Galaxy And Mass Assembly (GAMA): Improved emission lines measurements in four representative samples at 0.07 <z< 0.3

Abstract

This paper presents a new catalog of emission lines based on the GAMA II data for galaxies between 0.07 < z < 0.34. The catalog includes four subsamples containing 3000 galaxies drawn from the GAMA II survey and spanning four redshift windows. The four samples are representative of intermediate-mass galaxies down to log M * > 9.4 at z ∼ 0.1 and log M * > 10.6 at z ∼ 0.30. We have developed a dedicated code called MARVIN that automates the main steps of the data analysis, but imposes visual individual quality control of each measurement. We use this catalog to investigate how the sample selection influences the shape of the stellar massmetallicity relation. We find that commonly used selection criteria on line detections and by AGN rejection could affect the shape and dispersion of the high-mass end of the M − Z relation. For log M * > 10.6, common selection criteria reject about 65% of the emission-line galaxies. We also find that the relation does not evolve significantly from z = 0.07 to z = 0.34 in the range of stellar mass for which the samples are representative (log M * > 10.6). For lower stellar masses (log M * < 10.2) we are able to show that the observed 0.15 dex metallicity decrease in the same redshift range is a consequence of a color bias arising from selecting targets in the r-band. We highlight that this color selection bias affects all samples selected in r-band (e.g., GAMA and SDSS), even those drawn from volume-limited samples. Previously reported evolution of the M − Z relation at various redshifts may need to be revised to evaluate the effect of this selection bias.

Star-forming galaxies at low-redshift in the SHARDS survey

“…This fraction grows with decreasing stellar mass, until we reach the completeness limit (∼ 10 9 M ). This behavior is consistent with previous results (e.g., Hammer et al 1997, Rodrigues et al 2016and Sobral et al 2011. Comparing with Figure 4 in Sobral et al (2011), we find that the slope of the relation is compatible, despite the different mass range and redshift.…”

“…Their work was based on a low-resolution spectroscopic survey, dealing with more massive galaxies, but with a lower EW detection limit than us (15 Å in the OII[3727] line). More recently, Rodrigues et al (2016) found a higher fraction (∼ 45%), dealing also with massive galaxies (∼ 10 10 M ) and with a much lower EW limit (10 Å in the Hα line).…”

AI-assisted super-resolution cosmological simulations II: Halo substructures, velocities and higher order statistics

“…which contain at least 300 tracer particles in our HR (SR) test set. This value corresponds roughly to the typical host mass of emission line galaxies (ELGs, see e.g., Rodrigues et al 2016). We specify this mass threshold as a sufficiently resolved halo in our HR (SR) set.…”