The sky density of quasars is low. To observe ~1000 quasars simultaneously on the sky we require wide-field spectrographs and imagers.


The SDSS telescope and the BOSS spectrograph provide an ideal choice to observe the single RM field, with a 7 deg2 field of view and 1000 fibers per plate. The spectroscopy was performed with the BOSS spectrograph on the 2.5m SDSS telescope, during Jan to July in 2014. The observations were executed in service mode by the SDSS-III survey team.

Among the 1000 fibers, 849 were assigned to RM quasar targets; 1 was assigned to a galaxy target per BOSS tiling requirement; 70 were assigned to spectrophotometric F stars; 80 were assigned to sky observations.


The wide-field imaging came from two telescopes with a degree-size imager. The 3.6m CFHT telescope is equipped with MegaCam, a 1x1 deg FoV imager, which was used to perform two-band imaging (g and i) during dark/gray time in 2014 Feb to July at a cadence of 2 days. The University of Arizona Bok 2.3m telescope is equipped with 90Prime, a prime focus wide-field imager with a ~1x1 deg FoV, which was used to obtain two-band imaging mostly during bright time in the same monitoring period. In addition, we obtained six nights of KPNO-4m (Mayall) time to perform Ugriz imaging of the RM field with MOSAIC, in 3 dark runs (Feb, Apr and Jun).

The RM Field

The RM field (RA/DEC=14:14:49.00+53:05:00.0) lies within the CFHT-LS W3 field, and coincides with the Pan-STARRS 1 (PS1) Medium Deep Field MD07, with 4 years of multi-band early PS1 light curves. It encloses the 0.5-1 sq. degree AEGIS field of the Extended Groth Strip with extensive multi-wavelength coverage. The CFHT-LS D3 field is also covered by this field.

This field has a good annual visibility window from APO, and has been fully or partially covered by various multi-wavelength facilities such as Chandra and HST.

The Quasar Sample

The quasar sample is a flux-limited (i<21.7), spectroscopically confirmed broad-line quasar
sample that covers a wide redshift range (0.1<z<4.5).

We mak
e no additional cuts on quasar properties to ensure a uniform selection. For the 6-month baseline program, only low-z quasars can be detected a lag due to the time dilation. However, by combining early PS1 photometry and continued spectroscopic monitoring in the SDSS-IV era (starting in July 2014), a large number of lags on >6 mo timescales can be detected, providing a complete coverage of the redshift-lag plane shown on the right.   

The Baseline Program

The baseline program had a length of 6 months (2014A semester) over 7 dark/grey runs, with 3-6 BOSS spectroscopic epochs per run (cadence of a few days). Each spectroscopic epoch performed simultaneous spectroscopy for ~ 850 flux-limited quasars in a single, 7 deg2 field. The photometric monitoring came from CFHT/MegaCam (dark time), Bok 2.3m/90Prime (bright) and KPNO-4m/MOSA (dark time), and had a cadence of ~ 2 days over the same period, covering both dark and bright times.

The Extended Program

The SDSS-RM field will continue to be monitored by the BOSS spectrograph through 2016, albeit with a lower cadence. These additional spectroscopic epochs, when combined with four prior years of photometric light curves from PanSTARRS 1 and SDSS-RM, will enable the detection of long (>6 months) lags in our RM sample.

Science Cases

The unique dataset from SDSS-RM will enable an array of applications for RM science and general quasar science.

RM science

  1. BLR lag detections

  2. BLR size-luminosity (R-L) relations

  3. Host - RM BH mass correlations

General quasar science

  1. Photometric and spectral quasar variability

  2. Broad absorption trough variability

  3. Deep spectroscopy of quasar absorption lines

  4. High-resolution and deep imaging of quasar hosts

  5. Spectral decomposition of AGN and host components

  6. Multi-wavelength synergy on RM quasars