分类： 天文学 >> 天文学 提交时间： 2023-02-19
Wei Yan
Ryan C. Hickox
Chien-Ting J. Chen
Claudio Ricci
Alberto Masini
Franz E. Bauer
David M. Alexander
摘要： In active galactic nuclei (AGN), fluorescent Fe K$\alpha$ (iron) line
emission is generally interpreted as originating from obscuring material around
a supermassive black hole (SMBH) on the scale of a few parsecs (pc). However,
recent Chandra studies indicate the existence of iron line emission extending
to kpc scales in the host galaxy. The connection between iron line emission and
large-scale material can be spatially resolved directly only in nearby
galaxies, but could be inferred in more distant AGNs by a connection between
line emission and star-forming gas and dust that is more extended than the
pc-scale torus. Here we present the results from a stacking analysis and X-ray
spectral fitting performed on sources in the Chandra Deep Field South (CDFS) 7
Ms observations. From the deep stacked spectra, we select sources with stellar
mass $\log(M_*/M_\odot)>10$ at $0.5
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shrey. Ansh
Chien-Ting J. Chen
W. N. Brandt
Carol E. Hood
E. S. Kammoun
G. Lansbury
Stéphane Paltani
Amy E. Reines
C. Ricci
Douglas A. Swartz
Jonathan R. Trump
F. Vito
Ryan C. Hickox
摘要： We present a multi-wavelength analysis of the dwarf Seyfert-2 galaxy J$144013+024744$, a candidate obscured active galactic nucleus (AGN) thought to be powered by an intermediate-mass black hole (IMBH, $M_\bullet \approx 10^{4-6} M_\odot$) of mass $M_{\bullet} \sim 10^{5.2}M_\odot$. To study its X-ray properties, we targeted J$144013+024744$ with NuSTAR for $\approx 100$ ks. The X-ray spectrum was fitted with absorbed power law, Pexmon and a physical model (RXTorus). A Bayesian X-ray analysis was performed to estimate the posteriors. The phenomenological and the physical models suggest the AGN to be heavily obscured by a column density of $N_{\rm H} = (3.4-7.0)\times10^{23}$ cm$^{-2}$. In particular, the RXTorus model with a sub-solar metallicity suggests the obscuring column to be almost Compton-thick. We compared the $2-10$ keV intrinsic X-ray luminosity with the inferred X-ray luminosities based on empirical scaling relations for unobscured AGNs using $L_{\rm [OIV](25.89\mu {\rm m})}$, $L_{[{\rm OIII}](5007 {\rm angstrom})}$, and $L_{6\rm \mu m}$ and found that the high-excitation $[{\rm OIV}]$ line provides a better estimate of the intrinsic $2-10$ keV X-ray luminosity ($L_{2-10}^{\rm int} \sim 10^{41.41}{\rm erg s}^{-1}$). Our results suggest that J$144013+024744$ is the first type-2 dwarf galaxy that shows X-ray spectroscopic evidence for obscuration. The column density that we estimated is among the highest measured to date for IMBH-powered AGNs, implying that a typical AGN torus geometry might extend to the low-mass end. This work has implications for constraining the black hole occupation fraction in dwarf galaxies using X-ray observations.
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