FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope


Recently, high angular resolution continuum surveys of the Galactic plane such as GLIMPS & MIPSGAL by Spitzer, Hi-GAL by Herschel and AKARI have been carried out at the mid- and far-infrared. Submm surveys of Galactic plane were also conducted by some groups, such as ATLASGAL, BGPS and SUCUBA-2 surveys.
These surveys made a great contribution to identify star forming activity, and revealed detailed structure of molecular clouds, filaments and dense clumps thought to be sites of massive star and cluster formation but they lack the velocity information. On the other hand, 3-dimensional data obtained by observations of spectral lines provide crucial information to reveal their dynamical state and interaction of molecular clouds. Therefor, Survey of the Galactic plane in spectral lines with wide coverage and enough angular resolution to comparable to the IR surveys are highly required.

FUGIN Project

Recent improvement of surface accuracy of the Nobeyama 45-m Telescope and the new multi-beam receiver "FOREST" realized large-scale mapping observations of the Galactic plane with high angular resolution within a short time. That is ”FUGIN” (FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope).
Using the multi-beam receiver FOREST, we will carry out OTF mapping of the Galactic plane and the outer disk in 12CO, 13CO, and C180 J=1-0 transition, simultaneously. This is the CO Galactic Plane Survey by simultaneous 3 CO lines with the highest angular resolution(-20”). Moreover, we can resolve structures of both diffuse gas and dense gas in molecular clouds at once by simultaneous 3 CO J=1-0 lines tracing different density regions.

Observing strategy

Mapping area

  • 1st quadrant l: 10° -50° b: ±1°(80 deg2)
    (inner disk: spiral arms, interarm, bar/barend)
  • 3rd quadrant l: 198°-236° b: ±1° (76 deg2)
    (outer disk: comparison with inner disk)

Observation Plan

  • Lines: 12CO, 13CO, C18O J=1-0 (simultaneously)
  • SAM45 spectrometer: BW=1000MHz, 4096ch
  • Simultaneous 12CO, 13CO, C18O observations
  • Velocity resolution: 1.3 km/s (df=244.14kHz-->0.65 km/s)
  • Scans: the 1st quadrant: X and Y scans, the 3rd quadrant: X scan

Target Sensitivity

  • Trms(Ta*) =0.12K @13CO dv= 1.3 km/s @Tsys=150K
  • Trms(Ta*) =0.12K @12CO dv= 5 km/s (-0.24 K dv=1.3 km/s) @Tsys=250K

See Umemoto, T. et al. 2017, PASJ, 69, 78