NuSTAR Observations of a Heavily X-Ray-obscured AGN in the Dwarf Galaxy J144013+024744

We present a multiwavelength analysis of the dwarf Seyfert 2 galaxy J144013+024744, a candidate obscured active galactic nucleus (AGN) thought to be powered by an intermediate-mass black hole (IMBH, M (& BULL;) & AP; 10(4)-10(6) M (& ODOT;)) of mass M (& BULL;) & SIM; 10(5.2) M (& ODOT;). To study its X-ray properties, we targeted J144013+024744 with NuSTAR for & AP;100 ks. The X-ray spectrum was fitted with an 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 (H) = (3.4-7.0) x 10(23) cm(-2). In particular, the RXTorus model with a subsolar 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 ([Oiv] 25.89 mu m), L ([Oiii] lambda 5007), and L (6 mu m) and found that the high-excitation [Oiv] line provides a better estimate of the intrinsic 2-10 keV X-ray luminosity ( L2-10int & SIM;1041.41 -1). Our results suggest that J144013+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 BH occupation fraction in dwarf galaxies using X-ray observations.