51 research outputs found
Characteristics of Gravity Waves over an Antarctic Ice Sheet during an Austral Summer
While occurrences of wavelike motion in the stable boundary layer due to the presence of a significant restoring buoyancy force are rarely disputed, their modalities and interaction with turbulence remain a subject of active research. In this work, the characteristics of gravity waves and their impact on flow statistics, including turbulent fluxes, are presented using data collected above an Antarctic Ice sheet during an Austral Summer. Antarctica is an ideal location for exploring the characteristics of gravity waves because of persistent conditions of strong atmospheric stability in the lower troposphere. Periods dominated by wavelike motion have been identified by analysing time series measured by fast response instrumentation. The nature and characteristic of the dominant wavy motions are investigated using Fourier cross-spectral indicators. Moreover, a multi-resolution decomposition has been applied to separate gravity waves from turbulent fluctuations in case of a sufficiently defined spectral gap. Statistics computed after removing wavy disturbances highlight the large impact of gravity waves on second order turbulent quantities including turbulent flux calculations
Structural and dynamical modeling of WINGS clusters. I. The distribution of cluster galaxies of different morphological classes within regular and irregular clusters
[Abridged] We use the WINGS database to select a sample of 67 nearby galaxy
clusters with at least 30 spectroscopic members each. 53 of these clusters do
not show evidence of substructures in phase-space, while 14 do. We estimate the
virial radii and circular velocities of the 67 clusters by a variety of proxies
(velocity dispersion, X-ray temperature, and richness) and use these estimates
to build stack samples from these 53 and 14 clusters ('Reg' and 'Irr' stacks,
respectively). We determine the number-density and velocity-dispersion profiles
(VDPs) of E, S0, and Sp+Irr (S) galaxies in the Reg and Irr samples,
separately, and fit models to these profiles. The number density profiles of E,
S0, and S galaxies are adequately described by either a NFW or a cored King
model, both for the Reg and Irr samples, with a slight preference for the NFW
model. The spatial distribution concentration increases from the S to the S0
and to the E populations, both in the Reg and the Irr stacks, reflecting the
well-known morphology-radius relation. Reg clusters have a more concentrated
spatial distribution of E and S0 galaxies than Irr clusters, while the spatial
distributions of S galaxies in Reg and Irr clusters are similar. We propose a
new phenomenological model that provides acceptable fits to the VDP of all our
galaxy samples. The VDPs become steeper and with a higher normalization from E
to S0 to S galaxies. The S0 VDP is close to that of E galaxies in Reg clusters,
and intermediate between those of E and S galaxies in Irr clusters. Our results
suggest that S galaxies are a recently accreted cluster population, that take
less than 3 Gyr to evolve into S0 galaxies after accretion, and in doing so
modify their phase-space distribution, approaching that of cluster ellipticals.
While in Reg clusters this evolutionary process is mostly completed, it is
still ongoing in Irr clusters.Comment: A&A, in press - 11 pages, 9 figures, 4 table
Clostridium difficile infection in Italian urban hospitals: data from 2006 through 2011
BACKGROUND: In developed countries, Clostridium difficile infection (CDI) represents an emerging threat in terms of morbidity and mortality rates. In our country limited CDI epidemiological data can be found. We have conducted a 6-year retrospective study to evaluate the incidence of CDI in Italian urban hospitals. METHODS: Stool samples tested for C. difficile toxins from January 2006 to December 2011 in 5 large hospitals in Rome, Italy, were considered in the analysis. Repeated samples takenââ€â2 months after a positive result were excluded. RESULTS: A total of 402 CDI episodes were identified. The incidence of CDI episodes progressively increased from 0.3 in 2006 to 2.3 per 10,000 patient-days in 2011. CDI episodes mostly occurred in patientsâ>â60 years of age (77%). The >80 year-old age class reported the highest percentage of CDI episodes on tested samples (16%). Eighty percent (80%) of CDI episodes occurred in medical wards followed by surgery (10.2%) and intensive care units (9.8%). CONCLUSIONS: A significant increasing incidence of CDI episodes over the study period was observed during the years (p<.001), particularly in the older age groups. Medical wards experienced the highest number of CDI episodes as compared to intensive care and surgical wards. The increasing rate of CDI episodes over the last six years in our country, is alarming; urgent improvements in the surveillance systems and control programs are advisable
Surface photometry of WINGS galaxies with GASPHOT
Aims. We present the B-, V- and K-band surface photometry catalogs obtained
running the automatic software GASPHOT on galaxies from the WINGS cluster
survey having isophotal area larger than 200 pixels. The catalogs can be
downloaded at the Centre de Donnees Astronomiques de Strasbourg (CDS). Methods.
