The XXL Survey Pacaud, F; Clerc, N; Giles, P A ...
Astronomy and astrophysics (Berlin),
08/2016, Letnik:
592
Journal Article
Recenzirano
Odprti dostop
Context. The XXL Survey is the largest survey carried out by the XMM-Newton satellite and covers a total area of 50 square degrees distributed over two fields. It primarily aims at investigating the ...large-scale structures of the Universe using the distribution of galaxy clusters and active galactic nuclei as tracers of the matter distribution. The survey will ultimately uncover several hundreds of galaxy clusters out to a redshift of ~2 at a sensitivity of ~10 super(-14) ergs super(-1)cm super(-2) in the 0.5-2 keV band. Aims. This article presents the XXL bright cluster sample, a subsample of 100 galaxy clusters selected from the full XXL catalogue by setting a lower limit of 3 x 10 super(-14) erg s super(-1) cm super(-2) on the source flux within a 1? aperture. Methods. The selection function was estimated using a mixture of Monte Carlo simulations and analytical recipes that closely reproduce the source selection process. An extensive spectroscopic follow-up provided redshifts for 97 of the 100 clusters. We derived accurate X-ray parameters for all the sources. Scaling relations were self-consistently derived from the same sample in other publications of the series. On this basis, we study the number density, luminosity function, and spatial distribution of the sample. Results. The bright cluster sample consists of systems with masses between M sub(500)= 7 x 10 super(13) and 3 x 10 super(14)M sub(?), mostly located between z= 0.1 and 0.5. The observed sky density of clusters is slightly below the predictions from the WMAP9 model, and significantly below the prediction from the Planck 2015 cosmology. In general, within the current uncertainties of the cluster mass calibration, models with higher values of sigma sub(8) and/or Omega sub(M) appear more difficult to accommodate. We provide tight constraints on the cluster differential luminosity function and find no hint of evolution out to z~ 1. We also find strong evidence for the presence of large-scale structures in the XXL bright cluster sample and identify five new superclusters.
We present the general real- and redshift-space clustering properties of galaxies as measured in the first data release of the VIPERS survey. VIPERS is a large redshift survey designed to probe in ...detail the distant Universe and its large-scale structure at 0.5 < z < 1.2. We describe in this analysis the global properties of the sample and discuss the survey completeness and associated corrections. This sample allows us to measure the galaxy clustering with an unprecedented accuracy at these redshifts. From the redshift-space distortions observed in the galaxy clustering pattern we provide a first measurement of the growth rate of structure at z = 0.8: fsigma8 = 0.47 + or - 0.08. This is completely consistent with the predictions of standard cosmological models based on Einstein gravity, although this measurement alone does not discriminate between different gravity models.
Context. In the context of large-scale structure formation, clusters of galaxies are located at the nodes of the cosmic web, and continue to accrete galaxies and groups along filaments. In some ...cases, they show a very large extension and a preferential direction. Brightest cluster galaxies (BCGs) are believed to grow through the accretion of many small galaxies, and their structural properties are therefore expected to vary with redshift. In some cases BCGs show an orientation comparable to that of the cluster to which they belong. Aims. We analyse the morphological properties of 38 BCGs from the DAFT/FADA and CLASH surveys, and compare the position angles of their major axes to the direction of the cluster elongation at large scale (several Mpc). Methods. The morphological properties of the BCGs were studied by applying the GALFIT software to HST images and fitting the light distribution with one or two Sérsic laws, or with a Nuker plus a Sérsic law. The cluster elongations at very large scale were estimated by computing density maps of red sequence galaxies. Results. The morphological analysis of the 38 BCGs shows that in 11 cases a single Sérsic law is sufficient to account for the surface brightness, while for all the other clusters two Sérsic laws are necessary. In five cases, a Nuker plus a Sérsic law give a better fit. For the outer Sérsic component, the effective radius increases with decreasing redshift, and the effective surface brightness decreases with effective radius, following the Kormendy law. An agreement between the major axis of the BCG and the cluster elongation at large scale within ±30 deg is found for 12 clusters out of the 21 for which the PAs of the BCG and of the large-scale structure can be defined. Conclusions. The variation with redshift of the effective radius of the outer Sérsic component agrees with the growing of BCGs by accretion of smaller galaxies from z = 0.9 to 0.2, and it would be interesting to investigate this variation at higher redshift. The directions of the elongations of BCGs and of their host clusters and large scale structures surrounding them agree for 12 objects out of 21, implying that a larger sample is necessary to reach more definite conclusions.
