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arXiv · 2607.17271

Ongoing Morphological Transformation from Elliptical to Spiral Galaxies Induced by Gas Accretion from Neighboring Galaxies

Gene Yun·Sang Hyeok Im·Ho Seong Hwang·Changbom Park·Hyeonguk Bahk
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Abstract

We present results from spectroscopic observations of three interacting galaxy systems, each associated with a primary galaxy - VCC 1748, SDSS J1106, and 2MASX J0834 - which have been proposed as potential examples of reverse morphological transformation from elliptical to spiral types driven by external gas accretion. Using Gemini/GMOS longslit spectroscopy, we obtain spectra along longslits connecting the regions of interest between the two galaxies in each pair. We model the spatially binned spectra with the Penalized Pixel-Fitting (pPXF) method to derive velocity fields and radial profiles of gas-phase metallicity, stellar metallicity, and stellar population age. Among the three systems, only the VCC 1748 system provides spectra with sufficiently high signal-to-noise ratios (S/N) to reveal coherent velocity and metallicity structures extending between the companion spiral galaxy and its elliptical target. The velocity profile along the gas-bridge of the system is smooth and continuous from the companion spiral arm to the target galaxy, and the elliptical target, VCC 1748, exhibits younger stellar populations and a high star formation rate (SFR) in its newly formed disk regions compared to its central parts. These findings indicate in-situ star formation at the newly-formed spiral arm of the elliptical target, consistent with ongoing gas inflow from the spiral companion into the elliptical target. Altogether, the results capture an intermediate stage of morphological evolution in which an originally quiescent elliptical galaxy begins to assemble a rotationally supported disk through interaction-driven gas accretion.

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Gene Yun, Sang Hyeok Im, Ho Seong Hwang, Changbom Park, Hyeonguk Bahk. 2026-07-19. Ongoing Morphological Transformation from Elliptical to Spiral Galaxies Induced by Gas Accretion from Neighboring Galaxies. https://arxiv.org/abs/2607.17271

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