Autorzy: Zajaček, Michal et al.

Czasopismo: Astronomy & Astrophysics, 2024, 683, id. A140

Context. FeII 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 λ2800 emission, which is one of the lines used for black hole mass measurements and cosmological applications. Aims: We tested different FeII emission models when modeling the UV emission of the intermediate-redshift quasar HE 0413−4031 to see how the use of a specific template affects the MgII λ2800 line properties and the measurement of the MgII λ2800 and UV FeII time delays with respect to the continuum. Methods: We used the 11-year monitoring of the selected quasar HE 0413−4031 with the South African Large Telescope (SALT), and we supplemented this monitoring with the near-IR spectrum taken with the SOAR telescope, which gave access to the Hβλ4861 and [OIII] λλ4959, 5007 emission lines at the rest frame and allowed for a precise measurement of the redshift. Results: A new redshift determination (z = 1.39117 ± 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 MgII and UV FeII emissions. The line characteristics and the time delay of the MgII emission (224−23+21 days) are not significantly affected. However, in comparison with the previous analysis, the rest-frame UV FeII time delay (251−7+9 days) is consistent with the inferred UV FeII line full width at half maximum (FWHM) of 4200 km s−1 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 ∼0.023 pc (4700 AU). The inferred velocity shift of both MgII and UV FeII lines with respect to the systemic redshift is now rather low, below 300 km s−1. In addition, we constructed 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 HβR − L relations. While the new decomposition of the spectrum is satisfactory, we see a need to create better FeII templates using the newest version of the code CLOUDY.

Pełen tekst pracy dostępny na stronie: https://www.aanda.org/articles/aa/pdf/2024/03/aa48172-23.pdf

Autorzy: Cao, Shulei; Zajaček, Michal ; Czerny, Bożena; Panda, Swayamtrupta ; Ratra, Bharat

Czasopismo: Monthly Notices of the Royal Astronomical Society, 2024, 528, pp.6444-6469

Previously, we demonstrated that Mg II and C IV reverberation-mapped quasars (RM QSOs) are standardizable and that the cosmological parameters inferred using the broad-line region radius-luminosity (R-L) relation are consistent with those determined from better-established cosmological probes. With more data expected from ongoing and future spectroscopic and photometric surveys, it is imperative to examine how new QSO data sets of varied quality, with their own specific luminosity and time-delay distributions, can be best used to determine more restrictive cosmological parameter constraints. In this study, we test the effect of adding 25 OzDES Mg II RM QSOs as well as 25 lower quality SDSS RM C IV QSOs, which increases the previous sample of RM QSOs by ∼36 per cent. Although cosmological parameter constraints become tighter for some cosmological models after adding these new QSOs, the new combined data sets have increased differences between R-L parameter values obtained in different cosmological models and thus a lower standardizability for the larger Mg II + C IV compilation. Different time-delay methodologies, particularly the ICCF and CREAM methods used for inferring time delays of SDSS RM QSOs, slightly affect cosmological and R-L relation parameter values, however, the effect is negligible for (smaller) compilations of robust time-delay detections. Our analysis indicates that increasing the sample size is not sufficient for tightening cosmological constraints and a quality cut is necessary to obtain a standardizable RM QSO sample.

Pełen tekst pracy dostępny na stronie: https://ui.adsabs.harvard.edu/abs/2024MNRAS.528.6444C/abstract

Autorzy: Pandey, Ashwani; Czerny, Bożena ; Panda, Swayamtrupta; Prince, Raj ; Jaiswal, Vikram Kumar ; Martinez-Aldama, Mary Loli ; Zajaček, Michal ; Śniegowska, Marzena

Czasopismo: Astronomy & Astrophysics, 2023, 680, id. A102

Context. Dust in active galactic nuclei is clearly present right outside the broad-line region (BLR) in the form of a dusty molecular torus. However, some models of the BLR predict that dust may also exist within the BLR. Aims: We study the reprocessing of radiation by the BLR with the aim of observing how the presence of dust affects the reprocessed continuum and the line properties. Methods: We calculated a range of models using the CLOUDY photoionisation code for dusty and dustless plasma. We paid particular attention to the well-studied object NGC 5548, and we compared the line equivalent width predictions with the data from observations for this object. Results: We obtained a rough agreement between the expected equivalent widths of the Hβ and Mg II lines and the observed values for NGC 5548 for the line distances implied by the time-delay measurement (for Hβ) and the radius-luminosity relation (for Mg II) when the medium is dusty. We found the incident radiation to be consistent with the radiation seen by the observer, so no shielding between the inner disc and the BLR is required. High ionisation lines such as He II, however, clearly form in the inner dustless region. When the additional absorber is present, the Hβ emitting region moves closer to the dustless part of the accretion disc surface.

