Continuum Region Research Articles

The Spatial Correlation between CN-line- and Dust-continuum-emitting Regions in High-mass Star-forming Clouds

Measuring the strength of a three-dimensional (3D) magnetic field vector is challenging as it is not easy to recognize whether its line-of-sight (LOS) and plane-of-sky (POS) components are obtained from the same region. CN (N = 1–0) emission has been used to get the LOS component of a magnetic field (B LOS) from its Zeeman splitting lines, while dust continuum emission has been used to get the POS component of a magnetic field (B POS). We use the CN (N = 1–0) data observed with the Taeduk Radio Astronomy Observatory 14 m telescope and the dust continuum data from the Herschel archive toward six high-mass star-forming regions in order to test whether CN line and dust continuum emission can trace a similar region and thus can be used for inferring 3D magnetic field strength. Our comparison between CN and H2 column densities for all targets indicates that CN line emission tends to be strong toward bright continuum regions. The positions of peak CN column densities are particularly well correlated with those of peak H2 column densities, at least over the H2 column density of 8.0 × 1022 cm−2 within one or two telescope beam sizes in all targets, implying that CN-line- and dust-continuum-emitting regions are likely spatially coincident. This enabled us to make the reliable measurement of the 3D magnetic field strengths of five targets by taking a vector sum of their B LOS and B POS, helping to decide the magnetical criticality of the targets as supercritical or transcritical.

MUSE spectroscopy of the high abundance discrepancy planetary nebula NGC\,6153

The abundance discrepancy problem in planetary nebulae (PNe) has long puzzled astronomers. NGC\,6153, with its high abundance discrepancy factor (ADF sim 10), provides a unique opportunity to study the chemical structure and ionisation processes within these objects. We aim to understand the chemical structure and ionisation processes in this high-ADF nebula by constructing detailed emission line maps and examining variations in electron temperature and density. This study also explores the discrepancies between ionic abundances derived from collisional and recombination lines, shedding light on the presence of multiple plasma components. We used the MUSE spectrograph to acquire IFU data covering the wavelength range 4600$-$9300 with a spatial sampling of 0.2 arcsec and spectral resolutions ranging from R = 1609 to R = 3506. We created emission line maps for 60 lines and two continuum regions. We developed a tailored methodology for the analysis of the data, including correction for recombination contributions to auroral lines and the contributions of different plasma phases. Our analysis confirmed the presence of a low-temperature plasma component in NGC\,6153. We find that electron temperatures derived from recombination line and continuum diagnostics are significantly lower than those derived from collisionally excited line diagnostics. Ionic chemical abundance maps were constructed, considering the weight of the cold plasma phase in the emission. Adopting this approach we found ionic abundances that could be up to 0.2 dex lower for those derived from CELs and up to 1.1 dex higher for those derived from RLs than in the case of a homogeneous emission. The abundance contrast factor (ACF) between both plasma components was defined, with values, on average, 0.9 dex higher than the ADF. Different methods for calculating ionisation correction factors (ICFs), including state-of-the-art literature ICFs and machine learning techniques, yielded consistent results. Our findings emphasise that accurate chemical abundance determinations in high-ADF PNe must account for multiple plasma phases. Future research should focus on expanding this methodology to a broader sample of PNe, with spectra deep enough to gather physical condition information of both plasma components, which will enhance our understanding of their chemical compositions and the underlying physical processes in these complex objects.

ASKAP-EMU Radio Emission from Type Ic Supernova SN1996aq in NGC 5584

We report the Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe survey detection of radio continuum emission from SN1996aq, a Type Ic supernova within the nearby face-on spiral galaxy NGC 5584. Analysis at multiple radio frequencies reveals radio emission coincident with SN1996aq. We find a flatter radio spectral index compared to the 2009 observations, indicating rapid evolution of SN1996aq. Conversely, no radio emission is observed from NGC 5584’s other known supernova, SN2007af. Furthermore, we identified two other significant radio continuum regions with properties consistent with H ii regions.

