arXiv subjects

Krzysztof Hryniewicz

Publications and source records attributed to Krzysztof Hryniewicz.

At least 19 recordsLinked to original sources

arXiv2026

Extending the Little Red Dot population at intermediate redshift with VIPERS

Little red dots (LRDs) are a recently identified population of compact, red sources characterised by a distinctive V-shaped UV-to-optical continuum and broad emission lines. Their physical structure and evolution remain uncertain, while their properties at intermediate redshifts are largely unexplored. We identify and characterise LRD-like sources at 0.5 0.5, bridging local and high-redshift studies. Their abundance, compact morphology, environmental properties, and multi-wavelength emission provide new constraints on the evolution and physical origin of this population.

astro-ph.GA↗

arXiv2026

Weak emission line quasar SDSS J101353.45+492758.1 I. Continuum fitting

We present a broadband study of the WLQ SDSS J101353.45+492758.1, which displays a nearly featureless UV-optical spectrum with only a weak Mg II line alongside an exceptionally low X-ray flux. We model its spectral energy distribution using the relativistic thin-disk model kerrbb with a power law, and the multicomponent AGN model relagn, a physically motivated extension of agnsed incorporating warm and hot Comptonizing regions. Our fits constrain the black hole mass, accretion rate, X-ray loudness, and coronal energetics. Both approaches yield consistent BH masses of M_{BH} \approx 2 \times 10^{9} M_\odot and an Eddington accretion rate of \dot m \approx 0.1. The relagn fit including a warm Comptonizing region provides a significantly improved representation of the UV-soft X-ray continuum. The warm corona, characterized by kTe \simeq 0.20 keV, Γ \simeq 3.8, and an optical depth τ \simeq 7.26, extends to \sim 34 R_g. The hot corona appears compact and energetically suppressed, leading to an intrinsically weak X ray output with log(L_{X}/L_{bol}) \simeq -4.29, among the lowest reported for WLQs. The α_{ox} \sim 2.06 indicates the source to be in high/soft AGN spectral state. The combination of a luminous, standard disk and extremely weak hot corona suggests that this quasar hosts a highly inefficient inner coronal region. This explains its X-ray faintness and extreme deficit of high-ionization emission lines. The source may represent an AGN analog in "ultrasoft" accretion state, or a system in which the ionizing continuum is suppressed by a compact or quenched corona. Our study suggests that the source is not accreting at high Eddington ratio, highlighting the physical diversity of WLQs, and supports the view that geometric and radiative effects jointly shape their extreme spectral properties.

astro-ph.HE↗

arXiv2026

The optical-infrared relation for active galactic nuclei: The role of contaminations

The main objective is to calibrate the OPT-IR luminosity relation for quasars, focusing on accurate estimations of dusty torus and accretion disk luminosities. We analyzed contaminations related to host galaxies, particularly from polar dust, the interstellar medium, and stellar emission that affect the optical and infrared. We used a sample of nearly 400 quasars with photometrical observations and spectroscopical redshift divided into four redshift bins (0.7-2.4). Full spectral energy distribution (SED) fitting was performed with the CIGALE code, and results were compared with simplified photometric luminosity estimates. The impact of non-active galactic nucleus components and the role of polar dust in the fitting process were assessed. We show that for sources with a disk luminosity above 10^45 [erg/s], the photometric estimates are consistent with SED-based values. While polar dust contributes marginally to luminosity, its presence significantly alters SED fitting, particularly the torus opening angle and cold dust properties. In the optical domain, stellar emission is the dominant contamination. In the infrared, disk emission and cold dust play major roles. We propose two empirical calibrations for the OPT-IR relation. We conclude that the optical band is dominated by the accretion disk component above 10^45 or 10^46 [erg/s] depending on redshift, while IR luminosity is dominated by the dusty torus emission above 1.6 $\times$ 10^45 or 2 $\times$ 10^46 [erg/s] depending on the redshift. In this high-luminosity regime, simplified photometric methods yield reliable disk and torus luminosity estimates. The aim of the analysis we present is to test the parameter space in order to build a well behaving OPT-IR nonlinear luminosity relation for quasars that could serve as a cosmological probe.

