An X-ray absorption analysis of the high-velocity system in NGC 1275

We present an X-ray absorption analysis of the high-velocity system (HVS) in NGC 1275 using results from a deep 200 ks Chandra observation. We are able to describe the morphology of the HVS in more detail than ever before. We present an HST image for comparison, and note close correspondence between the deepest X-ray absorption and the optical absorption. A column density map of the HVS shows an average column density NH of 1x10^21 cm^-2 with a range from ~5x10^20 to 5x10^21 cm^-2. From the NH map we calculate a total mass for the absorbing gas in the HVS of (1.32+-0.05)x10^9 solar masses at solar abundance. 75 per cent of the absorbing mass is contained in the four regions of deepest absorption. We examine temperature maps produced by spectral fitting and find no direct evidence for shocked gas in the HVS. Using deprojection methods and the depth of the observed absorption, we are able to put a lower limit on the distance of the HVS from the nucleus of 57 kpc, showing that the HVS is quite separate from the body of NGC 1275.Comment: 6 pages, 5 colour figures, accepted by MNRA

Deep optical observations of the interaction of the SS 433 microquasar jet with the W 50 radio continuum shell

Four mosaics of deep, continuum-subtracted, CCD images have been obtained over the extensive galactic radio continuum shell, W 50, which surrounds the remarkable stellar system SS 433. Two of these mosaics in the Halpha+[N II] and [O III] 5007 A emission lines respectively cover a field of ~2.3 x 2.5 degr^2 which contains all of W 50 but at a low angular resolution of 5 arcsec. The third and fourth mosaics cover the eastern (in [O III] 5007 A) and western (in Halpha+[N II]) filamentary nebulosity respectively but at an angular resolution of 1 arcsec. These observations are supplemented by new low dispersion spectra and longslit, spatially resolved echelle spectra. The [O III] 5007 A images show for the first time the distribution of this emission in both the eastern and western filaments while new Halpha+[N II] emission features are also found in both of these regions. Approaching flows of faintly emitting material from the bright eastern filaments of up 100 km/s in radial velocity are detected. The present observations also suggest that the heliocentric systemic radial velocity of the whole system is 56+-2 km/s. Furthermore, very deep imagery and high resolution spectroscopy of a small part of the northern radio ridge of W 50 has revealed for the first time the very faint optical nebulosity associated with this edge. It is suggested that patchy foreground dust along the ~5 kpc sightline is inhibiting the detection of all of the optical nebulosity associated with W 50. The interaction of the microquasar jets of SS 433 with the W 50 shell is discussed.Comment: 19 pages, 13 figures, 2 tables. Accepted for pubication in MNRA

Theory of the anomalous Hall effect from the Kubo formula and the Dirac equation

A model to treat the anomalous Hall effect is developed. Based on the Kubo formalism and on the Dirac equation, this model allows the simultaneous calculation of the skew-scattering and side-jump contributions to the anomalous Hall conductivity. The continuity and the consistency with the weak-relativistic limit described by the Pauli Hamiltonian is shown. For both approaches, Dirac and Pauli, the Feynman diagrams, which lead to the skew-scattering and the side-jump contributions, are underlined. In order to illustrate this method, we apply it to a particular case: a ferromagnetic bulk compound in the limit of weak-scattering and free-electrons approximation. Explicit expressions for the anomalous Hall conductivity for both skew-scattering and side-jump mechanisms are obtained. Within this model, the recently predicted ''spin Hall effect'' appears naturally

Star Formation in the Outer Filaments of NGC 1275

We present photometry of the outer star clusters in NGC 1275, the brightest galaxy in the Perseus cluster. The observations were taken using the Hubble Space Telescope Advanced Camera for Surveys. We focus on two stellar regions in the south and south-east, far from the nucleus of the low velocity system (~22 kpc). These regions of extended star formation trace the H alpha filaments, drawn out by rising radio bubbles. In both regions bimodal distributions of colour (B-R)_0 against magnitude are apparent, suggesting two populations of star clusters with different ages; most of the H alpha filaments show no detectable star formation. The younger, bluer population is found to be concentrated along the filaments while the older population is dispersed evenly about the galaxy. We construct colour-magnitude diagrams and derive ages of at most 10^8 years for the younger population, a factor of 10 younger than the young population of star clusters in the inner regions of NGC 1275. We conclude that a formation mechanism or event different to that for the young inner population is needed to explain the outer star clusters and suggest that formation from the filaments, triggered by a buoyant radio bubble either rising above or below these filaments, is the most likely mechanism.Comment: Accepted for publication in MNRAS, 14 pages, 14 figures, 3 table

