1,184 research outputs found
The luminosity and stellar mass Fundamental Plane of early-type galaxies
From a sample of ~50000 early-type galaxies from the SDSS, we measured the
traditional Fundamental Plane in four bands. We then replaced luminosity with
stellar mass, and measured the "stellar mass" FP. The FP steepens slightly as
one moves from shorter to longer wavelengths: the orthogonal fit has slope 1.40
in g and 1.47 in z. The FP is thinner at longer wavelengths: scatter is 0.062
dex in g, 0.054 dex in z. The scatter is larger at small galaxy sizes/masses;
at large masses measurement errors account for essentially all of the observed
scatter. The FP steepens further when luminosity is replaced with stellar mass,
to slope ~ 1.6. The intrinsic scatter also reduces further, to 0.048 dex. Since
color and stellar mass-to-light ratio are closely related, this explains why
color can be thought of as the fourth FP parameter. However, the slope of the
stellar mass FP remains shallower than the value of 2 associated with the
virial theorem. This is because the ratio of dynamical to stellar mass
increases at large masses as M_d^0.17. The face-on view of the stellar mass
kappa-space suggests that there is an upper limit to the stellar density for a
given dynamical mass, and this decreases at large masses: M_*/R_e^3 ~ M_d^-4/3.
We also study how the estimated coefficients a and b of the FP are affected by
other selection effects (e.g. excluding small sigma biases a high; excluding
fainter L biases a low). These biases are seen in FPs which have no intrinsic
curvature, so the observation that a and b scale with L and sigma is not, by
itself, evidence that the Plane is warped. We show that the FP appears to curve
sharply downwards at the small mass end, and more gradually downwards towards
larger masses. Whereas the drop at small sizes is real, most of the latter
effect is due to correlated errors.Comment: 17 pages, 15 figures, MNRAS in press. Added appendix on possible
sample contamination by disk
Colour Gradients and the Colour-Magnitude Relation: Different Properties of Brightest Cluster Galaxies and E/S0 Galaxies in the Sloan Digital Sky Survey
We examine the colour-magnitude relation of approximately 5000 Brightest
Cluster Galaxies (BCGs) in the Sloan Digital Sky Survey, and compare with
non-BCG E/S0 galaxies. The colour-magnitude and colour-sigma (velocity
dispersion) relations are flatter in slope (by a factor of about 2) for BCGs
than for non-BCG E/S0s, and the BCGs also tend to be redder by 0.01 magnitudes
in g-r. We investigate radial colour gradients in both samples, using the ratio
of the de Vaucouleurs radii in the g and r bands. We find BCGs have
significantly flatter (by 23%) mean colour gradients than other high luminosity
E/S0s. In early-type galaxies, the colour gradients are strongest at
intermediate luminosities of Mr=-22. Colour gradients in E/S0s increase with
radius (up to 10kpc) and are negatively correlated with 10sigma + Mr (velocity
dispersion relative to luminosity) and with mass density. The gradients also
tend to decrease with increasing stellar age. These trends are weak or not seen
in BCGs, in which the mean colour gradient is low whatever the other
properties. We discuss possible explanations, which involve a greater amount of
dry merging in the formation history of the BCGs.Comment: 16 pages, 24 figures, revised, accepted for publication in MNRAS
Strong lens search in the ESO public Survey KiDS
We have started a systematic search of strong lens candidates in the ESO
public survey KiDS based on the visual inspection of massive galaxies in the
redshift range . As a pilot program we have inspected 100 sq. deg.,
which overlap with SDSS and where there are known lenses to use as a control
sample. Taking advantage of the superb image quality of VST/OmegaCAM, the
colour information and accurate model subtracted images, we have found 18 new
lens candidates, for which spectroscopic confirmation will be needed to confirm
their lensing nature and study the mass profile of the lensing galaxies.Comment: 4 pages, 1 figure, to appear on the refereed Proceeding of the "The
Universe of Digital Sky Surveys" conference held at the INAF--OAC, Naples, on
25th-28th november 2014, to be published on Astrophysics and Space Science
Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodic
Detection of small-molecule enzyme inhibitors with peptides isolated from phage-displayed combinatorial peptide libraries
AbstractBackground: The rapidly expanding list of pharmacologically important targets has highlighted the need for ways to discover new inhibitors that are independent of functional assays. We have utilized peptides to detect inhibitors of protein function. We hypothesized that most peptide ligands identified by phage display would bind to regions of biological interaction in target proteins and that these peptides could be used as sensitive probes for detecting low molecular weight inhibitors that bind to these sites.Results: We selected a broad range of enzymes as targets for phage display and isolated a series of peptides that bound specifically to each target. Peptide ligands for each target contained similar amino acid sequences and competition analysis indicated that they bound one or two sites per target. Of 17 peptides tested, 13 were found to be specific inhibitors of enzyme function. Finally, we used two peptides specific for Haemophilus influenzae tyrosyl-tRNA synthetase to show that a simple binding assay can be used to detect small-molecule inhibitors with potencies in the micromolar to nanomolar range.Conclusions: Peptidic surrogate ligands identified using phage display are preferentially targeted to a limited number of sites that inhibit enzyme function. These peptides can be utilized in a binding assay as a rapid and sensitive method to detect small-molecule inhibitors of target protein function. The binding assay can be used with a variety of detection systems and is readily adaptable to automation, making this platform ideal for high-throughput screening of compound libraries for drug discovery
The Faber-Jackson relation for early-type galaxies: Dependence on the magnitude range
We take a sample of early-type galaxies from the Sloan Digital Sky Survey
(SDSS-DR7, 90 000 galaxies) spanning a range of approximately 7 in
