Optical and near-IR spectroscopy of candidate red galaxies in two z~2.5 proto-clusters

We present a spectroscopic campaign to follow-up red colour-selected candidate massive galaxies in two high redshift proto-clusters surrounding radio galaxies. We observed a total of 57 galaxies in the field of MRC0943-242 (z=2.93) and 33 in the field of PKS1138-262 (z=2.16) with a mix of optical and near-infrared multi-object spectroscopy. We confirm two red galaxies in the field of PKS1138-262 at the redshift of the radio galaxy. Based on an analysis of their spectral energy distributions, and their derived star formation rates from the H-alpha and 24um flux, one object belongs to the class of dust-obscured star-forming red galaxies, while the other is evolved with little ongoing star formation. This result represents the first red and mainly passively evolving galaxy to be confirmed as companion galaxies in a z>2 proto-cluster. Both red galaxies in PKS1138-262 are massive, of the order of 4-6x10^11 M_Sol. They lie along a Colour-Magnitude relation which implies that they formed the bulk of their stellar population around z=4. In the MRC0943-242 field we find no red galaxies at the redshift of the radio galaxy but we do confirm the effectiveness of our JHK_s selection of galaxies at 2.3<z<3.1, finding that 10 out of 18 (56%) of JHK_s-selected galaxies whose redshifts could be measured fall within this redshift range. We also serendipitously identify an interesting foreground structure of 6 galaxies at z=2.6 in the field of MRC0943-242. This may be a proto-cluster itself, but complicates any interpretation of the red sequence build-up in MRC0943-242 until more redshifts can be measured.Comment: 17 pages, 14 figures, accepted for publication in Astronomy and Astrophysic

The retinoid agonist Tazarotene promotes angiogenesis and wound healing

Therapeutic angiogenesis is a major goal ofregenerative medicine, but no clinically approved small molecule exists that enhancesnew blood vessel formation. Here we show, using a phenotype-driven high-content imaging screen of an annotated chemical library of 1280 bioactive small molecules, that the retinoid agonist Tazarotene, enhances in vitroangiogenesis, promoting branching morphogenesis, and tubule remodeling. The pro-angiogenic phenotype is mediated by Retinoic Acid Receptor (RAR) but not Retinoic X Receptor(RXR) activation, and is characterized by secretion of the pro-angiogenic factors Hepatocyte Growth Factor (HGF), Vascular Endothelial Growth Factor (VEGFA), Plasminogen Activator, Urokinase (PLAU) and Placental Growth Factor (PGF), and reduced secretion of the antiangiogenic factor Pentraxin-3 (PTX3) from adjacent fibroblasts. In vivo, Tazarotene enhanced the growth of mature and functional microvessels in Matrigel implants and wound healing models, and increased blood flow. Notably, in ear punch wound healing model, Tazarotene promoted tissue repair characterized by rapid ear punch closure with normal-appearing skin containing new hair follicles, and maturing collagen fibers. Our study suggests that Tazarotene, an FDA-approved small molecule, could be potentially exploited for therapeutic applications in neovascularization and wound healing

Establishment of cell-cell junctions depends on the oligomeric states of VE-cadherin.: Oligomerization of VE-cadherin at cell surface

International audienceSpecifically expressed at intercellular adherens junctions of endothelial cells, VE-cadherin is a receptor that exhibits particular self-association properties. Indeed, in vitro studies demonstrated that the extracellular part of VE-cadherin elaborates Ca(++)-dependent hexameric structures. We hypothesized that this assembly could be at the basis of a new cadherin-mediated cell-cell adhesion mechanism. To verify this assumption, we first demonstrated that VE-cadherin can elaborate hexamers at the cell surface of confluent endothelial cells. Second, mutations were introduced within the extracellular part of VE-cadherin to destabilize the hexamer. Following an in vitro screening, three mutants were selected, among which, one is able to elaborate only dimers. The selected mutations were expressed as C-terminal green fluorescent protein fusions in CHO cells. Despite their capacity to elaborate nascent cell-cell contacts, the mutants seem to be rapidly degraded and/or internalized. Altogether, our results suggest that the formation of VE-cadherin hexamers protects this receptor and might allow the elaboration of mature endothelial cell-cell junctions

A peculiar galaxy appears at redshift 11: properties of a moderate redshift interloper

Laporte et al. (2011) reported a very high redshift galaxy candidate: a lensed J-band dropout (A2667-J1). J1 has a photometric redshift of z=9.6-12, the probability density function for which permits no low or intermediate z solution. We here report new spectroscopic observations of this galaxy with VLT/XShooter, which show clear [OIII]5007AA, Ly-alpha, H-alpha, and H-beta emission and place the galaxy firmly at z=2.082. The oxygen lines contribute only ~25% to the H-band flux, and do not significantly affect the dropout selection of J1. After correcting the broadband fluxes for line emission, we identify two roughly equally plausible natures for A2667-J1: either it is young heavily reddened starburst, or a maximally old system with a very pronounced 4000AA break, upon which a minor secondary burst of star formation is superimposed. Fits show that to make a 3 sigma detection of this object in the B-band (V-band), imaging of depth AB=30.2 (29.5) would be required - despite the relatively bright NIR magnitude, we would need optical data of equivalent depth to the Hubble Ultra Deep Field to rule out the mid-z solution on purely photometric grounds. Assuming that this stellar population can be scaled to the NIR magnitudes of recent HST/WFC3 IR-selected galaxies, we conclude that infeasibly deep optical data AB~32 would be required for the same level of security. There is a population of galaxies at z~2 with continuum colours alone that mimic those of our z=7-12 candidates.Comment: Accepted by Monthly Notices. 5 pages, 2 figure

