Bar ages derived for the first time in nearby galaxies

Insights into secular evolution from the TIMER sample

¹ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Región Metropolitana, Chile
² Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
³ Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁴ Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Rua do Matão 1226, 05508-090 São Paulo, SP, Brazil
⁵ Universidad de La Laguna, Departamento de Astrofísica, Avda. Astrofísico Francisco Sánchez S/N, E 38206 La Laguna, Tenerife, Spain
⁶ Instituto de Astrofísica de Canarias, C/ Vía Láctea, S/N, E-38205 La Laguna, Tenerife, Spain
⁷ Instituto de Física de Partículas y del Cosmos (IPARCOS), Universidad Complutense de Madrid, 28040 Madrid, Spain
⁸ Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 41566, Republic of Korea
⁹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁰ Observatorio Astronómico Nacional (IGN), C/ Alfonso XII 3, E-28014 Madrid, Spain
¹¹ Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, 1180 Wien, Austria

^⋆ Corresponding author: camila.desafreitas@eso.org

Received: 9 December 2024
Accepted: 26 March 2025

Abstract

Once galaxies settle their discs and become self-gravitating, stellar bars can form, driving the subsequent evolution of their host galaxy. Determining the ages of bars can therefore shed light on the epoch of the onset of secular evolution. For this work we applied the first broadly applicable methodology to derive bar ages to a sample of 20 nearby galaxies. The method is based on the co-eval build-up of nuclear structures and bars, and involves using integral field spectroscopic (IFS) data from the Multi Unit Spectroscopic Explorer (MUSE) instrument on the Very Large Telescope to disentangle the star formation history of the nuclear disc from the background population. This allows us to derive the formation epoch of the nuclear disc, and thus of the bar. We estimated the bar formation epoch of nearby galaxies, mostly from the TIMER survey, and have created the largest sample of galaxies with known bar ages to date. We find bar formation epochs varying between 1 and 13 Gyr ago, illustrating how disc-settling and bar formation are processes that first took place in the early Universe and are still taking place in some galaxies. We infer the bar fraction over cosmological time with our sample, finding remarkable agreement with that obtained from direct studies of galaxies at high redshifts. Additionally, for the first time, we were able to investigate secular evolution processes taking into account the ages of bars. Our results agree with the scenario in which bars aid the quenching of the host galaxy; galaxies that host older bars tend to be more quenched. We also find that older bars tend to be longer and stronger, and to host larger nuclear discs. Furthermore, we find evidence that the nuclear disc stellar mass builds up over time. On the other hand, we find no evidence that downsizing plays a role in bar formation since we find that bar age is independent of galaxy stellar mass. With the means to estimate bar ages, we can begin to understand better when and how bars shape the observed properties of disc galaxies.