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We present a survey toward 16 Low Luminosity Objects (LLOs with an internalluminosity, Lint, lower than 0.2 Lsun) with N2H+ (1-0), N2H+ (3-2), N2D+ (3-2),HCO+ (3-2) and HCN (3-2) using the Arizona Radio Observatory Kitt Peak 12mTelescope and Submillimeter Telescope. Our goal is to probe the nature of thesefaint protostars which are believed to be either very low mass or extremelyyoung protostars. We find that the N2D+/N2H+ column density ratios of LLOs aresimilar to those of typical starless cores and Class 0 objects. The N2D+/N2H+column density ratios are relatively high (> 0.05) for LLOs with kinetictemperatures less than 10 K in our sample. The distribution of N2H+ (1-0) linewidths spreads between that of starless cores and young Class 0 objects. If weuse the line width as a dynamic evolutionary indicator, LLOs are likely youngClass 0 protostellar sources. We further use the optically thick tracers, HCO+(3-2) and HCN (3-2), to probe the infall signatures of our targets. We derivethe asymmetry parameters from both lines and estimate the infall velocities byfitting the HCO+ (3-2) spectra with two-layer models. As a result, we identifyeight infall candidates based on the infall velocities and seven candidateshave infall signatures supported by asymmetry parameters from at least one ofHCO+ (3-2) and HCN (3-2).

Properties of the Molecular Cores of Low Luminosity Objects