MUSE discovers perpendicular arcs in the inner filament of Cen A

Evidence of AGN interaction with the IGM is observed in some galaxies and many cool core clusters. Radio jets are suspected to dig large cavities into the surrounding gas. In most cases, very large optical filaments are seen around the central galaxy. The origin of these filaments is still not understood. Star-forming regions are sometimes observed inside the filaments and are interpreted as evidence of positive feedback. Cen A is a nearby galaxy with huge optical filaments aligned with the AGN radio-jet direction. We searched for line ratio variations along the filaments, kinematic evidence of shock-broadend line widths, and large-scale dynamical structures. We observed a 1'x1' region around the inner filament of Cen A with MUSE on the VLT during Science Verification. The brightest lines detected are the Halpha, [NII], [OIII] and [SII]. MUSE shows that the filaments are made of clumpy structures inside a more diffuse medium aligned with the radio-jet axis. We find evidence of shocked shells surrounding the star-forming clumps from the line profiles, suggesting that the star formation is induced by shocks. The clump line ratios are best explained by a composite of shocks and star formation illuminated by a radiation cone from the AGN. We also report a previously undetected large arc-like structure: three streams running perpendicular to the main filament; they are kinematically, morphologically, and excitationally distinct. The clear difference in the excitation of the arcs and clumps suggests that the arcs are very likely located outside of the radiation cone and match the position of the filament only in projection. The three arcs are most consistent with neutral material swept along by a backflow of the jet plasma from the AGN outburst that is ionised through a diffuse radiation field with a low-ionisation parameter that continues to excite gas away from the radiation cone.Comment: 14 Pages (4 paper, 10 appendices), 12 Figures (3 paper, 9 appendicies). Accepted for publication by A&

CO(2-1) large scale mapping of the Perseus cluster core with HERA

Cold molecular gas has recently been found is several cooling flow clusters cores with single dish telescopes. High spatial resolution imaging of some of these clusters then revealed the peculiar morphology and dynamics of the CO emission lines, pointing out a perturbed very cold component in the cluster centers. We report here the observations of NGC 1275, in the Perseus cluster of galaxies. This object is the strongest cooling flow emitter in the millimeter. The 9 dual polarization pixels of the HERA focal plane array, installed on the 30m telescope, enabled to image the large scale emission of the cold molecular gas which is found to follow the very peculiar Halpha filamentary structure around the central galaxy. We discuss here this association and the non-rotating dynamics of the cold gas that argue for a cooling flow origin of the molecular component.Comment: 2 pages, 1 figure, to be published in SF2A-2005, to be published by EdP-Sciences, F. Casoli, T. Contini, J-M. Hameury & L. Pagani (eds

Star formation efficiency along the radio jet in Centaurus A

Centaurus A is the most nearby powerful AGN, widely studied at all wavelengths. Molecular gas has been found in the halo at a distance of ~20 kpc from the galaxy centre, associated with HI shells. The molecular gas lies inside some IR and UV bright star-forming filaments that have recently been observed in the direction of the radio jets. These archival data show that there is dust and very weak star formation on scales of hundreds of parsecs. On top of analysing combined archival data, we have performed searches of HCN(1-0) and HCO+(1-0) emission with ATCA at the interaction of the northern filaments and the HI shell of Cen A. Measuring the dense gas is another indicator of star formation efficiency inside the filaments. However, we only derived upper limits of 1.6x10^3 K.km/s.pc^2 at 3 sigma in the synthesised beam of 3.1". We also compared the CO masses with the SFR estimates in order to measure a star formation efficiency. Using a standard conversion factor leads to long depletion times (7 Gyr). We then corrected the mass estimates from metallicity effect by using gas-to-dust mass ratio as a proxy. From MUSE data, we estimated the metallicity spread (0.4-0.8 Zsun) in the filament, corresponding to gas-to-dust ratios of ~200-400. The CO/H2 conversion ratio is corrected for low metallicity by a factor between 1.4 and 3.2. Such a low-metallicity correction leads to even more massive clouds with higher depletion times (16 Gyr). We finally present ALMA observations that detect 3 unresolved CO(2-1) clumps of siz

Dependence of DNA persistence length on ionic strength of solutions with monovalent and divalent salts: a joint theory-experiment study

