This page displays results from searches for redshift data for an
individual object. These redshift data are distinct from NED's "Basic
Data" because they are not only referenced, but accompanied by detailed
qualifiers. Within NED, each measurement (single data point) along with its
descriptors is called a "Redshift Data Frame" or a "Redshift Data Point".
The redshifts displayed in the Basic Data page are often NOT
included in the Redshift Data page, though they are included in the summary
list as No. "0" with their errors and references.
The redshift data returned by your search will be presented as an
HTML table (default), HTML preformatted text, ASCII text (tab-separated
or bar-separated), or in XML (VOTable) format. The HTML output is
formatted for easy reading by eye on your computer screen, while the
ASCII and XML output is appropriate for parsing by computer scripts or
programs. The ASCII and XML tables are preceded by a header line showing
the data contents of each column.
The top section of this page displays a summary table of NED's redshift
data frames for a given object. The first line shows the redshift taken from
NED's basic data. The second and following lines include
- A sequential data-point number applicable to this list only.
- The frequency or wavelength at which the data apply (in common
astronomical jargon, e.g. "Optical", "21-cm").
- The redshift or velocity as published, first in km/s with
errors if given; then in dimensionless units
z = Δλ/λ0,
again with errors if given in the original reference.
- The errors are expressed as 1-sigma uncertainties (if given in the
- The reference code for the source of the redshift. This is linked
to NED's Reference database so that you may retrieve the full
reference or abstract easily.
More extensive data for any measurement in the list may be seen by
clicking on the sequential number for that measurement, or by scrolling
down the page to the measurement of interest.
The second part of this page displays the data associated with the
redshift data frame for the object you selected. Fields which are empty
in the database are suppressed in the output. These data include
- Name in publication: The name, in NED's standard format, of the
object to which the data apply.
- Coordinates: The object's coordinates and equinox, as published.
- Features targeted: Rest wavelength or frequency of the spectral
used for the observation, if specified, in standard astronomical jargon.
Examples include "HI line," "Optical spectrum," "CIV," and "H K G-band".
- Velocity or redshift: Given first as published, followed by the
units of measurement; then as heliocentric redshift.
- Uncertainty: Given first as published, then as a standard
deviation on the heliocentric redshift.
- Unc(ertainty) Significance: The type of uncertainty reported in
the original publication; e.g. "rms uncertainty", "90% confidence",
"no unc. reported", etc.
- Reference code: The literature source for the present redshift
data frame, in NED's standard 19-byte code (click on the highlighted
reference code to display the full reference).
- Measurement mode
- Spectral range: the observed spectral range. Possible values
|Gamma ray ||X-ray|
|Near IR ||Infrared|
|Far IR ||Sub-millimeter|
- Spectrograph: the observing instrumentation, e.g. "Long-slit
spectrum," "Heterodyne receiver (e.g. 21-cm)," "Grism," etc.
- Features: The number and nature of the spectral features
measured. For multiple objects (e.g. galaxy clusters), the number
of objects measured.
- Technique: The method of measuring the spectrum, e.g.
"Cross-correlation fit to template spectrum," "Mid-point of line
profile at 20% level," "Peak of line," etc.
- Spatial mode: The part of the object measured, e.g. "Systemic
redshift," "Average over multiple objects," "Redshift is for
individual star," etc.
- Obs(ervation) Date: Epoch of observation, if given.
- Reference Frame: Specifies the nature of the redshift or
velocity and any corrections applied to it, e.g. "Heliocentric,"
"Corrected to the 3K microwave background," etc.
- Apex: the velocity and direction of the apex of the reference
frame used to calculate the published redshift, if given. NED
adopts heliocentric redshifts or velocities as published whenever
possible. If not, NED calculates the heliocentric redshift using
the apex as published.
- Qualifiers: Self-explanatory notes pertaining to
- The history of the data (e.g. "from new raw data", "transformed
from previously published data", etc.).
- Adjustments to the data (e.g. "zero-point corrected", etc.).
- Changes introduced by NED (e.g. "obvious typo corrected",
"correction published in errata", etc.).
- Values modified by NED (e.g. "Redshift modified from published
value", "Uncertainty modified from published value", etc.).
- Comments: Other information about the data.
John Huchra at the Harvard-Smithsonian Center for Astrophysics
has kindly supplied more information on the
definition of extragalactic redshifts.
Use your browser's "Back" button to return to the Redshift Data Page.
Back to the Redshift Search Input