Environmental effects on halo abundance and weak lensing peak statistics toward large underdense regions. (arXiv:1902.01503v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Higuchi_Y/0/1/0/all/0/1">Yuichi Higuchi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Inoue_K/0/1/0/all/0/1">Kaiki Taro Inoue</a> The cosmic microwave background (CMB) contains an anomalous cold spot with a surrounding hot ring, known as the Cold Spot. Inoue & Silk (2006) proposed that this feature could be explained by postulating a supervoid: if such a large underdense region exists, then the growth of matter perturbing around the spot might differ from the average value in the Universe and the differences might affect weak lensing analysis of peak statistics. To investigate environmental effects on halo number count and peak statistics,Read More →

Model for a Noise Matched Phased Array Feed. (arXiv:1902.01515v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Roshi_D/0/1/0/all/0/1">D. Anish Roshi</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Shillue_W/0/1/0/all/0/1">W. Shillue</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Fisher_J/0/1/0/all/0/1">J. Richard Fisher</a> (2) (1. National Astronomy and Ionosphere Center, Arecibo Observatory, Arecibo, 2. National Radio Astronomy Observatory, Charlottesville) We present a model for a Noise Matched Phased Array Feed (PAF) system and compare model predictions with the measurement results. The PAF system consists of an array feed, a receiver, a beamformer and a parabolic reflector. The novel aspect of our model is the characterization of the {em PAF system} by a single matrix. This characteristic matrix is constructed from the open-circuit voltage covariance atRead More →

A Model for Phased Array Feed. (arXiv:1902.01516v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Roshi_D/0/1/0/all/0/1">D. Anish Roshi</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Fisher_J/0/1/0/all/0/1">J. Richard Fisher</a> (1) (1. National Radio Astronomy Observatory, Charlottesville, USA) In this report we present a model for phased array feed (PAF) and compare the model predictions with measurements. A theory for loss-less PAF is presented first. To develop the theory we ask the question — what is the best $T_{sys}/eta_{ap}$ that can be achieved when a PAF is used on a telescope to observe a source at an angle $theta_s, phi_s$ from the boresight direction ? We show that a characteristic matrix for the {em system} (i.e. PAF+telescope+receiver) canRead More →

Phased Array Feed Model Equations corresponding to two definitions of embedded beam pattern. (arXiv:1902.01517v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Roshi_D/0/1/0/all/0/1">D. Anish Roshi</a> (National Radio Astronomy Observatory, Charlottesville, USA) In this report, we present the phased array feed (PAF) model equations for two definitions of embedded beam patterns. In Roshi & Fisher (2016), we presented the PAF model by defining the embedded beam pattern as the beam pattern due to a 1 V excitation to one port and all other ports short circuited. This embedded beam pattern is referred to as voltage-embedded-beam (VEB). The embedded beam pattern can also be defined as the beam pattern due to a 1Read More →

ESA is Planning a Mission to the Smallest Spacerock Ever Visited: the Moon of an Asteroid For some small minority of humans, Death By Asteroid is a desirable fate. The idea probably satisfies their wonky Doomsday thinking. But for the rest of us, going out the same way the dinosaurs did would just be embarrassing. Thankfully, the ESA’s Hera mission will visit the smallest spacerock ever, and will help us avoid … Continue reading “ESA is Planning a Mission to the Smallest Spacerock Ever Visited: the Moon of an Asteroid” The post ESA is Planning a Mission to the Smallest Spacerock Ever Visited: the MoonRead More →

Weekly Space Hangout: Feb 6, 2019: Dr. Natalie Hinkel and “The Hypatia Catalog” Hosts: Fraser Cain (universetoday.com / @fcain) Dr. Paul M. Sutter (pmsutter.com / @PaulMattSutter) Dr. Kimberly Cartier (KimberlyCartier.org / @AstroKimCartier ) Dr. Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg & ChartYourWorld.org) Dr. Natalie Hinkel is a Planetary Astrophysicist at the Southwest Research Institute and a co-investigator for the Nexus for Exoplanet System Science (NExSS) research network at Arizona … Continue reading “Weekly Space Hangout: Feb 6, 2019: Dr. Natalie Hinkel and “The Hypatia Catalog”” The post Weekly Space Hangout: Feb 6, 2019: Dr. Natalie Hinkel and “The Hypatia Catalog” appeared first on Universe Today. UniverseRead More →

