arXiv subjects

Mira Seo

Publications and source records attributed to Mira Seo.

5 recordsLinked to original sources

arXiv2025

Star Formation Histories of Early-type Dwarfs in Group Environment

We investigate the star formation histories (SFHs) of 983 early-type dwarf galaxies classified into five morphological subtypes, dS0, dE, dEbc, dSph, and dEbl,across six environments ranging from the field to rich clusters such as Ursa Major and Virgo. Using full spectral fitting of SDSS spectra with the starlight code, we derive detailed SFHs and chemical enrichment patterns. We find that SFHs are primarily shaped by morphology, with environment playing a secondary but non-negligible role. Red early-type dwarfs (dS0, dE, dSph) typically formed most of their stars early and quenched rapidly, whereas blue early-type dwarfs (dEbc, dEbl) exhibit extended or ongoing star formation and host extremely metal-poor stars, suggesting continued pristine gas accretion. Environmental dependence is clearest in low-mass systems: field galaxies often show prolonged SFHs and delayed enrichment, while Virgo Cluster galaxies tend to quench earlier and enrich more rapidly. Cumulative SFHs reinforce these trends, with dSph galaxies showing the earliest quenching and least environmental dependence, indicating a likely primordial origin. Metallicity evolution also varies with mass and environment, progressing most slowly in low-mass field galaxies and most rapidly in high-mass cluster galaxies. Our results highlight the combined influence of morphology, stellar mass, and environment on the evolutionary diversity of early-type dwarfs, and suggest that both internal processes (nature) and external conditions (nurture) are intricately linked in shaping their star formation and chemical enrichment histories.

astro-ph.GA↗

arXiv2024

Star Formation Histories of Dwarf Lenticular Galaxies

Star formation histories (SFHs) are essential for understanding galaxy formation and evolution. We present the mean SFHs of 148 dwarf lenticular galaxies (dS0s) derived from the Sloan Digital Sky Survey (SDSS) spectra. These SFHs reveal two distinct periods of active star formation. The first period, concluding approximately 6 Gyr ago, witnessed the formation of predominantly old, metal-poor (Z=0.0004) stars, accounting for approximately 60\% of the stellar mass and 30\% of the luminosity. The scarcity of extremely metal-poor (Z=0.0001) stars suggests pre-enrichment during the re-ionization era. Star formation gradually waned during this initial phase. In contrast, the second period, ending around 1 Gyr ago, exhibited a peak in the middle of the period, contributing to the formation of moderately old stellar populations with intermediate metallicity. The SFHs of dS0 galaxies show a clear dependence on stellar mass, with more massive dS0s forming stars earlier. But, we find no significant correlation with morphological properties such as outer spiral arms and nucleation. The SFHs of dS0 galaxies share many similarities with those of dE galaxies, suggesting a common origin, mostly not primordial.

astro-ph.GA↗

arXiv2023

Star Formation Histories of Dwarf Spheroidal and Dwarf Elliptical Galaxies in the Local Universe

We present the star formation histories (SFHs) of early-type dwarf galaxies, dSphs and dEs, in the local universe within z=0.01. The SFHs of early-type dwarf galaxies are characterized by pre-enriched, metal-poor old stellar populations, absence of moderately old stars that have ages of a few Gyr. There are some differences in the SFHs of dSphs and dEs. In particular, dSphs formed old ($\gtrsim10$ Gyr old) metal-poor stars $\sim2$ times more than dEs. The effects of reionization and feedback from supernova explosions are thought to be strong enough to remove the gas left, which prevent moderately old stellar populations in dSphs. In contrast, the ejected gas are not completely removed from dEs and fall back to ignite burst of star formation at a few Gyr after the first period of violent bursts of star formation, showing a suppression of star formation at lookback time $\approx 9.6$ Gyr. The second peak of star formation at lookback time $\approx 4.5$ Gyr in dEs produce moderately old stellar populations. Distinction between dSphs and dEs is useful to examine the SFHS of the early-type dwarfs since the cumulative SFHs are most closely related to their morphology. The stellar mass plays an important role in the SFHs of the early-type dwarfs as a driver of star formation, especially in galaxies with primordial origin.

astro-ph.GA↗

arXiv2022

Luminosity Distribution of Dwarf Elliptical-like Galaxies

We present the structural parameters of $\sim910$ dwarf elliptical-like galaxies in the local universe ($z\lesssim0.01$) derived from the $r-$band images of the Sloan Digital Sky Survey (SDSS). We examine the dependence of structural parameters on the morphological types (dS0, dE,dE$_{bc}$, dSph, and dE$_{blue}$). There is a significant difference in the structural parameters among the five sub-types if we properly treat the light excess due to nucleation in dSph and dE galaxies. The mean surface brightness within the effective radius ($<μ_{e}>$) of dSph galaxies is also clearly different from that of other sub-types. The frequency of disk features such as spiral arms depends on the morphology of dwarf galaxies. The most pronounced difference between dSph galaxies and other sub-types of early-type dwarf galaxies is the absence of disk feature which is thought to be closely related to their origin.

astro-ph.GA↗

arXiv2015

Catalog of Visually Classified Galaxies in the Local ($z\sim0.01$) Universe

The morphological types of 5840 galaxies were classified by a visual inspection of color images using the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) to produce a morphology catalog of a representative sample of local galaxies with $z<0.01$. The sample galaxies are almost complete for galaxies brighter than $r_{pet}=17.77$. Our classification system is basically the same as that of the Third Reference Catalog of Bright Galaxies with some simplification for giant galaxies. On the other hand, we distinguish fine features of dwarf elliptical-like galaxies to classify 5 subtypes: dwarf ellipticals (dE), blue-cored dwarf ellipticals (dE$_{bc}$), dwarf spheroidals (dSph), blue dwarf ellipticals (dE$_{blue}$), and dwarf lenticulars (dS0). In addition, we denote the presence of nucleation in dE, dSph, and dS0. Elliptical galaxies and lenticular galaxies contribute only $\sim1.5\%$ and $\sim4.9\%$ of the local galaxies, respectively, whereas spirals and irregulars contribute $\sim32.1\%$ and $\sim42.8\%$, respectively. The dE$_{blue}$ galaxies, which are recently found populations of galaxies, contribute a significant fraction to the dwarf galaxies. There seems to be structural difference between dSph and dE galaxies. The dSph galaxies are fainter and bluer with shallower surface brightness gradient than dE galaxies. They also have lower fraction of galaxies with small axis ratios ($b/a \lesssim 0.4$) than dE galaxies. The mean projected distance to the nearest neighbor galaxy is $\sim260$kpc. About $1\%$ of local galaxies have no neighbors with comparable luminosity within a projected distance of 2Mpc.

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