Multiwavelength Survey Research Articles

A discussion on estimating small bodies taxonomies using phase curves results

Upcoming large multiwavelength photometric surveys will provide a leap in our understanding of small body populations, among other fields of modern astrophysics. Serendipitous observations of small bodies in different orbital locations allow us to study diverse phenomena related to how their surfaces scatter solar light.In particular, multiple observations of the same object in different epochs permit us to construct their phase curves to obtain absolute magnitudes and phase coefficients. In this work, we tackle a series of long-used relationships associating these phase coefficients with the taxa of small bodies and suggest that some may need to be revised in the light of large-number statistics.

The fundamental plane of black hole activity for low-luminosity radio active galactic nuclei across 0 < z < 4

Context. The fundamental plane of black hole activity describes the correlation between radio luminosity (LR), X-ray luminosity (LX), and black hole mass (MBH). It reflects a connection between the accretion disc and the jet. However, the dependence of the fundamental plane on various physical properties of active galactic nuclei (AGNs) and host galaxies remains unclear, especially for low-luminosity AGNs, which is important for understanding the accretion physics in AGNs. Aims. Here, we explore the dependence of the fundamental plane on the radio loudness, Eddington-ratio (λEdd), redshift, and galaxy star formation properties (star-forming galaxies and quiescent galaxies) across 0.1 < z ≤ 4 for radio AGNs. Based on current deep and large surveys, our studies can extend to lower luminosities and higher redshifts. Methods. From the deep and large multi-wavelength surveys in the GOODS-N, GOODS-S, and COSMOS/UltraVISTA fields, we constructed a large and homogeneous radio AGN sample consisting of 208 objects with available estimates for LR and LX. Then we divided the radio AGN sample into 141 radio-quiet AGNs and 67 radio-loud AGNs according to the radio loudness defined by the ratio of LR to LX, and explored the dependence of the fundamental plane on different physical properties of the two populations, separately. Results. The ratio of LR to LX shows a bimodal distribution that is well described by two single Gaussian models. The cross point between these two Gaussian components corresponds to a radio-loudness threshold of log(LR/LX) = − 2.73. The radio-quiet AGNs have a significantly larger Eddington ratio than the radio-loud AGNs. Our radio-quiet and radio-loud AGNs show a significantly different fundamental plane, which indicates a significant dependence of the fundamental plane on the radio loudness. For both radio-quiet and radio-loud AGNs, the fundamental plane shows a significant dependence on λEdd, but no dependence on redshift. The fundamental plane shows a significant dependence on the galaxy star formation properties for radio-quiet AGNs, while for radio-loud AGNs this dependence disappears. Conclusions. The fundamental plane sheds important light on the accretion physics and X-ray emission origins of central engines. X-ray emission of radio-quiet AGNs at 0.01 < λEdd < 0.1 are produced by a combination of advection-dominated accretion flow (ADAF) and synchrotron radiation from the jet, while at 0.1 < λEdd < 1 they mainly follow the synchrotron jet model. The origins of X-ray emission of radio-loud AGNs are consistent with a combination of ADAF and the synchrotron jet model at λEdd < 0.01, agree with the synchrotron jet model at 0.01 < λEdd < 0.1, and follow a combination of the standard thin disc and a jet model at λEdd > 0.1.

A Multiwavelength Survey of Nearby M Dwarfs: Optical and Near-ultraviolet Flares and Activity with Contemporaneous TESS, Kepler/K2, Swift, and HST Observations

We present a comprehensive multiwavelength investigation into flares and activity in nearby M dwarf stars. We leverage the most extensive contemporaneous data set obtained through the Transiting Exoplanet Sky Survey, Kepler/K2, the Neil Gehrels Swift Observatory, and the Hubble Space Telescope, spanning the optical and near-ultraviolet (NUV) regimes. In total, we observed 213 NUV flares on 24 nearby M dwarfs, with ∼27% of them having detected optical counterparts, and found that all optical flares had NUV counterparts. We explore NUV/optical energy fractionation in M dwarf flares. Our findings reveal a slight decrease in the ratio of optical to NUV energies with increasing NUV energies, a trend in agreement with prior investigations on G–K stars’ flares at higher energies. Our analysis yields an average NUV fraction of flaring time for M0–M3 dwarfs of 2.1%, while for M4–M6 dwarfs it is 5%. We present an empirical relationship between NUV and optical flare energies and compare to predictions from radiative hydrodynamic and blackbody models. We conducted a comparison of the flare frequency distribution (FFDs) of NUV and optical flares, revealing that the FFDs of both NUV and optical flares exhibit comparable slopes across all spectral subtypes. NUV flares on stars affect the atmospheric chemistry, the radiation environment, and the overall potential to sustain life on any exoplanets they host. We find that early and mid-M dwarfs (M0–M5) have the potential to generate NUV flares capable of initiating abiogenesis.

