The MOSFIRE Deep Evolution Field Survey


Overview: The MOSFIRE Deep Evolution Field (MOSDEF) survey is a large multi-year project with MOSFIRE on the Keck I telescope. With MOSDEF we observe the stellar, gaseous and chemical content of ~1500 galaxies when the Universe was 1.5 to 4.5 billion years old. The MOSDEF survey is being executed over four spring semesters, and will be completed in the spring of 2016. MOSDEF is being executed in three well-studied legacy fields with deep extensive multi-wavelength datasets: AEGIS, COSMOS, and GOODS-N. Within these fields we target the regions that are covered by the CANDELS and 3D-HST surveys, as illustrated in the figure below.

Figure 1: Footprints of MOSDEF pointings and corresponding numbers are indicated in black. Each MOSFIRE pointing is 3’ by 6’. The shaded orange regions represent the CANDELS HST WFC3/F160W coverage, and the open light blue boxes represent the 3D-HST WFC3/G141 grism pointings.

Redshift intervals and spectroscopic features: In order to quantify galaxy evolution within the MOSDEF survey, we target 3 redshift regimes, z=[1.37, 1.70], z=[2.09, 2.61], z=[2.95, 3.80]. The targeted redshift regimes are selected such that bright rest-frame optical emission lines fall within atmospheric windows. A key aspect of our survey strategy is that we cover multiple rest-frame optical emission lines for each galaxy. Thus our strategy requires 2 or 3 filters per slit mask, as illustrated in Figure 2 below. For the z = [1.37, 1.70] interval, we target Hβ and [OIII] in the J-band and Hα, [NII], and [SII] in the H band. For 1.61<z<1.70, we target [OII] in the Y-band. These same features appear in J, H, and K for the z = [2.09,2.61] interval. For the z = [2.95,3.80] interval, [OII] falls in the H-band, and Hβ and [OIII] in the K-band. We are also targeting several continuum features and absorption lines in each of our three redshift regimes, including the 4000 Angstrom break, CaII H and K, Mgb and Balmer lines in absorption.

Status: We have completed our 2nd observing semester, and so far have obtained rest-frame optical spectra for nearly 600 galaxies.

Figure 2: MOSFIRE visibility of various rest-frame optical emission and absorption features as a function of redshift. Each row represents a different spectral feature. The primary emission line features are indicated in bold, and the wavelengths of the lines are given in vacuum. Each color represents a different filter, as indicated in the top right. The response curves are used for each filter and feature, and thus the brightness reflects the relative throughput at the corresponding redshift.