scholarly journals Reionization with galaxies and active galactic nuclei

2020 ◽  
Vol 495 (3) ◽  
pp. 3065-3078 ◽  
Author(s):  
Pratika Dayal ◽  
Marta Volonteri ◽  
Tirthankar Roy Choudhury ◽  
Raffaella Schneider ◽  
Maxime Trebitsch ◽  
...  

ABSTRACT In this work we investigate the properties of the sources that reionized the intergalactic medium (IGM) in the high-redshift Universe. Using a semi-analytical model aimed at reproducing galaxies and black holes in the first ∼1.5 Gyr of the Universe, we revisit the relative role of star formation and black hole accretion in producing ionizing photons that can escape into the IGM. Both star formation and black hole accretion are regulated by supernova feedback, resulting in black hole accretion being stunted in low-mass haloes. We explore a wide range of combinations for the escape fraction of ionizing photons (redshift-dependent, constant, and scaling with stellar mass) from both star formation ($\langle f_{\rm esc}^{\rm sf} \rangle$) and AGN ($f_{\rm esc}^{\rm bh}$) to find: (i) the ionizing budget is dominated by stellar radiation from low stellar mass ($M_*\lt 10^9 \, {\rm \rm M_\odot }$) galaxies at z > 6 with the AGN contribution (driven by $M_{bh}\gt 10^6 \, {\rm \rm M_\odot }$ black holes in $M_* \gtrsim 10^9\, {\rm \rm M_\odot }$ galaxies) dominating at lower redshifts; (ii) AGN only contribute $10-25{{\ \rm per\ cent}}$ to the cumulative ionizing emissivity by z = 4 for the models that match the observed reionization constraints; (iii) if the stellar mass dependence of $\langle f_{\rm esc}^{\rm sf} \rangle$ is shallower than $f_{\rm esc}^{\rm bh}$, at z < 7 a transition stellar mass exists above which AGN dominate the escaping ionizing photon production rate; (iv) the transition stellar mass decreases with decreasing redshift. While AGN dominate the escaping emissivity above the knee of the stellar mass function at z ∼ 6.8, they take-over at stellar masses that are a tenth of the knee mass by z = 4.

2020 ◽  
Vol 642 ◽  
pp. A65
Author(s):  
R. Carraro ◽  
G. Rodighiero ◽  
P. Cassata ◽  
M. Brusa ◽  
F. Shankar ◽  
...  

Aims. We study the coevolution between the black hole accretion rate (BHAR) and the star formation rate (SFR) in different phases of galaxy life: main-sequence star-forming galaxies, quiescent galaxies, and starburst galaxies at different cosmic epochs. Methods. We exploited the unique combination of depth and area in the COSMOS field and took advantage of the X-ray data from the Chandra COSMOS-Legacy survey and the extensive multiwavelength ancillary data presented in the COSMOS2015 catalog, including in particular the UVista Ultra-deep observations. These large datasets allowed us to perform an X-ray stacking analysis and combine it with detected sources in a broad redshift interval (0.1 <  z <  3.5) with unprecedented statistics for normal star-forming, quiescent, and starburst galaxies. The X-ray luminosity was used to predict the black holeAR, and a similar stacking analysis on far-infrared Herschel maps was used to measure the corresponding obscured SFR for statistical samples of sources in different redshifts and stellar mass bins. Results. We focus on the evolution of the average SFR-stellar mass (M*) relation and compare it with the BHAR-M* relation. This extends previous works that pointed toward the existence of almost linear correlations in both cases. We find that the ratio between BHAR and SFR does not evolve with redshift, although it depends on stellar mass. For the star-forming populations, this dependence on M* has a logarithmic slope of ∼0.6 and for the starburst sample, the slope is ∼0.4. These slopes are both at odds with quiescent sources, where the dependence remains constant (log(BHAR/SFR) ∼ −3.4). By studying the specific BHAR and specific SFR, we find signs of downsizing for M* and black hole mass (MBH) in galaxies in all evolutionary phases. The increase in black hole mass-doubling timescale was particularly fast for quiescents, whose super-massive black holes grew at very early times, while accretion in star-forming and starburst galaxies continued until more recent times. Conclusions. Our results support the idea that the same physical processes feed and sustain star formation and black hole accretion in star-forming galaxies while the starburst phase plays a lesser role in driving the growth of the supermassive black holes, especially at high redshift. Our integrated estimates of the M* − MBH relation at all redshifts are consistent with independent determinations of the local M* − MBH relation for samples of active galactic nuclei. This adds key evidence that the evolution in the BHAR/SFR is weak and its normalization is relatively lower than that of local dynamical M* − MBH relations.


2019 ◽  
Vol 493 (1) ◽  
pp. 1500-1511 ◽  
Author(s):  
Francesco Shankar ◽  
David H Weinberg ◽  
Christopher Marsden ◽  
Philip J Grylls ◽  
Mariangela Bernardi ◽  
...  

