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README for spectroscopic catalogs:

Sean Moran, Mar 30 2012
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Each file contains a fits table that loads into IDL as an array of
structures. Each element of the array represents an independent
spatial bin, with measurements contained in the structure tags 
described below. 

For files in "individual" subdirectory:
Spatial bins are constructed to optimize the tradeoff
between S/N and spatial information. All bins have minimum extent equal to
the slit width (1.25" or 1.5", for MMT and APO). S/N per bin is 
initially required to be >15 (per Angstrom), but is relaxed in 
several steps moving outward (i.e., S/N>12 if we've already 
binned >4" worth of slit, etc.)

X_KPC, X_ASEC: Luminosity-weighted position of this spatial bin, 
  in rest-frame projected kpc, and in arcseconds
R_ASEC_IN, R_ASEC_OUT: Each bin represents data co-added from 
  radius R_ASEC_IN to R_ASEC_OUT

For files in "global" subdirectory:
Contain arrays of measurements of spectra binned on several standard 
apertures, as follows:
array[0]:full integrated spectrum
array[1]:R<3arcsec
array[2]:R<R50
array[3]:R>R50
array[4]:R>R90 (exists only if S/N>3)

For all:
   
GASS_ID: Not filled in for the individual fits files, but is  
  used in the combined catalogs to aid in selecting points
  belonging to specific objects

S2N: Signal/Noise (per Angstrom) of the spectrum for 
  this spatial bin. Note that low S/N bins may still have significant
  emission lines detected.
Z, Z_ERR: Measured redshift for this bin, but only *after* rotation 
  curve has been fit and spectral bins have been corrected to zero 
  velocity. I.e, this tells you the how much *residual* scatter there 
  is in the bin-to-bin redshift, and is more sensibly expressed as a 
  residual velocity offset, which is given in V, V_ERR, below
V, V_ERR: residual velocity offset of this bin from the central 
  redshift of the galaxy (km/s). See above 
VMAX: Fitted maximal rotation velocity from functional fit to rotation 
  curve. But the fits frequently fail for galaxies with complex 
  velocity fields, so please check the rotation curves directly before 
  using this number (km/s)
VDISP, VDISP_ERR: Best-fit velocity dispersion of this spectral bin. 
  For bins with low S/N (<15), we populate this field with a median of 
  the VDISP values from the good spatial bins (and set
  VDISP_ERR=999). Keep in mind that a number of factors affect this 
  quantity, including how well we have subtracted off the rotation 
  curve before co-adding. (km/s)

Absorption spectrum measurements:
D4000_N, D4000_N_ERR: Measured D4000_N index and error
LICK_HD_A, LICK_HD_A_ERR: Lick HDelta_A index measured on the
  observed spectrum, so emission line contamination may be present.
LICK_HG_A, LICK_HG_A_ERR: Lick HGamma_A index measured on the
  observed spectrum, so emission line contamination may be present.
LICK_NAD, LICK_NAD_ERR: Measurement of Lick NaD sodium absorption line 
  index, and uncertainty
D4000_N_MODEL: D4000_N index measured on the best-fit *model* spectrum
LICK_HD_A_MODEL, LICK_HG_A_MODEL: HDelta_A and HGamma_A Lick indices
  measured on the *model* spectra, so that any emission line component
  is excluded.
LICK_NAD_MODEL: Na D index meaured on the best-fit model spectrum

Emission line measurements:
Each of the following lines are measured in emission by constructing
an emission-line only spectrum by subtacting the best-fit absorption
line model spectrum from the observed spectrum. We then perform a fit
with each possible line represented by a Gaussian function with width
tied to be the same for all lines, but with height and overall
velocity offset (for all lines together) left as free parameters.
Tags _FLUX and _FLUX_ERR are derived from integrating each Gaussian,
and _EW are found by dividing the flux by the stellar continuum
underneath the line, measured from the absorption line model spectrum
Fluxes in SDSS-like units of 1e-17 erg/s/cm^2/A
H_GAMMA_FLUX, H_GAMMA_FLUX_ERR, H_GAMMA_EW
H_BETA_FLUX, H_BETA_FLUX_ERR , H_BETA_EW
H_ALPHA_FLUX,H_ALPHA_FLUX_ERR,H_ALPHA_EW
OIII_4959_FLUX, OIII_4959_FLUX_ERR,OIII_4959_EW   
OIII_5007_FLUX,OIII_5007_FLUX_ERR,OIII_5007_EW    
NII_6548_FLUX,NII_6548_FLUX_ERR, NII_6548_EW  
NII_6584_FLUX,NII_6584_FLUX_ERR, NII_6584_EW  
In APO spectra only, also have:
OII_3726_FLUX, OII_3726_FLUX_ERR, OII_3726_EW
OII_3729_FLUX, OII_3729_FLUX_ERR, OII_3729_EW
NEIII_3869_FLUX, NEIII_3869_FLUX_ERR, NEIII_3869_EW
SII_6717_FLUX, SII_6717_FLUX_ERR, SII_6717_EW
SII_6731_FLUX, SII_6731_FLUX_ERR, SII_6731_EW

