arXiv subjects

Marcin Marculewicz

Publications and source records attributed to Marcin Marculewicz.

9 recordsLinked to original sources

arXiv2026

The unusually red delay spectrum of the low-mass black hole AGN NGC\,4051 as revealed by intensive continuum reverberation mapping with the Las Cumbres Observatory

We present a two-year optical reverberation mapping campaign of NGC 4051, an active galactic nucleus (AGN) hosting a low-mass black hole ($8\times10^5 M_\odot$), using daily observations in seven photometric bands from Las Cumbres Observatory augmented by archival data from Swift XRT and UVOT. The light curves show correlated variability with wavelength-dependent lags broadly consistent with the standard accretion disc scaling, $τ\propto λ^{4/3}$, and a pronounced u-band excess. However, the $i$ and $z_s$ lags are significantly larger than expected and cannot be explained by a combination of disc emission and diffuse continuum (DC) from the broad-line region (BLR), making NGC 4051 a notable lag-luminosity outlier. The spectral energy distribution (SED) of the variable AGN component is markedly redder than the canonical accretion disc prediction, $F_ν\propto ν^{1/3}$, typically observed in more massive systems. We explore two scenarios to account for the red UV-optical SED and the anomalously large $i$ and $z_s$ lags: (a) SMC-like dust reddening ($E(B-V)\sim0.18$) combined with optically thick emission from the inner edge of the dusty torus; and (b) a dominant diffuse continuum contribution. We discuss the implications of each scenario within a comprehensive multi-wavelength framework.

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arXiv2025

Predicting Quasar Counts Detectable in the LSST Survey

The Legacy Survey of Space and Time (LSST), being conducted by the Vera C. Rubin Observatory, is a wide-field multi-band survey that will revolutionize our understanding of extragalactic sources through its unprecedented combination of area and depth. While the LSST survey strategy is still being finalized, the Rubin Observatory team has generated a series of survey simulations using the LSST Operations Simulator to explore the optimal survey strategy that best accommodates the majority of scientific goals. In this study, we utilize the latest simulated data to predict the number of detectable quasars by LSST in each band and evaluate the impact of different survey strategies. We find that the number of quasars and lower luminosity AGNs detected in the baseline strategy (v4.3.1) in the redshift range z=0.3-6.7 will be highest in the i-band and lowest in the u-band. Over 70% of quasars are expected to be detected within the first year in all bands, as LSST will have already reached the break of the luminosity function at most redshifts. With a limiting magnitude of 25.7 mag, we expect to detect 184 million AGNs in the z-band over the 10-year survey, with quasars constituting only 6% of the total AGNs in each band. This arises because, considering that the luminosities of most low-luminosity AGNs are affected by contamination from their host galaxies, we set a magnitude threshold when predicting the number of quasars. We find that variations in the u-band strategy can impact the number of quasar detections. Specifically, the difference between the baseline strategy and that with the largest total exposure in u is 15%. In contrast, changes in rolling strategies, DDF strategies, weather conditions, and Target of Opportunity observations result in variations below 2%. These results provide valuable insights for optimizing approaches to maximize the scientific output of quasar studies.

astro-ph.GA↗

arXiv2025

Scalable and Robust Multiband Modeling of AGN Light Curves in Rubin-LSST

The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will monitor tens of millions of active galactic nuclei (AGNs) for a period of 10 years with an average cadence of 3 days in six broad photometric bands. This unprecedented dataset will enable robust characterizations of AGN UV/optical variability across a wide range of AGN physical properties. However, existing tools for modeling AGN light curves are not yet capable of fully leveraging the volume, cadence, and multiband nature of LSST data. We present EzTaoX, a scalable light curve modeling tool designed to take advantage of LSST's multiband observations to simultaneously characterize AGN UV/optical stochastic variability and measure interband time delays. EzTaoX achieves a speed increase of $\sim 10^2-10^4 \times$ on CPUs over current tools with similar capabilities, while maintaining equal or better accuracy in recovering simulated variability properties. This performance gain enables continuum time-delay measurements for all AGNs discovered by LSST -- both in the Wide Fast Deep survey and the Deep Drilling Fields -- thereby opening new opportunities to probe AGN accretion-flow geometries. In addition, EzTaoX's multiband capability allows robust characterization of AGN stochastic variability down to hourly timescales, facilitating the identification of accreting low-mass AGNs -- such as those residing in dwarf galaxies -- through their distinctive variability signatures.

