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Accurate modelling of redshift-space distortions (RSD) is challenging in the non-linear regime for two-point statistics e.g. the two-point correlation function (2PCF). We take a different perspective to split the galaxy density field according to the local density, and cross-correlate those densities with the entire galaxy field. Using mock galaxies, we demonstrate that combining a series of cross-correlation functions (CCFs) offers improvements over the 2PCF as follows: 1. The distribution of peculiar velocities in each split density is nearly Gaussian. This allows the Gaussian streaming model for RSD to perform accurately within the statistical errors of a ($1.5\,h^{-1}$Gpc)$^3$ volume for almost all scales and all split densities. 2. The PDF of the density field at small scales is non-Gaussian, but the CCFs of split densities capture the non-Gaussianity, leading to improved cosmological constraints over the 2PCF. We can obtain unbiased constraints on the growth parameter $f\sigma_{12}$ at the per-cent level, and Alcock-Paczynski (AP) parameters at the sub-per-cent level with the minimal scale of $15\,h^{-1}{\rm Mpc}$. This is a $\sim$30 per cent and $\sim$6 times improvement over the 2PCF, respectively. The diverse and steep slopes of the CCFs at small scales are likely to be responsible for the improved constraints of AP parameters. 3. Baryon acoustic oscillations (BAO) are contained in all CCFs of split densities. Including BAO scales helps to break the degeneracy between the line-of-sight and transverse AP parameters, allowing independent constraints on them. We discuss and compare models for RSD around spherical densities., Comment: 23 pages, 16 figures, MNRAS accepted version after peer review, minor comments

Cosmic voids are a key component of the large-scale structure that contain a plethora of cosmological information. Typically, voids are identified from the underlying galaxy distribution, which is a biased tracer of the total matter field. Previous works have shown that 2D voids identified in weak lensing maps -- weak lensing voids -- correspond better to true underdense regions along the line of sight. In this work, we study how the properties of weak lensing voids depend on the choice of void finder, by adapting several popular void finders. We present and discuss the differences between identifying voids directly in the convergence maps, and in the distribution of weak lensing peaks. Particular effort has been made to test how these results are affected by galaxy shape noise, which is a dominant source of noise in weak lensing observations. By studying the signal-to-noise ratios (SNR) for the tangential shear profile of each void finder, we find that voids identified directly in the convergence maps have the highest SNR but are also the ones most affected by galaxy shape noise. Troughs are least affected by noise, but also have the lowest SNR. The tunnel algorithm, which identifies voids in the distribution of weak lensing peaks, represents a good compromise between finding a large tangential shear SNR and mitigating the effect of galaxy shape noise., Comment: 25 pages, 10 figures, Accepted in MNRAS

The EAGLE simulation suite has previously been used to investigate the relationship between the stellar mass of galaxies, $M_{*}$, and the properties of dark matter halos, using the hydrodynamical reference simulation combined with a dark matter only (DMO) simulation having identical initial conditions. The stellar masses of central galaxies in halos with $M_{\mathrm{200c}} > 10^{11} \mathrm{M_{\odot}}$ were shown to correlate with the DMO halo maximum circular velocity, with $\approx 0.2$ dex of scatter that is uncorrelated with other DMO halo properties. Here we revisit the origin of the scatter in the $M_{*}-V_{\mathrm{max, DMO}}$ relation in EAGLE at $z = 0.1$. We find that the scatter in $M_{*}$ correlates with the mean age of the galaxy stellar population such that more massive galaxies at fixed $V_{\mathrm{max, DMO}}$ are younger. The scatter in the stellar mass and mean stellar population age results from variation in the baryonic mass, $M_{\mathrm{bary}} = M_{\mathrm{gas}} + M_{*}$, of the galaxies' progenitors at fixed halo mass and concentration. At the redshift of peak correlation ($z \approx 1$), the progenitor baryonic mass accounts for $75\%$ of the variance in the $z=0.1$ $M_{*}-V_{\mathrm{max, DMO}}$ relation. The scatter in the baryonic mass, in turn, is primarily set by differences in feedback strength and gas accretion over the course of the evolution of each halo., 15 pages, 9 figures. Version accepted to MNRAS