STONKS: Quasi-real time XMM-Newton transient detection system

Over recent decades, astronomy has entered the era of massive data and real-time surveys. This is improving the study of transient objects -- although they still contain some of the most poorly understood phenomena in astrophysics, as it is inherently more difficult to obtain data to constrain the proposed models. In order to help detect these objects in their brightest state and build synergies with multi-wavelength real-time surveys, we have built a quasi-real time automatic transient detection system for the XMM-Newton pipeline: the Search for Transient Objects in New detections using Known Sources (STONKS) pipeline. STONKS detects long-term X-ray transient events by automatically comparing new XMM-Newton detections to any available archival X-ray data at this position, sending out an alert if the variability between observations (defined as the ratio between the maximum flux and the minimum flux or upper limit) is over 5. This required an initial careful cross-correlation and flux calibration of various X-ray catalogs from different observatories ( XMM-Newton Chandra Swift ROSAT, and eROSITA). A Bayesian framework was put into place to solve any ambiguous associations. We also systematically computed the XMM-Newton upper limits at the position of any X-ray source covered by the XMM-Newton observational footprint, even without any XMM-Newton counterpart. The behavior of STONKS was then tested on all 483 observations performed with imaging mode in 2021. Over the 2021 testing run, STONKS provided a daily alert rate of 0.7$^ $ alerts per day, about 80<!PCT!> of them corresponding to serendipitous sources. Among the detected variable serendipitous sources, there are: several highly variable active galactic nuclei (AGNs) and flaring stars, as well as new X-ray binary and ultra-luminous X-ray source candidates, some of which are present here. STONKS also detected targeted tidal disruption events, ensuring its ability to detect other serendipitous events. As a byproduct of our method, the archival multi-instrument catalog contains about one million X-ray sources, with 15<!PCT!> of them involving several catalogs and 60<!PCT!> of them having XMM-Newton (pointed or slew) upper limits. STONKS demonstrates a great potential for revealing future serendipitous transient X-ray sources, providing the community with the ability to follow-up on these objects a few days after their detection with the goal of obtaining a better understanding of their nature. The underlying multi-instrument archival X-ray catalog will be made available to the community and kept up to date with future X-ray data releases.

The star formation, dust, and abundance of galaxies with unWISE-CIB cross-correlations

The cosmic infrared background (CIB) is the accumulated infrared (IR) radiation mainly from interstellar dust heated up by early stars. In this work, we measure the cross-correlation between galaxies from the unWISE catalog and the CIB maps from the Planck satellite to simultaneously constrain the cosmic star formation rate (SFR), dust spectral energy distribution (SED), and the halo occupation distribution (HOD). The unWISE galaxy catalog is divided into three tomographic bins centered at z ∼ 0.6, 1.1, 1.5, and the CIB maps are at 353, 545, and 857 GHz. We measure the cross-correlations between these galaxy samples and CIB maps and get a 194σ signal within an angular scale 100<ℓ<2000, from which we constrain two CIB halo models from previous literature and one new model. The SFR, SED, and HOD model parameters are constrained consistently among the three models. Specifically, the dust temperature at z = 0 is constrained T 0 = 21.14+1.02 -1.34 K, which is slightly lower than T 0 = 24.4±1.9 K measured by the Planck collaboration. The halo mass that gives the most efficient star formation is around 1011.79+0.73 -0.86 M ⊙. From the model parameters, combined with the SFR density at z = 0 synthesized from multi-wavelength observations, we break the degeneracy between SED and SFR and recover the cosmic star formation history that is consistent with multi-wavelength surveys. We also constrain the graybody SED model in agreement with previous measurements from infrared flux stacking. From the HOD constraints, we derive an increasing trend of galaxy linear bias along redshifts that agrees with the results from cross- and auto-correlation with unWISE galaxies. This study indicates the power of using CIB-galaxy cross-correlation to study star formation, dust, and abundance of galaxies across cosmic time.