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arXiv2025

Unprecedented Continuum Time Delay Variation Phenomenon in an Active Supermassive Black Hole

Resolving the accretion disks and broad line regions (BLRs) of active galactic nuclei (AGNs) can probe the physics behind supermassive black holes (SMBHs) fueling and weigh SMBHs. With time-domain observations, the reverberation mapping (RM) technique measures time delays between different light curves, probing the AGN inner structures that are otherwise often too compact to resolve spatially with current facilities. Theoretically, the SMBH accretion disk structure does not evolve over decades. Here we report the significant variations in the continuum time delays of NGC 4151. In the high-flux state, our high-cadence ($\sim 2$ days) spectroscopy reveals that continuum time delays are $3.8^{+1.8}_{-1.0}$ times larger than those in the low-flux state and $14.9\pm 2.0$ times longer than the classical standard thin disk prediction. Notably, the continuum time delays can be comparable with the time delay between H$β$ and the $5100\ \mathrmÅ$ continuum, and the latter is commonly used to calculate the BLR sizes. Hence, the BLR sizes are underestimated if the continuum time delays are not considered, which introduces $\sim 0.3$ dex systematic uncertainties on RM SMBH masses. Our findings underscore that simultaneous continuum and BLR RMs are vital for better deciphering the SMBH accretion and mass function.

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arXiv2024

The disk reverberation mapping of the lensed quasar Q0957+561

The measurement of continuum time lags in lensed quasars can effectively probe the accretion physics of quasars. This is because microlensing observations of lensed quasars can provide constraints on the half-light radii of quasar accretion disks. By combining the microlensing results with time lag measurements, one can, for the first time, estimate the propagation velocity of the physical process that drives inter-band time lags and cross-correlations among disk emission (i.e. in UV/optical bands). In this study, we perform the disk reverberation mapping study for the well-studied lensed quasar, Q0957+561. The cross-correlation between the Zwicky Transient Facility (ZTF) $g$ and $r$ bands was measured; the $g$ variations lead the $r$ ones by $6.4\pm 2.6$ days in the rest frame. In combination with the half-light radius from the existing literature, we find that the propagation velocity of the variability mechanism should be $1.7^{+1.5}_{-0.7}$ times the speed of light. We discuss the possible outcomes of this result. Similar studies can be applied to other lensed quasars by utilizing the Legacy Survey of Space and Time (LSST) observations.

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arXiv2023

The disk reverberation mapping of X-ray weak quasars: a case study of SDSS J153913.47+395423.4

The widely adopted ``lamppost'' thermal reprocessing model, in which the variable UV/optical emission is a result of the accretion disk reprocessing of the highly fluctuating X-ray emission, can be tested by measuring inter-band time lags in quasars spanning a range of X-ray power. This work reports the inter-band time lag in an apparently X-ray weak quasar, SDSS J153913.47+395423.4. A significant cross-correlation with a time delay of $\sim 33$ days (observed-frame) is detected in the Zwicky Transient Facility (ZTF) $g$ and $r$ light curves of SDSS J153913.47+395423.4. The observed X-ray power seems to be too weak to account for the observed inter-band cross-correlation with time delay. Hence the X-ray weak quasar SDSS J153913.47+395423.4 is either intrinsically X-ray normal (but observationally X-ray weak), or the X-ray emission is not the only mechanism to drive UV/optical variability. In the former case, the required X-ray power is at least 19 times stronger than observed, which requires either an exceptionally anisotropic corona or Compton-thick obscuration. Alternatively, the Corona-heated Accretion disk Reprocessing (CHAR) or the EUV torus models may account for the observed time lags.

