Three of the galaxies in the TIMER sample are shown above, with our MUSE fields shown as white squares. These are images from the beautiful Carnegie-Irvine Galaxy Survey. For each of the 21 TIMER galaxies we have obtained more than 90000 spectra across a field of about 6 x 6 kpc on average.

Highlights from our main discoveries so far

Stellar populations in bars.  How do the ages of stars vary across bars? It turns out that idealised models of isolated galaxies had predicted that stars should be younger close the bar major axis. Given the excellent quality of the TIMER data, we were able to test and confirm this prediction (again for the first time!) in the work led by Justus Neumann (arXiv:2003.08946). Further, we show that cosmological simulations are currently also able to reproduce this behaviour. In this study we also discovered that most bars are more metal-rich than their surroundings.

 

Inner bars. Most disc galaxies host bars, a central stellar structure where stars move along elongated orbits around the galaxy centre. It turns out that many such galaxies hosts as well an inner bar. We studied in detail two such inner bars in the galaxies NGC 1291 and NGC 5850, and we found that such inner bars appear to form just like main bars, i.e., from dynamical instabilities in a stellar disc (where stars move along near circular orbits). In addition, we found evidence that inner bars are also long lived, just as main bars. These results can be found in the paper by Adriana de Lorenzo Cáceres (arXiv:1901.06394). In a related study led by Jairo Méndez-Abreu (arXiv:1811.03855), we discovered by chance the first box/peanut in an inner bar. Box/peanuts are structures that form from dynamical instabilities in the central parts of bars, changing stellar orbits such that the structure looks like a peanut when seen from certain directions. Box/peanuts are common in main bars, but this is the first time it is observed in an inner bar. This discovery strengthens the case that inner bars are just like main bars, following the same orbital structure and dynamical evolution.

Stellar feedback from nuclear rings. One of the main processes driven by bars is the funnelling

of gas to the central regions of the galaxy. Shocks on the leading edges of bars remove

angular momentum from gas in the interstellar medium, which then streams down

along the bar. The in-falling gas stops at the region where the orbital structure of

the bar leads to more circular orbits perpendicular to the bar, which often results

in star-forming nuclear rings. In the galaxy NGC 3351, new stars are being

formed through this process at a very high rate. Combining our MUSE TIMER

data with data from ALMA, we found that the young stars in the nuclear ring

not only heat up the gas around them, but also blows it away from the galaxy

centre at speeds of 70 km/s. We also see that cold molecular gas surrounding the

nuclear ring gets pushed back by the warm gas. In the picture on the right, the

expanding, warm gas detected with MUSE is shown in orange shades, while the

cold gas detected with ALMA is shown in blue shades. The start-bursting nuclear

ring is the whitish structure that is elongated vertically in the picture. These results

were published in the paper led by Ryan Leaman (arXiv:1907.13142) and advertised in a

ESO Picture of the Week release.

The ages of bars and the settling of disc galaxies. When the MUSE instrument was still a newcomer at the La Silla Paranal Observatory, our team has published a pilot study led by Dimitri Gadotti (arXiv:1509.00032), where we showed that we can provide an estimate to when a bar has formed in a galaxy by studying the star formation history of the nuclear ring formed by the bar. Essentially, since the stars in the ring form from gas brought to the central regions by the bar, the oldest star therein have an age that is a lower limit to the age of the bar. In fact, in this study we found a very old bar, with an age of about 10 Gyr, which implies that (i), bars can be robust structures, and (ii), some bars are formed at redshifts as high as z ~ 2. The TIMER project (see paper 1) was born from that pilot study, with the aim of estimating the ages of bars for 24 nearby barred galaxies. An important aspect of this work is that a bar can only develop in a galaxy when the main disc is dynamically settled. Therefore, our work will also provide estimates for the time when discs settle, which is a very important observational constraint to models of galaxy formation and evolution. In addition, as our sample spans a range in stellar mass, we will also be able to test the downsizing scenario, in which discs settle (and bars form) in more massive galaxies first.