Publikacje

Mg II Line Properties in Lobe-dominated Quasars

Autorzy: Wildy, Conor; Czerny, Bozena; Kuźmicz, Agnieszka

Czasopismo: Astrophysical Journal, 861, 54 (2018)

We investigate the relationships between Mg II λ2798 emission line properties, as well as between these properties and inclination angle and Fe II strength, in a lobe-dominated quasar sample. We find no correlation between Mg II line width and inclination, unlike previous studies of the general quasar population. This suggests that the Mg II emission region in these objects is not of a thin disk geometry; however, the average equivalent width (EW) of the line negates a spherical alternative. A positive correlation between Mg II EW and inclination cannot be ruled out, meaning there is no strong evidence that Mg II emission is anisotropic. Since thin disk emission would be highly directional, the geometric implications of these two findings are compatible. The lack of line width correlation with inclination may also indicate that Mg II is useful for estimating black hole masses in lobe-dominated quasar samples, since it is unbiased by orientation. Some quasars in our sample have almost edge-on viewing angles and therefore cannot have a smooth toroidal obscurer co-planar with the accretion disk. Alternatives may be a distorted dusty disk or a clumpy obscurer. This could result from the sample selection bias toward high inclination objects, rather than intrinsic differences between lobe-dominated and typical quasars. Five objects have visible [O III], allowing EW calculation and revealing it to be higher than in typical quasars. Since these objects are of high inclination, this finding supports the positive correlation between [O III] EW and inclination found in a previous study.

Pełen tekst pracy dostępny na stronie: https://arxiv.org/abs/1805.06263


Properties of active galaxies at the extreme of Eigenvector 1

Autorzy: Śniegowska, M.; Czerny, B.; You, B.; Panda, S.; Wang, J.-M.; Hryniewicz, K.; Wildy, C.

Czasopismo: Astronomy & Astrophysics, 613, A38 (2018)

Eigenvector 1 (EV1) is the formal parameter which allows the introduction of some order in the properties of the unobscured type 1 active galaxies. We aim to understand the nature of this parameter by analyzing the most extreme examples of quasars with the highest possible values of the corresponding eigenvalues RFe. We selected the appropriate sources from the Sloan Digital Sky Survey (SDSS) and performed detailed modeling, including various templates for the Fe II pseudo-continuum and the starlight contribution to the spectrum. Out of 27 sources with RFe larger than 1.3 and with the measurement errors smaller than 20% selected from the SDSS quasar catalog, only six sources were confirmed to have a high value of RFe, defined as being above 1.3. All other sources have an RFe of approximately 1. Three of the high RFe objects have a very narrow Hβ line, below 2100 km s-1 but three sources have broad lines, above 4500 km s-1, that do not seem to form a uniform group, differing considerably in black hole mass and Eddington ratio; they simply have a very similar EW([OIII]5007) line. Therefore, the interpretation of the EV1 remains an open issue.

Pełen tekst pracy dostępny na stronie: https://arxiv.org/abs/1701.03694


Astronomical Distance Determination in the Space Age. Secondary Distance Indicators

Autorzy: Czerny, Bozena; Beaton, Rachael; Bejger, Michał; Cackett, Edward; Dall'Ora, Massimo; .....

Czasopismo: Space Science Reviews, 214, 32 (2018)

The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations.

Pełen tekst pracy dostępny na stronie: https://arxiv.org/abs/1801.00598


Unbiased Large Spectroscopic Surveys of Galaxies Selected by SPICA Using Dust Bands

Autorzy: Kaneda, H., ..... Czerny, Bozena;

Czasopismo: Publications of the Astronomical Society of Australia, 34, 59 (2017)