Textural variations in Neogene pelagic carbonate ooze at DSDP Site 593, southern Tasman Sea, and their paleoceanographic implications

Changes in Neogene sediment texture in pelagic carbonate-rich oozes on the Challenger Plateau, southern Tasman Sea, are used to infer changes in depositional paleocurrent velocities. The most obvious record of textural change is in the mud:sand ratio. Increases in the sand content are inferred to indicate a general up-core trend towards increasing winnowing of sediments resulting from increasing flow velocity of Southern Component Intermediate Water (SCIW), the forerunner of Antarctic Intermediate Water. In particular, the intervals c. 19-14.5 Ma, c. 9.5-8 Ma, and after 5 Ma are suggested to be times of increased SCIW velocity and strong sediment winnowing. Within the mud fraction, the fine silt to coarse clay sizes from 15.6 to 2 µm make the greatest contribution to the sediments and are composed of nannofossil plates. During extreme winnowing events it is the fine silt to very coarse clay material (13-3 µm) within this range that is preferentially removed, suggesting the 10 µm cohesive silt boundary reported for siliciclastic sediments does not apply to calcitic skeletal grains. The winnowed sediment comprises coccolithophore placoliths and spheres, represented by a mode at 4-7 µm. Further support for seafloor winnowing is gained from the presence in Hole 593 of a condensed sedimentary section from c. 18 to 14 Ma where the sand content increases to c. 20% of the bulk sample. Associated with the condensed section is a 6 m thick orange unit representing sediments subjected to particularly oxygen-rich, late early to early middle Miocene SCIW. Together these are inferred to indicate increased SCIW velocity resulting in winnowed sediment associated with faster arrival of oxygen-rich surface water subducted to form SCIW. Glacial development of Antarctica has been recorded from many deep-sea sites, with extreme glacials providing the mechanism to increase watermass flow. Miocene glacial zones Mi1b-Mi6 are identified in an associated oxygen isotope record from Hole 593, and correspond with times of particularly invigorated paleocirculation, bottom winnowing, and sediment textural changes

Supersonic water masers in 30 Doradus

We report on extremely high velocity molecular gas, up to -80 km/s relative to the ambient medium, in the giant star-formation complex 30 Doradus in the Large Magellanic Cloud (LMC), as observed in new 22 GHz H2O maser emission spectra obtained with the Mopra radio telescope. The masers may trace the velocities of protostars, and the observed morphology and kinematics indicate that current star formation occurs near the interfaces of colliding stellar-wind blown bubbles. The large space velocities of the protostars and associated gas could result in efficient mixing of the LMC. A similar mechanism in the Milky Way could seed the galactic halo with relatively young stars and gas.Comment: 11 pages plus 1 PS and 1 EPS figure, uses AASTeX preprint style; accepted for publication in Astrophysical Journal Letter

The unprecedented optical outburst of the quasar 3C 454.3. The WEBT campaign of 2004-2005

The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. The maximum brightness detected was R = 12.0, which represents the most luminous quasar state thus far observed (M_B ~ -31.4). In order to follow the emission behaviour of the source in detail, a large multiwavelength campaign was organized by the Whole Earth Blazar Telescope (WEBT). Continuous optical, near-IR and radio monitoring was performed in several bands. ToO pointings by the Chandra and INTEGRAL satellites provided additional information at high energies in May 2005. The historical radio and optical light curves show different behaviours. Until about 2001.0 only moderate variability was present in the optical regime, while prominent and long-lasting radio outbursts were visible at the various radio frequencies, with higher-frequency variations preceding the lower-frequency ones. After that date, the optical activity increased and the radio flux is less variable. This suggests that the optical and radio emissions come from two separate and misaligned jet regions, with the inner optical one acquiring a smaller viewing angle during the 2004-2005 outburst. Moreover, the colour-index behaviour (generally redder-when-brighter) during the outburst suggests the presence of a luminous accretion disc. A huge mm outburst followed the optical one, peaking in June-July 2005. The high-frequency (37-43 GHz) radio flux started to increase in early 2005 and reached a maximum at the end of our observing period (end of September 2005). VLBA observations at 43 GHz during the summer confirm theComment: 7 pages, 4 figures, to be published in A&

