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Register a new userExploratory Chandra observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30
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We report exploratory chandra observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30. The quasar is clearly detected by chandra with a possible component of extended emission. The rest-frame 2-10 keV luminosity is 9.0$^{+9.1}_{-4.5}$ $times$ 10$^{45}$ erg s$^{-1}$ with inferred photon index of $Gamma$ = 3.03$^{+0.78}_{-0.70}$. This quasar is X-ray bright, with inferred X-ray-to-optical flux ratio aox $=-1.22^{+0.07}_{-0.05}$, higher than the values found in other quasars of comparable ultraviolet luminosity. The properties inferred from this exploratory observation indicate that this ultraluminous quasar might be growing with super-Eddington accretion and probably viewed with small inclination angle. Deep X-ray observation will help to probe the plausible extended emission and better constraint the spectral features for this ultraluminous quasar.
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A brief Chandra observation of the ultraluminous quasar, SDSS J010013.02+280225.8 at redshift 6.326, showed it to be a relatively bright, soft X-ray source with a count rate of about 1 ct/ks. In this paper we present results for the quasar from a 65ks XMM-Newton observation, which well constrains its spectral shape. The quasar is clearly detected with a total of $sim$ 460 net counts in the 0.2-10 keV band. The spectrum is characterised by a simple power-law model with photon index of $Gamma = 2.30^{+0.10}_{-0.10}$, and the intrinsic 2-10 keV luminosity is $3.14times10^{45}$ erg $text{s}^{-1}$. The 1 $sigma$ upper limit to any intrinsic absorption column density is $N_{H} = 6.07times 10^{22} {text{cm}}^{-2}$. No significant iron emission lines were detected. We derive the X-ray-to-optical flux ratio $alpha_{text{ox}}$ of $-1.74pm$0.01, consistent with the values found in other quasars of comparable ultraviolet luminosity. We did not detect significant flux variations either in the XMM-Newton exposure or between XMM-Newton and XMM-Newton observations, which are separated by $sim$ 8 months. The X-ray observation enables the bolometric luminosity to be calculated after modelling the spectral energy distribution: the accretion rate is found to be sub-Eddington.
We present the analysis of nine radio sources belonging to the Third Cambridge Revised catalog (3CR) observed with $Chandra$ during Cycle 20 in the redshift range between 1.5 and 2.5. This study completes the 3CR $Chandra$ Snapshot Survey thus guaranteeing the X-ray coverage of all 3CR sources identified to date. This sample lists two compact steep spectrum sources, four radio galaxies and three quasars. We detected X-ray emission from all nuclei, with the only exception of 3C 326.1 and 3C 454.1 and from radio lobes in 6 out of 9 sources at level of confidence larger than $sim$5$sigma$. We measured X-ray fluxes and luminosities for all nuclei and lobes in the soft (0.5 - 1 keV), medium (1 - 2 keV) and hard (2 - 7 keV) X-ray bands. Since the discovered X-ray extended emission is spatially coincident with the radio structure in all cases, its origin could be due to Inverse Compton scattering of the Cosmic Microwave Background (IC/CMB) occurring in radio lobes.
To date, PMN J2134-0419 (at a redshift z=4.33) is the second most distant quasar known with a milliarcsecond-scale morphology permitting direct estimates of the jet proper motion. Based on two-epoch observations, we constrained its radio jet proper motion using the very long baseline interferometry (VLBI) technique. The observations were conducted with the European VLBI Network (EVN) at 5 GHz on 1999 November 26 and 2015 October 6. We imaged the central 10-pc scale radio jet emission and modeled its brightness distribution. By identifying a jet component at both epochs separated by 15.86 yr, a proper motion of mu=0.035 +- 0.023 mas/yr is found. It corresponds to an apparent superluminal speed of beta_a=4.1 +- 2.7 c . Relativistic beaming at both epochs suggests that the jet viewing angle with respect to the line of sight is smaller than 20 deg, with a minimum bulk Lorentz factor Gamma=4.3. The small value of the proper motion is in good agreement with the expectations from the cosmological interpretation of the redshift and the current cosmological model. Additionally we analyzed archival Very Large Array observations of J2143-0419 and found indication of a bent jet extending to ~30 kpc.
X-ray emission from quasars has been detected up to redshift $z=7.5$, although only limited to a few objects at $z>6.5$. In this work, we present new Chandra observations of five $z>6.5$ quasars. By combining with archival Chandra observations of six additional $z>6.5$ quasars, we perform a systematic analysis on the X-ray properties of these earliest accreting supermassive black holes (SMBHs). We measure the black hole masses, bolometric luminosities ($L_{rm bol}$), Eddington ratios ($lambda_{rm Edd}$), emission line properties, and infrared luminosities ($L_{rm IR}$) of these quasars using infrared and sub-millimeter observations. Correlation analysis indicates that the X-ray bolometric correction (the factor that converts from X-ray luminosity to bolometric luminosity) decreases with increasing $L_{rm bol}$, and that the UV/optical-to-X-ray ratio, $alpha_{rm ox}$, strongly correlates with $L_{rm 2500}$, and moderately correlates with $lambda_{rm Edd}$ and blueshift of CIV emission lines. These correlations are consistent with those found in lower-$z$ quasars, indicating quasar accretion physics does not evolve with redshift. We also find that $L_{rm IR}$ does not correlate with $L_{rm 2-10 keV}$ in these luminous distant quasars, suggesting that the ratio of the SMBH growth rate and their host galaxy growth rate in these early luminous quasars are different from those of local galaxies. A joint spectral analysis of the X-ray detected $z>6.5$ quasars yields an average X-ray photon index of $ Gamma=2.32^{+0.31}_{-0.30}$, steeper than that of low-$z$ quasars. By comparing it with the $Gamma-lambda_{rm Edd}$ relation, we conclude that the steepening of $Gamma$ for quasars at $z>6.5$ is mainly driven by their higher Eddington ratios.
Large-scale surveys over the last years have revealed about 300 QSOs at redshift above 6. Follow-up observations identified surprising properties, such as the very high black hole (BH) masses, spatial correlations with surrounding cold gas of the host galaxy, or high CIV-MgII velocity shifts. In particular, the discovery of luminous high-redshift quasars suggests that at least some black holes likely have large masses at birth and grow efficiently. We aim at quantifying quasar pairs at high redshift for a large sample of objects. This provides a new key constraint on a combination of parameters related to the origin and assembly for the most massive black holes: BH formation efficiency and clustering, growth efficiency and relative contribution of BH mergers. We observed 116 spectroscopically confirmed QSOs around redshift 6 with the simultaneous 7-channel imager GROND in order to search for companions. Applying identical colour-colour cuts as for those which led to the spectroscopically confirmed QSO, we perform LePHARE fits to the 26 best QSO pair candidates, and obtained spectroscopic observations for 11 of those. e do not find any QSO pair with a companion brighter than M1450(AB) < -26 mag within our 0.1-3.3 h^-1 cMpc search radius, in contrast to the serendipitous findings in the redshift range 4--5. However, a low fraction of such pairs at this luminosity and redshift is consistent with indications from present-day cosmological-scale galaxy evolution models. In turn, the incidence of L- and T-type brown dwarfs which occupy a similar colour space as z ~ 6 QSOs, is higher than expected, by a factor of 5 and 20, respectively.
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