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jobovy / gaia_tools

Tools for working with the @ESAGaia data and related data sets
MIT License
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Matching stars with RAVE #7

Closed jtbuch closed 6 years ago

jtbuch commented 6 years ago

Hi Jo,

I tried to obtain the stars common to RAVE and TGAS using:

  1. gaia_tools.xmatch.xmatch(), and
  2. Considering the non-nan, unique stars directly from the TGAS data included in the RAVE catalog. The code I used was:

temp_indx= np.where(np.isnan(rave_cat['parallax_TGAS'])==False)[0] \ _, tgas_indx= np.unique(rave_cat['parallax_TGAS'][temp_indx], return_index=True)

where len(temp_indx)= 249,603 and matches the value that RAVE claims here: https://www.rave-survey.org/project/ and len(tgas_indx)=210,368 is the number of unique stars that should roughly match the value I obtain from 1.

However, there's only 118329 stars in common after using gaia_tools.xmatch.xmatch() .

I went through your source code and it had no obvious bugs. Any idea why there would be such a discrepancy?

Best, Jatan

jobovy commented 6 years ago

Did you use the method here? That gives me 216,201 stars, not 118,329.

jtbuch commented 6 years ago

This checks out.

It seems that the discrepancy was due to matching with RAVE after putting the selection function cuts on tgas.

Thanks, Jatan

jobovy commented 6 years ago

That makes sense, that would remove about 50% of the match, because the selection function only covers about 50% of the sky.