Glossary

AB magnitude

An astronomical magnitude system in which the apparent magnitude is defined as \(m=-2.5\log_{10}f-48.60\) for a flux density, \(f\), measured in ergs per second per square centimeter per hertz

ADAF

An advection-dominated accretion flow (ADAF) is a particular solution for an accretion flow around a black hole, star or compact object in which energy liberated by viscous forces is stored within the accretion flow and advected inward to the central object (see Narayan et al. 1998)

AHF

Amiga’s Halo Finder (AHF) is a software package which identifies dark matter halos in N-body simulations. Full details are given by Gill et al. (2004) and Knollmann and Knebe (2009)

Approximate Nearest Neighbor

The Approximate Nearest Neighbor library is a software package used finding the closest set of points to a given point, approximately

AxionCAMB

AxionCAMB is a code to compute anisotropies in the cosmic microwave background, and the linear theory power spectra of matter and radiation including an axion component in the dark matter

backward descendant

The primary progenitor of a node. This type of descendant is usually relevant when building merger trees and should be distinguished from a forward descendant which is relevant when considering how halos and galaxies evolve forward in time

Bernoulli distribution

A discrete probability distribution which takes value \(1\) with success probability \(p\) and value \(0\) with failure probability \(q = 1-p\). Read more on Wikipedia

CAMB

CAMB is a code to compute anisotropies in the cosmic microwave background, and the linear theory power spectra of matter and radiation

CDF

Cumulative Distribution Function (CDF) is a function which describes the cumulative probability for a random variable to be equal to or less than a given value.

CDM

Cold dark matter (CDM) is a hypothesized type of dark matter in which the particles move slowly compared to the speed of light

CGM

circum-galactic medium

CIE

collisional ionization equilibrium

CLASS

CLASS is a code to compute anisotropies in the cosmic microwave background, and the linear theory power spectra of matter and radiation

Cloudy

Cloudy is a code to compute the ionization structure of HII regions

CMB

cosmic microwave background

component

An individual physical system within a node, such as a dark matter halo, a galactic disk or a supermassive black hole

dark matter-only universe

Masses of nodes/halos are often defined as the mass which the node/halo would have in a dark matter-only universe in which the total matter density is the same as the actual model universe, but in which no baryons are present (i.e. all matter is dark matter)

deadlock

A deadlock describes a situation in which no node in a merger tree (or forest) can be evolved further forward in time due to the existence of circular dependencies between nodes. Deadlocks can occur due to incompatible parameter choices, or may indicate a bug in Galacticus.

DSL

Domain-specific languages (DSL) are a type of programming language dedicated to a particular problem. In Galacticus a DSL is used to specify the structure of component

ENZO

Enzo is an adaptive mesh refinement hydrodynamics code

FDM

Fuzzy dark matter (FDM) is a hypothesized type of dark matter consisting of extremely light scalar particles with masses on the order of \(10^{-22}\) eV

FFTLog

FFTLog is a code to compute fast Fourier transforms of discrete periodic sequences of logarithmically spaced data

forest

A collection of merger trees that are linked together by virtue of nodes which jump between trees

forward descendant

The node with which the mass (or majority of the mass) of a node will become associated with at a later time. This type of descendant is usually relevant when considering how halos and galaxies evolve forward in time and should be distinguished from a backward descendant which is relevant when building merger trees

GAMA

The Galaxy and Mass Assembly (GAMA) survey is a spectroscopic survey of \(\approx 300,000\) galaxies down to r \(<\) 19.8 mag over \(\approx 286\) deg\(^2\).

GNU

GNU is a free software collection used extensively on Unix-like operating systems

GraphViz

GraphViz is an open source graph visualization package. It is used by Galacticus in making diagrams of merger trees.

GSL

GNU Scientific Library (GSL) is a library providing a variety of numerical algorithms.

HDF5

The hierarchical data format (version 5; HDF5) is a file format designed for storing scientific data.

HOD

A halo occupation distribution (HOD) is a mathematical model describing the distribution of the number of galaxies (of some given physical properties) found in a dark matter halo of given mass.

IGM

intergalactic medium

IMF

initial mass function

IRATE

IRATE is file format designed for N-body simulation particle, halo, merger tree, and galaxy data

ISCO

innermost stable circular orbit

ISM

interstellar medium

Latin hypercube

A Latin hypercube is a construct for generating a sample of plausible collections of parameter values from a multidimensional distribution

Lyman continuum

The part of the electromagnetic spectrum which is capable of ionizing hydrogen, i.e. photons with wavelengths shorter than 91.1267 nanometers and with energy above 13.6 eV

maggie

A unit of luminosity defined to be equal to the luminosity of a zeroth magnitude object in the AB magnitude system

mangle

mangle is a software package used for defining angular masks on the surface of a sphere. It is used primarily for defining the geometry of galaxy surveys

maximin

In Latin hypercube design, the “maximin” approach generates a large number of Latin hypercube and selects the one which has the greatest minimum distance between all pairs of points in the hypercube

MCMC

Markov Chain Monte Carlo

MD5 hash

The MD5 Message-Digest Algorithm is a widely used cryptographic hash function that produces a 128-bit (16-byte) hash value. In Galacticus it is used to encode unique labels for modules which are incorporated into file names. Galacticus uses the glibc crypt() function to compute MD5 hashes, but switches “/” for “@” in the hash (since “/” is inconvenient for use in file names)

mergee

For a given node in a merger tree, the set of mergee nodes consists of all nodes which will undergo a galaxy merger with the node at some point in the future

Millennium Simulation

The Millennium Simulation is a high-resolution N-body simulation of structure formation in a cold dark matter universe.

MPI

Message Passing Interface (MPI) is a standard for passing messages between processes on parallel computers.

NFW

Navarro-Frenk-White (dark matter halo profile)

node

A single point in a merger tree, consisting of a dark matter halo and associated baryons

NSC

Nuclear star clusters (NSC) are high-density star clusters found in the centers of some galaxies

ODE

ordinary differential equation

OpenMP

OpenMP is an API for shared memory parallel programming.

PAH

Polycyclic aromatic hydrocarbons (PAH) are large organic molecules consisting of fused aromatic rings

parent

In a merger tree, the parent node of any given node that exists at time \(t_0\) is that node to which it is directly connected in the tree at time \(t_1>t_0\)

PBS

Portable Batch System (PBS) is a job scheduler used on many compute cluster environments.

PDF

Probability Density Function (PDF) is a function which describes the probability for a random variable to take on a given value.

primary progenitor

The progenitor of a given node which is regarding as the direct descendant of that node (often, but not always, the most massive progenitor). Other progenitors are considered to merge into this primary progenitor

RecFast

RecFast is a code to calculate the recombination history of the universe

SAM

Semi-analytic models (SAMs) are a type of galaxy formation model utilizing simple parameterizations of physical processes to follow the evolution of galaxies through a merging hierarchy of galaxies.

SDSS

Sloan Digital Sky Survey

SED

spectral energy distribution

SNe

supernovae

UUID

A universally unique identifier—this is a label which uniquely identifies some object (in this case, a Galacticus model)

WDM

Warm dark matter (WDM) is a hypothesized type of dark matter in which the particle has non-negligible thermal velocity at decoupling

XML

XML is a markup language, used for Galacticus parameter files