Faint star-forming galaxies at z \sim 2 - 3 can be used as alternative background sources to probe the Lyman- \alpha forest in addition to quasars , yielding high sightline densities that enable 3D tomographic reconstruction of the foreground absorption field .
Here , we present the first data release from the COSMOS Lyman-Alpha Mapping And Tomography Observations ( CLAMATO ) Survey , which was conducted with the LRIS spectrograph on the Keck-I telescope .
Over an observational footprint of 0.157 \mathrm { deg } ^ { 2 } within the COSMOS field , we used 240 galaxies and quasars at 2.17 < z < 3.00 , with a mean comoving transverse separation of 2.37 h ^ { -1 } \mathrm { Mpc } , as background sources probing the foreground Lyman- \alpha forest absorption at 2.05 < z < 2.55 .
The Lyman- \alpha forest data was then used to create a Wiener-filtered tomographic reconstruction over a comoving volume of 3.15 \times 10 ^ { 5 } h ^ { -3 } \mathrm { Mpc ^ { 3 } } with an effective smoothing scale of 2.5 h ^ { -1 } \mathrm { Mpc } .
In addition to traditional figures , this map is also presented as a virtual-reality visualization and manipulable interactive figure .
We see large overdensities and underdensities that visually agree with the distribution of coeval galaxies from spectroscopic redshift surveys in the same field , including overdensities associated with several recently-discovered galaxy protoclusters in the volume .
Quantitatively , the map signal-to-noise is \mathrm { S / N ^ { wiener } } \approx 3.4 over a 3 h ^ { -1 } \mathrm { Mpc } top-hat kernel based on the variances estimated from the Wiener filter .
This data release includes the redshift catalog , reduced spectra , extracted Lyman- \alpha forest pixel data , and reconstructed tomographic map of the absorption .
These can be downloaded from Zenodo ( \url https : //doi.org/10.5281/zenodo.1292459 ) .