scholarly journals The dynamical matter density in the solar neighbourhood inferred from Gaia DR1

2018 ◽  
Vol 482 (1) ◽  
pp. 262-277 ◽  
Author(s):  
Axel Widmark ◽  
Giacomo Monari
Keyword(s):  
Matter Density ◽  
Solar Neighbourhood ◽  
Gaia Dr1

scholarly journals Kinematic structures found with Gaia DR1/TGAS and RAVE data in the Solar neighbourhood

2017 ◽  
Vol 13 (S334) ◽  
pp. 323-324
Author(s):  
I. Kushniruk ◽  
T. Schirmer ◽  
T. Bensby
Keyword(s):  
Wavelet Analysis ◽  
Velocity Distribution ◽  
Confidence Level ◽  
Solar Neighbourhood ◽  
Kinematic Structure ◽  
Proper Motions ◽  
Gaia Dr1

AbstractWith the much enlarged stellar sample of 55 831 stars and much increased precision in distances, proper motions, provided by Gaia DR1 TGAS we have shown with the help of the wavelet analysis that the velocity distribution of stars in the Solar neighbourhood contains more kinematic structures than previously known. We detect 19 kinematic structures between scales 3-16 km s−1 at the 3σ confidence level. Among them we identified well-known groups (such as Hercules, Sirius, Coma Berenices, Pleiades, and Wolf 630). We confirmed recently detected groups (such as Antoja12 and Bobylev16). In addition we report here about a new kinematic structure at (U, V) ≈ (37, 8) km s−1. Another three new groups are tentatively detected, but require confirmation.

scholarly journals The vertical force in the solar neighbourhood using red clump stars in TGAS and RAVE

2018 ◽  
Vol 615 ◽  
pp. A99 ◽  
Author(s):  
Jorrit H. J. Hagen ◽  
Amina Helmi
Keyword(s):  
Dark Matter ◽  
Galactic Plane ◽  
Radial Distance ◽  
Matter Density ◽  
Thick Disk ◽  
Solar Neighbourhood ◽  
Vertical Force ◽  
Dark Matter Density ◽  
Combining Data ◽  
Red Clump

Aims. We investigate the kinematics of red clump (RC) stars in the solar neighbourhood by combining data from Tycho-Gaia Astrometric Solution (TGAS) and Radial Velocity Experiment (RAVE) to constrain the local dark matter density. Methods. After calibrating the absolute magnitude of RC stars, we characterized their velocity distribution over a radial distance range of 6−10 kpc and up to 1.5 kpc away from the Galactic plane. We then applied the axisymmetric Jeans equations on subsets representing the thin and thick disks to determine the (local) distribution of mass near the disk of our Galaxy. Results. Our kinematic maps are well behaved, permitting a straightforward local determination of the vertical force, which we find to be Kzthin = − 2454 ± 619 (km s−1)2 kpc−1 and Kzthick = − 2141 ± 774 (km s−1)2 kpc−1 at 1.5 kpc away from the Galactic plane for the thin and thick disk samples and for thin and thick disk scale heights of 0.28 kpc and 1.12 kpc, respectively. These measurements can be translated into a local dark matter density ρDM ~ 0.018 ± 0.002 M⊙ pc−3. The systematic error on this estimate is much larger than the quoted statistical error, since even a 10% difference in the scale height of the thin disk leads to a 30% change in the value of ρDM and a nearly equally good fit to the data.

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

scholarly journals Cosmological model parameter dependence of the matter power spectrum covariance from the DEUS-PUR Cosmo simulations

2020 ◽  
Vol 500 (2) ◽  
pp. 2532-2542
Author(s):  
Linda Blot ◽  
Pier-Stefano Corasaniti ◽  
Yann Rasera ◽  
Shankar Agarwal
Keyword(s):  
Dark Energy ◽  
Power Spectrum ◽  
Cold Dark Matter ◽  
Matter Density ◽  
Density Fluctuations ◽  
Matrix Analysis ◽  
Model Parameter ◽  
Matter Power Spectrum ◽  
Non Gaussian ◽  
The Impact

