DIISC-VII: Linking Radial Gas Motions to Anomalously Low Metallicity Star-forming Regions in the XUV Disk of NGC 3344
Abstract
We present evidence connecting anomalously low-metallicity regions to radial gas inflows in the extended ultraviolet (XUV) disk of the galaxy NGC 3344. Anomalously low-metallicity H II regions are hypothesized to result from the accretion of metal-poor gas, but a direct link between gas flows and low metallicity gas has not been previously established. We use high-resolution H I-21cm imaging from the Very Large Array to trace neutral gas kinematics and multi-slit optical spectroscopy from the MMT to trace the gas-phase metallicity of 76 H II regions in NGC 3344. The galaxy exhibits a negative radial metallicity gradient of −0.378 dex R25−1, with H II regions in the XUV disk showing nearly twice the metallicity scatter of those in the inner disk and several showing an anomalously low metallicity. Modeling the H I disk as tilted rings with 3DBarolo, we find gas moving radially inwards within the XUV disk at an average radial velocity of 6 km s−1, likely fueling star formation and diluting the metallicity, thereby producing anomalously low metallicity regions. Chemical evolution models indicate that the gas fraction, effective yield, and mass-loading factor profiles are disrupted at the onset of the XUV disk, as expected from recent gas flows. This example is the first direct detection of how radial gas flows can support stellar disk expansion and cause inside-out galaxy growth.
Versions
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BibTeX
@misc{olvera2026diiscvii,
title = {{DIISC-VII: Linking Radial Gas Motions to Anomalously Low Metallicity Star-forming Regions in the XUV Disk of NGC 3344}},
author = {Alejandro J. Olvera and Sanchayeeta Borthakur and Enrico M. Di Teodoro and Kanak Saha and Mansi Padave and Hansung B. Gim and Emmanuel Momjian},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.26884},
eprint = {2609.26884},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.26884},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - DIISC-VII: Linking Radial Gas Motions to Anomalously Low Metallicity Star-forming Regions in the XUV Disk of NGC 3344
AU - Alejandro J. Olvera
AU - Sanchayeeta Borthakur
AU - Enrico M. Di Teodoro
AU - Kanak Saha
AU - Mansi Padave
AU - Hansung B. Gim
AU - Emmanuel Momjian
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.26884
UR - https://arxiv.org/abs/2609.26884
AB - We present evidence connecting anomalously low-metallicity regions to radial gas inflows in the extended ultraviolet (XUV) disk of the galaxy NGC 3344. Anomalously low-metallicity H II regions are hypothesized to result from the accretion of metal-poor gas, but a direct link between gas flows and low metallicity gas has not been previously established. We use high-resolution H I-21cm imaging from the Very Large Array to trace neutral gas kinematics and multi-slit optical spectroscopy from the MMT to trace the gas-phase metallicity of 76 H II regions in NGC 3344. The galaxy exhibits a negative radial metallicity gradient of −0.378 dex R_25^−1, with H II regions in the XUV disk showing nearly twice the metallicity scatter of those in the inner disk and several showing an anomalously low metallicity. Modeling the H I disk as tilted rings with 3DBarolo, we find gas moving radially inwards within the XUV disk at an average radial velocity of 6 km s^−1, likely fueling star formation and diluting the metallicity, thereby producing anomalously low metallicity regions. Chemical evolution models indicate that the gas fraction, effective yield, and mass-loading factor profiles are disrupted at the onset of the XUV disk, as expected from recent gas flows. This example is the first direct detection of how radial gas flows can support stellar disk expansion and cause inside-out galaxy growth.
ER -