Dense Gas Tracers in Perseus: Relating the N2H , NH3, and Dust Continuum Properties of Pre- and Proto-Stellar Cores - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate




Dense Gas Tracers in Perseus: Relating the N2H , NH3, and Dust Continuum Properties of Pre- and Proto-Stellar Cores - Astrophysics > Solar and Stellar Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: 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 Np-NH3-NN2H+= 22 +- 10. We find a mild correlationbetween NH3 and N2H+ column density and the submillimeter dust continuumderived H2 column density for pre-stellar cores, Np-NH3-NH2 ~ 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 submillimeter dustcontinuum observations for proto-stellar cores is disconcerting and presentlyunexplained.



Author: Doug Johnstone, Erik Rosolowsky, Mario Tafalla, Helen Kirk

Source: https://arxiv.org/



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