Using high-throughput Tethered Particle Motion single molecule experiments, the double-stranded DNA persistence length, $L_p$, is measured in solutions with Na$^+$ and Mg$^{2+}$ ions of various ionic strengths, $I$. Several theoretical equations for $L_p(I)$ are fitted to the experimental data, but no decisive theory is found which fits all the $L_p$ values for the two ion valencies. Properly extracted from the particle trajectory using simulations, $L_p$ varies from 30~nm to 55~nm, and is compared to previous experimental results. For the Na$^+$ only case, $L_p$ is an increasing concave function of $I^{-1}$, well fitted by Manning's electrostatic stretching approach, but not by classical Odjik-Skolnick-Fixman theories with or without counter-ion condensation. With added Mg$^{2+}$ ions, $L_p$ shows a marked decrease at low $I$, interpreted as an ion-ion correlation effect, with an almost linear law in $I^{-1}$, fitted by a proposed variational approach

Inefficient jet-induced star formation in Centaurus A:High resolution ALMA observations of the northern filaments

NGC 5128 is one of the best targets to study AGN-feedback in the local Universe. At 13.5 kpc from the galaxy, optical filaments with recent star formation lie along the radio-jet direction. It is a testbed region for positive feedback (jet-induced star formation). APEX revealed strong CO emission in star-forming regions but also in regions with no detected tracers of star formation. When observed, star formation appears to be inefficient compared to the Kennicutt-Schmidt relation. We used ALMA to map the 12CO(1-0) emission all along the filaments at 1.3"~ 23.8 pc resolution. The CO emission is clumpy and distributed in two main structures: (i) the Horseshoe complex, outside the HI cloud, where gas is mostly excited by shocks and no star formation is observed; (ii) the Vertical filament, at the edge of the HI shell, which is a region of moderate star formation. We identified 140 molecular clouds. A statistical study reveals that they have very similar physical properties that in the inner Milky Way. However, the range of radius available with the present observations does not enable to investigate whether the clouds follow the Larson relation or not. The large virial parameter of the clouds suggests that gravity is not dominant. Finally, the total energy injection in the filaments is of the same order as in the inner part of the Milky Way. The strong CO emission detected in the filaments is an indication that the energy injected by the jet acts positively in the formation of dense molecular gas. The relatively high virial parameter of the molecular clouds suggests that the injected kinetic energy is too strong for star formation to be efficient. This is particularly the case in the Horseshoe complex where the virial parameter is the largest and where strong CO is detected with no associated star formation. This is the first evidence of inefficient AGN positive feedback

Using US Artificial Intelligence to Fight Human Trafficking in Europe

editorial reviewedHuman trafficking is keeping pace with new technologies, but so is its repression. Nowadays, artificial intelligence (AI) systems support the daily work of law enforcement authorities in detecting and investigating trafficking schemes. These systems were developed, and are used primarily, in the United States of America (US). As the fight against human trafficking is a worldwide priority, they are often exported from the US or replicated. Yet, so far, little research has been done to examine how (US) policies and values might be embedded in these specific systems. This article argues that the spread of US tools using artificial intelligence to combat human trafficking hinders the autonomy of foreign States. Particularly in the European context, these tools might challenge national criminal sovereignty as well as Europe’s digital sovereignty. The article highlights the US policies surrounding human trafficking that are embedded in these AI systems (legal definition, political priorities and decisions) and the lack of adequate consideration of existing European standards. These are meant to protect human rights while developing and using AI systems, i.e. the protection of personal data and control over technical standards

ESTUDIO COMPARADO HISPANO-FRANCÉS: LAS DILIGENCIAS DE INVESTIGACIÓN TECNOLÓGICAS FRENTE A LA JURISPRUDENCIA DEL TRIBUNAL EUROPEO DE DERECHOS HUMANOS

Este estudio propone analizar de manera sistemática la regulación de las diligencias tecnológicas en España y Francia. Como países vecinos que cooperan regularmente a nivel policial y judicial, el derecho comparado permite fomentar una buena mutua comprensión entre ambos sistemas, además de poner de manifiesto similitudes, diferencia, buenas prácticas y desafíos de estos mismos. En materia de diligencias tecnológicas, las operaciones consideradas por ambas legislaciones son de suma equivalencia, ya que se acoplan en gran mayoría al estado actual de las técnicas. Los conceptos españoles se encuentran también en la legislación francesa, aunque pueden diferir en su alcance técnico o legislativos. Además, ambos países deben de conformarse con la protección supranacional de los derechos fundamentales, derivada del convenio europeo de derechos humanos. En base a la protección de la vida privada, el TEDH fue desarrollando una amplia jurisprudencia en cuanto a la regulación de las diligencias tecnológicas. Aunque los regímenes de ambos países se conforman en su globalidad a los criterios fijados por el TEDH, cabe mencionar que ninguna de las diligencias está exenta de críticas frente a este marco jurídico

Blanchiment de la traite des êtres humains : réflexions générales sur la complémentarité des deux approches

editorial reviewe