173 research outputs found
GASP XVIII: Star formation quenching due to AGN feedback in the central region of a jellyfish galaxy
We report evidence for star formation quenching in the central 8.6 kpc region
of the jellyfish galaxy JO201 which hosts an active galactic nucleus, while
undergoing strong ram pressure stripping. The ultraviolet imaging data of the
galaxy disk reveal a region with reduced flux around the center of the galaxy
and a horse shoe shaped region with enhanced flux in the outer disk. The
characterization of the ionization regions based on emission line diagnostic
diagrams shows that the region of reduced flux seen in the ultraviolet is
within the AGN-dominated area. The CO J map of the galaxy disk reveals
a cavity in the central region. The image of the galaxy disk at redder
wavelengths (9050-9250 \overset{\lower.5em\circ}{\mathrm{A}}) reveals the
presence of a stellar bar. The star formation rate map of the galaxy disk shows
that the star formation suppression in the cavity occurred in the last few
10 yr. We present several lines of evidence supporting the scenario that
suppression of star formation in the central region of the disk is most likely
due to the feedback from the AGN. The observations reported here make JO201 a
unique case of AGN feedback and environmental effects suppressing star
formation in a spiral galaxy.Comment: Author's accepted manuscrip
GASP II. A MUSE view of extreme ram-pressure stripping along the line of sight: kinematics of the jellyfish galaxy JO201
This paper presents a spatially-resolved kinematic study of the jellyfish
galaxy JO201, one of the most spectacular cases of ram-pressure stripping (RPS)
in the GASP (GAs Stripping Phenomena in Galaxies with MUSE) survey. By studying
the environment of JO201, we find that it is moving through the dense
intra-cluster medium of Abell 85 at supersonic speeds along our line of sight,
and that it is likely accompanied by a small group of galaxies. Given the
density of the intra-cluster medium and the galaxy's mass, projected position
and velocity within the cluster, we estimate that JO201 must so far have lost
~50% of its gas during infall via RPS. The MUSE data indeed reveal a smooth
stellar disk, accompanied by large projected tails of ionised (Halpha) gas,
composed of kinematically cold (velocity dispersion <40km/s) star-forming knots
and very warm (>100km/s) diffuse emission which extend out to at least ~50 kpc
from the galaxy centre. The ionised Halpha-emitting gas in the disk rotates
with the stars out to ~6 kpc but in the disk outskirts becomes increasingly
redshifted with respect to the (undisturbed) stellar disk. The observed
disturbances are consistent with the presence of gas trailing behind the
stellar component, resulting from intense face-on RPS happening along the line
of sight. Our kinematic analysis is consistent with the estimated fraction of
lost gas, and reveals that stripping of the disk happens outside-in, causing
shock heating and gas compression in the stripped tails.Comment: ApJ, revised version after referee comments, 15 pages, 16 figures.
The interactive version of Figure 9 can be viewed at
web.oapd.inaf.it/gasp/publications.htm
GASP. VII. Gas accretion onto an isolated galaxy
Theoretically, inflowing filaments of gas are one of the main causes of
growth for a galaxy. Nonetheless, observationally, probing ongoing gas
accretion is challenging. As part of the Gas Stripping Phenomena in galaxies
with MUSE (GASP) program, we present the analysis of a spiral galaxy at
z=0.04648 whose characteristics indeed are consistent with a scenario in which
gas accretion plays a major role. The most salient indirect parts of evidence
that support this picture are: 1) The galaxy is isolated, its position rules
out the mechanisms expected in dense environments. 2) It shows a pronounced
lopsidedness extending toward West. According to the spatially resolved star
formation history, this component was formed <6x10^8 yr ago. 3) It has many
large and elongated HII regions that are indication of a fragmentation due to
disk instability. 4) The stellar and gas kinematics are quite symmetric around
the same axis, but in the gas the locus of negative velocities shows a
convexity toward East, as if new gas has been infalling with different
orientation and velocity. 5) The metallicity distribution is inhomogeneous and
shows exceptionally steep gradients from the center toward the outskirts,
especially in the South-West side. 6) The luminosity weighted age is generally
low (~8 Gyr) and particularly low (<7 Gyr) along a trail crossing the galaxy
from South-West toward North. It might trace the path of the accreted gas.
