scholarly journals Color Profiles of Disk Galaxies since z ~ 1: Probing Outer Disk Formation Scenarios

2008 ◽  
Vol 679 (2) ◽  
pp. L69-L72 ◽  
Author(s):  
R. Azzollini ◽  
I. Trujillo ◽  
J. E. Beckman
Keyword(s):  
Disk Galaxies ◽  
Disk Formation ◽  
Outer Disk

The first 200 kyr of the Solar System: making the planetary material diversity

2018 ◽  
Vol 14 (S345) ◽  
pp. 137-140
Author(s):  
Francesco C. Pignatale ◽  
Sébastien Charnoz ◽  
Marc Chaussidon ◽  
Emmanuel Jacquet
Keyword(s):  
Refractory Material ◽  
Thermal Processing ◽  
Large Scale ◽  
Transport Processes ◽  
Heterogeneous Distribution ◽  
Disk Formation ◽  
Outer Disk ◽  
Thermal Histories ◽  
High And Low Temperatures ◽  
Compositional Diversity

AbstractChondrites are made of a mixture of solids formed at high and low temperatures. This heterogeneity was thought to be produced by large scale transport processes in the Sun’s isolated accretion disk. However, mounting evidences suggest that refractory inclusions in chondrites were produced together with the disk formation.We present numerical simulations of the formation and transport of rocky materials during the collapse of the Solar Nebula’s parent cloud and the consequent disk assembling.We find that the interplay between the cloud collapse, the dynamics of gas and dust and thermal processing of different species in the disk, results in a local mixing of solids with different thermal histories. Our simulations return an heterogeneous distribution of refractory material with higher concentration in the outer disk. This refractory material has a short formation timescales, during the first tens of kyr of the Sun (class 0-I). Our results open new frontiers into the origin of the compositional diversity of chondrites.

Galactic archaeology: Understanding the metallicity gradients with chemo-dynamical models

2018 ◽  
Vol 14 (A30) ◽  
pp. 253-254
Author(s):  
I. Minchev ◽  
F. Anders ◽  
C. Chiappini
Keyword(s):  
Interstellar Medium ◽  
Milky Way ◽  
Cosmic Time ◽  
Dynamical Evolution ◽  
Disk Galaxies ◽  
Dynamical Models ◽  
Disk Formation ◽  
Recent Method ◽  
Gradient Evolution ◽  
Inside Out

AbstractRadial metallicity gradients measured today in the interstellar medium (ISM) and stellar components of disk galaxies are the result of chemo-dynamical evolution since the beginning of disk formation. This makes it difficult to infer the disk past without knowledge of the ISM metallicity gradient evolution with cosmic time. We show that abundance gradients are meaningful only if stellar age information is available. The observed gradient inversion with distance from the disk mid-plane seen in the Milky Way can be explained as the effect of inside-out disk formation and disk flaring of mono-age populations. A novel recent method is presented for constraining the evolution of the Galactic ISM metallicity with radius and time directly from the observations, while at the same time recovering the birth radii of any stellar sample with precise metallicity and age measurements.

scholarly journals The Mass Distribution in Disk Galaxies

2015 ◽  
Vol 11 (A29B) ◽  
pp. 195-196
Author(s):  
Stéphane Courteau ◽  
Aaron A. Dutton
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Spiral Galaxies ◽  
Formation Mechanisms ◽  
Disk Galaxies ◽  
Outer Disk ◽  
Mass Fractions ◽  
Low Mass ◽  
The Mean ◽  
Inner Parts

AbstractWe present the relative fraction of baryons and dark matter at various radii in galaxies. For spiral galaxies, this fraction measured in a galaxy's inner parts is typically baryon-dominated (maximal) and dark-matter dominated (sub-maximal) in the outskirts. The transition from maximal to sub-maximal baryons occurs within the inner parts of low-mass disk galaxies (with Vtot ≤ 200 km s−1) and in the outer disk for more massive systems. The mean mass fractions for late- and early-type galaxies vary significantly at the same fiducial radius and circular velocity, suggesting a range of galaxy formation mechanisms. A more detailed discussion, and resolution of the so-called “maximal disk problem”, is presented in Courteau & Dutton, ApJL, 801, 20.

scholarly journals Observable Consequences of Triaxial Halos

1987 ◽  
Vol 117 ◽  
pp. 303-313 ◽  
Author(s):  
James Binney
Keyword(s):  
Elliptical Galaxies ◽  
Disk Galaxies ◽  
Early Type ◽  
Disk Formation ◽  
Principal Axes