The Mid-Infrared Environments of High-Redshift Radio Galaxies

Taking advantage of the impressive sensitivity of Spitzer to detect massive galaxies at high redshift, we study the mid-infrared environments of powerful, high-redshift radio galaxies at 1.2<z<3. Galaxy cluster member candidates were isolated using a single Spitzer/IRAC mid-infrared color criterion, [3.6]-[4.5]>-0.1 (AB), in the fields of 48 radio galaxies at 1.2<z<3. This simple IRAC color selection is effective at identifying galaxies at z>1.2. Using a counts-in-cell analysis, we identify a field as overdense when 15 or more red IRAC sources are found within 1arcmin (i.e.,~0.5Mpc at 1.2<z<3) of the radio galaxy to the 5sigma flux density limits of our IRAC data (f3.6=11.0uJy, f4.5=13.4uJy). We find that radio galaxies lie preferentially in medium to dense regions, with 73% of the targeted fields denser than average. Our (shallow) 120s data permit the rediscovery of previously known clusters and protoclusters associated with radio galaxies as well as the discovery of new promising galaxy cluster candidates at z>1.2.Comment: 14 pages, 7 figures, 3 tables, accepted for publication in Ap

The Spitzer High Redshift Radio Galaxy Survey

We present results from a comprehensive imaging survey of 70 radio galaxies at redshifts 1<z<5.2 using all three cameras onboard the Spitzer Space Telescope. The resulting spectral energy distributions unambiguously show a stellar population in 46 sources and hot dust emission associated with the active nucleus in 59. Using a new restframe S_3um/S_1.6um versus S_um/S_3um criterion, we identify 42 sources where the restframe 1.6um emission from the stellar population can be measured. For these radio galaxies, the median stellar mass is high, 2x10^11 M_sun, and remarkably constant within the range 13, there is tentative evidence for a factor of two decrease in stellar mass. This suggests that radio galaxies have assembled the bulk of their stellar mass by z~3, but confirmation by more detailed decomposition of stellar and AGN emission is needed. The restframe 500 MHz radio luminosities are only marginally correlated with stellar mass but are strongly correlated with the restframe 5um hot dust luminosity. This suggests that the radio galaxies have a large range of Eddington ratios. We also present new Very Large Array 4.86 and 8.46 GHz imaging of 14 radio galaxies and find that radio core dominance --- an indicator of jet orientation --- is strongly correlated with hot dust luminosity. While all of our targets were selected as narrow-lined, type 2 AGNs, this result can be understood in the context of orientation-dependent models if there is a continuous distribution of orientations from obscured type 2 to unobscured type 1 AGNs rather than a clear dichotomy. Finally, four radio galaxies have nearby (<6") companions whose mid-IR colors are suggestive of their being AGNs. This may indicate an association between radio galaxy activity and major mergers.Comment: 31 pages, 125 figures. Accepted for publication in the Astrophysical Journa

A large-scale galaxy structure at z = 2.02 associated with the radio galaxy MRC 0156-252

We present the spectroscopic confirmation of a structure of galaxies surrounding the radio galaxy MRC 0156-252 at z = 2.02. The structure was initially discovered as an overdensity of both near-infrared selected z > 1.6 and mid-infrared selected z > 1.2 galaxy candidates. We used the VLT/FORS2 multi-object spectrograph to target ~80 high-redshift galaxy candidates, and obtain robust spectroscopic redshifts for more than half the targets. The majority of the confirmed sources are star-forming galaxies at z > 1.5. In addition to the radio galaxy, two of its close-by companions (<6″) also show AGN signatures. Ten sources, including the radio galaxy, lie within | z − 2.020 | <0.015 (i.e., velocity offsets <1500 km s^-1) and within projected 2 Mpc comoving of the radio galaxy. Additional evidence suggests not only that the galaxy structure associated with MRC 0156-252 is a forming galaxy cluster but also that this structure is most probably embedded in a larger-scale structure

A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE

In this small note we are concerned with the solution of Forward-Backward Stochastic Differential Equations (FBSDE) with drivers that grow quadratically in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem is a comparison result that allows comparing componentwise the signs of the control processes of two different qgFBSDE. As a byproduct one obtains conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio

Measurement of the forward Z boson production cross-section in pp collisions at s=13\sqrt{s} = 13 TeV

A measurement of the production cross-section of Z bosons in pp collisions at $\sqrt{s} = 13$ TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range $2.0 \eta 4.5$, transverse momenta $p_\text{T} 20$ GeV and dilepton invariant mass in the range $60 m(\ell\ell) 120$ GeV. The integrated cross-section from averaging the two final states is \begin{equation*}\sigma_{\text{Z}}^{\ell\ell} = 194.3 \pm 0.9 \pm 3.3 \pm 7.6\text{ pb,}\end{equation*} where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable $\phi^*_\eta$