scholarly journals NIHAO-UHD: The properties of MW-like stellar disks in high resolution cosmological simulations

2019 ◽  
Author(s):  
Tobias Buck ◽  
Aura Obreja ◽  
Andrea V Macciò ◽  
Ivan Minchev ◽  
Aaron A Dutton ◽  
...  
Keyword(s):  
Milky Way ◽  
General Structure ◽  
Stellar Mass ◽  
Scale Height ◽  
Stellar Disk ◽  
Galactic Disks ◽  
Cosmological Simulations ◽  
Hydrodynamical Simulations ◽  
Single Exponential ◽  
Scale Length

Abstract Simulating thin and extended galactic disks has long been a challenge in computational astrophysics. We introduce the NIHAO-UHD suite of cosmological hydrodynamical simulations of Milky Way mass galaxies and study stellar disk properties such as stellar mass, size and rotation velocity which agree well with observations of the Milky Way and local galaxies. In particular, the simulations reproduce the age-velocity dispersion relation and a multi-component stellar disk as observed for the Milky Way. Half of our galaxies show a double exponential vertical profile, while the others are well described by a single exponential model which we link to the disk merger history. In all cases, mono-age populations follow a single exponential whose scale height varies monotonically with stellar age and radius. The scale length decreases with stellar age while the scale height increases. The general structure of the stellar disks is already set at time of birth as a result of the inside-out and upside-down formation. Subsequent evolution modifies this structure by increasing both the scale length and height of all mono-age populations. Thus, our results put tight constraints on how much dynamical memory stellar disks can retain over cosmological timescales. Our simulations demonstrate that it is possible to form thin galactic disks in cosmological simulations provided there are no significant stellar mergers at low redshifts. Most of the stellar mass is formed in-situ with only a few percent ($\lesssim 5\%$) brought in by merging satellites at early times. Redshift zero snapshots and halo catalogues are publicly available.

scholarly journals Cold Dark Matter Substructure and the Heating of Galactic Disks

2003 ◽  
Vol 208 ◽  
pp. 391-392
Author(s):  
Andreea S. Font ◽  
Julio F. Navarro
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dark Matter Halo ◽  
Stellar Disk ◽  
Minor Role ◽  
Galactic Disks ◽  
Cosmological Simulations ◽  
A Minor

We investigate recent suggestions that substructure in cold dark matter (CDM) halos has potentially destructive effects on galactic disks. N-body simulations of disk/bulge models of the Milky Way, embedded in a dark matter halo with substructure similar to that found in cosmological simulations, show that tides from substructure halos play only a minor role in the dynamical heating of the stellar disk. This suggests that substructure might not preclude CDM halos from being acceptable hosts of thin stellar disks.

scholarly journals The radial extent of the Galactic thick disk

2016 ◽  
Vol 11 (S321) ◽  
pp. 3-5
Author(s):  
Thomas Bensby
Keyword(s):  
Milky Way ◽  
Galactic Disk ◽  
Thin Disk ◽  
Thick Disk ◽  
Stellar Disk ◽  
Chemical Signatures ◽  
Radial Extent ◽  
Thin And Thick Disks ◽  
Thick Disks ◽  
Scale Length

AbstractBased on observational data from the fourth internal data release of the Gaia-ESO Survey we probe the abundance structure in the Milky Way stellar disk as a function of galactocentric radius and height above the plane. We find that the inner and outer Galactic disks have different chemical signatures. The stars in the inner Galactic disk show abundance signatures of both the thin and thick disks, while the stars in the outer Galactic disk resemble in majority the abundances seen in the thin disk. Assuming that the Galactic thick disk can be associated with the α-enriched population, this can be interpreted as that the thick disk density drops drastically beyond a galactocentric radius of about 10 kpc. This is in agreement with recent findings that the thick disk has a short scale-length, shorter than that of the the thin disk.