We study cosmic voids in the normal-branch Dvali-Gabadadze-Porrati (nDGP) braneworld models, which are representative of a class of modified gravity theories where deviations from General Relativity are usually hidden by the Vainshtein screening in high-density environments. This screening is less efficient away from these environments, which makes voids ideally suited for testing this class of models. We use N-body simulations of $\Lambda$-cold dark matter ($\Lambda$CDM) and nGDP universes, where dark matter haloes are populated with mock galaxies that mimic the clustering and number densities of the BOSS CMASS galaxy sample. We measure the force, density and weak lensing profiles around voids identified with six different algorithms. Compared to $\Lambda$CDM, voids in nDGP are more under-dense due to the action of the fifth force that arises in these models, which leads to a faster evacuation of matter from voids. This leaves an imprint on the weak lensing tangential shear profile around nDGP voids, an effect that is particularly strong for 2D underdensities that are identified in the plane-of-the-sky. We make predictions for the feasibility of distinguishing between nDGP and $\Lambda$CDM using void lensing in upcoming large-scale surveys such as LSST and Euclid. We compare with the analysis of voids in chameleon gravity theories and find that the weak lensing signal for 3D voids is similar to nDGP, whereas for 2D voids the differences with $\Lambda$CDM are much stronger for the chameleon gravity case, a direct consequence of the different screening mechanisms operating in these theories., Comment: 17 pages, 12 figures; accepted version for publication in MNRAS

We present a systematic comparison of several existing and new void finding algorithms, focusing on their potential power to test a particular class of modified gravity models - chameleon $f(R)$ gravity. These models deviate from standard General Relativity (GR) more strongly in low-density regions and thus voids are a promising venue to test them. We use Halo Occupation Distribution (HOD) prescriptions to populate haloes with galaxies, and tune the HOD parameters such that the galaxy two-point correlation functions are the same in both f(R) and GR models. We identify both 3D voids as well as 2D underdensities in the plane-of-the-sky to find the same void abundance and void galaxy number density profiles across all models, which suggests that they do not contain much information beyond galaxy clustering. However, the underlying void dark matter density profiles are significantly different, with f(R) voids being more underdense than GR ones, which leads to f(R) voids having a larger tangential shear signal than their GR analogues. We investigate the potential of each void finder to test f(R) models with near-future lensing surveys such as EUCLID and LSST. The 2D voids have the largest power to probe f(R) gravity, with a LSST analysis of tunnel (which is a new type of 2D underdensity introduced here) lensing distinguishing at 80 and 11$\sigma$ (statistical error) f(R) models with $|f_{R0}|=10^{-5}$ and $10^{-6}$ from GR., Comment: 22 pages, 13 figures, version accepted for publication in MNRAS

We present ultraviolet, optical, near-infrared photometry and spectroscopy of SN 2009N in NGC 4487. This object is a type II-P supernova with spectra resembling those of subluminous II-P supernovae, while its bolometric luminosity is similar to that of the intermediate luminosity SN 2008in. We created SYNOW models of the plateau phase spectra for line identification and to measure the expansion velocity. In the near-infrared spectra we find signs indicating possible weak interaction between the supernova ejecta and the pre-existing circumstellar material. These signs are also present in the previously unpublished near-infrared spectra of SN 2008in. The distance to SN 2009N is determined via the expanding photosphere method and the standard candle method as $D= 21.6 \pm 1.1\,{\mathrm {Mpc}}$. The produced nickel-mass is estimated to be $\sim 0.020 \pm 0.004\,{\mathrm M_\odot}$. We infer the physical properties of the progenitor at the explosion through hydrodynamical modelling of the observables. We find the values of the total energy as $\sim 0.48 \times 10^{51}\, {\mathrm {erg}}$, the ejected mass as $\sim 11.5\,{\mathrm M_\odot}$, and the initial radius as $\sim 287\,{\mathrm R_\odot}$., 23 pages, 18 figures, accepted for publication by MNRAS

