HerMES catalogues - Data Release DR2

Contact: hedam@lam.fr
L. Wang, A. Smith, V. Buat, C. Clarke
2012-04-03 (updated 2015-04-30)

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This is the README file for the catalogues associated with the second
Herschel-SPIRE/SAG-1/HerMES public data release (DR2).  The HerMES
programme is presented in Oliver et al (2012).

The HerMES second data release provides three different catalogue types
for each field: StarFinder and SUSSEXtractor  mono-wavelength
catalogues and a  band-merged xID one.

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FILE NAMES

The file names indicate the level, field, catalogue type and version
number (here DR2).

<level>-<field>_<type>_DR2.fits.gz (or .xml.gz for VO-table format)

Level: defined in Oliver et al. (table 1). Each level corresponds to an
initial nominal depth of the survey, from Level 1 (L1, deep) to Level 6 (L6,
shallow). Cluster observations are refered as CD (deep), CS (shallow) and CH
(high-z).

The type is:

 - SCAT250, SCAT350 and SCAT500 for 250 µm, 350 µm and 500 µm
   Starfinder catalogues

 - SCAT250-SXT, SCAT350-SXT and SCAT500-SXT for 250 µm, 350 µm and 500 µm
   SUSSEXtractor catalogues

 - xID250 for band-merged catalogues extracted on Starfinder 250 µm
   positions

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SOURCE NAMING CONVENTION

Here is the naming convention used to identify unambiguously each
source (IAU name):

xHERMES Syyy zz d  JHHMMSS.s+DDMMSS

x:    the version number of the catalogue (here 2)

Syyy: the wavelength of the map where the source was identified
      'S250', 'S350' or 'S500' for SPIRE catalogues

zz:   the pipeline used to identify the source 'SX' for SUSSEXtractor,
      'SF' for Starfinder

d:    'D' to identify a source found on a deep map where a shallow map
      is also available (nested fields), nothing otherwise

JHHMMSS.S+DDMMSS: coordinates, Equinox J2000

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StarFinder CATALOGUES

StarFinder is an IDL iterative source finding and fitting program, originally
designed for crowded stellar fields analysis (Diolaiti et al. 2000). As such,
StarFinder is expected to do better at de-blending sources and finding faint
sources around bright sources than SUSSEXtractor (Wang et al. 2014). We use
a Gaussian shaped PSF with the FWHM set to 18.15, 25.15 and 36.3 arcsecs at
250, 350 and 500 micron respectively.

Single-band StarFinder catalogues are provided at 250, 350 and 500 micron with
a photometry based on a cross-identification (XID) method. Positions of the
sources are obtained with StarFinder and fluxes are extracted with the HerMES
XID code at the positions of StarFinder sources. For details of the HerMES XID
pipeline, please refer to Roseboom et al. (2010) (for more details, Wang et al.
2014)

Column descriptions (for 250 µm catalogues, adjust for 350 and 500):

iau_name          -        IAU Name

ra                deg      Right Ascension (J2000)

dec               deg      Declination (J2000)

f250              mJy      Flux density

e250              mJy      Instrumental error in flux density

et250             mJy      Total error (instrumental + confusion) in
                           flux density

chi250            -        Local reduced chi2 statistic of photometry fit
                           in 11x11 pixel window

gid               -        ID of the segment  where the source is

gsize             -        Number of sources in the segment gid

bkg250            mJy/Beam Background substracted from map

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SUSSEXtractor CATALOGUES

SUSSEXtractor is a simple peak finder written in IDL and Jython. For more
details on the SUSSEXtractor source extraction method, please refer to Savage
& Oliver (2007) and Smith et al. (2011). We use a Gaussian shaped PSF with the
FWHM set to 18.15, 25.15 and 36.3 arcsec at 250, 350 and 500 micron
respectively.

Single-band SUSSEXtractor catalogues at 250 (PSW), 350 (PMW) and 500 (PLW)
micron are provided for all the fields in the DR1.

Column descriptions:

iau_name          -        IAU Name

ra                deg      Right Ascension (J2000)

raerr             deg      Uncertainty on Right Ascension

dec               deg      Declination (J2000)

decerr            deg      Uncertainty on Dec

flux              mJy      Flux density

fluxerr           mJy      Formal uncertainty on flux (instrumental noise)

quality           -        Signal-to-instrumental noise ratio (flux/fluxerr)

fluxerrtotal      mJy      Total uncertainty in the source flux, due to
                           confusion and instrumental noise

snr               -        Signal-to-total noise ratio (flux/fluxerrtotal)

centralregion     -        1 if source lies within a well defined central
                           region of the map, 0 otherwise

fluxhalfdata1     mJy      Source flux, as measured using a map based on the
                           first half of the data

qualityhalfdata1  -        Signal-to-instrumental noise as measured using a
                           map based on the first half of the data

fluxhalfdata2     mJy      Source flux, as measured using a map based on the
                           second half of the data

qualityhalfdata2  -        Signal-to-instrumental noise as measured using a
                           map based on the second half of the data

The 'halfdata' maps are available for the fields from the 'complementary data'
page of HeDaM web site.

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xID CATALOGUES

Band-merged StarFinder catalogues with xID multi-band (250, 350 and 500
micron) fluxes at the positions of the StarFinder 250 micron sources. We use a
Gaussian shaped PSF with the FWHM set to 18.15, 25.15 and 36.3 arcsecs at 250,
350 and 500 micron respectively.

Column descriptions:

iau_name          -        IAU Name

ra                deg      Right Ascension (J2000)

dec               deg      Declination (J2000)

f250              mJy      Flux density at 250 µm

e250              mJy      Instrumental error in flux 250 µm density

et250             mJy      Total error (instrumental + confusion) in
                           250 µm flux density

chi250            -        Local reduced chi2 statistic of 250 µm photometry
                           fit in 11x11 pixel window

f350              mJy      Flux density at 350 µm

e350              mJy      Instrumental error in flux 350 µm density

et350             mJy      Total error (instrumental + confusion) in
                           350 µm flux density

chi350            -        Local reduced chi2 statistic of 350 µm photometry
                           fit in 11x11 pixel window

f500              mJy      Flux density at 500 µm

e500              mJy      Instrumental error in flux 500 µm density

et500             mJy      Total error (instrumental + confusion) in
                           500 µm flux density

chi500            -        Local reduced chi2 statistic of 500 µm photometry
                           fit in 11x11 pixel window

gid               -        ID of the segment  where the source is

gsize             -        Number of sources in the segment gid

bkg250            mJy/Beam Background substracted from 250 µm map

bkg350            mJy/Beam Background substracted from 350 µm map

bkg500            mJy/Beam Background substracted from 500 µm map


Notes

 In case of nested fields, (cf. the readme for the maps and the
 HerMES_DR2_nested_fields.pdf document), the image associated with the
 catalogue is the full nested one, thus much larger than the catalogue
 coverage. The full description of the fields is given in the readme for
 the maps.

 For L1-ECDFS, the catalogues contain an extra column named 'Flag', which
 contains "goods-s" for the sources extracted in the deepest part of the
 nested map, corresponding to the GOODS-S field (AOR 13).

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REFERENCES

  Diolaiti et al. 2000, SPIE 4007, 879
  Oliver, S. et al. 2012, MNRAS 424, 1614
  Roseboom, I.G., et al. 2010, MNRAS, 409, 48
  Savage, R.S., & Oliver, S. 2007, ApJ, 661, 1339
  Smith, A.J. et al. 2012, MNRAS, 419, 377
  Wang, L. et al. 2014, MNRAS, 444, 2870