Galaxy formation and evolution

Abstract:

There is a wide-ranging debate about the merits and demerits of searching for, and sending messages to, extraterrestrial intelligences (SETI and METI). There is however reasonable (but not universal) consensus that replying to a message from an extraterrestrial intelligence should not be done unilaterally, without consultation with wider society and the rest of the world. But how should this consultation actually work? In this paper we discuss various ways that decision making in such a scenario could be done democratically, and gain legitimacy. In particular we consider a scientist-led response, a politician-led response, deciding a response using a referendum, and finally using citizens’ assemblies. We present the results of a survey of a representative survey of 2000 people in the UK on how they thought a response should best be determined, and finally discuss parallels to how the public is responding to scientific expertise in the COVID-19 Pandemic.

Abstract:

We report the discovery of two new giant radio galaxies (GRGs) using the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey. Both GRGs were found within a ∼1 deg2 region inside the COSMOS field. They have redshifts of z = 0.1656 and z = 0.3363 and physical sizes of 2.4 and 2.0 Mpc, respectively. Only the cores of these GRGs were clearly visible in previous high-resolution Very Large Array observations, since the diffuse emission of the lobes was resolved out. However, the excellent sensitivity and uv coverage of the new MeerKAT telescope allowed this diffuse emission to be detected. The GRGs occupy an unpopulated region of radio power – size parameter space. Based on a recent estimate of the GRG number density, the probability of finding two or more GRGs with such large sizes at z < 0.4 in a ∼1 deg2 field is only 2.7 × 10−6, assuming Poisson statistics. This supports the hypothesis that the prevalence of GRGs has been significantly underestimated in the past due to limited sensitivity to low surface brightness emission. The two GRGs presented here may be the first of a new population to be revealed through surveys like MIGHTEE that provide exquisite sensitivity to diffuse, extended emission.