arXiv subjects

Gene Yun

Publications and source records attributed to Gene Yun.

2 recordsLinked to original sources

arXiv2026

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

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.

astro-ph.GA↗

arXiv2025

Twin peaks: SN 2021uvy and SN 2022hgk in the landscape of double-peaked stripped envelope supernovae

In recent years, a class of stripped-envelope supernovae (SESNe) showing two distinct light-curve peaks has emerged, where the first peak cannot be attributed to shock cooling emission. Such peculiar SNe are often studied individually, explained by a combination of powering mechanisms, but are rarely discussed broadly as a group. In this paper, we attempt to form a picture of the landscape of double-peaked SESNe and their powering mechanisms by adding two more objects -- SN 2021uvy and SN 2022hgk. SN 2021uvy is a broad, luminous SN Ib with an unusually long first peak rise and constant color evolution with rising photospheric temperature during the second peak. Though its first peak resembles SN 2019stc, their second peaks differ, making SN 2021uvy unique. SN 2022hgk shows photometric similarity to SN 2019cad and spectroscopic similarity to SN 2005bf, both proposed to be powered by a double-nickel distribution in their ejecta. We analyze their light curves and colors, compare them with a sample of double-peaked SESNe from the ZTF archive, and analyze the light curve parameters of the sample. We observe a correlation (p-value~0.025) between the peak absolute magnitudes of the first and second peaks. No single definitive powering mechanism applies to the whole sample, as it shows variety in the photometric and spectroscopic properties. However, sub-groups of similarity exist that can be explained by mechanisms like the double-nickel distribution, magnetar central engine, interaction, and fallback accretion. We also map out the duration between the peaks ($\Delta t^{21}$) vs the difference between peak absolute magnitudes ($\Delta M^{21}$) as a phase-space that could potentially delineate the most promising powering mechanisms for the double-peaked SESNe.

astro-ph.HE↗