The Cosmic Evolution Survey (COSMOS) is an astronomical survey designed to probe the formation and evolution of galaxies as a function of both cosmic time (redshift) and the local galaxy environment. The survey covers a 2 square degree equatorial field with imaging by most of the major space-based telescopes and a number of large ground based telescopes, with many ongoing surveys. Over 2 million galaxies are detected, spanning 75% of the age of the Universe. The COSMOS survey involves more than 100 scientists in a dozen countries.
For website content comments or questions please contact Jacinta Delhaize - jacinta [at] phy.hr
Quiescent galaxies do not form stars anymore, however, their population averaged size is increasing over time. Using stacked zCOSMOS spectra, Fagioli et al. measured their ages as a function of size and find that small galaxies are older than large ones. This indicates that the increase of the average size of quiescent galaxies with cosmic time is due to the addition of newly quenched, bigger star-forming galaxies at later times to the quiescent population. This is not true anymore for the most massive galaxies, which individually grow in size, possibly due to dry mergers.
Image: A massive quiescent elliptical galaxy in the local Universe.
Our proposal "Completing the legacy of UltraVISTA" on COSMOS has been accepted.
In the next 3 years, the VISTA telescope will image the COSMOS field (1.5 on 1.5 degrees) to its final depth in J, H, and Ks. It will finally reach equal depth across the whole field in these filters. In three years time, we will be able to reach 26, 25.7, and 25.3 AB magnitudes (5-sigma) in J, H, and Ks, respectively. This will double the area on COSMOS at this depth and will be an important step for better measurements and the identification of high redshift galaxies.
Stay tuned for the next data release!
This new study uses the COSMOS survey to measure the local environment (density) around galaxies at z < 3 and connects it to their star formation rates. The study suggests that the shutdown of star formation due to galaxies falling into dense environment (e.g., causing stripping and heating of gas) is dominant at z < 1. At higher redshifts, quenching of star formation is likely triggered by galaxy internal processes (feedback, etc).
The paper is accepted and ready to be checked out: http://arxiv.org/abs/
Image: An example of a jellyfish galaxy where 'tentacles' of gas are being stripped off the host galaxy due to its interaction with the hot gas in the cluster environment