These findings point to an inflow of gas probably proceeding from the
South-West side of the galaxy.Comment: 22 pages, 18 figure
Surgical management of life threatening events caused by intermittent aortic insufficiency in a native valve: case report
We describe a case of a patient admitted with apparent life threatening events characterized by hypotension and bradycardia. The patient was ultimately found to have intermittent severe aortic insufficiency. Upon surgical exploration, abnormalities were discovered in the aortic valve, which had a small left coronary cusp with absence of the nodulus of Arantius. Following surgical repair of the valve, aimed at preventing the small cusp from becoming stuck in the open position, the patient has remained episode free for over one year
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
GASP XXXIV: Unfolding the thermal side of ram pressure stripping in the jellyfish galaxy JO201
X-ray studies of jellyfish galaxies play a crucial role in understanding the
interactions between the interstellar medium (ISM) and the intracluster medium
(ICM). In this paper, we focused on the jellyfish galaxy JO201. By combining
archival Chandra observations, MUSE H cubes, and maps of the emission
fraction of the diffuse ionised gas, we investigated both its high energy
spectral properties and the spatial correlation between its X-ray and optical
emissions. The X-ray emission of JO201 is provided by both the Compton thick
AGN (L=2.710 erg s, not
corrected for intrinsic absorption) and an extended component
(L1.9-4.510 erg
s) produced by a warm plasma (kT1 keV), whose luminosity is
higher than expected from the observed star formation
(L3.8 erg s). The spectral analysis
showed that the X-ray emission is consistent with the thermal cooling of hot
plasma. These properties are similar to the ones found in other jellyfish
galaxies showing extended X-ray emission. A point-to-point analysis revealed
that this X-ray emission closely follows the ISM distribution, whereas CLOUDY
simulations proved that the ionisation triggered by this warm plasma would be
able to reproduce the [OI]/H excess observed in JO201. We conclude that
the galactic X-ray emitting plasma is originated on the surface of the ISM as a
result of the ICM-ISM interplay. This process would entail the cooling and
accretion of the ICM onto the galaxy, which could additionally fuel the star
formation, and the emergence of [OI]/H excess in the optical spectrum.Comment: 21 pages, 6 figures, 5 tables. Manuscript in press in Ap
GASP XXXIV: Unfolding the thermal side of ram pressure stripping in the jellyfish galaxy JO201
X-ray studies of jellyfish galaxies play a crucial role in understanding the interactions between the interstellar medium (ISM) and the intracluster medium (ICM). In this paper, we focused on the jellyfish galaxy JO201. By combining archival Chandra observations, Multi Unit Spectroscopic Explorer Hα cubes, and maps of the emission fraction of the diffuse ionized gas, we investigated both its high-energy spectral properties and the spatial correlation between its X-ray and optical emissions. The X-ray emission of JO201 is provided by both the Compton-thick active galactic nucleus (L0.5X-10keV = 2.7 · 1041 erg s−1, not corrected for intrinsic absorption) and an extended component (L0.5X–10 keV » 1.9–4.5 · 1041 erg s−1) produced by a warm plasma (kT»1 keV), whose luminosity is higher than expected from the observed star formation (LX ~ 3.8 · 1040erg s−1). The spectral analysis showed that the X-ray emission is consistent with the thermal cooling of hot plasma. These properties are similar to the ones found in other jellyfish galaxies showing extended X-ray emission. A point-to-point analysis revealed that this X-ray emission closely follows the ISM distribution, whereas CLOUDY simulations proved that the ionization triggered by this warm plasma would be able to reproduce the [O I]/Hα excess observed in JO201. We conclude that the galactic X-ray emitting plasma originates on the surface of the ISM as a result of the ICM–ISM interplay. This process would entail the cooling and accretion of the ICM onto the galaxy, which could additionally fuel the star formation, and the emergence of [O I]/Hα excess in the optical spectrum
Reciprocity as a foundation of financial economics
This paper argues that the subsistence of the fundamental theorem of contemporary financial mathematics is the ethical concept ‘reciprocity’. The argument is based on identifying an equivalence between the contemporary, and ostensibly ‘value neutral’, Fundamental Theory of Asset Pricing with theories of mathematical probability that emerged in the seventeenth century in the context of the ethical assessment of commercial contracts in a framework of Aristotelian ethics. This observation, the main claim of the paper, is justified on the basis of results from the Ultimatum Game and is analysed within a framework of Pragmatic philosophy. The analysis leads to the explanatory hypothesis that markets are centres of communicative action with reciprocity as a rule of discourse. The purpose of the paper is to reorientate financial economics to emphasise the objectives of cooperation and social cohesion and to this end, we offer specific policy advice
Enhanced gas-liquid mass transfer of an oscillatory constricted-tubular reactor
The mass transfer performance has been tested for gas-liquid flow in a new tubular reactor system, the oscillating mesotube (OMT), which features the oscillatory movement of fluid across a series of smooth constrictions located periodically along the vertical 4.4 mm internal diameter tube. The effect of the fluid oscillations (frequency,f, and center-to-peak amplitude, x(0), in the range of 0-20 s(-1) and 0-3 mm, respectively) on the overall volumetric mass transfer coefficient (k(L)a) has been tested by measuring the oxygen saturation levels with a fiber-optical microprobe (oxygen micro-optrode), and a mathematical model has been produced to describe the oxygen mass transport in the OMT. The oxygen mass transfer rates were about I order of magnitude higher (k(L)a values up to 0.16 s(-1)) than those values reported for gas-liquid contacting in a 50 mm internal diameter oscillatory flow reactor (OFR), for the same peak fluid oscillatory velocity, i.e., 2 pi fx(0). This represents remarkable oxygen transfer efficiencies, especially when considering the very low mean superficial gas velocity involved in this work (0.37 mm s(-1)). The narrower constrictions helped to increase the gas fraction (holdup) by reducing the rise velocity of the bubbles. However, the extent of radial mixing and the detachment of vortex rings from the surface of the periodic constrictions are actually the main causes of bubbles retention and effective gas-liquid contacting and are, thus, responsible for the enhancement of k(L)a in the OMT.N.R. thanks the Portuguese Foundation for Science and Technology (FCT) for financial support of his work (SFRH/BD/6954/2001)
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