Ages and metallicities of globular clusters in M81 using GTC/OSIRIS spectra

Luis Lomelí-Núñez; Y. D. Mayya; L. H. Rodríguez-Merino; P. A. Ovando; Jairo A. Alzate; D. Rosa-González; B. Cuevas-Otahola; Gustavo Bruzual; Arianna Cortesi; V. M. A Gómez-González; Carlos G. Escudero

arXiv · 2401.02519

Ages and metallicities of globular clusters in M81 using GTC/OSIRIS spectra

Luis Lomelí-Núñez·Y. D. Mayya·L. H. Rodríguez-Merino·P. A. Ovando·Jairo A. Alzate·D. Rosa-González·B. Cuevas-Otahola·Gustavo Bruzual·Arianna Cortesi·V. M. A Gómez-González·Carlos G. Escudero

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Abstract

We here present the results of an analysis of the optical spectroscopy of 42 globular cluster (GC) candidates in the nearby spiral galaxy M81 (3.61~Mpc). The spectra were obtained using the long-slit and MOS modes of the OSIRIS instrument at the 10.4~m Gran Telescopio Canarias (GTC) at a spectral resolution of $\sim$1000. We used the classical H$\beta$ vs [MgFe]$'$ index diagram to separate genuine old GCs from clusters younger than 3 Gyr. Of the 30 spectra with continuum signal-to-noise ratio $>10$, we confirm 17 objects to be classical GCs (age $>10$~Gyr, $-1.4<$[Fe/H]$<-$0.4), with the remaining 13 being intermediate-age clusters (1-7.5~Gyr). We combined age and metallicity data of other nearby spiral galaxies ($\lesssim18$~Mpc) obtained using similar methodology like the one we have used here to understand the origin of GCs in spiral galaxies in the cosmological context. We find that the metal-poor ([Fe/H]<$-$1) GCs continued to form up to 6~Gyr after the first GCs were formed, with all younger systems (age $<8$~Gyr) being metal-rich.

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Luis Lomelí-Núñez, Y. D. Mayya, L. H. Rodríguez-Merino, P. A. Ovando, Jairo A. Alzate, D. Rosa-González, B. Cuevas-Otahola, Gustavo Bruzual, Arianna Cortesi, V. M. A Gómez-González, Carlos G. Escudero. 2024-01-04. Ages and metallicities of globular clusters in M81 using GTC/OSIRIS spectra. https://arxiv.org/abs/2401.02519

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