Bubbles of Brand New Stars This dazzling region of newly-forming stars in the Large Magellanic Cloud (LMC) was captured by the Multi Unit Spectroscopic Explorer instrument (MUSE) on ESO’s Very Large Telescope. The relatively small amount of dust in the LMC and MUSE’s acute vision allowed intricate details of the region to be picked out in visible light. ESO News Feed Go to SourceRead More →

A Closer Look at Some Gas-Phase Depletions in the ISM: Trends for O, Ge, and Kr vs. $F_*$, $f({rm H}_2)$, and Starlight Intensity. (arXiv:1902.01521v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Jenkins_E/0/1/0/all/0/1">Edward B. Jenkins</a> In a survey of archived ultraviolet spectra of 100 stars recorded by the echelle spectrograph of the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), we measure the strengths of the weak absorption features of O I, Ge II and Kr I in the interstellar medium. Our objective is to undertake an investigation that goes beyond earlier abundance studies to see how these elements are influenced independently by three different environmental properties: (1)Read More →

Climbing Halo Merger Trees with TreeFrog. (arXiv:1902.01527v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Elahi_P/0/1/0/all/0/1">Pascal J. Elahi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Poulton_R/0/1/0/all/0/1">Rhys J.J. Poulton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tobar_R/0/1/0/all/0/1">Rodrigo J. Tobar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lagos_C/0/1/0/all/0/1">Claudia del P. Lagos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Power_C/0/1/0/all/0/1">Chris Power</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Robotham_A/0/1/0/all/0/1">Aaron S.G. Robotham</a> We present TreeFrog, a massively parallel halo merger tree builder that is capable comparing different halo catalogues and producing halo merger trees. The code is written in c++11, use the MPI and OpenMP API’s for parallelisation, and includes python tools to read/manipulate the data products produced. The code correlates binding energy sorted particle ID lists between halo catalogues, determining optimal descendant/progenitor matches using multiple snapshots, a merit function that maximises the number ofRead More →

Detectability of modulated X-rays from LISA’s supermassive black hole mergers. (arXiv:1902.01538v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Canton_T/0/1/0/all/0/1">Tito Dal Canton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mangiagli_A/0/1/0/all/0/1">Alberto Mangiagli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Noble_S/0/1/0/all/0/1">Scott C. Noble</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schnittman_J/0/1/0/all/0/1">Jeremy Schnittman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ptak_A/0/1/0/all/0/1">Andy Ptak</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Klein_A/0/1/0/all/0/1">Antoine Klein</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sesana_A/0/1/0/all/0/1">Alberto Sesana</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Camp_J/0/1/0/all/0/1">Jordan Camp</a> One of the central goals of LISA is the detection of gravitational waves from the merger of supermassive black holes. Contrary to stellar-mass black hole mergers, such events are expected to be rich X-ray sources due to the accretion of material from the circumbinary disks onto the black holes. The orbital dynamics before merger is also expected to modulate the resulting X-ray emission via Doppler boosting inRead More →

Local Stability of Galactic Discs in Modified Dynamics. (arXiv:1902.01555v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Shenavar_H/0/1/0/all/0/1">Hossein Shenavar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ghafourian_N/0/1/0/all/0/1">Neda Ghafourian</a> The local stability of stellar and fluid discs, under a new modified dynamical model, is surveyed by using WKB approximation. The exact form of the modified Toomre criterion is derived for both types of systems and it is shown that the new model is, in all situations, more locally stable than Newtonian model. In addition, it has been proved that the central surface density of the galaxies plays an important role in the local stability in the sense that LSB galaxies are more stable than HSBs. Furthermore, the growthRead More →

