Search

Contamination from singly ionized iron emission is one of the greatest obstacles to determining the intensity of emission lines in the UV and optical wavelength ranges. This study presents a comprehensive analysis of the FeII emission in the bright quasar RM 102, based on the most recent version of the CLOUDY software, with the goal of simultaneously reproducing UV and optical FeII emission. We employ a constant pressure model for the emitting clouds, instead of the customary constant density assumption. The allowed parameter range is broad, with metallicity up to 50 times the solar value and turbulent velocity up to 100 km s$^{-1}$ for a subset of models. We also consider geometrical effects that could enhance the visibility of the non-illuminated faces of the clouds, as well as additional mechanical heating. Our investigation reveals that the broad line region of RM 102 is characterized by highly metallic gas. The observed FeII features provide strong evidence for an inflow pattern geometry that favours the dark sides of clouds over isotropic emission. This study confirms the presence of chemically enriched gas in the broad line region of bright quasars, represented by RM 102, which is necessary to explain the strong FeII emission and its characteristic features. Additionally, we report that CLOUDY currently still lacks certain transitions in its atomic databases which prevents it from fully reproducing some observed FeII features in quasar spectra.

The Southern Photometric Local Universe Survey (S-PLUS) is a project to map $\sim9300$ sq deg of the sky using twelve bands (seven narrow and five broadbands). Observations are performed with the T80-South telescope, a robotic telescope located at the Cerro Tololo Observatory in Chile. The survey footprint consists of several large contiguous areas, including fields at high and low galactic latitudes, and towards the Magellanic Clouds. S-PLUS uses fixed exposure times to reach point source depths of about $21$ mag in the $griz$ and $20$ mag in the $u$ and the narrow filters. This paper describes the S-PLUS Data Release 4 (DR4), which includes calibrated images and derived catalogues for over 3000 sq deg, covering the aforementioned area. The catalogues provide multi-band photometry performed with the tools \texttt{DoPHOT} and \texttt{SExtractor} -- point spread function (\PSF) and aperture photometry, respectively. In addition to the characterization, we also present the scientific potential of the data. We use statistical tools to present and compare the photometry obtained through different methods. Overall we find good agreement between the different methods, with a slight systematic offset of 0.05\,mag between our \PSF and aperture photometry. We show that the astrometry accuracy is equivalent to that obtained in previous S-PLUS data releases, even in very crowded fields where photometric extraction is challenging. The depths of main survey (MS) photometry for a minimum signal-to-noise ratio $S/N = 3$ reach from $\sim19.5$ for the bluer bands to $\sim21.5$ mag on the red. The range of magnitudes over which accurate \PSF photometry is obtained is shallower, reaching $\sim19$ to $\sim20.5$ mag depending on the filter. Based on these photometric data, we provide star-galaxy-quasar classification and photometric redshift for millions of objects., Comment: 26 pages, 17 figures, 14 tables, accepted for A&A

The gamma-ray emitting narrow-line Seyfert 1 galaxies are a unique class of objects that launch powerful jets from relatively lower-mass black hole systems compared to the Blazars. However, the black hole masses estimated from the total flux spectrum suffer from the projection effect, making the mass measurement highly uncertain. The polarized spectrum provides a unique view of the central engine through scattered light. We performed spectro-polarimetric observations of the gamma-ray emitting narrow-line Seyfert 1 galaxy 1H0323+342 using SPOL/MMT. The degree of polarization and polarization angle is 0.122 $\pm$ 0.040 % and 142 $\pm$ 9 degrees, while the H$\alpha$ line is polarized at 0.265 $\pm$ 0.280 %. We decomposed the total flux spectrum and estimated broad H$\alpha$ FWHM of 1015 km/s. The polarized flux spectrum shows a broadening similar to the total flux spectrum, with a broadening ratio of 1.22. The Monte Carlo radiative transfer code `STOKES' applied to the data provides the best fit for a small viewing angle of 9-24 degrees and a small optical depth ratio between the polar and the equatorial scatters. A thick BLR with significant scale height can explain a similar broadening of the polarized spectrum compared to the total flux spectrum with a small viewing angle., Comment: Accepted for publication in MNRAS (Jul. 08th, 2024). 12 pages, 6 figures

Compact groups (CGs) of galaxies are extreme environments for morphological transformations and the cessation of star formation. Our objective is to understand the dynamics of CGs and how their surrounding environment impacts galaxy properties. We selected a sample of 340 CGs in the Stripe 82 region, totaling 1083 galaxies, and a control sample of 2281 field galaxies. We find that at least 27\% of our sample of CGs are part of major structures, i.e. non-isolated CGs. We find a bimodality in the effective radius ($R_e$)-S\'ersic index ($n$) plane for all transition galaxies (those with $(u-r) > 2.3$ and $n<2.5$) in CGs. Additionally, transition galaxies in isolated CGs populate more densely the $R_e-n$ plane for $n < 1.75$. In contrast, transition galaxies in non-isolated CGs have smoothly increasing $n$ values, suggesting these galaxies have already suffered morphological transformation, and primarily contribute to the distribution of more compact galaxies in the $R_e-n$ plane for all transition galaxies in CGs. We also find significant differences in the specific star-formation rate (sSFR) distribution between the late-type galaxies (LTGs) ($(u-r)<2.3$ and $n< 2.5$) in non-isolated CGs and the same type of galaxies in the control sample, suggesting that the evolution of LTGs differs in non-isolated CGs. Early-type galaxies ($(u-r)>2.3$ and $n>2.5$) and transition galaxies in non-isolated CGs have lower sSFR values and a higher fraction of quenched galaxies, compared to those in isolated CGs. Based on our results, we propose an evolutionary scenario where the major structures in which the CGs are embedded accelerate the morphological transformations of their members. Our findings highlight the importance of considering the larger structures in which CGs may be located, when analysing the properties of their galaxy, as this can significantly affect the evolution of CGs and their galaxies., Comment: Submitted to A&A, 13 pages, 9 figures

Reverberation mapping accurately determines virial black hole masses only for redshifts $z <$ 0.2 by utilizing the relationship between the H$\beta$ broad-line region (BLR) size and the 5100 Angstroms continuum luminosity established with $\sim 200$ active galactic nuclei (AGN). For quasars at $z \sim 2-3$ determining the BLR size is time-consuming and limited by seasonal gaps, requiring e.g., $\sim$ 20 years of monitoring of the CIV emission lines. In this work, we demonstrate that an efficient alternative is to use a continuum size-luminosity relation, which can be obtained up to 150 times faster than BLR sizes using photometric reverberation mapping (PRM). We outline the method and its feasibility based on simulations and propose an observational strategy that can be carried out with meter-class telescopes. In particular, we focus on the ESO La Silla 2.2 meter telescope as it is suitable for an efficient PRM campaign. These observations will provide the scaling factor between the accretion disk and the BLR size (for CIV-1350 Angstroms), which is crucial for estimating the masses of black holes at higher redshifts ($z \gtrsim 2-3$)., Comment: 12 pages, 5 figures, accepted to the Astrophysical Journal Letters

