Quasars as tracers
of the dark energy

Publications

Scientific publications presenting the results of our project "Quasars as tracers of the dark energy".


The mass of the black hole in RE J1034+396

Authors: B. Czerny, B. You, A. Kurcz, J. Średzinska, K. Hryniewicz, M. Nikołajuk, and M. Krupa

Publisher: Astronomy & Astrophysics

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Accretion in active galactic nuclei and disk-jet coupling

Authors: Bozena Czerny, Bei You

Publisher: Astronomische Nachrichten, 2016 (in press)

We review the current state of understanding how accretion onto a black hole proceeds and what are they key elements needed to form relativistic jets. Since the theoretical progress is severely halted by the lack of deep understanding of the microphysics involved, particularly in the presence of strong magnetic fields, all proposed solutions have a status of models, and their selection has to be based directly on observational constraints.

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The dust origin of the Broad Line Region and the model consequences for AGN unification scheme

Bozena Czerny, Justyna Modzelewska, Francesco Petrogalli, Wojtek Pych, Tek P. Adhikari, Piotr T. Zycki, Krzysztof Hryniewicz, Magdalena Krupa, Agnieszka Kurcz, Marek Nikolajuk

Publisher: Advances in Space Research, 55, 1806 (2015)

We propose a very simple physical mechanism responsible for the formation of the Low Ionization Line part of the Broad Line Region in Active Galactic Nuclei. It explains the scaling of the Broad Line Region size with the monochromatic luminosity, including the exact slope and the proportionality constant, seen in the reverberation studies of nearby sources. The scaling is independent from the mass and accretion rate of an active nucleus. The mechanism predicts the formation of a dust-driven wind in the disk region where the local effective temperature of a non-illuminated accretion disk drops below 1000 K and allows for dust formation. We explore now the predictive power of the model with the aim to differentiate between this model and the previously proposed mechanisms of the formation of the Broad Line Region. We discuss the expected departures from the universal scaling at long wavelength, and the role of the inclination angle of the accretion disk in the source. We compare the expected line profiles with Mg II line profiles in the quasars observed by us with the SALT telescope. We also discuss the tests based on the presence or absence of the broad emission lines in low luminosity active galaxies. Finally, we discuss the future tests of the model to be done with expected ground-based observations and satellite missions.

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Quasars as tracers of cosmic flows

Authors: J. Modzelewska, B. Czerny, M. Bilicki, K. Hryniewicz, M. Krupa, F. Petrogalli, W. Pych, A. Kurcz, A. Udalski

Publisher: Proceedings of IAU Symposium 308 "The Zeldovich Universe: Genesis and Growth of the Cosmic Web", 23-28 June 2014, Tallinn, Estonia

Quasars, as the most luminous persistent sources in the Universe, have broad applications for cosmological studies. In particular, they can be employed to directly measure the expansion history of the Universe, similarly to SNe Ia. The advantage of quasars is that they are numerous, cover a broad range of redshifts, up to z=7, and do not show significant evolution of metallicity with redshift. The idea is based on the relation between the time delay of an emission line and the continuum, and the absolute monochromatic luminosity of a quasar. For intermediate redshift quasars, the suitable line is Mg II. Between December 2012 and March 2014, we performed five spectroscopic observations of the QSO CTS C30.10 (z=0.900) using the South African Large Telesope (SALT), supplemented with photometric monitoring, with the aim of determining the variability of the line shape, changes in the total line intensity and in the continuum. We show that the method is very promising.

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SALT long-slit spectroscopy of LBQS 2113-4538: variability of the Mg II and Fe II component

Authors: K. Hryniewicz, B. Czerny, W. Pych, A. Udalski, M. Krupa, A. Swieton, J. Kaluzny

Publisher: Astronomy & Astrophysics, 562, A34 (2014)

The Mg II line is of extreme importance in intermediate redshift quasars since it allows us to measure the black hole mass in these sources and to use these sources as probes of the distribution of dark energy in the Universe, as a complementary tool to SN Ia. Reliable use of Mg II requires a good understanding of all the systematic effects involved in the measurement of the line properties, including the contamination by Fe II UV emission. We performed three spectroscopic observations of a quasar LBQS 2113-4538 (z = 0.956) with the SALT telescope separated in time by several months and we analyze in detail the mean spectrum and the variability in the spectral shape. We show that even in our good-quality spectra the Mg II doublet is well fit by a single Lorentzian shape. We tested several models of the Fe II pseudo-continuum and showed that one of them well represents all the data. The amplitudes of both components vary in time, but the shapes do not change significantly. The measured line width of LBQS 2113-4538 identifies this object as a class A quasar. The upper limit of 3% for the contribution of the Narrow Line Region (NLR) to Mg II may suggest that the separation of the Broad Line Region (BLR) and NLR disappears in this class of objects.

Full text: http://arxiv.org/abs/1308.3980


Dusty origin of the Broad Line Region in active galaxies

Authors: Bozena Czerny, Krzysztof Hryniewicz, Janusz Kaluzny, Ishita Maity

Wydawnictwo: Proceedings of IAUS 290 "Feeding Compact Objects: Accretion on All Scales", C. M. Zhang, T. Belloni, M. Mendez & S. N. Zhang (eds.)

The most characteristic property of active galaxies, including quasars, are prominent broad emission lines. I will discuss an interesting possibility that dust is responsible for this phenomenon. The dust is known to be present in quasars in the form of a dusty/molecular torus which results in complexity of the appearance of active galaxies. However, this dust is located further from the black hole than the Broad Line Region. We propose that the dust is present also closer in and it is actually responsible for formation of the broad emission lines. The argument is based on determination of the temperature of the disk atmosphere underlying the Broad Line Region: it is close to 1000 K, independently from the black hole mass and accretion rate of the object. The mechanism is simple and universal but leads to a considerable complexity of the active nucleus surrounding. The understanding the formation of BLR opens a way to use it reliably - in combination with reverberation measurement of its size - as standard candles in cosmology.

Full text: http://arxiv.org/abs/1211.1232


Equation of state of dark energy from quasar monitoring: Reverberation strategy

Authors: Czerny, B.; Maity, I.; Hryniewicz, K.; Schwarzenberg-Czerny, A.; Zycki, P. T.; Bilicki, M.

Publisher: Astronomy & Astrophysics, 556, A97 (2013)

High redshift quasars can be used to deduce the distribution of dark energy in the Universe, as a complementary tool to SN Ia. The method is based on determination of the size of the Broad Line Region from the emission line delay, determination of the absolute monochromatic luminosity either from the observed statistical relation or from a model of the formation of the Broad Line Region, and determination of the observed monochromatic flux from photometry. This allows to obtain the luminosity distance to a quasar independently from its redshift. The accuracy of the measurements is however, a key issue. We model the expected accuracy of the measurements by creating artificial quasar monochromatic lightcurves and responses from the Broad Line Region under various assumptions about the variability of a quasar, Broad Line Region extension, distribution of the measurements in time, accuracy of the measurements and the intrinsic line variability. We show that the five year monitoring based on Mg II line should give the accuracy of 0.06 - 0.32 magnitude in the distance modulus which allows to put interesting constraints on the cosmological models. Monitoring of higher redshift quasars based on CIV lines is problematic due to much higher level of the intrinsic variability of CIV in comparison with Mg II.

Full text: http://arxiv.org/abs/1212.0472