ABSTRACT Future galaxy surveys will provide accurate measurements of the matter power spectrum across an unprecedented range of scales and redshifts. The analysis of these data will require one to accurately model the imprint of non-linearities of the matter density field. In particular, these induce a non-Gaussian contribution to the data covariance that needs to be properly taken into account to realize unbiased cosmological parameter inference analyses. Here, we study the cosmological dependence of the matter power spectrum covariance using a dedicated suite of N-body simulations, the Dark Energy Universe Simulation–Parallel Universe Runs (DEUS-PUR) Cosmo. These consist of 512 realizations for 10 different cosmologies where we vary the matter density Ωm, the amplitude of density fluctuations σ8, the reduced Hubble parameter h, and a constant dark energy equation of state w by approximately $10{{\ \rm per\ cent}}$. We use these data to evaluate the first and second derivatives of the power spectrum covariance with respect to a fiducial Λ-cold dark matter cosmology. We find that the variations can be as large as $150{{\ \rm per\ cent}}$ depending on the scale, redshift, and model parameter considered. By performing a Fisher matrix analysis we explore the impact of different choices in modelling the cosmological dependence of the covariance. Our results suggest that fixing the covariance to a fiducial cosmology can significantly affect the recovered parameter errors and that modelling the cosmological dependence of the variance while keeping the correlation coefficient fixed can alleviate the impact of this effect.

scholarly journals Birth sites of young stellar associations and recent star formation in a flocculent corrugated disc

2020 ◽  
Vol 499 (4) ◽  
pp. 5623-5640
Author(s):  
Alice C Quillen ◽  
Alex R Pettitt ◽  
Sukanya Chakrabarti ◽  
Yifan Zhang ◽  
Jonathan Gagné ◽  
...  
Keyword(s):  
Space Distribution ◽  
Solar Neighbourhood ◽  
Low Velocity ◽  
Stellar Association ◽  
Stellar Orbits ◽  
Pattern Speeds ◽  
Moving Groups ◽  
Orbit Integration ◽  
Stellar Associations ◽  
Spiral Arm

ABSTRACT With backwards orbit integration, we estimate birth locations of young stellar associations and moving groups identified in the solar neighbourhood that are younger than 70 Myr. The birth locations of most of these stellar associations are at a smaller galactocentric radius than the Sun, implying that their stars moved radially outwards after birth. Exceptions to this rule are the Argus and Octans associations, which formed outside the Sun’s galactocentric radius. Variations in birth heights of the stellar associations suggest that they were born in a filamentary and corrugated disc of molecular clouds, similar to that inferred from the current filamentary molecular cloud distribution and dust extinction maps. Multiple spiral arm features with different but near corotation pattern speeds and at different heights could account for the stellar association birth sites. We find that the young stellar associations are located in between peaks in the radial/tangential (UV) stellar velocity distribution for stars in the solar neighbourhood. This would be expected if they were born in a spiral arm, which perturbs stellar orbits that cross it. In contrast, stellar associations seem to be located near peaks in the vertical phase-space distribution, suggesting that the gas in which stellar associations are born moves vertically together with the low-velocity dispersion disc stars.

scholarly journals Dark matter candidates in a type-II radiative neutrino mass model

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Roberto A. Lineros ◽  
Mathias Pierre
Keyword(s):  
Dark Matter ◽  
Neutral Particle ◽  
Matter Density ◽  
Indirect Detection ◽  
Dark Matter Candidate ◽  
Neutrino Masses ◽  
Type Ii ◽  
Mass Model ◽  
Direct And Indirect Detection

Abstract We explore the connection between Dark Matter and neutrinos in a model inspired by radiative Type-II seessaw and scotogenic scenarios. In our model, we introduce new electroweakly charged states (scalars and a vector-like fermion) and impose a discrete ℤ2 symmetry. Neutrino masses are generated at the loop level and the lightest ℤ2-odd neutral particle is stable and it can play the role of a Dark Matter candidate. We perform a numerical analysis of the model showing that neutrino masses and flavour structure can be reproduced in addition to the correct dark matter density, with viable DM masses from 700 GeV to 30 TeV. We explore direct and indirect detection signatures and show interesting detection prospects by CTA, Darwin and KM3Net and highlight the complementarity between these observables.

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