| 1. |
- Zenteno, A., et al.
(författare)
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A joint SZ-X-ray-optical analysis of the dynamical state of 288 massive galaxy clusters
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 495:1, s. 705-725
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Tidskriftsartikel (refereegranskat)abstract
- We use imaging from the first three years of the Dark Energy Survey to characterize the dynamical state of 288 galaxy clusters at 0.1 less than or similar to z less than or similar to 0.9 detected in the South Pole Telescope (SPT) Sunyaev-Zeldovich (SZ) effect survey (SPT-SZ). We examine spatial offsets between the position of the brightest cluster galaxy (BCG) and the centre of the gas distribution as traced by the SPT-SZ centroid and by the X-ray centroid/peak position from Chandra and XMM data. We show that the radial distribution of offsets provides no evidence that SPT SZ-selected cluster samples include a higher fraction of mergers than X-ray-selected cluster samples. We use the offsets to classify the dynamical state of the clusters, selecting the 43 most disturbed clusters, with half of those at z greater than or similar to 0.5, a region seldom explored previously. We find that Schechter function fits to the galaxy population in disturbed clusters and relaxed clusters differ at z > 0.55 but not at lower redshifts. Disturbed clusters at z > 0.55 have steeper faint-end slopes and brighter characteristic magnitudes. Within the same redshift range, we find that the BCGs in relaxed clusters tend to be brighter than the BCGs in disturbed samples, while in agreement in the lower redshift bin. Possible explanations includes a higher merger rate, and a more efficient dynamical friction at high redshift. The red-sequence population is less affected by the cluster dynamical state than the general galaxy population.
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| 2. |
- Rosati, P., et al.
(författare)
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Multi-wavelength study of XMMU J2235.3-2557 : the most massive galaxy cluster at z > 1
- 2009
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 508:2, s. 583-591
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Tidskriftsartikel (refereegranskat)abstract
- Context. The galaxy cluster XMMU J2235.3-2557 (hereafter XMM2235), spectroscopically confirmed at z = 1.39, is one of the most distant X-ray selected galaxy clusters. It has been at the center of a multi-wavelength observing campaign with ground and space facilities. Aims. We characterize the galaxy populations of passive members, the thermodynamical properties and metal abundance of the hot gas, and the total mass of the system using imaging data with HST/ACS (i(775) and z(850) bands) and VLT/ISAAC (J and K-S bands), extensive spectroscopic data obtained with VLT/FORS2, and deep (196 ks) Chandra observations. Methods. Chandra data allow temperature and metallicity to be measured with good accuracy and the X-ray surface brightness profile to be traced out to 1' (or 500 kpc), thus allowing the mass to be reliably estimated. Out of a total sample of 34 spectroscopically confirmed cluster members, we selected 16 passive galaxies (without detectable [OII]) within the central 2' (or 1 Mpc) with ACS coverage, and inferred star formation histories for subsamples of galaxies inside and outside the core by modeling their spectrophotometric data with spectral synthesis models. Results. Chandra data show a regular elongated morphology, closely resembling the distribution of core galaxies, with a significant cool core. We measure a global X-ray temperature of kT = 8.6(-1.2)(+1.3) keV (68% confidence), which we find to be robust against several systematics involved in the X-ray spectral analysis. By detecting the rest frame 6.7 keV Iron K line in the Chandra spectrum, we measure a metallicity Z = 0.26(-0.16)(+0.20) Z(circle dot). In the likely hypothesis of hydrostatic equilibrium, we obtain a total mass of M-tot( 1Mpc) = (5.9 +/- 1.3) x 10(14) M-circle dot. By modeling both the composite spectral energy distributions and spectra of the passive galaxies in and outside the core, we find a strong mean age radial gradient. Core galaxies, with stellar masses in excess of 10(11) M-circle dot, appear to have formed at an earlier epoch with a relatively short star formation phase (z = 5-6), whereas passive galaxies outside the core show spectral signatures suggesting a prolonged star formation phase to redshifts as low as z approximate to 2. Conclusions. Overall, our analysis implies that XMM2235 is the hottest and most massive bona-fide cluster discovered to date at z > 1, with a baryonic content, both its galaxy population and intracluster gas, in a significantly advanced evolutionary stage at 1/3 of the current age of the Universe.
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| 3. |
- Spagnuolo, M. S., et al.
(författare)
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A Short-Term Western Diet Impairs Cholesterol Homeostasis and Key Players of Beta Amyloid Metabolism in Brain of Middle Aged Rats
- 2020
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Ingår i: Molecular Nutrition & Food Research. - : Wiley. - 1613-4125 .- 1613-4133. ; 64:16
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Tidskriftsartikel (refereegranskat)abstract
- Scope Cholesterol homeostasis is crucial for brain functioning. Unhealthy nutrition can influence cerebral physiology, but the effect of western diets on brain cholesterol homeostasis, particularly at middle age, is unknown. Given the link between brain cholesterol alteration and beta amyloid production, the aim is to evaluate whether a diet rich in fat and fructose affects the protein network implicated in cholesterol synthesis and shuttling between glial cells and neurons, as well as crucial markers of beta amyloid metabolism. Methods and results Middle aged rats are fed a high fat-high fructose (HFF) or a control diet for 4 weeks. Inflammatory markers and cholesterol levels significantly increase in hippocampus of HFF rats. A higher activation of 3-hydroxy 3-methylglutaryl coenzyme-A reductase, coupled with lower levels of apolipoprotein E, LXR-beta, and lipoproteins receptors is measured in hippocampus from HFF rats. The alteration of critical players of cholesterol homeostasis is associated with increased level of amyloid precursor protein, presenilin 1, and nicastrin, and decreased level of insulin degrading enzyme. Conclusions Overall these data show that a western diet is associated with perturbation of cholesterol homeostasis in middle aged rats, mostly in hippocampus. This might trigger molecular events involved in the onset of neurodegenerative diseases.
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