We use near-infrared (NIR) spectroscopy covering simultaneously the $zJHK$ bands to look for outflowing gas from the nuclear environment of 1H0707-495 taking advantage that this region is dominated by low-ionization broad line region (BLR) lines, most of them isolated. We detect broad components in HI, FeII and OI, at rest to the systemic velocity, displaying full width at half maximum (FWHM) values of ~500 km s$^{-1}$, consistent with its classification as a narrow-line Seyfert~1 AGN. Moreover, most lines display a conspicuous blue-asymmetric profile, modeled using a blueshifted component, whose velocity shift reaches up to ~826 km s$^{-1}$. This last feature can be interpreted in terms of outflowing gas already observed in X-ray and UV lines in 1H0707-495 but not detected before in the low-ionization lines. We discuss the relevance of our findings within the framework of the wind scenario already proposed for this source and suggest that the wind extends well into the narrow line region due to the observation of a blueshifted component in the forbidden line of [SIII] $\lambda$9531., Comment: 21 pages, 11 figures. Accepted to The Astronomical Journal

We use the spectroscopic data collected by the Magellanic Quasars Survey (MQS) as well as the photometric V- and I-band data from the Optical Gravitational Lensing Experiment (OGLE) to measure the physical parameters for active galactic nuclei (AGNs) located behind the Magellanic Clouds. The flux-uncalibrated MQS spectra were obtained with the 4-m Anglo-Australian Telescope and the AAOmega spectroscope (R=1300) in a typical ~1.5-hour visit. They span a spectral range of 3700-8500 Angstroms and have S/N ratios in a range of 3-300. We report the discovery and observational properties of 161 AGNs in this footprint, which expands the total number of spectroscopically confirmed AGNs by MQS to 919. After converting the OGLE mean magnitudes to the monochromatic luminosities at 5100 Angstroms, 3000 Angstroms, and 1350 Angstroms, we reliably measured the black hole masses for 165 out of 919 AGNs. The remaining physical parameters we provide are the bolometric luminosities and the Eddington ratios. A fraction of these AGNs have been observed by the OGLE survey since 1997 (all of them since 2001), enabling studies of correlations between their variability and physical parameters., Comment: 15 pages, 8 figures, 8 tables, accepted for publication in The Astrophysical Journal Supplement Series

The Wide-field Spectroscopic Telescope (WST) is proposed as a new facility dedicated to the efficient delivery of spectroscopic surveys. This white paper summarises the initial concept as well as the corresponding science cases. WST will feature simultaneous operation of a large field-of-view (3 sq. degree), a high multiplex (20,000) multi-object spectrograph (MOS) and a giant 3x3 sq. arcmin integral field spectrograph (IFS). In scientific capability these requirements place WST far ahead of existing and planned facilities. Given the current investment in deep imaging surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work synergistically with future ground and space-based facilities. This white paper shows that WST can address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; origin of stars and planets; time domain and multi-messenger astrophysics. WST's uniquely rich dataset will deliver unforeseen discoveries in many of these areas. The WST Science Team (already including more than 500 scientists worldwide) is open to the all astronomical community. To register in the WST Science Team please visit https://www.wstelescope.com/for-scientists/participate, Comment: 194 pages, 66 figures. Comments are welcome (wstelescope@gmail.com)

We present a set of new theoretical Fe II templates for bright quasars covering a wavelength range of 1000-10000 \AA, based on the recent atomic database available in the C23.00 version of the photoionization code CLOUDY. We compute a grid of models for a range of incident photon flux and gas density and for multiple microturbulence velocities. We analyze the ratios of Fe II emission over a variety of wavebands and compare them with observations. Our key results are: (1) Despite the use of the newest atomic data we still confirm the long-standing problem that the predicted Fe II UV/optical ratio is significantly larger than that observed in the AGN spectra. (2) The ratio is not significantly affected by the variations in the microturbulence and the metallicity. (3) The turbulence can create an additional apparent velocity shift of up to 1000 km/s in the spectra. (4) There is no single Fe II template that can fit the observational data covering UV to optical wavelength range. We shortly discuss the most likely effects responsible for the Fe II UV/optical mismatch problem: the assumption of the constant column density and the assumption of the isotropic emission implying equal contribution of the bright irradiated faces and the dark shielded faces of the clouds., Comment: 21 pages, 16 figures, 4 tables, submited to the Astrophysical Journal Supplement (ApJS) series

Constraining the physical conditions of the ionized media in the vicinity of an active supermassive black hole (SMBH) is crucial to understanding how these complex systems operate. Metal emission lines such as iron (Fe) are useful probes to trace the gaseous media's abundance, activity, and evolution in these accreting systems. Among these, the FeII emission has been the focus of many prior studies to investigate the energetics, kinematics, and composition of the broad-emission line region (BELR) from where these emission lines are produced. In this work, we present the first simultaneous FeII modeling in the optical and near-infrared (NIR) regions. We use CLOUDY photoionization code to simulate both spectral regions in the wavelength interval 4000-12000 Angstroms. We compare our model predictions with the observed line flux ratios for IZw1 - a prototypical strong FeII-emitting active galactic nuclei (AGN). This allows putting constraints on the BLR cloud density and metal content that is optimal for the production of the FeII emission, which can be extended to IZw1-like sources, by examining a broad parameter space. We demonstrate the salient and distinct features of the FeII pseudo-continuum in the optical and NIR, giving special attention to the effect of micro-turbulence on the intensity of the FeII emission., Comment: 17 pages, 6 figures, 1 table, accepted in MDPI Physics

The 4D Eigenvector 1 sequence has proven to be a highly effective tool for organizing observational and physical properties of type 1 active galactic nuclei (AGN). In this paper, we present multiple measurements of metallicity for the broad line region gas, from new or previously published data. We demonstrate a consistent trend along the optical plane of the E1 (also known as the quasar main sequence), defined by the line width of H$\beta$ and by a parameter measuring the prominence of singly-ionized iron emission. The trend involves an increase from sub-solar metallicity in correspondence with extreme Population B (weak FeII emission, large H$\beta$ FWHM) to metallicity several tens the solar value in correspondence with extreme Population A (very strong FeII optical emission, narrower H$\beta$ profiles). The data establish the metallicity as a correlate of the 4D E1/main sequence. If the very high metallicity gas ($Z \gtrsim 10 Z_\odot$) is expelled from the sphere of influence of the central black hole, as indicated by the widespread evidence of nuclear outflows and disk wind in the case of sources radiating at high Eddington ratio, then it is possible that the outflows from quasars played a role in chemically enriching the host galaxy., Comment: Submitted to Physics

The investigation of emission line regions within active galaxies (AGNs) has a rich and extensive history, now extending to the use of AGNs and quasars as "standardizable" cosmological indicators, shedding light on the evolution of our universe. As we enter the era of advanced observatories, such as the successful launch of JWST and the forthcoming Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), the landscape of AGN exploration across cosmic epochs is poised for exciting advancements. In this work, we delve into recent developments in AGN variability research, anticipating the substantial influx of data facilitated by LSST. The article highlights recent strides made by the AGN Polish Consortium in their contributions to LSST. The piece emphasizes the role of quasars in cosmology, dissecting the intricacies of their calibration as standard candles. The primary focus centers on the relationship between the broad-line region size and luminosity, showcasing recent breakthroughs that enhance our comprehension of this correlation. These breakthroughs encompass a range of perspectives, including spectroscopic analyses, photoionization modeling, and collaborative investigations with other cosmological tools. The study further touches on select studies, underlining how the synergy of theoretical insights and advancements in observational capabilities has yielded deeper insights into these captivating cosmic entities., Comment: 34 pages, 5 figures, accepted for publication as a review in MDPI/Universe

