Tonima Tasnim Ananna

Context . Active galactic nuclei (AGNs) play a crucial role in galaxy evolution, but they are a minority of extragalactic sources with diverse spectral energy distributions (SEDs), which depend on their means of selection. Upcoming large-scale surveys such as LSST will identify many AGNs, but analysis tools are not optimized for them. The limited number of photometric bands in these surveys impacts the calculation of photometric redshifts for AGNs, which are essential for scientific advancement. Aims . We use LePHARE to demonstrate the impact that a limited number of bands and erroneous assumptions have on the determination of the photometric redshifts of AGNs. We conducted tests on six AGN samples selected using X-ray, radio, infrared, variability, color, and spectroscopic criteria in the COSMOS field, using photometry from HSC-CLAUDS, which is closest in depth and wavelength coverage to LSST. Methods . We present the LSST pipeline for LePHARE within the redshift assessment infrastructure layers (RAIL), facilitating comparison between SED fitting and machine-learning algorithms. Results . AGNs that appear as point-like sources in optical data are assigned highly unreliable photometric redshifts if they are processed using galaxy templates. Additionally, shallow all-sky surveys (such as eROSITA, WISE, and ZTF) miss many AGNs. As a result, these “hidden” AGNs are often misidentified as galaxies in public survey data, leading to incorrect photometric redshifts. Conclusions . We provide the configurations that are suggested for each type of AGN alongside measures of expected performance as a function of redshift, magnitude, and selection. To facilitate studies with a panchromatic view of AGNs, we also released photometric redshifts and posterior distributions for all AGN sources identified in the COSMOS field using the six criteria, based on 28-band photometry.

X-ray surveys of active galactic nuclei (AGNs) provide direct constraints on the properties of individual AGNs, such as their emission, obscuration, and accretion rate. Previous AGN population synthesis models have not addressed such properties self-consistently. For this study, we used a simulation-based inference (SBI) approach to constrain the geometrical and physical properties of the AGN population. We performed numerical simulations with our ray-tracing code, R EFLE X, which allows the self-consistent modelling of the X-ray emission of AGNs with flexible circumnuclear and source geometries. We created our synthetic population by sampling the intrinsic active black hole mass function (BHMF) and Eddington ratio distribution function (ERDF) of local AGNs, and we constructed a geometry based on the radiation-regulated model, along with Eddington-ratio-dependent emission spectra. Using the R EFLE X-simulated emission of the AGN population, we aimed to simultaneously reproduce the cosmic X-ray background (CXB), differential AGN number counts, and several observed absorption properties of local AGNs, such as the fraction of N _H in bins of log( N _H ), the Compton-thick fraction as a function of the limiting flux, and the number of obscured and unobscured AGNs as a function of the Eddington ratio. With this approach, we tested the consistency of the radiation-regulated model with a very comprehensive set of X-ray observables, while constraining the size and density of the dusty torus and the evolution of the local AGN population. We derive an intrinsic Compton-thick fraction of 40 ± 3%, and find that a simple evolutionary prescription controlling the active fraction of supermassive black holes is sufficient for our synthetic population to reproduce the CXB. Finally, we compare the inferred dusty torus structure to observations and examine the dependence of the covering factor on Eddington ratio, the observed correlation between reflection and obscuration, and the BHMFs and ERDFs of obscured and unobscured AGNs.

Compact and red sources in the high-redshift ( z ∼ 5) Universe, known as “Little Red Dots” (LRDs), are among JWST’s most intriguing discoveries. These sources have broad Balmer emission lines, weak X-ray emission, and unique spectral energy distributions (SEDs) poorly fit by either stellar or active galactic nucleus (AGN) templates. Local LRD-like objects allow for detailed studies of the underlying physical processes with archival multiwavelength datasets unavailable in the high- z Universe. We show that the Sloan Digital Sky Survey (SDSS) ugriz filters at z ≈ 0.4, 0.8 overlap well with the JWST filters used to select LRDs at z ∼ 5. We use SDSS quasars to define a sample of ∼1300 Local Red Dots (LoRDs) that share the same photometric colors of LRDs. A subset of the LoRD sample selected to have V-shaped continua ( N = 244) show prominent higher-order Balmer absorption features and [Ne v ] λ 3426 emission, both of which would likely be missed in JWST/PRISM observations given the low spectral resolution. A composite SED of the LoRDs differs from a typical quasar SED in the rest-frame UV/optical, but the two agree with each other in the near-infrared. The LoRD SED matches well with a stack of LRDs and can be modeled either as a reddened AGN combined with a host galaxy, or as a reddened AGN combined with a host galaxy and a cool blackbody. Interestingly, the LoRDs are X-ray detected at a rate comparable to typical quasars. However, the probability that LoRDs and typical quasars would go undetected, if subject to the LRD X-ray upper limits, is >50%.

