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arXiv · 2303.18245

AGN in the CALIFA survey: X-ray detection of nuclear sources

Natalia Osorio-Clavijo·Omaira González-Martín·Sebastián F. Sánchez-Sánchez·Matteo Guainazzi·Irene Cruz-González
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Abstract

A complete demographic of active galactic nuclei (AGN) is essential to understand the evolution of the Universe. Optical surveys estimate the population of AGN in the local Universe to be of $\sim$ 4%. However, these results could be biased towards bright sources, not affected by the host galaxy attenuation. An alternative method for detecting these objects is through the X-ray emission. In this work, we aim to complement the AGN population of the optical CALIFA survey (941 sources), by using X-ray data from Chandra, which provides the best spatial resolution to date, essential to isolate the nuclear emission from the host galaxy. We study a total of 138 sources with available data. We find 34 new bonafide AGN and 23 AGN candidates, which could increase the AGN population to 7-10\% among the CALIFA survey. X-rays are particularly useful for low-luminosity AGN since they are excluded by the criterion of large equivalent width of the $H\alpha$ emission line when applied to optical selections. Indeed, placing such a restrictive criteria might cause a loss of up to 70% of AGN sources. X-ray detected sources are preferentially located in the right side of the [$OIII$]/$H\beta$ versus [$NII$]/$H\alpha$ diagram, suggesting that this diagram might be the most reliable at classifying AGN sources. Our results support the idea that multi-wavelength studies are the best way to obtain a complete AGN population.

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Natalia Osorio-Clavijo, Omaira González-Martín, Sebastián F. Sánchez-Sánchez, Matteo Guainazzi, Irene Cruz-González. 2023-03-31. AGN in the CALIFA survey: X-ray detection of nuclear sources. https://doi.org/10.1093/mnras/stad1262

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