When a galaxy falls into a cluster, its outermost parts are the most affected by the environment. In this paper, we are interested in studying the influence of a dense environment on different galaxy's components to better understand how this affects the evolution of galaxies. We use, as laboratory for this study, the Hydra cluster which is close to virialization; yet it still shows evidence of substructures. We present a multi-wavelength bulge-disc decomposition performed simultaneously in 12 bands from S-PLUS data for 52 galaxies brighter than m$_{r}$= 16. We model the galaxies with a Sersic profile for the bulge and an exponential profile for the disc. We find that the smaller, more compact, and bulge-dominated galaxies tend to exhibit a redder colour at a fixed stellar mass. This suggests that the same mechanisms (ram-pressure stripping and tidal stripping) that are causing the compaction in these galaxies are also causing them to stop forming stars. The bulge size is unrelated to the galaxy's stellar mass, while the disc size increases with greater stellar mass, indicating the dominant role of the disc in the overall galaxy mass-size relation found. Furthermore, our analysis of the environment unveils that quenched galaxies are prevalent in regions likely associated with substructures. However, these areas also harbour a minority of star-forming galaxies, primarily resulting from galaxy interactions. Lastly, we find that ~37 percent of the galaxies exhibit bulges that are bluer than their discs, indicative of an outside-in quenching process in this type of dense environments., Comment: 17 pages, 19 figures. Submitted to the MNRAS

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 H$\beta$ and Mg II lines and the observed values for NGC 5548 for the line distances implied by the time-delay measurement (for H$\beta)$ 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 H$\beta$ emitting region moves closer to the dustless part of the accretion disc surface., Comment: 10 pages, 7 figures, 1 table, accepted for publication in the Astronomy and Astrophysics journal

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]$\lambda \lambda 4959,5007$ 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$\beta$ $R-L$ 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., Comment: 19 pages, 12+8 Figures, 5+1 Tables (Main Text+Appendix); accepted by A&A; minor corrections applied

Previously, we demonstrated that MgII and CIV 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 MgII RM QSOs as well as 25 lower-quality SDSS RM CIV QSOs, which increases the previous sample of RM QSOs by $\sim 36\%$. 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 MgII + CIV 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., Comment: 25 pages, 14 figures, 6 tables; accepted by the MNRAS Main Journal

Emission-line studies in the active galactic nuclei (AGNs), particularly those utilizing high spatial resolution, provide the most accurate method to determine critical quantities of the central engine and of the gas a few tens of parsecs away. Using seeing-limited data with spectroscopy, we have explored the extended narrow-line region for a sample of active galactic nuclei (AGNs) with strong, forbidden emission lines that have high-ionization potentials (IP $\gtrsim$ 100 eV). We have studied the optical and near-infrared spectra for these AGNs, extracted and compared their spectral energy distributions, and put constraints on the physical conditions of the region producing the coronal lines. We have realized a novel black hole mass scaling relation with one such prominent coronal line - [Si VI] 1.963 microns, over the 10$^6$ - 10$^8$ M$_{\odot}$ interval, that suggests photoionization by the continuum produced by the accretion disk is the primary physical process at play here. We perform a detailed parameter space study to optimize the emission from these coronal lines in terms of fundamental black hole parameters and test predictions that can be used to measure the kinematics of the extended X-ray emission gas. With the successful launch and first light of the JWST, we are well-poised to refine our findings using the superb angular resolution of the telescope that will allow us to map the inner few parsecs to the central supermassive black holes. This opens up the study of the higher ionization lines that will be spatially resolved by JWST, expanding our sample to tens of hundreds of AGNs, and putting firmer constraints on the physical conditions in the coronal line region., Comment: 3 pages, 1 figure, version matches the published version in Proceedings of the XLV Annual Meeting of the Brazilian Astronomical Society

NGC 5548 has been hailed as an archetypical type-1 active galactic nuclei (AGN) and serves as a valuable laboratory to study the long-term variation of its broad-line region (BLR). In this work, we re-affirm our finding on the connection between the continuum variability in the optical regime and the corresponding H$\beta$ response to it, in order to realize the increase, albeit with a gradual saturation, in the H$\beta$ emitting luminosity with increasing AGN continuum. This effect is also known as the Pronik-Chuvaev effect after the authors who first demonstrated this effect using long-term monitoring of another well-studied Type-1 AGN - Mrk 6. We employ a homogeneous, multi-component spectral fitting procedure over a broad range of spectral epochs that is then used to create the continuum and H$\beta$ light curves. We focus on the epoch range 48636-49686 MJD, different from our previous analysis. We again notice a clear signature of shallowing in the trend between the H$\beta$ and the continuum luminosities. We attempt to recover this H$\beta$ emission trend as a response to a significant continuum flux increase using CLOUDY photoionization simulations and employ a suitable broad-band spectral energy distribution for this source. We explore the wide range in the physical parameters space for modelling the H$\beta$ emission from the BLR appropriate for this source. We employ a constant density, single cloud model approach in this study and successfully recover the observed shallowing of the H$\beta$ emission with respect to the rising AGN continuum and provide constraints on the local BLR densities and the location of the H$\beta$ emitting BLR which agrees with the H$\beta$ time-lags reported from the long-term reverberation mapping monitoring. On the contrary, we do not find a significant breathing effect in the location of the H$\beta$ line-emitting BLR for this epoch in NGC 5548., Comment: 5 pages, 7 figures, version matches the published version in Proceedings of the XLV Annual Meeting of the Brazilian Astronomical Society. arXiv admin note: substantial text overlap with arXiv:2111.05378

Broad lines in active galaxies are primarily emitted by photoionization processes that are driven by the incident continuum arising from a complex geometrical structure circumscribing the supermassive black hole. A model of the broad-band spectral energy distribution (SED) effective in ionizing the gas-rich broad line emitting region (BLR) is needed to understand the various radiative processes that eventually lead to the emission of emission lines from diverse physical conditions. Photoionization codes are a useful tool to investigate two aspects - the importance of the shape of the SED, and the physical conditions in the BLR. In this work, we focus on the anisotropy of continuum radiation from the very centre a direct consequence of the development of a funnel-like structure at regions very close to the black hole. Accounting for the diversity of Type-1 active galactic nuclei (AGNs) in the context of the main sequence of quasars permits us to locate the super Eddington sources along the sequence and constrain the physical conditions of their line-emitting BLR., Comment: 5 pages, 3 figures, version matches the published version in Proceedings of the XLV Annual Meeting of the Brazilian Astronomical Society. arXiv admin note: text overlap with arXiv:2210.15041

Double-peaked profiles associated with the broad-line region (BLR) of active galactic nuclei (AGNs) are regarded as the clearest evidence of the presence of an accretion disk. They are most commonly detected by means of optical spectroscopy in the Balmer lines and in the Mg II $\lambda$2798 ultraviolet line. Here, we report the first unambiguous detection of a double-peak broad emission line associated with the O I $\lambda$11297 emission line in the near-infrared (NIR) in the local Seyfert 1 galaxy III Zw 002. Additionally, we detect simultaneously in the spectrum the double-peak emission in the Pa$\alpha$ line and very likely in the He II $\lambda$10830. This is the first time that several broad double-peaked NIR emission lines have been detected simultaneously. The double-peaked profiles are fit using a disk-based model, with an additional Gaussian component attributed to nondisk clouds, which represents the classical BLR. Our results obtained from the fits reveal important parameters, such as disk inclination and geometry. From the double-peaked profile fits, we suggest that the BLR in III Zw 002 has a disk-like geometry, as it extends up to the outer edge of the BLR., Comment: 8 pages, 3 figures, 1 table, published in ApJ Letters