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arXiv2025

A constant pressure model for the warm absorber in Mrk 509

We present the analysis of 900 ks high-resolution RGS XMM-Newton observations of the nearby Seyfert galaxy Mrk 509 with the use of a self-consistent warm absorber (WA) model. We perform a physically motivated approach to the modeling of WA as a stratified medium in constant total pressure (CTP) regime. Powerful outflows are fundamental ingredients of any active galactic nuclei (AGN) structure. They may significantly affect the cosmological environment of their host galaxy. High-resolution X-ray data are best suited for outflow's studies, and the observed absorption lines on heavy elements are evidence of the physical properties of an absorbing gas. Our models allow us to fit continuum shapes bounded together with the line profiles, which gives additional constraints on the gas structure of WA in this source. In this work, we benchmark and test the CTP model on the soft X-ray spectrum of Mrk 509. A grid of synthetic absorbed spectra was computed with the photoionization code Titan assuming that the system was under CTP. As an illuminating spectral energy distribution (SED), we used the most actual multiwavelength observations available for Mrk 509. We apply these models to the high-resolution spectrum of the WA in the Mrk 509, taking into account cold/warm/hot Galactic absorption on the way to the observer. CTP gas with $\log ξ_{0} \sim 1.9$, defined on the cloud surface, fits the data well. A higher ionization component is needed for Ne X absorption. The best-fit model is optically thin with $\log N_{\rm H }= 20.456 \pm 0.016$. The lines are non-saturated, and the CTP spectral fit aligns with previous analyses of Mrk 509 with a constant density WA. The model constrains the gas density, placing the WA cloud at 0.02 pc, consistent with the inner broad line region and the thickening region of the accretion disk.

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arXiv2025

Changing Look AGN: A study of Optical/UV and the Highly Ionized Fe K$α$ X-ray Line Flux Variations Using Photo-Ionization Simulations

Significant variability in broad emission line strengths of active galactic nuclei (AGN) over months to years has been observed, often accompanied by intrinsic continuum changes. Such spectral variability challenges the traditional AGN classification scheme, which attributes differences between Type 1 and Type 2 to geometrical effects, as transitions between these types occur on timescales shorter than viscous ones. In this work, using the {\sc cloudy} photo-ionization simulations, we investigated the response of the major emission line fluxes, in the optical/UV and hard X-ray bands, to changes in the intensity and shape of the continuum emission of the AGN under two scenarios: (i) changes in the X-ray power-law while keeping disc emission fixed, and (ii) broadband continuum variations. We demonstrate that BLR line fluxes are insensitive to X-ray power-law changes alone. Considering a well-studied case of the changing-look (CL) AGN Mrk 1018, which exhibits variations in the intrinsic disc emission, as well as the X-ray power-law, our simulations reproduce observed brightening and dimming trends of the BLR emission. Moreover, we show that the highly ionized Fe K$α$ X-ray flux, primarily produced by the H-like and He-like ions of Fe, strongly depends on the X-ray strength of the intrinsic SED. These findings suggest that the origin of highly ionized Fe K$α$ emission is in the coronal part of the accretion disk and that the CL phenomenon can be triggered by intrinsic changes in the accretion properties of AGN.

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arXiv2023

UV Fe II emission model of HE 0413-4031 and its relation to broad-line time delays

