The Global Star Formation Law: from Dense Cores to Extreme Starbursts

Active star formation (SF) is tightly related to the dense molecular gas in the giant molecular clouds' dense cores. Our HCN (measure of the dense molecular gas) survey in 65 galaxies (including 10 ultraluminous galaxies) reveals a tight linear correlation between HCN and IR (SF rate) luminosities, whereas the correlation between IR and CO (measure of the total molecular gas) luminosities is nonlinear. This suggests that the global SF rate depends more intimately upon the amount of dense molecular gas than the total molecular gas content. This linear relationship extends to both the dense cores in the Galaxy and the hyperluminous extreme starbursts at high-redshift. Therefore, the global SF law in dense gas appears to be linear all the way from dense cores to extreme starbursts, spanning over nine orders of magnitude in IR luminosity.Comment: 5 pages including (questions/answers) discussion. Talk contribution at IAU Symp. 237, B.G. Elmegreen & J. Palous, ed

Z-pole test of effective dark matter diboson interactions at the CEPC

In this paper we investigate the projected sensitivity to effective dark matter (DM) - diboson interaction during the high luminosity $Z$-pole and 240 GeV runs at the proposed Circular Electron Positron Collider (CEPC). The proposed runs at the 91.2 GeV $e^+e^-$ center of mass energy offers an interesting opportunity to probe effective dark matter couplings to the $Z$ boson, which can be less stringently tested in non-collider searches. We investigate the prospective sensitivity for dimension 6 and dimension 7 effective diboson operators to scalar and fermion dark matter. These diboson operators can generate semi-visible $Z$ boson decay, and high missing transverse momentum mono-photon signals that can be test efficiently at the CEPC, with a small and controllable Standard Model $\gamma\bar{\nu}\nu$ background. A projected sensitivity for effective $\gamma Z$ coupling efficient $\kappa_{\gamma Z}< (1030$ GeV$)^{-3}$, $(1970$ GeV$)^{-3}$ for scalar DM, $\kappa_{\gamma Z}< (360$ GeV$)^{-3}$, $(540$ GeV$)^{-3}$ for fermion DM are obtain for 25 fb$^{-1}$ and 2.5 ab$^{-1}$ $Z$-pole luminosities assuming the optimal low dark matter mass range. In comparison the effective DM-diphoton coupling sensitivity $\kappa_{\gamma \gamma}< (590$ GeV$)^{-3}$ for scalar DM, $\kappa_{\gamma \gamma}< (360$ GeV$)^{-3}$ for fermion DM are also obtained for a 5 ab$^{-1}$ 240 GeV Higgs run. We also compare the CEPC sensitivities to current direct and indirect search limits on these effective DM-diboson operators.Comment: 10 pages, 7 figures. Dimension-6 diboson operators include