Compact groups of galaxies (CGs) show members with morphological disturbances, mainly products of galaxy-galaxy interactions, thus making them ideal systems to study galaxy evolution, in high-density environment. To understand how this environment affects the properties of galaxies, we select a sample of 340 CGs in the Stripe 82 region, for a total of 1083 galaxies, and a sample of 2281 field galaxies as a control sample. By performing a multi-wavelength morphological fitting process using S-PLUS data, we divide our sample into early-type (ETG), late-type (LTG), and transition galaxies using the r-band S\'ersic index and the colour (u-r). We find a bimodal distribution in the plane of the effective radius-S\'ersic index, where a secondary "peculiar" galaxy population of smaller and more compact galaxies is found in CGs, which is not observed in the control sample. This indicates that galaxies are undergoing a morphological transformation in CGs. In addition, we find significant statistical differences in the distribution of specific Star Formation Rate (sSFR) when we compare both environments for LTGs and ETGs. We also find a higher fraction of quenched galaxies and a lower median sSFR in CGs than in the control sample, suggesting the existence of environmental effects favoring the cessation of star formation, regardless of galaxy type. Our results support the notion that CGs promote morphological and physical transformations, highlighting their potential as ideal systems for galaxy pre-processing., Comment: 17 pages, 15 figures. Accepted for publication in MNRAS

Development of the Rubin Observatory Legacy Survey of Space and Time (LSST) includes a series of Data Challenges (DC) arranged by various LSST Scientific Collaborations (SC) that are taking place during the projects preoperational phase. The AGN Science Collaboration Data Challenge (AGNSCDC) is a partial prototype of the expected LSST AGN data, aimed at validating machine learning approaches for AGN selection and characterization in large surveys like LSST. The AGNSC-DC took part in 2021 focusing on accuracy, robustness, and scalability. The training and the blinded datasets were constructed to mimic the future LSST release catalogs using the data from the Sloan Digital Sky Survey Stripe 82 region and the XMM-Newton Large Scale Structure Survey region. Data features were divided into astrometry, photometry, color, morphology, redshift and class label with the addition of variability features and images. We present the results of four DC submitted solutions using both classical and machine learning methods. We systematically test the performance of supervised (support vector machine, random forest, extreme gradient boosting, artificial neural network, convolutional neural network) and unsupervised (deep embedding clustering) models when applied to the problem of classifying/clustering sources as stars, galaxies or AGNs. We obtained classification accuracy 97.5% for supervised and clustering accuracy 96.0% for unsupervised models and 95.0% with a classic approach for a blinded dataset. We find that variability features significantly improve the accuracy of the trained models and correlation analysis among different bands enables a fast and inexpensive first order selection of quasar candidates, Comment: Accepted by ApJ. 21 pages, 14 figures, 5 tables

In Khadka et al. (2023), a sample of X-ray-detected reverberation-mapped quasars was presented and applied for the comparison of cosmological constraints inferred using two well-established relations in AGN -- the X-ray/UV luminosity ($L_{X}-L_{UV}$) relation and the broad-line region radius-luminosity ($R-L$) relation. $L_{X}-L_{UV}$ and $R-L$ luminosity distances to the same quasars exhibit a distribution of their differences that is generally asymmetric and positively shifted for the six cosmological models we consider. We demonstrate that this behaviour can be interpreted qualitatively to arise as a result of the dust extinction of UV/X-ray quasar emission. We show that the extinction always contributes to the non-zero difference between $L_{X}-L_{UV}$-based and $R-L$-based luminosity distances and we derive a linear relationship between the X-ray/UV colour index $E_{X-UV}$ and the luminosity-distance difference, which also depends on the value of the $L_{X}-L_{UV}$ relation slope. Taking into account the median and the peak values of the luminosity-distance difference distributions, the average X-ray/UV colour index falls in the range of $\overline{E}_{X-UV}=0.03-0.28$ mag for the current sample of 58 sources. This amount of extinction is typical for the majority of quasars and it can be attributed to the circumnuclear and interstellar media of host galaxies. After applying the standard hard X-ray and far-UV extinction cuts, heavily extincted sources are removed but overall the shift towards positive values persists. The effect of extinction on luminosity distances is more pronounced for the $L_{X}-L_{UV}$ relation since the extinction of UV and X-ray emissions both contribute., Comment: 22 pages, 11 figures, 4 tables; accepted by AAS journals

Optical and UV properties of radio-quiet (RQ) and radio-loud (RL, relativistically "jetted") active galactic nuclei (AGN) are known to differ markedly; however, it is still unclear what is due to a sample selection and what is associated with intrinsic differences in the inner workings of their emitting regions. Chemical composition is an important parameter related to the trends of the quasar main sequence. Recent works suggest that in addition to physical properties such as density, column density, and ionization level, strong FeII emitters require very high metal content. Little is known, however, about the chemical composition of jetted radio-loud sources. In this short note, we present a pilot analysis of the chemical composition of low-z radio-loud and radio-quiet quasars. Optical and UV spectra from ground and space were combined to allow for precise measurements of metallicity-sensitive diagnostic ratios. The comparison between radio-quiet and radio-loud was carried out for sources in the same domain of the Eigenvector 1 / main sequence parameter space. Arrays of dedicated photoionization simulations with the input of appropriate spectral energy distributions indicate that metallicity is sub-solar for RL AGN, and slightly sub-solar or around solar for RQ AGN. The metal content of the broad line emitting region likely reflects a similar enrichment story for both classes of AGN not involving recent circum-nuclear or nuclear starbursts., Comment: 14 pages, 5 figures, to appear in Galaxies

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 10 years will provide dense lightcurves for thousands of active galactic nuclei (AGN) in Deep Drilling Fields (DDFs) and less dense lightcurves for millions of AGN. We model the prospects for measuring time delays for emission lines with respect to the continuum, using these data. We model the artificial lightcurves using Timmer-Koenig algorithm, we use the exemplary cadence to sample them, we supplement lightcurves with the expected contamination by the strong emission lines (Hbeta, Mg II and CIV as well as with Fe II pseudo-continuum and the starlight). We choose the suitable photometric bands appropriate for the redshift and compare the assumed line time delay with the recovered time delay for 100 statistical realizations of the light curves. 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 the accuracy within 1 sigma error, for DDFs results for fainter quasars are also reliable when all 10 years of data are used. There are also some prospects to measure the time delays for the faintest quasars at the smallest redshifts from the first two years of data, and eventually even from the first season. The entire quasar population will allow obtaining results of apparently high accuracy but in our simulations, we see a systematic offset between the assumed and recovered time delay depending on the redshift and source luminosity which will not disappear even in the case of large statistics. Such a problem might affect the slope of the radius-luminosity relation and cosmological applications of quasars if simulations correcting for such effects are not performed., Comment: Astronomy & Astrophysics in press

