Table 1.
Comparison of search volumes and depth for previous, serendipituously found high-z QSO pairs.
| Publication | No. of pairs | z-range | Separation | Depth | Comments |
|---|---|---|---|---|---|
| (arcsec)/(cMpc) | (AB mag) | ||||
| Shen et al. (2010) | 7 | 2.9–3.5 | –/1.0 | i < 21.0 | 1 |
| 8 | 3.5–4.5 | –/1.2 | i < 21.0 | 1 | |
| Schneider et al. (2000) | 1 | 4.0–4.5 | 33/1.2 | i < 21.0 | 2 |
| McGreer et al. (2016) | 1 | 4.77–5.27 | 21/0.8 | z < 21.4 | 3 |
| Djorgovski et al. (2003) | 1 | 4.8–5.0 | 160/6.2 | z < 23.1 | 4 |
| This paper | 0 | 5.6–6.6 | 3–80/3.3 | z < 22.8 |
Notes. (1)Out of 319 binary candidates, follow-up spectroscopy ‘is about half finished’ (Hennawi et al. 2010). Based on the spectroscopic follow-up, Shen et al. (2010) derive a search completeness of 0.38 and 0.52 for the low-z and high-z sub-sample, respectively. These completeness fractions are used in computing wp for Fig. 3. (2)The second QSO of the pair was serendipitously in the slit, so we use the pair separation of 33″ even though it does not correspond to an azimuthally complete search cone. (3)The second QSO of the pair was serendipitously in the slit, so we use the pair separation of 21″. (4)The redshift depth is taken as the highest redshift QSO found in the parent sample. The search radius is estimated from the imaging FOV and guessing a 1 arcmin loss in the side-length due to dithering.
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