Fe II emission is a well-known contributor to the UV spectra of active galactic nuclei and the modeling of this part may affect the results obtained for the MgII$\lambda2800$ emission, which is one of the lines used for black hole mass measurements and cosmological applications. We use the 11-year monitoring of the selected quasar HE 0413-4031 with the South African Large Telescope (SALT) and we supplement this monitoring with the near-IR spectrum taken with the SOAR telescope. A new redshift determination ($z=1.39117 \pm 0.00017$) using [OIII]$λλ4959,5007$ gave a very different value than the previous determination based only on the UV FeII pseudocontinuum ($z=1.3764$). It favors a different decomposition of the spectrum into Mg II and UV Fe II emissions. The line characteristics and the time delay of the Mg II emission ($224^{+21}_{-23}$ days) are not significantly affected. However, in comparison with the previous analysis, the rest-frame UV FeII time delay ($251^{+9}_{-7}$ days) is consistent with the inferred UV FeII line FWHM of $4200\,{\rm km/s}$ that is only slightly smaller than the MgII line FWHM. Hence the FeII-emitting material is more distant than the MgII-emitting gas in HE 0413-4031 by $\sim 0.023$ pc (4700 AU). The inferred velocity shift of both Mg II and UV Fe II lines with respect to the systemic redshift is now rather low, below 300 km s$^{-1}$. In addition, we construct an updated MgII radius-luminosity ($R-L$) relation from 194 sources, which is more than double the previous sample. The MgII $R-L$ relation is flatter than the UV FeII, optical FeII, and H$β$ $R-L$ relations. While the new decomposition of the spectrum is satisfactory, we see a need to create better Fe II templates using the newest version of the code CLOUDY.

astro-ph.GA↗

arXiv2023

Covering factor in AGNs: evolution versus selection

In every proposed unification scheme for Active Galactic Nuclei (AGN), an integral element is the presence of circumnuclear dust arranged in torus-like structures. A crucial model parameter in this context is the covering factor (CF), defined as the ratio between the infrared luminosity of the dusty torus $L_{\rm IR}$, and the accretion disk bolometric luminosity $L_{\rm agn}$. Our study aims to determine whether CF evolution is genuine or if selection effects significantly influence it. Based on cross-matched multiwavelength photometrical data from the five major surveys (SDSS, GALEX, UKIDSS, WISE, SPITZER), a sample of almost 2,000 quasars was derived. The main parameters of quasars, such as black hole masses and the Eddington ratios, were calculated based on the spectroscopic data. The data were divided into two redshift bins: Low-$z$ (redshift ~1) and High-$z$ (redshift ~2) quasars. We identified an issue with the accuracy of the WISE W4 filter. Whenever feasible, it is recommended to utilize SPITZER MIPS 24 $μ$m data. The calculated median CF values for the highest quality SPITZER data are comparable within errors $\log$ CF$_{\textrm{low}-z} = -0.19\pm 0.11$ and $\log$ CF$_{\textrm{high}-z}= -0.18\pm 0.11$. The Efron & Petrosian test confirmed the presence of luminosity evolution with redshift for both $L_{\rm IR}$ and $L_{\rm agn}$. Both the Low-$z$ and High-$z$ samples exhibit a similar correlation between $L_{\rm agn}$ and $L_{\rm IR}$. No discernible evolution of the CF was observed in the subsample of quasars with high SMBH mass bin or high luminosities. The relationship between $L_{\rm IR}$ and $L_{\rm agn}$ deviates slightly from the expected 1:1 scaling. However, no statistically significant dependence of CF on luminosities could be claimed across the entire dataset.

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arXiv2022

Variable mass accretion and failed wind explain changing look phenomena in NGC 1365

Changing look active galactic nuclei (CLAGNs) show complex nature in their X-ray spectral shape and line of sight column density variation. The physical mechanisms responsible for these variations are unclear. Here, we study the spectral properties of a CLAGN, NGC\,1365 using combined {\it XMM-Newton} and {\it NuSTAR} observations to understand the CL behavior. The model fitted mass accretion rate varied between $0.003\pm 0.001$ and $0.009\pm0.002$ $\dot M_{\rm Edd}$ and the dynamic corona changed from $28\pm 3$ to $10\pm1$ $r_g$. We found that the variable absorption column density correlates with the mass accretion rate and the geometry of the corona. The derived wind velocity was sufficiently low compared to the escape velocity to drive the wind away from the disc for the epochs when column densities were high. This suggests that the high and variable absorption can be due to failed winds from the disc. Our estimated ratio of mass outflow to inflow rate from the inner region of the disc lies between $0.019\pm0.006$ and $0.12\pm0.04$. From spectral fitting of the combined data, we found the mass of the central black hole to be constant $4.38\pm0.34 - 4.51\pm0.29 \times10^{6} M_\odot$, consistent with earlier findings. The confidence contours of $N_H$ with other model parameters show that the model fitted parameters are robust and non-degenerate. Our study construed that the changing accretion rate, which is a fundamental physical quantity and the geometry of the corona driving the CL phenomena in NGC\,1365. The physical picture considered in this work connects both variable continuum and variable absorbing medium scenarios.

