scholarly journals How well is angular momentum accretion modelled in semi-analytic galaxy formation models?

2021 ◽  
Author(s):  
Jun Hou ◽  
Cedric G Lacey ◽  
Carlos S Frenk
Keyword(s):  
Angular Momentum ◽  
Galaxy Formation ◽  
Moving Mesh ◽  
Important Process ◽  
Metal Enrichment ◽  
Accretion Process ◽  
Hydrodynamical Simulation ◽  
Gas Cooling ◽  
The Mean ◽  
Cooling Model

Abstract Gas cooling and accretion in haloes delivers mass and angular momentum on to galaxies. In this work, we investigate the accuracy of the modelling of this important process in several different semi-analytic (SA) galaxy formation models (galform , l-galaxies and morgana ) through comparisons with a hydrodynamical simulation performed with the moving-mesh code arepo . Both SA models and the simulation were run without any feedback or metal enrichment, in order to focus on the cooling and accretion process. All of the SA models considered here assume that gas cools from a spherical halo. We found that the assumption that the gas conserves its angular momentum when moving from the virial radius, rvir, to the central region of the halo, r ∼ 0.1rvir, is approximately consistent with the results from our simulation. We also found that, compared to the simulation, the morgana model tends to overestimate the mean specific angular momentum of cooled-down gas, the l-galaxies model also tends to overestimate this in low-redshift massive haloes, while the two older galform models tend to underestimate the angular momentum. In general, the predictions of the new galform cooling model developed by Hou et al. agree agree the best with the simulation.

scholarly journals Rotation of Galaxy Dark Matter Halos

2006 ◽  
Vol 2 (S235) ◽  
pp. 104-104
Author(s):  
Stéphane Herbert-Fort ◽  
Dennis Zaritsky ◽  
Yeun Jin Kim ◽  
Jeremy Bailin ◽  
James E. Taylor
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Numerical Simulations ◽  
Galaxy Formation ◽  
Spiral Galaxy ◽  
Observational Studies ◽  
Spiral Galaxies ◽  
Satellite System ◽  
Dark Matter Halos ◽  
The Mean

AbstractThe degree to which outer dark matter halos of spiral galaxies rotate with the disk is sensitive to their accretion history and may be probed with associated satellite galaxies. We use the Steward Observatory Bok telescope to measure the sense of rotation of nearby isolated spirals and combine these data with those of their associated satellites (drawn from SDSS) to directly test predictions from numerical simulations. We aim to constrain models of galaxy formation by measuring the projected component of the halo angular momentum that is aligned with that of spiral galaxy disks, Jz. We find the mean bulk rotation of the ensemble satellite system to be co-rotating with the disk with a velocity of 22 ± 13 km/s, in general agreement with previous observational studies and suggesting that galaxy disks could be formed by halo baryons collapsing by a factor of ≈10. We also find a prograde satellite fraction of 51% and Jz, of the satellite system to be positively correlated with the disk, albeit at low significance (2655 ± 2232 kpc km/s).

scholarly journals A new gas cooling model for semi-analytic galaxy formation models

2017 ◽  
Vol 475 (1) ◽  
pp. 543-569 ◽  
Author(s):  
Jun Hou ◽  
Cedric G Lacey ◽  
Carlos S Frenk
Keyword(s):  
Galaxy Formation ◽  
Gas Cooling ◽  
Cooling Model

scholarly journals Core rotation braking on the red giant branch for various mass ranges

2018 ◽  
Vol 616 ◽  
pp. A24 ◽  
Author(s):  
C Gehan ◽  
B. Mosser ◽  
E. Michel ◽  
R. Samadi ◽  
T. Kallinger
Keyword(s):  
Angular Momentum ◽  
Red Giants ◽  
Regular Pattern ◽  
Convective Envelope ◽  
Large Sample ◽  
The Mean ◽  
Mixed Modes ◽  
Red Giant ◽  
Core Rotation ◽  
Dipole Gravity

