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We investigate 35 pre-stellar cores and 36 proto-stellar cores in the Perseusmolecular cloud. We find a very tight correlation between the physicalparameters describing the N2H+ and NH3 gas. Both the velocity centroids and theline widths of N2H+ and NH3 correlate much better than either speciescorrelates with CO, as expected if the nitrogen-bearing species are probingprimarily the dense core gas where the CO has been depleted. We also find atight correlation in the inferred abundance ratio between N2H+ and para-NH3across all cores, with N(p-NH3)/N(N2H+)= 22 +/- 10. We find a mild correlationbetween NH3 (and N2H+) column density and the (sub)millimeter dust continuumderived H2 column density for pre-stellar cores, N(p-NH3)/N(H2) ~ 10e-8, but donot find a fixed ratio for proto-stellar cores.  The observations suggest that in the Perseus molecular cloud the formationand destruction mechanisms for the two nitrogen-bearing species are similar,regardless of the physical conditions in the dense core gas. While theequivalence of N2H+ and NH3 as powerful tracers of dense gas is validated, thelack of correspondence between these species and the (sub)millimeter dustcontinuum observations for proto-stellar cores is disconcerting and presentlyunexplained.

Dense Gas Tracers in Perseus: Relating the N2H+, NH3, and Dust Continuum Properties of Pre- and Proto-Stellar Cores