387 research outputs found
Assessment of anthropogenic influences on copper complexation by aquatic dissolved organic matter using synchronous fluorescence
Anthropogenic influences on the characteristics of aquatic dissolved organic matter (DOM) were evaluated in this work using synchronous fluorescence (SyF) scan spectroscopy. Samples from the Iraí and the Iguaçu Rivers were collected during the summer and winter at points located upstream and downstream from a heavily urbanized area in Brazil, respectively. DOM from all samples was titrated with Cu2+ and monitored by SyF quenching. A 1:1 non linear model was used for data treatment in, at least, five distinct regions of the spectra. Results revealed that during the rainy summer, DOM from both rivers exhibited simple organic structures such as aromatic amino acids or conjugated aliphatics as the major constituents, probably arising from non-point sources. However, during the dry winter it became clear that raw sewage discharges arising from the urbanized area contributed to an increase of fluorescent organic matter that is unable to complex copper
An in-line clean system for the solid-phase extraction of emerging contaminants in natural waters
A solid-phase in-line extraction system for water samples containing low levels of emerging contaminants is described. The system was specially developed for large volume samples (up to 4 L) using commercial solid-phase extraction (SPE) cartridges. Four sets containing PTFE-made connectors, brass adapters and ball valves were used to fit SPE cartridges and sample bottles to a 4-port manifold attached to a 20 L carboy. A lab-made vacuum device was connected to the manifold cap. The apparatus is robust and less expensive than the typical available system. Its also provides less experimental handling, avoiding cross contamination and sample losses.21621
The optical/X-ray connection: ICM iron content and galaxy optical luminosity in 20 galaxy clusters
X-ray observations of galaxy clusters have shown that the intra-cluster gas
has iron abundances of about one third of the solar value. These observations
also show that part (if not all) of the intra-cluster gas metals were produced
within the member galaxies. We present a systematic analysis of 20 galaxy
clusters to explore the connection between the iron mass and the total
luminosity of early-type and late-type galaxies, and of the brightest cluster
galaxies (BCGs). From our results, the intra-cluster medium (ICM) iron mass
seems to correlate better with the luminosity of the BCGs than with that of the
red and blue galaxy populations. As the BCGs cannot produce alone the observed
amount of iron, we suggest that ram-pressure plus tidal stripping act together
to enhance, at the same time, the BCG luminosities and the iron mass in the
ICM. Through the analysis of the iron yield, we have also estimated that SN Ia
are responsible for more than 50% of the total iron in the ICM. This result
corroborates the fact that ram-pressure contributes to the gas removal from
galaxies to the inta-cluster medium, being very efficient for clusters in the
temperature range 2 < kT (keV)< 10Comment: Accepted for publication in MNRAS (11 pg, 9 figures and 3 tables
Two spectroscopically confirmed galaxy structures at z=0.61 and 0.74 in the CFHTLS Deep~3 field
Adami et al. (2010) have detected several cluster candidates at z>0.5 as part
of a systematic search for clusters in the Canada France Hawaii Telescope
Legacy Survey, based on photometric redshifts. We focus here on two of them,
located in the D3 field: D3-6 and D3-43. We have obtained spectroscopy with
Gemini/GMOS and measured redshifts for 23 and 14 galaxies in the two
structures. These redshifts were combined with those available in the
literature. A dynamical and a weak lensing analysis were also performed,
together with the study of X-ray Chandra archive data. Cluster D3-6 is found to
be a single structure of 8 spectroscopically confirmed members at an average
redshift z=0.607, with a velocity dispersion of 423 km/s. It appears to be a
relatively low mass cluster. D3-43-S3 has 46 spectroscopically confirmed
members at an average redshift z=0.739. It can be decomposed into two main
substructures, having a velocity dispersion of about 600 and 350 km/s. An
explanation to the fact that D3-43-S3 is detected through weak lensing (only
marginally, at the ~3sigma level) but not in X-rays could be that the two
substructures are just beginning to merge more or less along the line of sight.
We also show that D3-6 and D3-43-S3 have similar global galaxy luminosity
functions, stellar mass functions, and star formation rate (SFR) distributions.
The only differences are that D3-6 exhibits a lack of faint early type
galaxies, a deficit of extremely high stellar mass galaxies compared to
D3-43-S3, and an excess of very high SFR galaxies. This study shows the power
of techniques based on photometric redshifts to detect low to moderately
massive structures, even at z~0.75.Comment: Accepted in A&A, final version, shortened abstrac
The galaxy environment in GAMA G3C groups using the Kilo Degree Survey Data Release 3
We aim to investigate the galaxy environment in GAMA Galaxy Groups Catalogue
(G3C) using a volume-limited galaxy sample from the Kilo Degree Survey Data
Release 3. The k-Nearest Neighbour technique is adapted to take into account
the probability density functions (PDFs) of photometric redshifts in our
calculations. This algorithm was tested on simulated KiDS tiles, showing its
capability of recovering the relation between galaxy colour, luminosity and
local environment. The characterization of the galaxy environment in G3C groups
shows systematically steeper density contrasts for more massive groups. The red
galaxy fraction gradients in these groups is evident for most of group mass
bins. The density contrast of red galaxies is systematically higher at group
centers when compared to blue galaxy ones. In addition, distinct group center
definitions are used to show that our results are insensitive to center
definitions. These results confirm the galaxy evolution scenario which
environmental mechanisms are responsible for a slow quenching process as
galaxies fall into groups and clusters, resulting in a smooth observed colour
gradients in galaxy systems.Comment: 14 pages, Accepted to MNRA
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