부산대학교 도서관

We study the spatially resolved properties of 343 elliptical galaxies with the MaNGA/SDSS-IV survey. We used the DESI Legacy Imaging Surveys for morphological classification. Based on integrated spectroscopic properties and colors, we classified seven classes of ellipticals. We inferred the stellar age and metallicity ($Z$) gradients out to a 1.5 effective radius of classical "red and dead", recently quenched, and blue star-forming ellipticals (CLEs, RQEs, and BSFs), corresponding to 73%, 10%, and 4% of the sample, respectively. We reconstructed their global and radial histories of star formation and mass growth. We find the mass- and luminosity-weighted age gradients of CLEs are nearly flat or mildly negative. The respective $Z$ gradients are negative, being flatter as the mass is smaller. The more massive CLEs formed stars earlier and quenched faster than the less massive ones. The CLEs show a weak inside-out growth and a clear inside-out quenching. They finished their quenching globally 3.8 $\pm$ 1.2 Gyr ago, with quenching time-scales of 3.4 $\pm$ 0.8 Gyr. At masses < 10$^{11}$ $M_{\bigodot}$, the age and $Z$ gradients of the RQEs and BSFs are flatter than those of the CLEs but with larger scatters. They show very weak inside-out growth and quenching, which is slow and even not completed at $z\sim0$ for the BSFs. Instead, the massive RQEs show an outside-in quenching and positive gradients in the luminosity-weighted age and stellar metallicities. The RQEs of all masses quenched 1.2 $\pm$ 0.9 Gyr ago on average. Our results for the CLEs are consistent with a two-phase scenario where their inner parts formed by an early and coeval dissipative collapse with a consequent burst of star formation and further quenching, whereas the outer parts continued their assembly likely by dry mergers. We also discuss some evolutionary scenarios for the RQE and BSF galaxies.
Comment: 24 pages and 18 figures without appendix. We added Table 1 with a list of acronyms. Original article published in Astronomy & Astrophysics