Investigations of Massive Filaments and Star Formation (INFANT). I. Core Identification and Core Mass Function

Filamentary structures are ubiquitously found in high-mass star-forming clouds. To investigate the relationship between filaments and star formation, we carry out the INFANT (Investigations of Massive Filaments and Sar Formation) survey, a multiscale, multiwavelength survey of massive filamentary clouds with Atacama Large Millimeter/submillimeter Array (ALMA) band 3/band 6 and Very Large Array K band. In this first paper, we present the ALMA band 6 continuum observations toward a sample of eight high-mass star-forming filaments. We covered each target with an approximately rectangular mosaic field of view with two 12 m array configurations, achieving an angular resolution of ∼0.″6 (2700 au at 4.5 kpc) and a continuum rms of ∼0.1 mJy beam−1 (∼0.06 M ⊙ in gas mass assuming 15 K). We identify cores using the getsf and astrodendro and find the former is more robust in terms of both identification and measuring flux densities. We identify in total 183 dense cores (15–36 cores in each cloud) and classify their star formation states via outflow and warm gas tracers. The protostellar cores are statistically more massive than the prestellar cores, possibly indicating further accretion onto cores after the formation of protostars. For the high-mass end ( Mcore > 1.5 M ⊙) of the core mass function (CMF) we derive a power-law index of −1.15 ± 0.12 for the whole sample and −1.70 ± 0.25 for the prestellar population. We also find a steepening trend in CMF with cloud evolution (−0.89 ± 0.15 for the young group versus. −1.44 ± 0.25 for the evolved group) and discuss its implications for cluster formation.

Reconstructing the mid-infrared spectra of galaxies using ultraviolet to submillimeter photometry and Deep Generative Networks

The mid-infrared spectra of galaxies are rich in features such as the Polycyclic Aromatic Hydrocarbon (PAH) and silicate dust features which give valuable information about the physics of galaxies and their evolution. For example they can provide information about the relative contribution of star formation and accretion from a supermassive black hole to the power output of galaxies. However, the mid-infrared spectra are currently available for a very small fraction of galaxies that have been detected in deep multi-wavelength surveys of the sky. In this paper we explore whether Deep Generative Network methods can be used to reconstruct mid-infrared spectra in the 5–35μm range using the limited multi-wavelength photometry in ∼20 bands from the ultraviolet to the submillimeter which is typically available in extragalactic surveys. For this purpose we use simulated spectra computed with a combination of radiative transfer models for starbursts, active galactic nucleus (AGN) tori and host galaxies. We find that our method using Deep Generative Networks, namely Generative Adversarial Networks and Generative Latent Optimization models, can efficiently produce high quality reconstructions of mid-infrared spectra in ∼ 60% of the cases. We discuss how our method can be improved by using more training data, photometric bands, model parameters or by employing other generative networks.

Mapping the Growth of Supermassive Black Holes as a Function of Galaxy Stellar Mass and Redshift

The growth of supermassive black holes is strongly linked to their galaxies. It has been shown that the population mean black hole accretion rate ( BHAR¯ ) primarily correlates with the galaxy stellar mass (M ⋆) and redshift for the general galaxy population. This work aims to provide the best measurements of BHAR¯ as a function of M ⋆ and redshift over ranges of 109.5 < M ⋆ < 1012 M ⊙ and z < 4. We compile an unprecedentedly large sample with 8000 active galactic nuclei (AGNs) and 1.3 million normal galaxies from nine high-quality survey fields following a wedding cake design. We further develop a semiparametric Bayesian method that can reasonably estimate BHAR¯ and the corresponding uncertainties, even for sparsely populated regions in the parameter space. BHAR¯ is constrained by X-ray surveys sampling the AGN accretion power and UV-to-infrared multiwavelength surveys sampling the galaxy population. Our results can independently predict the X-ray luminosity function (XLF) from the galaxy stellar mass function (SMF), and the prediction is consistent with the observed XLF. We also try adding external constraints from the observed SMF and XLF. We further measure BHAR¯ for star-forming and quiescent galaxies and show that star-forming BHAR¯ is generally larger than or at least comparable to the quiescent BHAR¯ .