Lyman Continuum Emission from Active Galactic Nuclei at 2.3 ≲ z ≲ 3.7 in the UVCANDELS Fields

We present the results of our search for Lyman continuum (LyC)-emitting (weak) active galactic nuclei (AGN) at redshifts 2.3 ≲ z ≲ 4.9 from Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) F275W observations in the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (UVCANDELS) fields. We also include LyC emission from AGN using HST WFC3 F225W, F275W, and F336W imaging found in Early Release Science (ERS) and Hubble Deep UV Legacy Survey data. We performed exhaustive queries of the Vizier database to locate AGN with high-quality spectroscopic redshifts. In total, we found 51 AGN that met our criteria within the UVCANDELS and ERS footprints. Out of these 51, we find 12 AGN that had ≥4σ detected LyC flux in the WFC3/UVIS images. Using a wide variety of space-based plus ground-based data, ranging from X-ray to radio wavelengths, we fit the multiwavelength photometric data of each AGN to a CIGALE spectral energy distribution (SED) using AGN models and correlate various SED parameters to the LyC flux. Kolmogorov–Smirnov tests of the SED parameter distributions for the LyC-detected and nondetected AGN showed they are likely not distinct samples. However, we find that the X-ray luminosity, star formation onset age, and disk luminosity show strong correlations relative to their emitted LyC flux. We also find strong correlations of the LyC flux to several dust parameters, i.e., polar and toroidal dust emission and 6 μm luminosity, and anticorrelations with metallicity and A FUV. We simulate the LyC escape fraction (f esc) using the CIGALE and intergalactic medium transmission models for the LyC-detected AGN and find an average f esc ≃ 18%, weighted by uncertainties. We stack the LyC fluxes of subsamples of AGN according to the wavelength continuum region in which they are detected and find no significant distinctions in their LyC emission, although our submillimeter-detected F336W sample (3.15 < z < 3.71) shows the brightest stacked LyC flux. These findings indicate that LyC production and escape in AGN are more complicated than the simple assumption of thermal emission and a 100% escape fraction. Further testing of AGN models with larger samples than presented here is needed.

Total absorption spectrum of benzene aggregates obtained from two different approaches.

The study of molecular aggregation effects on the electronic spectrum is essential for the development of optoelectronic devices. However, investigating the entire valence absorption spectrum of aggregates using quantum mechanical methods is a challenging task. In this work, we perform systematic simulations of the absorption spectrum of benzene molecular clusters up to 35 eV applying two approaches based on time-dependent density functional theory. The results show that depending on the dimer packing, different energy shifts occur for the symmetry allowed [Formula: see text] transition, in comparison to the monomer. The transition intensity increases for the band around 6 eV for larger aggregates from the monomer to dimers and tetramer, indicating the occurrence of the symmetry forbidden (in [Formula: see text] point group) [Formula: see text] [Formula: see text] transition. The benzene crystal exhibits a large redshift following the experimental spectrum. Also, the continuum regions of all spectra show a good agreement with the experiments both in gas and solid phases. Geometry optimization of the monomer was carried out with Gaussian 09 software using the PBE0/def2-TZVP level of theory. We used dimers and tetramer molecular geometries extracted from the experimental crystal structure. The absorption spectra were directly obtained by the Liouville-Lanczos TDDFT approach with plane waves basis set or indirectly by TDDFT pseudo-spectra calculated in a [Formula: see text] basis followed by analytic continuation procedure to obtain complex polarizability. The former is available at Quantum ESPRESSO, and the latter was calculated using Gaussian 09 with the post-processing performed with a code previously developed in our group.

Spectral Variability Studies in Active Galactic Nuclei: Exploring Continuum and Emission Line Regions in the Age of LSST and JWST

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 the 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.

Investigation on the mercury nucleation mechanism based on the release characteristics of inhalable particles during coupled combustion of sewage sludge-coal washery tailing

