SIMBAD references

The BTC40 Survey for high-redshift quasars is a multicolor search using images obtained with the Big Throughput Camera (BTC) on the Cerro Tololo Inter-American Observatory (CTIO) 4 m telescope in V, I, and z filters to search for quasars at redshifts of 4.8<z<6. The survey covers 40 deg² in B, V, and I, and 36 deg² in z. Limiting magnitudes (3 σ) reach to V=24.6, I=22.9, and z=22.9. We used the V-I versus I-z two-color diagram to select high-redshift quasar candidates from the objects classified as point sources in the imaging data. Follow-up spectroscopy with the Anglo-Australian Telescope and CTIO 4 m telescopes of candidates having I≤21.5 has yielded two quasars with redshifts of z=4.6 and z=4.8, as well as four emission-line galaxies with z~0.6. Fainter candidates have been identified down to I=22 for future spectroscopy on 8 m class telescopes.