Guide to NED Search Results Pages

This page displays the results of your object search. The format of the display depends on your search type and the output you requested. HTML-formatted text is designed to be easily read by eye on your computer display, while ASCII and XML VOTable output is appropriate for computerized applications. This help page discusses the output as formatted for the HTML pages, but the comments about the data here also apply to the data displayed in any of the output formats. All formats have headers briefly explaining the data output.

If you searched NED using "Near Name", "Near Position", or "IAU Format", the objects are listed in order of increasing distance from the center of the field. If you used a "By Name" (with the extended name search flag set), "By Refcode", "By Classifications", or "By Parameters" search, the objects are listed in order of increasing Right Ascension. You may choose a different sort order on the search input pages in the "Output Parameter" section.

By default, if fewer than five objects are returned by a search, their Basic Data will be included on the same page as the summary list. If more than five objects are found, click on the sequential number at the beginning of each line to see the Basic Data for that object. The number of objects with detailed data that will be displayed on the same page as the summary list may also be changed in the "Output Parameter" section of the search input pages.

NED's default is to use an ASCII table for the summary list; this displays long lists more quickly. An option on the search input page allows you to choose an HTML-formatted summary list; this is easier to read, but is slower to display long lists.

If you wish to make a finding chart of the objects returned by your search, click the highlighted "Skyplot". This will display a table with the coordinate data for your objects. If you wish, you may modify the table before plotting the data.

Summary list of objects found

Because NED is frequently updated, any of these data may be changed or supplemented when more or better data become available.

Also, because NED's images and spectra are currently stored in different internal databases, we do not yet display the number of images or spectra held for a given object. However, clicking on the "Retrieve" link in the "Images" or "Spectra" columns will retrieve all images or spectra currently in NED.

Detailed information for each object

This section of the output page is preceded by an Index containing links that will display all of NED's data for each object. Each section is blocked off on the screen for readability.

The Index also has a cutout from the Digitized Sky Survey for the object, and -- if there are any data points in NED's photometric database for the object -- a postage stamp version of the Spectral Energy Distribution. These link to the image database and the photometric database, respectively.

Note that the DSS preview images, generated "on the fly" during your object search, are centered on NED's current position for the object. Many DSS images -- specifically for large galaxies, and for groups and clusters -- are included in NED's image database accessible through the image link. These images are independently-generated cutouts centered on earlier, possibly less-accurate positions. While we update these "pre-cutouts" periodically if they differ by more than 10 arcseconds from current positions, there remains the possibility that these "pre-cutout" positions will be centered on slightly different positions than the "on-the-fly" DSS images.

Finally, the Index has a list of links to NED's databases of spectra, redshift-independent distances, literature references, redshifts, diameters, positions, notes, associations, and major catalogs. Click on any of these links to see the additional data.

Here is detailed information about each data block:

