HCN (1–0) and HCO$^+$ (1–0) in two CO-luminous post-starburst galaxies.

Data
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ALMA Observations {#sec:almaobs}
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The observations for this work were obtained during ALMA Cycle 4 (program 2016.1.00881.S; PI: French). We observe two post-starburst galaxies with CO (1–0) detections from @French2015 with representative CO luminosities and SFRs, and with redshifts and declinations enabling observations with ALMA (labeled H02 and S05). We use the Band 3 receiver (84-116 GHz) with two spectral windows to observe HCN 1–0 (88.63 GHz rest frame), HCO$^+$ 1–0 (89.19 GHz rest frame), and HNC 1–0 (90.66 GHz rest frame). The redshift of H02 pushes HCN close to the edge of the Band 3 bandwidth, so we adopt narrow spectral windows, of 417, 831, 817 km/s for the lines, respectively. These spectral windows are still much larger than the 170 km/s linewidth of the CO (1–0) line for this galaxy. For S05, we adopt wider spectral windows of 1622-1660 km/s.

The ALMA observations described here have a beam size of 1-1.5 (or 1.0-1.4 kpc), with a maximum recoverable scale of 7.6. The beam size is chosen to match the observed CO (2–1) sizes, as our companion ALMA program (2015.1.00665.S; PI: Smith; Smercina et al. in prep) 