4,607 research outputs found
Galaxy cluster mergers as triggers for the formation of jellyfish galaxies: case study of the A901/2 system
The A901/2 system is a rare case of galaxy cluster interaction, in which two
galaxy clusters and two smaller groups are seen in route of collision with each
other simultaneously. Within each of the four substructures, several galaxies
with features indicative of jellyfish morphologies have been observed. In this
paper, we propose a hydrodynamic model for the merger as a whole, compatible
with its diffuse X-ray emission, and correlate the gas properties in this model
with the locations of the jellyfish galaxy candidates in the real system. We
find that jellyfish galaxies seem to be preferentially located near a boundary
inside each subcluster where diffuse gas moving along with the subcluster and
diffuse gas from the remainder of the system meet. The velocity change in those
boundaries is such that a factor of up to 1000 increase in the ram
pressure takes place within a few hundred kpc, which could trigger the high
rate of gas loss necessary for a jellyfish morphology to emerge. A theoretical
treatment of ram pressure stripping in the environment of galaxy cluster
mergers has not been presented in the literature so far; we propose that this
could be a common scenario for the formation of jellyfish morphologies in such
systems.Comment: Accepted for publication in MNRAS. 10 pages, 9 figure
Lead-up and manifestation of the Oceanic Anoxic Event 2 at the DSDP Site 398 (Vigo Seamount, NW Iberian offshore): palynological and geochemical insights
Extreme climatic conditions, volcanism, and paleogeographical distribution presumably led to the Oceanic Anoxic Event 2 (OAE 2), one of the most disruptive events for Cretaceous ecosystems. Although the terrestrial response to this issue is barely studied, a turnover within the plant communities seems to be linked to the OAE 2, besides the well-known extinction of several marine groups. In this study, palynological and δ13Corg analyses were combined to research the sediments from DSDP Site 398 (Vigo Seamount) cores 398D-58 to 398D-56 (upper Albian to lower Turonian). The δ13Corg curve exhibits a Carbon Isotopic Excursion (CIE) observed between the interval 948,60 and 947,77 m below seafloor (mbsf), corresponding to the OAE 2. Four palynological assemblages were differentiated, ranging from the uppermost Albian to the lower Turonian. These assemblages comprised diverse marine and terrestrial communities with generally excellent preservation. In addition to previous biostratigraphic works, we present a more detailed chronostratigraphy of DSDP Hole 398D based on palynomorphs. The paleoecological reconstruction reveals the significant changes during the OAE 2 period: a decrease in the diversity and abundance of dinoflagellate cysts and a shift to angiosperm-dominated terrestrial communities (i.e., Normapolles) which, unlike other sites, occurs prior to the maximum values of δ13C
The impact of environmental effects on AGN: a decline in the incidence of ionized outflows
AGN have been generally considered to be less frequent in denser environments
due to the lower number of galaxy-galaxy interactions and/or the removal of
their gas-rich reservoirs by the dense intergalactic medium. However, recent
observational and theoretical works suggest that the effect of ram-pressure
stripping might reduce the angular momentum of their gas, causing it to infall
towards the super massive black hole (SMBH) at their centre, activating the AGN
phase. In this work we explore the connection between environment and nuclear
activity by evaluating the variation in the incidence of ionized outflows in
AGN across different environments. We select a sample of optical AGN
from the Sloan Digital Sky Survey Data Release 13 that we match with the group
catalogue from Lim et al. 2017. We further probe their environment through the
projected distance to the central galaxy of the group/cluster and the projected
surface density to the 5th neighbour (). We find that at lower masses
(M), the fraction of ionized outflows is significantly
lower in satellite (%) than in isolated (%) AGN. The fraction of
outflows in all satellite AGN decreases towards closer distances to the
central, whereas only the lower-mass ones display a significant decline with
. Although this study does not include AGN in the densest regions of
galaxy clusters, our findings suggest that AGN in dense environments accrete
less gas than those in the field potentially due to the removal of the gas
reservoirs via stripping or starvation, consistent with a negative connection
between environment and AGN activity. We propose that the observed change in
the incidence of outflows towards denser regions of groups and clusters could
contribute to the higher gas metallicities of cluster galaxies compared to
field ones, especially at lower masses.Comment: 9 pages, 6 figures, Accepted for publication in Astronomy and
Astrophysic
Wavelength self-calibration and sky subtraction for Fabry–Pérot interferometers: applications to OSIRIS
We describe techniques concerning wavelength calibration and sky subtraction to maximize the scientific utility of data from tunable filter instruments. While we specifically address data from the Optical System for Imaging and low Resolution Integrated Spectroscopy instrument (OSIRIS) on the 10.4-m Gran Telescopio Canarias telescope, our discussion is generalizable to data from other tunable filter instruments. A key aspect of our methodology is a coordinate transformation to polar coordinates, which simplifies matters when the tunable filter data are circularly symmetric around the optical centre. First, we present a method for rectifying inaccuracies in the wavelength calibration using OH sky emission rings. Using this technique, we improve the absolute wavelength calibration from an accuracy of ∼5 to 1 Å, equivalent to ∼7 per cent of our instrumental resolution, for 95 per cent of our data. Then, we discuss a new way to estimate the background sky emission by median filtering in polar coordinates. This method suppresses contributions to the sky background from the outer envelopes of distant galaxies, maximizing the fluxes of sources measured in the corresponding sky-subtracted images. We demonstrate for data tuned to a central wavelength of 7615 Å that galaxy fluxes in the new sky-subtracted image are ∼37 per cent higher, versus a sky-subtracted image from existing methods for OSIRIS tunable filter data
Exploring orbital-charge conversion mediated by interfaces with copper through spin-orbital pumping
We investigated how different materials affect the orbital-charge conversion