Search for transient gravitational wave signals associated with magnetar bursts during Advanced LIGO’s second observing run. (arXiv:1902.01557v1 [astro-ph.HE]) The <a href="http://arxiv.org/find/astro-ph/1/au:+Collaboration_LIGO_Scientific/0/1/0/all/0/1">LIGO Scientific Collaboration</a>, the <a href="http://arxiv.org/find/astro-ph/1/au:+Collaboration_Virgo/0/1/0/all/0/1">Virgo Collaboration</a>: <a href="http://arxiv.org/find/astro-ph/1/au:+Abbott_B/0/1/0/all/0/1">B. P. Abbott</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abbott_R/0/1/0/all/0/1">R. Abbott</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abbott_T/0/1/0/all/0/1">T. D. Abbott</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abraham_S/0/1/0/all/0/1">S. Abraham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Acernese_F/0/1/0/all/0/1">F. Acernese</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ackley_K/0/1/0/all/0/1">K. Ackley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Adams_C/0/1/0/all/0/1">C. Adams</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Adhikari_R/0/1/0/all/0/1">R. X. Adhikari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Adya_V/0/1/0/all/0/1">V. B. Adya</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Affeldt_C/0/1/0/all/0/1">C. Affeldt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Agathos_M/0/1/0/all/0/1">M. Agathos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Agatsuma_K/0/1/0/all/0/1">K. Agatsuma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aggarwal_N/0/1/0/all/0/1">N. Aggarwal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aguiar_O/0/1/0/all/0/1">O. D. Aguiar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aiello_L/0/1/0/all/0/1">L. Aiello</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ain_A/0/1/0/all/0/1">A. Ain</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ajith_P/0/1/0/all/0/1">P. Ajith</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Allen_G/0/1/0/all/0/1">G. Allen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Allocca_A/0/1/0/all/0/1">A. Allocca</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aloy_M/0/1/0/all/0/1">M. A. Aloy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Altin_P/0/1/0/all/0/1">P. A. Altin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Amato_A/0/1/0/all/0/1">A. Amato</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ananyeva_A/0/1/0/all/0/1">A. Ananyeva</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Anderson_S/0/1/0/all/0/1">S.Read More →

Global analysis of luminosity- and colour-dependent galaxy clustering in the Sloan Digital Sky Survey. (arXiv:1902.01566v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Paul_N/0/1/0/all/0/1">Niladri Paul</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pahwa_I/0/1/0/all/0/1">Isha Pahwa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paranjape_A/0/1/0/all/0/1">Aseem Paranjape</a> We present a Halo Occupation Distribution (HOD) analysis of the luminosity- and colour-dependent galaxy clustering in the Sloan Digital Sky Survey. A novelty of our technique is that it uses a combination of clustering measurements in luminosity bins to perform a global likelihood analysis, simultaneously constraining the HOD parameters for a range of luminosity thresholds. We present simple, smooth fitting functions which accurately describe the resulting luminosity dependence of the best-fit HOD parameters. To minimise systematic halo modelling effects, weRead More →

The Escape Fraction of Ionizing Photons During the Epoch of Reionization: Observability with the Square Kilometre Array. (arXiv:1902.01611v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Seiler_J/0/1/0/all/0/1">Jacob Seiler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hutter_A/0/1/0/all/0/1">Anne Hutter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sinha_M/0/1/0/all/0/1">Manodeep Sinha</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Croton_D/0/1/0/all/0/1">Darren Croton</a> One of the most important parameters in characterising the Epoch of Reionization, the escape fraction of ionizing photons, $f_mathrm{esc}$, remains unconstrained both observationally and theoretically. With recent work highlighting the impact of galaxy-scale feedback on the instantaneous value of $f_mathrm{esc}$, it is important to develop a model reionization is self-consistently coupled to galaxy evolution. In this work, we present such a model and explore how physically motivated functional forms of $f_mathrm{esc}$ affect the evolutionRead More →

The nature of Els”{a}sser variables in compressible MHD. (arXiv:1902.01619v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Magyar_N/0/1/0/all/0/1">N. Magyar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Doorsselaere_T/0/1/0/all/0/1">T. Van Doorsselaere</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goossens_M/0/1/0/all/0/1">M. Goossens</a> The Els”{a}sser variables are often used in studies of plasma turbulence, in helping differentiate between MHD waves propagating parallel or anti-parallel to the main magnetic field. While for pure Alfv’en waves in a homogeneous plasma the method is strictly valid, we show that compressible, magnetoacoustic waves are in general described by both Els”{a}sser variables. Furthermore, in a compressible and inhomogeneous plasma, the pure MHD waves (Alfv’en, fast and slow) are no longer normal modes, but waves become linearly coupled or display mixed properties of Alfv’enRead More →