Context. Asteroseismology allows us to probe stellar interiors. In the case of red giant stars, conditions in the stellar interior are such as to allow for the existence of mixed modes, consisting in a coupling between gravity waves in the radiative interior and pressure waves in the convective envelope. Mixed modes can thus be used to probe the physical conditions in red giant cores. However, we still need to identify the physical mechanisms that transport angular momentum inside red giants, leading to the slow-down observed for red giant core rotation. Thus large-scale measurements of red giant core rotation are of prime importance to obtain tighter constraints on the efficiency of the internal angular momentum transport, and to study how this efficiency changes with stellar parameters. Aims. This work aims at identifying the components of the rotational multiplets for dipole mixed modes in a large number of red giant oscillation spectra observed by Kepler. Such identification provides us with a direct measurement of the red giant mean core rotation. Methods. We compute stretched spectra that mimic the regular pattern of pure dipole gravity modes. Mixed modes with the same azimuthal order are expected to be almost equally spaced in stretched period, with a spacing equal to the pure dipole gravity mode period spacing. The departure from this regular pattern allows us to disentangle the various rotational components and therefore to determine the mean core rotation rates of red giants. Results. We automatically identify the rotational multiplet components of 1183 stars on the red giant branch with a success rate of 69% with respect to our initial sample. As no information on the internal rotation can be deduced for stars seen pole-on, we obtain mean core rotation measurements for 875 red giant branch stars. This large sample includes stars with a mass as large as 2.5 M⊙, allowing us to test the dependence of the core slow-down rate on the stellar mass. Conclusions. Disentangling rotational splittings from mixed modes is now possible in an automated way for stars on the red giant branch, even for the most complicated cases, where the rotational splittings exceed half the mixed-mode spacing. This work on a large sample allows us to refine previous measurements of the evolution of the mean core rotation on the red giant branch. Rather than a slight slow-down, our results suggest rotation is constant along the red giant branch, with values independent of the mass.

scholarly journals The effect of metal enrichment and galactic winds on galaxy formation in cosmological zoom simulations

2013 ◽  
Vol 436 (4) ◽  
pp. 2929-2949 ◽  
Author(s):  
Michaela Hirschmann ◽  
Thorsten Naab ◽  
Romeel Davé ◽  
Benjamin D. Oppenheimer ◽  
Jeremiah P. Ostriker ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Metal Enrichment ◽  
Galactic Winds

scholarly journals Large-Scale Structure of the Universe in Unstable Dark Matter Models

1988 ◽  
Vol 130 ◽  
pp. 293-300
Author(s):  
A.G. Doroshkevich ◽  
A.A. Klypin ◽  
M.U. Khlopov
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Numerical Models ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Microwave Background ◽  
Physical Background ◽  
The Mean ◽  
The Universe

Processes of the formation and the evolution of the large-scale structure are discussed in the framework of unstable dark matter models. Six numerical models are presented. The projected distribution of simulated galaxies on the sky, wedge diagrams, correlation functions and the mean linear scale of voids are presented. Physical background of the hypothesis of unstable particles and possible observational tests are discussed. The level of the microwave background fluctuations is estimated analytically. Special attention is given to late stage of supercluster evolution and galaxy formation.

scholarly journals Angular Momentum Transfer Due to Galactic Winds and Cooling Flows

1999 ◽  
Vol 186 ◽  
pp. 201-201
Author(s):  
V. Missoulis
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Momentum Transfer ◽  
Galaxy Formation ◽  
Cooling Flows ◽  
Galactic Wind ◽  
Angular Momentum Transfer ◽  
Early Stages ◽  
Galactic Winds ◽  
Gaseous Envelope

We examine a model of galaxy formation where the bulge is formed at very early stages and this burst of star formation leads to a galactic wind which interacts with a huge surrounding gaseous envelope.

scholarly journals Division I Working Group on “Precession and the Ecliptic”

2005 ◽  
Vol 1 (T26A) ◽  
pp. 67-67
Author(s):  
James L. Hilton ◽  
N. Capitaine ◽  
J. Chapront ◽  
J.M. Ferrandiz ◽  
A. Fienga ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Division I ◽  
General Assembly ◽  
Angular Momentum Vector ◽  
Inertial Reference Frame ◽  
Matrix Representations ◽  
Momentum Vector ◽  
Polynomial Coefficients ◽  
The Earth ◽  
The Mean

