RAS_WEB (Page 2,254)

Rapid Parameter Estimation of Gravitational Waves from Binary Neutron Star Coalescence using Focused Reduced Order Quadrature. (arXiv:2007.09108v2 [gr-qc] UPDATED) <a href="http://arxiv.org/find/gr-qc/1/au:+Morisaki_S/0/1/0/all/0/1">Soichiro Morisaki</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Raymond_V/0/1/0/all/0/1">Vivien Raymond</a> Rapid parameter estimation of gravitational waves from binary neutron star coalescence, in particular accurate sky localisation in minutes after the initial detection stage, is crucial for the success of multi-messenger observations. One of the techniques to speed up the parameter estimation, which has been applied for the production analysis of the LIGO-Virgo collaboration, is reduced order quadrature (ROQ). While it speeds up parameter estimation significantly, the time required is still on the order of hours. Focusing on the fact thatRead More →

Imprint of anisotropic primordial non-Gaussianity on halo intrinsic alignments in simulations. (arXiv:2007.03670v2 [astro-ph.CO] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Akitsu_K/0/1/0/all/0/1">Kazuyuki Akitsu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kurita_T/0/1/0/all/0/1">Toshiki Kurita</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nishimichi_T/0/1/0/all/0/1">Takahiro Nishimichi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Takada_M/0/1/0/all/0/1">Masahiro Takada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tanaka_S/0/1/0/all/0/1">Satoshi Tanaka</a> Using $N$-body simulations of cosmological large-scale structure formation, for the first time, we show that the anisotropic primordial non-Gaussianity (PNG) causes a scale-dependent modification, given by $1/k^2$ at small $k$ limit, in the three-dimensional power spectra of halo shapes (intrinsic alignments), whilst the conventional power spectrum of halo number density field remains unaffected. We discuss that wide-area imaging and spectrocopic surveys observing the same region of the sky allow us to constrain the quadrupole PNG coefficientRead More →

Black hole pair production on cosmic strings in the presence of a background magnetic field. (arXiv:2006.16983v2 [hep-th] UPDATED) <a href="http://arxiv.org/find/hep-th/1/au:+Ashoorioon_A/0/1/0/all/0/1">Amjad Ashoorioon</a>, <a href="http://arxiv.org/find/hep-th/1/au:+Poshteh_M/0/1/0/all/0/1">Mohammad Bagher Jahani Poshteh</a> We investigate the pair creation of magnetically charged black holes on a cosmic string in the presence of a background magnetic field. The string may either break or fray to produce a pair of accelerating black holes described by Ernst metric. By using the instanton action we obtain the rate of such production. For large values of background magnetic field the production of large black holes is probable. Comparing our results with the case of black hole pair creationRead More →

Easing cosmic tensions with an open and hotter universe. (arXiv:2006.16149v3 [astro-ph.CO] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Bose_B/0/1/0/all/0/1">Benjamin Bose</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lombriser_L/0/1/0/all/0/1">Lucas Lombriser</a> Despite the great observational success of the standard cosmological model some discrepancies in the inferred parameter constraints have manifested among a number of cosmological data sets. These include a tension between the expansion rate of our Cosmos as inferred from the cosmic microwave background (CMB) and as found from local measurements, the preference for an enhanced amplitude of CMB lensing, a somewhat low quadrupole moment of the CMB fluctuations as well as a preference for a lower amplitude of matter fluctuations in large-scale structure surveys than inferredRead More →

