220 research outputs found
Seismicity and seismogenic structures of Central Apennines (Italy): constraints on the present-day stress field from focal mechanisms â The SLAM (Seismicity of Lazio-Abruzzo and Molise) project
The aim of the SLAM (Seismicity of Lazio, Abruzzo and Molise region) project is to provide new insight on the seismotectonic and seismogenesis of a wide portion of central Italy situated between areas affected by
recent destructive events such as the 2009, Mw = 6.3, LâAquila earthquake to the north and the 2002, Mw = 5.8, Molise earthquake to the east. We present new results for the microseismic activity in the Central
Apennines, occurred in the period 2009 â 2013, by analyzing seismogram recordings from two temporary networks of up to 17 stations in combination with data from three networks of permanent stations
CLASH-VLT: Dissecting the Frontier Fields Galaxy Cluster MACS J0416.1-2403 with Spectra of Member Galaxies
We present VIMOS-VLT spectroscopy of the Frontier Fields cluster
MACS~J0416.1-2403 (z=0.397). Taken as part of the CLASH-VLT survey, the large
spectroscopic campaign provided more than 4000 reliable redshifts, including
~800 cluster member galaxies. The unprecedented sample of cluster members at
this redshift allows us to perform a highly detailed dynamical and structural
analysis of the cluster out to ~2.2 (~4Mpc). Our analysis of
substructures reveals a complex system composed of a main massive cluster
(~0.9) presenting two major features: i) a
bimodal velocity distribution, showing two central peaks separated by ~1100 km s with comparable galaxy content and velocity
dispersion, ii) a projected elongation of the main substructures along the
NE-SW direction, with a prominent subclump ~600 kpc SW of the center and an
isolated BCG approximately halfway between the center and the SW clump. We also
detect a low mass structure at z~0.390, ~10' S of the cluster center, projected
at ~3Mpc, with a relative line-of-sight velocity of ~-1700 km
s. The cluster mass profile that we obtain through our dynamical
analysis deviates significantly from the "universal" NFW, being best fit by a
Softened Isothermal Sphere model instead. The mass profile measured from the
galaxy dynamics is found to be in relatively good agreement with those obtained
from strong and weak lensing, as well as with that from the X-rays, despite the
clearly unrelaxed nature of the cluster. Our results reveal overall a complex
dynamical state of this massive cluster and support the hypothesis that the two
main subclusters are being observed in a pre-collisional phase, in line with
recent findings from radio and deep X-ray data. With this article we also
release the entire redshift catalog of 4386 sources in the field of this
cluster.Comment: Accepted for publication on ApJS. Revised to match the accepted
version; 21 pages, 18 figures, 9 tables. The CLASH-VLT spectroscopic catalogs
are publicly available at: http://sites.google.com/site/vltclashpublic
Phase transitions for -adic Potts model on the Cayley tree of order three
In the present paper, we study a phase transition problem for the -state
-adic Potts model over the Cayley tree of order three. We consider a more
general notion of -adic Gibbs measure which depends on parameter
\rho\in\bq_p. Such a measure is called {\it generalized -adic quasi Gibbs
measure}. When equals to -adic exponent, then it coincides with the
-adic Gibbs measure. When , then it coincides with -adic quasi
Gibbs measure. Therefore, we investigate two regimes with respect to the value
of . Namely, in the first regime, one takes for some
J\in\bq_p, in the second one . In each regime, we first find
conditions for the existence of generalized -adic quasi Gibbs measures.