The use of high-quality simulated sky catalogs is essential for the success of cosmological surveys. The catalogs have diverse applications, such as investigating signatures of fundamental physics in cosmological observables, understanding the effect of systematic uncertainties on measured signals and testing mitigation strategies for reducing these uncertainties, aiding analysis pipeline development and testing, and survey strategy optimization. The list of applications is growing with improvements in the quality of the catalogs and the details that they can provide. Given the importance of simulated catalogs, it is critical to provide rigorous validation protocols that enable both catalog providers and users to assess the quality of the catalogs in a straightforward and comprehensive way. For this purpose, we have developed the DESCQA framework for the Large Synoptic Survey Telescope Dark Energy Science Collaboration as well as for the broader community. The goal of DESCQA is to enable the inspection, validation, and comparison of an inhomogeneous set of synthetic catalogs via the provision of a common interface within an automated framework. In this paper, we present the design concept and first implementation of DESCQA. In order to establish and demonstrate its full functionality we use a set of interim catalogs and validation tests. We highlight several important aspects, both technical and scientific, that require thoughtful consideration when designing a validation framework, including validation metrics and how these metrics impose requirements on the synthetic sky catalogs., La lista completa de autores se encuentra en el documento., Instituto de Astrofísica de La Plata, Facultad de Ciencias Astronómicas y Geofísicas

Cosmic voids are promising tools for cosmological tests due to their sensitivity to dark energy, modified gravity and alternative cosmological scenarios. Most previous studies in the literature of void properties use cosmological N-body simulations of dark matter (DM) particles that ignore the potential effect of baryonic physics. Using a spherical underdensity finder, we analyse voids using the mass field and subhalo tracers in the EAGLE simulations, which follow the evolution of galaxies in a $\rm{\Lambda}$ cold dark matter Universe with state-of-the-art subgrid models for baryonic processes in a $(100 \rm{cMpc})^3$ volume. We study the effect of baryons on void statistics by comparing results with DM-only simulations that use the same initial conditions as EAGLE. When identifying voids in the mass field, we find that a DM-only simulation produces 24 per cent more voids than a hydrodynamical one due to the action of galaxy feedback polluting void regions with hot gas, specially for small voids with $r_{\rm{void}} \le 10\ \rm{Mpc}$. We find that the way in which galaxy tracers are selected has a strong impact on the inferred void properties. Voids identified using galaxies selected by their stellar mass are larger and have cuspier density profiles than those identified by galaxies selected by their total mass. Overall, baryons have minimal effects on void statistics, as void properties are well captured by DM-only simulations, but it is important to account for how galaxies populate DM haloes to estimate the observational effect of different cosmological models on the statistics of voids., Comment: Accepted for publication in MNRAS, 21 pages, 16 figures

We present optical and near-infrared photometry and spectroscopy of SN 2009ib, a Type II-P supernova in NGC 1559. This object has moderate brightness, similar to those of the intermediate-luminosity SNe 2008in and 2009N. Its plateau phase is unusually long, lasting for about 130 days after explosion. The spectra are similar to those of the subluminous SN 2002gd, with moderate expansion velocities. We estimate the $^{56}$Ni mass produced as $0.046 \pm 0.015\,{\rm M}_{\sun}$. We determine the distance to SN 2009ib using both the expanding photosphere method (EPM) and the standard candle method. We also apply EPM to SN 1986L, a type II-P SN that exploded in the same galaxy. Combining the results of different methods, we conclude the distance to NGC 1559 as $D=19.8 \pm 3.0$ Mpc. We examine archival, pre-explosion images of the field taken with the Hubble Space Telescope, and find a faint source at the position of the SN, which has a yellow colour ($(V-I)_0 = 0.85$ mag). Assuming it is a single star, we estimate its initial mass as $M_{\rm ZAMS}=20\,{\rm M}_{\sun}$. We also examine the possibility, that instead of the yellow source the progenitor of SN 2009ib is a red supergiant star too faint to be detected. In this case we estimate the upper limit for the initial zero-age main sequence mass of the progenitor to be $\sim 14-17\,{\rm M}_{\sun}$. In addition, we infer the physical properties of the progenitor at the explosion via hydrodynamical modelling of the observables, and estimate the total energy as $\sim 0.55 \times 10^{51}$~erg, the pre-explosion radius as $\sim 400\,{\rm R}_{\sun}$, and the ejected envelope mass as $\sim 15\,{\rm M}_{\sun}$, which implies that the mass of the progenitor before explosion was $\sim 16.5-17\,{\rm M}_{\sun}$., Comment: 18 pages plus 7 page appendix; accepted version (MNRAS), v3: a reference and typos corrected