Heavy halos are probably not axisymmetric. During disk formation, the visible parts of disk galaxies are likely to have aligned their principal axes with those of the surrounding halos, but it is less clear that early-type galaxies are aligned with their halos. Triaxial halos may possibly sustain, or even excite, the warps often seen in the outer parts of disks. Polar rings and ripples around elliptical galaxies provide promising probes of the triaxiality of halo potentials.

scholarly journals Simulating Disk Galaxies: First Results of a Systematical Study

2006 ◽  
Vol 2 (S235) ◽  
pp. 114-114 ◽  
Author(s):  
Franziska Köckert ◽  
Matthias Steinmetz
Keyword(s):  
Angular Momentum ◽  
Galaxy Formation ◽  
Initial Conditions ◽  
Disk Galaxies ◽  
Disk Formation ◽  
Numerical Resolution ◽  
First Results ◽  
Low Mass ◽  
Current Paradigm ◽  
Made In

Simulating disk galaxies within the current paradigm of galaxy formation has been a long standing problem. In comparison with observations, the simulated disks were too small and too centrally concentrated, due to a large loss of angular momentum during formation. This is known as the angular momentum catastrophe (Navarro & Benz (1991)). Recently, some progress has been made in reducing this effect by changing the cosmology, including various feedback mechanisms, improving numerical resolution and carefully selecting initial conditions with a quiet merging history after z≈2. Unfortunately, it remains unclear which of these effects, or which combination, has resulted in more realistic disk formation. In order to address this problem, we conduct a systematical study using the N-body code GADGET2 (Springel (2005)). We adopt a flat ΛCDM cosmology with Ωm=0.3, ΩΛ=0.7, Ωbar=0.04 and h=0.65. Using a softening of 0.5 kpc we find disks with a very compact unresolved gas clump in the center and a thin, extended disk (R≈10kpc) of very low mass around it.

scholarly journals Color Profiles of Spiral Galaxies: Clues on Outer-Disk Formation Scenarios

2008 ◽  
Vol 683 (2) ◽  
pp. L103-L106 ◽  
Author(s):  
Judit Bakos ◽  
Ignacio Trujillo ◽  
Michael Pohlen
Keyword(s):  
Spiral Galaxies ◽  
Disk Formation ◽  
Outer Disk

scholarly journals A Model for a Chemical Evolution of Galactic Discs.

1977 ◽  
Vol 45 ◽  
pp. 61-66 ◽  
Author(s):  
C. Chiosi
Keyword(s):  
Chemical Evolution ◽  
Mass Density ◽  
Disk Galaxies ◽  
Surface Mass ◽  
Disk Formation ◽  
System A ◽  
Collapse Models ◽  
Nearby Stars ◽  
Surface Mass Density ◽  
Formation Phase

In this paper we discuss a simple model for the chemical evolution of galactic disks, aiming at understanding the observed metallicity gradients in spiral galaxies. The model in corporates both the recent results of Talbot and Arnett (1975), who proposed a rate of star formation driven by the surface mass density, and those of Lynden-Bell (1975), who investigated the consequences of significant infall of gas into the system. A similar attempt was made by Chiosi (1977) for the solar neighbourhood. The result was that the metallicity distribution of nearby stars can be easily interpreted if the time scale for accretion of gas into the solar pool, or in other words the duration of the disk formation phase, is of the or der of 2-3 109ys. Such a result is qualitatively in agreement with the models of Larson (1972), Ostricker and Thuan (1975), and also is implicit in the collapse models for the formation of disk galaxies, Larson (1976).

scholarly journals Time-resolved photometry of the young dipper RX J1604.3-2130A

2020 ◽  
Vol 633 ◽  
pp. A37 ◽  
Author(s):  
A. Sicilia-Aguilar ◽  
C. F. Manara ◽  
J. de Boer ◽  
M. Benisty ◽  
P. Pinilla ◽  
...  
Keyword(s):  
Accretion Rate ◽  
Time Resolved ◽  
Disk Formation ◽  
Corotation Radius ◽  
Disk Structure ◽  
Outer Disk ◽  
Matter Transport ◽  
Multi Wavelength ◽  
Type Variable ◽  
The Times

