Astrophysics (Index)About

redshift

(z, redshift parameter)
(change to longer wavelengths due to Doppler effects)

Redshift is a lengthening of EMR wavelengths (e.g., seen in observed spectral lines), due to Doppler effects of radial motion of the EMR-source away from the observer (i.e., its recessional velocity). Given the expansion of the universe such that the more distant an object, the higher its recessional velocity, redshift is used as a measure of distance and lookback time, and a redshift due to this is called a cosmological redshift. Redshifts and blue shifts (the analogous shortening of the wavelength from sources moving toward the observer) are also measured to determine radial velocity of the source, such as in studies of peculiar velocity and of objects orbiting stars such as extra-solar planets and binary companions. Measurements of stars using high resolution spectrography (HRS) can determine radial velocity differences as small as 1 meter per second. The redshift parameter (often just called redshift) z is:

     observed wavelength - rest wavelength
z =  —————————————————————————————————————
              rest wavelength

The relationship between z and the recessional velocity, ignoring relativity (which is OK for low velocity) is z=v/c, where v is recessional velocity and c is the light speed. Incorporating special relativity using the Lorentz transformation (needed for relativistic speeds) is:

1 + z = γ ( 1 + v/c )

where γ is the Lorentz factor, (1-v²/c²). This is equivalent to:

              1 + v/c
1 + z = sqrt( ——————— )
              1 - v/c

Transverse motion has a small effect on redshift an z, as does gravity (gravitational redshift). Redshift determined through noting the different wavelength of absorption lines is termed absorption redshift (zabs) and from emission lines is termed emission redshift (zem).


(measure,EMR,Doppler)
Further reading:
https://en.wikipedia.org/wiki/Red_shift
https://astronomy.swin.edu.au/cosmos/c/redshift
http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/redshf.html
http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/reldop2.html
https://www.esa.int/Science_Exploration/Space_Science/What_is_red_shift
https://www.astro.ucla.edu/~wright/doppler.htm