Using gradient boosting regression to improve ambient solar wind model predictions. (arXiv:2006.12835v3 [physics.space-ph] UPDATED) <a href="http://arxiv.org/find/physics/1/au:+Bailey_R/0/1/0/all/0/1">R. L. Bailey</a>, <a href="http://arxiv.org/find/physics/1/au:+Reiss_M/0/1/0/all/0/1">M. A. Reiss</a>, <a href="http://arxiv.org/find/physics/1/au:+Arge_C/0/1/0/all/0/1">C. N. Arge</a>, <a href="http://arxiv.org/find/physics/1/au:+Mostl_C/0/1/0/all/0/1">C. M&#xf6;stl</a>, <a href="http://arxiv.org/find/physics/1/au:+Owens_M/0/1/0/all/0/1">M. J. Owens</a>, <a href="http://arxiv.org/find/physics/1/au:+Amerstorfer_U/0/1/0/all/0/1">U. V. Amerstorfer</a>, <a href="http://arxiv.org/find/physics/1/au:+Henney_C/0/1/0/all/0/1">C. J. Henney</a>, <a href="http://arxiv.org/find/physics/1/au:+Amerstorfer_T/0/1/0/all/0/1">T. Amerstorfer</a>, <a href="http://arxiv.org/find/physics/1/au:+Weiss_A/0/1/0/all/0/1">A. J. Weiss</a>, <a href="http://arxiv.org/find/physics/1/au:+Hinterreiter_J/0/1/0/all/0/1">J. Hinterreiter</a> Studying the ambient solar wind, a continuous pressure-driven plasma flow emanating from our Sun, is an important component of space weather research. The ambient solar wind flows in interplanetary space determine how solar storms evolve through the heliosphere before reaching Earth, and especially during solar minimum are themselves a driver of activity in theRead More →

The anisotropy of the power spectrum in periodic cosmological simulations. (arXiv:2006.10399v2 [astro-ph.CO] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Racz_G/0/1/0/all/0/1">G&#xe1;bor R&#xe1;cz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Szapudi_I/0/1/0/all/0/1">Istv&#xe1;n Szapudi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Csabai_I/0/1/0/all/0/1">Istv&#xe1;n Csabai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dobos_L/0/1/0/all/0/1">L&#xe1;szl&#xf3; Dobos</a> The classical gravitational force on a torus is anisotropic and always lower than Newton’s $1/r^2$ law. We demonstrate the effects of periodicity in dark matter only $N$-body simulations of spherical collapse and standard $Lambda$CDM initial conditions. Periodic boundary conditions cause an overall negative and anisotropic bias in cosmological simulations of cosmic structure formation. The lower amplitude of power spectra of small periodic simulations are a consequence of the missing large scale modes and the equally important smaller periodic forces. TheRead More →

Tomographic Constraints on Gravity from Angular Redshift Fluctuations in the Late Universe. (arXiv:2005.06568v2 [astro-ph.CO] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Hernandez_Monteagudo_C/0/1/0/all/0/1">Carlos Hern&#xe1;ndez-Monteagudo</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Chaves_Montero_J/0/1/0/all/0/1">Jon&#xe1;s Chaves-Montero</a> (2 and 1), <a href="http://arxiv.org/find/astro-ph/1/au:+Angulo_R/0/1/0/all/0/1">Ra&#xfa;l E. Angulo</a> (3 and 4), <a href="http://arxiv.org/find/astro-ph/1/au:+Arico_G/0/1/0/all/0/1">Giovanni Aric&#xf2;</a> (3 and 1) ((1) CEFCA, (2) ANL, (3) DIPC, (4) IKERBASQUE) Fluctuations in sky maps of the galaxy redshifts, dubbed as angular redshift fluctuations (ARF), contain precise information about the growth rate of structures and the nature of gravity in the Universe. Specifically, ARF constrain the combination of cosmological parameters $H/H_0,fsigma_8(z)$, while being an intrinsically tomographic probe and largely insensitive to many observational systematic errors, all this without requiring theRead More →