A Markedly Expanded Sample of Candidate X-Ray-emitting Isolated Neutron Stars

The current sample of 12 radio-quiet isolated neutron stars that emit strongly in X-rays (XINSs) is both small and heterogeneous, limiting its usefulness for understanding the physics of neutron star atmospheres and cooling rates and for constraining the equation of state of neutron degenerate matter. Utilizing the ROSAT 1RXS and 2RXS data sets, in conjunction with the Sloan Digital Sky Survey Data Release 17 and other companion multiwavelength surveys, we have extended previous searches for blank-field X-ray source candidate XINSs, ultimately recovering two known XINSs while identifying 46 new, unstudied candidate fields devoid of likely multiwavelength counterparts. In this publication, we describe our selection approach and provide detailed information regarding our sample of new candidate XINSs. Future opportunities to verify or to refute these X-ray sources as isolated neutron stars by obtaining more accurate X-ray source positions, quality X-ray spectra, or deeper optical imaging are also discussed.

Licking the plate: Dusty star-forming galaxies buried in the ALMA calibration data

Deep, unbiased surveys are essential to decipher the cosmic evolution of galaxies. The submillimetre (submm) and millimetre (mm) windows complement the UV/optical waveband and are key to revealing the cold and dusty Universe. Traditional ways of conducting deep surveys resort to either lensed fields or target small areas for ultra-long integrations. These surveys have greatly advanced our understanding of dusty star-forming galaxies (DSFGs), but are susceptible to lensing uncertainties and cosmic variance and will be expensive to expand. Here, we summarise our recent multi-wavelength survey of DSFGs in the vicinity of ALMA’s calibrators: the ALMACAL survey. These fields have accumulated many hundreds of hours of on-source time, reaching depths and effective areas that are competitive with bespoke cosmological surveys. We summarise the multi-wavelength number counts from ALMACAL and the resolved fraction of the Cosmic Infrared Background (CIB) from submm to mm wave-lengths. Meanwhile, combining all available ALMA observations in each field results in impressive frequency coverage, which often yields the redshifts of these DSFGs. The ALMACAL survey has demonstrated the scientific value of calibration scans for all submm/mm and radio telescopes, existing and planned.

An observationally driven multifield approach for probing the circum-galactic medium with convolutional neural networks

ABSTRACT The circum-galactic medium (CGM) can feasibly be mapped by multiwavelength surveys covering broad swaths of the sky. With multiple large data sets becoming available in the near future, we develop a likelihood-free Deep Learning technique using convolutional neural networks (CNNs) to infer broad-scale physical properties of a galaxy’s CGM and its halo mass for the first time. Using CAMELS (Cosmology and Astrophysics with MachinE Learning Simulations) data, including IllustrisTNG, SIMBA, and Astrid models, we train CNNs on Soft X-ray and 21-cm (H i) radio two-dimensional maps to trace hot and cool gas, respectively, around galaxies, groups, and clusters. Our CNNs offer the unique ability to train and test on ‘multifield’ data sets comprised of both H i and X-ray maps, providing complementary information about physical CGM properties and improved inferences. Applying eRASS:4 survey limits shows that X-ray is not powerful enough to infer individual haloes with masses log (Mhalo/M⊙) &amp;lt; 12.5. The multifield improves the inference for all halo masses. Generally, the CNN trained and tested on Astrid (SIMBA) can most (least) accurately infer CGM properties. Cross-simulation analysis – training on one galaxy formation model and testing on another – highlights the challenges of developing CNNs trained on a single model to marginalize over astrophysical uncertainties and perform robust inferences on real data. The next crucial step in improving the resulting inferences on the physical properties of CGM depends on our ability to interpret these deep-learning models.