Pełen tekst pracy dostępny na stronie: https://www.aanda.org/articles/aa/pdf/2023/12/aa47819-23.pdf

Autorzy: Prince, Raj ; Zajaček, Michal ; Panda, Swayamtrupta ; Hryniewicz, Krzysztof ; Kumar Jaiswal, Vikram ; Czerny, Bożena ; Trzcionkowski, Piotr ; Bronikowski, Mateusz ; Rałowski, Mateusz ; Sobrino Figaredo, Catalina ; Martinez-Aldama, Mary Loli ; Śniegowska, Marzena ; Średzińska, Justyna ; Bilicki, Maciej ; Naddaf, Mohammad-Hassan ; Pandey, Ashwani ; Haas, Martin ; Sarna, Marek Jacek ; Pietrzyński, Grzegorz ; Karas, Vladimir ; Olejak, Aleksandra ; Przyłuski, Robert ; Sefako, Ramotholo R. ; Genade, Anja ; Worters, Hannah L. ; Kozłowski, Szymon ; Udalski, Andrzej

Czasopismo: Astronomy & Astrophysics, 2023, 678, id.A189

Context. We present the wavelength-resolved reverberation mapping (RM) of combined Mg II and UV Fe II broad-line emissions for two intermediate-redshift (z ∼ 1), luminous quasars, HE 0413-4031 and HE 0435-4312, monitored by the Southern African Large Telescope (SALT) and 1m class telescopes between 2012 and 2022. Aims: Using a wavelength-resolved technique, we aim to disentangle the Mg II and Fe II emission regions and to build a radius-luminosity (R-L) relation for UV Fe II emission, which has so far remained unconstrained. Methods: We applied several time-delay methodologies to constrain the time delays for total Mg II and Fe II emissions. In addition, wavelength-resolved RM is performed to quantify the inflow or outflow of broad-line region (BLR) gas around the supermassive black hole and to disentangle the emission and the emitting regions based on lines produced in proximity to each other. Results: The mean total FeII time delay is nearly equal to the mean total MgII time delay for HE 0435-4312, suggesting the co-spatiality of their emission regions. However, in HE 0413-4031, the mean FeII time delay is found to be longer than the mean MgII time delay, suggesting that FeII emission is produced at greater distances from the black hole. The UV FeII R-L relation is updated with these two quasars (now four in total) and compared with the optical FeII relation (20 sources), which suggests that the optical FeII emission region is located further than the UV FeII region by a factor of 1.7-1.9, that is, RFeII-opt ∼ (1.7 − 1.9)RFeII-UV. Conclusion. Wavelength-resolved reverberation is an efficient way to constrain the geometry and structure of the BLR. We detected a weak pattern in the time delay versus wavelength relation, suggesting that the MgII broad line originates from a region slightly closer to the SMBH than the UV FeII pseudo continuum, although the difference is not very significant. Comparison of MgII, UV, and optical FeII R-L relations suggests that the difference may be greater for lower-luminosity sources, possibly with the MgII emission originating further from the SMBH. In the future, more RM data will be acquired, allowing better constraints on these trends, in particular the UV FeII R-L relation.

Pełen tekst pracy dostępny na stronie: https://www.aanda.org/articles/aa/pdf/2023/10/aa46738-23.pdf

Autorzy: Czerny, Bozena ; Panda, Swayamtrupta ; Prince, Raj ; Kumar Jaiswal, Vikram ; Zajaček, Michal ; Martinez Aldama, Mary Loli ; Kozłowski, Szymon ; Kovacevic, Andjelka B. ; Ilic, Dragana ; Popović, Luka Č. ; Pozo Nuñez, Francisco ; Hönig, Sebastian F. ; Brandt, William N.

