Galaxy and Mass Assembly (GAMA): merging galaxies and their properties

We derive the close pair fractions and volume merger rates for galaxies in the Galaxy and Mass Assembly (GAMA) survey with −23 < Mr < −17 (ΩM = 0.27, ΩΛ = 0.73, H0 = 100 km s−1 Mpc−1) at 0.01 < z < 0.22 (look-back time of <2 Gyr). The merger fraction is approximately 1.5 per cent Gyr−1 at all luminosities (assuming 50 per cent of pairs merge) and the volume merger rate is ≈3.5 × 10−4 Mpc−3 Gyr−1. We examine how the merger rate varies by luminosity and morphology. Dry mergers (between red/spheroidal galaxies) are found to be uncommon and to decrease with decreasing luminosity. Fainter mergers are wet, between blue/discy galaxies. Damp mergers (one of each type) follow the average of dry and wet mergers. In the brighter luminosity bin (−23 < Mr < −20), the merger rate evolution is flat, irrespective of colour or morphology, out to z ∼ 0.2. The makeup of the merging population does not appear to change over this redshift range. Galaxy growth by major mergers appears comparatively unimportant and dry mergers are unlikely to be significant in the buildup of the red sequence over the past 2 Gyr. We compare the colour, morphology, environmental density and degree of activity (BPT class, Baldwin, Phillips & Terlevich) of galaxies in pairs to those of more isolated objects in the same volume. Galaxies in close pairs tend to be both redder and slightly more spheroid dominated than the comparison sample. We suggest that this may be due to ‘harassment’ in multiple previous passes prior to the current close interaction. Galaxy pairs do not appear to prefer significantly denser environments. There is no evidence of an enhancement in the AGN fraction in pairs, compared to other galaxies in the same volume

The Origin of Neutral Hydrogen Clouds in Nearby Galaxy Groups: Exploring the Range Of Galaxy Interactions

We combine high resolution N-body simulations with deep observations of neutral hydrogen (HI) in nearby galaxy groups in order to explore two well-known theories of HI cloud formation: HI stripping by galaxy interactions and dark matter minihalos with embedded HI gas. This paper presents new data from three galaxy groups, Canes Venatici I, NGC 672, and NGC 45, and assembles data from our previous galaxy group campaign to generate a rich HI cloud archive to compare to our simulated data. We find no HI clouds in the Canes Venatici I, NGC 672, or NGC 45 galaxy groups. We conclude that HI clouds in our detection space are most likely to be generated through recent, strong galaxy interactions. We find no evidence of HI clouds associated with dark matter halos above M_HI = 10^6 M_Sun, within +/- 700 km/s of galaxies, and within 50 kpc projected distance of galaxies.Comment: 35 pages, 10 figures, AJ accepte

Precision Cosmology: Successes and Challenges

After briefly reviewing the good agreement between large-scale observations and the predictions of the now-standard CDM theory and problems with the MOND alternative, I summarize several of the main areas of possible disagreement between theory and observation: galaxy centers, dark matter substructure, angular momentum, and the sequence of cosmogony, updating earlier reviews [1]. All of these issues are sufficiently complicated that it is not yet clear how serious they are, but there is at least some reason to think that the problems will be resolved through a deeper understanding of the complicated "gastrophysics" of star formation and feedback from supernovae and AGN.Comment: 5 pages, 1 figure, to appear in proceedings of 7th UCLA Symposium on sources and detection of dark matter and dark energy in the universe, 22-24 Feb 2006, Marina de Rey, Californi