Hunting Gamma-Ray-emitting FR0 Radio Galaxies in Wide-field Sky Surveys

Abstract The latest entry in the jetted active galactic nuclei (AGN) family is the Fanaroff–Riley type 0 (FR0) radio galaxies. They share several observational characteristics, e.g., nuclear emission and host galaxy morphology, with FR I sources; however, they lack extended, kiloparsec-scale radio structures, which are the defining features of canonical FR I and II sources. Here we report the identification of seven γ-ray-emitting AGN as FR0 radio sources by utilizing the high-quality observations delivered by ongoing multiwavelength wide-field sky surveys, e.g., Very Large Array Sky Survey. The broadband observational properties of these objects are found to be similar to their γ-ray undetected counterparts. In the γ-ray band, FR0 radio galaxies exhibit spectral features similar to more common FR I and II radio galaxies, indicating a common γ-ray production mechanism and the presence of misaligned jets. Although the parsec-scale radio structure of FR0s generally exhibits a wide range, with about half having emission on opposite sides of the core, the γ-ray-detected FR0s tend to have dominant cores with core-jet structures. We conclude that dedicated, high-resolution observations are needed to unravel the origin of relativistic jets in this enigmatic class of faint yet numerous population of compact radio sources.

The effect of cluster dynamical state on ram-pressure stripping

ABSTRACT Theoretical and observational studies have suggested that ram-pressure stripping (RPS) by the intracluster medium can be enhanced during cluster interactions, boosting the formation of the ‘jellyfish’ galaxies. In this work, we study the incidence of galaxies undergoing RPS in 52 clusters of different dynamical states. We use optical data from the WINGS/OmegaWINGS surveys and archival X-ray data to characterize the dynamical state of our cluster sample, applying eight different proxies. We then compute the number of RPS candidates relative to the infalling population of blue late-type galaxies within a fixed circular aperture in each cluster. We find no clear correlation between the fractions of RPS candidates and the different cluster dynamical state proxies considered. These fractions also show no apparent correlation with cluster mass. To construct a dynamical state classification closer to a merging ‘sequence’, we perform a visual classification of the dynamical states of the clusters, combining information available in optical, X-ray, and radio wavelengths. We find a mild increase in the RPS fraction in interacting clusters with respect to all other classes (including post-mergers). This mild enhancement could hint at a short-lived enhanced RPS in ongoing cluster mergers. However, our results are not statistically significant due to the low galaxy numbers. We note this is the first homogeneous attempt to quantify the effect of cluster dynamical state on RPS using a large cluster sample, but even larger (especially wider) multiwavelength surveys are needed to confirm the results.

Large-scale clustering of buried X-ray AGN: Trends in AGN obscuration and redshift evolution

Aims. In order to test active galactic nucleus (AGN) unification and evolutionary models, we measured the AGN clustering properties as a function of AGN obscuration defined in terms of hydrogen column density, NH. In addition to measuring the clustering of unobscured (NH &lt; 1022 cm−2) and moderately obscured (1022 ≤ NH &lt; 1023.5) AGNs, we also targeted highly obscured sources (NH ≥ 1023.5) up to redshifts of z = 3. Methods. We have compiled one of the largest samples of X-ray-selected AGNs from a total of eight deep XMM/Chandra and multiwavelength surveys. We measured the clustering as a function of both AGN obscuration and redshift using the projected two-point correlation function, wp(rp). We modeled the large-scale clustering signal, measured the AGN bias, b(z, NH), and interpreted it in terms of the typical AGN host dark matter halo, Mhalo(z, NH). Results. We find no significant dependence of AGN clustering on obscuration, suggesting similar typical masses of the hosting halos as a function of NH. This result matches expectations of AGN unification models, in which AGN obscuration depends mainly on the viewing angle of the obscuring torus. We measured, for the first time, the clustering of highly obscured AGNs and find that these objects reside in halos with typical mass log Mhalo = 12.98−0.22+0.17[h−1 M⊙] (12.28−0.19+0.13) at low z ∼ 0.7 (high z ∼ 1.8) redshifts. We find that irrespective of obscuration, an increase in AGN bias with redshift is slower than the expectation for a constant halo mass and instead follows the growth rate of halos, known as the passive evolution track. This implies that for those AGNs the clustering is mainly driven by the mass growth rate of the hosting halos and galaxies across cosmic time.

