Astrophysics (index)

Galaxy

(gravitationally-bound group of stars)

A Galaxy is a group of millions or billions of stars gravitationally bound, such as the Milky Way. Galaxies often have a Supermassive Black Hole (SMBH) in the center. The movement of stars as compared to the mass revealed by the stars indicates there is hidden mass in galaxies, which has been termed Dark Matter.

Galaxy Classification:

  • elliptical galaxies - come in all sizes, the largest as much as a hundreds of thousands of Parsecs (pc) in length.
  • Spiral Galaxy Disk Galaxy - Milky Way is typical, 50,000 parsecs across.
  • Lenticular
  • Lenticular - bright central Bulge in disk but no visible spiral.
  • Irregular

dwarf galaxies are small galaxies that can be classified as elliptical or irregular, and can be as small as 100 parsecs across.

Star Formation (SF) is most seen in Spiral/Disk galaxies. Elliptical galaxies are considered the results of mergers that have lost their gas, e.g., by going through a Starburst Galaxy stage. Molecular Gas Depletion Time is the time it takes for the gas in a star-forming galaxy to be used. The term Early-Type Galaxy (ETG or Blue Galaxy) designates a galaxy with early-type (hot, blue) stars, indicating recent stellar formation, and Late-Type Galaxy (LTG or Red Galaxy) designates the opposite, with late-type, red stars, whose age-range suggests they are older. This represents a Galaxy Bimodality of galaxies forming stars and not.

The workings of Spiral Arms of a spiral galaxy is not fully certain, with the classic theory consisting of Spiral Density Waves (of higher-density Intergalactic Medium (IGM)) feeding a visible spiral wave of Star Formation. Many of the created stars will be bright but short-lived, so a traveling line of star formation will lead a line of brightness, a spiral arm.

For the purposes of modeling, especially functions within galaxies, they are often modeled as:


