g., multiple stellar populations, any additional discriminatory information is valuable.The various stellar populations within a galaxy often have contrasting spatial distributions. In our simplest models, a galaxy grows through two principal mechanisms: the gradual accretion of gas, which cools and forms a thin disk of stars; and the merging of existing stellar systems, which produces a spheroid. These two structural components thus form through disparate mechanisms, contain different stellar populations, and represent disjoint periods in a galaxy's history (e.g., Cole et al. 2000;Cook et al. 2009;Benson 2010). Using information regarding both the spatial distributions and SEDs of these components will clearly enable a more robust separation of their properties, when compared with trying to use just one of these pieces of information alone. The dichotomy between disk and spheroid stellar components (e.g., Allen et al. 2006;Benson & Devereux 2010) is at the heart of our understanding of galaxy development: measuring their individual properties will provide a deeper understanding of the galaxy population and more effective comparison with theoretical models.

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Letters

Cited by 60 publications

References 0 publications

Down-sizing in galaxy formation atz∼ 1 in the Subaru/XMM-NewtonDeep Survey (SXDS)

Down-sizing in galaxy formation atz∼ 1 in the Subaru/XMM-NewtonDeep Survey (SXDS)

Heating of galactic discs by infalling satellites

Measuring SEDs for individual galaxy components

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