Classification of Blazar Candidates of Unknown Type in Fermi 4LAC by Unanimous Voting from Multiple Machine-learning Algorithms

The Fermi fourth catalog of active galactic nuclei (AGNs) data release 3 (4LAC-DR3) contains 3407 AGNs, out of which 755 are flat spectrum radio quasars (FSRQs), 1379 are BL Lacertae objects (BL Lac objects), 1208 are blazars of unknown (BCUs) type, while 65 are non-AGNs. Accurate categorization of many unassociated blazars still remains a challenge due to the lack of sufficient optical spectral information. The aim of this work is to use high-precision, optimized machine-learning (ML) algorithms to classify BCUs into BL Lac objects and FSRQs. To address this, we selected the 4LAC-DR3 Clean sample (i.e., sources with no analysis flags) containing 1115 BCUs. We employ five different supervised ML algorithms, namely, random forest, logistic regression, XGBoost, CatBoost, and neural network with seven features: photon index, synchrotron-peak frequency, pivot energy, photon index at pivot energy, fractional variability, ν F ν, at synchrotron-peak frequency, and variability index. Combining results from all models leads to better accuracy and more robust predictions. These five methods together classified 610 BCUs as BL Lac objects and 333 BCUs as FSRQs with a classification metric area under the curve >0.96. Our results are significantly compatible with recent studies as well. The output from this study provides a larger blazar sample with many new targets that could be used for forthcoming multiwavelength surveys. This work can be further extended by adding features in X-rays, UV, visible, and radio wavelengths.

Searching for New Supernova Remnant Candidates from the VTSS Survey

The Virginia Tech Spectral Line Survey (VTSS) Galactic Plane Hydrogen-Alpha Survey has the strong ability to search and discover many different types of objects that cannot be identified clearly on red plates and by other Multi-Wavelength Sky Surveys. Here we make a visual search from the VTSS fields with the supportive surveys of Southern Hydrogen-Alpha Sky Survey Atlas (SHASSA) and MDW Hydrogen-Alpha Sky Survey (MDWS) fields, in the Galactic latitude of |b| between -17 ° and 7 ° for several new optical emission nebulae. Seven candidates were chosen as most likely supernova remnant candidates by their physical shapes and the three of all having [SII]/Hα ratio larger than 0.4, found with T100 photometric observations, are considered to be supernova remnant candidates. Comprehensive optical imaging and spectroscopic observations with multi-wavelength observations will help us to identify the types of all these galactic candidates, more precisely.

A Hidden Population of Massive Black Holes in Simulated Dwarf Galaxies

We explore the characteristics of actively accreting massive black holes (MBHs) within dwarf galaxies in the Romulus25 cosmological hydrodynamic simulation. We examine the MBH occupation fraction, X-ray active fractions, and active galactic nucleus (AGN) scaling relations within dwarf galaxies of stellar mass 108 M ⊙ < M star < 1010 M ⊙ out to redshift z = 2. In the local universe, the MBH occupation fraction is consistent with observed constraints, dropping below unity at M star < 3 × 1010 M ⊙, M 200 < 3 × 1011 M ⊙. Local dwarf AGN in Romulus25 follow observed scaling relations between AGN X-ray luminosity, stellar mass, and star formation rate, though they exhibit slightly higher active fractions and number densities than comparable X-ray observations. Since z = 2, the MBH occupation fraction has decreased, the population of dwarf AGN has become overall less luminous, and as a result the overall number density of dwarf AGN has diminished. We predict the existence of a large population of MBHs in the local universe with low X-ray luminosities and high contamination from X-ray binaries and the hot interstellar medium that are undetectable by current X-ray surveys. These hidden MBHs make up 76% of all MBHs in local dwarf galaxies and include many MBHs that are undermassive relative to their host galaxy’s stellar mass. Their detection relies on not only greater instrument sensitivity but also better modeling of X-ray contaminants or multiwavelength surveys. Our results indicate that dwarf AGN were substantially more active in the past, despite having low luminosity today, and that future deep X-ray surveys may uncover many hidden MBHs in dwarf galaxies out to at least z = 2.

