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  • 1
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    The ATLAS3D Project - XXIII. Angular momentum and nuclear surface brightness profiles (2013)
    Oxford University Press
    Details
    Publication Date: 2013-07-26
    Description: We investigate nuclear light profiles in 135 ATLAS 3D galaxies for which the Hubble Space Telescope ( HST ) imaging is available and compare them to the large-scale kinematics obtained with the SAURON integral-field spectrograph. Specific angular momentum, R , correlates with the shape of nuclear light profiles, where, as suggested by previous studies, cores are typically found in slow rotators and core-less galaxies are fast rotators. As also shown before, cores are found only in massive galaxies and only in systems with the stellar mass (measured via dynamical models) M   8  x 10 10 M . Based on our sample, we, however, see no evidence for a bimodal distribution of nuclear slopes. The best predictor for finding a core is based on the stellar velocity dispersion within an effective radius, e , and specific angular momentum, where cores are found for R   0.25 and e   160 km s –1 . We estimate that only about 10 per cent of nearby early-type galaxies contain cores. Furthermore, we show that there is a genuine population of fast rotators with cores. We also show that core fast rotators are morphologically, kinematically and dynamically different from core slow rotators. The cores of fast rotators, however, could harbour black holes of similar masses to those in core slow rotators, but typically more massive than those found in core-less fast rotators. Cores of both fast and slow rotators are made of old stars and found in galaxies typically lacking molecular or atomic gas (with a few exceptions). Core-less galaxies, and especially core-less fast rotators, are underluminous in the diffuse X-ray emission, but the presence of a core does not imply high X-ray luminosities. Additionally, we postulate (as many of these galaxies lack HST imaging) a possible population of core-less galaxies among slow rotators, which cannot be explained as face-on discs, but comprise a genuine sub-population of slow rotators. These galaxies are typically less massive and flatter than core slow rotators, and show evidence for dynamical cold structures and exponential photometric components. Based on our findings, major non-dissipative (gas-poor) mergers together with black hole binary evolution may not be the only path for formation of cores in early-type galaxies. We discuss possible processes for formation of cores and their subsequent preservation.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    The KMOS Redshift One Spectroscopic Survey (KROSS): the Tully-Fisher relation at z ~ 1 (2016)
    Oxford University Press
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    Publication Date: 2016-05-22
    Description: We present the stellar mass ( M * ), and K-corrected K -band absolute magnitude ( M K ) Tully–Fisher relations (TFRs) for subsamples of the 584 galaxies spatially resolved in H α emission by the KMOS Redshift One Spectroscopic Survey (KROSS). We model the velocity field of each of the KROSS galaxies and extract a rotation velocity, V 80 at a radius equal to the major axis of an ellipse containing 80 per cent of the total integrated H α flux. The large sample size of KROSS allowed us to select 210 galaxies with well-measured rotation speeds. We extract from this sample a further 56 galaxies that are rotationally supported, using the stringent criterion V 80 / 〉 3, where is the flux weighted average velocity dispersion. We find the M K and M * TFRs for this subsample to be $M_{K} / \rm {mag}= (-7.3 \pm 0.9) \times [(\log (V_{80}/\rm {km\ s^{-1}})-2.25]- 23.4 \pm 0.2$ , and $\log (M_{{\ast }} / \mathrm{M}_{{\odot }})= (4.7 \pm 0.4) \times [(\log (V_{80}/\rm {km\ s^{-1}}) - 2.25] + 10.0 \pm 0.3$ , respectively. We find an evolution of the M * TFR zero-point of –0.41 ± 0.08 dex over the last ~8 billion years. However, we measure no evolution in the M K TFR zero-point over the same period. We conclude that rotationally supported galaxies of a given dynamical mass had less stellar mass at z ~ 1 than the present day, yet emitted the same amounts of K -band light. The ability of KROSS to differentiate, using integral field spectroscopy with KMOS, between those galaxies that are rotationally supported and those that are not explains why our findings are at odds with previous studies without the same capabilities.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 3
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    The ATLAS3D project - XXII. Low-efficiency star formation in early-type galaxies: hydrodynamic models and observations (2013)
    Oxford University Press
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    Publication Date: 2013-06-09