The dynamics of mutation rate, aging and extrinsic risk in melanoma development

The gradual accumulation of intrinsic mutations linked to cell division, and the mutational imprints caused by extrinsic or environmental factors on the genome, afford the opportunity to examine the relationship between intrinsic and extrinsic risk in cancer subtypes with varying lifetime incidences. The incidence of the distinct molecular subtypes of cutaneous melanoma varies depending on anatomical site, intensity and pattern of ultraviolet (UV) light exposure, and age. Cutaneous melanoma has been subdivided into four groups, with tumor groups defined by driver mutations in either BRAF, NRAS, or NF1; with the final group defined by the absence of mutations in these genes (triple wild-type).Here we analyze the relative contributions of intrinsic risk, measured by characteristic age-related (clock-like) mutations, and extrinsic risk, measured by canonical UV light-induced signatures, to tumor development in melanoma subtypes. We show that the contributions of intrinsic and extrinsic mutations differ in magnitude and chronology during the molecular evolution of the distinct disease subtypes. We observe a gradual decline in intrinsic cell division rates as patients’ age. Our analysis of UV light-driven mutations reveals that gradual UV damage drives non-BRAF melanomas, and punctuated UV damage is linked to BRAF melanomagenesis. These data suggest that mutations accumulate at different rates in the disease subtypes, independently of germline melanoma susceptibility, from cells of origin with distinct proliferation rates. Based on our results we propose that models examining the relative roles of extrinsic and intrinsic risk in cancer consider subtype-specific lifetime risks, germline susceptibility and somatic mutational processes. <br/

Tidal Dwarf Galaxies at Intermediate Redshifts

We present the first attempt at measuring the production rate of tidal dwarf galaxies (TDGs) and estimating their contribution to the overall dwarf population. Using HST/ACS deep imaging data from GOODS and GEMS surveys in conjunction with photometric redshifts from COMBO-17 survey, we performed a morphological analysis for a sample of merging/interacting galaxies in the Extended Chandra Deep Field South and identified tidal dwarf candidates in the rest-frame optical bands. We estimated a production rate about 1.4 {\times} 10^{-5} per Gyr per comoving volume for long-lived TDGs with stellar mass 3 {\times} 10^{8-9} solar mass at 0.5<z<1.1. Together with galaxy merger rates and TDG survival rate from the literature, our results suggest that only a marginal fraction (less than 10%) of dwarf galaxies in the local universe could be tidally-originated. TDGs in our sample are on average bluer than their host galaxies in the optical. Stellar population modelling of optical to near-infrared spectral energy distributions (SEDs) for two TDGs favors a burst component with age 400/200 Myr and stellar mass 40%/26% of the total, indicating that a young stellar population newly formed in TDGs. This is consistent with the episodic star formation histories found for nearby TDGs.Comment: 9 pages, 5 figures, Accepted for publication in Astrophysics & Space Scienc

LSST Science Book, Version 2.0

A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of the exciting science opportunities of the next decade. The Large Synoptic Survey Telescope (LSST) will have an effective aperture of 6.7 meters and an imaging camera with field of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over 20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a total point-source depth of r~27.5. The LSST Science Book describes the basic parameters of the LSST hardware, software, and observing plans. The book discusses educational and outreach opportunities, then goes on to describe a broad range of science that LSST will revolutionize: mapping the inner and outer Solar System, stellar populations in the Milky Way and nearby galaxies, the structure of the Milky Way disk and halo and other objects in the Local Volume, transient and variable objects both at low and high redshift, and the properties of normal and active galaxies at low and high redshift. It then turns to far-field cosmological topics, exploring properties of supernovae to z~1, strong and weak lensing, the large-scale distribution of galaxies and baryon oscillations, and how these different probes may be combined to constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at http://www.lsst.org/lsst/sciboo