• Essential Notes calling attention to e.g. errors in positions or identifications in published catalogs, confused radio sources, etc.
• All the Cross-Identifications in NED for the object, originating from a process using positions (with uncertainties), redshifts, and morphological information, as available in the related catalogs and journal articles. The name prefixes are linked to information about the catalog or paper in which the name originates.
• Coordinates, uncertainty, and reference:
  • The reference code for the position adopted by NED. This is linked to NED's bibliographic database so that you may easily see the full reference and (for papers later than 1988) the paper's abstract.
  • Equatorial and ecliptic positions for B1950.0 and J2000.0. Equatorial positions are given in sexagesimal units as well as in decimal degrees.
  • Galactic and supergalactic positions in decimal degrees.
  • Position uncertainties in arcseconds given as the 95% confidence ellipse semi-axes and position angle; or, for galaxy pairs, triples, and other multiplets, the radius of a circle enclosing the positions of the two or more galaxies.
• Two different estimates of the Foreground Galactic Extinction:
  • First is the total absorption in B magnitudes, based on the prescription of Burstein and Heiles (ApJS 54, 33, 1984 and references therein), modified in the area of M31 to show only the Galactic extinction, not the Galactic extinction affected by the HI emission in M31. No extinction is calculated when |b| < 10 degrees; a few other small gaps occur in the Burstein-Heiles extinction maps (see AJ 87, 1165, 1982) where no extinction can be calculated. See the note below for more information and cautions on using the extinction values returned by your search.
  • This data block also shows the total absorption A_λ in magnitudes at several optical and near-infrared wavelengths, as well as the selective extinction E(B-V), also in magnitudes based on the prescription of Schlegel et al. (ApJ 500, 525, 1998). See the note below for more information and cautions on using the extinction values returned by your search.
• NED's Basic Data for the object including:
  • The heliocentric radial velocity or redshift, with its mean error when known, and reference code (again linked to NED's bibliographic database).
  • Additional parameters whose choice depends on the object type. The self-explanatory parameter headings change depending on the Preferred Object Type of the object. For example:
    • Galaxies:
      1. major and minor axis diameters (in arcminutes),
      2. an indicative optical magnitude, often followed by a single letter indicating the spectral band or filter (e.g. "B", "r")
      3. a morphological type.
    • Small Associations of Galaxies (Pairs, Triples, Multiplets, Groups):
      1. optical magnitude of the brightest member, or the total magnitude of the association,
      2. separation or diameter as appropriate,
      3. descriptive morphology,
      4. number of galaxies or population.
    • Clusters of Galaxies:
      1. magnitude and rank of a cluster member (often the first-, third-, or tenth-ranked galaxy),
      2. diameter in arcminutes,
      3. classification or type, and the classification system,
      4. indicative population or richness class.
    • Quasars:
      1. indicative optical magnitude,
      2. description (e.g. "blazar", "BSO", "Sy1").
    • Infrared Sources:
      1. log(flux density S) in mJy; or magnitude, flagged with "m" or with band pass or filter,
      2. wavelength in microns for the flux density,
      3. second log(flux density S) in mJy, or another magnitude,
      4. wavelength in microns for the second flux density,
      5. origin of the source (e.g. "IRAS FaintSrcCat(v2)").
    • Radio Sources:
      1. log(flux density S, in mJy),
      2. frequency (in GHz) for the flux density,
      3. spectral index, for S=A*freq^Index^,
      4. radio morphology (e.g., head-tail, double-lobe),
      5. size of source (in arcmin).

  PLEASE NOTE

  NED's Basic Data -- diameters, magnitudes, morphological types, flux densities, spectral indices, cluster populations or richnesses, and so forth -- are generally NOT on homogeneous systems. While we have used data from large compilations such as the Sloan Digital Sky Survey, The Third Reference Catalogue of Bright Galaxies (RC3), the Hewitt-Burbidge compendia of QSO's, or the Abell catalog of rich galaxy clusters whenever possible, there are many hundreds of thousands of extragalactic sources represented in NED that are not listed in these more specialized catalogs. Thus, we have taken basic parameters for these other objects from available literature sources. We give preference to large catalogs (e.g. SDSS, 2MASS, APM, IRAS, CGCG, UGC, 87GB) over shorter lists, but the data have not been reduced to homogeneous systems. The Basic Data values are intended only to provide convenient, representative, first-look parameters for the object. Most objects in NED have more extensive, detailed, multi-wavelength measurements for redshifts, photometry, and diameters available using links in the Index section of the results page.