We use measurements of 59/58 quasars (QSOs), over a redshift range $0.0041\leq z \leq 1.686$, to do a comparative study of the radius--luminosity ($R-L$) and X-ray$-$UV luminosity ($L_X-L_{UV}$) relations and the implication of these relations for cosmological parameter estimation. By simultaneously determining $R-L$ or $L_X-L_{UV}$ relation parameters and cosmological parameters in six different cosmological models, we find that both $R-L$ and $L_X-L_{UV}$ relations are standardizable but provide only weak cosmological parameter constraints, with $L_X-L_{UV}$ relation data favoring larger current non-relativistic matter density parameter $\Omega_{m0}$ values than $R-L$ relation data and most other available data. We derive $L_X-L_{UV}$ and $R-L$ luminosity distances for each of the sources in the six cosmological models and find that $L_X-L_{UV}$ relation luminosity distances are shorter than $R-L$ relation luminosity distances as well as standard flat $\Lambda$CDM model luminosity distances. This explains why $L_X-L_{UV}$ relation QSO data favor larger $\Omega_{m0}$ values than do $R-L$ relation QSO data or most other cosmological measurements. While our sample size is small and only spans a small $z$ range, these results indicate that more work is needed to determine whether the $L_X-L_{UV}$ relation can be used as a cosmological probe., Comment: 20 pages, 10 figures, MNRAS in press

We test a scenario claiming that the broad absorption line (BAL) phenomenon in quasars (QSOs) is not a temporary stage of their life. In this scenario, we see the BAL effect only if the line of sight is within a spatially limited and collimated massive outflow cone covering only a fraction of sky from the point of view of the nucleus. The aim is to understand the theoretical mechanism behind the massive outflow in BAL QSOs which is important for modelling the impact of quasars onto the star formation rate in the host galaxy, and, subsequently, onto the galaxy evolution. We apply the specific theoretical model of dust-driven wind. The model has considerable predictive power. The 2.5D version of FRADO model of Czerny & Hryniewicz gives rise to the formation of fast funnel-shaped outflow from the disk for a certain range of black hole masses, Eddington ratios and metallicities. We now interpret BAL QSO as sources viewed along the outflowing stream and we calculate the probabilities of seeing the BAL phenomenon as functions of these global parameters, and we compare these probabilities to those seen in the observational data. We include considerations on the presence/absence of obscuring torus. Comparing our theoretical results with observational data for a sample consisting of two sub-populations of BAL and non-BAL QSOs we found that both in the model and in the data the BAL phenomenon mostly happens for sources with black hole masses larger than 10^{8} solar mass, the effect get stronger with accretion rate, and also high metallicities are more likely in QSOs showing BAL features if the presence of torus is taken into account. The consistency of the model with the data provides support for the interpretation of the BAL phenomenon as the result of the orientation of the source. It also supports the underlying theoretical model although more consistency checks should be done in the future., Comment: 15 pages, 13 figures, 3 tables, Accepted for publication in the Journal of Astronomy and Astrophysics (A&A)

Since many years we know that dust in the form of the dusty-molecular torus is responsible for the obscuration in active galactic nuclei (AGN) at large viewing angles and thus for the classification of AGN. Recently, we gained some observational and theoretical insight into geometry of the region and the role of the dust in the dynamics of the outflow and failed winds. We will briefly touch on all these aspects, including our dust-based model (FRADO - Failed Radiatively Accelerated Dusty Outflow) of the formation of the Balmer lines in AGN., Comment: Partially based on talk at 31st Symposium on the Physics of Ionized Gases in Belgrade, accepted for European Physical Journal D Topical Issue: "Physics of Ionized Gases and Spectroscopy of Isolated Complex Systems: Fundamentals and Applications"

A landmark of accretion processes in active galactic nuclei (AGN) is the continuum originating from a complex structure, i.e., an accretion disk and a corona around a supermassive black hole. Modelling the broad-band spectral energy distribution (SED) effectively ionizing the gas-rich broad emission line region (BLR) is key to understanding the various radiative processes at play and their importance that eventually leads to the emission from diverse physical conditions. Photoionization codes are a useful tool to investigate two aspects, the importance of the shape of the spectral energy distribution, and the physical conditions in the broad emission line region. In this work, we critically review long-standing issues pertaining to the spectral energy distribution shape and the anisotropic continuum radiation from the central regions around the accreting supermassive black holes (a few 10-100 gravitational radii), with a focus on black holes accreting at high rates, possibly much above the Eddington limit. The anisotropic emission is a direct consequence of the development of a geometrically and optically thick structure at regions very close to the black hole due to a marked increase in the accretion rates. The analysis presented in this paper took advantage of the look at the diversity of the type-1 active galactic nuclei provided by the main sequence of quasars. The main sequence permitted us to assess the importance of the Eddington ratio and hence to locate the super Eddington sources in observational parameter space, as well as to constrain the distinctive physical conditions of their line-emitting BLR. This feat is posing the basis for the exploitation of quasars as cosmological distance indicators, hopefully allowing us to use the fascinating super Eddington quasars up to unprecedented distances., Comment: Identical to the published version in Frontiers in Astronomy and Space Sciences (09-05-2023). 31 pages, 8 figures, 2 tables, based on the invited talk presented at the SPIG - 31st Summer School and International Symposium on the Physics of Ionized Gases, held between 05th - 09th September 2022

As Setti & Woltjer noted back in 1973, quasars could be used to construct the Hubble diagram but the actual application was not that straightforward. It took years to implement the idea successfully. Most of the ways to use quasars for cosmology now require an advanced understanding of their structure, step by step. We briefly review this progress, with unavoidable personal bias, and concentrate on bright unobscured sources. We will mention the problem of the gas flow character close to the innermost stable circular orbit close to the black hole, discussed 50 years ago, which later led to the development of the slim disk scenario, but was recently revived in the context of Magnetically Arrested Disks (MAD) and Standard and Normal Evolution (SANE) disk models. We also discuss the hot/warm corona issue, which is still under discussion and complicates the analysis of the X-ray reflection. We present the scenario of the formation of the low ionization part of the Broad Line Region as a mostly failed wind powered by radiation pressure acting on dust (FRADO - Failed Radiatively Driven Dusty Outflow model). Next, we discuss the cosmological constraints that are currently achievable with quasars, mostly concentrating on light echo methods (continuum time delays and spectral line time delays with respect to the continuum) which are (or should be) incorporating the progress mentioned above. Finally, we briefly mention future prospects in this direction., Comment: Astrophysics and Space Science (in press)

The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will detect an unprecedentedly large sample of actively accreting supermassive black holes with typical accretion disk (AD) sizes of a few light days. This brings us to face challenges in the reverberation mapping (RM) measurement of AD sizes in active galactic nuclei (AGNs) using interband continuum delays. We examine the effect of LSST cadence strategies on AD RM using our metric AGNTimeLagMetric. It accounts for redshift, cadence, the magnitude limit, and magnitude corrections for dust extinction. Running our metric on different LSST cadence strategies, we produce an atlas of the performance estimations for LSST photometric RM measurements. We provide an upper limit on the estimated number of quasars for which the AD time lag can be computed within 01000 sources in each Deep Drilling field (DDF, 10 sq. deg) in any filter, with the redshift distribution of these sources peaking at z~1. We find the LSST observation strategies with a good cadence (~ 5 days) and a long cumulative season (~9 yr), as proposed for LSST DDF, are favored for the AD size measurement. We create synthetic LSST light curves for the most suitable DDF cadences and determine RM time lags to demonstrate the impact of the best cadences based on the proposed metric., Comment: accepted for publication in the Astrophysical Journal Focus Issue on Rubin LSST cadence and survey strategy

