The nebular properties of star-forming galaxies at intermediate redshift from the Large Early Galaxy Astrophysics Census

Abstract

We present a detailed study of the partial rest-optical (${\lambda }_{\mathrm{obs}}\approx 3600-5600$Å) spectra of $N=328$ star-forming galaxies at $0.6<z<1.0$ from the Large Early Galaxy Astrophysics Census (LEGA-C). We compare this sample with low-redshift ($z\sim 0$) galaxies from the Sloan Digital Sky Survey (SDSS), intermediate-redshift ($z\sim 1.6$) galaxies from the Fiber Multi-Object Spectrograph (FMOS)-COSMOS Survey, and high-redshift ($z\sim 2$) galaxies from the Keck Baryonic Structure Survey (KBSS). At a lookback time of $6-8\mathrm{Gyr}$, galaxies with stellar masses $\log ({\mathrm{M}}_{\ast }/{\mathrm{M}}_{\odot })>10.25$ appear remarkably similar to $z\sim 0$ galaxies in terms of their nebular excitation, as measured using $[\mathrm{O}\mathrm{III}]\lambda 5008/\mathrm{H}\beta$. There is some evidence that $0.6<z<1.0$ galaxies with lower ${\mathrm{M}}_{\ast }$ have higher $[\mathrm{O}\mathrm{III}]\lambda 5008/\mathrm{H}\beta$ than $z\sim 0$ galaxies and are more similar to less evolved $z\sim 1.6$ and $z\sim 2$ galaxies, which are offset from the $z\sim 0$ locus at all ${\mathrm{M}}_{\ast }$. We explore the impact selection effects, contributions from active galactic nuclei, and variations in physical conditions (ionization parameter and gas-phase oxygen abundance) have on the apparent distribution of $[\mathrm{O}\mathrm{III}]\lambda 5008/\mathrm{H}\beta$ and find somewhat higher ionization and lower enrichment in $0.6<z<1.0$ galaxies with lower ${\mathrm{M}}_{\ast }$ relative to $z\sim 0$ galaxies. We use new near-infrared spectroscopic observations of $N=53$ LEGA-C galaxies to investigate other probes of enrichment and excitation. Our analysis demonstrates the importance of obtaining complete rest-optical spectra of galaxies in order to disentangle these effects.

Accepted by ApJ; main text 20 pages, 12 figures and 5 tables

References in corpus (21)

• Array Programming with NumPy
• The NumPy array: a structure for efficient numerical computation
• Cosmic Star Formation History
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Strong Nebular Line Ratios in the Spectra of z~2-3 Star-forming Galaxies: First Results from KBSS-MOSFIRE
• Understanding Galaxy Evolution through Emission Lines
• Nebular Emission Line Ratios in z~2-3 Star-Forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio
• The MOSDEF Survey: Excitation Properties of $z\sim 2.3$ Star-forming Galaxies
• AGN Emission Line Diagnostics and the Mass-Metallicity Relation up to Redshift z~2: the Impact of Selection Effects and Evolution
• Metallicities and Physical Conditions in Star-forming Galaxies at z~1.0-1.5
• The Constant Average Relationship between Dust-obscured Star Formation and Stellar Mass from $z=0$ to $z=2.5$
• The MOSDEF Survey: Optical AGN Diagnostics at z~2.3
• The Chandra COSMOS-Legacy survey: Source X-ray spectral properties
• The Detection of a Red Sequence of Massive Field Galaxies at z~2.3 and its Evolution to z~0
• The FMOS-COSMOS survey of star-forming galaxies at $z\sim 1.6$ VI: Redshift and emission-line catalog and basic properties of star-forming galaxies
• Physical properties of galaxies and their evolution in the VIMOS VLT Deep Survey. I. The evolution of the mass-metallicity relation up to z~0.9
• Chemical abundance scaling relations for multiple elements in z~2-3 star-forming galaxies
• Metal-poor, Strongly Star-Forming Galaxies in the DEEP2 Survey: The Relationship between Stellar Mass, Temperature-based Metallicity, and Star Formation Rate
• The MOSDEF Survey: The Mass-Metallicity relationship and the existence of the FMR at z~1.5
• Reconciling the Results of the z~2 MOSDEF and KBSS-MOSFIRE Surveys
• Disentangling the physical origin of emission line ratio offsets at high redshift with spatially resolved spectroscopy