Remove quasar J0439 + 1634 explored in X-rays

Remove quasar J0439 + 1634 explored in X-rays

XMM-Newton EPIC image of J0439 + 1634, combined from the pn, MOS1 and MOS2 images, in 0.2-0.5 keV (left), 0.5-2 keV (center) and 2-10 keV (right) X-ray bands. Credit: Yang et al., 2021.

Using ESA’s XMM-Newton spacecraft, an international team of astronomers has performed X-ray observations of the most distant known gravitational-lined quasar – J0439 + 1634. The results of the study, published on December 20 on arXiv pre-print server, shed more light on the characteristics of this source.

Quasars or quasi-star objects (QSOs) are extremely luminous active galactic nuclei (AGNs) that contain supermassive central black holes with growth disks. Their redshifts are measured from the strong spectral lines that dominate their visible and ultraviolet spectra.

Astronomers are particularly interested in studying high-redshift quasars (at redshifts higher than 5.0), as they are the brightest and most distant compact objects in the observable universe. Spectra of such QSOs can be used to estimate the mass of supermassive black holes that limit the evolution and formation models of quasars. Therefore, high-redshift quasars could serve as a powerful tool for exploring the early universe.

At a redshift of 6.52, J0439 + 1634 was the first known gravitational lensed high-redshift quasar. Its high lens magnification makes it an excellent target for the study of X-rays from a QSO from the reionization era, which in itself is less luminous.

J0439 + 1634 is also the so-called broad absorption line (BAL) quasar. BAL quasars are generally assumed to be highly absorbed in the soft X-ray band and are generally X-ray weak in observations of low-redshift quasars. To date, however, no such studies have been performed on BAL QSOs with high redshift due to their weak X-rays.

So a team of researchers led by Jinyi Yang from the University of Arizona decided to explore J0439 + 1634 with the European Photon Imaging Camera (EPIC) system aboard the XMM-Newton. They examined the X-ray properties of this source through spectral analysis and compared the results with other quasar populations.

J0439 + 1634 was identified as an X-ray source with XMM-Newton in the 0.5-10 keV band of all three EPIC cameras, while it was not detected in the 0.2-0.5 keV band. The EPIC spectra show that the quasar has a flat photon index – at a level of about 1.45.

The observations found that the optical-to-X-ray spectral slope of J0439 + 1634 is about -2.07, suggesting that this quasar is illuminating by a factor of 18 in X-rays, which is consistent with the behavior of BAL QSOs observed at lower redshift. The astronomers noted that their study marks the first time that an X-ray-weak BAL quasar at a redshift of over 6.0 has been observed spectroscopically.

Furthermore, spectral alignment using an absorbed power law model suggests a high inherent column density in the case of J0439 + 1634 – more than 200 trillion cm-2. According to the researchers, this finding suggests that J0439 + 1634 is the first highly blurred quasar with X-ray spectroscopy in the reionization era. They assume that this source could be an inherent X-ray-weak quasar.

Astronomers discover the most X-ray bright red-shifting quasar

More information:
Deep XMM-Newton observations of an X-ray weak, broad absorption line quasar at z = 6.5, arXiv: 2112.10785 [astro-ph.GA]

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