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We describe the survey design, calibration, commissioning, and emission-line detection algorithms for the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). The goal of HETDEX is to measure the redshifts of over a million Lyα emitting galaxies between 1.88 < z < 3.52, in a 540 deg2 area encompassing a comoving volume of 10.9 Gpc3. No preselection of targets is involved; instead the HETDEX measurements are accomplished via a spectroscopic survey using a suite of wide-field integral field units distributed over the focal plane of the telescope. This survey measures the Hubble expansion parameter and angular diameter distance, with a final expected accuracy of better than 1%. We detail the project’s observational strategy, reduction pipeline, source detection, and catalog generation, and present initial results for science verification in the Cosmological Evolution Survey, Extended Groth Strip, and Great Observatories Origins Deep Survey North fields. We demonstrate that our data reach the required specifications in throughput, astrometric accuracy, flux limit, and object detection, with the end products being a catalog of emission-line sources, their object classifications, and flux-calibrated spectra.

We present estimates of intrinsic scatter in the Star Formation Rate (SFR) -Stellar Mass (M*) correlation in the redshift range 0.5 < z < 3.0 and in themass range 10^7 < M* < 10^11 Msun. We utilize photometry in the HubbleUltradeep Field (HUDF12), Ultraviolet Ultra Deep Field (UVUDF) campaigns andCANDELS/GOODS-S. We estimate SFR, M* from broadband Spectral EnergyDistributions (SEDs) and the best available redshifts. The maximum depth of theHUDF photometry (F160W 29.9 AB, 5 sigma depth) probes the SFR-M* correlationdown to M* ~ 10 ^7 Msun, a factor of 10-100X lower in M* than previous studies,and comparable to dwarf galaxies in the local universe. We find the slope ofthe SFR-M* relationship to be near unity at all redshifts and the normalizationto decrease with cosmic time. We find a moderate increase in intrinsic scatterwith cosmic time from 0.2 to 0.4 dex across the epoch of peak cosmic starformation. None of our redshift bins show a statistically significant increasein intrinsic scatter at low mass. However, it remains possible that intrinsicscatter increases at low mass on timescales shorter than ~ 100 Myr. Our resultsare consistent with a picture of gradual and self-similar assembly of galaxiesacross more than three orders of magnitude in stellar mass from as low as 10^7Msun.

We present estimates of intrinsic scatter in the Star Formation Rate (SFR) -Stellar Mass (M*) correlation in the redshift range 0.5 < z < 3.0 and in themass range 10^7 < M* < 10^11 Msun. We utilize photometry in the HubbleUltradeep Field (HUDF12), Ultraviolet Ultra Deep Field (UVUDF) campaigns andCANDELS/GOODS-S. We estimate SFR, M* from broadband Spectral EnergyDistributions (SEDs) and the best available redshifts. The maximum depth of theHUDF photometry (F160W 29.9 AB, 5 sigma depth) probes the SFR-M* correlationdown to M* ~ 10 ^7 Msun, a factor of 10-100X lower in M* than previous studies,and comparable to dwarf galaxies in the local universe. We find the slope ofthe SFR-M* relationship to be near unity at all redshifts and the normalizationto decrease with cosmic time. We find a moderate increase in intrinsic scatterwith cosmic time from 0.2 to 0.4 dex across the epoch of peak cosmic starformation. None of our redshift bins show a statistically significant increasein intrinsic scatter at low mass. However, it remains possible that intrinsicscatter increases at low mass on timescales shorter than ~ 100 Myr. Our resultsare consistent with a picture of gradual and self-similar assembly of galaxiesacross more than three orders of magnitude in stellar mass from as low as 10^7Msun.