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This page displays the results of your image search, and shows
the following information:
A summary line showing the name of the object you requested. This
is linked to NED's object database, allowing you to retrieve the
data and literature references currently stored by NED for the object.
A list, preceded by a header line, of the images and maps which NED
currently has for your object. The information given in this list:
- A "postage stamp" preview of the GIF or JPEG version of the image;
clicking on this will retrieve the GIF or JPEG image and -- if your
browser is configured to display GIF and/or JPEG images -- display it.
- The size in KB of the corresponding FITS or JPEG file of the image, and
a "Retrieve" option which allows you to download the FITS or JPEG
image to your machine.
- A "More Information" option which shows you the
FITS header for
FITS-formatted versions of the image, or the caption -- from the source
article -- of the figure or map.
- A "View and Overlay" option with a clickable icon to start the
Aladin image tool, if the image supports this.
This Java applets allows you
to examine the NED image in detail, overlay catalogs on it, and
retrieve data for objects in the field from NED,
SIMBAD,
VizieR,
and other archives.
If the FITS header does not contain enough information to allow
Aladin to operate correctly, a warning
message to that effect appears in this column. In particular, many
images do not contain World Coordinate System (WCS) information, so
cannot be used for any astrometric purpose, including derivation of
accurate positions.
- The waveband in which the image was obtained, in standard astronomical
jargon, and the wavelength associated with that waveband.
- The image size in arcminutes, and -- for
Digitized Sky Survey images -- an option to
change the image size.
- The resolution (pixel size) of the image in arcseconds.
- The telescope with which the image was obtained.
- The literature reference which gives more information on the image.
This is linked to NED's bibliographic database, allowing you to
see the title and/or abstract for the paper.
| Many FITS images have not had WCS information put
into their headers and cannot be used for any astrometric work, including the
derivation of accurate positions. NED includes a warning to that effect in
the image list (see "View and Overlay" above) if the WCS keywords are missing.
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| Please note that the optical images from
Frei et al., AJ 111, 174, 1996
have had all foreground stars and background galaxies removed.
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NED includes images for extended sources from the final
release of the The Two Micron All-Sky Survey. Here is a brief
description of 2MASS, the extended source database, and the extended source
images, courtesy of Tom Jarrett and the 2MASS Team.
The Two Micron All-Sky Survey (2MASS) is a ground-based,
all-sky survey that utilizes the near-infrared band windows
of J (1.11 - 1.36 µm), H (1.50 - 1.80 µm) and Ks (2.00 -
2.32 µm).
Two dedicated 1.3-m telescopes, one covering the most northern declinations
one covering the most southern declinations, were designed specifically for
2MASS to provide all-sky uniformity. The 2MASS database includes both
point and extended (i.e. resolved) sources extracted from "Atlas" images,
each 8.5' X 16' in angular size with 1" pixels. Further information
can be found in the
2MASS Data Release Documentation.
2MASS extracts extended sources in both tabular and image format.
Each extended source includes a small image data cube,
representing the J, H and Ks-band "postage stamp" images
(planes 1, 2 and 3, respectively), extracted from the
full resolution Atlas images. The size of the cube is
dynamically selected, scaled according to the measured angular size
of the extended source, ranging from 21 to 101 pixels.
The pixel scale is 1" per pixel, with a true PSF resolution of
about 2.5" (FWHM). The size of the "postage stamp" images are
adequate for most 2MASS galaxies, but for the largest galaxies
(typically Ks < 9th mag) the images may not be large enough,
resulting in clipped outer isophotes. The full-sized Atlas images
should be consulted for the largest galaxies (size > 2').
The "stamp" image header contains the following information: catalog
identification (e.g. NED name, if any), observation date and time,
equatorial coordinate information, median background level
before removal and the background "noise", PSF "shape" value
(representing the radial extent of the PSF at the time of the
observation), zero point calibration magnitudes and the airmass.
Further information can be found in
Jarrett et al., AJ 119, 2498, 2000
and in
the on-line version of the paper.
For quick viewing, the J, H, and Ks images have been combined to form
a 3-color RGB jpeg image: the J-band image is assigned blue intensity levels,
H green intensity levels and Ks red intensity levels. The color
range was
assigned such that a galaxy of color J-K = 1.0 and H-K = 0.28 appears
white. Galaxies with colors J-K > 1 will appear correspondingly redder,
and galaxies with J-K < 1 will appear correspondingly bluer. The basic
near-infrared properties of galaxies separated by morphological type are
illustrated and described in
Jarrett, PASP 112, 1008, 2000
and in
the on-line version of the paper.
Questions, comments and suggestions regarding this publication may be
directed to the 2MASS Help
Desk or to
Tom Jarrett.
We gratefully acknowledge the many individuals who have already sent images
in machine-readable formats for integration into NED.
Digitized Sky Survey images in NED
appear courtesy of
AURA/STScI.
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