Detectability of wandering intermediate-mass black holes in the Milky Way galaxy from radio to x-rays

ABSTRACT Intermediate-mass black holes (IMBHs, $10^{3\!-\!6} \, {\rm M_\odot }$), are typically found at the centre of dwarf galaxies and might be wandering, thus far undetected, in the Milky Way (MW). We use model spectra for advection-dominated accretion flows to compute the typical fluxes, in a range of frequencies spanning from radio to X-rays, emitted by a putative population of $10^5 \, {\rm M_\odot }$ IMBHs wandering in five realistic volume-weighted MW environments. We predict that $\sim 27{{\ \rm per\ cent}}$ of the wandering IMBHs can be detected in the X-ray with Chandra, $\sim 37{{\ \rm per\ cent}}$ in the near-infrared with the Roman Space Telescope, $\sim 49{{\ \rm per\ cent}}$ in the sub-mm with CMB-S4, and $\sim 57{{\ \rm per\ cent}}$ in the radio with ngVLA. We find that the brightest fluxes are emitted by IMBHs passing through molecular clouds or cold neutral medium, where they are always detectable. We propose criteria to facilitate the selection of candidates in multiwavelength surveys. Specifically, we compute the X-ray to optical ratio (αox) and the optical to sub-mm ratio, as a function of the accretion rate of the IMBH. We show that at low rates the sub-mm emission of IMBHs is significantly higher than the optical, UV, and X-ray emission. Finally, we place upper limits on the number N• of these objects in the MW: N• &amp;lt; 2000 and N• &amp;lt; 100, based on our detectability expectations and current lack of detections in molecular clouds and cold neutral medium, respectively. These predictions will guide future searches of IMBHs in the MW, which will be instrumental to understanding their demographics and evolution.

Correlations of Dark Matter, Gas, and Stellar Profiles in Dark Matter Halos

Halos of similar mass and redshift exhibit a large degree of variability in their differential properties, such as dark matter, hot gas, and stellar mass density profiles. This variability is an indicator of diversity in the formation history of these dark matter halos that is reflected in the coupling of scatters about the mean relations. In this work, we show that the strength of this coupling depends on the scale at which halo profiles are measured. By analyzing the outputs of the IllustrisTNG hydrodynamical cosmological simulations, we report the radial- and mass-dependent couplings between the dark matter, hot gas, and stellar mass radial density profiles utilizing the population diversity in dark matter halos. We find that for the same mass halos, the scatters in the density of baryons and dark matter are strongly coupled at large scales (r > R 200), but the coupling between gas and dark matter density profiles fades near the core of halos (r < 0.3R 200). We then show that the correlation between halo profile and integrated quantities induces a radius-dependent additive bias in the profile observables of halos when halos are selected on properties other than their mass. We discuss the impact of this effect on cluster abundance and cross-correlation cosmology with multiwavelength cosmological surveys.

X-ray selected narrow-line active galactic nuclei in the COSMOS field: Nature of optically dull active galactic nuclei

Abstract X-ray emission detection in a galaxy is one of the efficient tools for selecting active galactic nuclei (AGNs). However, many X-ray-selected AGNs are not easily selected as AGNs by their optical emission. These galaxies, so-called optically dull (OD) AGNs, are fascinating since their X-ray emission is bright even though the AGN signature in the optical regime is absent. In a deep multiwavelength survey over 2 deg2 of the Cosmic Evolution Survey (COSMOS) field, we have looked for the OD AGNs using photometric, spectroscopic, and X-ray data. We identified 310 non-broad line sources with optical spectra as AGNs using X-ray selection up to redshift z ∼ 1.5. We inspected the spectra to check for any AGN signature in their optical emission lines: [Ne v] forbidden emission line, Mass Excitation diagram (MEx), color excitation diagram (TBT), and excess in [O ii] emission line. Finally, we found 48 AGNs that show AGN signatures in the optical spectrum, classified as narrow-line AGN, and 180 AGNs that did not show any AGN signature as the OD AGN sample. Simple explanations of the nature of OD AGNe are a bright host galaxy that dilutes the AGN light or dust materials obscuring the AGN light. We found that the bright host galaxy dilution explains nearly $70\%$ of our OD AGN sample. At the same time, the dust material obscuration is unlikely to be the main reason. By estimating the Eddington ratio, we also found that 95 out of 180 of our OD AGNs have a lower accretion rate, (λEdd) ≲ 10−2, than the typical AGN value. We expected the lower accretion rate sources that suffer from neither host galaxy dilution nor obscuration to have radiatively inefficient flow (RIAF) in their accretion disk. Finally, nine sources have been identified to be most likely hosts of the RIAF disk.