scholarly journals Action-space clustering of tidal streams to map the Galactic potential

2013 ◽  
Vol 9 (S298) ◽  
pp. 207-212 ◽  
Author(s):  
Robyn E. Sanderson ◽  
Amina Helmi ◽  
David W. Hogg
Keyword(s):  
Action Space ◽  
Leibler Divergence ◽  
Galactic Potential ◽  
Stellar Halo ◽  
Observational Errors ◽  
Tidal Streams ◽  
Potential Parameters ◽  
Best Fit ◽  
Membership Information ◽  
Input Potential

AbstractGiven a parametrized model of the Galactic potential, the best-fit parameters can be obtained by maximizing the Kullback-Leibler divergence of the action distribution of a set of stars initially clustered in action space (e.g. stars in tidal streams). This method will allow us to map the Milky Way's gravitational potential by simultaneously fitting multiple tidal streams without requiring stream membership information. With 20 streams of at least 20 stars each, including observational errors consistent with predictions for Gaia, this technique recovers the input potential parameters to a precision of 10-60% and an accuracy of 10%. With all the observed streams in our mock stellar halo (about 40) that fit the error criteria, the precision improves to 10%.

scholarly journals ACTION-SPACE CLUSTERING OF TIDAL STREAMS TO INFER THE GALACTIC POTENTIAL

2015 ◽  
Vol 801 (2) ◽  
pp. 98 ◽  
Author(s):  
Robyn E. Sanderson ◽  
Amina Helmi ◽  
David W. Hogg
Keyword(s):  
Action Space ◽  
Galactic Potential ◽  
Tidal Streams

scholarly journals Stream-orbit misalignment & a new algorithm for constraining the Galactic potential with streams

2013 ◽  
Vol 9 (S298) ◽  
pp. 195-200
Author(s):  
Jason L. Sanders ◽  
James Binney
Keyword(s):  
Action Space ◽  
Galactic Potential ◽  
Alternative Algorithm ◽  
Orbit Fitting ◽  
Tidal Stream ◽  
Tidal Streams

AbstractIn general, a tidal stream is misaligned with the orbit of its progenitor. Here we present the formation of tidal streams in angle-action space to discuss the effect of this misalignment on orbit-fitting algorithms for constraining the Galactic potential. We close by presenting and testing an alternative algorithm which more fully accounts for the dynamics of streams by using the angle-action formalism.

scholarly journals The stellar halo and tidal streams of Messier 63

2015 ◽  
Vol 454 (4) ◽  
pp. 3613-3621 ◽  
Author(s):  
Shawn M. Staudaher ◽  
Daniel A. Dale ◽  
Liese van Zee ◽  
Kate L. Barnes ◽  
David O. Cook
Keyword(s):  
Stellar Halo ◽  
Tidal Streams

scholarly journals A STATISTICAL METHOD FOR MEASURING THE GALACTIC POTENTIAL AND TESTING GRAVITY WITH COLD TIDAL STREAMS

2012 ◽  
Vol 760 (1) ◽  
pp. 2 ◽  
Author(s):  
Jorge Peñarrubia ◽  
Sergey E. Koposov ◽  
Matthew G. Walker
Keyword(s):  
Statistical Method ◽  
Galactic Potential ◽  
Tidal Streams

scholarly journals Convergent Bayesian global fits of 4D composite Higgs models

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Ethan Carragher ◽  
Will Handley ◽  
Daniel Murnane ◽  
Peter Stangl ◽  
Wei Su ◽  
...  
Keyword(s):  
Higgs Mass ◽  
Goldstone Boson ◽  
Fine Tuning ◽  
Collider Phenomenology ◽  
Parameter Spaces ◽  
Composite Higgs ◽  
Wide Range ◽  
Leibler Divergence ◽  
Future Collider ◽  
Best Fit