Observations spanning a large wavelength range, from X-ray to radio, of the Type IIb supernova 2011hs are presented, covering its evolution during the first year after explosion. The optical light curve presents a narrower shape and a fainter luminosity at peak than previously observed for Type IIb SNe. High expansion velocities are measured from the broad absorption H I and He I lines. From the comparison of the bolometric light curve and the time evolution of the photospheric velocities with hydrodynamical models, we found that SN 2011hs is consistent with the explosion of a 3-4 Msun He-core progenitor star, corresponding to a main sequence mass of 12-15 Msun, that ejected a mass of 56Ni of about 0.04 Msun, with an energy of E= 8.5 x 10^50 erg. Such a low-mass progenitor scenario is in full agreement with the modelling of the nebular spectrum taken at $\sim$215 days from maximum. From the modelling of the adiabatic cooling phase, we infer a progenitor radius of $\approx$500-600 Rsun, clearly pointing to an extended progenitor star. The radio light curve of SN 2011hs yields a peak luminosity similar to that of SN 1993J, but with a higher mass loss rate and a wind density possibly more similar to that of SN 2001ig. Although no significant deviations from a smooth decline have been found in the radio light curves, we cannot rule out the presence of a binary companion star., 25 pages, 19 figures, 10 tables. Accepted for publication in MNRAS

Studying 2,413 cases of supratentorial brain tumors operated on a 30 years period, the author emphasizes appealing signs, pitfalls, and tumoral relapses. Epilepsy is the most frequent initial sign preceding headache and focal signs. We discuss the frequency of the epilepsy, the age of the first seizure, the location and the histological nature of the epiletogenic tumor, and the type of the seizures. In the end, we study diagnosis pitfalls such as long-standing epilepsy, ictal presentation, pitfalls due to metastases and the difficult problem of tumoral relapses.

SUMMARY This etiological and clinical study concludes with the following propositions. 1 In cases of cranial trauma, those having had severe hemispheric lesions with anatomically proven damage are predisposed to epilepsy. 2 A delay in the maturation of the epileptogenic focus is necessary; this delay is longer the younger the patient and the further the initial lesion from the motor area; it is shorter when the brain lesions are more numerous and diffuse. 3 Generalized seizures are frequently signs of traumatic epilepsy, but not exclusively; they also stem from frontal lesions and to a slightly lesser degree from temporal lesions, but any cortical lesion may induce them. Psychomotor seizures are seen mainly after temporal lobe lesions but less frequently after injury to neighbouring lobes; Bravais-Jacksonian attacks are more rare. 4 Seizures with partial clinical expression do not necessarily indicate a single lesion confined to the corresponding cortical area. 5 Although the predominance of cortical lesions in determining traumatic epilepsy is accepted, the role of the brain stem lesion is still to be determined. RESUME Les auteurs ont etudie 247 epileptiques sur une serie de 2331 traumatises crâniens. La duree d'observation a ete de 3 a 16 ans. 1 Parmi les traumatises crâniens sont predisposes a l'epilepsie ceux qui ont eu des lesions hemispheriques severes laissant des dommages anatomiques demonstrables; 2 Un delai de maturation du foyer epileptogene est necessaire, d'autant plus long que le blesse est plus jeune et que la lesion initiale est a distance de la zone motrice, d'autant plus court que les lesions encephaliques sont plus nombreuses et diffuses; 3 Les crises generalisees sont l'expression frequente de l'epilepsie traumatique mais non exclusive; elles relevent essentiellement des lesions frontales, a un degre un peu moindre des lesions temporales, mais toute lesion du cortex peut les induire; les crises psycho-motrices s'observent essentiellement apres lesion temporale, mais aussi avec une moindre frequence apres alteration des lobes voisins; les crises bravais-jacksoniennes sont plus rares; 4 Des crises d'expression clinique partielle ne signent pas obligatoirement une seule lesion confinee a l'aire corticale correspondante; 5 Si Ton admet la preeminence des lesions corticales dans le determinisme de l'epilepsie traumatique, la place tenue par les lesions du tronc cerebral reste encore a apprecier.

