Our Galactic Survey 2013/15
Using the 9 m dish we conducted a sky survey in the light of the 21 cm line. The observations
were done by drift scans: The telescope was pointed to a fixed position for a whole day
while spectra were continously recorded of those regions which passed by. From the known pointing
position and the time the galactic coordinates of every spectrum is computed. The reduced spectra
are added to the corresponding bins in longitude and latitude, so that one obtains an average of
100..600 spectra for each position.
This tool shows the results from several surveys of galactic hydrogen,
at the radio line of atomic hydrogen at 21 cm wavelength.
- DL0SHF: our Survey with the 9 m dish (DF5DU and DF3GJ, Nov.2013 - Feb.2015). Since this
antenna had not yet had a proper pointing correction, the positions are uncertain as much as
perhaps 3°.
- DL0SHFplane: within 30° of the Galactic Plane (in 1° steps)
- DL0SHFallsky: All sky (in 2° steps)
- LAB: (professional) Leiden-Bonn-Argentina Survey with 25 m dishes,
here smoothed to HPBW = 1° and shown in 5° steps
- ISGH3: (amateur-level) Illkirch Survey of Galactic Hydrogen with the
2.3 m ESA-Haystack
Telescope at ISU (DF3GJ, Nov.2010-Feb.2011)
- ISGHcube: with the same instrument, but in 1° steps in galactic latitude (2012)
- GCOSRT+ISGHcube: combined data of two 2.3 m teleskopes: Grove Creek
Observatory (Australia) and ESA-Haystack (France) (DF3GJ, 2013/14)
The data are in a datacube of galactic longitude (from -180° to +180°
or 0° to 360° in steps of 2° or 5°), galactic latitude
(from -30° to +30° in steps of 2°), and radial velocity
from -150 to +150 (or -400 to +400) km/s.
The results are shown as:
- one may chose the longitude range between
0°..360°, -90°..270°, -180°..180°, and -270°..90°
- false colour map of antenna temperature (i.e. the measured intensity) for
galactic longitude and latitude, at a fixed value of the radial
velocity. The colour bar at the right hand side gives the relation between colour
and the value varying linearly between minimum (violet) and maximum (red).
- false colour map of antenna temperature for galactic longitude and
radial velocity, for a given value of the galactic latitude. For glat=0°
one obtains a map from which the spiral arms of the Milky Way become apparent
and the galactic rotation curve, too (the white curve is the limit of the hydrogen
emission for a constant rotation velocity of 230 km/s).
- false colour map of antenna temperature for radial velocity and
galactic latitude, for a given value of the galactic longitude.
From the map at glong=90° one can see that the outer spiral arms lie above
the Galactic Plane, i.e. that the disc of the Milky Way is warped.
- the spectrum at the specified galactic longitude and latitude is a plot
of antenna temperature as a function of radial velocity. The bump near
vrad = 0 km/s is the emission from neutral hydrogen clouds in the
local spiral arm in which the Solar System is embedded. Other bumps are from
other spiral arms.
- the deprojected view of the data for a fixed value of the galactic
latitude shows how the Milky Way would look like when seen from the Northern
Galactic Pole. Similarly, a view with fixed galactic longitude shows a cut
through the disk, perpendicular to the Plane. By assuming a constant rotation velocity,
we can computing from the galactic coordinates and the radial velocity of every pixel
the true distance from the sun of the emitting parcel of gas. By simply associating
the pixel's observed antenna temperature with this true position in the Galaxy
the false colour map is generated.
- The values for the fixed parameter(s) can be changed by the user: enter a new
value in the associated field and hit the return key.
- Mouse position gives the values of all coordinates of the current
position of the mouse.