MASSIV: Mass Assembly Survey with SINFONI in VVDS - II. Kinematics and close environment classification

(Abridged) Processes driving mass assembly are expected to evolve on different timescales along cosmic time. A transition might happen around z ~ 1 as the cosmic star formation rate starts its decrease. Identifying the dynamical nature of galaxies on a representative sample is necessary to infer and compare the mass assembly mechanisms across cosmic time. We present an analysis of the kinematics properties of 50 galaxies with 0.9 < z < 1.6 from the MASSIV sample observed with SINFONI/VLT with 4.5x10^9 Msun < M < 1.7x10^11 Msun and 6 Msun/yr < SFR < 300 Msun/yr. This is the largest sample with 2D-kinematics in this redshift range. We provide a classification based on kinematics as well as on close galaxy environment. We find that 29% of galaxies are experiencing merging or have close companions that may be gravitationally linked. This is placing a lower limit on the fraction of interacting galaxies. We find that at least 44% of the galaxies display ordered rotation whereas at least 35% are non-rotating objects. All rotators except one are compatible with rotation-dominated (Vmax/sigma > 1) systems. Non-rotating objects are mainly small objects (Re < 4 kpc). Combining our sample with other 3D-spectroscopy samples, we find that the local velocity dispersion of the ionized gas component decreases continuously from z ~ 3 to z = 0. The proportion of disks also seems to be increasing in star-forming galaxies when the redshift decreases. The number of interacting galaxies seems to be at a maximum at z ~ 1.2. These results draw a picture in which cold gas accretion may still be efficient at z ~ 1.2 but in which mergers may play a much more significant role at z ~ 1.2 than at higher redshift. From a dynamical point of view, the redshift range 1 < z < 2 therefore appears as a transition period in the galaxy mass assembly process.Comment: 23 pages (+29 maps pages), 7 figures, language corrections and reference updates included, A&A in pres

Increased expression of endothelial lipase in symptomatic and unstable carotid plaques

The aim of this study was to evaluate endothelial lipase (EL) protein expression in advanced human carotid artery plaques (HCAP) with regard to plaque (in)stability and the incidence of symptoms. HCAP were collected from 66 patients undergoing carotid endarterectomy (CEA). The degree of plaque (in)stability was estimated by ultrasound and histology. In HCAP sections, EL expression was determined by immunostaining and the intensity was assessed on a semi-quantitative scale (low: <25%, high: >25% positive cells). Monocytes and macrophages in adjacent HCAP sections were stained with a CD163 specific antibody. High EL staining was more prevalent in histologically unstable plaques (in 33.3% of fibrous plaques, 50% of ulcerated non-complicated plaques and 79.2% of ulcerated complicated plaques; χ2 test, p = 0.004) and in the symptomatic group (70.8 vs. 42.9% in the asymptomatic group; χ2 test, p = 0.028). The majority of EL immunostaining was found in those HCAP regions exhibiting a strong CD163 immunostaining. EL in HCAP might be a marker and/or promoter of plaque instability and HCAP-related symptomatology

Observations and modelling of a clumpy galaxy at z=1.6: Spectroscopic clues to the origin and evolution of chain galaxies

We investigate the properties of a clump-cluster galaxy at redshift 1.57. The morphology of this galaxy is dominated by eight star-forming clumps in optical observations, and has photometric properties typical of most clump-cluster and chain galaxies. Its complex asymmetrical morphology has led to the suggestion that this system is a group merger of several initially separate proto-galaxies. We performed H_alpha integral field spectroscopy of this system using SINFONI on VLT UT4. These observations reveal a large-scale velocity gradient throughout the system, but with large local kinematic disturbances. Using a numerical model of gas-rich disk fragmentation, we find that clump interactions and migration can account for the observed disturbed rotation. On the other hand, the global rotation would not be expected for a multiply merging system. We further find that this system follows the stellar mass vs. metallicity, star formation rate and size relations expected for a disk at this redshift, and exhibits a disk-like radial metallicity gradient, so that the scenario of internal disk fragmentation is the most likely one. A red and metallic central concentration appears to be a bulge in this proto-spiral clumpy galaxy. A chain galaxy at redshift 2.07 in the same field also shows disk-like rotation. Such systems are likely progenitors of the present-day bright spiral galaxies, forming their exponential disks through clump migration and disruption and fueling their bulges. Our present results show that disturbed morphologies and kinematics are not necessarily signs of galaxy mergers and interactions, and can instead result from the internal evolution of primordial disks.Comment: A&A, accepted. Version with full resolution figures available at http://aramis.obspm.fr/~bournaud/udfr2.pdf -- Animation of clumpy galaxy models available at http://aramis.obspm.fr/~bournaud/cc/cc.htm