    Description: We study the global efficiency of star formation in high-resolution hydrodynamical simulations of gas discs embedded in isolated early-type and spiral galaxies. Despite using a universal local law to form stars in the simulations, we find that the early-type galaxies are offset from the spirals on the large-scale Kennicutt relation, and form stars two to five times less efficiently. This offset is in agreement with previous results on morphological quenching: gas discs are more stable against star formation when embedded in early-type galaxies due to the lower disc self-gravity and increased shear. As a result, these gas discs do not fragment into dense clumps and do not reach as high densities as in the spiral galaxies. Even if some molecular gas is present, the fraction of very dense gas (typically above 10 4 cm –3 ) is significantly reduced, which explains the overall lower star formation efficiency. We also analyse a sample of local early-type and spiral galaxies, measuring their CO and H i surface densities and their star formation rates as determined by their non-stellar 8 μm emission. As predicted by the simulations, we find that the early-type galaxies are offset from the Kennicutt relation compared to the spirals, with a twice lower efficiency. Finally, we validate our approach by performing a direct comparison between models and observations. We run a simulation designed to mimic the stellar and gaseous properties of NGC 524, a local lenticular galaxy, and find a gas disc structure and global star formation rate in good agreement with the observations. Morphological quenching thus seems to be a robust mechanism, and is also consistent with other observations of a reduced star formation efficiency in early-type galaxies in the COLD GASS survey. This lower efficiency of star formation is not enough to explain the formation of the whole red sequence, but can contribute to the reddening of some galaxies.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 4
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    Phylogenetic and Genomic Analyses Resolve the Origin of Important Plant Genes Derived from Transposable Elements (2016)
    Oxford University Press
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    Publication Date: 2016-07-19
    Description: Once perceived as merely selfish, transposable elements (TEs) are now recognized as potent agents of adaptation. One way TEs contribute to evolution is through TE exaptation, a process whereby TEs, which persist by replicating in the genome, transform into novel host genes, which persist by conferring phenotypic benefits. Known exapted TEs (ETEs) contribute diverse and vital functions, and may facilitate punctuated equilibrium, yet little is known about this process. To better understand TE exaptation, we designed an approach to resolve the phylogenetic context and timing of exaptation events and subsequent patterns of ETE diversification. Starting with known ETEs, we search in diverse genomes for basal ETEs and closely related TEs, carefully curate the numerous candidate sequences, and infer detailed phylogenies. To distinguish TEs from ETEs, we also weigh several key genomic characteristics including repetitiveness, terminal repeats, pseudogenic features, and conserved domains. Applying this approach to the well-characterized plant ETEs MUG and FHY3 , we show that each group is paraphyletic and we argue that this pattern demonstrates that each originated in not one but multiple exaptation events. These exaptations and subsequent ETE diversification occurred throughout angiosperm evolution including the crown group expansion, the angiosperm radiation, and the primitive evolution of angiosperms. In addition, we detect evidence of several putative novel ETE families. Our findings support the hypothesis that TE exaptation generates novel genes more frequently than is currently thought, often coinciding with key periods of evolution.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 5
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    Arms-race dynamics between plants and butterflies [Evolution] (2015)
    National Academy of Sciences
    Details
    Publication Date: 2015-07-08
    Description: Coevolutionary interactions are thought to have spurred the evolution of key innovations and driven the diversification of much of life on Earth. However, the genetic and evolutionary basis of the innovations that facilitate such interactions remains poorly understood. We examined the coevolutionary interactions between plants (Brassicales) and butterflies (Pieridae), and...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 6
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    In situ bubble vesiculation in silicic magmas (2011)
    Mineralogical Society of America
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    Publication Date: 2011-01-01
    Description: Volatile degassing is a major process driving volcanic eruptions. Therefore, a full understanding of mechanisms ranging from bubble nucleation, growth, coalescence, to magma fragmentation is required. We have simulated magma degassing during ascent in the volcanic conduit by depressurizing hydrated haplogranite melts in high-pressure and high-temperature optical cells (a hydrothermal diamond-anvil cell and an internally heated pressure vessel fitted with sapphire windows). This allowed the whole process of bubble nucleation, growth, and coalescence to be directly observed in situ through images captured from the recording videos. Bubble nucleation pressures, number densities, growth laws, and characteristics of coalescence were estimated as a function of melt water content, decompression rate, and temperature. Melt/vapor surface tension during bubble nucleation and coalescence was calculated. Our data show good agreement with those previously obtained in classical vessels. Methodological improvements are proposed for the experimental simulation of magma degassing in volcanic conduits.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 7
