  The Effelsberg-Bonn HI Survey (EBHIS) is a new 21-cm survey performed with
the 100-m telescope at Effelsberg. It covers the whole northern sky out to a
redshift of z~0.07 and comprises HI line emission from the Milky Way and the
Local Volume. We aim to substitute the northern-hemisphere part of the
Leiden/Argentine/Bonn Milky Way HI survey (LAB) with this first EBHIS data
release, which presents the HI gas in the Milky Way regime. The use of a
seven-beam L-band array made it feasible to perform this all-sky survey with a
100-m class telescope in a reasonable amount of observing time.
State-of-the-art fast-Fourier-transform spectrometers provide the necessary
data read-out speed, dynamic range, and spectral resolution to apply software
radio-frequency interference mitigation. EBHIS is corrected for stray radiation
and employs frequency-dependent flux-density calibration and sophisticated
baseline-removal techniques to ensure the highest possible data quality.
Detailed analyses of the resulting data products show that EBHIS is not only
outperforming LAB in terms of sensitivity and angular resolution, but also
matches the intensity-scale of LAB extremely well, allowing EBHIS to be used as
a drop-in replacement for LAB. Data products are made available to the public
in a variety of forms. Most important, we provide a properly gridded Milky Way
HI column density map in HEALPix representation. To maximize the usefulness of
EBHIS data, we estimate uncertainties in the HI column density and brightness
temperature distributions, accounting for systematic effects.