We outline the GASPHOT performances and compare our surface photometry with
that obtained by SExtractor, GALFIT and GIM2D. This analysis is aimed at
providing statistical information about the accuracy generally achieved by the
softwares for automatic surface photometry of galaxies. Results. For each
galaxy and for each photometric band the GASPHOT catalogs provide the
parameters of the Sersic law best-fitting the luminosity profiles. They are:
the sky coordinates of the galaxy center (R:A:; DEC:), the total magnitude (m),
the semi-major axis of the effective isophote (Re), the Sersic index (n), the
axis ratio (b=a) and a flag parameter (QFLAG) giving a global indication of the
fit quality. The WINGS-GASPHOT database includes 41,463 galaxies in the B-band,
42,275 in the V-band, and 71,687 in the K-band. We find that the bright
early-type galaxies have larger Sersic indices and effective radii, as well as
redder colors in their center. In general the effective radii increase
systematically from the K- to the V- and B-band. Conclusions. The GASPHOT
photometry turns out to be in fairly good agreement with the surface photometry
obtained by GALFIT and GIM2D, as well as with the aperture photometry provided
by SExtractor. The main advantages of GASPHOT with respect to other tools are:
(i) the automatic finding of the local PSF; (ii) the short CPU time of
execution; (iii) the remarkable stability against the choice of the initial
guess parameters. All these characteristics make GASPHOT an ideal tool for
blind surface photometry of large galaxy samples in wide-field CCD mosaics.Comment: 14 pages, 9 figure
Galaxy stellar mass functions of different morphological types in clusters, and their evolution between z=0.8 and z=0
We present the galaxy stellar mass function (MF) and its evolution in
clusters from z~0.8 to the current epoch, based on the WIde-field Nearby
Galaxy-cluster Survey (WINGS) (0.04<z<0.07), and the ESO Distant Cluster Survey
(EDisCS) (0.4<z <0.8). We investigate the total MF and find it evolves
noticeably with redshift. The shape at M*>10^11 M' does not evolve, but below
M*~10^10.8 M' the MF at high redshift is flat, while in the Local Universe it
flattens out at lower masses. The population of M* = 10^10.2 - 10^10.8 M'
galaxies must have grown significantly between z=0.8 and z=0. We analyze the MF
of different morphological types (ellipticals, S0s and late-types), and find
that also each of them evolves with redshift. All types have proportionally
more massive galaxies at high- than at low-z, and the strongest evolution
occurs among S0 galaxies. Examining the morphology-mass relation (the way the
proportion of galaxies of different morphological types changes with galaxy
mass), we find it strongly depends on redshift. At both redshifts, ~40% of the
stellar mass is in elliptical galaxies. Another ~43% of the mass is in S0
galaxies in local clusters, while it is in spirals in distant clusters. To
explain the observed trends, we discuss the importance of those mechanisms that
could shape the MF. We conclude that mass growth due to star formation plays a
crucial role in driving the evolution. It has to be accompanied by infall of
galaxies onto clusters, and the mass distribution of infalling galaxies might
be different from that of cluster galaxies. However, comparing with high-z
field samples, we do not find conclusive evidence for such an environmental
mass segregation. Our results suggest that star formation and infall change
directly the MF of late-type galaxies in clusters and, indirectly, that of
early-type galaxies through subsequent morphological transformations.Comment: MNRAS in press, 24 pages, 19 figures and 8 table
Ram pressure feeding super-massive black holes
When supermassive black holes at the center of galaxies accrete matter
(usually gas), they give rise to highly energetic phenomena named Active
Galactic Nuclei (AGN). A number of physical processes have been proposed to
account for the funneling of gas towards the galaxy centers to feed the AGN.