Fischer carbene complexes of cobalt(I) : Synthesis and structure

AbstractThree different aryl substrates thiophene (ThH), ferrocene (FcH) and p-bromodimethylaniline (p-DMABr) were lithiated and reacted with [Co(CO)₄SnPh₃], according to the Fischer carbene protocol. The products [CoSnPh₃(CO)₃{C(OEt)R}] (R =Th, 1, p-DMA, 2 and R = Fc, 3) were analysed to unravel the role of the aryl carbene substituent in stabilizing intermediates and final products. The ethoxy carbene complexes were aminolysed by in situ generated HNMe₂ to afford [CoSnPh₃(CO)₃{C(NMe₂)R}] (R =Th, 4, p-DMA, 5) and with N,N-dimethylethylenediamine [CoSnPh₃(CO)₃{C(NHCH₂CH₂NMe₂)R}] (R = p-DMA, 6) in high yields. The trigonal Co(CO)₃ in the equatorial plane is very stable and efforts to displace a carbonyl in 6 was unsuccessful, both by heating and irradiation. The role of the aryl carbene substituents in stabilizing the electrophilic carbene carbon was investigated and studied by NMR spectroscopy in solution and single crystal X-ray structure determinations.Abstract Three different aryl substrates thiophene (ThH), ferrocene (FcH) and p-bromodimethylaniline (p-DMABr) were lithiated and reacted with [Co(CO)₄SnPh₃], according to the Fischer carbene protocol. The products [CoSnPh₃(CO)₃{C(OEt)R}] (R =Th, 1, p-DMA, 2 and R = Fc, 3) were analysed to unravel the role of the aryl carbene substituent in stabilizing intermediates and final products. The ethoxy carbene complexes were aminolysed by in situ generated HNMe₂ to afford [CoSnPh₃(CO)₃{C(NMe₂)R}] (R =Th, 4, p-DMA, 5) and with N,N-dimethylethylenediamine [CoSnPh₃(CO)₃{C(NHCH₂CH₂NMe₂)R}] (R = p-DMA, 6) in high yields. The trigonal Co(CO)₃ in the equatorial plane is very stable and efforts to displace a carbonyl in 6 was unsuccessful, both by heating and irradiation. The role of the aryl carbene substituents in stabilizing the electrophilic carbene carbon was investigated and studied by NMR spectroscopy in solution and single crystal X-ray structure determinations

A landscape view of emerging sustainability responses within VET

With evidence of global climate change and ongoing ecological degradation, there is an urgent need to give more attention to sustainability within VET to ensure that VET does not remain complicit in reproducing the unjust and unsustainable trajectories of current economic and development pathways. At present, the VET literature does not adequately address these issues, hence the need for this special issue. In response, this paper offers a meta-reflective ‘landscape view’ of the sustainability within the VET ‘field of knowledge’ as it is emerging. Here, we use landscape review as a multi-dimensional, ‘outside-in’ view that provides a basis for understanding the broad context and helps to inform actionable next steps. This analysis we believe helps to highlight the key emerging priorities as well as what paths VET is taking on the journey to sustainability. The analysis shows that while some progress has been made in policy and practice related to the ‘greening’ of VET, much of the current response within VET to the environmental challenge reflects a minimalist reformist approach, characterised by ‘bolt-ons’ to existing institutional structures and curricula whilst leaving the fundamental beliefs in productivism, industrialisation and growth in place. Yet, as argued by researchers working on green economy, these beliefs are often complicit in co-creation of the environmental crisis

Reframing skills ecosystems for sustainable and just futures

The current dominant approach to vocational education and training (VET) does not work in theory, policy or practice in current contexts of unsustainability and global inequality. Nor is it fit for future purpose. Drawing on a large-scale research collaboration between four universities, funded by the UK’s Global Challenges Research Fund, with co-funding and funding in-kind from global south partners, this paper is a contribution to imagining new VET futures. It looks iteratively, reflexively and expansively at how our experience of VET system development involving boundary crossing between formal and informal VET systems interfaces with recent Northern work on the conceptualisation of social skills ecosystems, and how this concept can be expanded to address the challenge of skills for just transitions in the global South. We advance the skills ecosystems approach ontologically by drawing on critical realism (a growing trend in VET and development research). This allows us both to move beyond the structure-agency divide that has bedeviled the field, and with it the tendency to monoscalar analysis. Rather, we argue that accounts of VET and development must address both structure and agency, and their interplay, and must be multiscalar. This reading allows us to focus on the central importance of relationality. We argue that it is through networks and relationships that the precarious worlds of learning and work are brought together