astro-ph.HE↗

arXiv2022

AGN in the ULIRG HE 0435-5304

HE 0435-5304 from Hamburg European Southern Observatory survey is a quasar that appears in the literature with two conflicting redshift values: $\sim 1.2$ and $\sim 0.4$. It was used in the studies of the intergalactic medium through fitting of the narrow absorption lines in its ultraviolet (UV) spectrum. This source is also known historically as a luminous infrared galaxy. We present optical spectra of HE 0435-5304, aiming to precisely measure its redshift and to study its physical properties. In particular, properties of its active nucleus, which is studied in the context of the source being identified here as an ultra-luminous infrared galaxy, allow us to place this quasar in the context of the general population. Fitting the spectra, we focused on modeling H$β$ and [O III] lines. Based on these, we derived the virial black hole mass, bolometric luminosity, and Eddington ratio of the active galactic nucleus (AGN). Additionally, we performed broad band photometry fitting which allows us to quantify host galaxy parameters. The improved redshift value of HE 0435-5304 is estimated to $0.42788 \pm 0.00027$ based on the [O II] line, which is mostly consistent with the narrowest components of the other emission lines. The source was found to be a relatively massive and luminous AGN whose host galaxy is actively forming stars. Although its stellar population seems to be heavily obscured, we did not find evidence for significant obscuration of the nucleus. We conclude that the AGN HE 0435-5304 is a rather prominent iron emitter from the extreme type-A population very close to the narrow-line Seyfert 1 group. The fact that the width of the H$β$ line appears to be systematically growing in its broadest component with time may suggest that this AGN is changing its broad line region. Due to the influence of atmospheric effects, this finding is uncertain.

astro-ph.GA↗

arXiv2021

Viewing angle observations and effects of evolution with redshift, black hole mass, and Eddington ratio in quasar based cosmology

This study is focused on the observational measurement of the viewing angle of individual quasars by modeling the broadband quasar spectrum ranging from the infra-red (IR) to the soft X-ray band. Sources are selected from various published catalogs, and their broadband quasi-simultaneous spectral data points were collected and used to model. We started with a COSMOS sample of type-1 sources which have broadband photometric points. Then, to include more data points, we cross-matched the COSMOS with the SDSS DR14 quasar catalog, and eventually, we find 90 sources that have broadband data ranging from IR to soft X-ray. The broadband spectral energy distribution (SED) modeling is done in Xspec by using the optxagnf and the SKIRTOR models for the X-ray, UV, Optical, and IR regimes for each source. The whole sample is divided into four bins with respect to redshift, black hole (BH) mass, and Eddington ratio with an equal number of sources in each bin. The viewing angle is estimated in each bin, and its evolution with respect to redshift, BH mass, and Eddington ratio is examined. As a result, we did not find any significant evolution of viewing angle with those parameters within the 95$\%$ confidence interval. We conclude that the use of quasars in cosmology to determine the expansion rate of the universe is therefore justified, and biases are not expected.

astro-ph.GA↗

arXiv2021

Time Delay of MgII Emission Response for the Luminous Quasar HE 0435-4312: Towards Application of High-Accretor Radius-Luminosity Relation in Cosmology