Gravitational wave signature from phase transition of a combusting neutron star to quark star. (arXiv:2003.00693v2 [astro-ph.HE] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Mallick_R/0/1/0/all/0/1">Ritam Mallick</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Singh_S/0/1/0/all/0/1">Shailendra Singh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Prasad_R/0/1/0/all/0/1">R Prasad</a> Fluctuation at the neutron star center gives rise to a small deconfined quark core very close to the star center. The density discontinuity at the quark-hadron boundary initiates a shock wave, which propagates outwards of the star. The shock has enough energy to combust nuclear matter to 2-flavor quark matter in the star. The 2-flavor quark matter is not stable and settles to a stable 3-flavor matter in the weakly interacting timescale. In this paper, we study the conversionRead More →

A response to criticisms on “CMB Constraints Cast a Shadow on CSL Model”. (arXiv:2010.04067v2 [gr-qc] UPDATED) <a href="http://arxiv.org/find/gr-qc/1/au:+Martin_J/0/1/0/all/0/1">Jerome Martin</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Vennin_V/0/1/0/all/0/1">Vincent Vennin</a> Our recent letter “Cosmic Microwave Background Constraints Cast a Shadow On Continuous Spontaneous Localization Models” [arXiv:1906.04405] has recently been criticised in [G. R. Bengochea, G. Leon, P. Pearle, and D. Sudarsky, arXiv:2008.05285, see also arXiv:2006.05313]. In this reply, we explain why the arguments presented in those articles are either incorrect or a confirmation of the robustness of our results. Our recent letter “Cosmic Microwave Background Constraints Cast a Shadow On Continuous Spontaneous Localization Models” [arXiv:1906.04405] has recently been criticised in [G. R. Bengochea,Read More →

Density Weighted Angular Redshift Fluctuations: a New Cosmological Observable. (arXiv:1911.12056v2 [astro-ph.CO] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Hernandez_Monteagudo_C/0/1/0/all/0/1">Carlos Hernandez-Monteagudo</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Chaves_Montero_J/0/1/0/all/0/1">Jonas Chaves-Montero</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Angulo_R/0/1/0/all/0/1">Raul E. Angulo</a> (3) ((1) CEFCA, (2) ANL, (3) DIPC) We propose the use of angular fluctuations in the galaxy redshift field as a new way to extract cosmological information in the Universe. This new probe $delta z (hat{n})$ consists on the statistics of sky maps built by projecting redshifts under a Gaussian window of width $sigma_z$ centred upon a redshift $z_{rm obs}$, and weighted by the galaxy density field. We compute the angular power spectrum of the $delta z (hat{n})$ field in bothRead More →

Prospects for Observing the low-density Cosmic Web in Lyman-alpha Emission. (arXiv:1905.06954v3 [astro-ph.GA] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Witstok_J/0/1/0/all/0/1">Joris Witstok</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Puchwein_E/0/1/0/all/0/1">Ewald Puchwein</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kulkarni_G/0/1/0/all/0/1">Girish Kulkarni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smit_R/0/1/0/all/0/1">Renske Smit</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haehnelt_M/0/1/0/all/0/1">Martin G. Haehnelt</a> Mapping the intergalactic medium (IGM) in Lyman-$alpha$ emission would yield unprecedented tomographic information on the large-scale distribution of baryons and potentially provide new constraints on the UV background and various feedback processes relevant to galaxy formation. Here, we use a cosmological hydrodynamical simulation to examine the Lyman-$alpha$ emission of the IGM due to collisional excitations and recombinations in the presence of a UV background. We focus on gas in large-scale-structure filaments in which Lyman-$alpha$ radiative transferRead More →

Sparse Image Reconstruction for the SPIDER Optical Interferometric Telescope. (arXiv:1903.05638v3 [astro-ph.IM] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Pratley_L/0/1/0/all/0/1">Luke Pratley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McEwen_J/0/1/0/all/0/1">Jason D. McEwen</a> The concept of a recently proposed small-scale interferometric optical imaging device, an instrument known as the Segmented Planar Imaging Detector for Electro-optical Reconnaissance (SPIDER), is of great interest for its possible applications in astronomy and space science. Due to low weight, low power consumption, and high resolution, the SPIDER telescope could replace the large space telescopes that exist today. Unlike traditional optical interferometry the SPIDER accurately retrieves both phase and amplitude information, making the measurement process analogous to a radio interferometer. State of the art sparseRead More →