Establishing an integrated treatment technology system for sewage sludge and coal washery tailing by mixed combustion can effectively overcome the disadvantages of the low calorific value and utilization efficiency, realizing the efficient resource. The single-component and coupled fuel were analyzed. Aiming at the generated inhalable particulate matter during the combustion process, using multiple characterization means and the fluidized bed experimental system, the micro-characteristics and elemental distribution of coupled fuel and combustion products were obtained, and the theory based on nucleation control was analyzed to reveal particle size distribution and particulate matter emission characteristics under multiparameter coupling conditions. The nucleation mechanism of Hg on the surface of the particulate matter under mixed combustion conditions was clarified. The results show that the weight loss process of sewage sludge in the combustion process mainly includes four stages. An obvious boundary between the volatilization and combustion processes of fixed carbon does not exist; furthermore, there is some overlap between the two processes. Volatiles and minerals interact in the mixed combustion process. The constituent elements of PM1 and PM1∼10 in the generated particulate matter are mainly easily vaporizable and refractory elements, respectively. The particle size of the particles produced presents the characteristics of bimodal distribution. There is a critical value (800 °C) for the influence of combustion temperature on the emission characteristics of particulate matter. It mainly affects the emission characteristics of coarse and fine particles through dominating the occurrence forms of tar, easily gasified and refractory elements, and the collision and aggregation process between particles. Homogeneous nucleation and heterogeneous condensation are the basic pathways for the transition of Hg from the gas phase to particle nucleation, and there are different nucleation control mechanisms. The heterogeneous condensation process includes diffusion control and surface reaction control. In addition, after the coupled fuel is demineralized by acid washing, the nucleation control mechanism changes significantly from diffusion control to chemical reaction control for the particles in the continuum region.

The connection between the escape of ionizing radiation and galaxy properties at z ∼ 3 in the Keck Lyman continuum spectroscopic survey

ABSTRACT The connection between the escape fraction of ionizing radiation (fesc) and the properties of galaxies, such as stellar mass ($\rm M_{\rm *}$), age, star-formation rate (SFR), and dust content, are key inputs for reionization models, but many of these relationships remain untested at high redshift. We present an analysis of a sample of 96 $z$ ∼ 3 galaxies from the Keck Lyman Continuum Spectroscopic Survey (KLCS). These galaxies have both sensitive Keck/LRIS spectroscopic measurements of the Lyman continuum (LyC) region, and multiband photometry that places constraints on stellar population parameters. We construct composite spectra from subsamples binned as a function of galaxy property and quantify the ionizing-photon escape for each composite. We find a significant anti-correlation between fesc and $\rm M_{\rm *}$, consistent with predictions from cosmological zoom-in simulations. We also find significant anti-correlation between fesc and E(B−V), encoding the underlying physics of LyC escape in our sample. We also find no significant correlation between fesc and either stellar age or specific SFR (= SFR/$\rm M_{\rm *}$), challenging interpretations that synchronize recent star formation and favorable conditions for ionizing escape. The galaxy properties now shown to correlate with fesc in the KLCS are Lyα equivalent width, UV Luminosity, $\rm M_{\rm *}$, SFR, and E(B−V), but not age or sSFR. This comprehensive analysis of galaxy properties and LyC escape at high redshift will be used to guide future models and observations of the reionization epoch.

Estimating reddening of the continuum and broad-line region of active galactic nuclei: the mean reddening of NGC 5548 and the size of the accretion disc

ABSTRACT We use seven different methods to estimate broad-line and continuum reddenings of NGC 5548. We investigate two possible reddening curves considered for active galactic nuclei (AGNs): the mean AGN reddening curve of Gaskell &amp; Benker (2007) which is relatively flat in the ultraviolet, and a curve that rises strongly into the ultraviolet like a Small Magellanic Cloud (SMC) reddening curve. We also consider a standard Milky Way curve. Regardless of the curve adopted, we find a total reddening ∼14 times greater than the small amount of reddening due to dust in the solar neighbourhood. The UV-to-optical ratios rule out a steep SMC-like reddening curve for NGC 5548. The Milky Way and Gaskell &amp; Benker curves give a mean reddening of E(B − V) = 0.25 ± 0.02. The four non-hydrogen-line reddening indicators imply that the intrinsic hydrogen line ratios are consistent with Baker–Menzel case B values. The unreddened optical to UV spectral energy distribution is consistent with the predicted distribution for an externally-illuminated accretion disc. The reddening we derive for NGC 5548 is typical of previous estimates for type-1 AGNs. Neglecting internal extinction leads to an underestimate of the luminosity at 1200 Å by a factor of seven. The size scale of the accretion disc has therefore been underestimated by a factor of ≈2.6. This is similar to the accretion disc size discrepancy found in the 2013 AGNSTORM campaign and thus supports the proposal by Gaskell (2017) that the accretion disc size discrepancy is primarily due to the neglect of reddening.