Using the six years of the spectroscopic monitoring of the luminous quasar HE 0435-4312 ($z=1.2231$) with the Southern African Large Telescope (SALT), in combination with the photometric data (CATALINA, OGLE, SALTICAM, and BMT), we determined the rest-frame time-delay of $296^{+13}_{-14}$ days between the MgII broad-line emission and the ionizing continuum using seven different time-delay inference methods. Artefact time-delay peaks and aliases were mitigated using the bootstrap method, prior weighting probability function as well as by analyzing unevenly sampled mock light curves. The MgII emission is considerably variable with the fractional variability of $\sim 5.4\%$, which is comparable to the continuum variability ($\sim 4.8\%$). Because of its high luminosity ($L_{3000}=10^{46.4}\,{\rm erg\,s^{-1}}$), the source is beneficial for a further reduction of the scatter along the MgII-based radius-luminosity relation and its extended versions, especially when the high-accreting subsample that has an RMS scatter of $\sim 0.2$ dex is considered. This opens up a possibility to use the high-accretor MgII-based radius-luminosity relation for constraining cosmological parameters. With the current sample of 27 reverberation-mapped sources, the best-fit cosmological parameters $(Ω_{\rm m}, Ω_Λ)=(0.19; 0.62)$ are consistent with the standard cosmological model within 1$σ$ confidence level.

astro-ph.GA↗

arXiv2020

Quasar main sequence in the UV plane

Active galaxies form a clear pattern in the optical plane showing the correlation between the Full Width Half Maximum (FWHM) of the H$β$ line and the ratio of the Equivalent Width (EW) of the optical FeII emission and the EW(H$β$). This pattern is frequently refereed to as the quasar main sequence. In this paper we study the UV plane showing FWHM of the MgII line against the ratio of EW of UV FeII emission to EW(MgII). We show that the UV plane trends are different, with the underlying strong correlation between FWHM(MgII) and EW(MgII). This correlation is entirely driven by the choice of the continuum used to measure EW(MgII). If we correct for the strong curvature in the UV continuum related to the character of emission expected from accretion disk, the behavior of the FWHM vs. EW for MgII becomes similar to the behaviour of H$β$. Such a similarity is expected since both lines belong to the Low Ionization group of emission lines and come from a similar region. Such a similarity and weak coupling between FWHM and EW of the corresponding line is then also consistent with the Broad Line Region model based on the presence of dust in the accretion disk atmosphere.

astro-ph.HE↗

arXiv2020

Long-term optical spectroscopic variations in blazar 3C 454.3

Characterisation of the long-term variations in the broad line region in a luminous blazar, where Comptonisation of broad-line emission within a relativistic jet is the standard scenario for production of gamma-ray emission that dominates the spectral energy distribution. We analysed ten years of optical spectroscopic data from the Steward Observatory for the blazar 3C 454.3, as well as gamma-ray data from the Fermi Large Area Telescope (LAT). The optical spectra are dominated by a highly variable non-thermal synchrotron continuum with a prominent Mg II broad emission line. The line flux was obtained by spectral decomposition including significant contribution from the Fe II pseudo-continuum. Three methods were used to characterise variations in the line flux: (1) stacking of the continuum-subtracted spectra, (2) subtracting the running mean light curves calculated for different timescales, and (3) evaluating potential time delays via the discrete correlation function (DCF). Despite very large variations in the gamma-ray and optical continua, the line flux changes only moderately (< 0.1 dex). The data suggest that the line flux responds to a dramatic change in the blazar activity from a very high state in 2010 to a deep low state in 2012. Two interpretations are possible: either the line flux is anti-correlated with the continuum or the increase in the line luminosity is delayed by ~600 days. If this time delay results from the reverberation of poorly constrained accretion disc emission in both the broad-line region (BLR) and the synchrotron emitting blazar zone within a relativistic jet, we would obtain natural estimates for the BLR radius [R_{BLR,MgII} >~ 0.28 pc] and for the supermassive black hole mass [M_SMBH ~ 8.5x10^8 M_sun]. We did not identify additional examples of short-term 'flares' of the line flux, in addition to the previously reported case observed in 2010.

astro-ph.HE↗

arXiv2020

Time-delay measurement of MgII broad line response for the highly-accreting quasar HE 0413-4031: Implications for the MgII-based radius-luminosity relation