Medulloblastoma is classically a childhood tumor, but one third of the cases occurs in adulthood. 17 adult cases are reported here (12 men, 5 women). The average age was 26 years 6 m (from 16 to 47 years). Pre-surgical clinical course is shorter before 30 years (7 months) than after (up to 24 months). Initial symptoms were intracranial hypertension with signs of lateralisation in 2:3 of the cases (cranial nerve and pontocerebellar syndroms). Vertebral angiography, scintigraphy, tomodensitometry helped to the diagnosis. Morphologically, two variants of tumors were found: soft and infiltrative classical medulloblastoma (12 cases) and desmoplastic medulloblastoma which was firmer and better limited (5 cases). The treatment consisted of a surgical removal, as complete as possible, then of an entire neuraxis radiation. Three operated patients died before 6 weeks. Among the 14 other cases, six patients are still alive three years, four other, five years and one, 22 years after the operation. This histological type was of no influence on the post-operative course. Remote metastasis were noted in cauda equina (3 cases), in spinal cord (1 case), in bones and lymphatic nodes (3 cases).

The authors report 90 cases of space occupying lesions originating in the occipital lobe, including 58 primary (26 malignant gliomas, II "benign" gliomas, 19 meningiomas, I sarcoma nad I hémangioblastoma (and 32 secondary masses (i. e. 16 metastatic tumors, 15 abcesses and I hydatid cyst). The onset of clinical features was progressive (gradual increase of intracranial pressure : 59 p. 100) rather than acute (41 p. 100 mostly as a visual (II) or a non visual (10) epileptic seizure). The time elapsed between the first symptom and the surgical procedure in any case appeared to be much shorter than in masses with other hemispheric localisation. This is thought to be due to the precocity and the intensity of the increased intracranial pressure, in relation to the blocage of posterior venous drainage. Increased intracranial pressure : only 7,7 p. 100 of the patient were free of IIP. Fundal changes are of little value in excluding this finding since no less than 3 months of evolution are necessary for their appearence. Visual disturbances consisted of acute obscurations (7.7 p. 100), controlateral deviations of head and eyes (3.3 p. 100) and visual field defects = 10 p. 100 of the patients were comatose and unable to be examined, 16.6 p. 100 had normal visual field. All the others had visual field defects wich could be evaluated by campimetric examination in only 26.6 p. 100. These included 14 hemiopias (7 without macular sparing) and 10 quadranopsia, always with incongruence (4 superior and 6 inferior). When the mass was strictly occipital, the same disparity was observed. Finally these visual field defects appeared to be variable and could well recover after surgery. Visual hallucinations were mostly of elementary type (21 p. 100) and always controlateral in cases of strictly occipital lesions. Elaborate hallucinations were rare (2 patients with extensive lesions). 8.8 p. 100 suffered from visual illusions wich always were related to large and right-sided masses. Disturbances of higher functions : Alexia was seen in 33 p. 100 of the left-sided masses (24 p. 100 "agraphic", 9 p. 100 "pure word blindness") Space agnosias of different type was found in 10 p. 100 of the patients, sometimes with purely occipital tumors.

The authors report their experience of 84 patients with oligodendroglioma seen over a 34 year period. The low incidence of these brain tumors is underlined. Oligodendroglioma is the most epileptogenic of brain tumors. The clinical picture may resemble "essential" epilepsy. Normal EEG should be considered suspect in confirmed epileptic children and adolescents since oligodendroglioma is the most common of all tumors which induce long-standing epilepsy. Emphasis is put on the importance of computerized tomography and radionuclide scanning for early detection of these tumors. Both procedures are very helpful for deciding on the best operative approach and for determining whether the lesion is malignant or not. The authors advise tumorectomy, which should be as complete as possible, followed by systematic radiotherapy, even if histopathological criteria indicate a benign tumor. With this therapeutic regimen mean survival rates are significantly higher than those published previously.

Between 1975 and 1983, 17 patients who underwent surgery for haemangioblastomas of the brain (16 lesions occurring in the posterior fossa) were studied with CT scans (17 cases) and vertebral angiograms (15 cases). The CT scans were superior for demonstrating a cystic tumour, its topography in the posterior fossa, its relationship to the fourth ventricle, and the presence and degree of an obstructive hydrocephalus. The vertebral angiographies were more sensitive and specific than CT for revealing the vascular nature, and were imperative in order to establish the supply and drainage of the tumours. It is clear that CT and angiography each make an important contribution toward defining these tumours. Their association is necessary.

The use of computer tomography and myelography with amipaque is of considerable value for establishing the diagnosis of the Arnold-Chiari syndrome. The cerebral lesion (hydrocephalus) can be clearly demonstrated, together with a hernia of the amygdalae, IVth ventricle abnormalities and the size and contents of any myelomeningocele present.