Devang Somawanshi | Searcharxiv

arXiv2025

Chemical signature reveals co-spatial dwarf satellite of an edge-on disc galaxy with MUSE

Integral field unit (IFU) spectroscopic observations of resolved galaxies provide an optimal experimental setting for determination of stellar population properties, in particular - age, metallicity and $α$-enhancement, which are key to understanding evolution of galaxies across diverse physical environments. We determine these properties for the edge-on disc galaxy IC 1553, through stellar population models fitted to MUSE IFU observations. From our determined spatial distributions of metallicity and [$α$/Fe], we serendipitiously identify the unique chemical signature of a dwarf galaxy that is co-spatial with the luminous disc of IC 1553. The dwarf galaxy is characterized by the presence of higher [$α$/Fe] and metal-poor stellar populations relative to the disc of IC 1553. The identified dwarf is dynamically cold from its determined kinematics, consistent with being a satellite of IC 1553. From modeling the Spitzer IRAC 3.6 $μm$ image of IC 1553, we confirmed the presence of the dwarf galaxy and calculated its stellar mass to be $\sim1.28\times 10^{9} \rm~M_{\odot}$. This is the first such identification of a dwarf galaxy from its unique chemical signature in such integrated light IFU observations, even though its hidden by the luminous body of its massive host.

astro-ph.GA↗

arXiv2024

Understanding stellar populations in thin & thick discs of edge-on galaxies with MUSE -- I. The case of the reignited S0 galaxy ESO 544-27

Edge-on galaxies act as the best laboratories to understand the origin of thin and thick discs in galaxies. Measurement of spatially resolved stellar population properties in such galaxies, particularly age, metallicity and [$α$/Fe], are crucial to understanding the formation and evolution of disc galaxies. Such measurements are made possible from stellar population model fits to deep integral field spectroscopic (IFU) observations of resolved galaxies. We utilise archival MUSE IFU observations of the edge-on galaxy ESO 544-27 to uncover the formation history of its thin and thick discs through its stellar populations. We find the thin disc of the galaxy is dominated by an old ($>9$ Gyr) low [$α$/Fe] metal-rich stellar population. Its outer thick disc is dominated by an old ($>9$ Gyr) high [$α$/Fe] metal-rich component that should have formed with higher star-formation efficiency than the Milky Way thick disc. We thus find [$α$/Fe] dichotomy in ESO 544-27 with its thin and thick discs dominated by low and high [$α$/Fe] stellar populations respectively. However, we also find a metal-rich younger ($<2$ Gyr old) stellar population in ESO 544-27. The galaxy was nearly quenched until its star-formation was reignited recently first in the outer and inner thick disc ($\sim$1 Gyr ago) and then in the thin disc ($\sim$600 Myr ago). We thus find that both the low [$α$/Fe] thin and high [$α$/Fe] thick discs of ESO 544-27 are inhabited primarily by similarly old metal-rich stellar populations, a contrast to that of other galaxies with known thin and thick disc stellar population properties.

astro-ph.GA↗