# 2MASX J09175344+5143379

2MASX J09175344+5143379 also known as PGC 2399018, is a massive elliptical galaxy located in the constellation of Ursa Major. At the redshift of 0.216, the galaxy is located 2.9 billion light-years from Earth and considered the brightest cluster galaxy (BCG) in the galaxy cluster, Abell 773.

## Characteristics

2MASX J09175344+5143379 is classified a luminous galaxy with an r-band luminosity of L r > 8L*. The galaxy is considered radio-loud, located in a specific location of the cluster environment with an X-ray luminosity of LX ≥ 5 × 10$^{44}$ erg s$^{−1}$. 2MASX J09175344+5143379 also has central velocity dispersion between the range of α ~ 300–400 km s$^{−1}$ or D$_n$4000 > 1.5 and within R$_{200}$ according to calculations from velocity dispersion functions.
It is also a line-emitting galaxy with [O III] 5007 Å line emission and contains a powerful radio source showing the presence of a strong core component. This might be caused by X-ray cavity power correlating with the extended and core radio emission, suggesting of steady fueling of the nucleus over bubble-rise that is observed in time scales.
Like other elliptical galaxies of similar sizes, the light profile in 2MASX J09175344+5143379 is described by a de Vaucouleurs surface brightness law, μ(r) ɐ r$^{1/4}$, over a large range in radius. As a giant elliptical galaxy, it has extended stellar envelope of excess light over it, probably associated by the formation of the cluster.
The galaxy is known to show recent signs of star formation in its region, suggesting it a starburst galaxy. It has a low central gas entropy displaying enhanced ultraviolet rays (38%) and mid-infrared emission (43%) from 8 to 160 μm, according to observations by Galaxy Evolution Explorer (GALEX), Spitzer Space Telescope, and Two Micron All Sky Survey (2MASS) assembling spectral energy distributions (SEDs) and colors for BCGs like 2MASX J09175344+5143379. Such of these high excesses is consistent with the star formation activity inside the BCG, appearing to be enabled by presence of high density, X-ray emitting intergalactic gas in the cluster core. This hot gas may provide the clues of enhanced ambient pressure and fuel to trigger star formation. According to Spitzer Space Telescope observations, it is classified a luminous infrared galaxy with luminosity values of L$_{IR}$>10$^{11}$ L$_{solar}$.
Due to its colossal appearance, it is possible 2MASX J09175344+5143379 might have been formed from multiple galaxy mergers. As numerous galaxies of shapes and sizes collided together, the process of dynamical friction along with tidal forces redistribute the kinetic energy into random energy form, allowing these galaxies to combine into a single amorphous, triaxial system resembling 2MASX J09175344+5143379. The stellar mass of the galaxy is also built as well, making it having a large galactic halo.
The star formation rate of 2MASX J09175344+5143379 is estimated to be 1-150 M⊙ yr$^{−1}$ according to infrared observations done by Spitzer and Herschel photometry. Researchers who found a correlation with cluster X-ray gas cooling time for cool-core clusters (gas cooling time <1 Gyr), suggested the star formation in 2MASX J09175344+5143379 is influenced by the cluster-scale cooling process with occurrence of the molecular gas tracing Hα emission, correlating together with its obscured star formation.

## Abell 773

The cluster where 2MASX J09175344+5143379 is residing, is found to be a rich X-ray and luminous galaxy cluster at z = 0.22. Observed through Ryle Telescope at 15 GHz, the cluster has a Sunyaev-Zel'dovich effect due to measurements of decrements in the cosmic microwave background radiation with values of -590 ± 116μ Jy beam$^{−1}$. This indicates the temperature decrement is in the range of –790 to –990 μK.
According to observations from researchers, the velocity distribution of cluster galaxies shows two peaks at v 65000 and 67500 km s$^{−1}$, which corresponds to velocities of the two dominant galaxies in Abell 773. The low velocity structure has a high velocity dispersion - σv = 800–1100 km s$^{−1}$ intermediate velocity dispersion - σv~ 500 km s$^{−1}$ in the high velocity structure. These components are suggested to be two independent groups. Researchers estimate a cluster mass of about 1h^-1_70 of 6-11h^-1_70 M_⊙ and a mass accretion rate of M200 = 10$^{15}$ h$^{−1}$ M⊙ according to computer stimulations.
Abell 773 has a gas entropy profile. Researchers studied intracluster medium entropy profiles in a sample of 47 galaxy clusters and groups, which was observed at ~r$_{500}$ with Chandra, XMM-Newton, and Suzaku. They found the gas entropy profiles are derived with Bayesian statistics showing the gas entropy profiles are consistent with simulation-predicted power-law profile. Apart from that, they also calculated the total feedback energy per particle and found it decreases from ~10 keV at the center to zero at ~0.35r$_{200}$. These values are consistent with zero outside ~0.35r$_{200}$, implying there is an upper limit of the feedback efficiency of ~0.02 for the supermassive black holes hosted in 2MASX J09175344+5143379.
The radial variation of the intrinsic scatter in scaled density profile in Abell 773, is found to be a minimum of ~20% at R ~ [0.5−0.7] R$_{500}$ and a value of ~40% at R$_{500}$ according to researchers. They also found a radio halo in Abell 773 through using dynamical information from the X-ray data and studying distribution of galaxy clusters in the radio power-mass diagram. Through the results, they found the radio power correlates with the mass of its host cluster. Nevertheless, Abell 773 is a disturbed cluster exhibiting an apparent bimodality, with the emissivity of radio halo being ~5 times larger compared to non-emission radio halos in relaxed clusters. Researchers found the fraction of radio halos drops from ~70% in high-mass clusters to ~35% in the lower mass systems in the sample and showed that this result is in good agreement with the expectations from turbulent re-acceleration models.

## Lensed galaxy in Abell 773

A galaxy has been found to be lensed during the Herschel Lensing Survey (HLS) of Abell 773. With a bright source and located at redshift 5.2429, it is found unusual as compared to other lensed sources discovered so far, because of its higher submm flux (~200 mJy at 500 μm) and the high redshift. Apart from that, the source has a far-infrared (FIR) luminosity of L$_{FIR}$ = 1.1 × 10$^{14}$/μ L$_⊙$, where μ is the magnification factor, of ~11, indicating the source originates from an ultraluminous infrared galaxy with a H$_2$  mass is 5.8 × 10$^{11}$/μ M$_⊙$.