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We present an empirical relation between the cold gas surface density ($Sigma_{rm gas}$) and the optical extinction (${rm A_V}$) in a sample of 103 galaxies from the Extragalactic Database for Galaxy Evolution (EDGE) survey. This survey provides CARMA interferometric CO observations for 126 galaxies included in the Calar Alto Legacy Integral Field Area (CALIFA) survey. The matched, spatially resolved nature of these data sets allows us to derive the $Sigma_{rm gas}$-${rm A_V}$ relation on global, radial, and kpc (spaxel) scales. We determine ${rm A_V}$ from the Balmer decrement (H$alpha$/H$beta$). We find that the best fit for this relation is $Sigma_{rm gas} ({rm M_odot pc^{-2}})sim~26~times~ {rm A_V}({rm mag})$, and that it does not depend on the spatial scale used for the fit. However, the scatter in the fits increases as we probe smaller spatial scales, reflecting the complex relative spatial distributions of stars, gas, and dust. We investigate the $Sigma_{rm gas}$/ ${rm A_V}$ ratio on radial and spaxel scales as a function of ${rm EW(Halpha)}$. We find that at larger values of ${rm EW(Halpha)}$ (i.e., actively star-forming regions) this ratio tend to converge to the value expected for dust-star mixed geometries ($sim$ 30 $mathrm{M_{odot} ,pc^{-2},mag^{-1}}$). On radial scales, we do not find a significant relation between the $Sigma_{rm gas}$/${rm A_V}$ ratio and the ionized gas metallicity. We contrast our estimates of $Sigma_{rm gas}$ using ${rm A_V}$ with compilations in the literature of the gas fraction on global and radial scales as well as with well known scaling relations such as the radial star-formation law and the $Sigma_{rm gas}$-$Sigma_*$ relation. These tests show that optical extinction is a reliable proxy for estimating $Sigma_{rm gas}$ in the absence of direct sub/millimeter observations of the cold gas.
We present a comparative study of molecular and ionized gas kinematics in nearby galaxies. These results are based on observations from the EDGE survey, which measured spatially resolved $^{12}$CO(J=1-0) in 126 nearby galaxies. Every galaxy in EDGE h
We investigate the prevalence, properties, and kinematics of extraplanar diffuse ionized gas (eDIG) in a sample of 25 edge-on galaxies selected from the CALIFA survey. We measure ionized gas scale heights from ${rm Halpha}$ and find that 90% have mea
We present the results of our ALMA HCN J=3-2 and HCO+ J=3-2 line observations of a uniformly selected sample (>25) of nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.15. The emission of these dense molecular gas tracers and continuum are spa
The Calar Alto Legacy Integral Field Area (CALIFA) is an ongoing 3D spectroscopic survey of 600 nearby galaxies of all kinds. This pioneer survey is providing valuable clues on how galaxies form and evolve. Processed through spectral synthesis techni
We present results from the EDGE survey, a spatially resolved CO(1-0) follow-up to CALIFA, an optical Integral Field Unit (IFU) survey of local galaxies. By combining the data products of EDGE and CALIFA, we study the variation in molecular gas deple