Hawaii Two-0 Observing Plan

Airmass Charts for S2020B

Hawaii Two-0 Survey Footprint

The 10 deg footprint for each of the H20 fields comprised of seven HSC pointings arranged in a flower petal pattern.

*** Note: We will continue to request classical time until Subaru can develop a more robust and widely used queue system. Furthermore, due to the RA/elevation constraints of our fields, it is much more efficient to execute the observations in classical mode. ***

Limiting Magnitudes / Exposure Times for Final Survey

g r i z Y JH ch1 ch2
Limiting mag 27.5 27.5 27 26.5 26 26 24.8 24.7
HSC exposure time 1.1h 2.5h 4.1h 4.8h 9h

☆ From Euclid Deep (operations start in 2021). WFIRST will also cover this area at 26 mag 10σ (operations start mid-2020s).
† From the Euclid/WFIRST Spitzer Legacy Survey (ADS)

Following an assessment of progress through the first four semesters of our LCP, we have decided it would be prudent to descope the LCP by forgoing the HSC Y-band observations. This descope brings the total number of HSC nights down from 30N to 18N. Considering the 6 nights of successful data collection through the LCP, and an equivalent of 6 nights of archival data, we have a strong chance of reaching 100% completion of a four band (griz) imaging program for the H20 LCP. 

The HSC griz imaging in conjunction with the SLS 3.4+4.5 micron imaging will be sufficient for identifying massive galaxies at z~3-6.5, and thus does not significantly degrade our original science plan. The Y-band data will eventually be obtained by Euclid, along with JH-band observations, that will allow us to identify massive galaxies out to redshifts z~14 (if they exist!).

High-z Dropout Selection 

To confirm the ability of the Hawaii Two-0 (20 sq. deg.) survey (as designed) to robustly identify high-redshift galaxies (z≳4) using our H20 dropout selection technique, we used the UH+SSP HSC data in the COSMOS (2 sq. deg.) field to select high redshift galaxy candidates. See Dropout Selection Section of the Science Page for more details.

H20 Predictions

Dropout Band Redshift Expected Sources in
H20 20 sq. deg
g 4 ~720,000
r 5 ~40,000
i 6 ~3000
z 7 ~500

 Photo-z selected sources

Redshift Expected Sources in
H20 20 sq. deg
2 ~3,000,000
3 ~2,000,000

Note that r-band dropouts are sources that “just begin to appear” in the r-band, are clearly absent in the g-band, and robustly detected in the i-band. The above figure clearly illustrates the potential for H20 observations to detect high-redshift dropout galaxies.

Exposure Time Calculations for

DEIMOS Spectroscopy

Density of High-Redshift Dropout Targets in a DEIMOS FOV

In each DEIMOS mask (16’x4′, yellow box), we expect to collect spectra for:

60+ g-band droupouts

40 r-band droupouts

10 i-band droupouts

For comparison, we indicate the smaller LRIS FOV (6’x7.8′, red dashed box).

Expected Magnitude Distributions for the gri-band Dropouts

DEIMOS Instrument Configuration & Exposure Times

The optimal configuration for our DEIMOS spectroscopy is the 600ZD grating with the OG550 order blocking filter (green dot-dashed line below). This configuration maximizes efficiency over the wavelength range where we expect to dectect Ly-α emission in the gri-band dropout galaxies at z = 4, 5, & 6. The galaxy templates were generated using FSPS assuming a 10^10 Msun galaxy with a delayed-exponential SFH with τ = 2 Gyr and age of 1 Gyr. The signal to noise estimates are based on an exposure time of 3.5hrs with a 1 arcsec slit, 1 arcsec seeing, and an airmass of 1.3.

Institute for Astronomy

We are one of the largest university astronomy programs in the world.