Context. RX J1604.3-2130A is a young, dipper-type, variable star in the Upper Scorpius association, suspected to have an inclined inner disk, with respect to its face-on outer disk. Aims. We aim to study the eclipses to constrain the inner disk properties. Methods. We used time-resolved photometry from the Rapid Eye Mount telescope and Kepler 2 data to study the multi-wavelength variability, and archival optical and infrared data to track accretion, rotation, and changes in disk structure. Results. The observations reveal details of the structure and matter transport through the inner disk. The eclipses show 5 d quasi-periodicity, with the phase drifting in time and some periods showing increased/decreased eclipse depth and frequency. Dips are consistent with extinction by slightly processed dust grains in an inclined, irregularly-shaped inner disk locked to the star through two relatively stable accretion structures. The grains are located near the dust sublimation radius (~0.06 au) at the corotation radius, and can explain the shadows observed in the outer disk. The total mass (gas and dust) required to produce the eclipses and shadows is a few % of a Ceres mass. Such an amount of mass is accreted/replenished by accretion in days to weeks, which explains the variability from period to period. Spitzer and WISE infrared variability reveal variations in the dust content in the innermost disk on a timescale of a few years, which is consistent with small imbalances (compared to the stellar accretion rate) in the matter transport from the outer to the inner disk. A decrease in the accretion rate is observed at the times of less eclipsing variability and low mid-IR fluxes, confirming this picture. The v sin i = 16 km s−1 confirms that the star cannot be aligned with the outer disk, but is likely close to equator-on and to be aligned with the inner disk. This anomalous orientation is a challenge for standard theories of protoplanetary disk formation.

scholarly journals Barred Galaxies: Intrinsic or Extrinsic?

1996 ◽  
Vol 171 ◽  
pp. 426-426
Author(s):  
M. Noguchi
Keyword(s):  
Star Formation ◽  
Galactic Disk ◽  
Stellar Disk ◽  
Disk Galaxies ◽  
Analytic Model ◽  
Disk Formation ◽  
Barred Galaxies ◽  
Disk Growth ◽  
Bar Formation ◽  
Disk Component

A unified picture is presented of the formation of bar structures in disk galaxies of various morphological types. In order to discuss bar formation in the context of galactic disk formation, a simple analytic model is constructed of the growth of galactic disks by infall of primordial gas from haloes and subsequent star formation in the disks. It is monitored during the course of disk growth whether or not the condition for spontaneous bar formation (i.e., bar instability) is fulfilled for the stellar disk component.

scholarly journals Gaia-DR2 extended kinematical maps

2020 ◽  
Vol 642 ◽  
pp. A95 ◽  
Author(s):  
Ž. Chrobáková ◽  
M. López-Corredoira ◽  
F. Sylos Labini ◽  
H.-F. Wang ◽  
R. Nagy
Keyword(s):  
Dark Matter ◽  
Radial Velocity ◽  
Rotation Curve ◽  
Milky Way ◽  
Galactic Plane ◽  
Dark Matter Halo ◽  
Disk Galaxies ◽  
Modified Newtonian Dynamics ◽  
Outer Disk ◽  
Gaia Dr2

Context. Recent statistical deconvolution methods have produced extended kinematical maps in a range of heliocentric distances that are a factor of two to three larger than those analysed in Gaia Collaboration (2018, A&A, 616, A11) based on the same data. Aims. In this paper, we use such maps to derive the rotation curve both in the Galactic plane and in off-plane regions and to analyse the density distribution. Methods. By assuming stationary equilibrium and axisymmetry, we used the Jeans equation to derive the rotation curve. Then we fit it with density models that include both dark matter and predictions of the MOND (Modified Newtonian dynamics) theory. Since the Milky Way exhibits deviations from axisymmetry and equilibrium, we also considered corrections to the Jeans equation. To compute such corrections, we ran N-body experiments of mock disk galaxies where the departure from equilibrium becomes larger as a function of the distance from the centre. Results. The rotation curve in the outer disk of the Milky Way that is constructed with the Jeans equation exhibits very low dependence on R and z and it is well-fitted both by dark matter halo and MOND models. The application of the Jeans equation for deriving the rotation curve, in the case of the systems that deviate from equilibrium and axisymmetry, introduces systematic errors that grow as a function of the amplitude of the average radial velocity. In the case of the Milky Way, we can observe that the amplitude of the radial velocity reaches ∼10% that of the azimuthal one at R ≈ 20 kpc. Based on this condition, using the rotation curve obtained from the Jeans equation to calculate the mass may overestimate its measurement.

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