The mid-infrared range contains many spectral features associated with large molecules and dust grains such as polycyclic aromatic hydrocarbons and silicates. These are usually very strong compared to fine-structure gas lines, and thus valuable in studying the spectral properties of faint distant galaxies. In this paper, we evaluate the capability of low-resolution mid-infrared spectroscopic surveys of galaxies that could be performed by SPICA. The surveys are designed to address the question how star formation and black hole accretion activities evolved over cosmic time through spectral diagnostics of the physical conditions of the interstellar/circumnuclear media in galaxies. On the basis of results obtained with Herschel far-infrared photometric surveys of distant galaxies and Spitzer and AKARI near- to mid-infrared spectroscopic observations of nearby galaxies, we estimate the numbers of the galaxies at redshift z > 0.5, which are expected to be detected in the polycyclic aromatic hydrocarbon features or dust continuum by a wide (10 deg2) or deep (1 deg2) blind survey, both for a given observation time of 600 h. As by-products of the wide blind survey, we also expect to detect debris disks, through the mid-infrared excess above the photospheric emission of nearby main-sequence stars, and we estimate their number. We demonstrate that the SPICA mid-infrared surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-infrared with SPICA.

Pełen tekst pracy dostępny na stronie: https://arxiv.org/abs/1710.07103


The relationship between Mg II broad emission and quasar inclination angle

Autorzy: Wildy, Conor; Czerny, Bozena; Panda, Swayamtrupta

Czasopismo: Frontiers in Astronomy & Space Sciences, 4, 43 (2017)

Several observed spectral properties of quasars are believed to be influenced by quasar orientation. In this investigation we examine the effect of orientation on the Mg II line located at 2798 A in a sample of 36 radio-loud quasars, with orientation angles having been obtained in a previous study using radio observations. We find no significant relationship between orientation angle and either Mg II line full-width at half-maximum or equivalent width. The lack of correlation with inclination angle contradicts previous studies which also use radio data as a proxy for inclination angle and suggests the Mg II emission region does not occupy a disk-like geometry. The lack of correlation with Mg II equivalent width, however, is reported in at least one previous study. Although the significance is not very strong (86 percent), there is a possible negative relationship between inclination angle and Fe II strength which, if true, could explain the Fe II anti-correlation with [O III] strength associated with Eigenvector 1. Interestingly, there are objects having almost edge-on inclinations while still exhibiting broad lines. This could be explained by a torus which is either clumpy (allowing sight lines to the central engine) or mis-aligned with the accretion disk.

Pełen tekst pracy dostępny na stronie: https://arxiv.org/abs/1711.08926


The physical driver of the optical Eigenvector 1 in Quasar Main Sequence

Autorzy: Panda, Swayamtrupta; Czerny, Bozena; Wildy, Conor

Czasopismo: Frontiers in Astronomy & Space Sciences, in press

Quasars are complex sources, characterized by broad band spectra from radio through optical to X-ray band, with numerous emission and absorption features. However, Boroson & Green (1992) used Principal Component Analysis (PCA), and with this analysis they were able to show significant correlations between the measured parameters. The leading component, related to Eigenvector 1 (EV1) was dominated by the anticorrelation between the FeII optical emission and [OIII] line and EV1 alone contained 30% of the total variance. It opened a way in defining a quasar main sequence, in close analogy to the stellar main sequence on the Hertzsprung-Russel (HR) diagram (Sulentic et al. 2001). The question still remains which of the basic theoretically motivated parameters of an active nucleus (Eddington ratio, black hole mass, accretion rate, spin, and viewing angle) is the main driver behind the EV1. Here we limit ourselves to the optical waveband, and concentrate on theoretical modelling the FeII to Hβ ratio, and we test the hypothesis that the physical driver of EV1 is the maximum of the accretion disk temperature, reflected in the shape of the spectral energy distribution (SED). We performed computations of the Hβ and optical FeII for a broad range of SED peak position using CLOUDY photoionisation code. We assumed that both Hβ and FeII emission come from the Broad Line Region represented as a constant density cloud in a plane-parallel geometry. We expected that a hotter disk continuum will lead to more efficient production of FeII but our computations show that the FeII to Hβ ratio actually drops with the rise of the disk temperature. Thus either hypothesis is incorrect, or approximations used in our paper for the description of the line emissivity is inadequate.

Pełen tekst pracy dostępny na stronie: http://arxiv.org/abs/1710.10180


On the Intermediate Line Region in AGNs

Autorzy: Adhikari, Tek P.; Różańska, Agata; Hryniewicz, Krzysztof; Czerny, Bozena; Ferland, Gary J.

