Journal article
Probing the active massive black hole candidate in the center of NGC 404 with VLBI
The Astrophysical journal, Vol.791(1), p.2
07/2014
DOI: 10.1088/0004-637X/791/1/2
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 ≲ 10{sup 6} M{sub ☉}). 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{sub −2}{sup +5}×10{sup 5} M{sub ☉}, 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.
Details
- Title: Subtitle
- Probing the active massive black hole candidate in the center of NGC 404 with VLBI
- Creators
- Z Paragi - Joint Institute for VLBI ERICS FreyP Kaaret - University of IowaD Cseh - Radboud University NijmegenR Overzier - Observatório Nacional, Rua José Cristino, 77. CEP 20921-400, Rio de Janeiro, BrazilP Kharb - Indian Institute of Astrophysics
- Resource Type
- Journal article
- Publication Details
- The Astrophysical journal, Vol.791(1), p.2
- DOI
- 10.1088/0004-637X/791/1/2
- ISSN
- 0004-637X
- eISSN
- 1538-4357
- Publisher
- Institute of Physics (IOP)
- Language
- English
- Date published
- 07/2014
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199717802771
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