Resolved properties of classical bulge and pseudo-bulge galaxies

Abstract

We compare properties of classical and pseudo-bulges and properties of their hosting galaxies selected from the MaNGA survey. Bulge types are identified based on the S$\mathrm{\acute{e}}$rsic index n of bulge component and the position of bulges on the Kormendy diagram. For the 393 classical bulges and 422 pseudo-bulges selected and their hosting galaxies, we study their kinematic properties including a proxy for specific angular momentum and central velocity dispersion, their stellar population properties including stellar age, metallicity, and specific star formation rate, as well as HI fractions of the galaxies. Our results show that at given stellar mass, disc components of pseudo-bulge galaxies are younger, have more active star formation, rotate more, and may contain more HI content compared with those of classical bulge galaxies, and the differences are larger than those between bulges themselves. The correlations between bulge types and disc properties indicate that different types of bulges are shaped by different processes that may regulate both growth of central components and evolution of outer discs in galaxies. In addition, we propose a stellar mass dependent divider of central velocity dispersion to separate galaxies with classical bulges from those with pseudo-bulges in galaxy mass range of $10.4<\mathrm{log}(M_*/\rm M_\odot )<11.4$: $\mathrm{log}(\sigma _0) = 0.23 \times \mathrm{log}(M_*/\rm M_\odot )-0.46$. Galaxies with larger/smaller σ0 can be classified as hosts of classical/pseudo-bulges.

Grand Design versus Multiarmed Spiral Galaxies: Dependence on Galaxy Structure

“…The percentage of classical bulges is known to increase with increasing stellar mass. Classical bulges dominate above log (M * /M ☉ ) ∼10.5, while pseudo-bulges are more common at lower masses (Sachdeva et al 2020;Hu et al 2024). The tendency of grand design galaxies to have earlier Hubble types and larger concentrations for a given mass may also favor classical bulges.…”

“…Their catalog includes the results of fits to the SDSS surface-brightness profiles of the galaxies. Following Hu et al (2024), for this comparison we limited the sample to galaxies with a reliable two-component fit (bulge plus disk) by setting the parameters FLAG_FIT = 2 and FLAG_FAILED_SE = 0, and requiring the half-light radius for the disk component to be larger than that for the bulge component and the half-light radius of the bulge to be larger than 0 75 (about the half-width halfmaximum point-spread function). A total of 41 and 32 of our multiarmed and grand design galaxies, respectively, meet these criteria.…”