• A summary table of Redshift-Independent Distances showing the mean distance modulus (in magnitudes) and metric distance (in megaparsecs) with their standard deviations, and the minimum and maximum values. There is also a link to the Detailed Listing of individual values in NED's redshift-independent database.
• Derived Values based on the object's redshift (if known) and position:
  • Calculated and Corrected Velocities, with errors:
    1. V (Heliocentric) in km/s with its error (if known) and source, calculated from V = z/c. No relativisitc correction is applied to these apparent redshifts (see John Huchra's discussion of extragalactic redshifts for more information), so velocities in excess of the speed of light can be displayed here.
    2. V (Galactocentric GSR) in km/s calculated as in RC3.
    3. V (Local Group) in km/s based on the formulation by Karachentsev and Makarov (AJ 111, 794, 1996).
    4. V (3K CMB) in km/s using the CMB dipole model presented by Fixsen et al. (ApJ 473, 576, 1996).
    5. V (Virgo Infall only) based on the local velocity field model given in Mould et al. (ApJ 529, 786, 2000) using only the term for the influence of the Virgo Cluster.
    6. V (Virgo + Great Attractor Infall only) again based on the local velocity field model given in Mould et al. (ApJ 529, 786, 2000) using the terms for the influence of Virgo Cluster and the Great Attractor, but not the Shapley Supercluster (we thank Jim Condon for his code for this model, on which we have based ours). See Mould et al. Appendix A or click here for parameters of their local velocity field model.
    7. V (Virgo + Great Attractor + Shapley Supercluster), once again based on the local velocity field model given in Mould et al. (ApJ 529, 786, 2000) using the terms for the influence of the Virgo Cluster, the Great Attractor, and the Shapley Supercluster.
    The errors in the model parameters for each correction are added in quadrature to the error in the galaxy's redshift as follows: 4% of the GSR correction, 6% of the Local Group correction, 7% of the 3K CMB correction, and 7% of the velocity field correction.
  • Hubble Flow Distances and Distance Moduli, with their errors, calculated from the apparent corrected velocities using the cosmological parameters that you chose on the search input page (defaults are H₀ = 73 km/s/Mpc, Ω_matter = 0.27, and Ω_vacuum = 0.73). No derived distances are given if the corrected velocity is negative.
  • Scale at these Hubble Flow Distances in parsec/arcsec, kiloparsec/arcsec, kiloparsec/arcmin, and megaparsec/degree.
  • You may search for physical companions with known redshifts with an "Environment Search". The default values are calculated to correspond to 750 kpc at the distance of the galaxy, and to be plus or minus 500 km/s. You may change these values by entering you desired numbers in the boxes. Click "Submit Environment Search" to initiate the search.
  • Several quantities derived from the redshift corrected to the reference frame defined by the 3K background, and further corrected using the cosmological parameters that you chose on the search input page (again, defaults are H₀ = 73 km/s/Mpc, Ω_matter = 0.27, and Ω_vacuum = 0.73). We thank Chris Burns (OCIW) for the code behind these calculations. Further explanation of the calculated quantities is available through Ned Wright's Cosmology Calculator web site, and through Alberto Cappi's CosmoTools web site.

    PLEASE NOTE

    Calculated distances and scales for galaxies with heliocentric velocities less than 500-700 km/s -- particularly in the Virgo Cluster area -- should be treated with considerable caution. Many of these nearby galaxies have individually-determined distances given above in the list of redshift-independent distances. These are generally much more accurate than the calculated distances presented here, and should certainly be used in preference to the calculated distances.

  • If you wish to change the cosmological parameters used to calculate the derived values, you may do so by entering them in the appropriate boxes. WMAP Three-Year (Spergel et al. ApJS 170, 377, 2007) and Five-Year (Komatsu et al. ApJS 180, 330, 2009) values may be entered by clicking the appropriate buttons. You may also choose which redshift/velocity correction is used as input for the calculations of luminosity distance and cosmology-corrected quantities (the default is the redshift corrected to the 3K cosmic microwave background). After you have made your selections, click the "Submit Changed Hubble Parameters" button; the page will refresh with the new derived values displayed.
• Links to External Archives and Services.

  This section of your NED results contains two subsections distinguished by the nature of their hyperlinks.

  Links listed under "Data Directly Related to Object Names" are made as follows:

  The list of NED names for an object returned by your search is compared with a list of related on-line astronomical services that are specific to the survey or catalog associated with the NED names. For example, if the object has an NVSS name, a 2MASS name, and a UGC name, only links to data services referring to NVSS, 2MASS, and UGC are listed. Click on the links to access these external data services.

