Garching DR4 data

Which plates are included?

The full list of PLATEID and MJD can be found here. And the Yanny format file used for the reduction can be found here

The organisation of the data

The files with raw data define the order of the objects and are FITS tables that are sorted with the same number of elements. These files contain the line fluxes, equivalent widths and continuum indices as well as information about the objects such as their redshifts, velocity dispersions and plate, fiber and MJD. While these files can be read in directly using mrdfits in IDL, this is not recommended as some of the files are very big. Use other approaches instead.

Go to the raw data

In addition to these large FITS tables with raw measurements from the spectra, we also have files with derived data - this include gas-phase metallicity estimates, star formation rates, stellar masses and the These files either correspond one-to-one with the raw files, or there is a lookup file associated to the data which can be used to correlate the two.

• Stellar masses, mass-to-light ratios, effective dust attenuations and burst probabilities (Kauffmann et al)
• AGN catalogue, strong line diagnostic ratios and [O III] luminosities (Kauffmann et al/Heckman et al)
• Star formation rates (Brinchmann et al)
• Gas phase metallicities (Tremonti et al)
• Stellar metallicities, ages and masses (Gallazzi et al)

Duplicates

The sample included here has a lot of duplicates - this is very useful for assessing the true uncertainties in measured quantities, see in particular the discussion about uncertainty estimates here. However it is necessary to know which objects are duplicates of each other for analysis of course. This is achived with these files:

• duplicates_new.txt.gz is a duplicates file which was created by finding all objects within 5 arcseconds of the positions of a given object (including self-matches) and whose redshifts differ by no more than 150 km/s. The first column contains the index of the object, the second the number of objects within 5 arcsecs, N, and finally a list of N indices. Thus for instance the object with index 18 has a duplicate object at index 757.
• parsed_duplicates150.txt.gz is a simplified version of the above with the first column having the index number and the second a 1 if the galaxy is to be used and a zero otherwise. The zero means that the object is a duplicate of a preceding galaxy and where we have also required that the redshifts of the two objects differ by no more than 150 km/s. Note that it is not obvious that the first object should be chosen as the one to keep - the one with the highest S/N is another possibility and the user should examine her/his situation accordingly.
• parsed_duplicates500.txt.gz This is the same as the above but this time requiring that the redshifts agree within 500 km/s.

    IDL:

IDL> rdfloat, 'parsed_duplicates150.txt', index, flag
IDL> autohist, z[where(flag eq 1)]

    PDL:

perldl> ($flag) = rcols 'parsed_duplicates150.txt.gz', 1
perldl> bin hist $z->where($flag == 1)

You can get PDL at http://pdl.perl.org.

Other lookup files

We also provide the following files for convenience:

• official_dr4.dat. This has the same number of lines as there are galaxies in our raw files with 1 if the object is in the official DR4 list and a 0 otherwise.
• id_of_dr2_in_dr4.list is a poorly named file which contains for each galaxy in our previous release the index in this present release.
• id_of_dr4_in_dr2.list is the converse of the preceding.
• data_releases.dat contains a single column with the data release number for each object. Be aware that this hasn't been thoroughly checked!
• specobj_id_vs_num.dat.gz is a file giving the specObjID from SDSS DR4 for the objects in the sample. The file has two columns - the first gives the running index in the raw files and the second the specObjID in DR4.

To make sure that the id_* files are understood, here is how to compare the Ha values from our DR2 release with that from the DR4 release (again the reading is suppressed):

   IDL:
	    
  IDL> rdfloat, 'id_of_dr2_in_dr4.list', ind
  IDL> ok=where(ind ge 0)
  IDL> plot, ha_dr4[ind[ok]], ha_dr2[ok], psym=3

   PDL:

perldl> ($ind) = rcols 'id_of_dr2_in_dr4.list'
perldl> $ok=which($ind >= 0)
perldl> points $ha_dr4($ind($ok)), $ha_dr2($ok), {Symbol => -2}

Matching to HST Archive

MAST - STScI's archive facility - provides a list of the HST exposures on-line. For conveniece we have matched this to the positions of our sample as well as the full DR4 imaging data using the Footprint server. click here to get more information.

Note about previous version (relevant only for SDSS members)

For those that used the first incarnation of these files, a note of caution is necessary: The current version includes all plates in the DR4 released to the public and as such is different from the previous data-release we made. A file containing the reverse lookup between the current files (line number) and the ID in the previous release (first column) can be found here.