Sharp gap edges in dense planetary rings: An axisymmetric diffusion model. (arXiv:1902.01627v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Gratz_F/0/1/0/all/0/1">Fabio Gr&#xe4;tz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Seiss_M/0/1/0/all/0/1">Martin Sei&#xdf;</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schmidt_J/0/1/0/all/0/1">J&#xfc;rgen Schmidt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Colwell_J/0/1/0/all/0/1">Joshua Colwell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Spahn_F/0/1/0/all/0/1">Frank Spahn</a> One of the most intriguing facets of Saturn’s rings are the sharp edges of gaps in the rings where the surface density abruptly drops to zero. This is despite of the fact that the range over which a moon transfers angular momentum onto the ring material is much larger. Recent UVIS-scans of the edges of the Encke and Keeler gap show that this drop occurs over a range approximately equal to the rings’ thickness. Borderies et al.Read More →

An ancient and a primordial collisional family as the main sources of X-type asteroids of the inner Main Belt. (arXiv:1902.01633v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Delbo_M/0/1/0/all/0/1">Marco Delbo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Avdellidou_C/0/1/0/all/0/1">Chrysa Avdellidou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Morbidelli_A/0/1/0/all/0/1">Alessandro Morbidelli</a> The near-Earth asteroid population suggests the existence of an inner Main Belt source of asteroids that belongs to the spectroscopic X-complex and has moderate albedos. The identification of such a source has been lacking so far. We argue that the most probable source is one or more collisional asteroid families that escaped discovery up to now. We apply a novel method to search for asteroid families in the inner Main Belt population of asteroids belongingRead More →

CCD and DSLR maxima of RR Lyrae stars in 2016 and 2017. (arXiv:1902.01634v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Hirosawa_K/0/1/0/all/0/1">K. Hirosawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Borgne_J/0/1/0/all/0/1">J.F. Le Borgne</a> We present here maximum timings of RR Lyrae stars observed in 2016 and 2017 by VSOLJ member Kenji Hirosawa. The calculation of the time of maximum from the measurements provided by the observer have been made in the frame of the GEOS RR Lyr survey. We present here maximum timings of RR Lyrae stars observed in 2016 and 2017 by VSOLJ member Kenji Hirosawa. The calculation of the time of maximum from the measurements provided by the observer have been made in the frameRead More →

Energetics of magnetic transients in solar active region plage. (arXiv:1902.01650v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Chitta_L/0/1/0/all/0/1">L. P. Chitta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sukarmadji_A/0/1/0/all/0/1">A. R. C. Sukarmadji</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Voort_L/0/1/0/all/0/1">L. Rouppe van der Voort</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Peter_H/0/1/0/all/0/1">H. Peter</a> Densely packed coronal loops are rooted in plages in the vicinity of active regions on the Sun. The photospheric magnetic features underlying these plage areas are patches of mostly unidirectional magnetic field extending several acrsec on the solar surface. To explore the transient nature of magnetic field, its mixed-polarity characteristics and the associated energetics in plages using high spatial resolution observations and numerical simulations. We use photospheric Fe I 6173,AA spectropolarimetric observations of a decaying activeRead More →

Probing restarting activity in hard X-ray selected giant radio galaxies. (arXiv:1902.01657v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Bruni_G/0/1/0/all/0/1">G. Bruni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ursini_F/0/1/0/all/0/1">F. Ursini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Panessa_F/0/1/0/all/0/1">F. Panessa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bassani_L/0/1/0/all/0/1">L. Bassani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bazzano_A/0/1/0/all/0/1">A. Bazzano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bird_A/0/1/0/all/0/1">A.J. Bird</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chiaraluce_E/0/1/0/all/0/1">E. Chiaraluce</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dallacasa_D/0/1/0/all/0/1">D. Dallacasa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fiocchi_M/0/1/0/all/0/1">M. Fiocchi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Giroletti_M/0/1/0/all/0/1">M. Giroletti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hernandez_Garcia_L/0/1/0/all/0/1">L. Hernandez-Garcia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malizia_A/0/1/0/all/0/1">A. Malizia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Molina_M/0/1/0/all/0/1">M. Molina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Saripalli_L/0/1/0/all/0/1">L. Saripalli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ubertini_P/0/1/0/all/0/1">P. Ubertini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Venturi_T/0/1/0/all/0/1">T. Venturi</a> With their sizes larger than 0.7 Mpc, Giant Radio Galaxies (GRGs) are the largest individual objects in the Universe. To date, the reason why they reach such enormous extensions is still unclear. One of the proposed scenarios suggests that they are the result of multipleRead More →