512 research outputs found
GASP. XVI. Does cosmic web enhancement turn on star formation in galaxies?
Galaxy filaments are a peculiar environment, and their impact on the galaxy
properties is still controversial. Exploiting the data from the GAs Stripping
Phenomena in galaxies with MUSE (GASP), we provide the first characterisation
of the spatially resolved properties of galaxies embedded in filaments in the
local Universe. The four galaxies we focus on show peculiar ionised gas
distributions: Halpha clouds have been observed beyond four times the effective
radius. The gas kinematics, metallicity map and the ratios of emission line
fluxes confirm that they do belong to the galaxy gas disk, the analysis of
their spectra shows that very weak stellar continuum is associated to them.
Similarly, the star formation history and luminosity weighted age maps point to
a recent formation of such clouds. The clouds are powered by star formation,
and are characterised by intermediate values of dust absorption. We hypothesise
a scenario in which the observed features are due to "Cosmic Web Enhancement":
we are most likely witnessing galaxies passing through or flowing within
filaments that assist the gas cooling and increase the extent of the star
formation in the densest regions in the circumgalactic gas. Targeted
simulations are mandatory to better understand this phenomenon.Comment: MNRAS in press, 18 pages, 12 figure
Enhanced star formation in both disks and ram pressure stripped tails of GASP jellyfish galaxies
Exploiting the data from the GAs Stripping Phenomena in galaxies with MUSE
(GASP) program, we compare the integrated Star Formation Rate- Mass relation
(SFR-M_ast) relation of 42 cluster galaxies undergoing ram pressure stripping
("stripping galaxies") to that of 32 field and cluster undisturbed galaxies.
Theoretical predictions have so far led to contradictory conclusions about
whether ram pressure can enhance the star formation in the gas disks and tails
or not and until now a statistically significant observed sample of stripping
galaxies was lacking. We find that stripping galaxies occupy the upper envelope
of the control sample SFR-M_ast relation, showing a systematic enhancement of
the SFR at any given mass. The star formation enhancement occurs in the disk
(0.2 dex), and additional star formation takes place in the tails. Our results
suggest that strong ram pressure stripping events can moderately enhance the
star formation also in the disk prior to gas removal.Comment: ApJL in pres
GASP. XII. The variety of physical processes occurring in a single galaxy group in formation
GAs Stripping Phenomena in galaxies with MUSE (GASP) is a program aimed at
studying gas removal processes in nearby galaxies in different environments. We
present the study of four galaxies that are part of the same group (z= 0.06359)
and highlight the multitude of mechanisms affecting the spatially resolved
properties of the group members. One galaxy is passive and shows a regular
stellar kinematics. The analysis of its star formation history indicates that
the quenching process lasted for a few Gyr and that the star formation declined
throughout the disk in a similar way, consistent with strangulation. Another
galaxy is characterised by a two-component stellar disk with an extended gas
disk that formed a few 10^8 yr ago, most likely as a consequence of gas
accretion. The third member is a spiral galaxy at the edges of the group, but
embedded in a filament. We hypothesise that the compression exerted by the
sparse intergalactic medium on the dense circumgalactic gas switches on star
formation in a number of clouds surrounding the galaxy ("cosmic web
enhancement"). Alternatively, also ram pressure stripping might be effective.
Finally, the fourth galaxy is a spiral with a truncated ionised gas disk and an
undisturbed stellar kinematics. An analytical model of the galaxy's restoring
pressure, and its location and velocity within the cluster, suggest ram
pressure is the most likely physical mechanism in action. This is the first
optical evidence for stripping in groups.Comment: 19 page, 12 figure
Experimental Determination of Momentum-Resolved Electron-Phonon Coupling
We provide a novel experimental method to quantitatively estimate the
electron-phonon coupling and its momentum dependence from resonant inelastic
x-ray scattering (RIXS) spectra based on the detuning of the incident photon
energy away from an absorption resonance. We apply it to the cuprate parent
compound NdBaCuO and find that the electronic coupling to the
oxygen half-breathing phonon mode is strongest at the Brillouin zone boundary,
where it amounts to eV, in agreement with previous studies. In
principle, this method is applicable to any absorption resonance suitable for
RIXS measurements and will help to define the contribution of lattice
vibrations to the peculiar properties of quantum materials.Comment: 6 pages, 3 figure
Fabrication of 3D cell-laden hydrogel microstructures through photo-mold patterning
Native tissues are characterized by spatially organized three-dimensional (3D) microscaled units which functionally define cellsâcells and cellsâextracellular matrix interactions. The ability to engineer biomimetic constructs mimicking these 3D microarchitectures is subject to the control over cell distribution and organization. In the present study we introduce a novel protocol to generate 3D cell laden hydrogel micropatterns with defined size and shape. The method, named photo-mold patterning (PMP), combines hydrogel micromolding within polydimethylsiloxane (PDMS) stamps and photopolymerization through a recently introduced biocompatible ultraviolet (UVA) activated photoinitiator (VA-086). Exploiting PDMS micromolds as geometrical constraints for two methacrylated prepolymers (polyethylene glycol diacrylate and gelatin methacrylate), micrometrically resolved structures were obtained within a 3 min exposure to a low cost and commercially available UVA LED. The PMP was validated both on a continuous cell line (human umbilical vein endothelial cells expressing green fluorescent protein, HUVEC GFP) and on primary human bone marrow stromal cells (BMSCs). HUVEC GFP and BMSCs were exposed to 1.5% w/v VA-086 and UVA light (1 W, 385 nm, distance from sample = 5 cm). Photocrosslinking conditions applied during the PMP did not negatively affect cells viability or specific metabolic activity. Quantitative analyses demonstrated the potentiality of PMP to uniformly embed viable cells within 3D microgels, creating biocompatible and favorable environments for cell proliferation and spreading during a seven days' culture. PMP can thus be considered as a promising and cost effective tool for designing spatially accurate in vitro models and, in perspective, functional constructs
