Estudos estruturais das enzimas envolvidas com o mecanismo de produção de ácidos orgânicos da bactéria G. Diazotrophicus utilizando métodos computacionais.

Ga5DH é uma enzima que exerce um papel fundamental na regulação do fluxo das fontes de carbono e energia nas bactérias, e na produção de Ácidos Orgânicos, entre eles o 5-Ceto-D-Gluconato (5KGA) [1,2]. Devido à importância deste ácido na indústria química [3], há um grande interesse em sua estrutura. Isto nos leva a apresentar a estrutura teórica de Ga5DH de Gluconacetobacter diazotrophicus, obtida com Modelagem por Homologia. Dez modelos foram gerados no programa MODELLER [4], baseados na estrutura de Gluconate 5- dehydrogenase de Streptococcus suis (PDB 3cxr), a única proteína Ga5DH resolvida experimentalmente até então.Trabalho apresentado na V Mostra de Trabalhos de Estagiários e Bolsistas, Campinas, out. 2009

Discovery of a faint, star-forming, multiply lensed, Lyman-alpha blob

We report the discovery of a multiply lensed Lyman-$\alpha$ blob (LAB) behind the galaxy cluster AS1063 using the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT). The background source is at $z=$ 3.117 and is intrinsically faint compared to almost all previously reported LABs. We used our highly precise strong lensing model to reconstruct the source properties, and we find an intrinsic luminosity of $L_{\rm Ly\alpha}$=$1.9\times10^{42}$ erg s$^{-1}$, extending to 33 kpc. We find that the LAB is associated with a group of galaxies, and possibly a protocluster, in agreement with previous studies that find LABs in overdensities. In addition to Lyman-$\alpha$ (Ly$\alpha$) emission, we find \ion{C}{IV}, \ion{He}{II}, and \ion{O}{III}] ultraviolet (UV) emission lines arising from the centre of the nebula. We used the compactness of these lines in combination with the line ratios to conclude that the \Lya nebula is likely powered by embedded star formation. Resonant scattering of the \Lya photons then produces the extended shape of the emission. Thanks to the combined power of MUSE and strong gravitational lensing, we are now able to probe the circumgalatic medium of sub-$L_{*}$ galaxies at $z\approx 3$.Comment: 7 pages, 7 figures; moderate changes to match the accepted A&A versoi

The story of supernova 'Refsdal' told by MUSE

We present MUSE observations in the core of the HFF galaxy cluster MACS J1149.5+2223, where the first magnified and spatially-resolved multiple images of SN 'Refsdal' at redshift 1.489 were detected. Thanks to a DDT program with the VLT and the extraordinary efficiency of MUSE, we measure 117 secure redshifts with just 4.8 hours of total integration time on a single target pointing. We spectroscopically confirm 68 galaxy cluster members, with redshift values ranging from 0.5272 to 0.5660, and 18 multiple images belonging to 7 background, lensed sources distributed in redshifts between 1.240 and 3.703. Starting from the combination of our catalog with those obtained from extensive spectroscopic and photometric campaigns using the HST, we select a sample of 300 (164 spectroscopic and 136 photometric) cluster members, within approximately 500 kpc from the BCG, and a set of 88 reliable multiple images associated to 10 different background source galaxies and 18 distinct knots in the spiral galaxy hosting SN 'Refsdal'. We exploit this valuable information to build 6 detailed strong lensing models, the best of which reproduces the observed positions of the multiple images with a rms offset of only 0.26". We use these models to quantify the statistical and systematic errors on the predicted values of magnification and time delay of the next emerging image of SN 'Refsdal'. We find that its peak luminosity should should occur between March and June 2016, and should be approximately 20% fainter than the dimmest (S4) of the previously detected images but above the detection limit of the planned HST/WFC3 follow-up. We present our two-dimensional reconstruction of the cluster mass density distribution and of the SN 'Refsdal' host galaxy surface brightness distribution. We outline the roadmap towards even better strong lensing models with a synergetic MUSE and HST effort.Comment: 21 pages, 9 figures, 6 tables; accepted for publication in the Astrophysical Journal - extra information on data analysis added, all model predictions and results unchange

