SALT spectroscopic observations of galaxy clusters detected by ACT and a Type II quasar hosted by a brightest cluster galaxy

Brian Kirk, Matt Hilton, Catherine Cress, Steven M. Crawford, John P. Hughes, Nicholas Battaglia, J. Richard Bond, Claire Burke, Megan B. Gralla, Amir Hajian, Matthew Hasselfield, Adam D. Hincks, Leopoldo Infante, Arthur Kosowsky, Tobias A. Marriage, Felipe Menanteau, Kavilan Moodley, Michael D. Niemack, Jonathan L. Sievers, Cristóbal Sifón, Susan Wilson, Edward J. Wollack, Caroline Zunckel

Published 2014-10-29Version 1

We present Southern African Large Telescope (SALT) follow-up observations of seven massive clusters detected by the Atacama Cosmology Telescope (ACT) on the celestial equator using the Sunyaev-Zel'dovich (SZ) effect. We conducted multi-object spectroscopic observations with the Robert Stobie Spectrograph in order to measure galaxy redshifts in each cluster field, determine the cluster line-of-sight velocity dispersions, and infer the cluster dynamical masses. We find that the clusters, which span the redshift range 0.3 < z < 0.55, range in mass from (5 -- 20) x 10$^{14}$ solar masses (M200c). Their masses, given their SZ signals, are similar to those of southern hemisphere ACT clusters previously observed using Gemini and the VLT. We note that the brightest cluster galaxy in one of the systems studied, ACT-CL J0320.4+0032 at z = 0.38, hosts a Type II quasar. To our knowledge, this is only the third such system discovered, and therefore may be a rare example of a very massive halo in which quasar-mode feedback is actively taking place.