Probing star formation and ISM properties using galaxy disk inclination

Abstract

Disk galaxies at intermediate redshift (z ∼ 0.7) have been found in previous work to display more optically thick behaviour than their local counterparts in the rest-frame B-band surface brightness, suggesting an evolution in dust properties over the past ∼6 Gyr. We compare the measured luminosities of face-on and edge-on star-forming galaxies at different wavelengths (Ultraviolet (UV), midinfrared (MIR), far-infrared (FIR), and radio) for two well-matched samples of disk-dominated galaxies: a local Sloan Digital Sky Survey (SDSS)-selected sample at z ∼ 0.07 and a sample of disks at z ∼ 0.7 drawn from Cosmic Evolution Survey (COSMOS). We have derived correction factors to account for the inclination dependence of the parameters used for sample selection. We find that typical galaxies are transparent at MIR wavelengths at both redshifts, and that the FIR and radio emission is also transparent as expected. However, reduced sensitivity at these wavelengths limits our analysis; we cannot rule out opacity in the FIR or radio. Ultra-violet attenuation has increased between z ∼ 0 and z ∼ 0.7, with the z ∼ 0.7 sample being a factor of ∼3.4 more attenuated. The larger UV attenuation at z ∼ 0.7 can be explained by more clumpy dust around nascent star-forming regions. There is good agreement between the fitted evolution of the normalisation of the SFR UV versus 1-cos(i) trend (interpreted as the clumpiness fraction) and the molecular gas fraction/dust fraction evolution of galaxies found out to z < 1.

A universal relation of dust obscuration across cosmic time

“…Both the symbols and lines are color-coded with the gas-phase metallicity shown by the color bar. Leslie et al 2018). Some authors concluded from this that galaxy stellar mass is the most fundamental parameter determining the dust obscuration in SFGs (Garn & Best 2010;Zahid et al 2014b).…”

“…The mass-IRX relation has been widely examined over a wide redshift range (Reddy et al 2010;Heinis et al 2014;Whitaker et al 2014;Álvarez-Márquez et al 2016), finding that it evolves little out to z=3 at the low-mass end of M * <10 10.5 M in contrast to a rapid evolution at the high-mass end (Whitaker et al 2014; Leslie et al 2018). Some authors concluded from this that galaxy stellar mass is the most fundamental parameter determining the dust obscuration in SFGs (Garn & Best 2010;Zahid et al 2014b).…”

“…Dust obscuration also increases with SFR or SFR surface density (Wang & Heckman 1996;Martin et al 2005;Garn & Best 2010;Xiao et al 2012), as well as galaxy stellar mass (Garn & Best 2010;Reddy et al 2010;Price et al 2014;Whitaker et al 2014;Zahid et al 2017). In addition, the observed dust obscuration is weakly correlated with the inclination of disc SFGs due to enhanced projected dust columns (Wild et al 2011;Chevallard et al 2013;Leslie et al 2018).…”

On the Impact of Inclination-dependent Attenuation on Derived Star Formation Histories: Results from Disk Galaxies in the Great Observatories Origins Deep Survey Fields

“…Both Graham & Worley (2008) and Sargent et al (2010) independently found that the inclination effects of dust can bias measurements of the galaxy B-band surface brightness to be » -0.5 mag arcsec 2 brighter for edge-on galaxies. Measurements of the half light radius have been shown to be increased by up to 110% for edge-on galaxies compared to face-on galaxies (Möllenhoff et al 2006;Leslie et al 2018b). UV magnitudes have been shown to be 1-2 magnitudes fainter for edge-on galaxies.…”

“…Finally, we quantified the consequences of not incorporating variation in γ and assuming radial symmetry when determining inclination. We compared the median, 16th, and 84th percentiles of our sample's inclination PDFs to inclinations and uncertainties of our sample calculated using Equation (1) assuming radial symmetry and the commonly used fixed values of γ = 0.15 and 0.2 (e.g., Maller et al 2009;Sargent et al 2010;Chevallard et al 2013;Wang et al 2018;Leslie et al 2018b) as well as γ = 0.08 assumed by Tuffs et al (2004) in deriving the inclinationdependent attenuation curves. These calculated values for the fixed values of γ are in excellent agreement with the median PDF inclinations for galaxies with i  30°.…”