9,075 research outputs found
SPIDER X - Environmental effects in central and satellite early-type galaxies through the stellar fossil record
A detailed analysis of how environment affects the star formation history of
early-type galaxies (ETGs) is undertaken via high signal to noise ratio stacked
spectra obtained from a sample of 20,977 ETGs (morphologically selected) from
the SDSS-based SPIDER survey. Two major parameters are considered for the
study: the central velocity dispersion (sigma), which relates to local drivers
of star formation, and the mass of the host halo, which relates to
environment-related effects. In addition, we separate the sample between
centrals (the most massive galaxy in a halo) and satellites. We derive trends
of age, metallicity, and [alpha/Fe] enhancement, with sigma. We confirm that
the major driver of stellar population properties in ETGs is velocity
dispersion, with a second-order effect associated to the central/satellite
nature of the galaxy. No environmental dependence is detected for satellite
ETGs, except at low sigma - where satellites in groups or in the outskirts of
clusters tend to be younger than those in the central regions of clusters. In
contrast, the trends for centrals show a significant dependence on halo mass.
Central ETGs in groups (i.e. with a halo mass >10^12.5 M_Sun) have younger
ages, lower [alpha/Fe], and higher internal reddening, than "isolated" systems
(i.e. centrals residing in low-mass, <10^12.5 M_Sun, halos). Our findings imply
that central ETGs in groups formed their stellar component over longer time
scales than "isolated" centrals, mainly because of gas-rich interactions with
their companion galaxies.Comment: 22 pages, 19 figures, accepted for publication in MNRA
Investigation of thin n-in-p planar pixel modules for the ATLAS upgrade
In view of the High Luminosity upgrade of the Large Hadron Collider (HL-LHC),
planned to start around 2023-2025, the ATLAS experiment will undergo a
replacement of the Inner Detector. A higher luminosity will imply higher
irradiation levels and hence will demand more ra- diation hardness especially
in the inner layers of the pixel system. The n-in-p silicon technology is a
promising candidate to instrument this region, also thanks to its
cost-effectiveness because it only requires a single sided processing in
contrast to the n-in-n pixel technology presently employed in the LHC
experiments. In addition, thin sensors were found to ensure radiation hardness
at high fluences. An overview is given of recent results obtained with not
irradiated and irradiated n-in-p planar pixel modules. The focus will be on
n-in-p planar pixel sensors with an active thickness of 100 and 150 um recently
produced at ADVACAM. To maximize the active area of the sensors, slim and
active edges are implemented. The performance of these modules is investigated
at beam tests and the results on edge efficiency will be shown
Assessing the influence of the carbon oxidation-reduction state on organic pollutant biodegradation in algal-bacterial photobioreactors
The influence of the carbon oxidation-reduction state (CORS) of organic pollutants on their biodegradation in enclosed algal-bacterial photobioreactors was evaluated using a consortium of enriched wild-type methanotrophic bacteria and microalgae. Methane, methanol and glucose (with CORS -4, -2 and 0, respectively) were chosen as model organic pollutants. In the absence of external oxygen supply, microalgal photosynthesis was not capable of supporting a significant methane and methanol biodegradation due to their high oxygen demands per carbon unit, while glucose was fully oxidized by photosynthetic oxygenation. When bicarbonate was added, removal efficiencies of 37¿±¿4% (20 days), 65¿±¿4% (11 days) and 100% (2 days) were recorded for CH(4,) CH(3)OH and C(6)H(12)O(6), respectively due to the additional oxygen generated from photosynthetic bicarbonate assimilation. The use of NO(3)(-) instead of NH(4)(+) as nitrogen source (N oxidation-reduction state of +5 vs. -3) resulted in an increase in CH(4) degradation from 0 to 33¿±¿3% in the absence of bicarbonate and from 37¿±¿4% to 100% in the presence of bicarbonate, likely due to a decrease in the stoichiometric oxygen requirements and the higher photosynthetic oxygen production. Hypothetically, the CORS of the substrates might affect the CORS of the microalgal biomass composition (higher lipid content). However, the total lipid content of the algal-bacterial biomass was 19¿±¿7% in the absence and 16¿±¿2% in the presence of bicarbonat
Performance of novel silicon n-in-p planar Pixel Sensors
The performance of novel n-in-p planar pixel detectors, designed for future
upgrades of the ATLAS Pixel system is presented. The n-in-p silicon sensors
technology is a promising candidate for the pixel upgrade thanks to its
radiation hardness and cost effectiveness, that allow for enlarging the area
instrumented with pixel detectors. The n-in-p modules presented here are
composed of pixel sensors produced by CiS connected by bump-bonding to the
ATLAS readout chip FE-I3. The characterization of these devices has been
performed before and after irradiation up to a fluence of 5 x 10**15 1 MeV neq
cm-2 . Charge collection measurements carried out with radioactive sources have
proven the functioning of this technology up to these particle fluences. First
results from beam test data with a 120 GeV/c pion beam at the CERN-SPS are also
discussed, demonstrating a high tracking efficiency of (98.6 \pm 0.3)% and a
high collected charge of about 10 ke for a device irradiated at the maximum
fluence and biased at 1 kV.Comment: Preprint submitted to Nuclear Instruments and Methods A. 7 pages, 13
figure
On the Nature of Fossil Galaxy Groups: Are they really fossils ?