AbstractThe WG has conferred via email on the topics of providing a precession theory dynamically consistent with the IAU 2000A nutation theory and updating the expressions defining the ecliptic. The consensus of the WG is to recommend:(a) The terms lunisolar precession and planetary precession be replaced by precession of the equator and precession of the ecliptic, respectively.(b) The IAU adopt the P03 precession theory, of Capitaine et al (2003a, A& A 412, 567–586) for the precession of the equator (Eqs. 37) and the precession of the ecliptic (Eqs. 38); the same paper provides the polynomial developments for the P03 primary angles and a number of derived quantities for use in both the equinox based and celestial intermediate origin based paradigms.(c) The choice of precession parameters be left to the user.(d) The recommended polynomial coefficients for a number of precession angles are given in Table 1 of the WG report, including the P03 expressions set out in Tables 3–;5 of Capitaine et al (2005, A& A 432, 355–;367), and those of the alternative Fukushima (2003, AJ 126, 494–;534) parameterization; the corresponding matrix representations are given in equations 1, 6, 11, and 22 of the WG report.(e) The ecliptic pole should be explicitly defined by the mean orbital angular momentum vector of the Earth-Moon barycenter in an inertial reference frame, and this definition should be explicitly stated to avoid confusion with older definitions. The formal WG report will be submitted, shortly to Celest. Mech. for publication and their recommendations will be submitted at the next General Assembly for adoption by the IAU.

scholarly journals Dark-ages reionization and galaxy formation simulation – XVII. Sizes, angular momenta, and morphologies of high-redshift galaxies

2019 ◽  
Vol 488 (2) ◽  
pp. 1941-1959 ◽  
Author(s):  
Madeline A Marshall ◽  
Simon J Mutch ◽  
Yuxiang Qin ◽  
Gregory B Poole ◽  
J Stuart B Wyithe
Keyword(s):  
Angular Momentum ◽  
Galaxy Evolution ◽  
Galaxy Formation ◽  
High Redshift ◽  
Stellar Mass ◽  
Galaxy Mergers ◽  
High Redshift Galaxies ◽  
Massive Galaxies ◽  
Angular Momenta ◽  
Redshift Galaxies

Abstract We study the sizes, angular momenta, and morphologies of high-redshift galaxies, using an update of the meraxes semi-analytic galaxy evolution model. Our model successfully reproduces a range of observations from redshifts z = 0–10. We find that the effective radius of a galaxy disc scales with ultraviolet (UV) luminosity as $R_\mathrm{ e}\propto L_{\textrm{UV}}^{0.33}$ at z = 5–10, and with stellar mass as $R_e\propto M_\ast ^{0.24}$ at z = 5 but with a slope that increases at higher redshifts. Our model predicts that the median galaxy size scales with redshift as Re ∝ (1 + z)−m, where m = 1.98 ± 0.07 for galaxies with (0.3–1)$L^\ast _{z=3}$ and m = 2.15 ± 0.05 for galaxies with (0.12–0.3)$L^\ast _{z=3}$. We find that the ratio between stellar and halo specific angular momentum is typically less than 1 and decreases with halo and stellar mass. This relation shows no redshift dependence, while the relation between specific angular momentum and stellar mass decreases by ∼0.5 dex from z = 7 to z = 2. Our model reproduces the distribution of local galaxy morphologies, with bulges formed predominantly through galaxy mergers for low-mass galaxies, disc-instabilities for galaxies with M* ≃ 1010–$10^{11.5}\, \mathrm{M}_\odot$, and major mergers for the most massive galaxies. At high redshifts, we find galaxy morphologies that are predominantly bulge-dominated.

A Survey of the Stress between the Ocean and Atmosphere

1951 ◽  
Vol 4 (3) ◽  
pp. 315 ◽  
Author(s):  
CHB Priestley
Keyword(s):  
Angular Momentum ◽  
Atmospheric Angular Momentum ◽  
Latitude Zone ◽  
First Approximation ◽  
Four Seasons ◽  
The Mean ◽  
East West

A survey is made of the mean east-west component of stress between the ocean and atmosphere for each season and each ocean, and for the mean of all oceans. The averaging is carried out for each 5" latitude zone from 55 �N. to 55 �S. The results provide a first approximation to the total torque about the Earth's axis, on the atmosphere as a whole, in the various latitude belts. From them is derived a table showing the distribution of total northward flux of atmospheric angular momentum for the annual mean and the four seasons individually, allowing for the changes occurring during spring and autumn. A brief comparative discussion of both the stress and flux results is given.

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