Referenced by pages:
21-cm experiment
21-cm line
2dF Galaxy Redshift Survey (2dFGRS)
3C 273
3C 279
3C 295
3C 48
6dF Galaxy Survey (6dFGS)
AEGIS
AIM-CO
Akaike information criterion (AIC)
Alcock-Paczyński effect (AP effect)
ALFALFA
Astrid simulation
AzTEC-3
Balmer series (H)
Balmer-break galaxy (BBG)
band shifting
baryon acoustic oscillations (BAO)
Baryon Oscillation Spectroscopic Survey (BOSS)
BINGO
black hole shadow
blind survey
blue shift
Brackett series
brightest cluster galaxy (BCG)
Butcher-Oemler effect (BOE)
Calán/Tololo Supernova Survey
Canada-France Redshift Survey (CFRS)
Canadian Hydrogen Intensity Mapping Experiment (CHIME)
carbon monoxide (CO)
Carnegie Supernova Project (CSP)
Cepheid variable (CEP)
CfA Redshift Survey
CIBER
cluster radius
CMB dipole
CO ladder
CONCERTO
COPSS
cosmic background radiation (CBR)
Cosmic Dawn Intensity Mapper (CDIM)
cosmic distance ladder
Cosmic Evolution Survey (COSMOS)
cosmic infrared background (CIB)
cosmic microwave background (CMB)
cosmic neutrino background (CNB)
cosmological distance
cosmological redshift
cosmological time dilation
cosmological zoom simulation
critical density (ρc)
damped Lyman alpha absorber (DLA)
dark age
dark energy (Λ)
Dark Energy Spectroscopic Instrument (DESI)
Dark Energy Survey (DES)
data cube
DECaLS
deceleration parameter (q)
deep field (DF)
Deep Multicolor Survey (DMS)
deep survey
DEEP2
DESHIMA
DEVILS
direct collapse black hole (DCBH)
distance modulus (μ)
Doppler shift
dropout
dusty galaxy
EDGES
emission line
emission line galaxy (ELG)
epoch of galaxy formation
epoch of reionization (EOR)
escape fraction
ESO Nearby Abell Cluster Survey (ENACS)
Euclid
EXCLAIM
Extended Groth Strip (EGS)
extremely metal poor galaxy (XMPG)
extremely red object (ERO)
Faber-Jackson relation (FJR)
faint blue galaxy (FBG)
Faint Infrared Grism Survey (FIGS)
first galaxies
FourStar Galaxy Evolution Survey (ZFOURGE)
FRB121102
Fred Young Submillimeter Telescope (FYST)
galaxy cluster (CL)
galaxy merger
galaxy power spectrum
Galaxy Zoo
Gamow Explorer
gas fraction estimation
Gemini Observatory
Giant Gemini GMOS survey (GGG survey)
Giant GRB Ring
Giant Metrewave Radio Telescope (GMRT)
GISMO
GLARE
GN-z11
gravitational redshift
GRB 060505
GRB 190114C
Great Attractor
Great Debate
Great Wall
Green Bank Telescope (GBT)
Gunn-Peterson trough
Hα survey
H-alpha (Ha)
H-beta (Hβ)
Hamburg/ESO Survey (HE)
HD1
HERA
Hercules-Corona Borealis Great Wall (Her-CrB GW)
Herschel Stripe 82 Survey (HerS)
HFLS3
HIRAX
Hoag's Object
Holmberg radius (RH)
hot DOG
Hubble constant (H0)
Hubble diagram
Hubble expansion
Hubble time (tH)
Hubble Ultra-Deep Field (HUDF)
Humphreys series
infrared (IR)
intensity mapping (IM)
ionized carbon fine structure line ([CII])
ionizing radiation
IRAC Shallow Survey (ISS)
isotropy
James Webb Space Telescope (JWST)
K correction
KMOS3D
Lambda-CDM model (ΛCDM)
Large Millimeter Telescope (LMT)
large quasar group (LQG)
Las Campanas Redshift Survey (LCRS)
LIGO
line broadening
Low-frequency Array (LOFAR)
luminosity distance (dL)
luminosity function (LF)
luminous red galaxy (LRG)
Lyman alpha (Ly-α)
Lyman beta (Ly-β)
Lyman continuum (LyC)
Lyman series (L)
Lyman-alpha blob
Lyman-alpha emitter (LAE)
Lyman-alpha forest
Lyman-break galaxy (LBG)
MeerKLASS
microwave
Molecular Deep Field
MORA
Multi-Epoch Nearby Cluster Survey (MENeaCS)
Murchison Widefield Array (MWA)
near infrared (NIR)
observable universe
Ogle Galaxy Catalog (OGC)
OIR
Origins Space Telescope (OST)
OVRO-LWA
P Cygni profile
Palomar high-redshift quasar surveys
Pantheon
PAPER
Paschen series
pea galaxy (GP)
peak star-formation epoch
Pfund series
PHIBSS
photometric redshift (photo-z)
PIXIE
PRIMUS
proto-cluster
protogalaxy
proximity effect
quasar (QSO)
r-process
radio galaxy (RG)
rare designator prefixes
REBELS
recombination
redshift space
redshift survey
redshift-angular size relation
redshift-magnitude relation
REFINE
rest wavelength
Rossiter-McLaughlin effect (RM effect)
Sachs-Wolfe effect (SWE)
SARAS
SHARDS
sigma-8 tension (S8 tension)
SINS
Sloan Digital Sky Survey (SDSS)
SMBH formation
Southern Sky Redshift Survey (SSRS)
spectral feature
spectral line
Spitzer HETDEX Exploratory Large Area Survey (SHELA)
standard candle
standard ruler
star formation history (SFH)
star formation rate (SFR)
star-formation rate stellar-mass ratio
Stephan's Quintet
submillimeter galaxy (SMG)
supermassive black hole (SMBH)
Supernova Cosmology Project (SCP)
Supernova Legacy Survey (SNLS)
survey depth
Swope Supernova Survey (SSS)
systemic velocity
templates
Tianlai Project
time dilation
Tomographic Ionized-carbon Mapping Experiment (TIME)
TXS 0506+056
ultra-fast outflow (UFO)
ultraluminous infrared galaxy (ULIRG)
USS Sources
UVJ diagram
velocity-metallicity relation
VIMOS Public Extragalactic Redshift Survey (VIPERS)
VIMOS-VLT Deep Survey (VVDS)
WiggleZ
WINGS
X-ray luminosity function (XLF)
X-ray luminous galaxy cluster
X-SHOOTER Lyman α survey at z = 2 (XLS-z2)
Yuan-Tseh Lee Array (YTLA)

Index