The Stellar Number Density Distribution in the Local Solar Neighborhood is North-South Asymmetric

Abstract

We study the number density distribution of a sample of K and M dwarf stars, matched North and South of the Galactic plane within a distance of 2 kpc from the sun, using observations from the Ninth Data Release of the Sloan Digital Sky Survey. We determine distances using the photometric parallax method, and in this context systematic effects exist which could potentially impact the determination of the number density profile with height from the Galactic plane --- and ultimately affect a number density North-South asymmetry. They include: (i) the calibration of the various photometric parallax relations, (ii) the ability to separate dwarfs from giants in our sample, (iii) the role of stellar population differences such as age and metallicity, (iv) the ability to determine the offset of the sun from the Galactic plane, and (v) the correction for reddening from dust in the Galactic plane, though our stars are at high Galactic latitudes. We find the various analyzed systematic effects to have a negligible impact on our observed asymmetry, and using a new and larger sample of stars we confirm and refine the earlier discovery of Widrow et al. of a significant Galactic North-South asymmetry in the stellar number density distribution.

23 pages, 25 figures, update to match Journal version: 2013 ApJ 777, 91

References in corpus (8)

• The Milky Way Tomography with SDSS: II. Stellar Metallicity
• Stellar SEDs from 0.3-2.5 Microns: Tracing the Stellar Locus and Searching for Color Outliers in SDSS and 2MASS
• On the local dark matter density
• The SEGUE Stellar Parameter Pipeline. II. Validation with Galactic Globular and Open Clusters
• The Distances to Open Clusters from Main-Sequence Fitting. III. Improved Accuracy with Empirically Calibrated Isochrones
• A new determination of the local dark matter density from the kinematics of K dwarfs
• Tracing Sagittarius Structure with SDSS and SEGUE Imaging and Spectroscopy
• An Improved Photometric Calibration of the Sloan Digital Sky Survey Imaging Data

Cited by in corpus (64)

• The Local Dark Matter Density
• Vertical waves in the solar neighbourhood in Gaia DR2
• Rings and Radial Waves in the Disk of the Milky Way
• The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry and location
• A Large Catalog of Accurate Distances to Molecular Clouds from PS1 Photometry
• Dark matter local density determination: recent observations and future prospects
• Bending and Breathing Modes of the Galactic Disk
• Radial and vertical flows induced by galactic spiral arms: likely contributors to our "wobbly Galaxy''
• Galactic seismology: the evolving "phase spiral" after the Sagittarius dwarf impact
• Warps and waves in the stellar discs of the Auriga cosmological simulations
• Gaia Early Data Release 3: The Galactic anticentre
• Constraining a Thin Dark Matter Disk with Gaia
• A Tail of Two Populations: Chemo-dynamics of the Sagittarius Stream and Implications for its Original Mass
• A fully cosmological model of a Monoceros-like ring
• Modelling the Galactic disc: perturbed distribution functions in the presence of spiral arms
• Excitation of coupled stellar motions in the Galactic Disk by orbiting satellites
• Emergence of the Gaia Phase Space Spirals from Bending Waves
• The Vertical Structure and Kinematics of Grand Design Spirals
• Detecting Dark Matter Substructures around the Milky Way with Gaia
• Stellar mass distribution and star formation history of the Galactic disk revealed by mono-age stellar populations from LAMOST
• Bending Waves in the Milky Way's disc from halo substructure
• Measuring the local dark matter density with LAMOST DR5 and Gaia DR2
• The vertical effects of disc non-axisymmetries from perturbation theory: the case of the Galactic bar
• Mapping the Monoceros Ring in 3D with Pan-STARRS1
• Gravitational scattering of stars and clusters and the heating of the Galactic disk
• Galactoseismology and the Local Density of Dark Matter
• Kinematics and dynamics of Gaia red clump stars
• The Milky Way's Shell Structure Reveals the Time of a Radial Collision
• Exploring the pertubed Milky Way disk and the substructures of the outer disk
• The Stellar Distribution Function and Local Vertical Potential from Gaia DR2
• Spontaneous generation of bending waves in isolated Milky Way-like discs
• Milky Way Red Dwarfs in the BoRG Survey; Galactic scale-height and the distribution of dwarfs stars in WFC3 imaging
• Milky Way Tomography with K and M Dwarf Stars: the Vertical Structure of the Galactic Disk
• Did Sgr cause the vertical waves in the solar neighbourhood?
• Constraining the Galactic structure parameters with the XSTPS-GAC and SDSS photometric surveys
• A Comprehensive Perturbative Formalism for Phase-Mixing in Perturbed Disks. I. Phase spirals in an Infinite, Isothermal Slab
• Galactic seismology: joint evolution of impact-triggered stellar and gaseous disc corrugations
• Vertical Oscillations of Fluid and Stellar Disks
• Mapping Milky Way disk perturbations in stellar number density and vertical velocity using Gaia DR3
• Swing Amplification and the Gaia Phase Spirals
• Age dissection of the vertical breathing motions in Gaia DR2: evidence for spiral driving
• The Great Wave: Evidence of a large-scale vertical corrugation propagating outwards in the Galactic disc
• Eigenfunctions of Galactic Phase Space Spirals from Dynamic Mode Decomposition
• A new resonance-like feature in the outer disc of the Milky Way
• Bending waves excited by irregular gas inflow along warps
• The Milky Way, Coming into Focus: Precision Astrometry Probes its Evolution, and its Dark Matter
• A Map of the Local Velocity Substructure in the Milky Way Disk
• A Bayesian Approach to the Vertical Structure of the Disk of the Milky Way
• The North/South Asymmetry of the Galaxy: Possible Connection to the Vertical Phase Space Snail
• Residuals of an Equilibrium Model for the Galaxy Reveal a State of Disequilibrium in the Solar Neighborhood
• Asymmetric Mean Metallicity Distribution of the Milky Way's Disk
• A non-uniform distribution of the nearest brown dwarfs
• Applying Noether's theorem to matter in the Milky Way: evidence for external perturbations and non-steady-state effects from Gaia Data Release 2
• Fractal properties of stellar systems and random forces
• Stellar Tidal Streams in External Galaxies
• Probing Axial Symmetry Breaking in the Galaxy with Gaia Data Release 2
• A method to calculate the local density distribution of the Galaxy from the Tycho-Gaia Astrometric Solution data
• Non-equilibrium in the Solar Neighbourhood using dynamical modelling with Gaia DR2
• Axial Asymmetry Studies in Gaia Data Release 2 Yield the Pattern Speed of the Galactic Bar
• Introduction to Tidal Streams
• Two-point correlation function studies for the Milky Way: discovery of spatial clustering from disk excitations and substructure
• The Vertical Displacement of the Milky Way Disk
• A Wave-Corrected Assessment of the Local Midplane
• Bending Waves in Velocity Space: a First Look at the THINGS sample