ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Telescope B-Wavelength I-Wavelength O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Software O B-TextGarbage I-TextGarbage B-URL O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O O B-Telescope B-Wavelength I-Wavelength O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Tag O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Telescope O O O O O O O O O O O O O O O O O O O O O O B-Telescope O O O O O O O O O O O O O O O
tokens: might be candidates of prestellar cores or simply overdensities of molecular gas flows. 4.2. Gas Temperatures in Dense Cores We estimated gas temperatures in dense cores using the VLA (1, 1) and (2, 2) lines. The temperatures were then used to calculate core masses below. Line widths, column densities, and optical depths were derived at the same time. We extracted the mean (1, 1) and (2, 2) spectra within the FWHM of the 2D Gaussian fit of each core and fit them with a customized code pyAmor . 9 9 https://github.com/xinglunju/pyAmor We assumed local thermodynamic equilibrium (LTE) conditions and the same filling factor for all hyperfine components. The free parameters in the fit are the core velocity , the rotational temperature , the column density N (), the velocity dispersion , and the filling factor. The core velocity was first selected by eye and then varied within ±0.62 (one channel) of the selected value. Model spectra were constructed with these parameters. The nonlinear least-squares minimization of the difference between the model spectra and the observed spectrum was implemented with the lmfit package (Newville et al. 2014 ), and then the parameters of the best-fit model spectrum were taken to be the best-fit results. The optical depth at the line center of the main hyperfine component of (1, 1), , was derived afterward using the best-fit , N (), and . An example of the fitting is shown in Figure 6 . Figure 6. Fitting results of gas temperatures in I18308-c1 using the VLA (1, 1) and (2, 2) lines. The red curve shows the best-fit model, with the best-fit parameters displayed in the panel. Toward several dense cores, multiple velocity components in lines were found. Then we fit two independent models, each of which was constructed with the parameters listed in the previous paragraph. Two sets of best-fit parameters were derived, from which we chose the one that has similar to dense gas tracers in cores (e.g., H 2 CO, CH 3 OH) to calculate dense core properties. 4.3. Masses, Densities, NH<sub>3</sub> Abundances, Virial States The masses of the dense cores were derived using the following equation:where is the gas-to-dust mass ratio, S ν is the dust emission flux, d is the distance, is the Planck function at temperature , and is the dust opacity. We assumed and cm −2 g −1 (MRN model with thin ice mantles, after 10 5 yr of coagulation at 10 6 ; Ossenkopf Henning 1994 ). The kinematic distances were derived using the rotation curve model in Reid et al. ( 2009 ; see Lu et al. 2014 , for details). The near distance was taken in case of kinematic distance ambiguity. Under the assumption of LTE, the dust temperatures were taken to be the gas temperatures derived from , , in Section 4.2 . We did not use dust temperatures derived from Herschel data because their angular resolution is not sufficient to resolve the dense cores, nor did we use gas temperatures based on the SMA H 2 CO or CH 3 CN lines because they usually only probe the inner,