Nuclear Activity in the Low-metallicity Dwarf Galaxy SDSS J0944-0038 : A Glimpse into the Primordial Universe

Reefe, Michael and Satyapal, Shobita and Sexton, Remington O. and Secrest, Nathan J. and Matzko, William and Schwartzman, Emma and Nyland, Kristina and Canalizo, Gabriela and Rothberg, Barry and Pfeifle, Ryan W. and Cann, Jenna M. and Aravindan, Archana and Vazquez, Camilo and Clarke, Tracy (2023) Nuclear Activity in the Low-metallicity Dwarf Galaxy SDSS J0944-0038 : A Glimpse into the Primordial Universe. The Astrophysical Journal Letters, 946 (2). L38. ISSN 2041-8205

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Local low-metallicity dwarf galaxies are relics of the early universe and are thought to hold clues into the origins of supermassive black holes. While recent studies are uncovering a growing population of active galactic nuclei (AGNs) in dwarf galaxies, the vast majority reside in galaxies with solar or supersolar metallicities and stellar masses comparable to that of the LMC. Using Multi-Unit Spectroscopic Explorer (MUSE) and Very Large Telescope observations, we report the detection of [Fe x] λ6374 coronal line emission and a broad Hα line in the nucleus of SDSS J094401.87−003832.1, a nearby (z = 0.0049) metal-poor dwarf galaxy almost 500 times less massive than the LMC. Unlike the emission from the lower-ionization nebular lines, the [Fe x] λ6374 emission is compact and centered on the brightest nuclear source, with a spatial extent of ≈100 pc, similar to that seen in well-known AGNs. The [Fe x] luminosity is ≈1037 erg s−1, within the range seen in previously identified AGNs in the dwarf-galaxy population. The [Fe x] emission has persisted over the roughly 19 yr time period between the SDSS and MUSE observations, ruling out supernovae as the origin for the emission. The FWHM of the broad component of the Hα line is 446 ± 17 km s−1 and its luminosity is ≈1.5 × 1038 erg s−1, corresponding to a black hole mass of ≈ 3150 M⊙, in line with its stellar mass if virial mass relations and black hole–galaxy scaling relations apply in this mass regime. These observations, together with previously reported multiwavelength observations, can most plausibly be explained by the presence of an accreting intermediate-mass black hole in a primordial galaxy analog.

Item Type: Article
Subjects: Eprints STM archive > Physics and Astronomy
Depositing User: Unnamed user with email admin@eprints.stmarchive
Date Deposited: 03 May 2023 08:00
Last Modified: 03 Jan 2024 06:51

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