in heterostructures with the naturally oxidized cooper capping layer. When we
added a thin layer of onto yttrium iron garnet stacks, we
observed a significant reduction in the charge current signal measured by means
the spin pumping effect technique. This finding contrasts with the results of a
prior study conducted on YIG/Pt/CuOx, which reported the opposite effect. On
the other hand, when we added the same layer to
structures, there was not much change in the spin pumping signal. This occurred
because Ti does not generate much orbital current at the interface,
unlike Pt, due to its weaker spin-orbit coupling. Interestingly, when we added
the layer to structures, the spin pumping
signal increased. However, in structures,
the signal decreased. Finally, we delve into a theoretical analysis of the spin
(orbital) Hall effect in YIG/Heavy-metal systems. These findings have the
potential to advance research in the innovative field of orbitronics and
contribute to the development of new technologies based on spin-orbital
conversion.Comment: 21 pages, 6 figures
Environmental monitoring platform based on a heterogeneous wireless sensor network
Abstract – In museums, to conserve the existing artwork is a
vital issue. To achieve this purpose, it is fundamental to monitor
its environment, either in storage or exhibition rooms. The
deployment of a Wireless Sensor Network (WSN) can help to
implement these measurements continuously, in a real-time basis,
and in a much easier and cheaper way than when using
traditional measuring equipments and procedures. This is the
main objective of the WISE-MUSE project, which uses WSNs for
monitoring and automatically controlling museums’ environment
and structural health. In this paper, the implementation and the
final results of the WISE-MUSE project, which was carried out
in two particular museums located in Madeira Island, the
Museum of Contemporary Art of Funchal and the Madeira
Whale Museum, are described. Among other important
contributions, we emphasize the development of new
environmental monitoring and controlling devices, an emergency
doors’ controlling device, as well as the development of three new
tools for monitoring, visualizing and managing WSNs, which
bring some considerable advantages when compared with other
commercially available solutions.info:eu-repo/semantics/publishedVersio
Monitoring bubble production in a seagrass meadow using a source of opportunity
Under high irradiance, the photosynthetic activity of dense seagrass meadows saturates the water forming oxygen bubbles. The diel cycle of bubble production peaks at mid-day, following light intensity pattern. It is well known that bubbles strongly affect the acoustic propagation, increasing signal attenuation and decreasing the effective water sound speed, noticeable at low frequencies. Thus, the diurnal variability of bubbles may show an interference pattern in the spectrograms of low frequency acoustic signals. In an experiment conducted in July 2016 at the Aquaculture Research Station of the Portuguese Institute for the Sea and Atmosphere in Olhão, Portugal, the spectrograms of low frequency (<20kHz) broadband noise produced by water pumps in a pond of 0.48ha covered by the seagrass Cymodocea nodosa showed interference patterns that can be ascribed to the variability of the sound speed in the water. Preliminary analysis suggests that the daily cycle of bubble concentration can be inferred from these interference patterns.info:eu-repo/semantics/publishedVersio
Mouse p53-deficient cancer models as platforms for obtaining genomic predictors of human cancer clinical outcomes
Mutations in the TP53 gene are very common in human cancers, and are associated with poor clinical outcome. Transgenic mouse models lacking the Trp53 gene or that express mutant Trp53 transgenes produce tumours with malignant features in many organs. We previously showed the transcriptome of a p53-deficient mouse skin carcinoma model to be similar to those of human cancers with TP53 mutations and associated with poor clinical outcomes. This report shows that much of the 682-gene signature of this murine skin carcinoma transcriptome is also present in breast and lung cancer mouse models in which p53 is inhibited. Further, we report validated gene-expression-based tests for predicting the clinical outcome of human breast and lung adenocarcinoma. It was found that human patients with cancer could be stratified based on the similarity of their transcriptome with the mouse skin carcinoma 682-gene signature. The results also provide new targets for the treatment of p53-defective tumours
The multi-thermal chromosphere: inversions of ALMA and IRIS data
Numerical simulations of the solar chromosphere predict a diverse thermal
structure with both hot and cool regions. Observations of plage regions in
particular feature broader and brighter chromospheric lines, which suggest that
they are formed in hotter and denser conditions than in the quiet-Sun, but also
implies a non-thermal component whose source is unclear. We revisit the problem
of the stratification of temperature and microturbulence in plage now adding
millimeter continuum observations provided by ALMA to inversions of
near-ultraviolet IRIS spectra as a powerful new diagnostic to disentangle the
two parameters. We fit cool chromospheric holes and track the fast evolution of
compact mm brightenings in the plage region. We use the STiC non-LTE inversion
code to simultaneously fit real ultraviolet and millimeter spectra in order to
infer the thermodynamic parameters of the plasma. We confirm the anticipated
constraining potential of ALMA in non-LTE inversions of the solar chromosphere.
We find significant differences between the inversion results of IRIS data
alone compared to the results of a combination with the mm data: the IRIS+ALMA
inversions have increased contrast and temperature range, and tend to favor
lower values of microturbulence in the chromosphere of plage. The average
brightness temperature of the plage region at 1.25 mm is 8500 K, but the ALMA
maps also show much cooler ( K) and hotter ( K) evolving
features partially seen in other diagnostics. To explain the former, the
inversions require the existence of localized, low temperature regions in the
chromosphere where molecules such as CO could form. The hot features could
sustain such high temperatures due to non-equilibrium hydrogen ionization
effects in a shocked chromosphere - a scenario that is supported by
low-frequency shock wave patterns found in the MgII lines probed by IRIS.Comment: 17 pages, 12 figures; accepted in A&A (added references, corrected
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