Some useful astronomical links

NASA Extragalactic Database (NED)

NED (http://nedwww.ipac.caltech.edu/; telnet ned.ipac.caltech.edu username: ned) contains information about 800,000 extragalactic objects which includes 1.3M names and almost a million bibliographic references (since 1983), abstracts (since 1988) and notes on the sources. NED is the place to start on a project that includes extragalactic sources and is freely available to any person with an Internet account.

NED includes an object-based database, it organizes all information around individual extragalactic objects not by catalogs (Helou et al 1995).
The master list was culled from around 40 major astronomical catalogs plus several lists from the literature (PG quasars or compact groups of galaxies, for example). NED team members continuously produce the cross identification of each source in the list.

The information for each of the sources (if available) includes:

• name(s)
  
• object type (from the discovery method or original catalog)
  
• position
  
• photometric measurements in as many bands as available and

• radial velocity or redshift
  
• cross identification
  
• references
  
• catalog notes

NED also includes abstracts of dissertations devoted to extragalactic studies defended since 1980. Dissertation titles and authors only are available for theses since 1909.

It is very easy to search for information in NED. Little information is needed about the object as the query can be started by name, near a position (in equatorial, ecliptic, galactic or super-galactic) IAU formatted name, near the position or by object type. The list can be created also in such a way that object types are excluded from those retrieved inside a searching radius.

If the list is long, a batch job request can be submitted. The user will send an e-mail message to nedbatch@ipac.caltech.edu and NED will reply with the desired information in one or more messages. NED can also be run in a client mode, making it possible to access the database from within user programs.

To complete the search an image of the object (or the region) can be obtained. NED can produce images from the Digitized Sky Survey, infrared images from the IRAS survey and radio maps.