We report the discovery of a luminous quasar, J1007+2115 at z = 7.515 ("Pōniuā'ena"), from our wide-field reionization-era quasar survey. J1007+2115 is the second quasar now known at z > 7.5, deep into the reionization epoch. The quasar is powered by a (1.5 ± 0.2) × 10 9 M supermassive black hole (SMBH), based on its broad Mg II emission-line profile from Gemini and Keck near-IR spectroscopy. The SMBH in J1007+2115 is twice as massive as that in quasar J1342+0928 at z = 7.54, the current quasar redshift record holder. The existence of such a massive SMBH just 700 million years after the Big Bang significantly challenges models of the earliest SMBH growth. Model assumptions of Eddington-limited accretion and a radiative efficiency of 0.1 require a seed black hole of 10 4 M at z = 30. This requirement suggests either a massive black hole seed as a result of direct collapse or earlier periods of rapid black hole growth with hyper-Eddington accretion and/or a low radiative efficiency. We measure the damping wing signature imprinted by neutral hydrogen absorption in the intergalactic medium (IGM) on J1007+2115's Lyα line profile, and find that it is weaker than that of J1342+0928 and two other z 7 quasars. We estimate an IGM volume-averaged neutral fraction x HI = 0.39 +0.22 −0.13 . This range of values suggests a patchy reionization history toward different IGM sightlines. We detect the 158 µm [C II] emission line in J1007+2115 with ALMA; this line centroid yields a systemic redshift of z = 7.5149 ± 0.0004 and indicates a star formation rate of ∼ 210 M yr −1 in its host galaxy.

Distant quasars are unique tracers to study the formation of the earliest supermassive black holes (SMBHs) and the history of cosmic reionization. Despite extensive efforts, only two quasars have been found at z ≥ 7.5, due to a combination of their low spatial density and the high contamination rate in quasar selection. We report the discovery of a luminous quasar at z = 7.642, J0313−1806, the most distant quasar yet known. This quasar has a bolometric luminosity of 3.6 × 1013 L ⊙. Deep spectroscopic observations reveal a SMBH with a mass of (1.6 ± 0.4) × 109 M ⊙ in this quasar. The existence of such a massive SMBH just ∼670 million years after the big bang challenges significantly theoretical models of SMBH growth. In addition, the quasar spectrum exhibits strong broad absorption line (BAL) features in C iv and Si iv, with a maximum velocity close to 20% of the speed of light. The relativistic BAL features, combined with a strongly blueshifted C iv emission line, indicate that there is a strong active galactic nucleus (AGN)-driven outflow in this system. Atacama Large Millimeter/submillimeter Array observations detect the dust continuum and [C ii] emission from the quasar host galaxy, yielding an accurate redshift of 7.6423 ± 0.0013 and suggesting that the quasar is hosted by an intensely star-forming galaxy, with a star formation rate of ∼200 M ⊙ yr−1 and a dust mass of ∼7 × 107 M ⊙. Follow-up observations of this reionization-era BAL quasar will provide a powerful probe of the effects of AGN feedback on the growth of the earliest massive galaxies.

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This is the third paper in a series aimed at finding reionization-era quasars with the combination of DESI Legacy imaging Surveys (DELS), the Pan-STARRS1 (PS1) Survey, and near-infrared imaging surveys, such as the UKIRT Hemisphere Survey (UHS), as well as the Wide-field Infrared Survey Explorer (WISE) mid-infrared survey. In this paper, we describe the updated quasar candidate selection procedure, report the discovery of 16 quasars at 6.4 z6.9 from an area of ∼13,020 deg 2 , and present the quasar luminosity function (QLF) at z∼6.7. The measured QLF follows F µ-L L 1450 1450 2.35 () in the magnitude range −27.6<M 1450 <−25.5. We determine the quasar comoving spatial density at á ñ z =6.7 and M 1450 <−26.0 to be 0.39±0.11 Gpc −3 and find the exponential density evolution parameter to be k=−0.78±0.18 from z∼6 to z∼6.7, corresponding to a rapid decline by a factor of ∼6 per unit redshift toward earlier epochs. This indicates that the rapid decline of quasar spatial density at z>5 that was found by previous works continues to z>6, at a rate significantly faster than the average decline rate between z∼3 and 5. We measured quasar comoving emissivity at z∼6.7, which indicates that high-redshift quasars are highly unlikely to make a significant contribution to hydrogen reionization. The broad absorption line quasar fraction at z6.5 is measured to be 22%. In addition, we also report the discovery of six additional quasars at z∼6 in the Appendix.

We present the analysis of the XMM-Newton data of the Circum-Galactic Medium of MASsive Spirals (CGM-MASS) sample of six extremely massive spiral galaxies in the local Universe. All the CGM-MASS galaxies have diffuse X-ray emission from hot gas detected above the background extending ∼ (30 − 100) kpc from the galactic center. This doubles the existing detection of such extended hot CGM around massive spiral galaxies. The radial soft X-ray intensity profile of hot gas can be fitted with a β-function with the slope typically in the range of β = 0.35 − 0.55. This range, as well as those β values measured for other massive spiral galaxies, including the Milky Way (MW), are in general consistent with X-ray luminous elliptical galaxies of similar hot gas luminosity and temperature, and with those predicted from a hydrostatic isothermal gaseous halo. Hot gas in such massive spiral galaxy tends to have temperature comparable to its virial value, indicating the importance of gravitational heating. This is in contrast to lower mass galaxies where hot gas temperature tends to be systematically higher than the virial one. The ratio of the radiative cooling to free fall timescales of hot gas is much larger than the critical value of ∼ 10 throughout the entire halos of all the CGM-MASS galaxies, indicating the inefficiency of gas cooling and precipitation in the CGM. The hot CGM in these massive spiral galaxies is thus most likely in a hydrostatic state, with the feedback material mixed with the CGM, instead of escaping out of the halo or falling back to the disk. We also homogenize and compare the halo X-ray luminosity measured for the CGM-MASS galaxies and other galaxy samples and discuss the "missing" galactic feedback detected in these massive spiral galaxies. Spatial analysis of the diffuse X-ray emissionWe present additional information on the XMM-Newton data reduction and the results on the prominent extended or point-like sources in Appendix A. We present the major results on the diffuse hot gas emission in the following sections. In Fig. 1, we present the point source removed, soft proton and quiescent particle background

