Research
In my research I deal with the 21 cm emission of neutral hydrogen, HI. I am part of the survey team of the Effelsberg-Bonn HI Survey and work mostly on the data reduction process and the extragalactic emission.
Topics
Radio Frequency Interference Mitigation
Performance of the algorithm as determined by simulations. About 97% of all interference is found at the noise of the data. The false detections for this simulation are only 0.3%.
Every radio astronomical measurement is affected by man-made interference. This radio frequency interference (RFI) can be emitted by virtually every electronic device; either purposefully or accidental. In all cases, one has to identify and excise those signals from the raw data to yield a clean dataset. Many interference signals have amplitudes that are many orders of magnitude higher than the actual astronomical signal. The most hurtful type of interference is the one, that is barely visible in raw data and gets more pronounced during the averaging in the data reduction process.
During my diploma thesis, I've developed an RFI detection algorithm that makes use of the fact, that in multi feed observations, we have several feeds, all in the same RFI environment. This fact can be used to improve the sensitivity and also the robustness of the RFI detection scheme.
The details and also examples of application of the RFI detection algorithm are discussed in Flöer et al. (2010), as part of the proceedings to the RFI 2010 workshop.
Since the original publication, the algorithm has been improved in both sensitivity and speed. Even though the code was tailor-made for EBHIS data, it should, in principle, work with every telescope that has a similar observing mode (e.g. focal plane arrays, closely packed dipole arrays, etc.).
Source Finding for Spectroscopic Surveys
To fully exploit the scientific potential in future HI surveys conducted with the SKA and its pathfinders, an automatic source detection algorithm is of cardinal importance. This algorithm needs to be both sensitive and reliable.
As part of my Ph.D. thesis, I've developed a three dimensional source finding algorithm based on wavelet denoising. The developed algorithm is applicable to any spectroscopic imaging survey. Its first application will be the source finding for EBHIS and has also been investigated as a potential source finding algorithm for ASKAP. The performance and implementation of the algorithm is discussed in Flöer et al. (2011).
Extragalactic HI Science with EBHIS
The Effelsberg-Bonn HI Survey (EBHIS) is a novel HI survey of the whole northern sky (δ > -5°). Once finished it will be combined with the Galactic All Sky Survey (GASS) to become the database for galactic neutral hydrogen. In addition to that, the usage of modern FPGA-FFT spectrometers and a large bandwidth of 100 MHz enables EBHIS to observe both the galactic and the extragalactic neutral hydrogen in one pass. EBHIS will therefore also become the northern equivalent to the HI Parkes All Sky Survey (HIPASS).
This will allow to calculate the HI mass function for the local universe with increased precision, especially for the low mass end. Together with the HIPASS sample this also enables a calculation of the HI mass function with the cosmic variance eliminated.
We anticipate a first data release in 2013.