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Bedin L.R.,National institute for astrophysics | Ruiz-lapuente P.,Institute Fisica Fundamental | Ruiz-lapuente P.,Institute Of Ciencies Del Cosmos Ub Ieec | Ruiz-lapuente P.,Max Planck Institute for Astrophysics | And 7 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

With archival and new Hubble Space Telescope observations, we have refined the spacevelocity measurements of the stars in the central region of the remnant of Tycho's supernova (SN) 1572, one of the historical Galactic Type Ia supernova remnants (SNRs). We derived a proper motion for Tycho-G of (μαcos δ μδ)J2000.0 = (-2.63; -3.98) ± (0.06; 0.04) [formal errors] ± (0.18; 0.10) [expected errors] mas yr-1. If the star were at the distance of the SNR (taken here to be 2.83 kpc), its velocity would be vb = -51 ± 1.5 kms-1.We also reconstruct the binary orbit that Tycho-G should have followed if it were the surviving companion of SN 1572. We redetermine the Ni abundance of this star and compare it with new abundance data from stars of theGalactic disc, finding that [Ni/Fe] is about 1.7σ above the Galactic trend. From the high velocity of Tycho-G perpendicular to the Galactic plane (-90 ± 3 kms-1 ≤ vb ≤ -45 ± 1 kms-1, for the allowed range of distances to the star), its metallicity and its Ni excess, we find the probability of it being a chance interloper to be P {less-than or approximate} 0.000 37 at most. The projected rotational velocity of the star should be below current observational limits. The projected position of Tycho-G is, within the uncertainties, consistent with the centroid of the X-ray emission of Tycho's SNR; moreover, its brightness is generally consistent with the postexplosion evolution of the luminosity of an SN companion. Among the other 23 stars having V < 22 mag and located within 42 arcsec from the X-ray centroid, only 4 are at distances compatible with that of the SNR, and none of them shows any peculiarity. Therefore, if even Tycho-G is not the surviving companion of SN 1572, the absence of other viable candidates does favour the merging of two white dwarfs as the producer of the SN. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Font-Ribera A.,Institute Of Ciencies Of Lespai Csic Ieec | McDonald P.,Lawrence Berkeley National Laboratory | McDonald P.,Brookhaven National Laboratory | Miralda-Escude J.,Catalan Institution for Research and Advanced Studies | Miralda-Escude J.,Institute Of Ciencies Del Cosmos Ub Ieec
Journal of Cosmology and Astroparticle Physics | Year: 2012

Massive spectroscopic surveys of high-redshift quasars yield large numbers of correlated Lyα absorption spectra that can be used to measure large-scale structure. Simulations of these surveys are required to accurately interpret the measurements of correlations and correct for systematic errors. An efficient method to generate mock realizations of Lyα forest surveys is presented which generates a field over the lines of sight to the survey sources only, instead of having to generate it over the entire three-dimensional volume of the survey. The method can be calibrated to reproduce the power spectrum and one-point distribution function of the transmitted flux fraction, as well as the redshift evolution of these quantities, and is easily used for modeling any survey systematic effects. We present an example of how these mock surveys are applied to predict the measurement errors in a survey with similar parameters as the BOSS quasar survey in SDSS-III. © 2012 IOP Publishing Ltd and SISSA.

Vallely P.,University of Oklahoma | Moreno-Raya M.E.,CIEMAT | Baron E.,University of Oklahoma | Ruiz-Lapuente P.,Institute Fisica Fundamental | And 24 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016

We analyse a time series of optical spectra of SN 2014J from almost two weeks prior to maximum to nearly four months after maximum. We perform our analysis using the synow code, which is well suited to track the distribution of the ions with velocity in the ejecta. We show that almost all of the spectral features during the entire epoch can be identified with permitted transitions of the common ions found in normal supernovae (SNe) Ia in agreement with previous studies. We show that 2014J is a relatively normal SN Ia. At early times the spectral features are dominated by Si Ii, S Ii, Mg Ii, and Ca II. These ions persist to maximum light with the appearance of Na iand Mg i. At later times iron-group elements also appear, as expected in the stratified abundance model of the formation of normal Type Ia SNe. We do not find significant spectroscopic evidence for oxygen, until 100 d after maximum light. The +100 d identification of oxygen is tentative, and would imply significant mixing of unburned or only slight processed elements down to a velocity of 6000 kms-1. Our results are in relatively good agreement with other analyses in the infrared. We briefly compare SN 2011fe to SN 2014J and conclude that the differences could be due to different central densities at ignition or differences in the C/O ratio of the progenitors. © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Galbany L.,University of Chile | Moreno-Raya M.E.,CIEMAT | Ruiz-Lapuente P.,Institute Fisica Fundamental | Ruiz-Lapuente P.,Institute Of Ciencies Del Cosmos Ub Ieec | And 25 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016