From the South and from the North? â Quilnus marcosi Heiss & Baena and Aradus angularis J. Sahlberg, two flat bug species new for Central Europe (Hemiptera, Heteroptera, Aradidae)
The flat bug fauna of Switzerland is still insufficiently studied. We describe the first records of Aradus angularis J. Sahlberg, 1886 and Quilnus marcosi Heiss & Baena, 2006 (Heteroptera: Aradidae) in Switzerland from a burnt forest area in the canton Valais. These are also the first records for Central Europe. With these new records, the number of Aradidae species recorded in Switzerland increases to 21, and in the canton Valais to 16. A cantonal record list of aradid species in Switzerland and photographs of the two recently new recorded species are provided. The pyrophilous A. angularis shows a disjunct distribution pattern, disconnected from its known distributional range from Fennoscandia to Northeast China, which suggests that the species is a relict of the Ice Age in Central Europe. In contrast, the sub-Mediterranean Q. marcosi seems to have expanded its distributional range to the north-east or has previously gone unnoticed in Switzerland. The host plants of Q. marcosi include Pinus nigra and P. sylvestris
The evolution of galaxy sizes
We present a study of galaxy sizes in the local Universe as a function of
galaxy environment, comparing clusters and the general field. Galaxies with
radii and masses comparable to high-z massive and compact galaxies represent
4.4% of all galaxies more massive than 3 X 10^{10} M_sun in the field. Such
galaxies are 3 times more frequent in clusters than in the field. Most of them
are early-type galaxies with intermediate to old stellar populations. There is
a trend of smaller radii for older luminosity-weighted ages at fixed galaxy
mass. We show the relation between size and luminosity-weighted age for
galaxies of different stellar masses and in different environments. We compare
with high-z data to quantify the evolution of galaxy sizes. We find that, once
the progenitor bias due to the relation between galaxy size and stellar age is
removed, the average amount of size evolution of individual galaxies between
high- and low-z is mild, of the order of a factor 1.6.Comment: to appear in the proceedings of the IAU S295: The intriguing life of
massive galaxies, editors D. Thomas, A. Pasquali & I. Ferrera
GASP IV: A muse view of extreme ram-pressure stripping in the plane of the sky: the case of jellyfish galaxy JO204
In the context of the GAs Stripping Phenomena in galaxies with Muse (GASP)
survey, we present the characterization of JO204, a jellyfish galaxy in A957, a
relatively low-mass cluster with . This galaxy
shows a tail of ionized gas that extends up to 30 kpc from the main body in the
opposite direction of the cluster center. No gas emission is detected in the
galaxy outer disk, suggesting that gas stripping is proceeding outside-in. The
stellar component is distributed as a regular disk galaxy; the stellar
kinematics shows a symmetric rotation curve with a maximum radial velocity of
200km/s out to 20 kpc from the galaxy center. The radial velocity of the gas
component in the central part of the disk follows the distribution of the
stellar component; the gas kinematics in the tail retains the rotation of the
galaxy disk, indicating that JO204 is moving at high speed in the intracluster
medium. Both the emission and radial velocity maps of the gas and stellar
components indicate ram-pressure as the most likely primary mechanism for gas
stripping, as expected given that JO204 is close to the cluster center and it
is likely at the first infall in the cluster. The spatially resolved star
formation history of JO204 provides evidence that the onset of ram-pressure
stripping occurred in the last 500 Myr, quenching the star formation activity
in the outer disk, where the gas has been already completely stripped. Our
conclusions are supported by a set of hydrodynamic simulations.Comment: accepted for publication in Ap
Edge Computing and Communication for Energy-Efficient Earth Surveillance with LEO Satellites
Modern satellites deployed in low Earth orbit (LEO) accommodate processing
payloads that can be exploited for edge computing. Furthermore, by implementing
inter-satellite links, the LEO satellites in a constellation can route the data
end-to-end (E2E). These capabilities can be exploited to greatly improve the
current store-and-forward approaches in Earth surveillance systems. However,
they give rise to an NP-hard problem of joint communication and edge computing
resource management (RM). In this paper, we propose an algorithm that allows
the satellites to select between computing the tasks at the edge or at a cloud
server and to allocate an adequate power for communication. The overall
objective is to minimize the energy consumption at the satellites while
fulfilling specific service E2E latency constraints for the computing tasks.
Experimental results show that our algorithm achieves energy savings of up to
18% when compared to the selected benchmarks with either 1) fixed edge
computing decisions or 2) maximum power allocation.Comment: Submitted to ICC 202
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