both and filters and analyse the behaviour of the Faber-Jackson
relation parameters as functions of the magnitude range. We calculate the
parameters in two ways: i) We consider the faintest (brightest) galaxies in
each sample and we progressively increase the width of the magnitude interval
by inclusion of the brighter (fainter) galaxies
(increasing-magnitude-intervals), and ii) we consider narrow-magnitude
intervals of the same width ( ) over the whole magnitude
range available (narrow-magnitude-intervals). Our main results are that: i) in
both increasing and narrow-magnitude-intervals the Faber-Jackson relation
parameters change systematically, ii) non-parametric tests show that the
fluctuations in the values of the slope of the Faber-Jackson relation are not
products of chance variations. We conclude that the values of the Faber-Jackson
relation parameters depend on the width of the magnitude range and the
luminosity of galaxies within the magnitude range. This dependence is caused,
to a great extent by the selection effects and because the geometrical shape of
the distribution of galaxies on the plane depends on
luminosity. We therefore emphasize that if the luminosity of galaxies or the
width of the magnitude range or both are not taken into consideration when
comparing the structural relations of galaxy samples for different wavelengths,
environments, redshifts and luminosities, any differences found may be
misinterpreted.Comment: 15 pages, 5 figures. A&A. Accepte
SPIDER VII - Revealing the Stellar Population Content of Massive Early-type Galaxies out to 8Re
Radial trends of stellar populations in galaxies provide a valuable tool to
understand the mechanisms of galaxy growth. In this paper, we present the first
comprehensive analysis of optical-optical and optical-NIR colours, as a
function of galaxy mass, out to the halo region (8Re) of early-type galaxies
(ETGs). We select a sample of 674 massive ETGs (M*>3x10^10MSun) from the
SDSS-based SPIDER survey. By comparing with a large range of population
synthesis models, we derive robust constraints on the radial trends in age and
metallicity. Metallicity is unambiguously found to decrease outwards, with a
measurable steepening of the slope in the outer regions (Re<R<8Re). The
gradients in stellar age are found to be more sensitive to the models used, but
in general, the outer regions of ETGs feature older populations compared to the
cores. This trend is strongest for the most massive galaxies in our sample
(M*>10^11MSun). Furthermore, when segregating with respect to large scale
environment, the age gradient is more significant in ETGs residing in higher
density regions. These results shed light on the processes leading from the
formation of the central core to the growth of the stellar envelope of massive
galaxies. The fact that the populations in the outer regions are older and more
metal-poor than in the core suggests a process whereby the envelope of massive
galaxies is made up of accreted small satellites (i.e. minor mergers) whose
stars were born during the first stages of galaxy formation.Comment: 20 pages, 13 figures, 10 tables. Accepted for publication in MNRA
Assembling sustainable ideas: The construction process of the proposal SMLsystem at the Solar Decathlon Europe 2012
[EN] The innovation of the construction process in SMLsystem lies in an evolution of the way of thinking the sustainable architecture. The key is that SMLsystem proposal is not constructed but is assembled. This way, it is designed with prefabricated and industrialized elements which allow themselves to connect as in a plug and play process in order to reduce the risks and save time and costs consequently. About that, the study and design of the junction has been another interesting issue to solve the assembly of the modules, focusing on factors like the isolation and the rainwater always present. In addition this proposal shows a new way in the use of wood as a structural material, as a building enclosure and as a dynamic system of solar protection, all of them as a result of the combination of various premises inherent to the concept of the project like the respect for the environment, recycling or sustainability and, of course, with an absolute integration with the architectural design. This way, the complete development of SMLsystem has had the capacity of defining a global project which reflects the primal ideas: design, sustainability, modularity, flexibility and prefabrication. © 2014 Elsevier B.V. All rights reserved.The research reflected in this paper has been possible thanks to the support of the CEU Cardenal Herrera University and of many companies who have contributed to the realization of housing SMLsystem. This effort and commitment to research are translated into a competitive, quality teaching and research staff improvement and also as a result to the University advance.Serra Soriano, B.; Verdejo Gimeno, P.; Diaz Segura, AL.; Meri De La Maza, RM. (2014). Assembling sustainable ideas: The construction process of the proposal SMLsystem at the Solar Decathlon Europe 2012. Energy and Buildings. 83:186-194. doi:10.1016/j.enbuild.2014.03.075S1861948
Anti-nausea effects and pharmacokinetics of ondansetron, maropitant and metoclopramide in a low-dose cisplatin model of nausea and vomiting in the dog: a blinded crossover study
Nausea is a subjective sensation which is difficult to measure in non-verbal species. The aims of this study were to determine the efficacy of three classes of antiemetic drugs in a novel low dose cisplatin model of nausea and vomiting and measure change in potential nausea biomarkers arginine vasopressin (AVP) and cortisol. A four period cross-over blinded study was conducted in eight healthy beagle dogs of both genders. Dogs were administered 18 mg/m2 cisplatin intravenously, followed 45 min later by a 15 min infusion of either placebo (saline) or antiemetic treatment with ondansetron (0.5 mg/kg; 5-HT3 antagonist), maropitant (1 mg/kg; NK1 antagonist) or metoclopramide (0.5 mg/kg; D2 antagonist). The number of vomits and nausea associated behaviours, scored on a visual analogue scale, were recorded every 15 min for 8 h following cisplatin administration. Plasma samples were collected to measure AVP, cortisol and antiemetic drug concentrations
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