The Formation Timescale Of Bulges In The BEARD Survey

Abstract

The study of galaxy evolution has been a subject of intense debate within the astronomical community. Interactions between galaxies and secular processes leave distinctive imprints on the properties of galaxies, contributing to their evolution. The ΛCDM cosmological model has successfully explained the large-scale structures of the universe, but the evolution of luminous structures, such as galaxies, differs from the formation history of dark matter halos. The BEARD project focuses on studying the metallicity and abundance properties of a sample of 66 massive bulgeless galaxies in the nearby universe to gain a better understanding of galactic evolution. The main objective of this work is to study the stellar populations properties in 27 galaxies from the BEARD sample, as well as to test the ability to obtain the age of galaxies in the spectral range of 4963−5443 ˚A, which lacks lines sensitive to this parameter. The data used in this study were collected using the MEGARA IFU instrument with the MR-G gratins installed in the GTC. The method used was based on a python code implementing the pPXF algorithm adapted to our needs, and utilising the MILES SSP models. To ensure that our methodology used yields consistent results, mock spectra models were developed by modifying MILES models to mimmick the MEGARA data. These mock spectra were used to study two main parameters of our analysis: regularisation and signal-to-noise ratio. Additionally, these models made it possible to determine the error associated with the method, obtaining, in general, errors of ± 1 Gyr for ages younger than 4 Gyr, and errors always less than ±6.2 Gyr for older ages. For metallicity, an error of ±0.1 dex was obtained for all [M/H] values. The scientific results of this work were based on obtaining 21 maps of stellar populations along with their respective age-metallicity plane. Overall, a variety of results were found for the different bulges. We have analysed three galaxies of the sample which are NGC 5962, NGC 4405, and NGC 1087. Also, a comparative study was performed with the CALIFA survey (M´endez-Abreu et al., 2021) in order to shed some light on the bulge formation scenario. This study demonstrated the feasibility of determining stellar populations in spectra without age-sensitive lines, using analyses of mock spectral models. It is suggested that galactic bulges in the BEARD sample are mainly formed from material in the galactic disc and undergo internal secular evolution enriched with metals from previous generations of stars.

El estudio de la evoluci´on de las galaxias ha sido objeto de un intenso debate en la comunidad astron´omica durante d´ecadas. Las galaxias, como sistemas complejos, est´an sujetas a numerosos procesos y fen´omenos que influyen en su formaci´on y desarrollo a lo largo del tiempo. Las interacciones entre galaxias, la actividad nuclear, la formaci´on de estrellas y las fusiones son solo algunos ejemplos de estos procesos que dejan huellas distintivas en las propiedades cinem´aticas, qu´ımicas y fotom´etricas de las galaxias. Para comprender mejor la evoluci´on gal´actica, se han propuesto varios modelos y teor´ıas. Uno de los modelos cosmol´ogicos m´as exitosos es el modelo ΛCDM, que ha explicado con ´exito las estructuras a gran escala del universo. Sin embargo, la evoluci´on de las estructuras luminosas, como las galaxias, difiere de la historia de formaci´on de los halos de materia oscura predichos por este modelo. En las proximidades de nuestro universo, hemos observado un n´umero de galaxias masivas que carecen de bulbo o tienen uno muy d´ebil. Esta observaci´on contradice tanto los escenarios de las galaxias tempranas tipo el´ıpticas con bulbos prominentes, como el de las galaxias tard´ıas (tipo disco). Por lo tanto, la implementaci´on bari´onica de la teor´ıa del Universo ΛCDM presenta desaf´ıos a escalas gal´acticas, especialmente en lo que respecta a la alta proporci´on de galaxias sin bulbo observadas en el Universo cercano. En este contexto, el proyecto BEARD, se ha enfocado en el estudio de las propiedades de metalicidad y abundancia en una muestra de 66 galaxias masivas sin bulbo en el Universo cercano para profundizar en el conocimiento de la formaci´on y evoluci´on gal´actica. De esta forma, se espera determinar la historia de formaci´on de estas galaxias y compararla con simulaciones num´ericas.