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Register a new userPhylogenetic Analyses of Quasars and Galaxies
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Didier Fraix-Burnet
Publication date
2017
fields
Physics
and research's language is
English
Authors
Didier Fraix-Burnet n IPAG
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Phylogenetic approaches have proven to be useful in astrophysics. We have recently published a Maximum Parsimony (or cladistics) analysis on two samples of 215 and 85 low-z quasars (z < 0.7) which offer a satisfactory coverage of the Eigenvector 1-derived main sequence. Cladistics is not only able to group sources radiating at higher Eddington ratios, to separate radio-quiet (RQ) and radio-loud (RL) quasars and properly distinguishes core-dominated and lobe-dominated quasars, but it suggests a black hole mass threshold for powerful radio emission as already proposed elsewhere. An interesting interpretation from this work is that the phylogeny of quasars may be represented by the ontogeny of their central black hole, i.e. the increase of the black hole mass. However these exciting results are based on a small sample of low-z quasars, so that the work must be extended. We are here faced with two difficulties. The first one is the current lack of a larger sample with similar observables. The second one is the prohibitive computation time to perform a cladistic analysis on more that about one thousand objects. We show in this paper an experimental strategy on about 1500 galaxies to get around this difficulty. Even if it not related to the quasar study, it is interesting by itself and opens new pathways to generalize the quasar findings.
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We use the GALFORM semi-analytical model to study high density regions traced by radio galaxies and quasars at high redshifts. We explore the impact that baryonic physics has upon the properties of galaxies in these environments. Star-forming emission-line galaxies (Ly{alpha} and H{alpha} emitters) are used to probe the environments at high redshifts. Radio galaxies are predicted to be hosted by more massive haloes than quasars, and this is imprinted on the amplitude of galaxy overdensities and cross-correlation functions. We find that Ly{alpha} radiative transfer and AGN feedback indirectly affect the clustering on small scales and also the stellar masses, star- formation rates and gas metallicities of galaxies in dense environments. We also investigate the relation between protoclusters associated with radio galaxies and quasars, and their present- day cluster descendants. The progenitors of massive clusters associated with radio galaxies and quasars allow us to determine an average protocluster size in a simple way. Overdensities within the protoclusters are found to correlate with the halo descendant masses. We present scaling relations that can be applied to observational data. By computing projection effects due to the wavelength resolution of modern spectrographs and narrow-band filters we show that the former have enough spectral resolution to map the structure of protoclusters, whereas the latter can be used to measure the clustering around radio galaxies and quasars over larger scales to determine the mass of dark matter haloes hosting them.
We present spectroscopic identification of 32 new quasars and luminous galaxies discovered at 5.7 < z < 6.8. This is the second in a series of papers presenting the results of the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which exploits the deep multi-band imaging data produced by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. The photometric candidates were selected by a Bayesian probabilistic algorithm, and then observed with spectrographs on the Gran Telescopio Canarias and the Subaru Telescope. Combined with the sample presented in the previous paper, we have now identified 64 HSC sources over about 430 deg2, which include 33 high-z quasars, 14 high-z luminous galaxies, 2 [O III] emitters at z ~ 0.8, and 15 Galactic brown dwarfs. The new quasars have considerably lower luminosity (M1450 ~ -25 to -22 mag) than most of the previously known high-z quasars. Several of these quasars have luminous (> 10^(43) erg/s) and narrow (< 500 km/s) Ly alpha lines, and also a possible mini broad absorption line system of N V 1240 in the composite spectrum, which clearly separate them from typical quasars. On the other hand, the high-z galaxies have extremely high luminosity (M1450 ~ -24 to -22 mag) compared to other galaxies found at similar redshift. With the discovery of these new classes of objects, we are opening up new parameter spaces in the high-z Universe. Further survey observations and follow-up studies of the identified objects, including the construction of the quasar luminosity function at z ~ 6, are ongoing.
Observations of $z gtrsim 6$ quasars provide information on the early phases of the most massive black holes (MBHs) and galaxies. Current observations at sub-mm wavelengths trace cold and warm gas, and future observations will extend information to other gas phases and the stellar properties. The goal of this study is to examine the gas life cycle in a $z gtrsim 6$ quasar: from accretion from the halo to the galaxy and all the way into the MBH, to how star formation and the MBH itself affect the gas properties. Using 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, we investigate the distribution of the different gas phases in the interstellar medium across cosmic time. We assess the morphological evolution of the quasar host using different tracers (star- or gas-based) and the thermodynamic distribution of the MBH accretion-driven outflows, finding that obscuration in the disc is mainly due to molecular gas, with the atomic component contributing at larger scales and/or above/below the disc plane. Moreover, our results also show that molecular outflows, if present, are more likely the result of gas being lifted near the MBH than production within the wind because of thermal instabilities. Finally, we also discuss how different gas phases can be employed to dynamically constrain the MBH mass, and argue that resolutions below $sim 100$ pc yield unreliable estimates because of the strong contribution of the nuclear stellar component to the potential at larger scales.
Observations of high-redshift quasars provide information on the massive black holes (MBHs) powering them and the galaxies hosting them. 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. The relations at $z=0$, however, rely on stellar-based tracers of the galaxy properties. 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. 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. The high-redshift studies argued that MBHs at high redshift deviate from the local MBH-galaxy correlations. 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 $z=0$. When using the gas-based tracers, however, MBHs appear to be over-massive. The discrepancy between local and high-redshift MBHs seems caused by the different tracers employed, and necessary assumptions, and not by an intrinsic difference. 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.
This paper provides a catalogue of stars, quasars, and galaxies for the Southern Photometric Local Universe Survey Data Release 2 (S-PLUS DR2) in the Stripe 82 region. We show that a 12-band filter system (5 Sloan-like and 7 narrow bands) allows better performance for object classification than the usual analysis based solely on broad bands (regardless of infrared information). Moreover, we show that our classification is robust against missing values. Using spectroscopically confirmed sources retrieved from the Sloan Digital Sky Survey DR16 and DR14Q, we train a random forest classifier with the 12 S-PLUS magnitudes + 4 morphological features. A second random forest classifier is trained with the addition of the W1 (3.4 $mu$m) and W2 (4.6 $mu$m) magnitudes from the Wide-field Infrared Survey Explorer (WISE). Forty-four percent of our catalogue have WISE counterparts and are provided with classification from both models. We achieve 95.76% (52.47%) of quasar purity, 95.88% (92.24%) of quasar completeness, 99.44% (98.17%) of star purity, 98.22% (78.56%) of star completeness, 98.04% (81.39%) of galaxy purity, and 98.8% (85.37%) of galaxy completeness for the first (second) classifier, for which the metrics were calculated on objects with (without) WISE counterpart. A total of 2,926,787 objects that are not in our spectroscopic sample were labelled, obtaining 335,956 quasars, 1,347,340 stars, and 1,243,391 galaxies. From those, 7.4%, 76.0%, and 58.4% were classified with probabilities above 80%. The catalogue with classification and probabilities for Stripe 82 S-PLUS DR2 is available for download.
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