GASS Second Data Release: Data Server
Back to AIfA Hi Surveys Server
Please note:
The datacubes are currently limited to 100.000 pixels per image plane (e.g. 25°x25° ). The calculations take a few minutes, the size of the cubes is up to 120 MB. Requests for GASS FITS cubes are queued. You will be notified via email as soon as your data are available.
RFI may still be a problem at a few positions. If you find such cases please send us details about the problem.
In the current data release some of the nearby galaxies have inappropriate corrections for the instrumental baseline. At these positions, the profiles for the Galactic emission may also be corrupt. This work is in progress.
Before submission please check your inputs carefully. If you encounter any problems send an email to hisurvey@astro.uni-bonn.de with a full description.
Method
We provide cubes in Cartesian (CAR) coordinates with "FLAT" projection. For gridding we use a two-dimensional Gaussian with a user-definable width. The kernel FWHM affects both resolution and rms of the FITS cubes - see plots below (e.g. for FWHM = 0.125 deg (7.5 arcmin) one gets an effective beam of 16 arcmin FWHM and a noise level of about 53 mK at intermediate latitudes.) Alternatively you may select an optimized interpolation using a Bessel function tapered by a Gaussian, such as proposed as the default for the AIPS SDGRD routine. Use FWHM = 0 in this case.
Data Products
Cleaned data: Data corrected for stray radiation and cleaned for RFI.
Dirty data: These data have been corrected for stray radiation but no RFI was removed.
Stray radiation: The correction that was removed from the data.
High velocity mode: HVC features may be affected by "bandpass ghosts" offset from emission features by +/- 660 km/s. Such ghosts can be avoided by selecting only apropriate single IF data for |v| > 160 km/s. The disadvantage in this case is that the noise increases by a factor 1.41 for |v| > 160 km/s. You may select the single IF mode for data cubes with |v| > 160 km/s.
Selected velocity range: data are available for |v| = 500 km/s but are incomplete for |v| > 468 km/s. Therefore the default is set to |v| = 468 km/s. The spectral velocity resolution is 1 km/s with a channel separation of 0.82 km/s. The Default is to use the original channel spacing. You may define a larger channel separation: in this case the data are interpolated.
If you want to calculate a column density map simply enter for Δv a large number so that you get only a single channel.
Please specify the parameters of your job below. If not specified otherwise, all angles are given in true angles with respect to the field center.
Please note: this server has recently been abused by repeated submission of requests for huge datacubes with identical setup. If such activities continue we will need to close this server down for public usage.
Observations and first data release are described by McClure-Griffiths et al. (2009). The Second data release, including correction for stray radiation, instrumental baseline, and RFI contamination is described by Kalberla et al. (2010).
References
If you use GASS data products in your research or publications, please reference the following:
McClure-Griffiths, N. M.; Pisano, D. J.; Calabretta, M. R.; Ford, H. Alyson; Lockman, Felix J.; Staveley-Smith, L.; Kalberla, P. M. W.; Bailin, J.; Dedes, L.; Janowiecki, S , Gibson, B.K., Murpy, T., Newton-McGee, K. (2009) ApJS, 181, 398 (http://adsabs.harvard.edu/abs/2009ApJS..181..398M)
Kalberla, P.M.W., McClure-Griffiths, N.M., Pisano, D. J. Calabretta, M. R., Ford, H. Alyson, Lockman, Felix J., Staveley-Smith, L., Kerp, J., Winkel, B., Murphy, T., Newton-McGee, K. (2010) A&A, 512, A14 (Highlight: Gass: The Parkes Galactic All-Sky Survey. II)
Data from the first data release are available at http://www.atnf.csiro.au/research/GASS/index.html
Videos
Below you will find videos showing a sweep in velocity through the data cube of the GASS survey; clean data (22 MB), stray radiation (6 MB), and RFI that was removed (83 MB).
http://www.astro.uni-bonn.de/hisurvey/gass/clean.mpg
http://www.astro.uni-bonn.de/hisurvey/gass/stray.mpg
http://www.astro.uni-bonn.de/hisurvey/gass/dirt.mpg
Additional plots
Effective FWHM resolution of GASS images as a function of the user-definable Gaussian interpolation kernel. For comparison we show the effective resolution obtained by median gridding and by Bessel interpolation (horizontal lines). The Bessel interpolation can be selected by defining FWHM = 0.
Effective rms uncertainties of GASS channel maps with 1 km/s velocity resolution as a function of the user-definable Gaussian interpolation kernel. Crosses indicate fitted values determined at high Galactic latitudes, the solid black line represents upper limits of the noise, valid for most of the positions in the Galactic plane. For comparison we show the effective noise at high latitudes obtained by median gridding and by Bessel interpolation (horizontal lines). The Bessel interpolation can be selected by defining FWHM = 0.
Webinterface created by Lars Flöer