NuSTAR observations of four nearby X-ray faint AGNs: low luminosity or heavy obscuration?

Annuar, A.; Alexander, D. M.; Gandhi, P.; Lansbury, G. B.; Asmus, D.; Baloković, Mislav; Ballantyne, D. R.; Bauer, F. E.; Boorman, Peter; Brandt, W. N.; Brightman, Murray; Chen, C.-T. J.; Moro, A. Del; Farrah, D.; Harrison, Fiona A.; Koss, Michael; Lanz, Lauranne; Marchesi, S.; Masini, Alberto; Nardini, E.; Ricci, Cláudio; Stern, Daniel; Zappacosta, L.

doi:10.1093/mnras/staa1820

Cited by 16 publications

(7 citation statements)

References 110 publications

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“…Thus, the baseline model used in this work will lead to robust results that can be easily compared with previous works (e.g. Annuar et al 2015Annuar et al , 2017Annuar et al , 2020Kawamuro et al 2016 ).…”

Section: Baseline Modelsmentioning

confidence: 86%

Observational hints on the torus obscuring gas behaviour through X-rays with NuSTAR data

Osorio-Clavijo¹,

González‐Martín²,

Sánchez-Sánchez

et al. 2021

Monthly Notices of the Royal Astronomical Society

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According to theory, the torus of active galactic nuclei (AGN) is sustained from a wind coming off the accretion disk, and for low efficient AGN, it has been proposed that such structure disappears. However, the exact conditions for its disappearance remain unclear. This can be studied throughout the reflection component at X-rays, which is associated with distant and neutral material at the inner walls of the torus in obscured AGN. We select a sample of 81 AGNs observed with NuSTAR with a distance limit of D< 200 Mpc and Eddington rate $\rm {\lambda _{Edd} \equiv L_{bol}/L_{Edd}<10^{-3}}$. We fit the 3-70 keV spectra using a model accounting for a partial-covering absorber plus a reflection component from neutral material. We find that the existence of the reflection component spans in a wide range of black hole mass and bolometric luminosities, with only ∼13 per cent of our sample (11 sources) lacking of any reflection signatures. These sources fall in the region in which the torus may be lacking in the L-MBH diagram. For the sources with a detected reflection component, we find that the vast majority of them are highly obscured ($\rm {\log \ N_H > 23}$), with $\rm {\sim 20{{\ \rm per\ cent}}}$ being Compton-thick. We also find an increase on the number of unobscured sources and a tentative increase on the ratio between $\rm {FeK\alpha }$ emission line and Compton-hump luminosities toward $\rm {\lambda _{Edd}=10^{-5}}$, suggesting that the contribution of the $\rm {FeK\alpha }$ line changes with Eddington ratio.

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Section: Baseline Modelsmentioning

confidence: 86%

Observational hints on the torus obscuring gas behaviour through X-rays with NuSTAR data

Osorio-Clavijo¹,

González‐Martín²,

Sánchez-Sánchez

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Interestingly, this situation is reminiscent of NGC 3486-as one example-in that a high-excitation line attributed to AGN activity was reported (O VI in NGC 3486 and Ne V in NGC 4178; Satyapal et al 2009;Annuar et al 2020), and an AGN was reported based on soft X-ray emission from XMM-Newton (L 2-10keV = 1.1 × 10 39 erg s −1 in NGC 3486; Cappi et al 2006) or Chandra (L 2-10keV = 7.9 × 10 38 erg s −1 in NGC 4178; Secrest et al 2012) but was not detected in the NuSTAR imaging (Annuar et al 2020, and this work). The major difference in this comparison is that NGC 3486 is detected as a Type II AGN in the optical, whereas NGC 4178 presents as an H II star-forming region.…”

Section: Ngc 4178mentioning

confidence: 93%

NuSTAR Observes Two Bulgeless Galaxies: No Hard X-Ray AGN Detected in NGC 4178 or J0851+3926

