Galaxy formation and evolution at redshifts z>1

The FourStar Galaxy Evolution Survey (ZFOURGE) is a large and deep medium-band imaging survey aimed at establishing an observational benchmark of galaxy properties at redshift z > 1. ZFOURGE survey is carried out using an extremely efficient near-infrared FOURSTAR instrument on the Magellan telescope, in three HST legacy fields: COSMOS, CDFS, and UDS.

Accurate redshifts for ~30,000 galaxies at z>1

Most normal L* galaxies at 1 < z < 3 are too faint for spectroscopic observations, which has forced us to rely on inaccurate broadband photometric redshifts in the past. In response, we have equipped FourStar with innovative “medium-bandwidth” filters from 1 − 1.8μm, which enable accurate and robust redshifts with 1-2% accuracy of ~30,000 galaxies at z>1.

High-redshift universe at z=6-9

One of the quests of galaxy formation studies is to trace back the evolutionary history of galaxies directly to the birth of the first population of stars. ZFOURGE opens up the exciting possibility of identifying the brightest z ~ 8 galaxies, by selecting galaxies that are not detected in the J1-filter, but clearly detected in the J2 + J3-bands, essentially providing a low resolution spectroscopy(R~10). We expect to find 3 − 9 galaxies at z ~ 8 per deep FourStar pointing, placing strong constraints on the shape of the luminosity function and providing extremely compelling candidates for spectroscopic follow up.

We greatly acknowledge support from the Carnegie Observatories and the staff at the Las Campanas observatories during this survey.