The massive black hole (BH) population in dwarf galaxies (MBH ≲ 105M⊙) can provide strong constraints on the origin of BH seeds. However, traditional optical searches for active galactic nuclei (AGNs) only reliably detect high-accretion, relatively high-mass BHs in dwarf galaxies with low amounts of star formation, leaving a large portion of the overall BH population in dwarf galaxies relatively unexplored. Here, we present a sample of 81 dwarf galaxies (M$$\star$$ ≤ 3 × 109M⊙) with detectable [Fe x]λ6374 coronal line emission indicative of accretion onto massive BHs, only two of which were previously identified as optical AGNs. Here, we analyze optical spectroscopy from the Sloan Digital Sky Survey and find [Fe x]λ6374 luminosities in the range L[Fe x] ≈ 1036–1039 erg s–1, with a median value of 1.6 × 1038 erg s–1. The [Fe x]λ6374 luminosities are generally much too high to be produced by stellar sources, including luminous Type IIn supernovae (SNe). Moreover, based on known SNe rates, we expect at most eight Type IIn SNe in our sample. That said, the [Fe x]λ6374 luminosities are consistent with accretion onto massive BHs from AGNs or tidal disruption events (TDEs). We find additional indicators of BH accretion in some cases using other emission line diagnostics, optical variability, and X-ray and radio emission (or some combination of these). However, many of the galaxies in our sample only have evidence for a massive BH based on their [Fe x]λ6374 luminosities. This work highlights the power of coronal line emission to find BHs in dwarf galaxies missed by other selection techniques and to probe the BH population in bluer, lower-mass dwarf galaxies.
Molina, Mallory, et al. "A Sample of Massive Black Holes in Dwarf Galaxies Detected via [Fe x] Coronal Line Emission: Active Galactic Nuclei and/or Tidal Disruption Events." The Astrophysical Journal, vol. 922, no. 2, Nov. 2021. https://doi.org/10.3847/1538-4357/ac1ffa
Molina, Mallory, Reines, Amy E., Latimer, Lilikoi, Baldassare, Vivienne, & Salehirad, Sheyda (2021). A Sample of Massive Black Holes in Dwarf Galaxies Detected via [Fe x] Coronal Line Emission: Active Galactic Nuclei and/or Tidal Disruption Events. The Astrophysical Journal, 922(2). https://doi.org/10.3847/1538-4357/ac1ffa
Molina, Mallory, Reines, Amy E., Latimer, Lilikoi, et al., "A Sample of Massive Black Holes in Dwarf Galaxies Detected via [Fe x] Coronal Line Emission: Active Galactic Nuclei and/or Tidal Disruption Events," The Astrophysical Journal 922, no. 2 (2021), https://doi.org/10.3847/1538-4357/ac1ffa
@article{osti_1983185,
author = {Molina, Mallory and Reines, Amy E. and Latimer, Lilikoi and Baldassare, Vivienne and Salehirad, Sheyda},
title = {A Sample of Massive Black Holes in Dwarf Galaxies Detected via [Fe x] Coronal Line Emission: Active Galactic Nuclei and/or Tidal Disruption Events},
annote = {The massive black hole (BH) population in dwarf galaxies (MBH ≲ 105 M⊙) can provide strong constraints on the origin of BH seeds. However, traditional optical searches for active galactic nuclei (AGNs) only reliably detect high-accretion, relatively high-mass BHs in dwarf galaxies with low amounts of star formation, leaving a large portion of the overall BH population in dwarf galaxies relatively unexplored. Here, we present a sample of 81 dwarf galaxies (M$\star$ ≤ 3 × 109 M⊙) with detectable [Fe x]λ6374 coronal line emission indicative of accretion onto massive BHs, only two of which were previously identified as optical AGNs. Here, we analyze optical spectroscopy from the Sloan Digital Sky Survey and find [Fe x]λ6374 luminosities in the range L[Fe x] ≈ 1036–1039 erg s–1, with a median value of 1.6 × 1038 erg s–1. The [Fe x]λ6374 luminosities are generally much too high to be produced by stellar sources, including luminous Type IIn supernovae (SNe). Moreover, based on known SNe rates, we expect at most eight Type IIn SNe in our sample. That said, the [Fe x]λ6374 luminosities are consistent with accretion onto massive BHs from AGNs or tidal disruption events (TDEs). We find additional indicators of BH accretion in some cases using other emission line diagnostics, optical variability, and X-ray and radio emission (or some combination of these). However, many of the galaxies in our sample only have evidence for a massive BH based on their [Fe x]λ6374 luminosities. This work highlights the power of coronal line emission to find BHs in dwarf galaxies missed by other selection techniques and to probe the BH population in bluer, lower-mass dwarf galaxies.},
doi = {10.3847/1538-4357/ac1ffa},
url = {https://www.osti.gov/biblio/1983185},
journal = {The Astrophysical Journal},
issn = {ISSN 0004-637X},
number = {2},
volume = {922},
place = {United States},
publisher = {IOP Publishing},
year = {2021},
month = {11}}
Argonne National Laboratory (ANL), Argonne, IL (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing
Center (NERSC); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Organization:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Office of Science (SC), High Energy Physics (HEP)
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1983185
Journal Information:
The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 2 Vol. 922; ISSN 0004-637X