A Deep Chandra View of the NGC 404 Central Engine

Abstract

We present the results of a 100 ks {\it Chandra} observation of the NGC 404 nuclear region. The long exposure and excellent spatial resolution of {\it Chandra} has enabled us to critically examine the nuclear environment of NGC 404, which is known to host a nuclear star cluster and potentially an intermediate-mass black hole (on the order of a few times $10^5$ \Msun). We find two distinct X-ray sources: a hard, central point source coincident with the optical and radio centers of the galaxy, and a soft extended region that is coincident with areas of high H$\alpha$ emission and likely recent star formation. When we fit the 0.3-8 keV spectra of each region separately, we find the hard nuclear point source to be dominated by a power law (\PL = 1.88), while the soft off-nuclear region is best fit by a thermal plasma model ($kT$ = 0.67 keV). We therefore find evidence for both a power law component and hot gas in the nuclear region of NGC 404. We estimate the 2-10 keV luminosity to be 1.3${}_{-0.5}^{+0.8}\times 10^{37}$ erg s${}^{-1}$. A low-level of diffuse X-ray emission is detected out to $\sim$15\as ($\sim$0.2 kpc) from the nucleus. We compare our results to the observed relationships between power law photon index and Eddington ratio for both X-ray binaries and low luminosity active galaxies and find NGC 404 to be consistent with other low luminosity active galaxies. We therefore favor the conclusion that NGC 404 harbors an intermediate-mass black hole accreting at a very low level.

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Cited by in corpus (12)

• Observational evidence for intermediate-mass black holes
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• The Nuclear Near-Infrared Spectral Properties of Nearby Galaxies
• Investigating the retention of intermediate-mass black holes in star clusters using N-body simulations
• Revolutionizing Our Understanding of AGN Feedback and its Importance to Galaxy Evolution in the Era of the Next Generation Very Large Array
• A Multi-wavelength Study of the Turbulent Central Engine of the Low-mass AGN hosted by NGC404
• Probing the Active Massive Black Hole Candidate in the Center of NGC 404 with VLBI
• Compact jets dominate the continuum emission in low-luminosity active galactic nuclei
• Surprisingly Strong K-band Emission Found in Low Luminosity Active Galactic Nuclei
• X-ray and radio observations of central black holes in nearby low-mass early-type galaxies: Preliminary evidence for low Eddington fractions
• Widespread Shocks in the Nucleus of NGC 404 Revealed by Near-infrared Integral Field Spectroscopy
• The Chandra Local Volume Survey: The X-ray Point Source Population of NGC 404