We study the edge‐on galaxy NGC 5775, utilizing a 58.2 ks Chandra ACIS‐S observation together with complementary Hubble Space Telescope (HST) ACS, Spitzer IRAC and other multi‐wavelength data sets. This edge‐on galaxy, with its disc‐wide active star formation, is particularly well suited for studying the disc/halo interaction on subgalactic scales. We detect 27 discrete X‐ray sources within the D25 region of the galaxy, including an ultra‐luminous source with a 0.3–7 keV luminosity of ∼7 × 1040 erg s−1. The source‐removed diffuse X‐ray emission shows several prominent extraplanar features, including a ∼10 kpc diameter ‘shell‐like’ feature and a ‘blob’ reaching a projected distance of ∼25 kpc from the galactic disc. The bulk of the X‐ray emission in the halo has a scale height of ∼1.5 kpc and can be characterized by a two‐temperature optically thin thermal plasma with temperatures of ∼0.2 and 0.6 keV and a total 0.3–2 keV luminosity of ∼3.5 × 1039 erg s−1. The high‐resolution, multi‐wavelength data reveal the presence of several extraplanar features around the disc, which appear to be associated with the in‐disc star formation. We suggest that hot gas produced with different levels of mass loading can have different temperatures, which may explain the characteristic temperatures of hot gas in the halo. We have obtained a subgalactic scale X‐ray‐intensity–star‐formation relation, which is consistent with the integrated version in other star‐forming galaxies.

We present a systematical analysis of the Chandra observations of 53 nearby highly-inclined (i 60 • ) disk galaxies to study the coronae around them. This sample covers a broad range of galaxy properties: e.g., about three orders of magnitude in the SFR and more than two orders of magnitude in the stellar mass. The Chandra observations of the diffuse soft X-ray emission from 20 of these galaxies are presented for the first time. The data are reduced in a uniform manner, including the excision/subtraction of both resolved and unresolved stellar contributions. Various coronal properties, such as the scale height and luminosity, are characterized for all the sample galaxies. For galaxies with high enough counting statistics, we also examine the thermal and chemical states of the coronal gas. We note on galaxies with distinct multi-wavelength characteristics which may affect the coronal properties. The uniformly processed images, spectra, and brightness profiles, as well as the inferred hot gas parameters, form a large X-ray database for studying the coronae around nearby disk galaxies. We also discuss various complications which may cause biases to this database and their possible corrections or effects, such as the uncertainty in the thermal and chemical states of hot gas, the different galactic disk inclination angles, the presence of AGN, and the contribution of the emission from charge exchange at interfaces between hot and cool gases. Results from a detailed correlation analysis are presented in a companion paper, to gain a more comprehensive statistical understanding of the origin of galactic coronae.

X-ray observations provide a key tool for exploring the properties of galactic coronae and their formation processes. In an earlier paper, we have presented a Chandra data analysis of the coronae of 53 nearby highly-inclined disc galaxies. Here we study the correlation of the X-ray measurements of the coronae with other galaxy properties and compare the results with those obtained for elliptical galaxies. A good correlation is present between the coronal luminosity (L X ) and the star formation rate (SFR). But we find a better correlation between L X and the total SN mechanical energy input rate (Ė SN ), including the expected contribution from both core collapsed (CC) and Type Ia SNe. The X-ray radiation efficiency (η ≡ L X /Ė SN ) of the coronae has a mean value of ∼ 0.4% with an rms of 0.50 ± 0.06 dex. η further correlates with M T F /M * (M T F is the total baryon mass measured from the rotation velocity and the Tully-Fisher relation, M * is the stellar mass measured from the K-band luminosity) and the CC SN rate surface density (F SN (CC) , in units of SN yr −1 kpc −2 ), which can be characterized as: η = (0.41 +0.13 −0.12 %)M T F /M * and η = (1.4 ± 0.5%)F −(0.29±0.11) SN (CC). These correlations reflect the roles that played by the gravitational mass and energetic feedback concentrations of the galaxies in determining their X-ray radiation efficiency. The characteristic temperature (T X ) of the coronal gas shows little dependence on the total or specific SFR, the cold gas content, or L X . The coronae of disc galaxies tend to be more X-ray luminous, hotter, and lower in the Fe/O abundance ratio than those of elliptical ones of similar masses. Early-type non-starburst disc galaxies tend to be more Fe-rich, while starburst ones have a roughly constant abundance ratio of Fe/O ∼ 0.36±0.12 solar. Our results are consistent with the coronal gas being mainly provided by stellar feedback in a galaxy stellar mass range of ∼ 10 8.7−11 M ⊙ . In addition, processes such as charge exchange at cool/hot gas interfaces, as well as various other environmental effects, are also needed to explain the diversity of the observed coronal X-ray properties.