Aims. Contemporary large-scale surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) and Euclid present an unprecedented discovery potential for studying active galactic nuclei (AGNs) at the population level in the big data era. However, one major challenge is the accurate identification and classification of AGNs from optical and near-infrared photometry or variability data alone. To optimize active galactic nucleus (AGN) selection, classification, and systematics as well as to test different data analysis tools, we present AGILE (AGNs In the LSST Era), an LSST end-to-end simulation software. Developed as part of the INAF LSST in-kind contribution, AGILE is capable of simulating the anticipated AGN population in LSST and Euclid. Methods. We based AGILE on existing simulations of galaxies and stars, while we developed an AGN recipe based on empirical relations. AGILE populates complete galaxy samples with AGNs according to the observed AGN accretion rate distribution, and each AGN is assigned an optical/UV spectral energy distribution. Optical AGN variability is added using a damped random walk model connected to the AGN physical parameters. Finally, AGILE creates both LSST-like images and related data products. Results. Using AGILE, we built a 24 deg ² complete mock truth catalog of AGNs, galaxies, and stars with 0.2 < z < 5.5, log ₁₀ ( M _star / M _⊙ ) > 8.5 (AGNs and galaxies), and r < 27.5 mag (stars). We also performed a pilot simulation (AGILE DR1) consisting of 1 deg ² of LSST operations in the COSMOS field observed up to three years in accordance with the survey strategy. We used AGILE DR1 to quantify the accuracy of the LSST Science Pipelines in recovering the true fluxes of AGNs, galaxies, and stars. We quantified the LSST completeness and purity in recovering Type 1 AGNs using typical color-color and variability selections. We share the AGILE DR1 dataset, as it represents an ideal test bench for further scientific exploitation and forecasts in the context of LSST AGNs.

We present an analysis of spectral energy distributions (SEDs), galaxy light profiles, and visual morphological classifications for 194 X-ray luminous active galactic nuclei (AGN) (intrinsic absorption-corrected log ( L X , 0.5 − 7 keV ) > 42.5 ( maximum 45.2 ) erg s − 1 ) with z < 1.5 in the Great Observatories Origins Deep Survey (GOODS) fields. We generate X-ray to far-infrared SEDs normalized at 1 μ m for all AGN and sort them according to their emission slopes in the ultraviolet (UV) and infrared (IR). We visually classify their host galaxies’ morphologies and compute their bulge/total light ratios using the Galaxy Shapes of Light ( galight ) software. Most (94%) GOODS AGN exhibit obscured (i.e., diminished UV and/or mid-IR emission) SEDs. Only 6% show unobscured, quasar-like SEDs. Secular processes appear to play a large role in stimulating AGN emission, since only ∼1/3 of galaxies are undergoing interactions. We also describe the morphological identification of a population of suspected postmerger spheroid galaxies with obscured UV/IR SEDs and distinguish them from the host galaxies of AGN with less obscuration in the UV or IR.

The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) is expected to obtain observations of over ten million quasars. The survey’s exceptional cadence and sensitivity will enable a significant fraction of these objects to be monitored in the ugrizy bands, spanning observed wavelengths of approximately 0.3 − 1.0 μm. The unprecedented number of sources makes spectroscopic follow-up for the vast majority of them unfeasible in the near future, so most studies will have to rely on photometric redshift estimates which are traditionally much less reliable for Active Galactic Nuclei (AGNs) than for inactive galaxies. This work presents a novel methodology to constrain the photometric redshift of AGNs that leverages the effects of cosmological time dilation, and of the luminosity and wavelength dependence of AGN variability. Specifically, we assume that the variability can be modeled as a damped random walk (DRW) process, and we adopted a parametric model to characterize the DRW timescale ( τ ) and asymptotic amplitude of the variability (SF _∞ ) based on the redshift, the rest-frame wavelength, and the AGN luminosity. We constructed variability-based photometric redshift (photo- z ) priors by modeling the observed variability using the expected DRW parameters at a given redshift. These variability-based photo- z ( VAR-PZ ) priors were then combined with traditional spectral energy distribution (SED) fitting to improve the redshift estimates from SED fitting. Validation was performed using observational data from the Sloan Digital Sky Survey (SDSS), demonstrating significant reduction in catastrophic outliers by more than 10% in comparison with SED fitting techniques and improvements in redshift precision. The simulated light curves with both SDSS and LSST-like cadences and baselines confirm that VAR-PZ will be able to constrain the photometric redshifts of SDSS-like AGNs by bringing the outlier fractions down to below 15% from 32% (SED alone) at the end of the survey.