Peripheral T cell lymphoma, not otherwise specified: the stuff of genes, dreams and therapies

Peripheral T cell lymphomas (PTCL) account for about 12% of lymphoid tumours worldwide. Almost half show such morphological and molecular variability as to hamper any further classification, and to justify their inclusion in a waste-basket category termed “not otherwise specified (NOS)”. The latter term is used for neoplasms with aggressive presentation, poor response to therapy and dismal prognosis. In contrast to B cell lymphomas, PTCL have been the subject of only a limited number of studies to elucidate their pathobiology and identify novel pharmacological approaches. Herewith, the authors revise the most recent contributions on the subject based on the experience they have gained in the extensive application of microarray technologies. PTCL/NOS are characterised by erratic expression of T cell associated antigens, including CD4 and CD52, which have recently been proposed as targets for ad hoc immunotherapies. PTCL/NOS also show variable Ki-67 marking, with rates >80% heralding a worse prognosis. Gene expression profiling studies have revealed that PTCL/NOS derive from activated T lymphocytes, more often of the CD4+ type, and bear a signature composed of 155 genes and related products that play a pivotal role in cell signalling transduction, proliferation, apoptosis and matrix remodelling. This observation seems to pave the way for the use of innovative drugs such as tyrosine kinase and histone deacetylase inhibitors whose efficacy has been proven in PTCL primary cell cultures. Gene expression profiling also allows better distinction of PTCL/NOS from angioimmunoblastic T cell lymphoma, the latter being characterised by follicular T helper lymphocyte derivation and CXCL13, PD1 and vascular endothelial growth factor expression

Anomalous Hall effect in Fe/Cu bilayers

The scaling of anomalous Hall resistivity on the longitudinal resistivity has been intensively studied in the different magnetic systems, including multilayers and granular films, to examine which mechanism, skew scattering or side-jump, dominates. The basis of the scaling law is that both the resistivities are due to the electron scattering at the imperfections in the materials. By studying of anomalous Hall effect (AHE) in the simple Fe/Cu bilayers, we demonstrate that the measured anomalous Hall effect should not follow the scaling laws derived from skew scattering or side-jump mechanism due to the short-circuit and shunting effects of the non-magnetic layers.Comment: 12 pages, 4 figures; http://www.springerlink.com/content/1718722u75j24587

Faster maturation of selective attention in musically trained children and adolescents : Converging behavioral and event-related potential evidence

Previous work suggests that musical training in childhood is associated with enhanced executive functions. However, it is unknown whether this advantage extends to selective attention-another central aspect of executive control. We recorded a well-established event-related potential (ERP) marker of distraction, the P3a, during an audio-visual task to investigate the maturation of selective attention in musically trained children and adolescents aged 10-17 years and a control group of untrained peers. The task required categorization of visual stimuli, while a sequence of standard sounds and distracting novel sounds were presented in the background. The music group outperformed the control group in the categorization task and the younger children in the music group showed a smaller P3a to the distracting novel sounds than their peers in the control group. Also, a negative response elicited by the novel sounds in the N1/MMN time range (similar to 150-200 ms) was smaller in the music group. These results indicate that the music group was less easily distracted by the task-irrelevant sound stimulation and gated the neural processing of the novel sounds more efficiently than the control group. Furthermore, we replicated our previous finding that, relative to the control group, the musically trained children and adolescents performed faster in standardized tests for inhibition and set shifting. These results provide novel converging behavioral and electrophysiological evidence from a cross-modal paradigm for accelerated maturation of selective attention in musically trained children and adolescents and corroborate the association between musical training and enhanced inhibition and set shifting.Peer reviewe