scholarly journals Modelling the outskirts of galaxies in a cosmological context

2016 ◽  
Vol 11 (S321) ◽  
pp. 69-71
Author(s):  
Andrew P. Cooper
Keyword(s):  
Surface Brightness ◽  
Milky Way ◽  
State Of The Art ◽  
Mass Function ◽  
Stellar Mass ◽  
Current Data ◽  
Cosmological Simulations ◽  
Cosmological Context ◽  
Profile Amplitude

AbstractCurrent data broadly support trends of galaxy surface brightness profile amplitude and shape with total stellar mass predicted by state-of-the-art ΛCDM cosmological simulations, although recent results show signs of interesting discrepancies, particularly for galaxies less massive than the Milky Way. Here I discuss how perhaps the largest contribution to such discrepancies can be inferred almost directly from how well a given model agrees with the observed present-day galaxy stellar mass function.

scholarly journals The stellar disk component: distribution, motions, age and stellar composition

1985 ◽  
Vol 106 ◽  
pp. 133-142
Author(s):  
Gösta Lyngå
Keyword(s):  
Radial Velocity ◽  
Milky Way ◽  
Scale Height ◽  
Open Clusters ◽  
Stellar Disk ◽  
Component Distribution ◽  
Disk Component ◽  
Linear Diameter

The distribution of the stellar disk component is studied with particular emphasis on the properties of open clusters. A scale height of 80 pc is found for clusters younger than 109 years while the scale height is 200 pc for older clusters. A radial metallicity gradient in the disk is confirmed but there seem to be significant abundance variations apart from this. There are radial gradients in age as well as in linear diameter. Kinematically, there are a number of regions in the Milky Way with systematic radial velocity residuals.

scholarly journals Revisiting the Planet Mass and Stellar Metallicity Relation for Low-Mass Exoplanets Orbiting GKM Class Stars

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 88
Author(s):  
Jonathan H. Jiang ◽  
Daniel Zhao ◽  
Xuan Ji ◽  
Bohan Xie ◽  
Kristen A. Fahy
Keyword(s):  
Uncertainty Analysis ◽  
Stellar Mass ◽  
Observational Evidence ◽  
Statistical Characteristics ◽  
Stellar Disk ◽  
Exponential Law ◽  
Spectral Class ◽  
Low Mass ◽  
M Stars

The growing database of exoplanets has shown us the statistical characteristics of various exoplanet populations, providing insight towards their origins. Observational evidence suggests that the process by which gas giants are conceived in the stellar disk may be disparate from that of smaller planets. Using NASA’s Exoplanet Archive, we analyzed the relationships between planet mass and stellar metallicity, as well as planet mass and stellar mass for low-mass exoplanets (MP < 0.13 MJ) orbiting spectral class G, K, and M stars. We performed further uncertainty analysis to confirm that the exponential law relationships found between the planet mass, stellar mass, and the stellar metallicity cannot be fully explained by observation biases alone.

scholarly journals The role of faint population III supernovae in forming CEMP stars in ultra-faint dwarf galaxies

2021 ◽  
Author(s):  
Myoungwon Jeon ◽  
Volker Bromm ◽  
Gurtina Besla ◽  
Jinmi Yoon ◽  
Yumi Choi
Keyword(s):  
Milky Way ◽  
Dwarf Galaxies ◽  
Mass Resolution ◽  
Explosion Energy ◽  
High Carbon ◽  
Cosmological Simulations ◽  
Carbon Abundance ◽  
The Absolute ◽  
Zoom In