•Acupuncture decreased opioid consumption in dogs undergoing spinal surgery.•Acupuncture improved analgesia after hemilaminectomy in dogs.•Acupuncture was not associated with side ...effects.•Acupuncture did not increase the anaesthetic time.•Combining behavioural scales and mechanical thresholds was useful to assess pain.
The aim of this study was to investigate the analgesic efficacy of a preoperative acupuncture treatment in 24 client-owned dogs undergoing thoracolumbar hemilaminectomy. Dogs were randomly assigned to either group A (Acupuncture) or group C (Control). Before skin incision, group A was treated with acupuncture, performed under general anaesthesia for 30 min. Rescue intraoperative fentanyl was administered following a 20% increase in cardiovascular parameters compared to baseline values, measured before incision. An observer masked to the treatment assessed pain, pre- and postoperatively, with the Glasgow (GCPS), the Colorado (CPS) pain scales and a Visual Analogue Scale (VAS); additionally, the mechanical thresholds (MT) were measured with the Electronic von Frey Anaesthesiometer (EVF) at four points located near the herniated disc. The groups were compared with respect to intraoperative cardiovascular and respiratory variables, rescue fentanyl administered in total and at different surgical events (first incision FI, drilling DR, disc removal RE and skin suturing ST), and pre- and postoperative pain scores and MT.
Group A received less fentanyl than group C (P = 0.014); this difference was significant at FI P = 0.035) and RE (P = 0.004). The improvement in postoperative CPS score (P = 0.013), VAS score (P = 0.003) and MT (P = 0.001) compared to preoperative values was greater for group A than for group C, whereas the treatment assignment had no effect on postoperative changes in GCPS compared to baseline. Pre-operative acupuncture may help improving perioperative analgesia in dogs with intervertebral disc herniation undergoing thoracolumbar hemilaminectomy.
Aims. The aim of this work is to identify He II emitters at 2 < z < 4.6 and to constrain the source of the hard ionizing continuum that powers the He II emission. Methods. We assembled a sample of ...277 galaxies with a highly reliable spectroscopic redshift at 2 < z < 4.6 from the VIMOS-VLT Deep Survey (VVDS) Deep and Ultra-Deep data, and we identified 39 He II λ1640 emitters. We studied their spectral properties, measuring the fluxes, equivalent widths (EW), and full width at half maximum (FWHM) for most relevant lines, including He II λ1640, Lyα line, Si II λ1527, and C IV λ1549. Results. About 10% of galaxies at z ~ 3 and iAB ≤ 24.75 show He II in emission, with rest frame equivalent widths EW0 ~ 1–7 Å, equally distributed between galaxies with Lyα in emission or in absorption. We find 11 (3.9% of the global population) reliable He II emitters with unresolved He II lines (FWHM0 < 1200 km s-1), 13 (4.6% of the global population) reliable emitters with broad He II emission (FWHM0 > 1200 km s-1), 3 active galactic nuclei (AGN), and an additional 12 possible He II emitters. The properties of the individual broad emitters are in agreement with expectations from a Wolf-Rayet (W-R) model. Instead, the properties of the narrow emitters are not compatible with this model, nor with predictions of gravitational cooling radiation produced by gas accretion, unless this is severely underestimated by current models by more than two orders of magnitude. Rather, we find that the EW of the narrow He II line emitters are in agreement with expectations for a Population III (PopIII) star formation, if the episode of star formation is continuous, and we calculate that a PopIII star formation rate (SFR) of 0.1–10 M⊙ yr-1 alone is enough to sustain the observed He II flux. Conclusions. We conclude that narrow He II emitters are powered either by the ionizing flux from a stellar population rare at z ~ 0 but much more common at z ~ 3, or by PopIII star formation. As proposed by Tornatore and collaborators, incomplete interstellar medium mixing may leave some small pockets of pristine gas at the periphery of galaxies from which PopIII may form, even down to z ~ 2 or lower. If this interpretation is correct, we measure at z ~ 3 a star formation rate density in PopIII stars of 10-6 M⊙ yr-1 Mpc-3, higher than, but qualitatively comparable to the value predicted by Tornatore and collaborators.