Численный анализ динамики молекулярного газа при импульсной лазерной абляции

The evaporation of a molecular gas with rotational degrees of freedom caused by the action of a pulsed nanosecond laser (pulsed laser ablation) of moderate intensity is considered. Model kinetic equations that account for the exchange of translational and rotational energies using a two-temperature model are used to account for the influence of internal energy on the vapor-gas cloud dynamics. Rykov equations (R-model) are integrated when modeling the flow of a diatomic gas, and a generalization of the Bhatnagar-Gross-Krook (BGK) equation for a molecular gas is used to calculate the flow of nonlinear molecules with a number of rotational degrees of freedom equal to three. Taking into account the influence of internal energy on the gas flow is realized by relaxation terms approximating the collision integral as a sum of elastic and inelastic collisions. Since in the model kinetic equations the collision frequency does not depend on the velocities, and the influence of internal energy is taken into account only due to temperature changes, it is necessary to compare with more realistic approaches, which include, for example, the method of direct simulation Monte Carlo (DSMC). The comparison shows that the change in the average temperature over time and the vapor-gas cloud parameters (density and temperature), obtained by the solution of the kinetic equations and the DSMC method, are close. Calculations of the problem of pulsed laser ablation by direct integration of kinetic equations are carried out by the method of discrete ordinates and are a difficult computational problem, which is associated with discontinuous boundary conditions, the presence of both continuum regions and free molecular flow regions in the solution, as well as the need to calculate the vapor-gas cloud dynamics for a large time interval. To reduce computational costs, grid adaptation in physical and velocity spaces is used.

Bottom quark mass with calibrated uncertainty

We determine the bottom quark mass {hat{m}}_b from QCD sum rules of moments of the vector current correlator calculated in perturbative QCD to {{mathcal {O}}} ({hat{alpha }}_s^3). Our approach is based on the mutual consistency across a set of moments where experimental data are required for the resonance contributions only. Additional experimental information from the continuum region can then be used for stability tests and to assess the theoretical uncertainty. We find {hat{m}}_b({hat{m}}_b) = (4180.2 pm 7.9) MeV for {hat{alpha }}_s(M_Z) = 0.1182.

Three-dimensional multiscale modeling of nanoindentation

Concurrent multiscale methods have been developed to reduce the degrees of freedom and reduce the effects of boundary conditions on the results of atomic simulations. In this paper, two simplified concurrent multiscale methods, one with handshake region and another without handshake region are used to investigate the nanoindentation process on a single crystal of Al at room temperature. The multiscale models are validated by observing reasonably well similarities in the load–depth curves obtained from multiscale and full MD simulations. Refining the element size down to atomic spacing resulted in high computational efforts while the analysis results do not improve significantly. Also, it is shown that by defining the thermostat in the atomistic part, wave reflections are eliminated at the interface of atomic and continuum domains. It is shown that by selecting appropriate dimensions of the atomic domain, there is no need to use nonlinear elasticity in the continuum region. Also, hardness is more affected by sample size than the elastic modulus.

Transmitting multiple high-frequency phonons across length scales using the concurrent atomistic–continuum method

Coupled atomistic–continuum methods can describe large domains and model dynamic material behavior for a much lower computational cost than traditional atomistic techniques. However, these multiscale frameworks suffer from wave reflections at the atomistic–continuum interfaces due to the numerical discrepancy between the fine-scaled and coarse-scaled models. Such reflections are non-physical and may lead to unfavorable outcomes such as artificial heating in the atomistic region. In this work, we develop a technique to allow the full spectrum of phonons to be incorporated into the coarse-scaled regions of a periodic concurrent atomistic–continuum (CAC) framework. This scheme tracks phonons generated at various time steps and thus allows multiple high-frequency wave packets to travel between the atomistic and continuum regions. Simulations performed with this method demonstrate the ability of the technique to preserve the coherency of waves with a range of wavevectors as they propagate through the domain. This work has applications for systems with defined boundary conditions and may be extended to more complex problems involving waves randomly nucleated from an impact within a multiscale framework.

