IC 4516

IC 4516 is a type E elliptical galaxy located in Boötes. Its redshift is 0.045618 which corresponds IC 4516 to be located 667 million light-years from Earth. The galaxy was discovered by Lewis Swift on June 2, 1898, which was his last discovery after spending half a century observing astronomical objects, starting with the observation of the Great Comet in 1843.

Features
IC 4516 is classified a radio galaxy, specially a Fanaroff-Riley type 2 (FR II). It has an active nucleus and is the brightest member in the galaxy cluster, WHL J145423.5+162119.

IC 4516 contains a strong radio source in its center called 3C 306. The radio source is identified to be stronger than 25 mJy on the Green Bank 4.85 GHz sky maps. Based on its infrared-radio flux ratio as well as infrared spectral indices and radio morphologies, it is classified to be a "starburst" or "monster". Further results show that the rms scatter in logarithmic infrared-radio q is not more compared to σq = 0.16 for starburst galaxies which is selected at 4.85 GHz.

Moreover, IC 4516 is one of the γ-ray-emitting radio galaxies detected by the Fermi Gamma-ray Space Telescope (Fermi), indicating it contributes to EGB (diffuse unresolved extragalactic γ-ray background) which is written by Mauro et al. and Hooper et al. This is suggested that IC 4516 is an AGN with a "mis-aligned" jet in with the direction of ~>20° towards Earth. Its possible IC 4516 is a low-luminosity core-dominated radio galaxy that is expected to have a proportionally lower γ-ray luminosity to the point it can't be detected individually by Fermi, based on the relation of core radio and its luminosity.

A further study conducted in 2020 in search of Centaurus A-like features, finds there is statistical evidence of flux variability on 6-month time scales for seven of the 26 radio galaxies, among them is IC 4516, in which is calculated over the full energy range of 100 MeV ≤ E ≤ 300 GeV. A variability index study was conducted via the method used by Nolan et al. 2012 which shows if the null hypothesis is correct, the variability index is correct, then it is distributed as χ2 with 19 degrees of freedom. This suggests evidence for variability index to be at the ≥3σ level.

From the variability indices that is distributed as X2 functions with Ndof degrees of freedom, which one of the variability indices is greater than the 99% confidence limit of 18.48 and 72.44 for the (Ndof = 7) and 2 month (Ndof = 47) light curves, IC 4516 is found to be variable thus suggesting blazar-like behavior.