- Shape and solar phase angle effects on the taxonomic classification of asteroids
- Carvano, J. M.; Davalos, J. A. G.
Context. The taxonomic classification of SDSS observations of asteroids show a dependency on the phase angle of the observations. Aims: We aim to quantify this dependence and use Hapke models to investigate its cause. Methods: Statistical method …
- Testing isotropy of cosmos with WMAP and PLANCK data
- Rath, Pranati K.; Samal, Pramoda Kumar
In recent years, there have been a large number of studies which support violation of statistical isotropy. Meanwhile, there are some studies which also found inconsistency. We use the power tensor method defined earlier in the literature to study t …
- Different studies of the global pitch angle of the Milky Way’s spiral arms
- Vallée, Jacques P.
There are many published values for the pitch angle of individual spiral arms, and their wide distribution (from -3° to -28°) begs for various attempts for a single value. Each of four statistical methods used here yields a mean pitch angle in a s …
- A maximum volume density estimator generalized over a proper motion-limited sample
- Lam, Marco C.; Rowell, Nicholas; Hambly, Nigel C.
The traditional Schmidt density estimator has been proven to be unbiased and effective in a magnitude-limited sample. Previously, efforts have been made to generalize it for populations with non-uniform density and proper motion-limited cases. This …
- The CIB-lensing bispectrum: impact on primordial non-Gaussianity and detectability for the Planck mission
- Curto, A.; Tucci, M.; Kunz, M.; Martínez-González, E.
We characterize the cosmic infrared background (CIB)-lensing bispectrum which is one of the contributions to the three-point functions of cosmic microwave background (CMB) maps in harmonic space. We show that the CIB-lensing bispectrum has a conside …
- Stellar populations in ω Centauri: a multivariate analysis
- Fraix-Burnet, D.; Davoust, E.
We have performed multivariate statistical analyses of photometric and chemical abundance parameters of three large samples of stars in the globular cluster ω Centauri. The statistical analysis of a sample of 735 stars based on seven chemical abund …
- Application of Multi-task Lasso Regression in the Parametrization of Stellar Spectra
- Chang, Li-Na; Zhang, Pei-Ai
The multi-task learning approaches have attracted the increasing attention in the fields of machine learning, computer vision, and artificial intelligence. By utilizing the correlations in tasks, learning multiple related tasks simultaneously is b …
- A New Method for Deriving the Stellar Birth Function of Resolved Stellar Populations.
- Gennaro, M.; Tchernyshyov, K.; Brown, T. M.; Gordon, K. D.
We present a new method for deriving the stellar birth function (SBF) of resolved stellar populations. The SBF (stars born per unit mass, time, and metallicity) is the combination of the initial mass function (IMF), the star formation history (SFH), …
- The Cannon: A Data-driven Approach to Stellar Label Determination
- Ness, M.; Hogg, David W.; Rix, H.-W.; Ho, Anna. Y. Q.; Zasowski, G.
New spectroscopic surveys offer the promise of stellar parameters and abundances (“stellar labels”) for hundreds of thousands of stars; this poses a formidable spectral modeling challenge. In many cases, there is a subset of reference objects fo …
- Hierarchical Probabilistic Inference of Cosmic Shear
- Schneider, Michael D.; Hogg, David W.; Marshall, Philip J.; Dawson, William A.; Meyers, Joshua; Bard, Deborah J.; Lang, Dustin
Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitatio …
- Bayesian Ages for Early-type Stars from Isochrones Including Rotation, and a Possible Old Age for the Hyades
- Brandt, Timothy D.; Huang, Chelsea X.
We combine recently computed models of stellar evolution using a new treatment of rotation with a Bayesian statistical framework to constrain the ages and other properties of early-type stars. We find good agreement for early-type stars and clusters …
- An improved method for object detection in astronomical images
- Zheng, Caixia; Pulido, Jesus; Thorman, Paul; Hamann, Bernd
This paper introduces an improved method for detecting objects of interest (galaxies and stars) in astronomical images. After applying a global detection scheme, further refinement is applied by dividing the entire image into several irregularly siz …
- A new method based on the subpixel Gaussian model for accurate estimation of asteroid coordinates
- Savanevych, V. E.; Briukhovetskyi, O. B.; Sokovikova, N. S.; Bezkrovny, M. M.; Vavilova, I. B.; Ivashchenko, Yu. M.; Elenin, L. V.; Khlamov, S. V.; Movsesian, Ia. S.; Dashkova, A. M.; Pogorelov, A. V.
