OBSERVING THE INVISIBLE: A COLLABORATIVE INVESTIGATION OF ASTROPHYSICISTS & PHILOSOPHERS

Background: This NSF-funded philosophy/astrophysics research project focuses on the search for dark matter galaxies: the simulations, observations, and database-combing required to find them, and the philosophical issues raised and illuminated by the search. Pure dark matter galaxies do not produce or interact within electromagnetic radiation. However, our research attempts to characterize the signatures of the gravitational interactions between dark and luminous galaxies. Methods: Through philosophical analysis we draw attention to how models and computer simulations play an important role in bridging the gap between observation and theory in contemporary scientific practice. Results: In this poster, we present the finding from three phases of this project with respect to both astrophysical and philosophical research. Phase 1 involved building computer simulations of dark matter galaxy/luminous matter galaxy interactions to determine their morphology and kinematics. This provides the opportunity to study the precise ways that theory enters into the construction of simulations, and how much theory determines values for simulation parameters. Philosophical analysis includes identifying what warrants importing these data into the luminous / dark galaxy interactions, what considerations go into concluding simulations are precise and accurate, given that no one has ever knowingly observed the target event, and finally how the simulations used to characterize morphology and confirm dynamics. Phase 2 involved a synergistic human-based and computer-based examination of the Sloan Digital Sky Survey for the dark matter galaxy signatures identified in Phase 1. This allows the team to investigate the relationship between human and computer-based judgments. We discussion how astrophysicists manage the trade-off between computational searching and human-based searching. Phase 3 involved conducting new, direct imaging and spectrophotometric/kinematic observations of the dark matter galaxy candidates. The philosophical side of this phase concerns empirical justifications and epistemic warrant in astrophysics, especially as the issue of entities such as dark matter. Conclusion: We argue the blend of imaging, spectroscopy, simulation, and theorizing combined to warrant inferences about objects hundreds of megaparsecs away that are intrinsically invisible at all known frequencies.