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    Systematic variation of the stellar initial mass function in early-type galaxies (2012)
    Nature Publishing Group (NPG)
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    Publication Date: 2012-04-28
    Description: Much of our knowledge of galaxies comes from analysing the radiation emitted by their stars, which depends on the present number of each type of star in the galaxy. The present number depends on the stellar initial mass function (IMF), which describes the distribution of stellar masses when the population formed, and knowledge of it is critical to almost every aspect of galaxy evolution. More than 50 years after the first IMF determination, no consensus has emerged on whether it is universal among different types of galaxies. Previous studies indicated that the IMF and the dark matter fraction in galaxy centres cannot both be universal, but they could not convincingly discriminate between the two possibilities. Only recently were indications found that massive elliptical galaxies may not have the same IMF as the Milky Way. Here we report a study of the two-dimensional stellar kinematics for the large representative ATLAS(3D) sample of nearby early-type galaxies spanning two orders of magnitude in stellar mass, using detailed dynamical models. We find a strong systematic variation in IMF in early-type galaxies as a function of their stellar mass-to-light ratios, producing differences of a factor of up to three in galactic stellar mass. This implies that a galaxy's IMF depends intimately on the galaxy's formation history.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cappellari, Michele -- McDermid, Richard M -- Alatalo, Katherine -- Blitz, Leo -- Bois, Maxime -- Bournaud, Frederic -- Bureau, M -- Crocker, Alison F -- Davies, Roger L -- Davis, Timothy A -- de Zeeuw, P T -- Duc, Pierre-Alain -- Emsellem, Eric -- Khochfar, Sadegh -- Krajnovic, Davor -- Kuntschner, Harald -- Lablanche, Pierre-Yves -- Morganti, Raffaella -- Naab, Thorsten -- Oosterloo, Tom -- Sarzi, Marc -- Scott, Nicholas -- Serra, Paolo -- Weijmans, Anne-Marie -- Young, Lisa M -- England -- Nature. 2012 Apr 25;484(7395):485-8. doi: 10.1038/nature10972.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of Oxford, Oxford OX1 3RH, UK. cappellari@astro.ox.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22538610" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 8
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    A black-hole mass measurement from molecular gas kinematics in NGC4526 (2013)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2013-02-01
    Description: The masses of the supermassive black holes found in galaxy bulges are correlated with a multitude of galaxy properties, leading to suggestions that galaxies and black holes may evolve together. The number of reliably measured black-hole masses is small, and the number of methods for measuring them is limited, holding back attempts to understand this co-evolution. Directly measuring black-hole masses is currently possible with stellar kinematics (in early-type galaxies), ionized-gas kinematics (in some spiral and early-type galaxies) and in rare objects that have central maser emission. Here we report that by modelling the effect of a black hole on the kinematics of molecular gas it is possible to fit interferometric observations of CO emission and thereby accurately estimate black-hole masses. We study the dynamics of the gas in the early-type galaxy NGC 4526, and obtain a best fit that requires the presence of a central dark object of 4.5(+4.2)(-3.1) x 10(8) solar masses (3sigma confidence limit). With the next-generation millimetre-wavelength interferometers these observations could be reproduced in galaxies out to 75 megaparsecs in less than 5 hours of observing time. The use of molecular gas as a kinematic tracer should thus allow one to estimate black-hole masses in hundreds of galaxies in the local Universe, many more than are accessible with current techniques.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Davis, Timothy A -- Bureau, Martin -- Cappellari, Michele -- Sarzi, Marc -- Blitz, Leo -- England -- Nature. 2013 Feb 21;494(7437):328-30. doi: 10.1038/nature11819. Epub 2013 Jan 30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching-bei-Munchen, Germany. tdavis@eso.org〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23364690" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 9
    Electronic Resource
    Electronic Resource
    γ-aminobutyric acid/benzodiazepine receptor protein carries binding sites for both ligands on both two major peptide subunits
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 153 (1988), S. 1006-1011 
    Details
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0006-291X(88)81328-7
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  • 10
    Electronic Resource
    Electronic Resource
    γ-aminobutyric acid/benzodiazepine receptor protein carries binding sites for both ligands on both two major peptide subunits
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 153 (1988), S. 1006-1011 
    Details
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0006-291X(88)81328-7
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