Foreground Data


Product Name
Coord. System
Projection Type
HEALPix, ring, res 9 (Nside=512)
Original Data Source
Leiden/Argentine/Bonn (LAB) Galactic HI Survey


These data were used in Land & Slosar, arXiv:0706.1703 and given for public use through LAMBDA.

The LAB survey contains the final data release of observations of 21-cm emission from Galactic neutral hydrogen over the entire sky, merging the Leiden/Dwingeloo Survey (LDS: Hartmann & Burton 1997, Cat. VIII/54) of the sky north of -30° with the Instituto Argentino de Radioastronomia Survey (IAR: Arnal et al. 2000A&AS..142...35A and Bajaja et al. 2005, Cat. VIII/75) of the sky south of -25°. The angular resolution of the combined material is HPBW ~ 0.6°. The LSR velocity coverage spans the interval -450 km/s to +400 km/s, at a resolution of 1.3km/s. The data were corrected for stray radiation at the Institute for Radioastronomy of the University of Bonn, refining the original correction applied to the LDS. The rms brightness-temperature noise of the merged database is 0.07-0.09 K. Residual errors in the profile wings due to defects in the correction for stray radiation are for most of the data below a level of 20-40 mK. It would be necessary to construct a telescope with a main beam efficiency of ηMB>0.99% to achieve the same accuracy. The merged and refined material entering the LAB Survey of Galactic H I is intended to be a general resource useful to a wide range of studies of the physical and structural characteristices of the Galactic interstellar environment. The LAB Survey is the most sensitive Milky Way H I survey to date, with the most extensive coverage both spatially and kinematically.

The data were resampled on NSIDE=512 HEALPix grid using nearest neighbour pixel. The NSIDE=512 with approx 0.1 sq deg pixels is probably oversampling the original data, which is stored in approximately 0.25 sq deg pixels. The HEALPix map is a two-channel map: the first channel contains the averaged values of corresponding pixels from the LAB data, while the second channel is weight, i.e. the number of original LAB pixels (i.e. velocity slices) that went into that particular HEALPix pixel. With exception of thin velocity slices, the sky coverage is pretty uniform.

The naming convention is as follows:

LAB_fullvel.fits - the entire velocity range
LAB_LV.fits -30 .. 30 km/s, low velocity
LAB_MV.fits -100 .. -30 km/s, intermediate velocity
LAB_HV.fits -500 .. -100 km/s, high velocity
LAB-cutXXX.fits XXX .. XXX+10 km/s range.
Note that number is the lower limit not the mean.

Please do not hesitate to contact us if you require any further information.

In addition to the standard HEALPix acknowledgement, you must also cite the original data:

Kalberla P.M.W., Burton W.B., Hartmann D., Arnal E.M., Bajaja E., Morras R., Poeppel W.G.L. Leiden/Argentine/Bonn (LAB) Survey of Galactic HI. Astron. Astrophys., 440, 775 (2005)

Citation of Land and Slosar (2007) is also appreciated:

Land, K. and Slosar, A. Correlation between galactic HI and the Cosmic Microwave Background, arXiv:0706.1703, PRD in print

Anze Slosar & Kate Land

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