Non-solar abundance ratios trends of dEs in the Fornax Cluster using newly defined high-resolution indices

ABSTRACT We perform a detailed study of the stellar populations in a sample of massive Fornax dwarf galaxies using a set of newly defined line indices. Using data from the Integral Field Spectroscopic data, we study abundance ratios of eight dEs with stellar mass ranging from 108 to 109.5 M⊙ in the Fornax Cluster. We present the definitions of a new set of high-resolution Lick-style indices to be used for stellar population studies of unresolved small stellar systems. We identify 23 absorption features and continuum regions, mainly dominated by 12 elements (Na, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Y, Ba, and Nd) in the wavelength range 4700–5400 Å and characterize them as a function of age, metallicity, and alpha element abundance ratios. We analyse eight dEs and interpret the line strengths, measured in our new high-resolution system of indices, with the aid of stellar population models with high enough spectral resolution. We obtain abundance ratio proxies for a number of elements that have never been studied before for dwarf ellipticals outside the Local Group. These proxies represent relative deviations from predicted index strengths of base stellar population models built-up following the abundance pattern of The Galaxy. The abundance proxy trend results are compared to abundance ratios from resolved stars in the Local Group, and indices from integrated light of larger early-type galaxies. We find that all our dwarfs show a pattern of abundance ratios consistent with the disc of the Milky Way, indicative of slow formation in comparison to their high-mass counterparts.

The photon content of the proton in the CT18 global analysis

Recently, two photon PDF sets based on implementations of the LUX ansatz into the CT18 global analysis were released. In CT18lux, the photon PDF is calculated directly using the LUX master formula for all scales, \muμ. In an alternative realization, CT18qed, the photon PDF is initialized at the starting scale, \mu_0μ0, using the LUX formulation and evolved to higher scales \mu(&gt;\mu_0)μ(&gt;μ0) with a combined QED+QCD kernel at \mathcal{O}(\alpha),~\mathcal{O}(\alpha\alpha_s)𝒪(α),𝒪(ααs) and \mathcal{O}(\alpha^2)𝒪(α2). In the small-xx region, the photon PDF uncertainty is mainly induced by the quark and gluon PDFs, through the perturbative DIS structure functions. In comparison, the large-xx photon uncertainty comes from various low-energy, nonperturbative contributions, including variations of the inelastic structure functions in the resonance and continuum regions, higher-twist and target-mass corrections, and elastic electromagnetic form factors of the proton. We take the production of doubly-charged Higgs pairs, (H^{++}H^{--})(H++H−−), as an example of scenarios beyond the Standard Model to illustrate the phenomenological implications of these photon PDFs at the LHC.

Free energy calculation and ghost force correction for hot‐QC

A new efficient variant of hot-QC, the finite temperature version of the quasicontinuum (QC) method, is presented. In the original formulation of hot-QC, a dynamically evolving atomistic region is coupled with either a dynamic (hot-QC-dynamic) or a static (hot-QC-static) continuum region. In the current work, a free energy minimization method is employed in which atom positions in both the atomistic and continuum regions always occupy equilibrium positions. The effect of ghost forces at the interface of the atomistic and continuum regions is discussed for all three variants of hot-QC using two examples: a perfect cubic crystal and a Lomer dislocation dipole. Errors due to ghost forces and due to mesh entropy are considered and the efficacy of their correction terms are evaluated. It is shown that the proposed free energy minimization method has comparable accuracy to the other methods with significantly higher efficiency.

Effect of multiple rescatterings on continuum harmonics from asymmetric molecules in multicycle lasers.

A wide range of harmonics especially continuum harmonics is a prerequisite for attosecond pulse generation. One can use longer-wavelength lasers to push the cutoff to a higher order. However, this does not translate to the same amount of continuum range extension because multiple rescattering phenomena are also enhanced in the process, potentially affecting the lower end of the continuum harmonics. It is then important to understand exactly how multiple rescatterings affect the harmonic structure and their response to various laser parameters, which is the main theme of this paper. Particularly, by applying the synchrosqueezed time-frequency transform and classical electron trajectory analysis to the asymmetric molecule carbon monoxide (CO), we justify that the multiple rescatterings indeed influence the periodicity of the harmonic spectra and the stable periodicity is, in fact, bounded by the first- and third-order returns. Moreover, for the first time, we find that the high-order rescatterings are asymmetric regarding the molecular rotation of 180°, but always correlate with the first-order returns. Our last result is that by breaking the laser symmetry in an appropriate way, the contribution of multiple rescatterings is removed so that the continuum region is entirely defined by the first-order return energies.