We present an analysis of UV spectra of quasars at intermediate redshifts believed to belong to the extreme Population A (xA), aimed to estimate the chemical abundances of the broad line emitting gas. We follow the approach described in a previous work extending the sample to 42 sources. Our aim is to test the robustness of the analysis carried out previously, as well as to confirm the two most intriguing results of this investigation: evidence of very high solar metallicities, and deviation of the relative abundance of elements with respect to solar values. The basis of our analysis is multi-component fits in three regions of the spectra centered at 1900, 1550 and 1400 A in order to deblend the broad components of AlIII1860, CIII]1909, CIV1549, HeII1640, and SiIV1397+OIV]1402 and their blue excess. By comparing the observed flux ratios of these components with the same ratios predicted by photoionization code CLOUDY we found that the virialized gas (broad components) presents a metallicity Z higher than 10Z$_\odot$. For non-virialized clouds we derive a lower limit to the metallicity around $\sim$ 5Z$_\odot$ under the assumption of chemical composition proportional to the solar one, confirming the previous results. We especially rely on the ratios between metal lines and HeII1640. This allowed us to confirm systematic differences in the solar-scaled metallicity derived from the lines of Aluminium and Silicon, and of Carbon, with the first being a factor 2 higher. For luminous quasars accreting at high rates, high Z values are likely, but that Z scaled values are affected by the possible pollution due to highly-enriched gas associated with the circumnuclear star formation. The high-Z values suggest a complex process involving nuclear and circumnuclear star formation, interaction between nuclear compact objects and accretion disk, possibly with the formation of accretion-modified stars., Comment: Accepted for publication in Astronomy and Astrophysics. 29 pages plus an appendix with full spectral analysis

Context. Continuum time delays from accretion disks in active galactic nuclei (AGN) has been proposed long time ago as a tool for measuring distances to the monitored sources. However, the method faces serious problems as a number of effects must be taken into account, including the contribution from the Broad Line Region (BLR). Aims. In this paper, we model the expected time delays when both the disk reprocessing of the incident X-ray flux and further reprocessing by the BLR are included, with the aim to see if the two effects can be disentangled. Methods. We use simple response function for the accretion disk, without relativistic effects, and we use a parametric description to account for the BLR contribution. We include only scattering of the disk emission by the BLR inter-cloud medium. We also use artificial lightcurves with 1-day sampling to check if the effects are likely to be seen in real data. Results. We show that the effect of the BLR scattering on the predicted time delay is very similar to the effect of rising height of the X-ray source, without any BLR contribution. This brings additional degeneracy if we want in the future to recover the parameters of the system from the observed time delays in a specific object. Both effects, however, modify the slope of the delay versus wavelength curve when plotted in log space which opens a way to obtaining bare disk time delay needed for cosmology. In addition, when the disk irradiation is strong, the modification of the predicted delay by the BLR scattering and by X-ray source height become considerably different. However, the required data quality must be high since our artificial curves with 1-day sampling give rather noisy results., Comment: 14 pages, 16 figures, and 1 table. Published in A&A. Comments are welcome

This paper is the first in a series of preparing and analyzing spectral and other properties for a database of already discovered Changing-Look active galactic nuclei (CL AGNs). Here, we focus on the spectral fitting and analysis of broad emission lines in a sample of 93 CL AGNs collected from the literature with existing SDSS/BOSS/eBOSS spectroscopy where the H$\beta$ emission line profile does not completely disappear in any epochs. Additionally, we have gathered older/newer spectral epochs from all the available SDSS data releases to make the database more complete. We use PyQSOFit and perform a homogeneous spectral decomposition of all of our SDSS spectra and tabulate the AGN continuum and emission line properties per epoch per source, chronologically. This further allows us to categorize the sources in our sample as \textit{Turn-On} or \textit{Turn-Off} and subsequently check for repeated occurrences of such phases. We then estimate the black hole mass (M$_{\rm BH}$) and the Eddington ratio (L$_{\rm bol}$/L$_{\rm Edd}$) per epoch per source where the required parameters are available and well-estimated. We realize the movement of the source in the M$_{\rm BH}$ versus L$_{\rm bol}$/L$_{\rm Edd}$ plane allowing us to check for systematic changes in the source's fundamental properties. We then track their transition along the optical plane of the Eigenvector 1 (EV1) schema and categorize sources that either stay within the same Population (A or B) or make an inter-population movement as a function of spectral epoch. We also test the Balmer decrement (H$\alpha$/H$\beta$) of a subset of our sample of CL AGNs as a function of time and AGN luminosity., Comment: 35 pages, 21 figures, 4 tables, accepted for publication in The Astrophysical Journal Supplement Series

We use 38 C IV quasar (QSO) reverberation-mapped (RM) observations, which span eight orders of magnitude in luminosity and the redshift range $0.001064 \leq z \leq 3.368$, to simultaneously constrain cosmological-model and QSO radius-luminosity ($R-L$) relation parameters in six cosmological models, using an improved technique that more correctly accounts for the asymmetric errors bars of the time-lag measurements. We find that $R-L$ relation parameters are independent of the cosmological models used in the analysis and so the $R-L$ relation can be used to standardize the C IV QSOs. The C IV QSO cosmological constraints are consistent with those from Mg II QSOs, allowing us to derive joint C IV + Mg II QSO cosmological constraints which are consistent with currently accelerated cosmological expansion, as well as consistent with cosmological constraints derived using better-established baryon acoustic oscillation (BAO) and Hubble parameter [$H(z)$] measurements. When jointly analyzed with $H(z)$ + BAO data, current C IV + Mg II QSO data mildly tighten current $H(z)$ + BAO data cosmological constraints., Comment: 19 pages, 11 figures, MNRAS accepted version

We use observations of 66 reverberation-measured \Mgii\ quasars (QSOs) in the redshift range $0.36 \leq z \leq 1.686$ -- a subset of the 78 QSOs we previously studied that also have \rfe\ (flux ratio parameter of UV \Feii\ to \Mgii\ that is used as an accretion-rate proxy) measurements -- to simultaneously constrain cosmological model parameters and QSO 2-parameter and 3-parameter radius-luminosity ($R-L$) relation parameters in six different cosmological models. We find that these QSO $R-L$ relation parameters are independent of the assumed cosmological model and so these QSOs are standardizable through the $R-L$ relations. Also: (1) With the 2-parameter $R-L$ relation, we find that the low-\rfe\ and high-\rfe\ data subsets obey the same $R-L$ relation within the error bars. (2) Extending the 2-parameter $R-L$ relation to a 3-parameter one does not result in the hoped-for reduction in the intrinsic dispersion of the $R-L$ relation. (3) Neither of the 3-parameter $R-L$ relations provide a significantly better fit to the measurements than does the 2-parameter $R-L$ relation. These are promising results for the on-going development of \Mgii\ cosmological probes. The first and third of these results differ significantly from those we found elsewhere from analyses of reverberation-measured \hb\ QSOs., Comment: 9 figures, 21 pages. arXiv admin note: text overlap with arXiv:2112.00052

Narrow Line Seyfert 1 (NLSy1) galaxies have been shown to have high Eddington ratios and relatively small black hole masses. The measurement of the black hole masses is based on the virial relation which is dependent on the distribution of the line-emitting gas and the viewing angle to the source. Spectropolarimetry enables us to probe the geometry of this line-emitting gas and allows us to estimate independently the viewing angle of the source by comparing the spectrum viewed under natural light and in the polarized light. We performed spectropolarimetric observations of three NLSy1 - Mrk 1044, SDSS J080101.41+184840.7, and IRAS 04416+1215 using the European Southern Observatory's Very Large Telescope. We use ESO Reflex workflow to perform standard data reduction and extract the natural and polarized spectra. We estimate the Stokes parameters and the viewing angles of the three sources. We model the Stokes parameters and infer the properties of the scattering media - located in the equatorial and polar regions, and simulate the spectra observed both in natural light and in polarized light using the polarization radiative transfer code STOKES. We confirm that all three sources are high Eddington ratio objects. We are successful in recovering the observed H$\alpha$ line profile both in the natural and polarized light using the STOKES modelling. We recover the polarization fractions of the order of 0.2-0.5% for the three sources. Our principal component analysis shows that the sample of the 25 sources including our sources, Fairall 9 from Jiang et al. (2021), and sources from Capetti et al. (2021) are mainly driven by the black hole mass and Eddington ratio. We re-affirm the connection of the strength of the optical FeII emission with the Eddington ratio, but the dependence on the viewing angle is moderate, more like a secondary effect., Comment: 25 pages, 21 figures, 11 tables, to be published in Astronomy & Astrophysics, version after proofs