V_OFF, V_OFF_ERR: Velocity offset of the emission line from the 
  redshift of the absorption spectrum  (km/s)
SIGMA, SIGMA_ERR: Velocity width of the best-fit Gaussian to 
  emission lines (Spectral resolution is 50-100km/s)


Derived quantities:
A_V_BALMER, A_V_BALMER_ERR: Internal extinction, expressed as
  magnitudes at V-band (A_V), derived from the Balmer decrement and
  the Calzetti extintion curve. (A_V=1.9655*3.1*Log(Halpha/Hbeta/2.87)
  Note that for bins with S/N(Hbeta) < 10, A_V is determined by coadding
  all such marginal bins (3 < S/N(Hbeta) < 10), deriving A_V from that
  spectrum, and then re-propulating these A_V_BALMER fields with the
  result, and setting error=999. A_V_BALMER=0 and A_V_BALMER_ERR=999
  when 1) no emission is detected, or 2) emission is too low S/N for a
  reliable estimate
H_ALPHA_INTRINS, H_BETA_INTRINS, H_GAMMA_INTRINS: Balmer line emission
  fluxes corrected for dust extinction (using A_V_BALMER)
H_ALPHA_INTRINS_ERR, H_BETA_INTRINS_ERR, H_GAMMA_INTRINS_ERR:
  Uncertainties in Balmer emission flux, also scaled to reflect
  dust-corrected flux values (i.e., to keep S/N constant)
SFR_DENSITY, SFR_DENSITY_ERR: Projected star-formation rate density
  under this bin, in Msolar/yr/kpc^2, and associated
  uncertainty. Derived from the dust-corrected Halpha
  fluxes. SFR_DENSITY is zeroed for bins where the various line 
  ratios indicate AGN-like emission. 
LOG_OH_N2, LOG_OH_N2_LIMIT: Gas-phase metalicity expressed in units of
 12+Log(O/H), derived only from the ratio of NII 6584/Halpha,
 according to the calibration of Pettini & Pagel
 2004. LOG_OH_N2_LIMIT=0 if both emission lines are detected, and =1
 if this metallicity is an upper limit because NII is not detected.
LOG_OH_O3N2, LOG_OH_O3N2_LIMIT: Gas-phase metalicity expressed in units of
 12+Log(O/H), derived from the ratios of NII 6584/Halpha, and
 OIII 5007/Hbeta, according to the calibration of Pettini & Pagel
 2004. LOG_OH_N2_LIMIT=0 if all emission lines are detected, =1
 if this is an upper limit because NII is not detected, =2 if this is
 a *lower* limit because OIII 5007 is undetected (but all other lines
 are detected), and =3 if two or more lines are undetected, and the
 metallicity could be either higher or lower than this.


Absorption model fit quantities:
Note that these tags will be empty for bins with low S/N (<3) in the 
absorption spectrum, and are likely unreliable when S2N<6.
TAUV, TAUV_ERR: V-band dust optical depth, from the best-fit dust 
  component to the absorption line spectrum. Possibly unreliable, 
  so please contact Sean for details before using this quantity 
LIGHT_FRAC, LIGHT_FRAC_ERR, MODEL_AGE: These are ten-element arrays 
  describing the best-fit absorption line model spectrum for this 
  bin. LIGHT_FRAC gives the fraction of the flux that was drawn from 
  each template spectrum of age MODEL_AGE. It is unclear to me how 
  unique these solutions are, and I think they probably have some 
  degeneracy with TAUV, so use with caution.
METALLICITY: Metallicity of model spectra that gave lowest Chi^2. 
  Codes are m42 through m72, as in Bruzual&Charlot nomenclature, 
  with m62=solar. 

Other measurements present only in the COMBINED catalogs:

R50, R90: Radius containing 50% or 90% of the light for the galaxy
that this point belongs to, from SDSS
NUVR: GASS parent catalog NUV-r measurement
MSTAR: GASS parent catalog stellar mass (Log(M/Msolar))
MUSTAR: *local* stellar mass density under every slit segment, as estimated
  by Jing Wang
MUSTAR_GLOBAL: Average stellar mass density within R50 for the parent galaxy
  of this data point
MHI: Log(M_HI) for this point's parent galaxy, if detected, zero otherwise
MH2: Log(M_H2) for this point's parent galaxy, if detected, zero otherwise
LG_FHI: Log(M_HI/M*) for this point's parent galaxy, including upper limits 
  as if they were detections
LG_FH2: Log(M_H2/M*) for this point's parent galaxy, including upper limits 
  as if they were detections
FP_RESID: Residual from the 'HI Plane' of Catinella et al. (2010) 
ROT_CLASS: Rotation curve classification (0:no rotation, 1:normal, 2:slightly
  disturbed, 3:irregular/disturbed, 4:low rotation amplitude)
DECOUPLED_ROT: Evidence for emission line rotation decoupled or 
  counter-rotating with respect to absorption/stellar rotation curve? 
  (0:no/1:yes)
SOLID_ROT: Is this point in the 'solid body rotation' portion of the rotation
  curve, where V rises linearly with radius? (0:no/1:yes)