Gravitational lensing and dynamics in SL2S\,J02140-0535: Probing the mass out to large radius

We aim to probe the mass of SL2S\,J02140-0535, a galaxy group at $z$ = 0.44 from the Strong Lensing Legacy Survey (SL2S). We combine strong lensing modeling and dynamical constraints. The strong lensing analysis is based on multi-band HST/ACS observations exhibiting strong lensing features that we have followed-up spectroscopically with VLT/FORS2. To constrain the scale radius of an NFW mass profile that cannot be constrained by strong lensing, we propose a new method by taking advantage of the large-scale dynamical information provided by VLT/FORS2 and KECK/LRIS spectroscopy of group members. In constrast to other authors, we show that the observed lensing features in SL2S\,J02140-0535 belong to different background sources: one at $z$ = 1.7 $\pm$ 0.1 produces three images, while the other at $z$ = 1.023 $\pm$ 0.001 has only a single image. Our unimodal NFW mass model reproduces these images very well. It is characterized by a concentration parameter $c_{200}$ = 6.0 $\pm$ 0.6, which is slightly greater than the value expected from $\Lambda$CDM simulations for a mass of M$_{200}$ $\approx$ 1 $\times$ 10$^{14}$ M_{\sun}. The spectroscopic analysis of group members also reveals a unimodal structure that exhibits no evidence of merging. We compare our dynamic mass estimate with an independent weak-lensing based mass estimate finding that both are consistent. Our combined lensing and dynamical analysis of SL2S\,J02140-0535 demonstrates the importance of spectroscopic information in reliably identifying the lensing features. Our findings argue that the system is a relaxed, massive galaxy group where mass is traced by light. This work shows a potentially useful method for constraining large-scale properties inaccessible to strong lensing, such as the scale radius of the NFW profile.Comment: Accepted for publication in A&

Survival of Ceriodaphnia dubia (Crustacea, Cladocera) exposed to different screens against natural ultraviolet radiation

The current increase of penetration of natural ultraviolet radiation (UVR) in southern South America affects water bodies because the UVR can penetrate the water column. In this scenario, the zooplankton develops photoprotective strategies such as vertical migrations against UVR or synthesis of photoprotective substances. The present study was done using a population of Ceriodaphnia dubia. That was collected from small shallow wetland near Temuco, Chile. The specimens were exposed for 7 to 9 hours to natural ultraviolet radiation, and with different colored nylon as protection against UVR, the experiment was done during the southern summer of 2006. The results revealed that in the presence of protection against UVR provided by colored nylon, the mortality was low, whereas under exposure to UVR and covering by transparent nylon total mortality was observed. The relation between mortality and the dose of UV that can penetrate the different colored nylon is represented by LC50 in UV (280-400 nm) and UVB (280-320 nm), within intensities of 234.82 and 14.96 kJ/m2, respectively

SARCS strong lensing galaxy groups: I - optical, weak lensing, and scaling laws

We present the weak lensing and optical analysis of the SL2S-ARCS (SARCS) sample of strong lens candidates. The sample is based on the Strong Lensing Legacy Survey (SL2S), a systematic search of strong lensing systems in the photometric Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). The SARCS sample focuses on arc-like features and is designed to contain mostly galaxy groups. We briefly present the weak lensing methodology that we use to estimate the mass of the SARCS objects. Among 126 candidates, we obtain a weak lensing detection for 89 objects with velocity dispersions of the Singular Isothermal Sphere mass model ranging from 350 to 1000 km/s with an average value of 600km/s, corresponding to a rich galaxy group (or poor cluster). From the galaxies belonging to the bright end of the group's red sequence (M_i<-21), we derive the optical properties of the SARCS candidates. We obtain typical richnesses of N=5-15 galaxies and optical luminosities of L=0.5-1.5e+12 Lsol (within a radius of 0.5 Mpc). We use these galaxies to compute luminosity density maps, from which a morphological classification reveals that a large fraction of the sample are groups with a complex light distribution, either elliptical or multimodal, suggesting that these objects are dynamically young structures. We finally combine the lensing and optical analyses to draw a sample of 80 most secure group candidates, i.e. weak lensing detection and over-density at the lens position in the luminosity map, to remove false detections and galaxy-scale systems from the initial sample. We use this reduced sample to probe the optical scaling relations in combination with a sample of massive galaxy clusters. We detect the expected correlations over the probed range in mass with a typical scatter of 25% in the SIS velocity dispersion at a given richness or luminosity, making these scaling laws interesting mass proxie

CLASH-VLT: Strangulation of cluster galaxies in MACSJ0416.1-2403 as seen from their chemical enrichment

