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Probing the Active Massive Black Hole Candidate in the Center of NGC 404 with VLBI

 dc.contributor.author Paragi, Z dc.contributor.author Frey, S dc.contributor.author Kaaret, P dc.contributor.author Cseh, D dc.contributor.author Overzier, R dc.contributor.author Preethi, K dc.date.accessioned 2014-08-19T05:24:41Z dc.date.available 2014-08-19T05:24:41Z dc.date.issued 2014-08-10 dc.identifier.citation The Astrophysical Journal, Vol. 791, No. 1, 2 en dc.identifier.issn 0004-637X dc.identifier.uri http://hdl.handle.net/2248/6643 dc.description Restricted Access en dc.description.abstract Recently, Nyland et al. argued that the radio emission observed in the center of the dwarf galaxy NGC 404 originates in a low-luminosity active galactic nucleus powered by a massive black hole (MBH, M lsim 106 M ☉). High-resolution radio detections of MBHs are rare. Here we present sensitive, contemporaneous Chandra X-ray, and very long baseline interferometry (VLBI) radio observations with the European VLBI Network. The source is detected in the X-rays, and shows no long-term variability. If the hard X-ray source is powered by accretion, the apparent low accretion efficiency would be consistent with a black hole (BH) in the hard state. Hard state BHs are known to show radio emission compact on the milliarcsecond scales. However, the central region of NGC 404 is resolved out on 10 mas (0.15-1.5 pc) scales. Our VLBI non-detection of a compact, partially self-absorbed radio core in NGC 404 implies that either the BH mass is smaller than $3^{+5}_{-2}\times 10^5$ M ☉, or the source does not follow the fundamental plane of BH activity relation. An alternative explanation is that the central BH is not in the hard state. The radio emission observed on arcsecond (tens of parsecs) scales may originate in nuclear star formation or extended emission due to AGN activity, although the latter would not be typical considering the structural properties of low-ionization nuclear emission-line region galaxies with confirmed nuclear activity. en dc.language.iso en en dc.publisher IOP Publishing en dc.relation.uri http://iopscience.iop.org/0004-637X/791/1/2/ en dc.rights © IOP Publishing en dc.subject Black hole physics en dc.subject Galaxies: active en dc.subject Galaxies: individual (NGC 404) en dc.subject Radio continuum: galaxies en dc.subject X-rays: galaxies en dc.title Probing the Active Massive Black Hole Candidate in the Center of NGC 404 with VLBI en dc.type Article en
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