Grad's distribution functions-based gas kinetic scheme for simulation of flows beyond Navier–Stokes level

Conventional gas kinetic scheme (GKS) has been successfully utilized to obtain the accurate solution of Navier–Stokes (NS) equations. However, when it comes to flows beyond NS level, the conventional GKS is not reliable because its initial gas distribution function is approximated by the first-order Chapman–Enskog expansion, which merely recovers the NS equations. In order to make an extension for flows beyond NS level, we propose the Grad's distribution functions-based GKS in this paper. This scheme retains the advantage of conventional GKS and constructs the numerical fluxes through a time-dependent gas distribution function, which is derived from the integral solution of Boltzmann equation. In the present scheme, the initial gas distribution function in the local solution of Boltzmann equation is approximated by Grad's 13 and 26 distribution functions. Furthermore, the high-order moments in the initial Grad's distribution function are calculated by moment relationship directly, and thus, the solution of complicated partial differential equations for these high-order moments is avoided. Four benchmark numerical examples are tested to validate the performance of the present scheme, and the results demonstrate that the present scheme can not only recover NS solutions in the continuum region but also predict reasonable results for flows in the slip and transition regimes.

Moving window techniques to model shock wave propagation using the concurrent atomistic–continuum method

Atomistic methods have successfully modeled different aspects of shock wave propagation in materials over the past several decades, but they suffer from limitations which restrict the total runtime and system size. Multiscale methods have been able to increase the length and time scales that can be modeled but employing such schemes to simulate wave propagation and evolution through engineering-scale domains is an active area of research. In this work, we develop two distinct moving window approaches within a Concurrent Atomistic–Continuum (CAC) framework to model shock wave propagation through a one-dimensional monatomic chain. In the first method, the entire CAC system travels with the shock in a conveyor fashion and maintains the shock front in the middle of the overall domain. In the second method, the atomistic region follows the shock by the simultaneous coarsening and refinement of the continuum regions. The CAC and moving window frameworks are verified through dispersion relation studies and phonon wave packet tests. We achieve good agreement between the simulated shock velocities and the values obtained from theory with the conveyor technique, while the coarsen-refine technique allows us to follow the propagating wave front through a large-scale domain. This work showcases the ability of the CAC method to accurately simulate propagating shocks and also demonstrates how a moving window technique can be used in a multiscale framework to study highly nonlinear, transient phenomena.

Evaluation of IMERG satellite precipitation over the land-coast-ocean continuum – Part I: Detection

AbstractAs a fundamental water flux, quantitative understanding of precipitation is important to understand and manage water systems under a changing climate, especially in transition regions such as the coastal interface between land and ocean. This work aims to assess the uncertainty in precipitation detection over the land-coast-ocean continuum in the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) V06B. It is examined over three coastal regions of the U.S., i.e. the West Coast, the Gulf of Mexico, and the East Coast, each of which are characterized by different topographies and precipitation climatologies. Detection capabilities are contrasted over different surfaces (land, coast, ocean). A novel and integrated approach traces the IMERG detection performance back to its components (passive microwave, infrared, and morphing-based estimates). The analysis is performed by using high-resolution, high-quality Ground Validation Multi-Radar/Multi-Sensor (GV-MRMS) rainfall estimates as ground reference. The best detection performances are reported with PMW estimates (hit rates in the range of [25-39]%), followed by morphing ([20-34]%), morphing+IR ([17-27]%) and IR ([11-16]%) estimates. Precipitation formation mechanisms play an important role, especially in the West Coast where orographic processes challenge detection. Further, precipitation typology is shown to be a strong driver of IMERG detection. Over the ocean, IMERG detection is generally better but suffers from false alarms ([10-53]%). Overall, IMERG displays nonhomogeneous precipitation detection capabilities tracing back to its components. Results point toward a similar behavior across various land-coast-ocean continuum regions of the CONUS, which suggests that results can be potentially transferred to other coastal regions of the world.