Abstract CEMP-no stars, a subset of carbon enhanced metal poor (CEMP) stars ($\rm [C/Fe]\ge 0.7$ and $\rm [Fe/H]\lesssim -1$) have been discovered in ultra-faint dwarf (UFD) galaxies, with Mvir ≈ 108 M⊙ and M* ≈ 103 − 104 M⊙ at z = 0, as well as in the halo of the Milky Way (MW). These CEMP-no stars are local fossils that may reflect the properties of the first (Pop III) and second (Pop II) generation of stars. However, cosmological simulations have struggled to reproduce the observed level of carbon enhancement of the known CEMP-no stars. Here we present new cosmological hydrodynamic zoom-in simulations of isolated UFDs that achieve a gas mass resolution of mgas ≈ 60 M⊙. We include enrichment from Pop III faint supernovae (SNe), with ESN = 0.6 × 1051 erg, to understand the origin of CEMP-no stars. We confirm that Pop III and Pop II stars are mainly responsible for the formation of CEMP and C-normal stars respectively. New to this study, we find that a majority of CEMP-no stars in the observed UFDs and the MW halo can be explained by Pop III SNe with normal explosion energy (ESN = 1.2 × 1051 erg) and Pop II enrichment, but faint SNe might also be needed to produce CEMP-no stars with $\rm [C/Fe]\gtrsim 2$, corresponding to the absolute carbon abundance of $\rm A(C)\gtrsim 6.0$. Furthermore, we find that while we create CEMP-no stars with high carbon ratio $\rm [C/Fe]\approx 3-4$, by adopting faint SNe, it is still challenging to reproduce CEMP-no stars with extreme level of carbon abundance of $\rm A(C)\approx 7.0-7.5$, observed both in the MW halo and UFDs.

scholarly journals The anisotropy of the power spectrum in periodic cosmological simulations

2021 ◽  
Vol 503 (4) ◽  
pp. 5638-5645
Author(s):  
Gábor Rácz ◽  
István Szapudi ◽  
István Csabai ◽  
László Dobos
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Power Spectra ◽  
Cosmological Simulations ◽  
Spherical Collapse ◽  
Lower Amplitude ◽  
Hydrodynamical Simulations

ABSTRACT The classical gravitational force on a torus is anisotropic and always lower than Newton’s 1/r2 law. We demonstrate the effects of periodicity in dark matter only N-body simulations of spherical collapse and standard Lambda cold dark matter (ΛCDM) initial conditions. Periodic boundary conditions cause an overall negative and anisotropic bias in cosmological simulations of cosmic structure formation. The lower amplitude of power spectra of small periodic simulations is a consequence of the missing large-scale modes and the equally important smaller periodic forces. The effect is most significant when the largest mildly non-linear scales are comparable to the linear size of the simulation box, as often is the case for high-resolution hydrodynamical simulations. Spherical collapse morphs into a shape similar to an octahedron. The anisotropic growth distorts the large-scale ΛCDM dark matter structures. We introduce the direction-dependent power spectrum invariant under the octahedral group of the simulation volume and show that the results break spherical symmetry.

scholarly journals The mass of the Milky Way out to 100 kpc using halo stars

2020 ◽  
Author(s):  
Alis J Deason ◽  
Denis Erkal ◽  
Vasily Belokurov ◽  
Azadeh Fattahi ◽  
Facundo A Gómez ◽  
...  
Keyword(s):  
Distribution Function ◽  
Mass Concentration ◽  
Milky Way ◽  
Function Analysis ◽  
Large Magellanic Cloud ◽  
Systematic Bias ◽  
Cosmological Simulations ◽  
Halo Stars ◽  
Systematic Effects ◽  
Mass Estimate

Abstract We use a distribution function analysis to estimate the mass of the Milky Way out to 100 kpc using a large sample of halo stars. These stars are compiled from the literature, and the vast majority ($\sim \! 98\%$) have 6D phase-space information. We pay particular attention to systematic effects, such as the dynamical influence of the Large Magellanic Cloud (LMC), and the effect of unrelaxed substructure. The LMC biases the (pre-LMC infall) halo mass estimates towards higher values, while realistic stellar halos from cosmological simulations tend to underestimate the true halo mass. After applying our method to the Milky Way data we find a mass within 100 kpc of M( &lt; 100kpc) = 6.07 ± 0.29(stat.) ± 1.21(sys.) × 1011M⊙. For this estimate, we have approximately corrected for the reflex motion induced by the LMC using the Erkal et al. model, which assumes a rigid potential for the LMC and MW. Furthermore, stars that likely belong to the Sagittarius stream are removed, and we include a 5% systematic bias, and a 20% systematic uncertainty based on our tests with cosmological simulations. Assuming the mass-concentration relation for Navarro-Frenk-White haloes, our mass estimate favours a total (pre-LMC infall) Milky Way mass of M200c = 1.01 ± 0.24 × 1012M⊙, or (post-LMC infall) mass of M200c = 1.16 ± 0.24 × 1012 M⊙ when a 1.5 × 1011M⊙ mass of a rigid LMC is included.

