195 research outputs found
Estudos estruturais das enzimas envolvidas com o mecanismo de produção de åcidos orgùnicos da bactéria G. Diazotrophicus utilizando métodos computacionais.
Ga5DH Ă© uma enzima que exerce um papel fundamental na regulação do fluxo das fontes de carbono e energia nas bactĂ©rias, e na produção de Ăcidos OrgĂąnicos, entre eles o 5-Ceto-D-Gluconato (5KGA) [1,2]. Devido Ă importĂąncia deste ĂĄcido na indĂșstria quĂmica [3], hĂĄ um grande interesse em sua estrutura. Isto nos leva a apresentar a estrutura teĂłrica 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 Ășnica proteĂna Ga5DH resolvida experimentalmente atĂ© entĂŁo.Trabalho apresentado na V Mostra de Trabalhos de EstagiĂĄrios 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- 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 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 =
erg s, 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-
(Ly) 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-
galaxies at .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
to estimate the value of the ratio 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 ), the lensing mass
profile reflects the contribution of both time-time and space-space components
(i.e. the sum ). We thus express as a function of the mass
profiles and perform our analysis over the radial range . 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 modified gravity model,
the constraint on translates into an upper bound to the interaction
length (inverse of the scalaron mass) smaller than 2 Mpc. This tight constraint
on the 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
Dissection of the collisional and collisionless mass components in a mini sample of CLASH and HFF massive galaxy clusters at
We present a multi-wavelength study of the massive (-) galaxy clusters RXC J2248.74431, MACS
J0416.12403, and MACS J1206.20847 at . 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 - secure multiple
images per cluster, effectively separating the collisional and collisionless
mass components of the clusters. At a radial distance of of
(approximately kpc), we measure a projected total
mass of , and , 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 to , 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
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
The 500 ks Chandra observation of the z = 6.31 QSO SDSS J1030+0524
We present the results from a ks Chandra observation of the
QSO SDSS J1030+0524. This is the deepest X-ray observation to date of
a QSO. The QSO is detected with a total of 125 net counts in the full
( keV) band and its spectrum can be modeled by a single power-law model
with photon index of and full band flux of
erg s cm. When compared with the data
obtained by XMM-Newton in 2003, our Chandra observation in 2017 shows a harder
() spectrum and a 2.5 times fainter flux. Such a
variation, in a timespan of yrs rest-frame, is unexpected for such a
luminous QSO powered by a 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 6, hardness ratio of
, and soft band flux of erg s cm, 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 ), 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 () 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 , 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 in a fixed flat 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 confidence level)
and for a flat
CDM model, and and
for a universe with 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 .(ABRIDGED)Comment: 23 pages, 13 figures, accepted for publication in A&
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