The study of the broad-line region (BLR) using reverberation mapping has allowed us to establish an empirical relation between the size of this line emitting region and the continuum luminosity that drives the line emission (i.e. the R$_{\rm BLR}$-L$_{\rm 5100}$ relation). To realize its full potential, the intrinsic scatter in the R$_{\rm BLR}$-L$_{\rm 5100}$ relation needs to be understood better. The Eddington ratio plays a key role in addressing this problem. On the other hand, the Eigenvector 1 schema has helped to reveal an almost clear connection between the Eddington ratio and the strength of the optical FeII emission which has its origin from the BLR. This paper aims to reveal the connection between theoretical entities, like, the ionization parameter (U) and cloud mean density (n$_{\rm H}$) of the BLR, with physical observables obtained directly from the spectra, such as optical FeII strength (R$_{\rm FeII}$) that has immense potential to trace the accretion rate. We utilize the photoionization code CLOUDY and perform a suite of models to reveal the BLR in the U-n parameter space and estimate RFeII. We compare the SEDs for a prototypical Population A and Population B source, I Zw 1 and NGC 5548, respectively, in this study. The results from the photoionization modelling are combined with existing reverberation mapped sources with observed R$_{\rm FeII}$ estimates, allowing us to provide an analytical formulation to tie together the aforementioned quantities. We utilize the comparison of the modelled equivalent widths for the low-ionization emission lines to their observed values to identify the optimal (U,n$_{\rm H}$). The recovery of the correct physical conditions in the BLR suggests that the BLR `sees' a different, filtered ionizing continuum with only a very small fraction (~1-10%) that leads to the line emission in the dustless, low-ionization BLR., Comment: 33 pages, 12 figures, 4 tables, accepted for publication in `Frontiers in Astronomy and Space Sciences: Rising Stars' Issue

The issue of the difference between optical and UV properties of radio-quiet and radio-loud (relativistically "jetted") active galactic nuclei (AGN) is a long standing one, related to the fundamental question of why a minority of powerful AGN possess strong radio emission due to relativistic ejections. This paper examines a particular aspect: the singly-ionized iron emission in the spectral range 4400 -- 5600 A, where the prominent HI H$\beta$ and [OIII] 4959, 5007 lines are also observed. We present a detailed comparison of the relative intensity of Fe II multiplets in the spectral types of the quasar main sequence where most jetted sources are found, and afterwards discuss radio-loud narrow-line Seyfert 1 (NLSy1) nuclei with $\gamma$-ray detection and with prominent Fe II emission. An Fe II template based on I Zw 1 provides an accurate representation of the optical Fe II emission for RQ and, with some caveats, also for RL sources. CLOUDY photoionization simulations indicate that the observed spectral energy distribution can account for the modest Fe II emission observed in composite radio-loud spectra. However, spectral energy differences alone cannot account for the stronger Fe II emission observed in radio-quiet sources, for similar physical parameters. As for RL NLSy1s, they do not seem to behave like other RL sources, likely because of their different physical properties that could be ultimately associated with a higher Eddington ratio., Comment: 27 pages, to appear in Universe as a contribution to the special issue "Panchromatic View of the Life-Cycle of AGN" (M. Berton, Editor)

Broad-band spectra of active galaxies contain a wide range of information that help reveal the nature and activity of the central continuum source and their immediate surroundings. Understanding the evolution of metals in the spectra of Active Galactic Nuclei (AGN) and linking them with the various fundamental black hole (BH) parameters, for example, BH mass, the bolometric luminosity of the source, its accreting power, can help address the connection between the growth of the BH across cosmic time. We investigate the role of selected metallicity indicators utilizing the rich spectroscopic database of emission lines covering a wide range in redshift in the recent spectroscopic data release of Sloan Digital Sky Survey (SDSS). We make careful filtering of the parent sample to prepare a pair of high-quality, redshift-dependent sub-samples and present the first results of the analysis here. To validate our findings from the simple correlations, we execute and evaluate the performance of a linear dimensionality reduction technique - principal component analysis (PCA), over our sub-samples and present the projection maps highlighting the primary drivers of the observed correlations. The projection maps also allow us to isolate peculiar sources of potential interest., Comment: 3 pages, 2 figures, submitted to the Proceedings of the 40th Polish Astronomical Society Meeting, 13-17 September 2021, Szczecin, Poland

Using bonafide black hole (BH) mass estimates from reverberation mapping and the line ratio [Si VI]1.963$\mu$m/Br$\gamma_{\rm broad}$ as tracer of the Active Galactic Nuclei (AGN) ionizing continuum, we find a novel BH-mass scaling relation of the form log($M_{\rm BH}) = (6.40\pm 0.17) - (1.99\pm 0.37) \times$ log ([Si VI]/Br$\gamma_{\rm broad})$, over the BH mass interval, $10^6 - 10^8$ M$_{\odot}$. The current sample consists of 21 Type-1 AGNs with the overall dispersion in our scaling relation at 0.47 dex, one that emulates the well-established M-$\sigma$ relation which shows a dispersion $\sim$0.44 dex. The new scaling offers an economic, and physically motivated alternative for BH estimate using single epoch spectra, avoiding large telescope time (reverberation mapping) or absolute flux calibration (the continuum luminosity method). With the advent of big surveys in the infrared in the near future, we aim to reduce the scatter in the relation by supplementing with more sources., Comment: 3 pages, 1 figure, submitted to the Proceedings of the 40th Polish Astronomical Society Meeting, 13-17 September 2021, Szczecin, Poland

The CaFe Project involves the study of the properties of the low ionization emission lines (LILs) pertaining to the broad-line region (BLR) in active galaxies. These emission lines, especially the singly-ionized iron (Fe II) in the optical and the corresponding singly-ionized calcium (Ca II) in the near-infrared (NIR) are found to show a strong correlation in their emission strengths, i.e., with respect to the broad H$\beta$ emission line, the latter also belonging to the same category of LILs. We outline the progress made in the past years that has developed our understanding of the location and the efficient production of these emission lines. We have yet to realize the full potential of Ca II emission and its connection to the black hole and the BLR parameters which can be useful in - (1) the classification of Type-1 active galactic nuclei (AGNs) in the context of the main sequence of quasars, (2) to realize an updated radius-luminosity relation wherein the inclusion of the strength of this emission line with respect to H$\beta$ can be an effective tracer of the accretion rate of the AGN, and, (3) the close connection of Ca II to Fe II can allow us to use the ratio of the two species to quantify the chemical evolution in these active galaxies across cosmic time. In this paper, we use our current sample and utilize a non-linear dimensionality reduction technique - t-distributed Stochastic Neighbour Embedding (tSNE), to understand the clustering in our dataset based on direct observables., Comment: 6 pages, 3 figures, submitted to the Proceedings of the 40th Polish Astronomical Society Meeting, 13-17 September 2021, Szczecin, Poland

