Near-infrared Variability Detected in the Young Star-Forming Dwarf Galaxy SBS 0335-052E
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2023
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| author | Hatano, Shun Kokubo, Mitsuru Ouchi, Masami Nakajima, Kimihiko Kawaguchi, Toshihiro Kikuta, Satoshi Tominaga, Nozomu Xu, Yi Watanabe, Kuria Harikane, Yuichi Isobe, Yuki Matsumoto, Akinori Nishigaki, Moka Ono, Yoshiaki Onodera, Masato Sugahara, Yuma Umeda, Hiroya Zhang, Yechi Chiba, Ryotaro Moriya, Takashi J. |
| author_facet | Hatano, Shun Kokubo, Mitsuru Ouchi, Masami Nakajima, Kimihiko Kawaguchi, Toshihiro Kikuta, Satoshi Tominaga, Nozomu Xu, Yi Watanabe, Kuria Harikane, Yuichi Isobe, Yuki Matsumoto, Akinori Nishigaki, Moka Ono, Yoshiaki Onodera, Masato Sugahara, Yuma Umeda, Hiroya Zhang, Yechi Chiba, Ryotaro Moriya, Takashi J. |
| contents | SBS~0335-052E is a young star-forming dwarf galaxy with a total stellar mass of $M_{*} \lesssim 10^{8}~M_{\odot}$ and an extremely low metallicity ($Z \sim 1/40~Z_{\odot}$), which has long been considered to be devoid of an active galactic nucleus (AGN). Here we report the detection of temporal flux variability of SBS~0335-052E in near-infrared (NIR) 3-4\ ${\rm μ}$m bands on timescales of several years, showing dimming and brightening of up to 50\% over 14~years, based on archival data from the Wide-field Infrared Survey Explorer. Our spectral energy distribution (SED) fitting of archival ultraviolet (UV)-NIR photometry, including AGN SED models, indicates that the variable NIR emission arises from an edge-on AGN dust torus. The UV-optical emission from the accretion disk is obscured and does not reach us, leading to the dominance of the host galaxy's young stellar population in the UV-optical wavelengths. This analysis favors the presence of a Compton-thick, heavily obscured AGN in SBS~0335-052E, consistent with its observed X-ray weakness. From the SED fitting, we estimate an AGN bolometric luminosity of $L_{\rm bol} = 1.2\times10^{43}\ {\rm erg\ s^{-1}}$, which implies a black hole mass of $M_{\rm BH} \simeq 10^{5}\ M_\odot$ if the AGN is accreting at the Eddington limit. If confirmed, SBS~0335-052E would be the least massive galaxy known to host an AGN, likely harboring an intermediate-mass black hole. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2304_03726 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Near-infrared Variability Detected in the Young Star-Forming Dwarf Galaxy SBS 0335-052E Hatano, Shun Kokubo, Mitsuru Ouchi, Masami Nakajima, Kimihiko Kawaguchi, Toshihiro Kikuta, Satoshi Tominaga, Nozomu Xu, Yi Watanabe, Kuria Harikane, Yuichi Isobe, Yuki Matsumoto, Akinori Nishigaki, Moka Ono, Yoshiaki Onodera, Masato Sugahara, Yuma Umeda, Hiroya Zhang, Yechi Chiba, Ryotaro Moriya, Takashi J. Astrophysics of Galaxies SBS~0335-052E is a young star-forming dwarf galaxy with a total stellar mass of $M_{*} \lesssim 10^{8}~M_{\odot}$ and an extremely low metallicity ($Z \sim 1/40~Z_{\odot}$), which has long been considered to be devoid of an active galactic nucleus (AGN). Here we report the detection of temporal flux variability of SBS~0335-052E in near-infrared (NIR) 3-4\ ${\rm μ}$m bands on timescales of several years, showing dimming and brightening of up to 50\% over 14~years, based on archival data from the Wide-field Infrared Survey Explorer. Our spectral energy distribution (SED) fitting of archival ultraviolet (UV)-NIR photometry, including AGN SED models, indicates that the variable NIR emission arises from an edge-on AGN dust torus. The UV-optical emission from the accretion disk is obscured and does not reach us, leading to the dominance of the host galaxy's young stellar population in the UV-optical wavelengths. This analysis favors the presence of a Compton-thick, heavily obscured AGN in SBS~0335-052E, consistent with its observed X-ray weakness. From the SED fitting, we estimate an AGN bolometric luminosity of $L_{\rm bol} = 1.2\times10^{43}\ {\rm erg\ s^{-1}}$, which implies a black hole mass of $M_{\rm BH} \simeq 10^{5}\ M_\odot$ if the AGN is accreting at the Eddington limit. If confirmed, SBS~0335-052E would be the least massive galaxy known to host an AGN, likely harboring an intermediate-mass black hole. |
| title | Near-infrared Variability Detected in the Young Star-Forming Dwarf Galaxy SBS 0335-052E |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2304.03726 |