ALMAzsearch

Code to plan CO redshift searches in spectral scan mode with ALMA in Cycle 2 or later.

###Installation The usual

    python setup.py install

###Usage First, you set up tunings, which are setups for ALMA spectral scans.

import astropy.units as u
import ALMAzsearch
import numpy as np
tuning3 = ALMAzsearch.scan_tuning(u.Quantity(84, u.GHz),
                                  u.Quantity(5, u.min))	

Then you chose your line templates, and set up and execute 2-line search

line_templates = ["Eyelash", "FLS3", "HLSW01"] # Names of line templates
twoline = ALMAzsearch.twoline(line_templates, ciratio=1.5)
z = np.linspace(3.5, 7.0, 500) # Redshift range to search
lir = u.Quantity(3e13, u.solLum)
n3, sn3 = twoline.sn(tuning3, z, norm=lir, applyciratio=True)

Now n3 shows the number of lines detected at each redshift (at any S/N) and sn3 gives the S/N ratios for each line as a nz by 2 array. The line list includes 12CO and [CI] lines only.

It is also possible to specify a target 500um (or other wavelength) flux density instead of a L_IR using the norm argument to twoline.sn.
This then uses a dust model based on typical DSFG parameters for red sources (see Dowell et al. 2013), although these can be adjusted. For example, to scale to a 15 mJy SCUBA2 (850um) flux density:

obs_wave = u.Quantity(850, u.um)
snu = u.Quantity(15., u.mJy)
n3, sn3 = twoline.sn(tuning3, z, norm=snu, obs_wave=obs_wave,
                     applyciratio=True)

Dependencies

This depends on a number of python packages:

• numpy version 1.7 or later.
• scipy
• astropy version 0.3 or later.
• cython

References

• More information about ALMA can be found at the ALMA Project Pages