Declining metallicity and extended HeII in the outflow of an epoch of reionization analogue galaxy
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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866908762118291456 |
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| author | Hamel-Bravo, M. J. Fisher, D. B. Berg, D. A. Cameron, A. J. Chisholm, J. Kacprzak, G. G. Ciraulo, B. Mazzilli Katz, H. |
| author_facet | Hamel-Bravo, M. J. Fisher, D. B. Berg, D. A. Cameron, A. J. Chisholm, J. Kacprzak, G. G. Ciraulo, B. Mazzilli Katz, H. |
| contents | We present VLT/X-shooter spectroscopy of the extremely metal-poor starburst galaxy SBS 0335-052E, a nearby (D $\sim$54 Mpc) analog of high-redshift systems, probing its outflow up to a distance of $\sim$2.6 kpc. Using direct-method oxygen abundances, we find a complex metallicity profile that generally declines with distance, decreasing by 0.37 dex from the galaxy center out to 2.4 kpc into the outflow. This implies a metal-loading factor roughly an order of magnitude lower than predictions based on the mass-metallicity relation for low-mass galaxies. We also detect extended HeII emission, including a broad, redshifted component beyond 2 kpc, distinct from narrow emission associated with star clusters. No H$β$ emission is detected associated with the broad redshifted component, implying extremely high HeII/H$β$ ratios (0.7--4.8). Such extreme values, combined with the decreasing metallicity, challenge current models for stellar feedback. The contribution of an intermediate-mass black hole could simultaneously account for the declining metallicity and the unusually extended HeII emission. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_05332 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Declining metallicity and extended HeII in the outflow of an epoch of reionization analogue galaxy Hamel-Bravo, M. J. Fisher, D. B. Berg, D. A. Cameron, A. J. Chisholm, J. Kacprzak, G. G. Ciraulo, B. Mazzilli Katz, H. Astrophysics of Galaxies We present VLT/X-shooter spectroscopy of the extremely metal-poor starburst galaxy SBS 0335-052E, a nearby (D $\sim$54 Mpc) analog of high-redshift systems, probing its outflow up to a distance of $\sim$2.6 kpc. Using direct-method oxygen abundances, we find a complex metallicity profile that generally declines with distance, decreasing by 0.37 dex from the galaxy center out to 2.4 kpc into the outflow. This implies a metal-loading factor roughly an order of magnitude lower than predictions based on the mass-metallicity relation for low-mass galaxies. We also detect extended HeII emission, including a broad, redshifted component beyond 2 kpc, distinct from narrow emission associated with star clusters. No H$β$ emission is detected associated with the broad redshifted component, implying extremely high HeII/H$β$ ratios (0.7--4.8). Such extreme values, combined with the decreasing metallicity, challenge current models for stellar feedback. The contribution of an intermediate-mass black hole could simultaneously account for the declining metallicity and the unusually extended HeII emission. |
| title | Declining metallicity and extended HeII in the outflow of an epoch of reionization analogue galaxy |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2510.05332 |