SAGE (v3) MIPS Catalog Definition

SAGE Overview

The Spitzer Space Telescope Survey of the Large Magellanic Cloud Legacy Project Surveying the Agents of a Galaxy's Evolution (SAGE) traces the life cycle of observable matter that drives the evolution of a galaxy's appearance. SAGE has revealed over 6 million sources including ~150,000 evolved stars, ~50,000 young stellar objects and the diffuse interstellar medium with column densities > 1.2×1021 cm -2. The data will provide fundamental insights into the physical processes of the interstellar medium, the formation of new stars and the injection of mass by evolved stars and their relationships on the galaxy-wide scale of the Large Magellanic Cloud.

The SAGE project page can be found here. The survey is described in Meixner et al. (2006). (AJ, 132, 2268). Also provided with the data release is the SAGE data delivery documentation [PDF]

SAGE MIPS Catalog & Full List Criteria

To be included in a Catalog, each source has to meet a number of criteria. The source had to be nearly point like with a correlation value 0.89. In regions where there is a significant structure in the surrounding region (identified as having a sigma > 0.25 in a 120" width square box), the source had to have a correlation value >0.91. There are a small number of sources with 24 um magnitudes between 4 and 8 which have unusually low uncertainties (i.e., high S/N). The origin of these sources is under investigation and seems to be related to edge effects in the AORs. In the meantime, these sources were removed from the 24 um catalogs. Finally, all sources had to have signal-to-noise values >5. The final catalogs likely have a few remaining unreliable sources, but we estimate this to be at the less than 1% error.

The Full Lists contain ALL the sources extracted from the mosaics, thus a user should be aware that it contains spurious sources. The full list may be useful to search for the potential counterparts to known sources.

For more details, see Section 8 of the SAGE Data Delivery Document [PDF].

SAGE MIPS Catalog Column Descriptions

Gator serves the following SAGE MIPS catalogs and archives:
SAGE Winter 2008 MIPS 24 um Catalog Epoch1 (34 columns [29 delivered + 5 IRSA-created], 76,238 data rows)
MIPS 24 um Catalog (34 columns [29 delivered + 5 IRSA-created], 81,519 data rows)
MIPS 24 um Full List (34 columns [29 delivered + 5 IRSA-created], 325,142 data rows)
MIPS 70 um Catalog (33 columns [28 delivered + 5 IRSA-created], 2,003 data rows)
MIPS 70 um Full List (33 columns [28 delivered + 5 IRSA-created], 15,189 data rows)
MIPS 160 um Catalog (33 columns [28 delivered + 5 IRSA-created], 381 data rows)
MIPS 160 um Full List (33 columns [28 delivered + 5 IRSA-created], 4,154 data rows)

In the column descriptions below, ch refers to the MIPS channel (24 um, 70 um, or 160 um).

Column Name Data Type Units Nulls Allowed Column Description
int nUnique identification number of each source in the catalog
char nCharacter string identifier for source catalog
char nCharacter string identifier for the epoch of the observation of the source, i.e. "epoch 1", "epoch 2", "epoch 1+2",...
char nSAGE source designation name.
Designation is
  SST = Spitzer Space Telescope
  M1  = MIPS 24um, M2 = MIPS 70um, M3 = MIPS 160um
  SAGE= LMC Survey project
  1   = epoch 1+2
  C   = Catalog
  J   = 2000.0 epoch
  HHMMSS.SS   Right ascension (hr, min, sec) of source
  sDDMMSS.S   Declination (deg, min, sec) of source

doubledegnRight ascension (J2000)
doubledegnDeclination (J2000)
doublearc secondsnError in right ascension
doublearc secondsnError in declination
int yConfusion Flag for ch, currently unused
doublemJyych flux
doublemJyych 1 sigma error
doublemagych magnitude
doublemagych 1 sigma error
realMJy/sryLocal sky background for ch, computed by measuring the surface brightness at the source location in the source subtracted image. This background includes contributions from the zodiacal light, Milky Way foreground emission, and extended emission in the LMC.
real ych Signal/Noise
int yThe flag currently refers to how many times a source was observed by different AORs in a single epoch. If it was observed more than once, the reported flux is the average of the multiple observations.
double y The value of the correlation indicates how close this source PSF is to a point source. The mathematical definition of the correlation is given in eq. 2 of Diolaiti, E. et al. (2000, A&AS, 147, 335). The value starts at 1 for an exact noiseless match to a point source and reduces as the source becomes more extended and/or the noise increases. The catalog only contains sources which have correlation values above 0.8 except for the special case of close double sources. In this case, the correlation value is set to -1 as it is not possible to compute the correlation value uniquely for each of the two sources. Thus, the correlation value in the catalog can have a value of -1 (for double sources) or between 0.8 and 1 (single sources).
double nNumber of points used to determine the sky values for mmmSkymodech, mmmSigmach and mmmSkewch
double nScalar giving standard deviation of the peak in the sky histogram
double nScalar giving skewness of the peak in the sky histogram
double nScalar giving estimated mode of the sky values
int nRequest key for the 1st AOR within which the source appears (24um catalogs and full lists only)
double nThe average coverage (# of independent observations per pixel)
smallfloat nVersion number assigned by MIPS/IRAC pipeline team
char nDate catalog was produced in the following format, "mon dd yyyy", "Dec 5 2007"
double nx of unit vector on the unit sphere for ra,dec of this source
double ny of unit vector on the unit sphere for ra,dec of this source
double nz of unit vector on the unit sphere for ra,dec of this source
htmIDlong nThe Hierchical Triangular Mesh partition, computed at index level 20, in which this source lies.