DYNAMO - I. A sample of H alpha-luminous galaxies with resolved kinematics

DYNAMO is a multiwavelength, spatially resolved survey of local (z ∼ 0.1) star-forming galaxies designed to study evolution through comparison with samples at z _ 2. Half of the sample has integrated Hα luminosities of >1042 erg s−1, the typical lower limit for resolved spectroscopy at z _ 2. The sample covers a range in stellar mass (109–1011M_) and star formation rate (0.2–100M_ yr−1). In this first paper of a series, we present integral-field spectroscopy of Hα emission for the sample of 67 galaxies. We infer gas fractions in our sample as high as _0.8, higher than typical for local galaxies. Gas fraction correlates with stellarmass in galaxies with star formation rates below 10M_ yr−1, as found by COLDGASS, but galaxies with higher star formation rates have higher than expected gas fractions. There is only a weak correlation, if any, between gas fraction and gas velocity dispersion. Galaxies in the sample visually classified as disc-like are offset from the local stellar mass Tully–Fisher relation to higher circular velocities, but this offset vanishes when both gas and stars are included in the baryonic Tully–Fisher relation. The mean gas velocity dispersion of the sample is_50 km s−1, and V/σ ranges from 2 to 10 for most of the discs, similar to ‘turbulent’ galaxies at high redshift. Half of our sample show disc-like rotation, while ∼20 per cent show no signs of rotation. The division between rotating and non-rotating is approximately equal for the sub-samples with either star formation rates >10M_ yr−1, or specific star formation rates typical of the star formation ‘main sequence’ at z _ 2. Across our whole sample, we find good correlation between the dominance of ‘turbulence’ in galaxy discs (as expressed by V/σ ) and gas fraction as has been predicted for marginally stable Toomre discs. Comparing our sample with many others at low- and high-redshift reveals a correlation between gas velocity dispersion and star formation rate. These findings suggest the DYNAMO discs are excellent candidates for local galaxies similar to turbulent z _ 2 disc galaxies

Aspirin inhibits Chlamydia pneumoniae:Induced nuclear factor-kappa B activation, cytokine expression, and bacterial development in human endothelial cells

Objective-Chlamydia pneumoniae has been associated with atherosclerosis. Infection of vascular endothelial cells with C pneumoniae increases the expression of proatherogenic cytokines mediated by nuclear factor (NF)-kappaB, a transcription factor. The present study was designed to test the effect of aspirin on C pneumoniae-induced NF-kappaB activation, interleukin expression, and bacterial development in cultured human endothelial cells. Methods and Results-Aspirin, its metabolite salicylic acid, and 2 other unrelated NF-kappaB inhibitors showed a strong concentration-dependent inhibitory effect on chlamydial growth, indicated by the reduction of bacterial inclusions and the titer of infectious progeny. Involvement of the transcription factor NF-kappaB was confirmed by electrophoretic mobility shift assay and by transfection experiments with appropriate decoy oligodeoxynucleotides. Attenuation of the C pneumoniae-induced activation of NF-kappaB by aspirin also reduced the secretion of interleukin-6 and interleukin-8, indicating efficient inhibition of NF-kappaB gene expression. Reduction of chlamydial growth was not caused by apoptosis of the host cell, as determined by monitoring characteristic chromatin condensation. Conclusions-These data provide evidence that NF-kappaB-mediated gene activation represents a crucial step in the developmental cycle of C pneumoniae. Aspirin exerts an anti-chlamydial effect that is due to the inhibition of C pneumoniae-induced NF-kappaB activation, which might account for some of the cardioprotective activity of aspirin