Tripling the Census of Dwarf AGN Candidates Using DESI Early Data

Journal Article · Tue Mar 11 00:00:00 EDT 2025 · The Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/adb1dd· OSTI ID:2530487

Pucha, Ragadeepika; Juneau, S.; Dey, Arjun; Siudek, M.; Mezcua, M.; Moustakas, J.; BenZvi, S.; Hainline, K.; Hviding, R.; Mao, Yao-Yuan; Alexander, D. M.; Alfarsy, R.; Circosta, C.; Guo, Wei-Jian; Manwadkar, V.; Martini, P.; Weaver, B. A.; Aguilar, J.; Ahlen, S.; Bianchi, D. ; Brooks, D.; Canning, R.; Claybaugh, T.; Dawson, K.; de la Macorra, A.; Dey, Biprateep; Doel, P.; Font-Ribera, A.; Forero-Romero, J. E.; Gaztañaga, E.; Gontcho A Gontcho, S.; Gutierrez, G.; Honscheid, K.; Kehoe, R.; Koposov, S. E.; Lambert, A.; Landriau, M.; Le Guillou, L.; Meisner, A.; Miquel, R.; Prada, F.; Rossi, G.; Sanchez, E.; Schlegel, D.; Schubnell, M.; Seo, H.; Sprayberry, D.; Tarlé, G.; Zou, H.

Using early data from the Dark Energy Spectroscopic Instrument (DESI) survey, we search for active galactic nuclei (AGN) signatures in 410,757 line-emitting galaxies. By employing the BPT emission-line ratio diagnostic diagram, we identify AGNs in 75,928/296,261 (≈25.6%) high-mass ($$\mathrm{log}({M}_{\star }/{M}_{\odot })\,\gt$$ 9.5) and 2444/114,496 (≈2.1%) dwarf ($$\mathrm{log}({M}_{\star }/{M}_{\odot })\,\leqslant$$ 9.5) galaxies. Of these AGN candidates, 4181 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 AGNs and doubles the number of intermediate-mass black hole (M_BH ≤ 10⁶M_⊙) candidates, spanning a broad discovery space in stellar mass (7 $$\lt \mathrm{log}({M}_{\star }/{M}_{\odot })\,\lt$$ 12) and redshift (0.001 < 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 M_BH–M⋆ scaling relation down to $${\rm{log}}({M}_{\star }/{M}_{\odot })\,\approx$$ 8.5 and $$\mathrm{log}({M}_{\mathrm{BH}}/{M}_{\odot })\,\approx$$ 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.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Univ. of Utah, Salt Lake City, UT (United States)
• Sponsoring Organization: U.S. National Science Foundation (NSF), Division of Astronomical Sciences; USDOE; USDOE Office of Science (SC), High Energy Physics (HEP)
• Contributing Organization: DESI Collaboration
• Grant/Contract Number: 89243024CSC000002; AC02-05CH11231; SC0009959
• OSTI ID: 2530487
• Alternate ID(s): OSTI ID: 2575480; OSTI ID: 3009753; OSTI ID: 2553045
• Report Number(s): FERMILAB-PUB--25-0198-PPD
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 1 Vol. 982; ISSN 0004-637X; ISSN 1538-4357
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AGN host galaxies
dwarf galaxies
intermediate-mass black holes