Disk Heating: Comparing the Milky Way with Cosmological Simulations

2010 ◽  
Author(s):  
Elisa L. House ◽  
Chris B. Brook ◽  
Brad K. Gibson ◽  
Victor P. Debattista ◽  
C. C. Popescu
Keyword(s):  
Milky Way ◽  
Cosmological Simulations

scholarly journals The local rotation curve of the Milky Way based on SEGUE and RAVE data

2018 ◽  
Vol 614 ◽  
pp. A63 ◽  
Author(s):  
K. Sysoliatina ◽  
A. Just ◽  
O. Golubov ◽  
Q. A. Parker ◽  
E. K. Grebel ◽  
...  
Keyword(s):  
Rotation Curve ◽  
Milky Way ◽  
Tangential Velocity ◽  
Solar Radius ◽  
Tangential Component ◽  
Peculiar Velocity ◽  
Thick Disc ◽  
Thin Disc ◽  
Peculiar Motion ◽  
Scale Length

Aims. We construct the rotation curve of the Milky Way in the extended solar neighbourhood using a sample of Sloan Extension for Galactic Understanding and Exploration (SEGUE) G-dwarfs. We investigate the rotation curve shape for the presence of any peculiarities just outside the solar radius as has been reported by some authors. Methods. Using the modified Strömberg relation and the most recent data from the RAdial Velocity Experiment (RAVE), we determine the solar peculiar velocity and the radial scale lengths for the three populations of different metallicities representing the Galactic thin disc. Subsequently, with the same binning in metallicity for the SEGUE G-dwarfs, we construct the rotation curve for a range of Galactocentric distances from 7 to 10 kpc. We approach this problem in a framework of classical Jeans analysis and derive the circular velocity by correcting the mean tangential velocity for the asymmetric drift in each distance bin. With SEGUE data we also calculate the radial scale length of the thick disc taking as known the derived peculiar motion of the Sun and the slope of the rotation curve. Results. The tangential component of the solar peculiar velocity is found to be V ⊙ = 4.47 ± 0.8 km s−1 and the corresponding scale lengths from the RAVE data are Rd(0 < [Fe/H] < 0.2) = 2.07 ± 0.2 kpc, Rd(−0.2 < [Fe/H] < 0) = 2.28 ± 0.26 kpc and Rd(−0.5 < [Fe/H] <−0.2) = 3.05 ± 0.43 kpc. In terms of the asymmetric drift, the thin disc SEGUE stars are demonstrated to have dynamics similar to the thin disc RAVE stars, therefore the scale lengths calculated from the SEGUE sample have close values: Rd(0 < [Fe/H] < 0.2) = 1.91 ± 0.23 kpc, Rd(−0.2 < [Fe/H] < 0) = 2.51 ± 0.25 kpc and Rd(−0.5 < [Fe/H] <−0.2) = 3.55 ± 0.42 kpc. The rotation curve constructed through SEGUE G-dwarfs appears to be smooth in the selected radial range 7 kpc < R < 10 kpc. The inferred power law index of the rotation curve is 0.033 ± 0.034, which corresponds to a local slope of dV c∕dR = 0.98 ± 1 km s−1 kpc−1. The radial scale length of the thick disc is 2.05 kpc with no essential dependence on metallicity. Conclusions. The local kinematics of the thin disc rotation as determined in the framework of our new careful analysis does not favour the presence of a massive overdensity ring just outside the solar radius. We also find values for solar peculiar motion, radial scale lengths of thick disc, and three thin disc populations of different metallicities as a side result of this work.

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