Hard X-Ray to Radio Multiwavelength SED Analysis of Local U/LIRGs in the GOALS Sample with a Self-consistent AGN Model including a Polar-dust Component

Abstract

We conduct hard X-ray to radio multiwavelength spectral energy distribution (SED) decomposition for 57 local luminous and ultraluminous infrared galaxies observed with the Nuclear Spectroscopic Telescope Array and/or Swift/Burst Alert Telescope in the GOALS sample. We modify the latest SED-fitting code X-CIGALE by implementing the infrared (IR) CLUMPY model, allowing us to conduct the multiwavelength study with the X-ray torus model XCLUMPY self-consistently. Adopting the torus parameters obtained by the X-ray fitting, we estimate the properties of the host galaxies, active galactic nucleus (AGN) tori, and polar dust. The star formation rates (SFRs) become larger with merger stage and most of them are above the main sequence. The SFRs are correlated with radio luminosity, indicating starburst emission is dominant in the radio band. Although polar-dust extinction is much smaller than torus extinction, the UV-to-IR (mainly IR) polar dust luminosities are ∼2 times larger than the torus ones. The polar-dust temperature decreases while the physical size, estimated by the temperature and dust sublimation radius, increases with AGN luminosity from a few tens of parsec (early mergers) to kiloparsec scales (late mergers), where the polar dust likely comes from expanding (i.e., evolving) dusty outflows. A comparison between the SFRs and intrinsic AGN luminosities suggests that starbursts occur first and AGNs arise later, and overall their growth rates follow the simultaneous coevolution local galaxy–SMBH mass relation. We confirm the coexistence of intense starbursts, AGNs, and large-scale outflows in late mergers, supporting a standard AGN feedback scenario.

Coevolution and Nuclear Structure in the Dwarf Galaxy POX 52 Studied by Multiwavelength Data from Radio to X-Ray

“…a These parameters were fixed in the GALFIT fits.θ inc = 20°. A comparison between the SKIRTOR and clumpy torus models was also discussed byYamada et al (2023), and a similar conclusion was drawn by the authors. We note that we relied on the SKIRTOR model in the SED fitting, as it has been generally used in CIGALE and makes it easy to compare our results with other ones.…”

“…It is natural to consider the same torus geometry used in the SED analysis; it is the SKIRTOR torus model, which considers a two-layer structure (Stalevski et al 2016), but there was no X-ray model that was built by considering the geometry. Therefore, we decided to alternatively adopt the clumpy torus structure, whose models were available in both IR and X-ray bands (Miyaji et al 2019;Yamada et al 2023). We adopted the IR one of Nenkova et al (2008a; see also Nenkova et al 2008b) and the X-ray one of Tanimoto et al (2019).…”

[O iv]- and [Ne v]-weak Active Galactic Nuclei Hidden by Compton-thick Material in Late Mergers

“…Among these objects, Yamada et al (2021) identified 57 U/LIRG systems that had been observed with hard X-rays, which totaled 84 individual nuclei in the optical band, and found significant hard X-ray detection from 40 AGNs from these nuclei. Yamada et al (2023) performed hard-X-ray-to-radio SED decomposition for these 57 U/LIRGs (or 72 component sources resolved in the Herschel 70 μm band). They cataloged the intrinsic AGN luminosities for the 40 hard X-ray-detected AGNs in the multiwavelength bands, containing two Herschel-unresolved dual-AGN systems and 36 resolved single AGNs.…”

“…First, we establish useful diagnostics for identifying buried AGNs. Specifically, we employ a similar method to our previous work (Yamada et al 2019) but using, together with [O IV], 12 μm AGN luminosities (designated as L 12,AGN ; e.g., Yamada et al 2023) derived through spectral energy distribution (SED) analysis and also using [Ne V] 14.32 μm data as a supplement. The SED data are much more easily obtained than L 12,nuc .…”

Constraining AGN Torus Sizes with Optical and Mid-infrared Ensemble Structure Functions

“…In this work, we consider a simple geometric model and neglect detailed radiative transfer given that the light-curve quality is insufficient to constrain the complicated physics that could be highly degenerate. Our torus model contains five parameters: the inclination angle (θ = 0°means a face-on view), inner radius R in (in units of parsecs), outer-to-inner radius ratio Y, torus half-opening angle σ, and radial power-law index p. Specifically, since we are measuring the ensemble SF in a narrow wavelength range (λ rest ∼ 1.4-2.8 μm in W1 and λ rest ∼ 2.0-3.8 μm in W2), the clouds are expected to be the hottest dust concentrated near the sublimation radius (T ∼ 1500 K, R  1 pc), as opposed to the polar dust component (T ∼ 100-200 K, R ∼ 100-1000 pc) that dominates the emissions at λ ∼ 20 μm, and contribute little to the W1 and W2 bands (e.g., Hönig et al 2013;Lyu & Rieke 2018;Yamada et al 2023). Therefore, we assume that the torus has a thin-wall geometry by fixing Y to a small value of 1.5 7 and neglect the polar component in our model.…”