Kinematics beats dust: unveiling nested substructure in the perturbed outer disc of the Milky Way. (arXiv:2103.12737v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Laporte_C/0/1/0/all/0/1">Chervin F. P. Laporte</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koposov_S/0/1/0/all/0/1">Sergey E. Koposov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Belokurov_V/0/1/0/all/0/1">Vasily Belokurov</a> We use $Gaia$ eDR3 data and legacy spectroscopic surveys to map the Milky Way disc substructure towards the Galactic Anticenter at heliocentric distances $dgeq10,rm{kpc}$. We report the discovery of multiple previously undetected new filaments embedded in the outer disc in highly extincted regions. Stars in these over-densities have distance gradients expected for disc material and move on disc-like orbits with $v_{phi}sim170-230,rm{km,s^{-1}}$, showing small spreads in energy. Such a morphology argues against a quiescently growing Galactic thinRead More →

Metallicity-dependent wind parameter predictions for OB stars. (arXiv:2103.12736v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Vink_J/0/1/0/all/0/1">Jorick S. Vink</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sander_A/0/1/0/all/0/1">Andreas A.C. Sander</a> (Armagh Observatory and Planetarium) Mass-loss rates and terminal wind velocities are key parameters that determine the kinetic wind energy and momenta of massive stars. Furthermore, accurate mass-loss rates determine the mass and rotational velocity evolution of mass stars, and their fates as neutron stars and black holes in function of metallicity (Z). Here we update our Monte Carlo mass-loss Recipe with new dynamically-consistent computations of the terminal wind velocity — as a function of Z. These predictions are particularly timely as the HST ULLYSES project will observe ultravioletRead More →

Science Commissioning of NIHTS: The Near-infrared High Throughput Spectrograph on the Lowell Discovery Telescope. (arXiv:2103.12722v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Gustafsson_A/0/1/0/all/0/1">Annika Gustafsson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moskovitz_N/0/1/0/all/0/1">Nicholas Moskovitz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cushing_M/0/1/0/all/0/1">Michael C. Cushing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bida_T/0/1/0/all/0/1">Thomas A. Bida</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dunham_E/0/1/0/all/0/1">Edward W. Dunham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Roe_H/0/1/0/all/0/1">Henry Roe</a> The Near-Infrared High Throughput Spectrograph (NIHTS) is in operation on the 4.3 m Lowell Discovery Telescope (LDT) in Happy Jack, AZ. NIHTS is a low-resolution spectrograph (R~200) that operates from 0.86 to 2.45 microns. NIHTS is fed by a custom dichroic mirror which reflects near-infrared wavelengths to the spectrograph and transmits the visible to enable simultaneous imaging with the Large Monolithic Imager (LMI), an independent visible wavelength camera.Read More →

Improved Lemaitre-Tolman model and the mass and turn-around radius in group of galaxies. (arXiv:2103.12714v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Popolo_A/0/1/0/all/0/1">Antonino Del Popolo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deliyergiyev_M/0/1/0/all/0/1">Maksym Deliyergiyev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chan_M/0/1/0/all/0/1">Man Ho Chan</a> We extended the modified Lemaitre-Tolman model taking into account the effect of angular momentum and dynamical friction. The inclusion of these quantities in the equation of motion modifies the evolution of a perturbation, initially moving with the Hubble flow. Solving the equation of motions we got the relationships between mass, $M$, and the turn-around radius, $R_0$. Knowing $R_0$, the quoted relation allows the determination of the mass of the object studied. The relationships for the case in which alsoRead More →