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 yr with an average cadence of 3 days in six broad photometric bands. This unprecedented data set 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 ∼10 ² –10 ⁴ × 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 for 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.

Identifying active galactic nuclei (AGNs) using only one wavelength region may miss AGNs with characteristics unfavorable for the identification method, which introduces bias in the sample. To better understand these selection effects, we compare the multiwavelength properties of 2584 X-ray- and IR-selected AGNs at z < 3 in the COSMOS field. The X-ray-selected sample consists of the 2219 AGNs with intrinsic 0.5–10 keV X-ray luminosity greater than 10 ⁴³ erg s ⁻¹ ; the 993 IR-selected AGNs are identified by their high-contrast, power-law IR colors using Spitzer/IRAC observations. We find that both selection methods miss a significant fraction of AGNs, as only 24.3% of AGNs (628 out of the total of 2584 AGNs) are recovered by both selection criteria. X-ray selection can capture the most diverse range of multiwavelength spectral emission features, while IRAC selection is biased against AGNs with a steeply decreasing power flux ( λF _λ ) between 1 and 6 μ m. For AGNs with X-ray detections, IRAC-selected sources are 2.5× more X-ray luminous than AGNs not identified by their IR colors. IRAC-selected AGNs without detectable X-rays are obscured, as they have a mean X-ray correction factor log ( L X , obs / L X , int ) = −1.4; 28.5%–42.2% of these AGNs are Compton-thick (according to estimated column densities). Only 1.4% of X-ray-selected AGNs are Compton-thick. The AGN selection technique used significantly impacts the overall characteristics of the resulting AGN sample.

We present an analysis of spectral energy distributions (SEDs), galaxy light profiles, and visual morphological classifications for 194 X-ray luminous AGN (intrinsic absorption-corrected log10 LX(0.5 to 7 keV) less than 42.5, with a maximum of 45.2 ergs per second) at redshift z less than 1.5 in the GOODS fields. We generate X-ray to far-infrared SEDs normalized at 1 micron for all AGN and sort them according to their emission slopes in the ultraviolet and infrared. We visually classify their host galaxy morphologies and compute their bulge-to-total light ratios using the software Galaxy Shapes of Light (galight). Most (94 percent) GOODS AGN exhibit obscured SEDs, defined by diminished ultraviolet and/or mid-infrared emission, while only 6 percent show unobscured, quasar-like SEDs. Secular processes appear to play a large role in stimulating AGN emission, as only around one-third of galaxies are undergoing interactions. We also describe the morphological identification of a population of suspected post-merger spheroid galaxies with obscured ultraviolet and infrared SEDs, and distinguish them from the host galaxies of AGN with less obscuration in the ultraviolet or infrared.

X-ray surveys are one of the most unbiased methods for detecting Compton-thick (CT; N _H ≥ 10 ²⁴ cm ⁻² ) active galactic nuclei (AGN), which are thought to comprise up to 60% of AGN within z ≲ 1.0. These CT AGN are often difficult to detect with current instruments, but the X-ray data within the JWST-North Ecliptic Pole (NEP) Time Domain Field present a unique opportunity to study faint and obscured AGN. The NEP contains the deepest NuSTAR survey to date, and X. Zhao et al. detected 60 hard X-ray sources from the combined exposure of NuSTAR’s Cycle 5 and 6 observations. In this work, we utilize the NuSTAR Cycle 5+6+8+9 data and simultaneous XMM-Newton observations in order to perform the first spectroscopic analysis of the 60 source catalog. We present this analysis and measure the N _H distribution of the sample. We measure an observed CT fraction of 0.1 3 − 0.04 + 0.15 down to an observed 8–24 keV flux of 6.0 × 10 ⁻¹⁴ erg s cm ⁻² , and we correct our analysis for absorption bias to estimate an underlying CT fraction of 0.3 2 − 0.08 + 0.23 . The derived obscuration distribution and CT fraction are consistent with population synthesis models and previous surveys.