Pfeifle¹,

Satyapal²,

Ricci³

et al. 2023

ApJ

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The discovery over the last several decades of low- and moderate-luminosity active galactic nuclei (AGNs) in disk-dominated galaxies—which show no “classical” bulges—suggests that secular mechanisms represent an important growth pathway for supermassive black holes in these systems. We present new follow-up NuSTAR observations of the optically elusive AGNs in two bulgeless galaxies, NGC 4178 and J0851+3926. Galaxy NGC 4178 was originally reported as hosting an AGN based on the detection of [Ne v] mid-infrared emission detected by Spitzer, and based on Chandra X-ray imaging, it has since been argued to host either a heavily obscured AGN or a supernova remnant. Galaxy J0851+3926 was originally identified as an AGN based on its Wide-Field Infrared Survey Explorer mid-IR colors, and follow-up near-infrared spectroscopy previously revealed a hidden broad-line region, offering compelling evidence for an optically elusive AGN. Neither AGN is detected within the new NuSTAR imaging, and we derive upper limits on the hard X-ray 10–24 keV fluxes of <7.41 × 10−14 and <9.40 × 10−14 erg cm−2 s−1 for the AGNs in NGC 4178 and J0851+3926, respectively. If these nondetections are due to large absorbing columns along the line of sight, the nondetections in NGC 4178 and J0851+3926 could be explained with column densities of log(N H/cm2) > 24.2 and 24.1, respectively. The nature of the nuclear activity in NGC 4178 remains inconclusive; it is plausible that the [Ne v] traces a period of higher activity in the past, but that the AGN is relatively quiescent now. The nondetection in J0851+3926 and multiwavelength properties are consistent with the AGN being heavily obscured.

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“…With the exception with the outer most ring, NGC 3486 has one of the most obvious examples of 𝑡 𝑦𝑆 𝑃 decreasing and 𝑓 𝑏𝑢𝑟 𝑠𝑡 increasing with galactocentric radius. The central region is host to a possible Type 2 Seyfert (Ho et al 1997;Annuar et al 2020). The outermost region, although slightly bluer than the intermediate regions, has a similar 𝑡 𝑦𝑆 𝑃 as the intermediate regions.…”

Section: A3 Ngc 3486mentioning

confidence: 99%

A Multi-Wavelength Study of Star Formation in 15 Local Star-Forming Galaxies

Smith,

van Zee,

Salim

et al. 2021

Preprint

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We have fit the far-ultraviolet (FUV) to mid-infrared (MIR) spectral energy distributions (SEDs) for several nearby galaxies (< 20 Mpc). Global, radial, and local photometric measurements are explored to better understand how SED-derived star formation histories (SFHs) and classic star formation rate (SFR) tracers manifest at different scales. Surface brightness profiles and radial SED fitting provide insight into stellar population gradients in stellar discs and haloes. A double exponential SFH model is used in the SED fitting to better understand the distributions of young vs. old populations throughout these galaxies. Different regions of a galaxy often have undergone very different SFHs, either in strength, rate, timing, or some combination of all these factors. An analysis of individual stellar complexes within these galaxies shows a relationship between the ages of stellar clusters and how these clusters are distributed throughout the galaxy. These star formation properties are presented alongside previously published HI observations to provide a holistic picture of a small sample of nearby star-forming galaxies. The results presented here show that there is a wide variety of star formation gradients and average stellar age distributions that can manifest in a ΛCDM universe.

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NuSTAR observations of four nearby X-ray faint AGNs: low luminosity or heavy obscuration?

Cited by 16 publications

References 110 publications

Observational hints on the torus obscuring gas behaviour through X-rays with NuSTAR data

Observational hints on the torus obscuring gas behaviour through X-rays with NuSTAR data

NuSTAR Observes Two Bulgeless Galaxies: No Hard X-Ray AGN Detected in NGC 4178 or J0851+3926

A Multi-Wavelength Study of Star Formation in 15 Local Star-Forming Galaxies

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