  Because these links are keyed on object names based on multi-wavelength cross-identifications, the data returned are relevant to your object with a high degree of certainty and reliability (but see Notes and Caveats below). Services currently accessed include catalog queries through VizieR (CDS) and LEDA (Lyon Extragalactic Database); and image and catalog data for large surveys such as 2MASS (IRSA, IPAC), FIRST (NRAO), and NVSS (also at NRAO).

  The second subsection lists links under "General Archive Resources". These are not necessarily tied to a specific name prefix. When the service supports a name-based query, the primary NED name (the first name listed in the Object Names columns above) is used; otherwise, the query is based on the position of the object. These external archives may or may not contain observations relevant to the NED objects in your list; you will have to run the query and explore the results. (Again, see Notes and Caveats below).

  On-line resources currently queried here include infrared mission archives at IRSA (2MASS, MSX, IRAS), optical and UV mission archives at MAST (HST, IUE, EUVE, GALEX, etc.), high energy mission archives at HEASARC (HEAO, GINGA, EXOSAT, EINSTEIN, XTE, ROSAT, etc.), the IMPReSS tool used to visualize observation coverage maps (GSFC), the Astrobrowse tool (HEASARC) used to explore astronomical resources, the SDSS Sky Server, the UZC Spectral Archive at SAO, the NVSS image archive at NRAO, the ATNF Observation Log, the VLA Observation Log, and a name-based object query to SIMBAD.

  Notes and Caveats

  NED does not automatically poll all of the above services and include a link only if data are available. This would take too much time -- we want to display your NED query results as quickly as possible.

  While many queries to external services will return relevant data, some queries may return nothing because observations for the given object (or near its position) may not be available in all archives.

  Results from an external archive may be unexpected. For example, a query to MAST on "3C 279", returns not only IUE, EUVE, and HST observations of this QSO, but also an observation of the planet Mars with the GHRS instrument on HST. This is not an error, but is due to the fact that MAST -- and many other archive services -- do position searches rather than name searches. The NED name is converted to a position and a default radius, and all observations within that search radius are returned. In this example, it may be of interest to know that Mars has appeared close to 3C 279. This could spur, for example, an archival investigation into possible occultation measurements with resultant information about the apparent size of the QSO, Mars's atmosphere, etc.

  Objects with name prefixes or suffixes added by NED, such as "NED01", square brackets, colons, etc., are stripped off before building the link to the external archive. Typically, this means that the search will return data relevant to the parent object and not to an object with name prefixes or suffixes. For example, the link to a catalog search for "NGC 3690 NED01" becomes "NGC 3690", so the data returned by the external service will refer to NGC 3690.

  Also note that the availability of these external resources is under control of the corresponding external servers. Thus, the response time to your query will depend on the state of the external server -- its Internet connectivity and its usage load, and even whether it is currently on-line or not.

  Finally, a few of the SDSS spectroscopically-observed objects will not link correctly with the SDSS server through the "External Archives and Services" link that appears for them in this section (an example is SDSS J132958.87+471557.4, a knot near the nucleus of NGC 5195 = Messier 051b). These are usually found in sections of the SDSS that have been masked because of the presence of nearby bright objects (in the case of this example, Messier 051 itself).

Notes on Coordinates in NED

The positional uncertainty is given as the semi-major and semi-minor axes of the 95% confidence ellipse, and the position angle (East of North) of the major axis of the ellipse. The two-dimensional 95% confidence ellipse corresponds to 2.5 sigma (where sigma is the standard deviation). Note that this is not the same as the one-dimensional 95% confidence interval; that corresponds to 1.96 sigma, assuming a normal (Gaussian) distribution of residuals about the mean value.

A few large lists of positions which do NOT appear in print are given bibliographic reference codes which point to papers explaining the measurement and reduction techniques. For example, positions taken from the Guide Star Catalog carry a reference pointing to "The Guide Star Catalog. II. Photometric and Astrometric Models and Solutions" in AJ 99, 2059, 1990; and positions for reference galaxies in the Lick Northern Proper Motion survey carry a reference to "Lick Northern Proper Motion Program. I. Goals, Organization, and Methods" in AJ 94, 501, 1987.