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arXiv2022

Global parameters of Quasars with anomalous electromagnetic spectrum

The thesis concerns the analysis of the Active Galactic Nuclei. These are galaxies with an active core. The most luminous type of Active Galactic Nuclei is Quasar. It contains the supermassive black hole at the center. One of the least known subtype of Quasars are: Weak emission-Line Quasars. Their recognizable feature are weak emission-lines. The primary goal of PhD thesis is to evaluate the global parameters such as: the black hole mass, the accretion rate, spin of the black hole, and the inclination of weak emission-line quasars based on the continuum fit method. This method apart from the literature black hole masses estimation methods does not depend on the observed Full Width at Half Maximum of emission line, which could be biased due to the weakness or lack of the emission lines in these quasars. Using the Spectral Energy Distribution of quasars, I have fitted the geometrically thin and optically thick accretion disk model described by Novikov \& Thorne equations. I have obtained the model of the continuum of the accretion disk for the 10 weak emission-line quasars. The second project concerned the description of abnormal, deep absorption of SDSS J110511.15+530806.5 quasar. I checked the correctness of the thesis posed that corona and warm skin concept above/around an accretion disk explain this phenomenon.

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arXiv2022

Deep absorption in SDSS J110511.15+530806.5

We study the origin of the anomalous deep absorption in a spectrum of the SDSS J110511.15+530806.5 distant quasar (z=1.929) obtained by the Sloan Digital Sky Survey in Data Release 7 of the optical catalog. We aim to estimate the velocity of absorbing material, and we show that this material considerably affects our measurements of the black hole (BH) mass in massive quasars with the use of common virial mass estimators. The spectral shape of the quasar was modeled assuming that the accretion disk emission is influenced by a hot corona, warm skin, and absorbing material located close to the nucleus. The whole analysis was undertaken with XSPEC models and tools. The overall spectral shape was represented with the AGNSED model, while the deep absorption is well described by two Gaussians. The observed spectrum and the fitting procedure allowed us to estimate the BH mass in the quasar as $3.52 \pm 0.01 \times 10^9 M_{\odot}$, the nonzero BH spin is $a_* = 0.32 \pm 0.04$, and the accretion rate is $\dot m=0.274 \pm 0.001$. The velocities of the detected absorbers lie in the range of 6330-108135 km/s. When we consider that absorption is caused by the CIV ion, one absorber is folding toward the nucleus with a velocity of 73887 km/s. We derived a BI index of about 20300 km/s and a mass outflow rate up to 38.5 % of the source accretion rate. The high absorption observed in SDSS J110511.15+530806.5 is evidence of fast winds that place the source in the group of objects on the border with UFO (ultra-fast outflows), strong broad absorption line (BAL), and fast failed radiatively accelerated dusty outflow (FRADO). This absorption affects the BH mass measurement by two orders of magnitude as compared to virial mass estimation.

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arXiv2020

Black hole masses of weak emission line quasars based on continuum fit method

We studied optical-ultraviolet spectral energy distribution of 10 weak emission-line quasars (WLQs) which lie at redshifts z = 0.19 and 1.43 < z < 3.48. The theoretical models of their accretion disk continua are created based on the Novikov-Thorne equations. It allows us to estimate masses of their supermassive black holes (MBH) and accretion rates. We determined the virial factor for WLQs and note its anti-correlation with the full width at half maximum (FWHM) of Hbeta emission-line (f propto FWHM^(alpha), alpha = (-1.34 +/- 0.37)). By comparison with the previously estimated BH masses, the underestimation of MBH is noticed with a mean factor 4-5 which depends on the measured full width. We proposed the new formula to estimate MBH in WLQs based on their observed FWHM (H beta) and luminosities at 5100 A. In our opinion, WLQs are also normal quasars visible in a reactivation stage.

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