We present the intensive spectroscopic follow up of the Type Ia supernova (SN Ia) 2014J in the starburst galaxy M82. Twenty-seven optical spectra have been acquired from 2014 January 22 to September 1 with the Isaac Newton and William Herschel Telescopes. After correcting the observations for the recession velocity of M82 and for MilkyWay and host galaxy extinction, we measured expansion velocities from spectral line blueshifts and pseudo-equivalent width of the strongest features in the spectra, which gives an idea on how elements are distributedwithin the ejecta.We position SN 2014J in the Benetti, Branch et al. andWang et al. diagrams. These diagrams are based on properties of the Si II features and provide dynamical and chemical information about the SN ejecta. The nearby SN 2011fe, which showed little evidence for reddening in its host galaxy, is shown as a reference for comparisons. SN 2014J is a border-line object between the Core-normal and Broad-line groups, which corresponds to an intermediate position between low-velocity gradient and high-velocity gradient objects. SN 2014J follows the R(Si II)-Δm15 correlation, which confirms its classification as a relatively normal SN Ia. Our description of the SN Ia in terms of the evolution of the pseudo-equivalent width of various ions as well as the position in the various diagrams put this specific SN Ia into the overall sample of SN Ia. © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Ruiz-Lapuente P.,Institute Fisica Fundamental | Ruiz-Lapuente P.,Max Planck Institute for Astrophysics | Ruiz-Lapuente P.,Institute Of Ciencies Del Cosmos Ub Ieec | The L.-S.,Clemson University | And 8 more authors.
Astrophysical Journal | Year: 2016

There has been much debate about the origin of the diffuse γ-ray background in the MeV range. At lower energies, AGNs and Seyfert galaxies can explain the background, but not above ≃0.3 MeV. Beyond ∼10 MeV blazars appear to account for the flux observed. That leaves an unexplained gap for which different candidates have been proposed, including annihilations of WIMPS. One candidate is Type Ia supernovae (SNe Ia). Early studies concluded that they were able to account for the γ-ray background in the gap, while later work attributed a significantly lower contribution to them. All those estimates were based on SN Ia explosion models that did not reflect the full 3D hydrodynamics of SN Ia explosions. In addition, new measurements obtained since 2010 have provided new, direct estimates of high-z SN Ia rates beyond z ∼ 2. We take into account these new advances to see the predicted contribution to the gamma-ray background. We use here a wide variety of explosion models and a plethora of new measurements of SN Ia rates. SNe Ia still fall short of the observed background. Only for a fit, which would imply ∼150% systematic error in detecting SN Ia events, do the theoretical predictions approach the observed fluxes. This fit is, however, at odds at the highest redshifts with recent SN Ia rate estimates. Other astrophysical sources such as flat-spectrum radio quasars do match the observed flux levels in the MeV regime, while SNe Ia make up to 30%-50% of the observed flux. © 2016. The American Astronomical Society. All rights reserved..

Villaescusa-Nanarro F.,University of Valencia | Miralda-Escude J.,Catalan Institution for Research and Advanced Studies | Miralda-Escude J.,Institute Of Ciencies Del Cosmos Ub Ieec | Pea-Garay C.,University of Valencia | Quilis V.,University of Valencia
Journal of Cosmology and Astroparticle Physics | Year: 2011

We study whether non-linear gravitational effects of relic neutrinos on the development of clustering and large-scale structure may be observable by weak gravitational lensing. We compute the density profile of relic massive neutrinos in a spherical model of a cluster of galaxies, for several neutrino mass schemes and cluster masses. Relic neutrinos add a small perturbation to the mass profile, making it more extended in the outer parts. In principle, this non-linear neutrino perturbation is detectable in an all-sky weak lensing survey such as EUCLID by averaging the shear profile of a large fraction of the visible massive clusters in the universe, or from its signature in the general weak lensing power spectrum or its cross-spectrum with galaxies. However, correctly modeling the distribution of mass in baryons and cold dark matter and suppressing any systematic errors to the accuracy required for detecting this neutrino perturbation is severely challenging. © 2011 IOP Publishing Ltd and SISSA.

Ruiz-Lapuente P.,Institute Fisica Fundamental | Ruiz-Lapuente P.,Institute Of Ciencies Del Cosmos Ub Ieec
New Astronomy Reviews | Year: 2014

Although Type Ia supernovae (SNe Ia) are a major tool in cosmology and play a key role in the chemical evolution of galaxies, the nature of their progenitor systems (apart from the fact that they must content at least one white dwarf, that explodes) remains largely unknown. In the last decade, considerable efforts have been made, both observationally and theoretically, to solve this problem. Observations have, however, revealed a previously unsuspected variety of events, ranging from very underluminous outbursts to clearly overluminous ones, and spanning a range well outside the peak luminosity-decline rate of the light curve relationship, used to make calibrated candles of the SNe Ia. On the theoretical side, new explosion scenarios, such as violent mergings of pairs of white dwarfs, have been explored. We review those recent developments, emphasizing the new observational findings, but also trying to tie them to the different scenarios and explosion mechanisms proposed thus far. © 2014 Elsevier B.V.

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