The XXL Survey Lieu, M; Smith, G P; Giles, P A ...
Astronomy and astrophysics (Berlin),
08/2016, Letnik:
592
Journal Article
Recenzirano
Odprti dostop
Context. The XXL Survey is the largest survey carried out by XMM-Newton. Covering an area of 50 deg super(2), the survey contains ~450 galaxy clusters out to a redshift ~2 and to an X-ray flux limit ...of ~ 5 x 10 super(-15) erg s super(-1) cm super(-2). This paper is part of the first release of XXL results focussed on the bright cluster sample. Aims. We investigate the scaling relation between weak-lensing mass and X-ray temperature for the brightest clusters in XXL. The scaling relation discussed in this article is used to estimate the mass of all 100 clusters in XXL-100-GC. Methods. Based on a subsample of 38 objects that lie within the intersection of the northern XXL field and the publicly available CFHTLenS shear catalog, we derive the weak-lensing mass of each system with careful considerations of the systematics. The clusters lie at 0.1 <z< 0.6 and span a temperature range of T? 1?5 keV. We combine our sample with an additional 58 clusters from the literature, increasing the range to T? 1?10 keV. To date, this is the largest sample of clusters with weak-lensing mass measurements that has been used to study the mass-temperature relation. Results. The mass-temperature relation fit (M? Tb) to the XXL clusters returns a slope b= 1.78 super(+0.37) sub(-0.32) and intrinsic scatter sigma sub(ln)MT? 0.53; the scatter is dominated by disturbed clusters. The fit to the combined sample of 96 clusters is in tension with self-similarity, b= 1.67 + or - 0.12 and sigma sub(ln)MT? 0.41. Conclusions. Overall our results demonstrate the feasibility of ground-based weak-lensing scaling relation studies down to cool systems of ~1 keV temperature and highlight that the current data and samples are a limit to our statistical precision. As such we are unable to determine whether the validity of hydrostatic equilibrium is a function of halo mass. An enlarged sample of cool systems, deeper weak-lensing data, and robust modelling of the selection function will help to explore these issues further.
We present the first Public Data Release (PDR-1) of the VIMOS Public Extragalactic Survey (VIPERS). It comprises 57 204 spectroscopic measurements together with all additional information necessary ...for optimal scientific exploitation of the data, in particular the associated photometric measurements and quantification of the photometric and survey completeness. VIPERS is an ESO Large Programme designed to build a spectroscopic sample of similar to 100 000 galaxies with i sub(AB) < 22.5 and 0.5 < z < 1.2 with high sampling rate ( similar to 45%). The survey spectroscopic targets are selected from the CFHTLS-Wide five-band catalogues in the W1 and W4 fields. The final survey will cover a total area of nearly 24 deg super(2), for a total comoving volume between z = 0.5 and 1.2 of similar to 4 x 10 super(7) h super(-3) Mpc super(3) and a median galaxy redshift of z similar to 0.8. The release presented in this paper includes data from virtually the entire W4 field and nearly half of the W1 area, thus representing 64% of the final dataset. We provide a detailed description of sample selection, observations and data reduction procedures; we summarise the global properties of the spectroscopic catalogue and explain the associated data products and their use, and provide all the details for accessing the data through the survey database (http://vipers.inaf.it) where all information can be queried interactively.
We present the first quantitative detection of large-scale filamentary structure at z NOT approximately equal to 0.7 in the large cosmological volume probed by the VIMOS Public Extragalactic ...Redshift Survey (VIPERS). We use simulations to show the capability of VIPERS to recover robust topological features in the galaxy distribution, in particular the filamentary network. We then investigate how galaxies with different stellar masses and stellar activities are distributed around the filaments, and find a significant segregation, with the most massive or quiescent galaxies being closer to the filament axis than less massive or active galaxies. The signal persists even after downweighting the contribution of peak regions. Our results suggest that massive and quiescent galaxies assemble their stellar mass through successive mergers during their migration along filaments towards the nodes of the cosmic web. On the other hand, low-mass star-forming galaxies prefer the outer edge of filaments, a vorticity-rich region dominated by smooth accretion, as predicted by the recent spin alignment theory. This emphasizes the role of large-scale cosmic flows in shaping galaxy properties.
