The role of the synchrotron component in the mid-infrared spectrum of M 87

We study in detail the mid-infrared (MIR) Spitzer-IRS spectrum of M 87 in the range 5–20 μm. Thanks to the high sensitivity of our Spitzer-IRS spectra we can disentangle the stellar and nuclear components of this active galaxy. To this end, we have properly subtracted from the M 87 spectrum the cont...

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Bibliographic Details
Main Authors: JOSE RAMON VALDES PARRA, MIGUEL Y ROSA MARIA CHAVEZ DAGOSTINO
Format: info:eu-repo/semantics/article
Language:eng
Published: The Astrophysical Journal 2009
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Online Access:http://inaoe.repositorioinstitucional.mx/jspui/handle/1009/1283
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Summary:We study in detail the mid-infrared (MIR) Spitzer-IRS spectrum of M 87 in the range 5–20 μm. Thanks to the high sensitivity of our Spitzer-IRS spectra we can disentangle the stellar and nuclear components of this active galaxy. To this end, we have properly subtracted from the M 87 spectrum the contribution of the underlying stellar continuum derived from passive Virgo galaxies in our sample. The residual is a clear power law, without any additional termal component, with a zero-point consistent with that obtained by high spatial resolution, ground-based observations. The residual is independent of the adopted passive template. This indicates that the 10 μm silicate emission shown in the spectra of M 87 can be entirely accounted for by the underlying old stellar population, leaving little room for a possible torus contribution. The MIR power law has a slope α ∼0.77–0.82 (Sᵥ ∝ ν exp−α), consistent with optically thin synchrotron emission.

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