(abridged) We explore the Frontier Fields cluster MACS J0416.1-2403 at z=0.3972 with VIMOS/VLT spectroscopy from the CLASH-VLT survey covering a region which corresponds to almost three virial radii. We measure fluxes of 5 emission lines of 76 cluster members enabling us to unambiguously derive O/H gas metallicities, and also SFRs from Halpha. For intermediate massses we find a similar distribution of cluster and field galaxies in the MZR and mass vs. sSFR diagrams. Bulge-dominated cluster galaxies have on average lower sSFRs and higher O/Hs compared to their disk-dominated counterparts. We use the location of galaxies in the projected velocity vs. position phase-space to separate our cluster sample into a region of objects accreted longer time ago and a region of recently accreted and infalling galaxies. We find a higher fraction of accreted metal-rich galaxies (63%) compared to the fraction of 28% of metal-rich galaxies in the infalling regions. Intermediate mass galaxies falling into the cluster for the first time are found to be in agreement with predictions of the fundamental metallicity relation. In contrast, for already accreted star-forming galaxies of similar masses, we find on average metallicities higher than predicted by the models. This trend is intensified for accreted cluster galaxies of the lowest mass bin, that display metallicities 2-3 times higher than predicted by models with primordial gas inflow. Environmental effects therefore strongly influence gas regulations and control gas metallicities of log(M/Msun)<10.2 (Salpeter IMF) cluster galaxies. We also investigate chemical evolutionary paths of model galaxies with and without inflow of gas showing that strangulation is needed to explain the higher metallicities of accreted cluster galaxies. Our results favor a strangulation scenario in which gas inflow stops for log(M/Msun)<10.2 galaxies when accreted by the cluster.Comment: Version better matched to the published version, including table with observed and derived quantities for the 76 cluster galaxie

Dark matter-baryons separation at the lowest mass scale: the Bullet Group

We report on the X-ray observation of a strong lensing selected group, SL2S J08544-0121, with a total mass of $2.4 \pm 0.6 \times 10^{14}$ $\rm{M_\odot}$ which revealed a separation of $124\pm20$ kpc between the X-ray emitting collisional gas and the collisionless galaxies and dark matter (DM), traced by strong lensing. This source allows to put an order of magnitude estimate to the upper limit to the interaction cross section of DM of 10 cm$^2$ g$^{-1}$. It is the lowest mass object found to date showing a DM-baryons separation and it reveals that the detection of bullet-like objects is not rare and confined to mergers of massive objects opening the possibility of a statistical detection of DM-baryons separation with future surveys.Comment: 5 pages, 3 figures. Accepted for publication in MNRAS Letters. Typos correcte

Hubble Space Telescope STIS spectrum of RW Aurigae A: Evidence for an ionized beltlike structure and mass ejection in timescales of a few hours

Profiles of the UV semiforbidden lines of C III](1908) and Si III](1892) of RW Aur have been obtained with the Hubble Space Telescope (HST) STIS. The C III](1908) profile shows two high-velocity components at upsilon = +/-170 km s(-1) and a central one. The Si III](1892) profile is very broad (FWHM = 293 km s(-1)), and the high-velocity components are unresolved. The high-velocity components are most probably produced in a rotating belt similar to that detected in other sources of bipolar outflows. A radius between 2.7 R-* and the corotation radius (6.1 R-*) is derived, and a log T-e(K) similar or equal to 4.7 and log n(e)(cm(-3)) = 11.6 are estimated. The belt is clumpy, and the most likely source of heating is local X-ray radiation, probably associated with the release of magnetic energy. In addition, profiles of the optical lines of He I, Fe II, and Halpha retrieved from the HST archive have been analyzed. The spectra were obtained by shifting the STIS slit between exposures in the transverse direction to the flow. Two features vary from one exposure to another: a blueshifted emission feature (detected in the Fe II and He I lines) and a redshifted absorption feature (detected in Halpha), which are observed at the velocity of the blueshifted and redshifted components of the jet, respectively. There is a clear-cut correlation between the equivalent widths of these two components. These components are not associated with the flaring activity of the source, since they remain stable timescales of similar or equal to40 minutes. They are most likely associated with variations in the stellar/circumstellar environment in timescales of a few (similar or equal to5) hours, consistent with reports by other authors for variations of the veiling and the appearance of shell signatures in the optical spectrum

Far-infrared imaging of post-AGB stars and (proto)-planetary nebulae with the AKARI Far-Infrared Surveyor

By tracing the distribution of cool dust in the extended envelopes of post-AGB stars and (proto)-planetary nebulae ((P)PNe) we aim to recover, or constrain, the mass loss history experienced by these stars in their recent past. The Far-Infrared Surveyor (FIS) instrument on board the AKARI satellite was used to obtain far-infrared maps for a selected sample of post-AGB stars and (P)PNe. We derived flux densities (aperture photometry) for 13 post-AGB stars and (P)PNe at four far-infrared wavelengths (60, 90, 140, and 160 um). Radial (azimuthally averaged) profiles are used to investigate the presence of extended emission from cool dust. No (detached) extended emission is detected for any target in our sample at levels significant with respect to background and cirrus emission. Only IRAS 21046+4739 reveals tentative excess emission between 30 and 130". Estimates of the total dust and gas mass from the obtained maps indicate that the envelope masses of these stars should be large in order to be detected with the AKARI FIS. Imaging with higher sensitivity and higher spatial resolution is needed to detect and resolve, if present, any cool compact or extended emission associated with these evolved stars.Comment: accepted for publication in The Astronomical Journal (16 pages, 3 figures and 4 tables

Strong lensing, weak lensing, and dynamics in SL2S J02140-0535

International audienceWe combine strong lensing modeling and dynamical constraints in order to probe the mass of SL2S J02140-0535, a galaxy group at z = 0.44 from the Strong Lensing Legacy Survey (SL2S) which has uncovered a new population of group-scale strong lenses. The strong lensing analysis is based on multi-band HST/ACS observations which display strong lensing features that we have followed up spectroscopically with VLT/FORS2. To constrain the scale radius of an NFW mass profile, we propose a new method taking advantage of the large scale dynamical information provided by VLT/FORS2 and KECK/LRIS spectroscopy of group members. This work shows a potentially useful method for constraining large-scale properties inaccessible to strong lensing, such as the scale radius of the NFW profile