Which is more realiable: NED or SIMBAD?

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SUMMARY

The discussion centers on the reliability of the NASA/IPAC Extragalactic Database (NED) versus the SIMBAD Astronomical Database in reporting luminosity values for the galaxy M33. NED lists the luminosity as 6.27, while SIMBAD reports it as 5.27, highlighting a significant discrepancy of 1. The participants note that both databases provide the same value for the B band magnitude, yet question which source is preferable for Z or luminosity values. The consensus suggests that the integration methods used by each database for extended objects like M33 may lead to varying results.

PREREQUISITES
  • Understanding of astronomical databases, specifically NED and SIMBAD.
  • Familiarity with luminosity and magnitude concepts in astrophysics.
  • Knowledge of photometric measurements and their implications for extended objects.
  • Basic comprehension of how brightness is integrated over astronomical bodies.
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  • Research the methodologies used by NED for calculating luminosity values.
  • Investigate SIMBAD's approach to reporting Z values and luminosity.
  • Learn about photometric techniques for measuring brightness in extended astronomical objects.
  • Explore comparative studies on the accuracy of data from NED and SIMBAD.
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Astronomers, astrophysicists, and researchers involved in extragalactic studies, particularly those analyzing luminosity and magnitude data from astronomical databases.

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I'm doing some research on M33. NED lists the luminosity as 6.27. SIMBAD gives it as 5.27. First, it looks odd to me that the difference is exactly 1. Second, I've seen other differences comparing identical extragalactic bodies, so which database is more reliable?

Note: it appears I misread the band data. NED and SIMBAD show the same value for the B band magnitude. However, the question still remains: is there a preference between the two for Z or luminosity values?
 
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Depends. How do they integrate the brightness over the surface of an extended object, like M33? There are probably as many answers as there are databases.
 

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