Simulation Recipes

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Massively Under Construction

(i.e. don't believe what you see here yet, or ask me when it doesn't make sense :)

Nearby edge-on spiral

Roughly modeled after NGC891

  • model data: Milky Way 13CO from the Galactic Ring Survey on the 14m FCRAO
  • units: K - first convert to flux surface brightness

[math]\displaystyle{ \frac{Jy}{Sr} = \frac{4\times 10^{23} k T}{\pi D^2 \Omega} }[/math], where [math]\displaystyle{ \Omega }[/math] is the beam solid angle. At 110GHz the factor is [math]\displaystyle{ 2x10^8 }[/math]

now we need to decide if this model data will work at the desired pixel scale

  • the GRS resolution of 40" at ~10kpc is 0.04" at 10Mpc, so we should be able to do a simulation of observing at ~0.1-0.2". 100pix indicates that for ALMA at 100GHz, configuration 20 is appropriate.
  • if we intend to set cell=0.04arcsec in simdata, then the cube needs to be multiplied by

[math]\displaystyle{ 2x10^8 * (.04/206265)^2 = 7.9x10^{-6} }[/math] to obtain Jy/pixel. The cube peaks at ~3K, so we can perform the simulation with inbright=2.3e-5

will we be dominated by the noise in the input model?

  • input noise ~150mK or S/N~20, so at our scaled intensity, a few mJy/bm. The exposure time calculator says that ALMA will achieve 1.3mJy/bm in an hour, so we should set this up as a half hour snapshot.