(object type)
http://en.wikipedia.org/wiki/Galaxy

Referenced by:
Active Galaxy
AEGIS
Active Galactic Nucleus (AGN)
Alcock-Paczyński Effect
ALFALFA
Alpha CO (αCO)
Arp-Madore Catalog of Southern Peculiar Galaxies (AM)
Adaptive Mesh Refinement (AMR)
Atlas of Peculiar Galaxies (APG)
APM Galaxy Survey (APMUKS)
Arakelian Catalog (Ark)
Astronomical Catalog
Astronomical Quantities
Astronomical Survey
Atlas 3d
Axisymmetric
AzTEC-3
Balmer Series
Baryon Acoustic Oscillations (BAO)
Bar
Balmer-Break Galaxy (BBG)
Brightest Cluster Galaxy (BCG)
BDF
Black Hole (BH)
Baryon Oscillation Spectroscopic Survey (BOSS)
Asiago Supernova Catalog (B/SN)
Bulge
Caldwell Catalog
CALIFA
Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS)
Canis Major Dwarf Galaxy
CARMA EDGE
Cold Dark Matter (CDM)
Celestial Mechanics
Cepheid Variable
Cosmic Gamma Ray Background (CGB)
Circumgalactic Medium (CGM)
Chemodynamics
Cosmic Infrared Background (CIB)
Circinus Galaxy (ESO 97-G13)
Conditional Luminosity Function (CLF)
Cluster Radius
Carbon Monoxide (CO)
Cold Gas
COLD GASS
Color-Color Diagram
Color-Magnitude Diagram (CMD)
Comet Galaxy
Computational Astrophysics
Conservation Law
Cosmic Distance Ladder
Cosmic String
Cosmological Principle
Cosmological Zoom Simulation
Cosmic Evolution Survey (COSMOS)
Council Of Giants
Corotation Resonance (CR)
Conditional Stellar Mass Function (CSMF)
Dark Matter
Dark Matter Halo
DEEP2
Velocity Dispersion (σ)
Drake Equation
Dropout
Dwarf Galaxy
Dynamo
EAGLE
Extended Groth Strip (EGS)
Ejection
Emission Line Galaxy (ELG)
Elliptical Galaxy
EMPIRE Survey
Epoch of Reionization (EOR)
Epoch of Galaxy Formation
Escape Fraction
ESO/Uppsala Survey Of The ESO (B) Atlas
Extinction
Star Formation Feedback
Faint Infrared Grism Survey (FIGS)
FIRE Simulations
First Galaxies
FORNAX
Fast Radio Burst (FRB)
Fairall Galaxy List (Frl)
Gadget-2
Galactic Electron Density
Galactic Halo
Galactic Plane
Galaxy Bias
Galaxy Classification
Galaxy Cluster (CL)
Galaxy Filament
Galaxy Group
Galaxy Main Sequence
Galaxy Merger
Galaxy Power Spectrum
Galaxy SED
Galaxy Zoo
Galaxy Evolution Explorer (GALEX)
GALEX Arecibo SDSS Survey (GASS)
Gas Flow
Gas Fraction
Gas Fraction Estimation
Gas Streamer
GISMO
Globular Cluster (GC)
GOODS NICMOS Survey (GNS)
Grand Design Spiral Galaxy
Gravitational Lensing
Gravity
Great Attractor
Galaxy Zoo 2 (GZ2)
Habitable Zone (HZ)
Halo Abundance Matching (HAM)
Hawaii K-Band Galaxy Survey
Hubble Deep Field (HDF)
Hubble Deep Field South (HDF-S)
Herschel Redshift Survey (HeRS)
HFLS3
Hierarchical Assembly of Galaxies
Hyperluminous Infrared Galaxy (HLIRG)
Hot DOG
H-R Diagram (HRD)
Hubble Constant (H0)
Hubble Ultra-Deep Field (HUDF)
High-Velocity Cloud (HVC)
Hypervelocity Star (HVS)
IC 342
Intergalactic Medium (IGM)
Interplanetary Medium (IPM)
Iron (Fe)
Interstellar Medium (ISM)
Interstellar Magnetic Field (ISMF)
James Clerk Maxwell Telescope (JCMT)
Kinematic Distance
KMOS3D
Lyman-Alpha Emitter (LAE)
Lambda-CDM model (ΛCDM)
LAMOST
Laniakea Supercluster
Lyman-Break Galaxy (LBG)
Line Broadening
Luminous Infrared Galaxy (LIRG)
Large Magellanic Cloud (LMC)
Local Group (LG)
Local Sheet
Luminous Red Galaxy (LRG)
Low-Surface-Brightness Galaxy (LSB Galaxy)
Large Scale Structure (LSS)
Luminosity Function (LF)
Local Volume (LV)
Lyman-Alpha Forest
Messier 100 (M100)
Andromeda (M31)
Triangulum Galaxy (M33)
Whirlpool Galaxy (M51a)
Messier 74 (M74)
M82
M87
MACHO
Mass Transport
Morphological Catalogue Of Galaxies (MCG)
Messier Catalog
Metallicity (Z)
Gravitational Microlensing
Milky Way
Markarian Galaxy (Mkn)
Mock Catalog
N-Body Simulation
NASA/IPAC Extragalactic Database (NED)
NGC 253
NGC 2770
Ammonia (NH3)
1 Jansky Empty Field Survey (1 Jy)
Open Cluster
Peculiar Velocity
Principal Galaxies Catalog (PGC)
PHIBSS
Polar-Ring Catalog (PRC)
Protogalaxy
PSF Fitting
Quenched Galaxy
Ram Pressure
Reddening
Redshift Space
Radio Galaxy (RG)
RASS/Green Bank Catalog (RGB)
Rotation Curve
R-Process
SAGE
Satellite Galaxy
Scale Height (H)
Subaru Deep Field (SDF)
Sloan Digital Sky Survey (SDSS)
Spectral Energy Distribution (SED)
Spitzer Extended Deep Survey (SEDS)
Seyfert Galaxy
Star Formation History (SFH)
Synthetic Field Method (SFM)
Star Formation Rate (SFR)
Spitzer HETDEX Exploratory Large Area Survey (SHELA)
SIMSTACK
SINS
Supermassive Black Hole (SMBH)
Small Magellanic Cloud (SMC)
Submillimeter Galaxy (SMG)
Supernova (SN)
SN 2014J
Spectral Line
Spiral Galaxy
Stellar Population Synthesis (SPS)
Stellar Population Synthesis Code
Standard Candle
STARBURST99
Starburst Galaxy
Star Formation (SF)
Stellar Nucleus
Subaru Telescope
Submillimeter Astronomy
Supercluster
Surface Density (Σ)
Synthetic Spectrum
Tully-Fisher Relation (TFR)
3C 273
3C 295
3D-HST
Three Dimensional Model
Tidal Force
Timescale
TiNy Titans (TNT)
21cm Line
Toomre Q Parameter (Q)
2dF Galaxy Redshift Survey (2dFGRS)
Two Micron All-Sky Survey (2MASS)
Type Ia Supernova
Ultra-Faint Dwarf Galaxy (UFD)
Uppsala General Catalogue (UGC)
Ultraluminous Infrared Galaxy (ULIRG)
Ursa Major II Dwarf
Virgo
Virial Theorem
Voyager
Catalogue of Interacting Galaxies (VV)
Weak Lensing
Westerhout Radio Survey (W)
Wide-Field Multi-Object Spectrograph (WFMOS)
Wolf-Rayet Galaxy

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