CLASH-VLT: Testing the Nature of Gravity with Galaxy Cluster Mass Profiles

We use high-precision kinematic and lensing measurements of the total mass profile of the dynamically relaxed galaxy cluster MACS J1206.2-0847 at $z=0.44$ to estimate the value of the ratio $\eta=\Psi/\Phi$ between the two scalar potentials in the linear perturbed Friedmann-Lemaitre-Robertson-Walker metric.[...] Complementary kinematic and lensing mass profiles were derived from exhaustive analyses using the data from the Cluster Lensing And Supernova survey with Hubble (CLASH) and the spectroscopic follow-up with the Very Large Telescope (CLASH-VLT). Whereas the kinematic mass profile tracks only the time-time part of the perturbed metric (i.e. only $\Phi$), the lensing mass profile reflects the contribution of both time-time and space-space components (i.e. the sum $\Phi+\Psi$). We thus express $\eta$ as a function of the mass profiles and perform our analysis over the radial range $0.5\,Mpc\le r\le r_{200}=1.96\,Mpc$. Using a spherical Navarro-Frenk-White mass profile, which well fits the data, we obtain \eta(r_{200})=1.01\,_{-0.28}^{+0.31} at the 68\% C.L. We discuss the effect of assuming different functional forms for mass profiles and of the orbit anisotropy in the kinematic reconstruction. Interpreting this result within the well-studied $f(R)$ modified gravity model, the constraint on $\eta$ translates into an upper bound to the interaction length (inverse of the scalaron mass) smaller than 2 Mpc. This tight constraint on the $f(R)$ interaction range is however substantially relaxed when systematic uncertainties in the analysis are considered. Our analysis highlights the potential of this method to detect deviations from general relativity, while calling for the need of further high-quality data on the total mass distribution of clusters and improved control on systematic effects.Comment: 18 pages, 3 figures, submitted to JCA

Direct Lyman continuum and Lyman-alpha escape observed at redshift 4

We report on the serendipitous discovery of a z=4.0, M1500=-22.20 star-forming galaxy (Ion3) showing copious Lyman continuum (LyC) leakage (~60% escaping), a remarkable multiple peaked Lya emission, and significant Lya radiation directly emerging at the resonance frequency. This is the highest redshift confirmed LyC emitter in which the ionising and Lya radiation possibly share a common ionised cavity (with N_HI<10^17.2 cm^-2). Ion3 is spatially resolved, it shows clear stellar winds signatures like the P-Cygni NV1240 profile, and has blue ultraviolet continuum (\beta = -2.5 +/- 0.25, F_\lambda~ \lambda^\beta) with weak low-ionisation interstellar metal lines. Deep VLT/HAWKI Ks and Spitzer/IRAC 3.6um and 4.5um imaging show a clear photometric signature of the Halpha line with equivalent width of 1000A rest-frame emerging over a flat continuum (Ks-4.5um ~ 0). From the SED fitting we derive a stellar mass of 1.5x10^9 Msun, SFR of 140 Msun/yr and age of ~10 Myr, with a low dust extinction, E(B-V)< 0.1, placing the source in the starburst region of the SFR-M^* plane. Ion3 shows similar properties of another LyC emitter previously discovered (z=3.21, Ion2, Vanzella et al. 2016). Ion3 (and Ion2) represents ideal high-redshift reference cases to guide the search for reionising sources at z>6.5 with JWST.Comment: Accepted for publication in MNRAS. 5 pages, 4 figures, 1 tabl