We present the monitoring of the AGN continuum and MgII broad line emission for the quasar HE 0413-4031 ($z=1.38$) based on the six-year monitoring by the South African Large Telescope (SALT). We managed to estimate a time-delay of $302.6^{+28.7}_{-33.1}$ days in the rest frame of the source using seven different methods: interpolated cross-correlation function (ICCF), discrete correlation function (DCF), $z$-transformed DCF, JAVELIN, two estimators of data regularity (Von Neumann, Bartels), and $χ^2$ method. This time-delay is below the value expected from the standard radius-luminosity relation. However, based on the monochromatic luminosity of the source and the SED modelling, we interpret this departure as the shortening of the time-delay due to the higher accretion rate of the source, with the inferred Eddington ratio of $\sim 0.4$. The MgII line luminosity of HE 0413-4031 responds to the continuum variability as $L_{\rm line}\propto L_{\rm cont}^{0.43\pm 0.10}$, which is consistent with the light-travel distance of the location of MgII emission at $R_{\rm out} \sim 10^{18}\,{\rm cm}$. Using the data of 10 other quasars, we confirm the radius-luminosity relation for broad MgII line, which was previously determined for broad H$β$ line for lower-redshift sources. In addition, we detect a general departure of higher-accreting quasars from this relation in analogy to H$β$ sample. After the accretion-rate correction of the light-travel distance, the MgII-based radius-luminosity relation has a small scatter of only $0.10$ dex.

astro-ph.GA↗

arXiv2019

Time delay measurement of Mg II line in CTS C30.10 with SALT

We report 6 yr monitoring of a distant bright quasar CTS C30.10 (z = 0.90052) with the Southern African Large Telescope (SALT). We measured the rest-frame time-lag of $562\pm 2$ days between the continuum variations and the response of the Mg II emission line, using the Javelin approach. More conservative approach, based on five different methods, imply the time delay of $564^{+109}_{-71}$ days. This time delay, combined with other available measurements of Mg II line delay, mostly for lower redshift sources, shows that the Mg II line reverberation implies a radius-luminosity relation very similar to the one based on a more frequently studied H$β$ line.

astro-ph.GA↗

arXiv2018

Interpretation of Departure from the Broad Line Region Scaling in Active Galactic Nuclei

Most results of the reverberation monitoring of active galaxies showed a universal scaling of the time delay of the Hbeta emission region with the monochromatic flux at 5100 A, with very small dipersion. Such a scaling favored the dust-based formation mechanism of the Broad Line Region (BLR). Recent reverberation measurements showed that actually a significant fraction of objects exhibits horter lags than the previously found scaling. Here we demonstrate that these shorter lags can be explained by the old concept of scaling of the BLR size with the ionization parameter. Assuming a universal value of this parameter and universal value of the cloud density reproduces the distribution of observational points in the time delay vs. monochromatic flux plane, provided that a range of black hole spins is allowed. However, a confirmation of the new measurements for low/moderate Eddington ratio sources is strongly needed before the dust-based origin of the BLR can be excluded.

astro-ph.GA↗

arXiv2018

Modelling of the quasar main sequence in the optical plane

The concept of the quasar main sequence is very attractive since it stresses correlations between various parameters and implies the underlying simplicity. In the optical plane defined by the width of the H\{beta} line and the ratio of the equivalent width of the Fe II to H\{beta} observed objects form a characteristic pattern. In this paper, we use a physically motivated model to explain the distribution of quasars in the optical plane. Continuum is modelled as an accretion disk with a hard X-ray power law uniquely tight to the disk at the basis of observational scaling, and the Broad Line Region distance is determined also from observational scaling. We perform the computations of the FeII and H\{beta} line production with the code CLOUDY. We have only six free parameters for an individual source: maximum temperature of the accretion disk, Eddington ratio, cloud density, cloud column density, microturbulence, and iron abundance, and only the last four remain as global parameters in our modelling of the whole sequence. Our theoretically computed points cover well the optical plane part populated with the observed quasars, particularly if we allow for super-Solar abundance of heavy elements. Explanation of the exceptionally strong Fe II emitter requires a stronger contribution from the dark sides of the clouds. Analyzing the way how our model covers the optical plane we conclude that there is no single simple driver behind the sequence, as neither the Eddington ratio nor broad band spectrum shape plays the dominant role. Also, the role of the viewing angle in providing the dispersion of the quasar main sequence is apparently not as strong as expected.

astro-ph.HE↗

arXiv2017

Self-consistent dynamical model of the Broad Line Region

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.

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