We describe a new iteration method to estimate asteroid coordinates, based on a subpixel Gaussian model of the discrete object image. The method operates by continuous parameters (asteroid coordinates) in a discrete observational space (the set of p …
- An automated classification approach to ranking photospheric proxies of magnetic energy build-up
- Al-Ghraibah, A.; Boucheron, L. E.; McAteer, R. T. J.
Aims: We study the photospheric magnetic field of ~2000 active regions over solar cycle 23 to search for parameters that may be indicative of energy build-up and its subsequent release as a solar flare in the corona. Methods: We extract three sets …
- nIFTy cosmology: comparison of galaxy formation models
- Knebe, Alexander; Pearce, Frazer R.; Thomas, Peter A.; Benson, Andrew; Blaizot, Jeremy; Bower, Richard; Carretero, Jorge; Castander, Francisco J.; Cattaneo, Andrea; Cora, Sofia A.; Croton, Darren J.; Cui, Weiguang; Cunnama, Daniel; De Lucia, Gabriella; Devriendt, Julien E.; Elahi, Pascal J.; Font, Andreea; Fontanot, Fabio; Garcia-Bellido, Juan; Gargiulo, Ignacio D.; Gonzalez-Perez, Violeta; Helly, John; Henriques, Bruno; Hirschmann, Michaela; Lee, Jaehyun; Mamon, Gary A.; Monaco, Pierluigi; Onions, Julian; Padilla, Nelson D.; Power, Chris; Pujol, Arnau; Skibba, Ramin A.; Somerville, Rachel S.; Srisawat, Chaichalit; Vega-Martínez, Cristian A.; Yi, Sukyoung K.
We present a comparison of 14 galaxy formation models: 12 different semi-analytical models and 2 halo occupation distribution models for galaxy formation based upon the same cosmological simulation and merger tree information derived from it. The pa …
- Particle splitting in smoothed particle hydrodynamics based on Voronoi diagram
- Chiaki, Gen; Yoshida, Naoki
We present a novel method for particle splitting in smoothed particle hydrodynamics simulations. Our method utilizes the Voronoi diagram for a given particle set to determine the position of fine daughter particles. We perform several test simulatio …
- The Q Continuum Simulation: Harnessing the Power of GPU Accelerated Supercomputers
- Heitmann, Katrin; Frontiere, Nicholas; Sewell, Chris; Habib, Salman; Pope, Adrian; Finkel, Hal; Rizzi, Silvio; Insley, Joe; Bhattacharya, Suman
Modeling large-scale sky survey observations is a key driver for the continuing development of high-resolution, large-volume, cosmological simulations. We report the first results from the “Q Continuum” cosmological N-body simulation run carried …
- Block Time Step Storage Scheme for Astrophysical N-body Simulations
- Cai, Maxwell Xu; Meiron, Yohai; Kouwenhoven, M. B. N.; Assmann, Paulina; Spurzem, Rainer
Astrophysical research in recent decades has made significant progress thanks to the availability of various N-body simulation techniques. With the rapid development of high-performance computing technologies, modern simulations have been able to us …
- HELIOS-K: An Ultrafast, Open-source Opacity Calculator for Radiative Transfer
- Grimm, Simon L.; Heng, Kevin
We present an ultrafast opacity calculator that we name HELIOS-K. It takes a line list as an input, computes the shape of each spectral line, and provides an option for grouping an enormous number of lines into a manageable number of bins. We implem …
- NBODY6++GPU: ready for the gravitational million-body problem
- Wang, Long; Spurzem, Rainer; Aarseth, Sverre; Nitadori, Keigo; Berczik, Peter; Kouwenhoven, M. B. N.; Naab, Thorsten
Accurate direct N-body simulations help to obtain detailed information about the dynamical evolution of star clusters. They also enable comparisons with analytical models and Fokker-Planck or Monte Carlo methods. NBODY6 is a well-known direct N-body …