Paving the way for the JWST: witnessing globular cluster formation at z>3

We report on five compact, extremely young (<10Myr) and blue (\beta_UV<-2.5, F_\lambda =\lambda^\beta) objects observed with VLT/MUSE at redshift 3.1169, 3.235, in addition to three objects at z=6.145. These sources are magnified by the Hubble Frontier Field galaxy clusters MACS~J0416 and AS1063. Their de-lensed half light radii (Re) are between 16 to 140pc, the stellar masses are ~1-20 X 10^6 Msun, the magnitudes are m_uv=28.8 - 31.4 (-17<Muv<-15) and specific star formation rates can be as large as ~800Gyr^-1. Multiple images of these systems are widely separated in the sky (up to 50'') and individually magnified by factors 3-40. Remarkably, the inferred physical properties of two objects are similar to those expected in some globular cluster formation scenarios, representing the best candidate proto-globular clusters (proto-GC) discovered so far. Rest-frame optical high dispersion spectroscopy of one of them at z=3.1169 yields a velocity dispersion \sigma_v~20km/s, implying a dynamical mass dominated by the stellar mass. Another object at z=6.145, with de-lensed Muv ~ -15.3 (m_uv ~ 31.4), shows a stellar mass and a star-formation rate surface density consistent with the values expected from popular GC formation scenarios. An additional star-forming region at z=6.145, with de-lensed m_uv ~ 32, a stellar mass of 0.5 X 10^6 Msun and a star formation rate of 0.06 Msun/yr is also identified. These objects currently represent the faintest spectroscopically confirmed star-forming systems at z>3, elusive even in the deepest blank fields. We discuss how proto-GCs might contribute to the ionization budget of the universe and augment Lya visibility during reionization. This work underlines the crucial role of JWST in characterizing the rest-frame optical and near-infrared properties of such low-luminosity high-z objects.Comment: 19 pages, 9 figures, 2 tables. MNRAS, version accepted by the refere

CLASH-VLT: Environment-driven evolution of galaxies in the z=0.209 cluster Abell 209

The analysis of galaxy properties and the relations among them and the environment, can be used to investigate the physical processes driving galaxy evolution. We study the cluster A209 by using the CLASH-VLT spectroscopic data combined with Subaru photometry, yielding to 1916 cluster members down to a stellar mass of 10^{8.6} Msun. We determine: i) the stellar mass function of star-forming and passive galaxies; ii) the intra-cluster light and its properties; iii) the orbits of low- and high-mass passive galaxies; and iv) the mass-size relation of ETGs. The stellar mass function of the star-forming galaxies does not depend on the environment, while the slope found for passive galaxies becomes flatter in the densest region. The color distribution of the intra-cluster light is consistent with the color of passive members. The analysis of the dynamical orbits shows that low-mass passive galaxies have tangential orbits, avoiding small pericenters around the BCG. The mass-size relation of low-mass passive ETGs is flatter than that of high mass galaxies, and its slope is consistent with that of field star-forming galaxies. Low-mass galaxies are also more compact within the scale radius of 0.65 Mpc. The ratio between stellar and number density profiles shows a mass segregation in the center. The comparative analysis of the stellar and total density profiles indicates that this effect is due to dynamical friction. Our results are consistent with a scenario in which the "environmental quenching" of low-mass galaxies is due to mechanisms such as harassment out to R200, starvation and ram-pressure stripping at smaller radii, as supported by the analysis of the mass function, of the dynamical orbits and of the mass-size relation of passive early-types in different regions. Our analyses support the idea that the intra-cluster light is formed through the tidal disruption of subgiant galaxies.Comment: 17 pages, 20 figures, A&A in pres

Dissection of the collisional and collisionless mass components in a mini sample of CLASH and HFF massive galaxy clusters at z≈0.4z \approx 0.4

We present a multi-wavelength study of the massive ($M_{200\textrm{c}} \approx 1$-$2 \times 10^{15} M_\odot$) galaxy clusters RXC J2248.7$-$4431, MACS J0416.1$-$2403, and MACS J1206.2$-$0847 at $z \approx 0.4$. Using the X-ray surface brightness of the clusters from deep Chandra data to model their hot gas, we are able to disentangle this mass term from the diffuse dark matter in our new strong-lensing analysis, with approximately $50$-$100$ secure multiple images per cluster, effectively separating the collisional and collisionless mass components of the clusters. At a radial distance of $10\%$ of $R_{200\textrm{c}}$ (approximately $200$ kpc), we measure a projected total mass of $(0.129 \pm 0.001)$, $(0.131 \pm 0.001)$ and $(0.137 \pm 0.001)\times M_{200\textrm{c}}$, for RXC J2248, MACS J0416 and MACS J1206, respectively. These values are surprisingly similar, considering the large differences in the merging configurations, and, as a consequence, in the mass models of the clusters. Interestingly, at the same radii, the hot gas over total mass fractions differ substantially, ranging from $0.082 \pm 0.001$ to $0.133 \pm 0.001$, reflecting the various dynamical states of the clusters. Moreover, we do not find a statistically significant offset between the positions of the peak of the diffuse dark matter component and of the BCG in the more complex clusters of the sample. We extend to this sample of clusters previous findings of a number of massive sub-halos higher than in numerical simulations. These results highlight the importance of a proper separation of the different mass components to study in detail the properties of dark matter in galaxy clusters.Comment: 19 pages, 11 figures, 7 tables; accepted for publication in the Astrophysical Journal; lensing models available at https://sites.google.com/site/vltclashpublic

