Reins et al. (2013) indentified 151 low mass galaxies with optical signs of AGN activity. Of these, 39 sources are unambigous AGN displaying either broad emission lines or have been identified as AGN in the BPT diagram. Of these 39 sources, 27 are observable with Arecibo in the Spring. For all potential targets, we estimate the 21-cm flux using 20% gas fractions, which generally places our targets below the detection threshold of the ALFALFA survey (see Figure X).
Therefore we have identified 27 primary targets for an estimated total of 28 hours required for high signal-to-noise observations. Our primary targets include all spring BPT AGN candidates and all broad-line BPT composites. We have also identified 19 secondary targets that include isolated BPT composites for an additional 18 hours of observing time, in case the gas fractions for the primary targets are underestimated. We request a total of 28 hours with the Arecibo telescope to observe 27 primary low mass AGN candidates. Given our prior experience, we are confident that we will obtain high quality, high signal-to-noise spectra for our proposed observations.
We will observe our target dwarf galaxy AGN candidates in the L-band wide receiver, with the spectrometer in 9 level sampling mode with 4096 channels and a 12.5 MHz bandwidth. This yields a velocity resolution of 0.66 km/s which we will center on the redshifted 21-cm line using the SDSS optically measured recession velocity. All of our target galaxies have recession velocities less than 5000 km s−1 and are unresolved by the Arecibo beam. We chose the L-band over the ALFA receiver as it has a higher sensitivity and minimizes side-lobe contamination. To mitigate any baselines issues, we will perform an associated off observation (position switching) of equal integration time for each target.
We request primarily night-time observing only in order to avoid standing waves due to solar interference which make estimating accurate baselines difficult. Using recently obtained HI data for low mass isolated galaxies, we have calibrated the relation of HI gas mass to stellar mass. Using this relation with the distances determined from SDSS redshifts, we have determined estimated integration times for all of our targets.
We have recently completed a fully automated set of reduction and measurement scripts for 21-cm emission spectra obtained at Arecibo. We will therefore reduce our new observations and measure the HI parameters of the emission lines within days of completing our observations. This expedited and automated pipleline will enable us to quickly meet our science objectives and publish our analysis and results.