Groundbreaking study sheds new light on galaxy evolution

Image of the large spiral galaxy NGC 1232

Image of the large spiral galaxy NGC 1232. The colours of the different regions are well visible: the central areas contain older stars of reddish colour, while the spiral arms are populated by young, blue stars and many star-forming regions. Credit: ESO

Using Integral Field Spectroscopy (IFS1) and advanced modeling tools, Instituto de Astrofísica e Ciências do Espaço (IA) researchers Iris Breda and Polychronis Papaderos have achieved an important milestone towards solving a long standing enigma in extragalactic astronomy – the nature and formation of the central spherical component in spiral galaxies like the Milky Way.

The bulge is thought to form through two distinct routes. Classical bulges consist of ancient stars, older than the disk, because they assembled rapidly more than 10 billion years ago, prior to disks. Pseudo-bulges have stars of similar age as the disk, because they assembled gradually through a combination of dynamical processes, with continuous star formation fed by inflow of gas from the disk.

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  1. In integral field spectroscopy, the signal from each pixel on the detector is sent into a spectrograph, which then generates a spectrum, allowing for the simultaneous recording of thousands of spectra per galaxy, thus producing a spatially resolved three dimensional view of its stars and ionized gas.