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We present new IRAM 30m spectroscopic observations of the $sim88$ GHz band, including emission from the CCH (n=1-0) multiplet, HCN (1-0), HCO+ (1-0), and HNC (1-0), for a sample of 58 local luminous and ultraluminous infrared galaxies from the Great Observatories All-sky LIRG Survey (GOALS). By combining our new IRAM data with literature data and Spitzer/IRS spectroscopy, we study the correspondence between these putative tracers of dense gas and the relative contribution of active galactic nuclei (AGN) and star formation to the mid-infrared luminosity of each system. We find the HCN (1-0) emission to be enhanced in AGN-dominated systems ($langle$L$_{HCN (1-0)}$/L$_{HCO^+ (1-0)}rangle=1.84$), compared to composite and starburst-dominated systems ($langle$L$_{HCN (1-0)}$/L$_{HCO^+ (1-0)}rangle=1.14$, and 0.88, respectively). However, some composite and starburst systems have L$_{HCN (1-0)}$/L$_{HCO^+ (1-0)}$ ratios comparable to those of AGN, indicating that enhanced HCN emission is not uniquely associated with energetically dominant AGN. After removing AGN-dominated systems from the sample, we find a linear relationship (within the uncertainties) between $log_{10}$(L$_{HCN (1-0)}$) and $log_{10}$(L$_{IR}$), consistent with most previous findings. L$_{HCN (1-0)}$/L$_{IR}$, typically interpreted as the dense gas depletion time, appears to have no systematic trend with L$_{IR}$ for our sample of luminous and ultraluminous infrared galaxies, and has significant scatter. The galaxy-integrated HCN (1-0) and HCO+ (1-0) emission do not appear to have a simple interpretation, in terms of the AGN dominance or the star formation rate, and are likely determined by multiple processes, including density and radiative effects.
We present IRAM-30m Telescope $^{12}$CO and $^{13}$CO observations of a sample of 55 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in the local universe. This sample is a subset of the Great Observatory All-Sky LIRG Survey (GOALS),
We report the results of interferometric HCN(1-0) and HCO+(1-0) observations of four luminous infrared galaxies (LIRGs), NGC 2623, Mrk 266, Arp 193, and NGC 1377, as a final sample of our systematic survey using the Nobeyama Millimeter Array. Our sur
Far-infrared (FIR) images and photometry are presented for 201 Luminous and Ultraluminous Infrared Galaxies [LIRGs: log$(L_{rm IR}/L_odot) = 11.00 - 11.99$, ULIRGs: log$(L_{rm IR}/L_odot) = 12.00 - 12.99$], in the Great Observatories All-Sky LIRG Sur
Gravitational accretion accumulates the original mass, and this process is crucial for us to understand the initial phases of star formation. Using the specific infall profiles in optically thick and thin lines, we searched the clumps with infall mot
The study of infall motion helps us to understand the initial stages of star formation. In this paper, we use the IRAM 30-m telescope to make mapping observations of 24 infall sources confirmed in previous work. The lines we use to track gas infall m