Семинар 241 – 19 апреля 2023 г.


Ольга Сильченко

Презентация

2304.08436 Saying Hallo to M94's Stellar Halo: Investigating the Accretion History of the Largest Pseudobulge Host in the Local Universe

Katya Gozman, Eric F. Bell, Adam Smercina, Paul Price, Jeremy Bailin, Roelof S. de Jong, Richard D'Souza, In Sung Jang, Antonela Monachesi, Colin Slater

Published 2023-04-17, 19 pages, 12 figures, 1 table; Published in ApJ on April 14, 2023

It is not yet settled how the combination of secular processes and merginggives rise to the bulges and pseudobulges of galaxies. The nearby ($D\sim$ 4.2Mpc) disk galaxy M94 (NGC 4736) has the largest pseudobulge in the localuniverse, and offers a unique opportunity for investigating the role of mergingin the formation of its pseudobulge. We present a first ever look at M94'sstellar halo, which we expect to contain a fossil record of M94's past mergers.Using Subaru's Hyper Suprime-Cam, we resolve and identify red giant branch(RGB) stars in M94's halo, finding two distinct populations. After correctingfor completeness through artificial star tests, we can measure the radialprofile of each RGB population. The metal-rich RGB stars show an unbrokenexponential profile to a radius of 30 kpc that is a clear continuation of M94'souter disk. M94's metal poor stellar halo is detectable over a wider area andclearly separates from its metal-rich disk. By integrating the halo densityprofile, we infer a total accreted stellar mass of $\sim 2.8 \times 10^8M_\odot$, with a median metallicity of [M/H] $=-$1.4. This indicates that M94'smost-massive past merger was with a galaxy similar to, or less massive than,the Small Magellanic Cloud. Few nearby galaxies have had such a low-massdominant merger; therefore we suggest that M94's pseudobulge was notsignificantly impacted by merging.