The EDGE-CALIFA Survey: Using Optical Extinction to Probe the Spatially-Resolved Distribution of Gas in Nearby Galaxies

Abstract

We present an empirical relation between the cold gas surface density (${\Sigma }_{\mathrm{gas}}$) and the optical extinction (${\mathrm{A}}_{\mathrm{V}}$) 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 ${\Sigma }_{\mathrm{gas}}$-${\mathrm{A}}_{\mathrm{V}}$ relation on global, radial, and kpc (spaxel) scales. We determine ${\mathrm{A}}_{\mathrm{V}}$ from the Balmer decrement (H$\alpha$/H$\beta$). We find that the best fit for this relation is ${\Sigma }_{\mathrm{gas}}({\mathrm{M}}_{\odot }\mathrm{p}{\mathrm{c}}^{-2})\sim 26\times {\mathrm{A}}_{\mathrm{V}}(\mathrm{mag})$, 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 ${\Sigma }_{\mathrm{gas}}$/ ${\mathrm{A}}_{\mathrm{V}}$ ratio on radial and spaxel scales as a function of $\mathrm{EW}(\mathrm{H}\alpha )$. We find that at larger values of $\mathrm{EW}(\mathrm{H}\alpha )$ (i.e., actively star-forming regions) this ratio tend to converge to the value expected for dust-star mixed geometries ($\sim$ 30 ${\mathrm{M}}_{\odot }\mathrm{p}{\mathrm{c}}^{-2}\mathrm{ma}{\mathrm{g}}^{-1}$). On radial scales, we do not find a significant relation between the ${\Sigma }_{\mathrm{gas}}$/${\mathrm{A}}_{\mathrm{V}}$ ratio and the ionized gas metallicity. We contrast our estimates of ${\Sigma }_{\mathrm{gas}}$ using ${\mathrm{A}}_{\mathrm{V}}$ 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 ${\Sigma }_{\mathrm{gas}}$-${\Sigma }_{\ast }$ relation. These tests show that optical extinction is a reliable proxy for estimating ${\Sigma }_{\mathrm{gas}}$ in the absence of direct sub/millimeter observations of the cold gas.

12 pages, 10 figures. Submitted to MNRAS

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Cited by in corpus (16)

• Galaxies hosting an AGN: a view from the CALIFA survey
• The ALMaQUEST Survey IX: The nature of the resolved star forming main sequence
• The EDGE-CALIFA survey: The local and global relations between ${\Sigma }_{\ast }$ , ${\Sigma }_{SFR}$ and ${\Sigma }_{mol}$ that regulate star-formation
• EDGE-CALIFA survey: Self-regulation of Star formation at kpc scales
• SDSS-IV MaNGA: Variations in the N/O -- O/H relation bias metallicity gradient measurements
• SDSS-IV MANGA: A Star Formation -- Baryonic Mass Relation at Kpc Scales
• ALMaQUEST -- VII: Star Formation Scaling Relations of Green Valley Galaxies
• Stellar feedback in M83 as observed with MUSE -- I. Overview, an unprecedented view of the stellar and gas kinematics and evidence of outflowing gas
• HII regions in CALIFA survey: II. The relation between their physical properties and galaxy evolution
• Which galaxy property is the best gauge of the oxygen abundance?
• Cold gas mass measurements for the era of large optical spectroscopic surveys
• A quantitative demonstration that stellar feedback locally regulates galaxy growth
• An analytical model to kinematically identify thin discs in MaNGA galaxies
• Nebular abundance gradient in the Cartwheel galaxy using MUSE data
• Galaxy evolution on resolved scales: ageing and quenching in CALIFA
• Spatially-resolved Evolution of Galaxies