Peiyuan Mao's Summer 2008 Progress page
- I have only been involved in the ALFALFA Project since mid-June. Thus, my understanding of the project itself and my contributions so far are extremely limited.
- In this project, I will look at the galaxy clusters at the high redshift end and study the HI content of the signals. Statistics will be compounded for the clusters and HI deficiency of the member galaxies will be studied. The signals have traveled hundreds of millions of years and contain information much earlier in time. The ultimate goal is to develop techniques of studying and understanding them so that these techniques can help us study clusters beyond the current redshift range in the future.
- My first task was to search for galaxy clusters with high redshifts between 14,000 km/s and 20,000 km/s within the NASA Extragalactic Database (NED). The currently published ALFALFA survey has covered three different regions in the sky under three catalogs, thus I have filtered out the searched results that are not in the ALFALFA coverage and obtained a list of potential candidates which could be sources of HI signals.
- A reasonable choice of the diameter of a galaxy cluster at this kind of high redshift is 40 arc minutes. Thus a further search of objects with coordinates centered in the previous list is performed within the ALFALFA catalog. Then I looked at the optical images of these objects and compared them with their spectrum. Since the Arecibo beam is about 3.2 arcmin in diameter, therefore any spiral or irregular galaxies in a circle about that size are my candidates that might contribute to the HI signal in the spectrum.
- Most of the 21 clusters have no ambiguity in which galaxy is the main contributor for the peak in the spectrum. However, three HI detections in three separate clusters contain multiple galaxy candidates for the main peak. These three will require special attention when trying to map the HI spectrum with the optical images.
- Next, I have started looking at the grids that have not yet been published and processing them. The first task is to run the grid baselining and grid flatfielding. The next step is 3-D extraction where I try to find galaxy signals from the grid.