English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We combine deep optical and NIR ( UBVRIzJK ) photometry from the Multiwavelength Survey by Yale–Chile (MUSYC) with redshifts from the COMBO‐17 survey to perform a large‐scale study of the rest‐frame ultraviolet (UV) properties of 674 high‐redshift (0.5 &lt;  z  &lt; 1) early‐type galaxies, drawn from the Extended  Chandra Deep Field ‐South (E‐CDFS). Galaxy morphologies are determined through visual inspection of  Hubble Space Telescope  ( HST ) images taken from the GEMS survey. We harness the sensitivity of the UV to young (&lt;1‐Gyr old) stars to quantify the  recent  star formation history of early‐type galaxies across a range of luminosities [−23.5 &lt;  M ( V ) &lt; −18]. Comparisons to simple stellar populations forming at high redshift indicate that ∼1.1 per cent of early‐types in this sample are consistent with  purely  passive ageing since  z = 2 – this value drops to ∼0.24 per cent and ∼0.15 per cent for  z = 3 and 5, respectively. Parametrizing the recent star formation (RSF) in terms of the mass fraction of stars less than a Gyr old, we find that the early‐type population as a whole shows a typical RSF between 5 and 13 per cent in the redshift range 0.5 &lt;  z  &lt; 1. Early‐types on the broad UV ‘red sequence’ show RSF values less than 5 per cent, while the reddest early‐types (which are also the most luminous) are virtually quiescent with RSF values of ∼1 per cent. In contrast to their low‐redshift ( z  &lt; 0.1) counterparts, the high‐redshift early‐types in this sample show a pronounced bimodality in the rest‐frame UV–optical colour, with a minor but significant peak centred on the blue cloud. Furthermore, star formation in the most active early‐types is a factor of 2 greater at  z ∼ 0.7 than in the local universe. Given that evolved sources of UV flux (e.g. horizontal branch stars) should be absent at  z  &gt; 0.5, implying that the UV is dominated by young stars, we find compelling evidence that early‐types of all luminosities form stars over the lifetime of the Universe, although the bulk of their star formation is already complete at high redshift. This ‘tail‐end’ of star formation is measurable and not negligible, with luminous [ −23 &lt;  M ( V ) &lt; −20.5 ] early‐types potentially forming 10–15 per cent of their mass since  z = 1, with less luminous early‐types [  M ( V ) &gt; −20.5 ] potentially forming 30–60 per cent of their mass after  z = 1. This, in turn, implies that intermediate‐age stellar populations should be abundant in local early‐type galaxies, as expected in hierarchical cosmology.

The UV colours of high‐redshift early‐type galaxies: evidence for recent star formation and stellar mass assembly over the last 8 billion years