RX J2129.7+0005 BCG

RX J2129.7+0005 BCG (short for RX J2129.7+0005 Brightest Cluster Galaxy) also known as PGC 1156801, is a massive elliptical galaxy residing as the brightest cluster galaxy (BCG) of the RX J2129.7+0005 galaxy cluster. It is located in the constellation of Aquarius and a redshift of 0.23, meaning the galaxy is located 3.1 billion light-years from Earth.

Characteristics
RX J2129.7+0005 BCG is one of the largest galaxies with a diameter exceeding 500,000 light-years across. It is found optically luminous and is aligned with its cluster distribution, suggesting that the galaxy lies at the bottom of the cluster's gravitational potential. It has a central velocity dispersions between the range of α ~ 300–400 km s−1 and little rotational support. Like other elliptical galaxies, RX J2129.7+0005 BCG has a light profile described by the de Vaucouleurs surface brightness law, μ(r) α r1/4, over a large range in radius. It is known to have an extended envelope of excess light, according to the de Vaucouleurs law fitted within the inner regions. As for intracluster light in RX J2129.7+0005 BCG on the other hand, it is estimated to have a range from 27.5 mag arcsec-2 at 100 kpc to ~32 mag arcsec-2 at 700 kpc as observed by r-bands.

It is possible RX J2129.7+0005 BCG was formed from smaller spiral or elliptical galaxies. As they collided with each other, dynamical friction together with tidal forces redistribute ordered orbital kinetic energy into random energy forms, allowing these galaxies to merge into an amorphous, triaxial system resembling the appearance of an elliptical galaxy.

Apart from that, RX J2129+0005 BCG is classified an active galaxy with an X-ray bright nucleus and a low-excitation radio galaxy with a 1.4 GHz luminosity range between the values of 2 × 1023 and 3 × 1025 W Hz−1. Its radio power in RX J2129.7+0005 detected, is found in the range of 2 ×1023 to ~ 1026 W Hz−1 and radio spectral indices α 1.530 and also distributed from ~ -1 to -0.25 around the central value < α > =-0.68 with a resolved radio emission.