scholarly journals Effects of self-consistent rest-ultraviolet colours in semi-empirical galaxy formation models

2020 ◽  
Vol 498 (2) ◽  
pp. 2645-2661 ◽  
Author(s):  
Jordan Mirocha ◽  
Charlotte Mason ◽  
Daniel P Stark
Keyword(s):  
Galaxy Formation ◽  
Surface Density ◽  
Empirical Relationships ◽  
James Webb Space Telescope ◽  
Luminosity Functions ◽  
Self Consistent ◽  
The Mean ◽  
Semi Empirical ◽  
Ir Emission ◽  
Dust Surface

ABSTRACT Connecting the observed rest-ultraviolet (UV) luminosities of high-z galaxies to their intrinsic luminosities (and thus star formation rates, SFRs) requires correcting for the presence of dust. We bypass a common dust-correction approach that uses empirical relationships between infrared (IR) emission and UV colours, and instead augment a semi-empirical model for galaxy formation with a simple – but self-consistent – dust model and use it to jointly fit high-z rest-UV luminosity functions (LFs) and colour–magnitude relations (MUV–β). In doing so, we find that UV colours evolve with redshift (at fixed UV magnitude), as suggested by observations, even in cases without underlying evolution in dust production, destruction, absorption, or geometry. The observed evolution in our model arises due to the reduction in the mean stellar age and rise in specific SFRs with increasing z. The UV extinction, AUV, evolves similarly with redshift, though we find a systematically shallower relation between AUV and MUV than that predicted by IRX–β relationships derived from z ∼ 3 galaxy samples. Finally, assuming that high $1600\hbox{-}{\mathring{\rm A}}$ transmission (≳0.6) is a reliable Ly α emitter (LAE) indicator, modest scatter in the effective dust surface density of galaxies can explain the evolution both in MUV–β and LAE fractions. These predictions are readily testable by deep surveys with the James Webb Space Telescope.

scholarly journals The Millennium Galaxy Catalogue: the severe attenuation of bulge flux by dusty spiral discs

2007 ◽  
Vol 3 (S245) ◽  
pp. 403-406
Author(s):  
Simon P. Driver ◽  
Keyword(s):  
Close Agreement ◽  
Luminosity Functions ◽  
Central Regions ◽  
The Mean ◽  
Galaxy Population ◽  
Ir Emission ◽  
Optical Appearance

AbstractUsing the Millennium Galaxy Catalogue we quantify the dependency of the disc and bulge luminosity functions on galaxy inclination. Using a contemporary dust model we show that our results are consistent with galaxy discs being optically thick in their central regions ($\tau_B^f=3.8\pm0.7$). As a consequence the measured B-band fluxes of bulges can be severely attenuated by 50% to 95% depending on disc inclination. We argue that a galaxy's optical appearance can be radically transformed by simply removing the dust, e.g. during cluster infall, with mid-type galaxies becoming earlier, redder, and more luminous. Finally we derive the mean photon escape fraction from the integrated galaxy population over the 0.1 μm to 2.1 μm range, and use this to show that the energy of starlight absorbed by dust (in our model) is in close agreement with the total far-IR emission.

scholarly journals The Universe at z > 10: predictions for JWST from the universemachine DR1

2020 ◽  
Vol 499 (4) ◽  
pp. 5702-5718
Author(s):  
Peter Behroozi ◽  
Charlie Conroy ◽  
Risa H Wechsler ◽  
Andrew Hearin ◽  
Christina C Williams ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Formation Rate ◽  
Mass Function ◽  
Model Parameters ◽  
James Webb Space Telescope ◽  
Luminosity Functions ◽  
Galaxy Halo ◽  
Stellar Masses ◽  
The Universe

ABSTRACT The James Webb Space Telescope (JWST) is expected to observe galaxies at z > 10 that are presently inaccessible. Here, we use a self-consistent empirical model, the universemachine, to generate mock galaxy catalogues and light-cones over the redshift range z = 0−15. These data include realistic galaxy properties (stellar masses, star formation rates, and UV luminosities), galaxy–halo relationships, and galaxy–galaxy clustering. Mock observables are also provided for different model parameters spanning observational uncertainties at z < 10. We predict that Cycle 1 JWST surveys will very likely detect galaxies with M* > 107 M⊙ and/or M1500 < −17 out to at least z ∼ 13.5. Number density uncertainties at z > 12 expand dramatically, so efforts to detect z > 12 galaxies will provide the most valuable constraints on galaxy formation models. The faint-end slopes of the stellar mass/luminosity functions at a given mass/luminosity threshold steepen as redshift increases. This is because observable galaxies are hosted by haloes in the exponentially falling regime of the halo mass function at high redshifts. Hence, these faint-end slopes are robustly predicted to become shallower below current observable limits (M* < 107 M⊙ or M1500 > −17). For reionization models, extrapolating luminosity functions with a constant faint-end slope from M1500 = −17 down to M1500 = −12 gives the most reasonable upper limit for the total UV luminosity and cosmic star formation rate up to z ∼ 12. We compare to three other empirical models and one semi-analytic model, showing that the range of predicted observables from our approach encompasses predictions from other techniques. Public catalogues and light-cones for common fields are available online.

