分类： 天文学 >> 天文学 提交时间： 2023-02-19
Rebecca L. Davies
Emma Ryan-Weber
Valentina D'Odorico
Sarah E. I. Bosman
Romain A. Meyer
George D. Becker
Guido Cupani
Manuela Bischetti
Alma M. Sebastian
Anna-Christina Eilers
Emanuele Paola Farina
Feige Wang
Jinyi Yang
Yongda Zhu
摘要： Intervening metal absorption lines in the spectra of z > 6 quasars are fundamental probes of the ionization state and chemical composition of circumgalactic and intergalactic gas near the end of the reionization epoch. Large absorber samples are required to robustly measure typical absorber properties and to refine models of the synthesis, transport, and ionization of metals in the early Universe. The "Ultimate XSHOOTER legacy survey of quasars at z~5.8-6.6" (XQR-30) has obtained high signal-to-noise spectra of 30 luminous quasars, nearly quadrupling the existing sample of 12 high quality z~6 quasar spectra. We use this unprecedented sample to construct a catalog of 778 systems showing absorption in one or more of MgII (360 systems), FeII (184), CII (46), CIV (479), SiIV (127), and NV (13) which span 2 5 absorbers, especially for CIV and SiIV which are important probes of the ionizing photon background at high redshift. The sample is 50% (90%) complete for rest-frame equivalent widths W > 0.03AA (0.09AA). We publicly release the absorber catalog along with completeness statistics and a Python script to compute the absorption search path for different ions and redshift ranges. This dataset is a key legacy resource for studies of enriched gas from the era of galaxy assembly to cosmic noon, and paves the way for even higher redshift studies with the James Webb Space Telescope and 30m-class telescopes.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Eduardo Banados
Jan-Torge Schindler
Bram P. Venemans
Thomas Connor
Roberto Decarli
Emanuele Paolo Farina
Chiara Mazzucchelli
Romain A. Meyer
Daniel Stern
Fabian Walter
Xiaohui Fan
Joseph F. Hennawi
Yana Khusanova
Nidia Morrell
Riccardo Nanni
Gael Noirot
Antonio Pensabene
Hans-Walter Rix
Joseph Simon
Gijs A. Verdoes Kleijn
摘要： The identification of bright quasars at z>6 enables detailed studies of
supermassive black holes, massive galaxies, structure formation, and the state
of the intergalactic medium within the first billion years after the Big Bang.
We present the spectroscopic confirmation of 55 quasars at redshifts 5.6
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Rebecca L. Davies
Emma Ryan-Weber
Valentina D'Odorico
Sarah E. I. Bosman
Romain A. Meyer
George D. Becker
Guido Cupani
Laura C. Keating
Manuela Bischetti
Frederick B. Davies
Anna-Christina Eilers
Emanuele Paolo Farina
Martin G. Haehnelt
Andrea Pallottini
Yongda Zhu
摘要： Intervening CIV absorbers are key tracers of metal-enriched gas in galaxy halos over cosmic time. Previous studies suggest that the CIV cosmic mass density ($\Omega_{\rm CIV}$) decreases slowly over 1.5 $\lesssim z\lesssim$ 5 before declining rapidly at $z\gtrsim$ 5, but the cause of this downturn is poorly understood. We characterize the $\Omega_{\rm CIV}$ evolution over 4.3 $\lesssim z\lesssim$ 6.3 using 260 absorbers found in 42 XSHOOTER spectra of $z\sim$ 6 quasars, of which 30 come from the ESO Large Program XQR-30. The large sample enables us to robustly constrain the rate and timing of the downturn. We find that $\Omega_{\rm CIV}$ decreases by a factor of 4.8 $\pm$ 2.0 over the ~300 Myr interval between $z\sim$ 4.7 and $z\sim$ 5.8. The slope of the column density (log N) distribution function does not change, suggesting that CIV absorption is suppressed approximately uniformly across 13.2 $\leq$ log N/cm$^{-2}$ < 15.0. Assuming that the carbon content of galaxy halos evolves as the integral of the cosmic star formation rate density (with some delay due to stellar lifetimes and outflow travel times), we show that chemical evolution alone could plausibly explain the fast decline in $\Omega_{\rm CIV}$ over 4.3 $\lesssim z\lesssim$ 6.3. However, the CIV/CII ratio decreases at the highest redshifts, so the accelerated decline in $\Omega_{\rm CIV}$ at $z\gtrsim$ 5 may be more naturally explained by rapid changes in the gas ionization state driven by evolution of the UV background towards the end of hydrogen reionization.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Emanuele Paolo Farina
Jan-Torge Schindler
Fabian Walter
Eduardo Bañados
Frederick B. Davies
Roberto Decarli
Anna-Christina Eilers
Xiaohui Fan
Joseph F. Hennawi
Chiara Mazzucchelli
Romain A. Meyer
Benny Trakhtenbrot
Marta Volonteri
Feige Wang
Gabor Worseck
Jinyi Yang
Thales A. Gutcke
Bram P. Venemans
Sarah E. I. Bosman
Tiago Costa
摘要： We present measurements of black hole masses and Eddington ratios for a sample of 38 bright (M$_{1450}$ 6. Combined with deep ALMA observations of the [CII] 158 $\mu$m line from the quasar host galaxies and VLT/MUSE investigations of the extended Ly$\alpha$ halos, this study provides fundamental clues to models of the formation and growth of the first massive galaxies and black holes. Compared to local scaling relations, z > 5.7 black holes appear to be over-massive with respect to their host galaxies, and their accretion properties do not change with host galaxy morphology. Under the assumption that the kinematics of the T ~ 10$^4$ K gas, traced by the extended Ly$\alpha$ halos, are dominated by the gravitational potential of the dark matter halo, we report a similar relation between the black hole mass and circular velocity to the one reported for z ~ 0 galaxies. These results paint a picture where the first supermassive black holes reside in massive halos at z > 6 and lead the first stages of galaxy formation by rapidly growing in mass with a duty cycle of order unity. However, this duty cycle needs to drastically drop towards lower redshifts, while the host galaxies continue forming stars at a rate of hundreds of solar masses per year, sustained by the large reservoirs of cool gas surrounding them.
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