Czasopismo: Frontiers in Astronomy & Space Sciences, 4, 19 (2017)

In this paper we explore the intermediate line region (ILR) by using the photoionisation simulations of the gas clouds present at different radial distances from the center, corresponding to the locations from BLR out to NLR in four types of AGNs. We let for the presence of dust whenever conditions allow for dust existence. All spectral shapes are taken from the recent multi-wavelength campaigns. The cloud density decreases with distance as a power law. We found that the slope of the power law density profile does not affect the line emissivity radial profiles of major emission lines: Hβ, He II, Mg II, C III] and [O III]. When the density of the cloud at the sublimation radius is as high as 1011.5 cm−3, the ILR should clearly be seen in the observations independently of the shape of the illuminating radiation. Moreover, our result is valid for low ionization nuclear emission regions of active galaxies.

Pełen tekst pracy dostępny na stronie: http://arxiv.org/abs/1709.07393


Failed Radiatively Accelerated Dusty Outflow Model of the Broad Line Region in Active Galactic Nuclei. I. Analytical Solution

Autorzy: Czerny, B.; Li, Yan-Rong; Hryniewicz, K.; Panda, S.; Wildy, C.; Sniegowska, M.; Wang, J.-M.; Sredzinska, J.; Karas, V.

Czasopismo: The Astrophysical Journal, 846, 154 (2017)

The physical origin of the Broad Line Region in Active Galactic Nuclei is still unclear despite many years of observational studies. The reason is that the region is unresolved and the reverberation mapping results imply complex velocity field. We adopt a theory-motivated approach to identify the principal mechanism responsible for this complex phenomenon. We consider the possibility that the role of dust is essential. We assume that the local radiation pressure acting on the dust in the accretion disk atmosphere launches the outflow of material, but higher above the disk the irradiation from the central parts cause the dust evaporation and a subsequent fall back. This failed radiatively accelerated dusty outflow (FRADO) is expected to represent the material forming low ionization lines. In this paper we formulate simple analytical equations describing the cloud motion, including the evaporation phase. The model is fully described just by the basic parameters: black hole mass, accretion rate, black hole spin and the viewing angle. We study how the spectral line generic profiles correspond to this dynamics. We show that the virial factor calculated from our model strongly depends on the black hole mass in case of enhanced dust opacity, and thus it then correlates with the line width. This could explain why the virial factor measured in galaxies with pseudo-bulges differs from that obtained from objects with classical bulges although the trend predicted by the current version of the model is opposite to the observed trend.

Pełen tekst pracy dostępny na stronie: http://arxiv.org/abs/1706.07958

Self-consistent dynamical model of the Broad Line Region

Autorzy: Czerny, Bozena; Li, Yan-Rong; Sredzinska, Justyna; Hryniewicz, Krzysztof; Panda, Swayam; Wildy, Conor; Karas, Vladimir

Czasopismo: Frontiers in Astronomy & Space Sciences, 4, 5 (2017)

We develope a self-consistent description of the Broad Line Region based on the concept of the failed wind powered by the radiation pressure acting on dusty accretion disk atmosphere in Keplerian motion. The material raised high above the disk is illuminated, dust evaportes, and the matter falls back towards the disk. This material is the source of emission lines. The model predicts the inner and outer radius of the region, the cloud dynamics under the dust radiation pressure and, subsequently, just the gravitational field of the central black hole, which results in assymetry between the rise and fall. Knowledge of the dynamics allows to predict the shapes of the emission lines as functions of the basic parameters of an active nucleus: black hole mass, accretion rate, black hole spin (or accretion efficiency) and the viewing angle with respect to the symmetry axis. Here we show preliminary results based on analytical approximations to the cloud motion.

Pełen tekst pracy dostępny na stronie: http://arxiv.org/abs/1705.08812


SALT long-slit spectroscopy of HE 0435-4312: fast displacement in the Mg II emission line

Autorzy: Sredzinska, J.; Czerny, B.; Hryniewicz, K.; Krupa, M.; Marziani, P.; Adhikari, T. P.; Basak, R.; You, B.; Bilicki, M.

