Hawaii Two-0 Science


1. “Euclid Preparation. TBD. The Cosmic Dawn Survey (DAWN) of the Euclid Deep and Auxiliary Fields” (McPartland et al. 2024)Submitted

2. “Euclid preparation. TBD. Cosmic Dawn Survey: Data release 1 multiwavelength catalogues for Euclid Deep Field North and Euclid Deep Field Fornax” (Zalesky et al. 2024)Submitted

3. “A Machine Learning Approach to Predict Missing flux Densities in Multi-band Galaxy Surveys” (Chartab et al. 2022)

4. “Hawaii Two-0: high redshift galaxy clustering and bias” (Beck et al. 2020)

5. “Measuring Linear Galaxy Bias at High Redshift using the H20 Survey” (Murphree et al. in prep)

6. “Properties of ~1500 Massive High-Redshift Galaxies in the H20 Survey” (Valdes et al. in prep)

Research Projects

Preliminary Stellar Mass Function

Lead: Zalesky

Spectra Catalogue & Protoclusters

Leads: Chartab, Taamoli

Massive High-Redshift Galaxies

Lead: Valdes

Linear Galaxy-Dark Matter Bias

Lead: Murphree

Stellar-to-Halo Mass

Leads: Shuntov, Zalesky, Weaver

High-Redshift Dropout Galaxies

Lead: McPartland

Cluster Properties & Metallicity

Lead: Murphree

Main-Sequence at High-Redshift

Lead: McPartland

Ultraviolet Luminosity Function

Lead: Allen

Morphology & Mergers

Leads: McPartland, Valdes


High-Redshift Dropout Galaxies

Lead: McPartland

To provide estimates for the ultimate outcomes of the H20 survey, we have identified a sample of high-redshift galaxies using available ultra-deep (limiting mag. ≥27) HSC data in the COSMOS Deep Field. “Dropout” galaxies were selected using standard Lyman break galaxy color selection criteria based on the analysis of Ono et al. (2018). At the conclusion of the H20 observing program, we expect to have a final sample of:

Dropout selection:

Band Redshift Detected Sources
COSMOS 2 sq. deg
Expected Sources
H20 20 sq. deg
g 4 72,098 ~720,000
r 5 3,814 ~40,000
i 6 262 ~3000
z 7 46 ~500

Photo-z selection

2,00,000+  galaxies @ z~3

3,00,000+  galaxies @ z~2

Linear Galaxy-Dark Matter Bias

Lead: Murphree

We have developed an analysis pipeline that measures the linear galaxy-dark matter bias for a galaxy survey. In preparation for the H20 survey, we developed this pipeline on the SSP Deep/UltraDeep survey around the COSMOS field. This pipeline can sort sources into dropout bands or redshift bins specified by photometric redshifts. We measure the angular two-point correlation function for each bin and compare it with the expected density power spectrum from concordance cosmology (fit shown in the figure).

Massive High-Redshift Galaxies

Lead: Valdes

Using 4.6 square degrees across the NEP and EDFF fields, we’ve selected a sample of ~1500 galaxies with masses log(M*)>10.5 at 3.5>z>5.8. With this sample, we’ve investigated the mass-size relationship as a function of redshift, in the figure below. We find reasonable agreeement between our fits (blue lines) and Eq. (4) of Mowla et al. (2019), extrapolated to our redshift range using the equations for α and lnA on page 12, paragraph 4 (red lines). Our sources, however, are more compact than predicted based on this extrapolated relationship. 


Figures from H20 Proposal


Dark matter density map at 4.3 < z < 5.3 over 20 deg2 , from the Millennium Simulation (Springel et al. 2005), while small rectangle and circle are comparable to CANDELS and COSMOS respectively. Only H20 has the statistical power to study the rare overdensity peaks (dark orange) and cosmic voids (dark purple) as well as characterizing the overall density field needed for cosmology.

Galaxy stellar mass functions with 1σ statistical errors from existing (hatched) and proposed (solid) data. H20 will improve the constraints by a factor of > 10, thus allowing us to make a more definitive measurement of the overall mass function, link it to the dark matter via clustering, and characterize differences as a function of local environment.
Three proposed models of the galaxy SMF at z~6 are shown, along with current data (shaded area, Grazian et al. 2015) and proposed constraints (red circles, with error bars including expected uncertainties from Poisson noise, cosmic variance, and SED fitting). The three models (solid, dashed, dotted lines) have radically different implications for galaxy evolution in the early universe (e.g. Davidzon et al. 2017). H20 will clearly differentiate between these models. When combined with the proposed clustering measurements it will also directly measure the duty cycle of star formation (e.g. determining typical star formation histories).
Sensitivity limits in the HSC filters of this proposal (blue), along with the IRAC ch. 1 and 2 from our ongoing SLS program (red) and the designed NIR filters of Euclid (green). Light and dark grey lines show spectral energy distributions (SEDs) of two galaxies at z ~ 2.5 and 7 respectively, which the deep H20 imaging will be able to disentangle. To confirm and characterize this differentiation the proposed Keck follow-up is essential.
Stellar-to-halo mass ratio (SHMR) at z~5 from state-of-the-art analyses. The 2 deg2 of the COSMSOS field (blue line, Coupon et al. in prep.) still suffer large statistical uncertainties at z ~ 5 (shaded area). HSC-SSP Wide estimates (Harikane et al. 2016) are apparently more precise, but they rely on MUV converted into stellar mass through average ad-hoc assumptions. Both samples cannot constrain the most massive regime while in the cosmic volume probed by H20 we expect to find at least ~ 40 halos > 7 x 1012 M⊙. Moreover our data will consolidate the SHMR at Mhalo ~ 1012 M, to pin down the peak of efficiency and determine weather it evolves from z ~ 0 (dashed line) to z = 4-6.
SED fitting to our photometric baseline (g, r, i, z, y, [3.6], [4.5]) recovers the redshift of simulated galaxies with an error (normalized median absolute deviation) of σz /(1 + z) . 0.03 at z < 1.5 and z > 3, with the 1.5 < z < 3 range reaching similar performance once Eculid data are avaialable. The fraction of outliers (Δz > 0.15 σz ) is expected to be < 10%; the actual value will be quantified using our spectroscopic sample.
Difference between the intrinsic stellar mass of 3 < z < 6 galaxies and those recovered with SED fitting. When IRAC data are not available estimates have over 1.5 dex of scatter, making impossible to constrain stellar mass assembly as a function of cosmic time. The HSC-SSP survey lacks sufficiently deep IRAC data (> 0.5 dex scatter bellow M☆) except in the two 1.8 deg ultra-deep fields which are too small for the proposed science and suffer from large cosmic variance.

Synergy with Other Surveys


Spitzer Legacy Survey


Deep Calibration Fields


Likely to be target of WFIRST deep surveys.

Institute for Astronomy

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