The XXL Survey Eckert, D; Ettori, S; Coupon, J ...
Astronomy and astrophysics (Berlin),
08/2016, Letnik:
592
Journal Article
Recenzirano
Odprti dostop
Traditionally, galaxy clusters have been expected to retain all the material accreted since their formation epoch. For this reason, their matter content should be representative of the Universe as a ...whole, and thus their baryon fraction should be close to the Universal baryon fraction Omega sub(b)/ Omega sub(m). We make use of the sample of the 100 brightest galaxy clusters discovered in the XXL Survey to investigate the fraction of baryons in the form of hot gas and stars in the cluster population. Since it spans a wide range of mass (10 super(13)-10 super(15)M sub(middot in circle)) and redshift (0.05-1.1) and benefits from a large set of multiwavelength data, the XXL-100-GC sample is ideal for measuring the global baryon budget of massive halos. We measure the gas masses of the detected halos and use a mass-temperature relation directly calibrated using weak-lensing measurements for a subset of XXL clusters to estimate the halo mass. We find that the weak-lensing calibrated gas fraction of XXL-100-GC clusters is substantially lower than was found in previous studies using hydrostatic masses. Our best-fit relation between gas fraction and mass reads f sub(gas,500)= 0.055 sub(-0.006) super(+0.007) (M sub(500)/10 super(14)M sub(middot in circle)) super(0.21) sub(-0.10)+0 .11. The baryon budget of galaxy clusters therefore falls short of the Universal baryon fraction by about a factor of two at r sub(500,MT). Our measurements require a hydrostatic bias 1-b= M sub(X)/M sub(WL)= 0.72 sub(-0.07) super(+0.08) to match the gas fraction obtained using lensing and hydrostatic equilibrium, which holds independently of the instrument considered. Comparing our gas fraction measurements with the expectations from numerical simulations, we find that our results favour an extreme feedback scheme in which a significant fraction of the baryons are expelled from the cores of halos. This model is, however, in contrast with the thermodynamical properties of observed halos, which might suggest that weak-lensing masses are overestimated. In light of these results, we note that a mass bias 1-b= 0.58 as required to reconcile Planck cosmic microwave background and cluster counts should translate into an even lower baryon fraction, which poses a major challenge to our current understanding of galaxy clusters.
Context.
Within the framework of investigating the link between the central super massive black holes in the cores of galaxies and the galaxies themselves, we detected a variable X-ray source in the ...center of CGCG 077-102 NED02, which is a member of the CGCG 077-102 galaxy pair within the Abell 2063 cluster of galaxies.
Aims.
Our goal is to combine X-ray and optical data to demonstrate that this object harbors an active super massive black hole in its core, and to relate this to the dynamical status of the galaxy pair within the Abell 2063 cluster.
Methods.
We used
Chandra
and
XMM-Newton
archival data to derive the X-ray spectral shape and variability. We also obtained optical spectroscopy to detect the expected emission lines that are typically found in active galactic nuclei. Finally, we used public ZTF imaging data to investigate the optical variability.
Results.
There is no evidence of multiple X-ray sources or extended components within CGCG 077-102 NED02. Single X-ray spectral models fit the source well. We detect significant, nonrandom inter-observation 0.5–10 keV X-ray flux variabilities, for observations separated by ∼4 days for short-term variations and by up to ∼700 days for long-term variations. Optical spectroscopy points toward a passive galaxy for CGCG 077-102 NED01 and a Seyfert for CGCG 077-102 NED02. The classification of CGCG 077-102 NED02 is also consistent with its X-ray luminosity of over 10
42
erg s
−1
. We do not detect short-term variability in the optical ZTF light curves. However, we find a significant long-term stochastic variability in the
g
-band that can be well described by the damped random walk model with a best-fit characteristic damping timescale of
τ
DRW
= 30
−12
+28
days. Finally, the CGCG 077-102 galaxy pair is deeply embedded within the Abell 2063 potential, with a long enough history within this massive structure to have been affected by the influence of this cluster for a long time.
Conclusions.
Our observations point toward a moderately massive black hole in the center of CGCG 077-102 NED02 of ∼10
6
M
⊙
. As compared to another similar pair in the literature, CGCG 077-102 NED02 is not heavily obscured, perhaps because of the surrounding intracluster medium ram-pressure stripping.
PDF
