分类： 天文学 >> 天文学 提交时间： 2023-02-19
Manuela Bischetti
Fabrizio Fiore
Chiara Feruglio
Valentina D'Odorico
Nahum Arav
Kastytis Zubovas
George Becker
Guido Cupani
Rebecca Davies
Anna-Christina Eilers
Emanuele Paolo Farina
Andrea Ferrara
Massimo Gaspari
Chiara Mazzucchelli
Masafusa Onoue
Enrico Piconcelli
Maria Vittoria Zanchettin
Yongda Zhu
摘要： Luminous quasars are powerful targets to investigate the role of feedback from supermassive black-holes (BHs) in regulating the growth phases of BHs themselves and of their host galaxies, up to the highest redshifts. Here we investigate the cosmic evolution of the occurrence and kinematics of BH-driven outflows, as traced by broad absorption line (BAL) features, due to the C IV ionic transition. We exploit a sample of 1935 quasars quasars at $z=2.1-6.6$ with bolometric luminosity log($L_{\rm bol}/$erg s$^{-1})\gtrsim46.8$, drawn from the Sloan Digital Sky Survey and from the X-shooter legacy survey of Quasars at Reionisation (XQR-30). We consider rest-frame optical bright quasars to minimise observational biases due to quasar selection criteria and we apply a homogeneous BAL identifiation analysis, based on employing composite template spectra to estimate the quasar intrinsic emission. We find a BAL quasar fraction close to 20\% at $z\sim2-4$, while it increases to almost 50\% at $z\sim6$. The velocity and width of the BAL features also increase at $z\gtrsim4.5$. We exclude that the redshift evolution of the BAL properties is due to differences in terms of quasar luminosity and accretion rate. These results suggest significant BH feedback occurring in the 1 Gyr old Universe, likely affecting the growth of BHs and, possibly, of their host galaxies, as supported by models of early BH and galaxy evolution.
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
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.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jan-Torge Schindler
Eduardo Bañados
Thomas Connor
Roberto Decarli
Xiaohui Fan
Emanuele Paolo Farina
Chiara Mazzucchelli
Riccardo Nanni
Hans-Walter Rix
Daniel Stern
Bram P. Venemans
Fabian Walter
摘要： We present the $z\!\approx\!6$ type-1 quasar luminosity function (QLF) based on the Pan-STARRS1 (PS1) quasar survey. The PS1 sample includes 125 quasars at $z\approx5.7-6.2$ with $-28\lesssim M_{1450}\lesssim-25$. Complemented by 48 fainter quasars from the SHELLQs survey, we evaluate the $z\approx6$ QLF over $-28\lesssim M_{1450}\lesssim-22$. Adopting a double power law with an exponential evolution of the quasar density ($\Phi(z)\propto10^{k(z-6)}$; $k=-0.7$), we use a maximum likelihood method to model our data. We find a break magnitude of $M^*=-26.38_{-0.60}^{+0.79}\,\text{mag}$, a faint end slope of $\alpha=-1.70_{-0.19}^{+0.29}$, and a steep bright end slope with $\beta=-3.84_{-1.21}^{+0.63}$. Based on our new QLF model we determine the quasar comoving spatial density at $z\!\approx\!6$ to be $n( M_{1450}<-26)=1.16_{-0.12}^{+0.13}\,\text{cGpc}^{-3}$. In comparison with the literature, we find the quasar density to evolve with a constant value of $k\approx-0.7$ from $z\approx7$ to $z\approx4$. Additionally, we derive an ionizing emissivity of $\epsilon_{912}(z=6) =7.23_{-1.02}^{+1.65}\times 10^{22}\,\text{erg}\,\text{s}^{-1}\text{Hz}^{-1}\text{cMpc}^{-3}$ based on the QLF measurement. Given standard assumptions and the recent measurement of the mean free path of Becker et al. (2021) at $z\approx6$ we calculate an HI photoionizing rate of $\Gamma_{\text{HI}}(z{=}6) \approx 6 \times10^{-16}\,\text{s}^{-1}$, strongly disfavoring a dominant role of quasars in hydrogen reionization.
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