Furthermore, in the first regime, we establish the existence of the phase
transition under some conditions. In the second regime, when we prove the existence of a quasi phase transition. It turns out that
if and \sqrt{-3}\in\bq_p, then one finds the existence
of the strong phase transition.Comment: 27 page
CLASH-VLT: Substructure in the galaxy cluster MACS J1206.2-0847 from kinematics of galaxy populations
In the effort to understand the link between the structure of galaxy clusters
and their galaxy populations, we focus on MACSJ1206.2-0847 at z~0.44 and probe
its substructure in the projected phase space through the spectrophotometric
properties of a large number of galaxies from the CLASH-VLT survey. Our
analysis is mainly based on an extensive spectroscopic dataset of 445 member
galaxies, mostly acquired with VIMOS@VLT as part of our ESO Large Programme,
sampling the cluster out to a radius ~2R200 (4 Mpc). We classify 412 galaxies
as passive, with strong Hdelta absorption (red and blue galaxies, and with
emission lines from weak to very strong. A number of tests for substructure
detection are applied to analyze the galaxy distribution in the velocity space,
in 2D space, and in 3D projected phase-space. Studied in its entirety, the
cluster appears as a large-scale relaxed system with a few secondary, minor
overdensities in 2D distribution. We detect no velocity gradients or evidence
of deviations in local mean velocities. The main feature is the WNW-ESE
elongation. The analysis of galaxy populations per spectral class highlights a
more complex scenario. The passive galaxies and red strong Hdelta galaxies
trace the cluster center and the WNW-ESE elongated structure. The red strong
Hdelta galaxies also mark a secondary, dense peak ~2 Mpc at ESE. The emission
line galaxies cluster in several loose structures, mostly outside R200. The
observational scenario agrees with MACS J1206.2-0847 having WNW-ESE as the
direction of the main cluster accretion, traced by passive galaxies and red
strong Hdelta galaxies. The red strong Hdelta galaxies, interpreted as
poststarburst galaxies, date a likely important event 1-2 Gyr before the epoch
of observation. The emission line galaxies trace a secondary, ongoing infall
where groups are accreted along several directions.Comment: A&A accepted, 19 pages, 30 figures, minor language change
CLASH-VLT: spectroscopic confirmation of a z=6.11 quintuply lensed galaxy in the Frontier Fields Cluster RXC J2248.7-4431
We present VIsible Multi-Object Spectrograph (VIMOS) observations of a z 6
galaxy quintuply imaged by the Frontier Fields galaxy cluster RXC J2248.7-4431
(z=0.348). This sub-L^*, high-z galaxy has been recently discovered by Monna et
al. (2013) using dropout techniques with the 16-band HST photometry acquired as
part of the Cluster Lensing And Supernova survey with Hubble (CLASH). Obtained
as part of the CLASH-VLT survey, the VIMOS medium-resolution spectra of this
source show a very faint continuum between ~8700A and ~9300A and a prominent
emission line at 8643A, which can be readily identified with Lyman-alpha at
z=6.110. The emission line exhibits an asymmetric profile, with a more
pronounced red wing. The rest-frame equivalent width of the line is EW=79+-10A.
After correcting for magnification, the star-formation rate (SFR) estimated
from the Lya line is SFR(Lya)=11 M_{sol}/yr and that estimated from the UV data
is SFR(UV)=3 M_{sol}/yr. We estimate that the effective radius of the source is
R_e6
M_{sol}/yr/kpc^2 and, using the Kennicutt-Schmidt relation, a gas surface mass
density Sigma_{gas}>10^3 M_{sol}/pc^2. Our results support the idea that this
magnified, distant galaxy is a young and compact object with 0.4 L^* at z=6,
with comparable amount of mass in gas and stars. Future follow-up observations
with ALMA will provide valuable insight into the SFR and molecular gas content
of this source. In the spirit of the Frontier Fields initiative, we also
publish the redshifts of several multiply imaged sources and other background
objects which will help improving the strong lensing model of this galaxy
cluster.Comment: 4 pages, 3 figures, 1 table, Accepted for publication in A&A (minor
changes, published version
Using a satellite swarm for building a space-based radio telescope for low frequencies
In radio astronomy, as in astronomy in general, a wide range of frequencies is observed as each spectral band o_ers a unique window to study astrophysical phenomena. In the recent years, new observatories have been designed and built at the extreme limits of the radio spectrum. For the low frequencies several Earth-based radio telescopes are constructed at this moment. In the Netherlands, the Low Frequency Array (LOFAR) is being constructed at this moment and will be operational later this year. LOFAR observes the sky between 30 and 240 MHz. Observing at even lower frequencies is very interesting, but, due to the inuence of the Earth's ionosphere this is not possible from Earth. Thus, the only option to observe low frequencies is a telescope in spac
Lead exposure in adult males in urban Transvaal Province, South Africa during the apartheid era