Using bona-fide black hole (BH) mass estimates from reverberation mapping and the line ratio [SiVI] 1.963$\mu$m/Br$\gamma_{\rm broad}$ as tracer of the AGN ionising continuum, a novel BH-mass scaling relation of the form log($M_{\rm BH}) = (6.40\pm 0.17) - (1.99\pm 0.37) \times$ log ([SiVI]/Br$\gamma_{\rm broad})$, dispersion 0.47 dex, over the BH mass interval, $10^6 - 10^8$ M$_{\odot}$ is found. Following on the geometrically thin accretion disc approximation and after surveying a basic parameter space for coronal lines production, we believe one of main drivers of the relation is the effective temperature of the disc, which is effectively sampled by the [SiVI] 1.963$\mu$m coronal line for the range of BH masses considered. By means of CLOUDY photoionisation models, the observed anti-correlation appears to be formally in line with the thin disc prediction T_disc $\propto {M_{\rm BH}}^{-1/4}$., Comment: 22 pages, 16 figures. Accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:2010.00075

We report preliminary results on the analysis of the continuum and H$\beta$ light curves of the type-1 active galactic nucleus (AGN) NGC 5548. We notice a clear signature of shallowing in the trend between the H$\beta$ and the continuum luminosities. We attempt the recovery of this observed H$\beta$ emission trend as a response to large continuum flux increase using CLOUDY photoionization simulations. We explore a wide range in the physical parameters space for modelling the H$\beta$ emission from the broad-line region (BLR) appropriate for this source. We employ a constant density, single cloud model approach in this study and successfully recover the observed shallowing of the H$\beta$ emission with respect to the rising AGN continuum. With our modelling, we are able to provide constraints on the local BLR cloud density and recover the BLR distances (from the continuum source) consistent with the H$\beta$ reverberation mapping estimates. We further discuss the implications of the BLR covering factor and their sizes on recovering the observed trend., Comment: 10 pages, 7 figures, accepted version after proofs in Astronomische Nachrichten (Special Issue, 13th Serbian Conference on Spectral Line Shapes in Astrophysics)

The CaFe Project involves the study of the properties of the low ionization emission lines (LILs) pertaining to the broad-line region (BLR) in active galaxies. These emission lines, especially the singly-ionized iron (Fe II) in the optical and the corresponding singly-ionized calcium (Ca II) in the near-infrared (NIR) are found to show a strong correlation in their emission strengths, i.e. with respect to the broad H$\beta$ emission line, the latter also belonging to the same category of LILs. The origin of this correlation is attributed to the similarity in the physical conditions necessary to emit these lines - especially in terms of the strength of the ionization from the central continuum source and the local number density of available matter in these regions. In this paper, we focus on the issue of the spectral energy distribution (SED) characteristic to a prototypical Type-1 Narrow-line Seyfert galaxy (NLS1) - I Zw 1. We extract the continuum from quasi-simultaneous spectroscopic measurements ranging from the near-UV ($\sim$1200A) to the near-infrared ($\sim$24000A) to construct the SED and supplement it with archival X-ray measurements available for this source. Using the photoionization code CLOUDY, we assess and compare the contribution of the prominent "Big Blue Bump" seen in our SED versus the SED used in our previous work, wherein the latter was constructed from archival, multi-epoch photometric measurements. Following the prescription from our previous work, we constrain the physical parameter space to optimize the emission from these LILs and discuss the implication of the use of a "better" SED., Comment: 11 pages, 5 figures, accepted version after proofs, Acta Astrophysica Taurica proceedings for Crimean-2021 AGN Conference "Galaxies with Active Nuclei on Scales from Black Hole to Host Galaxy" dedicated to the E.A. Dibai's 90th anniversary (13-17 September 2021)

The quasar Main Sequence (MS) appears to be an incredibly powerful tool to organize the diversity in large samples of type-1 quasars but the most important physical parameters governing it are still unclear. Here we investigate the origin of the broadening and of a defining feature of Population B sources: a strong redward asymmetry of the Balmer emission lines. We focus on a prototypical source, Fairall 9. Spectropolarimetric data of the Fairall 9 broad H$\beta$ and H$\alpha$ profiles allowed for a view of the geometric and dynamical complexity of the line emitting regions. Measurements (1) provided evidence of rotational motion; (2) were helpful to test the presence of polar and equatorial scatterers, and their association with non-virial motions., Comment: 22 pages, 3 tables and 14 figures. Accepted for publication in MNRAS

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., Comment: 13 pages, 4 figures, 2 tables, Accepted for publication in ApJ

In this second paper in the series, we carefully analyze the observational properties of the optical FeII and NIR CaII triplet in Active Galactic Nuclei, as well as the luminosity, black hole mass, and Eddington ratio in order to define the driving mechanism behind the properties of our sample. The CaII shows an inverse Baldwin effect, bringing out the particular behavior of this ion with respect to the other low-ionization lines such as H$\beta$. We performed a Principal Component Analysis, where 81.2% of the variance can be explained by the first three principal components drawn from the FWHMs, luminosity, and equivalent widths. The first principal component (PC1) is primarily driven by the combination of black hole mass and luminosity with a significance over 99.9%, which in turn is reflected in the strong correlation of the PC1 with the Eddington ratio. The observational correlations are better represented by the Eddington ratio, thus it could be the primary mechanism behind the strong correlations observed in the CaII-FeII sample. Since calcium belongs to the $\alpha$-elements, the FeII/CaII flux ratio can be used as a chemical clock for determining the metal content in AGN and trace the evolution of the host galaxies. We confirm the de-enhancement of the ratio FeII/CaII by the Eddington ratio, suggesting a metal enrichment of the BLR in intermediate-$z$ with respect to low-$z$ objects. A larger sample, particularly at $z$>2, is needed to confirm the present results., Comment: 35 pages, 16 figures, 4 tables. Accepted for publication in ApJ

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 $(\Omega_{\rm m}, \Omega_{\Lambda})=(0.19; 0.62)$ are consistent with the standard cosmological model within 1$\sigma$ confidence level., Comment: 34 pages, 23 figures, 6 tables; accepted by the Astrophysical Journal; Main body as well as the Appendix extended; added references

Getting insights on the shape and nature of the ionizing continuum in astronomical objects is often done via indirect methods as high energy photons are absorbed by our Galaxy. This work explores the ionization continuum of active galactic nuclei (AGN) using the ubiquitous coronal lines. Using bona-fide BH mass estimates from reverberation mapping and the line ratio [Si VI] 1.963 micron/Br$\gamma_{\rm broad}$ as tracer of the AGN ionizing continuum, a novel BH-mass scaling relation of the form log($M_{\rm BH}) = (6.40\pm 0.17) - (1.99\pm 0.37) \times$ log ([Si VI]/Br$\gamma_{\rm broad})$, over the BH mass interval, $10^6 - 10^8$ M$_{\odot}$ with dispersion 0.47 dex is found. Following on the thin accretion disc approximation and after surveying a basic parameter space for coronal lines production, we believe that a key parameter driving this anti-correlation is the effective temperature of the accretion disc, this being effectively sampled by the coronal line gas. Accordingly, the observed anti-correlation becomes formally in line with the thin accretion disc prediction $T_{\rm{disc}} \propto {M_{\rm BH}}^{-1/4}$., Comment: 16 pages, 6 figures. Submitted to ApJ