CLASSY V: The impact of aperture effects on the inferred nebular properties of local star-forming galaxies

Abstract

Strong nebular emission lines are an important diagnostic tool for tracing the evolution of star-forming galaxies across cosmic time. However, different observational setups can affect these lines, and the derivation of the physical nebular properties. We analyze 12 local star-forming galaxies from the COS Legacy Spectroscopy SurveY (CLASSY) to assess the impact of using different aperture combinations on the determination of the physical conditions and gas-phase metallicity. We compare optical spectra observed with the SDSS aperture, which has a 3" of diameter similar to COS, to IFU and longslit spectra, including new LBT/MODS observations of five CLASSY galaxies. We calculate the reddening, electron densities and temperatures, metallicities, star formation rates, and equivalent widths (EWs). We find that measurements of the electron densities and temperatures, and metallicity remained roughly constant with aperture size, indicating that the gas conditions are relatively uniform for this sample. However, using the IFU observations of 3 galaxies, we find that the E(B-V) values derived from the Balmer ratios decrease ( by up to 53%) with increasing aperture size. The values change most significantly in the center of the galaxies, and level out near the COS aperture diameter of 2.5". We examine the relative contributions from the gas and stars using the H$\alpha$ and [OIII] $\lambda$5007 EWs as a function of aperture light fraction, but find little to no variations within a given galaxy. These results imply that the optical spectra provide nebular properties appropriate for the FUV CLASSY spectra, even when narrow 1.0" long-slit observations are used.

arXiv commentAccepted for publication in ApJ

References in corpus (49)

• Stellar population synthesis at the resolution of 2003
• Galactic Stellar and Substellar Initial Mass Function
• The physical properties of star forming galaxies in the low redshift universe
• Star Formation in the Milky Way and Nearby Galaxies
• SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
• Galaxy Star-Formation as a Function of Environment in the Early Data Release of the Sloan Digital Sky Survey
• PyNeb: a new tool for analyzing emission lines. I. Code description and validation of results
• The chemical composition of metal-poor emission-line galaxies in the Data Release 3 of the Sloan Digital Sky Survey
• Heavy element abundances in blue compact galaxies
• A Three-Dimensional Map of Milky-Way Dust
• Star formation rate indicators in the Sloan Digital Sky Survey
• The most metal-poor galaxies
• Direct Oxygen Abundances for Low Luminosity LVL Galaxies
• On Measuring Chemical Abundances in Distant Galaxies Using Global Emission Line Spectra
• An Integrated Spectrophotometric Survey of Nearby Star-Forming Galaxies
• New fully empirical calibrations of strong-line metallicity indicators in star forming galaxies
• Aperture effects on Star Formation Rate, Metallicity and Reddening
• Ultraviolet spectra of extreme nearby star-forming regions --- approaching a local reference sample for JWST
• CHAOS I: Direct Chemical Abundances for HII Regions in NGC 628
• Carbon and Oxygen Abundances in Low Metallicity Dwarf Galaxies
• Biases in abundance derivations for metal-rich nebulae
• The Chemical Evolution of Carbon, Nitrogen, and Oxygen in Metal-Poor Dwarf Galaxies
• CHAOS IV: Gas-Phase Abundance Trends From The First Four CHAOS Galaxies
• CHAOS III: Gas-Phase Abundances in NGC5457
• Electron impact excitation of OII fine-structure levels
• The Connection Between Reddening, Gas Covering Fraction, and the Escape of Ionizing Radiation at High Redshift
• The MOSDEF Survey: the Variation of the Dust Attenuation Curve with Metallicity
• The Balmer decrement of SDSS galaxies
• The COS Legacy Archive Spectroscopy SurveY (CLASSY) Treasury Atlas
• The effect of dust geometry on the Lyman-alpha output of galaxies
• Characterizing Extreme Emission Line Galaxies I: A Four-Zone Ionization Model for Very-High-Ionization Emission
• Improving Helium Abundance Determinations with Leo P as a Case Study
• The Galactic radial abundance gradients of C, N, O, Ne, S, Cl and Ar from deep spectra of H II regions
• Neon and Argon optical emission lines in ionized gaseous nebulae: Implications and applications
• Spatial analysis of the Halpha emission in the local star-forming UCM galaxies
• New Radial Abundance Gradients for NGC 628 and NGC 2403
• SDSS IV MaNGA -- Metallicity and ionisation parameter in local star-forming galaxies from Bayesian fitting to photoionisation models
• Extremely metal-poor galaxies with HST/COS: laboratories for models of low-metallicity massive stars and high-redshift galaxies
• CHAOS VI: Direct Abundances in NGC 2403
• Search for Extremely Metal-poor Galaxies in the Sloan Digital Sky Survey (II): high electron temperature objects
• The H alpha Luminosity Function of Morphologically Classified Galaxies in the Sloan Digital Sky Survey
• Spectral Classification of Galaxies Along the Hubble Sequence
• Searching for metal-deficient emission-line galaxy candidates: the final sample of the SDSS DR12 galaxies
• The Leoncino Dwarf Galaxy: Exploring the Low-Metallicity End of the Luminosity-Metallicity and Mass-Metallcity Relations
• The Te[N II]-Te[O III] temperature relation in H II regions and the reliability of strong-line methods
• Bar effect on gas-phase abundance gradients. I. Data sample and chemical abundances
• Blue diffuse dwarf galaxies: a clearer picture
• The diffuse ionized gas (DIG) in star-forming galaxies: the influence of aperture effects on local HII regions
• Photoionized Herbig-Haro objects in the Orion Nebula through deep high-spectral resolution spectroscopy I: HH529II and III

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