Jet-induced star formation in 3C 285 and Minkowski Object

How efficiently star formation proceeds in galaxies is still an open question. Recent studies suggest that AGN can regulate the gas accretion and thus slow down star formation (negative feedback). However, evidence of AGN positive feedback has also been observed in a few radio galaxies (eg. Centaurus A). Here we present CO observations of 3C 285 and Minkowski Object (MO), which are examples of jet-induced star formation. A spot (named 09.6) aligned with the 3C 285 radio jet, at a projected distance of ~70 kpc from the galaxy centre, shows star formation, detected in optical emission. MO is located along the jet of NGC 541 and also shows star formation. To know the distribution of molecular gas along the jets is a way to study the physical processes at play in the AGN interaction with the intergalactic medium. We observed CO lines in 3C 285, NGC 541, 09.6 and MO with the IRAM-30m telescope. In the central galaxies, the spectra present a double-horn profile, typical of a rotation pattern, from which we are able to estimate the molecular gas density profile of the galaxy. The molecular gas appears to be in a compact reservoir. In addition, no kinematic signature of a molecular outflow is detected by the 30m-telescope. Interestingly, 09.6 and MO are not detected in CO. The cold gas mass upper limits are consistent with a star formation induced by the compression of dense ambient material by the jet. The depletion time scales are of the order of and even smaller than what is found in 3C 285, NGC 541 and local spiral galaxies (10^9 yr). The molecular gas surface density in 09.6 follows a Schmidt-Kennicutt law if the emitting region is very compact, while MO is found to have a much higher SFE (very short depletion time). Higher sensitivity and spatial resolution are necessary to detect CO in the spots of star formation, and map the emission in these jet-induced star forming regions.Comment: 9 pages, 10 figures, submitted to A&

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&

The anxiety of the lonely listener

Text on listening originally featured in /seconds. peer reviewed online journal. The radio is not one thing it is multitudes. Radio is not innately anything, but is everything it is, dependent on who is listening. In this sense any radio transmission is truly contingent on the temporal, spatial and psychological (understood as an inner dimension) circumstance of the listener. The radio broadcast, emitting from its unsighted box, gives the room it enters different colours; working with the tones that are already there, stretching them in every direction. Sure, this idea of contingency could be applied to other media too, but nowhere is the multiplicity of production and perception more profuse than in the darkness of radio, where no image preserves our hold an on authentic sense of reality, and thus no sense of non-reality limits the imagination of the listener. The temporal flow of radio is a blind stream, emanating from a faceless, boundary-less place. The association of this transitory stream with a visual actuality is produced in a fleeting action of listening. Radio does not produce a certain object, but incites figments of individual imagination. It does not affirm the surety of a location or object but produces its own reality as a perceptual and individual uncertainty

Sonic memory material as 'pathetic trigger'

Memory, according to Henri Bergson, is gleaned from the present and realises the present perception from its sensory-motor elements through movements towards that which it perceives. The purpose of this article is to propose and debate the deliberate use of such ‘present memory’ in the sonic artwork. The suggestion is that sonic memory material – sounds that are plundered from old recordings – can be collaged into complex sonic works to produce, not a nostalgic experience in the sense of a recognition of the past, but a current production of sonic material in a continually present perception. Such a production strategy employs the affective quality of memory to ‘trigger’ a sensorial engagement in the sense of a ‘pathetic’ engagement understood as an emotional and sentimental involvement with the work. The understanding is that such an emotional engagement involves the listener centrally in the production of the artwork and challenges modernist (visual) art discourses, which evaluate the work from a distance

Hamilton-Jacobi equations for optimal control on multidimensional junctions

We consider continuous-state and continuous-time control problems where the admissible trajectories of the system are constrained to remain on a union of half-planes which share a common straight line. This set will be named a junction. We define a notion of constrained viscosity solution of Hamilton-Jacobi equations on the junction and we propose a comparison principle whose proof is based on arguments from the optimal control theory.Comment: 37 pages and 2 figure

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

Luzernegrünmehl in Futtermischungen mit abgesenktem ME-Gehalt für die ökologische Hühnermast

Organic diets with low energy and amino acid contents were studied (Bellof, et al. 2005) with positive effects on growth and carcass performance of broilers. Alfalfa is moderately rich in protein, pigments and saponins and limited content of energy (AME). This event could benefit the design of low energy diets. Also alfalfa was able to produce healthy broiler meat (low fat and cholesterol) with a special flavour (Ponte et al., 2004). In the conventional production the results are controversial. A trial with 6 % of alfalfa diet found reduced performance of broilers (Tkácová et al., 2011), and a long raising study (56 d) found high and low carcass yield with 17 and 45 g/d of alfalfa intake respectively (Ponte et al., 2004). This fact could be attributed to the different fiber contents of the alfalfas used by the above mentioned authors (25.7 % vs. 21.8 % respectively).The aim of the trial was to study the impact of high levels of alfalfa in low energy diets on production parameters of slow-growing broilers

Effective transmission conditions for Hamilton-Jacobi equations defined on two domains separated by an oscillatory interface

We consider a family of optimal control problems in the plane with dynamics and running costs possibly discontinuous across an oscillatory interface $\Gamma_\epsilon$. The oscillations of the interface have small period and amplitude, both of the order of $\epsilon$, and the interfaces $\Gamma_\epsilon$ tend to a straight line $\Gamma$. We study the asymptotic behavior as $\epsilon\to 0$. We prove that the value function tends to the solution of Hamilton-Jacobi equations in the two half-planes limited by $\Gamma$, with an effective transmission condition on $\Gamma$ keeping track of the oscillations of $\Gamma_\epsilon$

Cosmic Feedback from AGN

Accretion onto the massive black hole at the centre of a galaxy can feed energy and momentum into its surroundings via radiation, winds and jets. Feedback due to radiation pressure can lock the mass of the black hole onto the M-sigma relation, and shape the final stellar bulge of the galaxy. Feedback due to the kinetic power of jets can prevent massive galaxies greatly increasing their stellar mass, by heating gas which would otherwise cool radiatively. The mechanisms involved in cosmic feedback are discussed and illustrated with observations.Comment: 9 pages, 13 figures, Proceedings IAU Symposium 267, Co-Evolution of Central Black Holes and Galaxie