Some unpublished positions measured by members of the NED team are referenced as "Internal NED Report", followed by the team member's name.

Display Precision

On most NED pages, the displayed precision of a position is dependent upon the 95% confidence ellipse (2.5 times the standard deviation) assigned to the semi-minor axis of the position uncertainty ellipse. Here is a table, with examples, showing the displayed coordinate precision for different ranges of uncertainty.

95% CI	CI/2.5	RA	Dec
(arcsec)	(arcsec)
>= 750	300	04h30m33s	+05d15m
>= 75	30	04h30m31s	+05d15.0m
>= 12.5	5	04h30m31.6s	+05d15m00s
>= 1.25	0.5	04h30m31.60s	+05d14m59.6s
>= 0.125	0.05	04h30m31.605s	+05d14m59.59s
>= 0.0125	0.005	04h30m31.6048s	+05d14m59.594s
>= 0.00125	0.0005	04h30m31.60485s	+05d14m59.5943s
>= 0.000125	0.00005	04h30m31.604856s	+05d14m59.59428s
< 0.000125	0.00005	04h30m31.6048560s	+05d14m59.594280s

For positions displayed as decimal degrees, we use the following rules:

CI/2.5	Digits displayed
(degrees)	after decimal point
0.5	1
0.05	2
0.005	3
0.0005	4
.
.
.
5.0E(-n)	n+1
where n <= 8.

Only the calculator and the initial object list page displayed after an object search do not follow these rules. The calculator always displays 7 significant digits in RA seconds and 6 in Dec (i.e. a 95% confidence ellipse of >= 0.00125 arcsec), while the object list always gives 3 significant digits in RA seconds and 2 in Dec (95% CI of >= 12.5 arcsec).

If you request data via a batch job, the positions will be in the fixed format
04h30m31.60s +05d14m59.6s
regardless of the accuracy stored in NED.

Notes on Galactic Extinction

Galactic extinction is presented as total absorption A_λ in magnitudes, as calculated by two different methods.

The Burstein-Heiles total B-band absorption is given as A_B = 4 E(B-V) + 0.005, consistent with A_B = 4 E(B-V) in Burstein and Heiles (ApJS 54, 33, 1984 and references therein) but with a small adjustment to the zero point (Burstein, 1988, private communication). Burstein and Heiles used HI column densities combined with galaxy counts to determine the extinction.

The individual values of the total absorption at each waveband are calculated from the list of A/E(B-V) in Table 6 of Schlegel et al (ApJ 500, 525, 1998) along with their estimate of E(B-V) calculated from COBE and IRAS maps as well as the Leiden-Dwingeloo maps of HI emission. We have adopted from their table the Landolt UBVRI filters for the optical total absorptions, and the UKIRT JHKL' filters for the near-infrared total absorptions. Please note that Schlegel et al. calculated the values of A/E(B-V) for these specific bandpasses using a spectral energy distribution for an unredshifted elliptical galaxy. Therefore, the numbers displayed by NED for a specific object may not be appropriate for other closely related bandpasses or other galaxy types. The total absorptions are nominally consistent with an average R = A/E(B-V) = 3.1, but do not agree numerically with this average. See Appendix B of Schlegel et al (ApJ 500, 525, 1998) and references therein for additional details. See Cardelli et al. (ApJ 500, 525, 1998) for other conversion factors.

Note, too, the list of cavaets in Appendix C of Schlegel et al. In particular, they call attention to the areas within the Holmberg radii of LMC, SMC, and M31 -- total reddenings through these large galaxies are replaced by Galactic reddenings toward them. They also note that no contaminating sources at Galactic latitudes |b| < 5 degrees have been removed from their dust maps, so calculated reddenings at these low latitudes are especially uncertain and untrustworthy. They state that the formal uncertainty in normalizing the dust column density to the reddenings is 10%; this should probably be taken as a lower limit on the formal error of the calculated reddenings at |b| > 5 degrees.