scholarly journals Realistic mock observations of the sizes and stellar mass surface densities of massive galaxies in FIRE-2 zoom-in simulations

2020 ◽  
Vol 501 (2) ◽  
pp. 1591-1602
Author(s):  
T Parsotan ◽  
R K Cochrane ◽  
C C Hayward ◽  
D Anglés-Alcázar ◽  
R Feldmann ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Surface Density ◽  
Stellar Mass ◽  
Massive Galaxies ◽  
Star Forming ◽  
Stellar Feedback ◽  
Central Surface ◽  
Stellar Ages ◽  
The Galaxy ◽  
Zoom In

ABSTRACT The galaxy size–stellar mass and central surface density–stellar mass relationships are fundamental observational constraints on galaxy formation models. However, inferring the physical size of a galaxy from observed stellar emission is non-trivial due to various observational effects, such as the mass-to-light ratio variations that can be caused by non-uniform stellar ages, metallicities, and dust attenuation. Consequently, forward-modelling light-based sizes from simulations is desirable. In this work, we use the skirt  dust radiative transfer code to generate synthetic observations of massive galaxies ($M_{*}\sim 10^{11}\, \rm {M_{\odot }}$ at z = 2, hosted by haloes of mass $M_{\rm {halo}}\sim 10^{12.5}\, \rm {M_{\odot }}$) from high-resolution cosmological zoom-in simulations that form part of the Feedback In Realistic Environments project. The simulations used in this paper include explicit stellar feedback but no active galactic nucleus (AGN) feedback. From each mock observation, we infer the effective radius (Re), as well as the stellar mass surface density within this radius and within $1\, \rm {kpc}$ (Σe and Σ1, respectively). We first investigate how well the intrinsic half-mass radius and stellar mass surface density can be inferred from observables. The majority of predicted sizes and surface densities are within a factor of 2 of the intrinsic values. We then compare our predictions to the observed size–mass relationship and the Σ1−M⋆ and Σe−M⋆ relationships. At z ≳ 2, the simulated massive galaxies are in general agreement with observational scaling relations. At z ≲ 2, they evolve to become too compact but still star forming, in the stellar mass and redshift regime where many of them should be quenched. Our results suggest that some additional source of feedback, such as AGN-driven outflows, is necessary in order to decrease the central densities of the simulated massive galaxies to bring them into agreement with observations at z ≲ 2.

scholarly journals Simulating Solar Global Magnetism in 3-D

2012 ◽  
Vol 10 (H16) ◽  
pp. 101-103
Author(s):  
A. S. Brun ◽  
A. Strugarek
Keyword(s):  
Magnetic Field ◽  
Recent Progress ◽  
Convection Zone ◽  
Thermal Structure ◽  
Solar Convection ◽  
Self Consistent ◽  
The Mean ◽  
The Magnetic Field

AbstractWe briefly present recent progress using the ASH code to model in 3-D the solar convection, dynamo and its coupling to the deep radiative interior. We show how the presence of a self-consistent tachocline influences greatly the organization of the magnetic field and modifies the thermal structure of the convection zone leading to realistic profiles of the mean flows as deduced by helioseismology.

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 Cosmological evolution of the AGN kinetic luminosity function

2006 ◽  
Vol 2 (S238) ◽  
pp. 65-70
Author(s):  
Andrea Merloni ◽  
Sebastian Heinz
Keyword(s):  
Galaxy Formation ◽  
Luminosity Function ◽  
Cosmological Evolution ◽  
Energy Output ◽  
Theoretical Assumption ◽  
X Ray ◽  
Spectrum Radio ◽  
Luminosity Functions ◽  
Jet Power ◽  
Joint Evolution

AbstractWe present a first attempt to derive the cosmological evolution of the kinetic luminosity function of AGN based on the joint evolution of the flat spectrum radio and hard X-ray selected AGN luminosity functions. An empirical correlation between jet power and radio core luminosity is found, which is consistent with the theoretical assumption that, below a certain Eddington ratio, SMBH accrete in a radiatively inefficient way, while most of the energy output is in the form of kinetic energy.We show how the redshift evolution of the kinetic power density from such a low-ṁ mode of accretion makes it a good candidate to explain the so-called “radio mode” of AGN feedback as outlined in many galaxy formation schemes.

scholarly journals MILES FORMULAE FOR BOOLEAN MODELS OBSERVED ON LATTICES

2011 ◽  
Vol 28 (2) ◽  
pp. 77 ◽  
Author(s):  
Joachim Ohser ◽  
Werner Nagel ◽  
Katja Schladitz
Keyword(s):  
Mean Curvature ◽  
Surface Density ◽  
Euler Number ◽  
Volume Density ◽  
Random Sets ◽  
Boolean Models ◽  
Intrinsic Volumes ◽  
Binary Images ◽  
Density Surface ◽  
The Mean

