Recent Event Horizon Telescope observations of M87* and Sgr A* strongly
suggests the presence of supermassive black hole at their respective cores. In
this work, we use the semi-analytic Radiatively Inefficient Accretion Flows
(RIAF) model to investigate the resulting images of Joshi-Malafarina-Narayan
(JMN-1) naked singularity and the Schwarzschild BH. We aim at choosing the
JMN-1 naked singularity model and compare the synchrotron images with the
Schwarzschild solution to search any distinct features which can distinguish
the two objects and find alternative to the black hole solution. We perform
general relativistic ray-tracing and radiative transfer simulations using
Brahma code to generate synchrotron emission images utilising thermal
distribution function for emissivity and absorptivity. We investigate effects
in the images by varying inclination angle, disk width and frequency. The
shadow images simulated by the JMN-1 model closely resemble those generated by
the Schwarzschild black hole. When we compare these images, we find that the
disparities between them are minimal. We conduct simulations using various
plasma parameters, but the resulting images remain largely consistent for both
scenarios. This similarity is evident in the horizontal cross-sectional
brightness profiles of the two instances. Notably, the JMN-1 model exhibits
slightly higher intensity in comparison to the Schwarzschild black hole. We
conclude that JMN-1 presents itself as a viable substitute for the black hole
scenario. This conclusion is not solely grounded in the fact that they are
indistinguishable from their respective shadow observations, but also in the
consideration that JMN-1 emerges as an end state of a continual gravitational
collapse. This paradigm not only allows for constraints on spacetime but also
provides a good probe for the nature of the central compact object.Comment: Accepted in A&A, 7 pages, 6 figures. arXiv admin note: text overlap
with arXiv:2202.0058