Abstract Models in which the Higgs boson is a composite pseudo-Nambu-Goldstone boson offer attractive solutions to the Higgs mass naturalness problem. We consider three such models based on the minimal SO(5) → SO(4) symmetry breaking pattern, and perform convergent global fits on the models under a Bayesian framework in order to find the regions of their parameter spaces that best fit a wide range of constraints, including recent Higgs measurements. We use a novel technique to analyse the fine-tuning of the models, quantifying the tuning as the Kullback-Leibler divergence from the prior to the posterior probability on the parameter space. Each model is found to be able to satisfy all constraints at the 3σ level simultaneously. As a by-product of the fits, we analyse the collider phenomenology of our models in these viable regions. In two of the three models, we find that the gg → H → γγ cross section is less than ∼90% that predicted by the SM, which is already in slight tension with experiment and could potentially be ruled out in the future high-luminosity run of the LHC. In addition, the lightest fermions F arising from the new strong dynamics in these models are seen in general to lie above ∼1.1 TeV, with the F → tW+ and F → $$ \overline{b}{W}^{+} $$ b ¯ W + decays offering particularly promising channels for probing these models in future collider searches.

Nucleon-nucleus velocity-dependent optical model: Revisited

2021 ◽  
Author(s):  
Sajedah Alalmeer ◽  
M I Jaghoub ◽  
Ibrahim Naji Ghabar
Keyword(s):  
Cross Sections ◽  
Mass Range ◽  
Angular Distributions ◽  
Polarization Data ◽  
Fitting Procedure ◽  
Wide Range ◽  
Local Equivalent ◽  
Potential Parameters ◽  
Best Fit ◽  
Good Agreement

Abstract In this work we study nucleon-nucleus elastic scattering using a nonlocal, velocity-dependent optical potential. The potential parameters are determined by fitting elastic angular distributions and polarization data for nucleon scattering off a wide range of nuclei falling in the mass range $12 \leq A \leq 208$ and over the energy range 10 - 60 MeV. Our potential parameters lead to smoothly varying local equivalent potentials and, unlike previous works, the potential depths corresponding to the real volume, imaginary surface, and imaginary volume terms show systematic linear dependences on energy. In addition, for each nuclear target, we determined constant sets of geometric parameters. Including the polarization data in the fitting procedure helped in reducing the large variations in the depths of the spin-orbit term. Our best-fit angular distributions and polarization data are in very good agreement with measured data, and are either as good as the cross sections obtained with widely-used systematics or better.

scholarly journals Determining distances to stars statistically from photometry

2012 ◽  
Vol 8 (S289) ◽  
pp. 74-81
Author(s):  
Heidi Jo Newberg
Keyword(s):  
Absolute Magnitude ◽  
Sloan Digital Sky Survey ◽  
Apparent Magnitude ◽  
Model Parameters ◽  
Computing Platform ◽  
Stellar Halo ◽  
Individual Star ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Tidal Streams

AbstractIn determining the distances to stars within the Milky Way galaxy, one often uses photometric or spectroscopic parallaxes. In these methods, the type of each individual star is determined, and the absolute magnitude of that star type is compared with the measured apparent magnitude to determine individual distances. In this paper, we define the term statistical photometric parallax, in which statistical knowledge of the absolute magnitudes of stellar populations is used to determine the underlying density distributions of those stars. This technique has been used to determine the density distribution of the Milky Way's stellar halo and its component tidal streams, using very large samples of stars from the Sloan Digital Sky Survey. Most recently, the volunteer computing platform MilkyWay@home has been used to find the best-fitting model parameters for the density of these halo stars.

scholarly journals Tidal Streams as Probes of the Galactic Potential

1999 ◽  
Vol 512 (2) ◽  
pp. L109-L112 ◽  
Author(s):  
Kathryn V. Johnston ◽  
HongSheng Zhao ◽  
David N. Spergel ◽  
Lars Hernquist
Keyword(s):  
Galactic Potential ◽  
Tidal Streams
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