RX J0911.4+0551 is a gravitationally-lensed quasar located in the constellation of Hydra. It has a high redshift of (z) 2.800 and was first discovered by astronomers who were conducting the ROSAT All-Sky Survey in 1997. This is a radio-quiet object with an X-ray luminosity of 4.1046 ergs.[1]
RX J0911.4+0551 is a quadruped imaged quasar with a wide angular separation of 3.1 arcseconds.[2] When imaged by high resolution imaging by both Nordic Optical Telescope and New Technology Telescope, it is found to be split into four images and lensed by a foreground galaxy located at a redshift of (z) 0.769.[2][3] The lens galaxy is described as elongated based on I-band imaging; apparently looking like as an edge-on spiral with a bright nucleus and elongated diffused disk, according to near-infrared imaging.[4] This lensed galaxy is known to be located in a galaxy cluster which in turn displays an extreme shear distortion for this lensing effect.[5][3]
The optical light curves of the components of RX J0911.4+0551 showed it has time delays. Based on results, the time delay is found significantly short with a period of 146 ± 8 days between the two observed components identified as A and B. The component (B) is found to be the leading component.[5] Raw and deconvolved imaging by Chandra X-ray Observatory also showed it as extended along east to west direction. An emission profile made up of a bright component was also found located southwest of B, being stretched towards the quasar's direction.[6]
The host galaxy of RX J0911.4+0551 is described to be young galaxy in stages of evolving without indications of a major merger.[7] It has a star formation rate of 140 Mʘ yr-1 and found to produce a molecular outflows reaching a rate of 180 Mʘ yr-1 indicating the large fraction of gas would be depleted within a lifetime of 100 million years.[8] Observations by the Plateau de Bure Interferometer also showed the host's low gas mass is 2.3 ± 0.5 x 109 Mʘ and it has a total far-infrared luminosity rate measuring as 7.2 ± 1011 Lʘ.[9] The host also has a carbon monoxide (CO) (5-4) line profile displaying a compact structure based on observations by Atacama Large Millimetre Array, with a full width at half maximum measuring 133 ± 3 kilometers per seconds.[10]
Several absorption line systems located at redshifts of (z) 2.790, 2.42 and 2.63 have been identified in the quasar's A and B spectra. Since these absorption lines display a velocity dispersion of around 1,000 kilometers per seconds, the quasar has a mini broad absorption line.[11] A rapid flare has been detected by Chandra with a duration of 2,000 seconds in November 2000.[12][13]