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I am looking for a catalog of low redshift galaxies (preferably SDSS) with information on line fluxes and stellar mass. My Google searches keep pointing me to work by the Portsmouth group, so I downloaded some of the fits files listed at the bottom of the page, but there are no line fluxes in those files, even though they seem to suggest that the line fluxes are being made available... I was just wondering if what I'm looking for is publicly available and if I'm looking in the right place? Their page links to a table that lists all the key words I would like to use, but I'm not sure how to obtain the data.

In one of the files I downloaded (portsmouth_emlinekin_full-26.fits) there's a column called BPT, which lists the BPT classification (Seyfert, LINER, Star forming...), so I was expecting to also find the "building blocks" ([OIII], [NII], [SII], [OII], Halpha and Hbeta line fluxes) of the BPT diagram. Is it usually necessary to contact the authors for stuff like this?

Would be very grateful to learn about using publicly available survey data from a more experienced scientist :)

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From what I can see, you already found what you were looking for. The table you linked is the description of the data available in the Catalog Archive Server (CAS) database. All you have to do now is use those table names (it seems that masses are on different tables, here and here) and then search whatever you want. If you do not have constraints, you could just search by sky regions, but I would recommend you to use the SQL queries as you can manually select columns an even join tables. Just to give you a quick example:

SELECT TOP 10
   p.specObjID, p.ra, p.dec, p.z, p.bpt, p.Flux_NeV_3425
FROM emissionLinesPort as p
WHERE 
   p.z BETWEEN 0 AND 2

You will get a table with the first 10 results that have a redshift between 0 an 2. Columns will be ID, right ascension, declination, redshift, classification and flux of [NeV] 3425 (everything described in the table you linked). Note that for masses you would have to change the table by editing emissionLinesPort and using stellarMassStarFormingPort or stellarMassPassivePort instead (as well as change the columns accordingly).

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