Czasopismo: Astronomy & Astrophysics, 601, A32 (2017)

The Mg II emission line is visible in the optical band for intermediate redshift quasars (0.4 < z < 1.6) and it is thus an extremely important tool to measure the black hole mass and to understand the structure of the Broad Line Region. We aim to determine the substructure and the variability of the Mg II line with the aim to identify which part of the line comes from a medium in Keplerian motion. Using the Southern African Large Telescope (SALT) with the Robert Stobie Spectrograph (RSS) we performed ten spectroscopic observations of quasar HE 0435-4312 (z = 1.2231) over a period of three years (Dec 23/24, 2012 to Dec 7/8, 2015). Both the Mg II line and the Fe II pseudo-continuum increase with time. We clearly detect the systematic shift of the Mg II line with respect to the Fe II over the years, corresponding to the acceleration of 104 pm 14 km/s/year in the quasar rest frame. The Mg II line shape is clearly non-Gaussian but single-component, and the increase in line equivalent width and line shift is not accompanied with significant evolution of the line shape. We analyse the conditions in the Mg II and Fe II formation region and we note that the very large difference in the covering factor and the turbulent velocity also support the conclusion that the two regions are spatially separated. The measured acceleration of the line systematic shift is too large to connect it with the orbital motion at a distance of the Broad Line Region (BLR) in this source. It may imply a precessing inner disk illuminating the BLR. Further monitoring is still needed to better constrain the variability mechanism.

Pełen tekst pracy dostępny na stronie: http://arxiv.org/abs/1602.01975

The properties of active galaxies at the extreme of eigenvector 1

Autorzy: Sniegowska, M.; Czerny, B.; You, B.; Panda, S.; Wang, J.-M.; Hryniewicz, K.; Wildy, C.

Czasopismo: Astronomy & Astrophysics (złożone do druku)

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Pełen tekst pracy dostępny na stronie: http://arxiv.org/abs/1701.03694

A Test of the Formation Mechanism of the Broad Line Region in Active Galactic Nuclei

Autorzy: Czerny, B.; Du, Pu; Wang, Jian-Min; Karas, Vladimir

Czasopismo: The Astrophysical Journal, 832, A15 (2016)

The origin of the Broad Line Region (BLR) in active galaxies remains unknown. It seems to be related to the underlying accretion disk but an efficient mechanism is required to rise the material from the disk surface without giving too strong signatures of the outflow in the case of the low ionization lines. We discuss in detail two proposed mechanisms: (i) radiation pressure acting on dust in the disk atmosphere creating a failed wind (ii) the gravitational instability of the underlying disk. We compare the predicted location of the inner radius of the BLR in those two scenarios with the observed position obtained from the reverberation studies of several active galaxies. The failed dusty outflow model well represents the observational data while the predictions of the self-gravitational instability are not consistent with observations. The issue remains why actually we do not see any imprints of the underlying disk instability in the BLR properties.

Pełen tekst pracy dostępny na stronie: http://arxiv.org/abs/1610.00420


The mass of the black hole in RE J1034+396

Autorzy: Czerny, B.; You, B.; Kurcz, A.; Średzińska, J.; Hryniewicz, K.; Nikołajuk, M.; Krupa, M.; Wang, J.-M.; Hu, C.; Życki, P. T.

Czasopismo: Astronomy & Astrophysics, 594, A102 (2016)

The black hole mass measurement in active galaxies is a challenge, particularly in sources where the reverberation method cannot be applied. We aim to determine the black hole mass in a very special object, RE J1034+396, one of the two AGN with QPO oscillations detected in X-rays, and a single bright AGN with optical band totally dominated by starlight. We fit the stellar content using the code starlight, and the broad band disk contribution to optical/UV/X-ray emission is modeled with optxagnf. We also determine the black hole mass using several other independent methods. Various methods give contradictory results. Most measurements of the blacc hole mass are in the range 1.e6-1.e7 Msun, and the measurements based on dynamics give higher values than measurements based on Hbeta and Mg II emission lines.

Pełen tekst pracy dostępny na stronie: http://arxiv.org/abs/1601.02498