Direct Evidence from Spitzer for a low-luminosity AGN at the center of the Elliptical Galaxy NGC 315

TL;DR

This study uses Spitzer infrared observations to identify and characterize a low-luminosity active galactic nucleus in NGC 315, revealing its spectral energy distribution and confirming its AGN nature.

Contribution

First infrared detection of the nucleus in NGC 315, providing detailed spectral energy distribution and bolometric luminosity measurement for a low-luminosity AGN.

Findings

Detected infrared nucleus after stellar emission removal

Measured bolometric luminosity of approximately 1.9 x 10^43 ergs/s

Confirmed the nucleus as a low-luminosity AGN

Abstract

We present the {\it Spitzer} Space Telescope InfraRed Array Camera (IRAC) and Multiband Imaging Photometer (MIPS) observations of the elliptical galaxy NGC 315. After removal of the host galaxy's stellar emission, we detected for the first time an infrared-red nucleus in NGC 315. We measured the spectral energy distribution (SED) for this active nucleus with wavelength range covering from radio to X-ray, and obtained the bolometric luminosity of $\rm L_{bol} \approx 1.9 \times 10^{43} ergs s^{-1}$, corresponding to an extremely low Eddington ratio (L/L$_{\rm Edd}$) of 4.97 $\times$ 10$^{-4}$. Our results confirm that the physical nature of the nucleus of NGC 315 is a low-luminosity AGN, consistent with the recent optical and {\it Chandra} X-ray observations.