2024/10/31 by Pucha, Ragadeepika, Juneau, S., Dey, Arjun +46 · 10 citations
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2411.00091
Using early data from the Dark Energy Spectroscopic Instrument (DESI) survey, we search for AGN signatures in 410,757 line-emitting galaxies. By employing the BPT emission-line ratio diagnostic diagram, we identify AGN in 75,928/296,261 (≈25.6%) high-mass (log (M⋆/\rm M\odot) > 9.5) and 2,444/114,496 (≈2.1%) dwarf (log (M⋆/\rm M\odot) ≤ 9.5) galaxies. Of these AGN candidates, 4,181 sources exhibit a broad Hα component, allowing us to estimate their BH masses via virial techniques. This study more than triples the census of dwarf AGN and doubles the number of intermediate-mass black hole (IMBH; MBH ≤ 106~\rm M\odot) candidates, spanning a broad discovery space in stellar mass (7 < log (M⋆/M\odot) < 12) and redshift (0.001 < \rm z < 0.45). The observed AGN fraction in dwarf galaxies (≈2.1%) is nearly four times higher than prior estimates, primarily due to DESI's smaller fiber size, which enables the detection of lower luminosity dwarf AGN candidates. We also extend the MBH - M⋆ scaling relation down to log (M⋆/M\odot) ≈ 8.5 and log (MBH/\rm M\odot) ≈ 4.4, with our results aligning well with previous low-redshift studies. The large statistical sample of dwarf AGN candidates from current and future DESI releases will be invaluable for enhancing our understanding of galaxy evolution at the low-mass end of the galaxy mass function.