The dust mass in Cassiopeia A from infrared and optical line flux differences. (arXiv:2103.12705v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Niculescu_Duvaz_M/0/1/0/all/0/1">Maria Niculescu-Duvaz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barlow_M/0/1/0/all/0/1">Michael J. Barlow</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bevan_A/0/1/0/all/0/1">Antonia Bevan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Milisavljevic_D/0/1/0/all/0/1">Danny Milisavljevic</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Looze_I/0/1/0/all/0/1">Ilse De Looze</a> The large quantities of dust that have been found in a number of high redshift galaxies have led to suggestions that core-collapse supernovae (CCSNe) are the main sources of their dust and have motivated the measurement of the dust masses formed by local CCSNe. For Cassiopeia~A, an oxygen-rich remnant of a Type~IIb CCSN, a dust mass of 0.6-1.1~M$_odot$ has already been determined by two different methods, namely (a) from its far-infrared spectral energyRead More →

Inverse Chameleon Mechanism and Mass Limits for Compact Stars. (arXiv:2103.12696v1 [gr-qc]) <a href="http://arxiv.org/find/gr-qc/1/au:+Wei_H/0/1/0/all/0/1">Hao Wei</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Yu_Z/0/1/0/all/0/1">Zhong-Xi Yu</a> As is well known, there are various mass limits for compact stars. For example, the maximum mass for non-rotating white dwarfs is given by the famous Chandrasekhar limit about $1.4 M_odot$ (solar masses). Although the mass limit for neutron stars is not so clear to date, one of the widely accepted values is about $2.1 M_odot,$. Recently, challenges to these mass limits appeared. Motivated by the super-Chandrasekhar mass white dwarfs with masses up to $2.4 sim 2.8 M_odot,$, and compact objects (probably neutron stars) in the mass gapRead More →

A model-independent test of the evolution of gas depletion factor for SPT-SZ and Planck ESZ clusters. (arXiv:2103.12695v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Bora_K/0/1/0/all/0/1">Kamal Bora</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Desai_S/0/1/0/all/0/1">Shantanu Desai</a> The gas mass fraction in galaxy clusters has been widely used to determine cosmological parameters. This method assumes that the ratio of the cluster gas mass fraction to the cosmic baryon fraction ($gamma(z)$) is constant as a function of redshift. In this work, we look for a time evolution of $gamma(z)$ at $R_{500}$ by using both the SPT-SZ and Planck Early SZ (ESZ) cluster data, in a model-independent fashion without any explicit dependence on the underlying cosmology. For this calculation, weRead More →

Ion heating and flow driven by an Instability found in Plasma Couette Flow. (arXiv:2103.12657v1 [physics.plasm-ph]) <a href="http://arxiv.org/find/physics/1/au:+Milhone_J/0/1/0/all/0/1">J. Milhone</a>, <a href="http://arxiv.org/find/physics/1/au:+Flanagan_K/0/1/0/all/0/1">K. Flanagan</a>, <a href="http://arxiv.org/find/physics/1/au:+Egedal_J/0/1/0/all/0/1">J. Egedal</a>, <a href="http://arxiv.org/find/physics/1/au:+Endrizzi_D/0/1/0/all/0/1">D. Endrizzi</a>, <a href="http://arxiv.org/find/physics/1/au:+Olson_J/0/1/0/all/0/1">J. Olson</a>, <a href="http://arxiv.org/find/physics/1/au:+Peterson_E/0/1/0/all/0/1">E.E. Peterson</a>, <a href="http://arxiv.org/find/physics/1/au:+Wright_J/0/1/0/all/0/1">J.C. Wright</a>, <a href="http://arxiv.org/find/physics/1/au:+Forest_C/0/1/0/all/0/1">C.B. Forest</a> We present the first observation of instability in weakly magnetized, pressure dominated plasma Couette flow firmly in the Hall regime. Strong Hall currents couple to a low frequency electromagnetic mode that is driven by high-$beta$ ($>1$) pressure profiles. Spectroscopic measurements show heating (factor of 3) of the cold, unmagnetized ions via a resonant Landau damping process. A linear theory of this instability is derived that predictsRead More →