Exploring New Redshift Indicators for Radio-Powerful AGN

Galaxies

Rodrigo Carvajal¹  José Afonso¹  Davi Barbosa¹  Israel Matute¹  Stergios Amarantidis¹  Andrew Humphrey²  Pedro Cunha² 

[1] Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa, OAL, Tapada da Ajuda, PT1349-018 Lisbon, Portugal;Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal;

关键词: Active Galactic Nuclei;    radio galaxies;    redshift determination;    multiwavelength catalogues;    Machine Learning;   

DOI  :  10.3390/galaxies9040086

来源: DOAJ

【 摘 要 】

Active Galactic Nuclei (AGN) are relevant sources of radiation that might have helped reionising the Universe during its early epochs. The super-massive black holes (SMBHs) they host helped accreting material and emitting large amounts of energy into the medium. Recent studies have shown that, for epochs earlier than $z\sim 5$, the number density of SMBHs is on the order of few hundreds per square degree. Latest observations place this value below 300 SMBHs at $z\gtrsim 6$ for the full sky. To overcome this gap, it is necessary to detect large numbers of sources at the earliest epochs. Given the large areas needed to detect such quantities, using traditional redshift determination techniques—spectroscopic and photometric redshift—is no longer an efficient task. Machine Learning (ML) might help obtaining precise redshift for large samples in a fraction of the time used by other methods. We have developed and implemented an ML model which can predict redshift values for WISE-detected AGN in the HETDEX Spring Field. We obtained a median prediction error of ${\sigma }_z^N=1.48\times (z_{\mathrm{Predicted}}-z_{\mathrm{True}})/(1+z_{\mathrm{True}})=0.1162$ and an outlier fraction of $\eta =11.58\%$ at $(z_{\mathrm{Predicted}}-z_{\mathrm{True}})/(1+z_{\mathrm{True}})>0.15$, in line with previous applications of ML to AGN. We also applied the model to data from the Stripe 82 area obtaining a prediction error of ${\sigma }_z^N=0.2501$.

【 授权许可】

Unknown