The densities of the intrinsic volumes – in 3D the volume density, surface density, the density of the integral of the mean curvature and the density of the Euler number – are a very useful collection of geometric characteristics of random sets. Combining integral and digital geometry we develop a method for efficient and simultaneous calculation of the intrinsic volumes of random sets observed in binary images in arbitrary dimensions. We consider isotropic and reflection invariant Boolean models sampled on homogeneous lattices and compute the expectations of the estimators of the intrinsic volumes. It turns out that the estimator for the surface density is proved to be asymptotically unbiased and thusmultigrid convergent for Boolean models with convex grains. The asymptotic bias of the estimators for the densities of the integral of the mean curvature and of the Euler number is assessed for Boolean models of balls of random diameters. Miles formulae with corresponding correction terms are derived for the 3D case.

An explicit algebraic Reynolds-stress and scalar-flux model for stably stratified flows

2013 ◽  
Vol 723 ◽  
pp. 91-125 ◽  
Author(s):  
W. M. J. Lazeroms ◽  
G. Brethouwer ◽  
S. Wallin ◽  
A. V. Johansson
Keyword(s):  
Heat Flux ◽  
Kinetic Energy ◽  
Temperature Gradient ◽  
Reynolds Stress ◽  
Turbulent Heat Flux ◽  
Turbulent Heat ◽  
Homogeneous Shear ◽  
Self Consistent ◽  
The Mean ◽  
Homogeneous Shear Flow

AbstractThis work describes the derivation of an algebraic model for the Reynolds stresses and turbulent heat flux in stably stratified turbulent flows, which are mutually coupled for this type of flow. For general two-dimensional mean flows, we present a correct way of expressing the Reynolds-stress anisotropy and the (normalized) turbulent heat flux as tensorial combinations of the mean strain rate, the mean rotation rate, the mean temperature gradient and gravity. A system of linear equations is derived for the coefficients in these expansions, which can easily be solved with computer algebra software for a specific choice of the model constants. The general model is simplified in the case of parallel mean shear flows where the temperature gradient is aligned with gravity. For this case, fully explicit and coupled expressions for the Reynolds-stress tensor and heat-flux vector are given. A self-consistent derivation of this model would, however, require finding a root of a polynomial equation of sixth-order, for which no simple analytical expression exists. Therefore, the nonlinear part of the algebraic equations is modelled through an approximation that is close to the consistent formulation. By using the framework of a$K\text{{\ndash}} \omega $model (where$K$is turbulent kinetic energy and$\omega $an inverse time scale) and, where needed, near-wall corrections, the model is applied to homogeneous shear flow and turbulent channel flow, both with stable stratification. For the case of homogeneous shear flow, the model predicts a critical Richardson number of 0.25 above which the turbulent kinetic energy decays to zero. The channel-flow results agree well with DNS data. Furthermore, the model is shown to be robust and approximately self-consistent. It also fulfils the requirements of realizability.

scholarly journals The colorimetric properties of the spectrum

1931 ◽  
Vol 108 (759) ◽  
pp. 576-576 ◽  
Keyword(s):  
Distribution Curve ◽  
National Physical Laboratory ◽  
Group Of Seven ◽  
Physical Laboratory ◽  
Luminosity Functions ◽  
Direct Measurements ◽  
Energy Distribution Curve ◽  
The Mean ◽  
General Method

The paper describes an investigation carried out at the National Physical Laboratory to determine the colorimetric properties of a group of seven subjects as obtained from direct measurements of the trichromatic coefficients of the spectrum on a trichromatic colorimeter. The “spectral distribution curves of the primaries,” by means of which the colorimetric quality of a heterochromatic stimulus may be computed from its energy distribution curve, are obtained by combining the experimentally determined trichromatic coefficients with the International Standard visibility curve. This procedure is a simplification, applicable to the mean results of a normal group, of a general method by which the chromatic and luminosity functions of any subject or group of subjects can be determined from one set of observations. The general method is described in an Appendix.

CURRENTS, SPIN DENSITIES AND MEAN-FIELD FORM FACTORS IN ROTATING NUCLEI: A SEMI-CLASSICAL APPROACH

2004 ◽  
Vol 13 (01) ◽  
pp. 225-233 ◽  
Author(s):  
J. BARTEL ◽  
K. BENCHEIKH ◽  
P. QUENTIN
Keyword(s):  
Mean Field ◽  
Form Factors ◽  
Spin Vector ◽  
Self Consistent ◽  
Field Form ◽  
Local Densities ◽  
The Mean ◽  
Self Consistency ◽  
Spin Densities ◽  
Rotating Nuclei

We present self-consistent semi-classical local densities characterising the structure of rotating nuclei. A particular emphasis is put on those densities which are generated by the breaking of time-reversal symmetry through the cranking piece of the Routhian, namely the current density and the spin vector density. Our approach which is based on the Extended-Thomas-Fermi method goes beyond the Inglis cranking approach and contains naturally the Thouless-Valatin self-consistency terms expressing the response of the mean field to the time-odd part of the density matrix.

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