Analyzing Neutral Hydrogen Absorption Profiles in the Host Galaxies of 25 Active Galactic Nuclei.

The purpose of this research consists in searching for neutral hydrogen (HI) absorption in the host galaxy of a sample of 25 active galactic nuclei (AGN). We looked at these radio sources because the AGN are often characterized by the presence of a jet which is able to interact with gas throughout the host galaxy. Because of that we can study the kinematics of the gas to understand the effect of the jet and the relation that exists between the host galaxy and the AGN (Brinks and Mundell 96). The distribution of the HI can also give us information about the shape of the galaxy. Based on the line width and center we can obtain properties of the HI gas, such as its main velocity, if it's moving towards us (blueshift) or moving away from us (redshift). To achieve our goal, we take advantage of the sensitivity of the Arecibo's 305m telescope, because here we can observe in minutes what it could take hours in another radio telescope, to detect these absorption lines. Once we observed the galaxies, we had to convert the data into useful information to get the spectral graphs. Each galaxy has a file with the different scans and we wrote a script using the wdpss6 program on each scan to analyze the data. In order to reduce data, we added the individual scans into one scan, and then we averaged the polarization. Once it was polarization-averaged, we smooth the data and then we plotted the results and analyzed the graphs. We detect HI absorption in 6 objects and rotation for the galaxies NGC 2619 (G2) and 2MASX J12172779+1554132 (E1). For those 6 objects that appear to have a detection we made a baseline correction for this data, so it could fix any systematic oscillation that remained in the spectrum graph and do not confuse them with the real and important data. For NGC 2619 we can say that have a double-winged profile because that type of profile is a signature of rotation (Jones 18). So far, the other 19 objects have no detected HI absorption.