There are also several physical processes that can strip gas from a galaxy, and
one of them is ram pressure stripping in galaxy clusters due to the hot and
dense gas filling the space between galaxies. We report the discovery of a
strong connection between severe ram pressure stripping and the presence of AGN
activity. Searching in galaxy clusters at low redshift, we have selected the
most extreme examples of jellyfish galaxies, which are galaxies with long
tentacles of material extending for dozens of kpc beyond the galaxy disk. Using
the MUSE spectrograph on the ESO Very Large Telescope, we find that 6 out of
the 7 galaxies of this sample host a central AGN, and two of them also have
galactic-scale AGN ionization cones. The high incidence of AGN among the most
striking jellyfishes may be due to ram pressure causing gas to flow towards the
center and triggering the AGN activity, or to an enhancement of the stripping
caused by AGN energy injection, or both. Our analysis of the galaxy position
and velocity relative to the cluster strongly supports the first hypothesis,
and puts forward ram pressure as another, yet unforeseen, possible mechanism
for feeding the central supermassive black hole with gas.Comment: published in Nature, Vol.548, Number 7667, pag.30
VizieR Online Data Catalog: OmegaWINGS local clusters of galaxies redshifts (Moretti+, 2017)
Redshifts, magnitude/radial completeness, and memberships are given for the 17985 galaxies observed as part of the OmegaWINGS survey of local clusters of galaxies over 1 square degree. Redshifts have been measured using both absorption and emission lines features. The sample magnitude completeness is 80% at V=20. Thanks to the observing strategy, the radial completeness turned out to be relatively constant (90%) within the AAOmega field of view. The success rate in measuring redshifts is 95%, at all radii. Cluster members are flagged 1 or 2, depending on the cluster structure/secondary structure, and 0 if they are not cluster members. (1 data file)
The evolution of early-type galaxies in clusters from z~ 0.8 to z~ 0: the ellipticity distribution and the morphological mix
We present the ellipticity distribution and its evolution for early-type
galaxies in clusters from z~0.8 to z~0, based on the WIde-field Nearby
Galaxy-cluster Survey (WINGS)(0.04<z<0.07), and the ESO Distant Cluster Survey
(EDisCS)(0.4<z<0.8). We first investigate a mass limited sample and we find
that, above a fixed mass limit, the ellipticity distribution of early-types
noticeably evolves with redshift. In the local Universe there are
proportionally more galaxies with higher ellipticity, hence flatter, than in
distant clusters. This evolution is due partly to the change of the mass
distribution and mainly to the change of the morphological mix with z (among
the early types, the fraction of ellipticals goes from ~70% at high to ~40% at
low-z). Analyzing separately the ellipticity distribution of the different
morphological types, we find no evolution both for ellipticals and S0s.
However, for ellipticals a change with redshift in the median value of the
distributions is detected. This is due to a larger population of very round
(e<0.05) elliptical galaxies at low-z. To compare our finding to previous
studies, we also assemble a magnitude-"delimited" sample that consists of
early-type galaxies on the red sequence with -19.3>M_B+1.208z>-21. Analyzing
this sample, we do not recover exactly the same results of the mass-limited
sample. Hence the selection criteria are crucial to characterize the galaxy
properties: the choice of the magnitude-delimited sample implies the loss of
many less massive galaxies and so it biases the final results. Moreover,
although we are adopting the same selection criteria, our results in the
magnitude-delimited sample are also not in agreement with those of Holden et
al.(2009). This is due to the fact that our and their low-z samples have a
different magnitude distribution because the Holden et al.(2009) sample suffers
from incompleteness at faint magnitudes.Comment: 19 figures and 9 tables, MNRAS in pres
âHot standardsâ for the thermoacidophilic archaeon Sulfolobus solfataricus
Within the archaea, the thermoacidophilic crenarchaeote Sulfolobus solfataricus has become an important model organism for physiology and biochemistry, comparative and functional genomics, as well as, more recently also for systems biology approaches. Within the Sulfolobus Systems Biology (âSulfoSYSâ)-project the effect of changing growth temperatures on a metabolic network is investigated at the systems level by integrating genomic, transcriptomic, proteomic, metabolomic and enzymatic information for production of a silicon cell-model. The network under investigation is the central carbohydrate metabolism. The generation of high-quality quantitative data, which is critical for the investigation of biological systems and the successful integration of the different datasets, derived for example from high-throughput approaches (e.g., transcriptome or proteome analyses), requires the application and compliance of uniform standard protocols, e.g., for growth and handling of the organism as well as the ââomicsâ approaches. Here, we report on the establishment and implementation of standard operating procedures for the different wet-lab and in silico techniques that are applied within the SulfoSYS-project and that we believe can be useful for future projects on Sulfolobus or (hyper)thermophiles in general. Beside established techniques, it includes new methodologies like strain surveillance, the improved identification of membrane proteins and the application of crenarchaeal metabolomics
- âŠ