The 500 ks Chandra observation of the z = 6.31 QSO SDSS J1030+0524

We present the results from a $\sim500$ ks Chandra observation of the $z=6.31$ QSO SDSS J1030+0524. This is the deepest X-ray observation to date of a $z\sim6$ QSO. The QSO is detected with a total of 125 net counts in the full ($0.5-7$ keV) band and its spectrum can be modeled by a single power-law model with photon index of $\Gamma = 1.81 \pm 0.18$ and full band flux of $f=3.95\times 10^{-15}$ erg s$^{-1}$ cm$^{-2}$. When compared with the data obtained by XMM-Newton in 2003, our Chandra observation in 2017 shows a harder ($\Delta \Gamma \approx -0.6$) spectrum and a 2.5 times fainter flux. Such a variation, in a timespan of $\sim2$ yrs rest-frame, is unexpected for such a luminous QSO powered by a $> 10^9 \: M_{\odot}$ black hole. The observed source hardening and weakening could be related to an intrinsic variation in the accretion rate. However, the limited photon statistics does not allow us to discriminate between an intrinsic luminosity and spectral change, and an absorption event produced by an intervening gas cloud along the line of sight. We also report the discovery of diffuse X-ray emission that extends for 30"x20" southward the QSO with a signal-to-noise ratio of $\sim$6, hardness ratio of $HR=0.03_{-0.25}^{+0.20}$, and soft band flux of $f_{0.5-2 \: keV}= 1.1_{-0.3}^{+0.3} \times 10^{-15}$ erg s$^{-1}$ cm$^{-2}$, that is not associated to a group or cluster of galaxies. We discuss two possible explanations for the extended emission, which may be either associated with the radio lobe of a nearby, foreground radio galaxy (at $z \approx 1-2$), or ascribed to the feedback from the QSO itself acting on its surrounding environment, as proposed by simulations of early black hole formation.Comment: 13 pages, 9 figures, A&A accepte

CLASH-VLT: A Highly Precise Strong Lensing Model of the Galaxy Cluster RXC J2248.7-4431 (Abell S1063) and Prospects for Cosmography

We perform a comprehensive study of the total mass distribution of the galaxy cluster RXCJ2248 ($z=0.348$) with a set of high-precision strong lensing models, which take advantage of extensive spectroscopic information on many multiply lensed systems. In the effort to understand and quantify inherent systematics in parametric strong lensing modelling, we explore a collection of 22 models where we use different samples of multiple image families, parametrizations of the mass distribution and cosmological parameters. As input information for the strong lensing models, we use the CLASH HST imaging data and spectroscopic follow-up observations, carried out with the VIMOS and MUSE spectrographs, to identify bona-fide multiple images. A total of 16 background sources, over the redshift range $1.0-6.1$, are multiply lensed into 47 images, 24 of which are spectroscopically confirmed and belong to 10 individual sources. The cluster total mass distribution and underlying cosmology in the models are optimized by matching the observed positions of the multiple images on the lens plane. We show that with a careful selection of a sample of spectroscopically confirmed multiple images, the best-fit model reproduces their observed positions with a rms of $0.3$ in a fixed flat $\Lambda$CDM cosmology, whereas the lack of spectroscopic information lead to biases in the values of the model parameters. Allowing cosmological parameters to vary together with the cluster parameters, we find (at $68\%$ confidence level) $\Omega_m=0.25^{+0.13}_{-0.16}$ and $w=-1.07^{+0.16}_{-0.42}$ for a flat $\Lambda$CDM model, and $\Omega_m=0.31^{+0.12}_{-0.13}$ and $\Omega_\Lambda=0.38^{+0.38}_{-0.27}$ for a universe with $w=-1$ and free curvature. Using toy models mimicking the overall configuration of RXCJ2248, we estimate the impact of the line of sight mass structure on the positional rms to be $0.3\pm 0.1$.(ABRIDGED)Comment: 23 pages, 13 figures, accepted for publication in A&