Human exposure to lead is a substantial public health hazard worldwide and is particularly problematic in the Republic of South Africa given the countryâs late cessation of leaded petrol. Lead exposure is associated with a number of serious health issues and diseases including developmental and cognitive deficiency, hypertension and heart disease. Understanding the distribution of lifetime lead burden within a given population is critical for reducing exposure rates. Femoral bone from 101 deceased adult males living in urban Transvaal Province (now Gauteng Province), South Africa between 1960 and 1998 were analyzed for lead concentration by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Of the 72 black and 29 white individuals sampled, chronic lead exposure was apparent in nearly all individuals. White males showed significantly higher median bone lead concentration (ME = 10.04 ”g·gâ1), than black males (ME = 3.80 ”g·gâ1) despite higher socioeconomic status. Bone lead concentration covaries significantly, though weakly, with individual age. There was no significant temporal trend in bone lead concentration. These results indicate that long-term low to moderate lead exposure is the historical norm among South African males. Unexpectedly, this research indicates that white males in the sample population were more highly exposed to lead
NEMO-SN1 Abyssal Cabled Observatory in the Western Ionian Sea
The âNEutrino Mediterranean Observatory - Submarine Network 1â (NEMO-SN1) seafloor observatory is located in the central
Mediterranean Sea, Western Ionian Sea, off Eastern Sicily (Southern Italy) at 2100 m water depth, 25 km from the harbour of the city of Catania. It is a prototype of a cabled deep-sea multiparameter observatory and the first one operating with real-time data transmission in Europe since 2005. NEMO-SN1 is also the first-established node of the âEuropean Multidisciplinary Seafloor and water column Observatoryâ (EMSO, http://www.emso-eu.org), one of the incoming European large-scale research infrastructures included in the Roadmap of the âEuropean Strategy Forum on Research Infrastructuresâ (ESFRI, http://cordis.europa.eu/esfri/roadmap.htm)
since 2006. EMSO will specifically address long-term monitoring of environmental processes related to Marine Ecosystems, Climate Change and Geo-hazards. NEMO-SN1 has been deployed and developed over the last decade thanks to Italian funding and to the EC project âEuropean Seas Observatory NETwork - Network of Excellenceâ (ESONET-NoE, 2007-2011) that funded the âListening to the Deep Ocean - Demonstration Missionâ (LIDO-DM) and a technological interoperability test (http://www.esonet-emso.org/). NEMOSN1 is performing geophysical and environmental long-term monitoring by acquiring seismological, geomagnetic, gravimetric, accelerometric, physico-oceanographic, hydroacoustic, bio-acoustic measurements. Scientific objectives include studying seismic signals,
tsunami generation and warnings, its hydroacoustic precursors, and ambient noise characterisation in terms of marine mammal sounds, environmental and anthropogenic sources. NEMO-SN1 is also an important test-site for the construction of the âKilometre-Cube Underwater Neutrino Telescopeâ (KM3NeT, http://www.km3net.org/), another large-scale research infrastructure included in the ESFRI Roadmap based on a large volume neutrino telescope. The description of the observatory and its most recent implementations is presented. On 9th June, 2012 NEMO-SN1 was successfully deployed and is working in real-time.Published358 - 3741.8. Osservazioni di geofisica ambientaleJCR Journalrestricte
OLFAR - orbiting low frequency array; using a satellite swarm for building a space-based radio telescope for low frequencies
In radio astronomy, as in astronomy in general, a wide range of frequencies is observed as each spectral band offers a unique window to study astrophysical phenomena. In the recent years, new observatories have been designed and built at the extreme limits of the radio spectrum. For the low frequencies several Earth-based radio telescopes are constructed at this moment. In the Netherlands, the Low Frequency Array (LOFAR) is being constructed at this moment and will be operational later this year. LOFAR observes the sky between 30 and 240 MHz. Observing at even lower frequencies is very interesting, but, due to the influence of the Earthâs ionosphere this is not possible from Earth. Thus, the only option to observe low frequencies is a telescope in space
Landuse and soil degradation in the southern Maya lowlands, from Pre-Classic to Post-Classic times : The case of La Joyanca (Petén, Guatemala)
International audienceThis work focuses on the impact of Maya agriculture on soil degradation. In site and out site studies in the area of the city of La Joyanca (NW Petén) show that "Maya clays" do not constitute a homogeneous unit, but represent a complex sedimentary record. A high resolution analysis leads us to document changes in rates and practices evolving in time in relation with major socio-political and economic changes. It is possible to highlight extensive agricultural practices between Early Pre-classical to Late Pre-classical times. Intensification occurs in relation with reduction of the fallow duration during Pre-classic to Classic periods. The consequences of these changes on soil erosion are discussed. However, it does not seem that the agronomic potential of the soils was significantly degraded before the end of the Classic period
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