A few other galaxies may have unreliable Galactic extinction values as well. An example is M82 (see Johnson et al ApJ, 697, 1138, 2009, Section 6.3) where emission by dust within the galaxy has apparently affected the Schlegel et al estimate of the foreground Galactic extinction. We thank L. C. Johnson for alerting us to the M82 problem.

Willick (ApJ 522, 647, 1999) adds the following notes and caution concerning the output of the Galactic extinction calculator:

"Two all-sky Galactic extinction maps are presently available: the older Burstein-Heiles (Burstein and Heiles, ApJ 225, 40, 1978, hereafter BH, and AJ 87, 1165, 1982) maps, which are based on 21-cm column density and faint galaxy counts, and the recently completed Schlegel, Finkbeiner, and Davis (ApJ 500, 525, 1998, hereafter SFD) maps, based on IRAS/DIRBE measurements of diffuse IR emission. The SFD extinctions have been favored in several recent analyses and, indeed, were used in Paper I (Willick, ApJ 516, 47, 1999). Unlike BH, the SFD extinctions are based directly on dust emission and have comparatively high spatial resolution. However, it has not been established beyond doubt that they are free of systematic errors, such as could arise from the presence of cold dust invisible to IRAS. The BH extinctions are also vulnerable to possible systematic effects, such as a variable dust-to-gas ratio and galaxy count fluctuations. Thus, it seems prudent to use both methods, or linear combinations of them, and see what effect this has on the results."

Finally, we note that we have replaced the Burstein-Heiles extinction toward M31 with values that are not affected by the HI emission of M31 itself (see ApJS 54, 33, 1984 for a discussion). This affects not only M31, but several thousand objects within that galaxy. Specifically, we have replaced "data word numbers" 402-405 in "physical record number" 20 in the Burstein-Heiles reddening file "redsouth.dat" with the E(B-V) values 0.068, 0.071, 0.074, and 0.077 (interpolated from surrounding areas), respectively. The original values were 0.043, 0.034, 0.024, and 0.045. (We thank Tod Lauer for alerting us to this problem.)

One additional note: The zero points of these two reddening laws differ by 0.02 magnitudes in E(B-V), with Schlegel et al. adopting a higher zero point than Burstein and Heiles. (We thank David Burstein for this note.)

Notes on the Local Velocity Field Model

V (Local Infall) is calculated from Equation A2 of Mould et al. (ApJ 529, 786, 2000), with signs corrected:

V_{(Local Infall)} = V_Sun + ΔV_LG + ΔV_Virgo + ΔV_GA + ΔV_Shapley

Each of the Δ terms represents one of the velocity corrections for the attraction of a nearby mass concentration. As explained above, we adopt the formulation for the Local Group correction from Karachentsev and Makarov (AJ 111, 794, 1996). Otherwise, we follow Mould et al. explicitly by adopting their three attractors as detailed in their Table A1 reproduced, with corrections, here:

Cluster	RA	Dec	VH	VLG	VField	Radius	VRange
Virgo	12h28m19s	+12d40.0m	1035	957	200	10	600 - 2300
Great Attractor	13h20.0m	-44d00m	4600	4380	400	10	2600 - 6600
Shapley	13h30.0m	-31d00m	13800	13600	85	12	10000 - 16000

All velocities in the table are in km/s. V_H is the observed mean heliocentric velocity of the cluster, V_LG is the mean cluster velocity corrected to the center of the Local Group using the standard 300 sin(l)cos(b) calculation, V_Field is the adopted model infall velocity at the position of the Local Group, "Radius" is the adopted radius of the cluster in degrees, and V_Range is the heliocentric velocity range within which cluster galaxies are found.

This model assumes that all galaxies within "Radius" of the center of the cluster (given by RA and Dec), and within the given velocity range, are cluster members. Any galaxy meeting these criteria is assigned the mean heliocentric velocity of the cluster for calculation of its distance.

Note that the declinations of the Great Attractor and the Shapley Supercluster given in Table A1 of Mould et al. should be negative, and that the minus signs in their Equation A2 should all be positive.

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