ABSTRACT The masses of supermassive black holes at the centres of local galaxies appear to be tightly correlated with the mass and velocity dispersions of their galactic hosts. However, the local Mbh–Mstar relation inferred from dynamically measured inactive black holes is up to an order-of-magnitude higher than some estimates from active black holes, and recent work suggests that this discrepancy arises from selection bias on the sample of dynamical black hole mass measurements. In this work, we combine X-ray measurements of the mean black hole accretion luminosity as a function of stellar mass and redshift with empirical models of galaxy stellar mass growth, integrating over time to predict the evolving Mbh–Mstar relation. The implied relation is nearly independent of redshift, indicating that stellar and black hole masses grow, on average, at similar rates. Matching the de-biased local Mbh–Mstar relation requires a mean radiative efficiency ε ≳ 0.15, in line with theoretical expectations for accretion on to spinning black holes. However, matching the ‘raw’ observed relation for inactive black holes requires ε ∼ 0.02, far below theoretical expectations. This result provides independent evidence for selection bias in dynamically estimated black hole masses, a conclusion that is robust to uncertainties in bolometric corrections, obscured active black hole fractions, and kinetic accretion efficiency. For our fiducial assumptions, they favour moderate-to-rapid spins of typical supermassive black holes, to achieve ε ∼ 0.12–0.20. Our approach has similarities to the classic Soltan analysis, but by using galaxy-based data instead of integrated quantities we are able to focus on regimes where observational uncertainties are minimized.


2015 ◽  
Vol 449 (2) ◽  
pp. 1470-1485 ◽  
Author(s):  
Marta Volonteri ◽  
Pedro R. Capelo ◽  
Hagai Netzer ◽  
Jillian Bellovary ◽  
Massimo Dotti ◽  
...  

2018 ◽  
Vol 477 (1) ◽  
pp. 780-790 ◽  
Author(s):  
C Vignali ◽  
E Piconcelli ◽  
M Perna ◽  
J Hennawi ◽  
R Gilli ◽  
...  

2019 ◽  
Vol 622 ◽  
pp. A18
Author(s):  
H. R. Stacey ◽  
J. P. McKean ◽  
N. J. Jackson ◽  
P. N. Best ◽  
G. Calistro Rivera ◽  
...  

Determining the star-forming properties of radio-quiet quasars is important for understanding the co-evolution of star formation and black hole accretion. We present the detection of the gravitationally lensed radio-quiet quasars SDSS J1055+4628, SDSS J1313+5151, and SBS 1520+530 at 144 MHz, which fall in the HETDEX Spring Field targeted in the LOFAR Two-metre Sky Survey (LoTSS) first full data release. We compare their radio and far-infrared luminosities relative to the radio–infrared correlation and find that their radio luminosities can be explained by star formation. The implied star formation rates derived from their radio and infrared luminosities are between 20 and 300 M ⊙ yr−1. These detections represent the first study of gravitationally lensed sources with LOFAR, opening a new frequency window for investigating the star-forming properties of high-redshift quasars at radio wavelengths. We consider the implications for future data releases and estimate that many of the objects in our parent sample will be detected during LoTSS, significantly increasing the fraction of gravitationally lensed radio-quiet quasars with radio detections.


2020 ◽  
Vol 498 (1) ◽  
pp. 1469-1479
Author(s):  
Clare F Wethers ◽  
Jari Kotilainen ◽  
Malte Schramm ◽  
Andreas Schulze

ABSTRACT Low-ionization broad absorption line quasars (LoBALs) mark an important, yet poorly understood, population of quasars showing direct evidence for energetic mass outflows. We outline a sample of 12 luminous (Lbol &gt; 1046 ergs−1) LoBALs at 2.0 &lt; z &lt; 2.5 – a key epoch in both star formation and black hole accretion, which have been imaged as part of a targeted program with the Herschel Spectral and Photometric Imaging REceiver (SPIRE). We present K-band NOTCam spectra for three of these targets, calculating their spectroscopic redshifts, black hole masses, and bolometric luminosities, and increasing the total number of LoBAL targets in our sample with spectral information from five to eight. Based on FIR observations from Herschel SPIRE, we derive prolific star formation rates (SFRs) ranging 740–2380 M⊙ yr−1 for the detected targets, consistent with LoBALs existing in an evolutionary phase associated with starburst activity. Furthermore, an upper limit of &lt;440 M⊙ yr−1 is derived for the non-detections, meaning moderate-to-high SFRs cannot be ruled out, even among the undetected targets. Indeed, we detect an enhancement in both the SFRs and FIR fluxes of LoBALs compared to HiBAL and non-BAL quasars, further supporting the evolutionary LoBAL paradigm. Despite this enhancement in SFR, however, the environments of LoBALs appear entirely consistent with the general galaxy population at 2.0 &lt; z &lt; 2.5.


2019 ◽  
Vol 489 (1) ◽  
pp. 802-819 ◽  
Author(s):  
Angelo Ricarte ◽  
Michael Tremmel ◽  
Priyamvada Natarajan ◽  
Thomas Quinn

ABSTRACT We study the link between supermassive black hole growth and the stellar mass assembly of their host galaxies in the state-of-the-art Romulus suite of simulations. The cosmological simulations Romulus25 and RomulusC employ innovative recipes for the seeding, accretion, and dynamics of black holes in the field and cluster environments, respectively. We find that the black hole accretion rate traces the star formation rate among star-forming galaxies. This result holds for stellar masses between 108 and 1012 solar masses, with a very weak dependence on host halo mass or redshift. The inferred relation between accretion rate and star formation rate does not appear to depend on environment, as no difference is seen in the cluster/proto-cluster volume compared to the field. A model including the star formation rate, the black hole-to-stellar mass ratio, and the cold gas fraction can explain about 70 per cent of all variations in the black hole accretion rate among star-forming galaxies. Finally, bearing in mind the limited volume and resolution of these cosmological simulations, we find no evidence for a connection between black hole growth and galaxy mergers, on any time-scale and at any redshift. Black holes and their galaxies assemble in tandem in these simulations, regardless of the larger scale intergalactic environment, suggesting that black hole growth simply follows star formation on galactic scales.


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