Significant progress is expected to come through improved analysis techniques, increases in the number of known high-redshift quasars from optical and infrared sky surveys, large gains in sensitivity from next-generation observing facilities, and synergies with other probes of the reionization era. Along with other probes of the high-redshift Universe, absorption line data are consistent with a relatively late end to reionization ($5.5 \lesssim z \lesssim 7$) however the constraints are still fairly weak. Finally, we review constraints from the Ly$\alpha$ forest and quasar near zones on the timing of reionization. A substantial fraction of metal absorbers at these redshifts may trace relatively low-mass galaxies. Current observations suggest a buildup of metals in the circumgalactic environments of galaxies over $z \sim 6$ to 5, although changes in ionization will also affect the evolution of metal line properties. ![]() We then discuss insights from metal absorption lines into reionization-era galaxies and their surroundings. Critically, these measurements reflect the escaping ionizing radiation from all galaxies, including those too faint to detect directly. The data was adopted from different databases, including SDSS data release five, USNO, FIRST, and ROSAT. We first describe how the Ly$\alpha$ forest is used to determine the intensity of the ionizing ultraviolet background and the global ionizing emissivity budget. 10 introduced a decision tree method called random forest for multiwavelength data classification. In this review we examine the multiple ways in which absorption lines trace the connection between galaxies and the IGM near the reionization epoch. If its redshift were interpreted conventionally, Mrk 205 would be located about 1.2 billion light-years, or 10 times farther. Towards this goal, quasar absorption lines play a unique role by probing the properties of diffuse gas on galactic and intergalactic scales. Mrk 205 is a very compact object which appears to lie within the spiral arms of NGC 4319, but it has a much higher redshift (z 0.07) and has been identified as a low-redshift quasar. It is sometimes known as a quasi-stellar object, abbreviated QSO.The emission from an AGN is powered by a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Better calibration of the tracers, higher resolution data and availability of facilities that can probe the stellar population will be crucial to assess precisely and accurately high-redshift quasar hosts.Determining when and how the first galaxies reionized the intergalactic medium (IGM) promises to shed light on both the nature of the first objects and the cosmic history of baryons. A quasar (/ k w e z r / KWAY-zar) is an extremely luminous active galactic nucleus (AGN). The discrepancy between local and high-redshift MBHs seems caused by the different tracers employed, and necessary assumptions, and not by an intrinsic difference. When using the gas-based tracers, however, MBHs appear to be over-massive. In our analysis of the single galaxy we evolve, we find that the high-redshift population sits on the same correlations as the local one, when using the same tracers used at $z=0$. The high-redshift studies argued that MBHs at high redshift deviate from the local MBH-galaxy correlations. We measure both the stellar-based quantities used to establish the $z=0$ correlations, as well as the gas-based quantities available in $z \gtrsim 6$ observations, adopting the same assumptions and techniques used in observational studies. ![]() We perform a very-high resolution cosmological zoom-in simulation of a $z=7$ quasar including state-of-the-art non-equilibrium chemistry, MBH formation, growth and feedback, to assess the evolution of the galaxy host and the central MBH, and compare the results with recent ALMA observations of high-redshift quasars. The relations at $z=0$, however, rely on stellar-based tracers of the galaxy properties. Current observations of $z \gtrsim 6$ hosts, at sub-mm wavelengths, trace the properties of cold gas, and these are used to compare with the correlations between MBHs and galaxies characterising the $z=0$ population. ![]() ![]() Download a PDF of the paper titled High-redshift quasars and their host galaxies I: kinematical and dynamical properties and their tracers, by Alessandro Lupi and 5 other authors Download PDF Abstract:Observations of high-redshift quasars provide information on the massive black holes (MBHs) powering them and the galaxies hosting them.
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