We use SDSS-DR4 photometric and spectroscopic data out to redshift z~0.1
combined with ROSAT All Sky Survey X-ray data to produce a sample of
twenty-five fossil groups (FGs), defined as bound systems dominated by a
single, luminous elliptical galaxy with extended X-ray emission. We examine
possible biases introduced by varying the parameters used to define the sample
and the main pitfalls are discussed. The spatial density of FGs, estimated via
the V/V_ MAX} test, is 2.83 x 10^{-6} h_{75}^3 Mpc^{-3} for L_x > 0.89 x 10^42
h_{75}^-2 erg/s consistent with Vikhlinin et al. (1999), who examined an X-ray
overluminous elliptical galaxy sample (OLEG). We compare the general properties
of FGs identified here with a sample of bright field ellipticals generated from
the same dataset. These two samples show no differences in the distribution of
neighboring faint galaxy density excess, distance from the red sequence in the
color-magnitude diagram, and structural parameters such as a and internal
color gradients. Furthermore, examination of stellar populations shows that our
twenty-five FGs have similar ages, metallicities, and -enhancement as
the bright field ellipticals, undermining the idea that these systems represent
fossils of a physical mechanism that occurred at high redshift. Our study
reveals no difference between FGs and field ellipticals, suggesting that FGs
might not be a distinct family of true fossils, but rather the final stage of
mass assembly in the Universe.Comment: 18 pages, Accepted to A
Vascular Endothelial Growth Factor (VEGF) Prevents the Downregulation of the Cholinergic Phenotype in Axotomized Motoneurons of the Adult Rat
Vascular endothelial growth factor (VEGF) was initially characterized by its activity on the vascular system. However, there is growing evidence indicating that VEGF also acts as a neuroprotective factor, and that its administration to neurons suffering from trauma or disease is able to rescue them from cell death. We questioned whether VEGF could also maintain damaged neurons in a neurotransmissive mode by evaluating the synthesis of their neurotransmitter, and whether its action would be direct or through its well-known angiogenic activity. Adult rat extraocular motoneurons were chosen as the experimental model. Lesion was performed by monocular enucleation and immediately a gelatine sponge soaked in VEGF was implanted intraorbitally. After 7 days, abducens, trochlear, and oculomotor nuclei were examined by immunohistochemistry against choline acetyltransferase (ChAT), the biosynthetic enzyme of the motoneuronal neurotransmitter acetylcholine. Lesioned motoneurons exhibited a noticeable ChAT downregulation which was prevented by VEGF administration. To explore whether this action was mediated via an increase in blood vessels or in their permeability, we performed immunohistochemistry against laminin, glucose transporter-1 and the plasmatic protein albumin. The quantification of the immunolabeling intensity against these three proteins showed no significant differences between VEGF-treated, axotomized and control animals. Therefore, the present data indicate that VEGF is able to sustain the cholinergic phenotype in damaged motoneurons, which is a first step for adequate neuromuscular neurotransmission, and that this action seems to be mediated directly on neurons since no sign of angiogenic activity was evident. These data reinforces the therapeutical potential of VEGF in motoneuronal diseases.España, MINECO and FEDER BFU2015-64515-PJunta de Andalucía and FEDER : P10-CVI605
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