Czasopismo: Astronomy & Astrophysics, 2023, 675, id.A163

Context. The Vera Rubin Observatory will provide an unprecedented set of time-dependent observations of the sky. The planned Legacy Survey of Space and Time (LSST), operating for ten years, will provide dense light curves for thousands of active galactic nuclei (AGN) in deep drilling fields (DDFs) and less dense light curves for millions of AGN from the main survey (MS). Aims: We model the prospects for measuring the time delays for the AGN emission lines with respect to the continuum, using these data. Methods: We modeled the artificial light curves using the Timmer-König algorithm. We used the exemplary cadence to sample them (one for the MS and one for the DDF), we supplement light curves with the expected contamination by the strong emission lines (Hβ, Mg II, and CIV, as well as with Fe II pseudo-continuum and the starlight). We chose suitable photometric bands that are appropriate for the redshift and compared the assumed line time-delay with the recovered time delay for 100 statistical realizations of the light curves. Results: We show that time delays for emission lines can be well measured from the main survey for the bright tail of the quasar distribution (about 15% of all sources) with an accuracy within 1σ error. For the DDF, the results for fainter quasars are also reliable when the entire ten years of data are used. There are also some prospects to measure the time delays for the faintest quasars at the lowest redshifts from the first two years of data, and possibly even from the first season. The entire quasar population will allow us to obtain results of apparently high accuracy, but in our simulations, we see a systematic offset between the assumed and recovered time delay that depends on the redshift and source luminosity. This offset will not disappear even in the case of large statistics. This problem might affect the slope of the radius-luminosity relation and cosmological applications of quasars if no simulations are performed that correct for these effects.

Pełen tekst pracy dostępny na stronie: https://www.aanda.org/articles/aa/pdf/2023/07/aa45844-23.pdf

Autorzy: Czerny, Bożena; Zajaček, Michal ; Naddaf, Mohammad-Hassan ; Sniegowska, Marzena ; Panda, Swayamtrupta ; Różanska, Agata ; Adhikari, Tek P. ; Pandey, Ashwani; Jaiswal, Vikram Kumar ; Karas, Vladimír ; Borkar, Abhijeet; Martínez-Aldama, Mary Loli ; Prince, Raj

Czasopismo: The European Physical Journal D, 2023, 77, id.56

For many years we have known that dust in the form of a dusty-molecular torus is responsible for the obscuration in active galactic nuclei (AGN) at large viewing angles and, thus, for the widely used phenomenological classification of AGN. Recently, we gained new observational and theoretical insights into the geometry of the torus region and the role of dust in the dynamics of emerging outflows and failed winds. We will briefly touch on all these aspects and provide a more detailed update of our dust-based model (FRADO—Failed Radiatively Accelerated Dusty Outflow) capable of explaining the processes of formation of Balmer lines in AGN.

Pełen tekst pracy dostępny na stronie: https://link.springer.com/article/10.1140/epjd/s10053-023-00630-8

Autorzy: Czerny, Bożena ; Cao, Shulei ; Jaiswal, Vikram Kumar ; Karas, Vladimír ; Khadka, Narayan ; Martínez-Aldama, Mary Loli ; Naddaf, Mohammad Hassan ; Panda, Swayamtrupta; Pozo Nuñez, Francisco ; Prince, Raj ; Ratra, Bharat ; Śniegowska, Marzena ; Yu, Zhefu ; Zajaček, Michal

Czasopismo: Astrophysics and Space Science, 2023, 368, id.8

As Setti and Woltjer noted back in 1973, one can use quasars to construct the Hubble diagram; however, the actual application of the idea was not that straightforward. It took years to implement the proposition successfully. Most ways to employ quasars for cosmology now require an advanced understanding of their structure, step by step. We briefly review this progress, with unavoidable personal biases, and concentrate on bright unobscured sources. We will mention the problem of the gas flow character close to the innermost stable circular orbit near the black hole, as discussed five decades ago. This problem later led to the development of the slim disk scenario and is recently revived in the context of Magnetically Arrested Disks (MAD) and Standard and Normal Evolution (SANE) models. We also discuss the hot or warm corona issue, which is still under debate and complicates the analysis of X-ray reflection. We present the scenario of the formation of the low ionization part of the Broad Line Region as a failed wind powered by radiation pressure acting on dust (Failed Radiatively Driven Dusty Outflow – FRADO). Next, we examine the cosmological constraints currently achievable with quasars, primarily concentrating on light echo methods (continuum time delays and spectral-line time delays to the continuum) that are (or should be) incorporating the progress mentioned above. Finally, we briefly discuss prospects in this lively subject area.

Pełen tekst pracy dostępny na stronie: https://link.springer.com/article/10.1007/s10509-023-04165-7