Dust extinction from balmer decrements of star-forming galaxies at 0.75 ≤ z ≤ 1.5 with hubble space telescope/wide-field-camera 3 spectroscopy from the wfc3 infrared spectroscopic parallel survey
Astrophysical Journal 763:2 (2013)
Abstract:
Spectroscopic observations of Hα and Hβ emission lines of 128 star-forming galaxies in the redshift range 0.75 ≤ z ≤ 1.5 are presented. These data were taken with slitless spectroscopy using the G102 and G141 grisms of the Wide-Field-Camera 3 (WFC3) on board the Hubble Space Telescope as part of the WFC3 Infrared Spectroscopic Parallel survey. Interstellar dust extinction is measured from stacked spectra that cover the Balmer decrement (Hα/Hβ). We present dust extinction as a function of Hα luminosity (down to 3 × 1041 erg s-1), galaxy stellar mass (reaching 4 × 108 M, and rest-frame Hα equivalent width. The faintest galaxies are two times fainter in Hα luminosity than galaxies previously studied at z ∼ 1.5. An evolution is observed where galaxies of the same Hα luminosity have lower extinction at higher redshifts, whereas no evolution is found within our error bars with stellar mass. The lower Hα luminosity galaxies in our sample are found to be consistent with no dust extinction. We find an anti-correlation of the [O III] λ5007/Hα flux ratio as a function of luminosity where galaxies with L Hα < 5 × 1041 erg s-1 are brighter in [O III] λ5007 than Hα. This trend is evident even after extinction correction, suggesting that the increased [O III] λ5007/Hα ratio in low-luminosity galaxies is likely due to lower metallicity and/or higher ionization parameters. © 2013. The American Astronomical Society. All rights reserved..Theoretical predictions for the effect of nebular emission on the broad-band photometry of high-redshift galaxies
Monthly Notices of the Royal Astronomical Society 435:4 (2013) 2885-2895
Abstract:
By combining optical and near-IR observations from the Hubble Space Telescope with near-IR photometry from the Spitzer Space Telescope, it is possible to measure the rest-frame UV- optical colours of galaxies at z = 4-8. The UV-optical spectral energy distribution of star formation dominated galaxies is the result of several different factors. These include the joint distribution of stellar masses, ages and metallicities (solely responsible for the pure stellar spectral energy distribution), and the subsequent reprocessing by dust and gas in the interstellar medium. Using a large cosmological hydrodynamical simulation (MassiveBlack-II), we investigate the predicted spectral energy distributions of galaxies at high redshift with a particular emphasis on assessing the potential contribution of nebular emission. We find that the average (median) pure stellar UV-optical colour correlates with both luminosity and redshift such that galaxies at lower redshift and higher luminosity are typically redder. Assuming that the escape fraction of ionizing photons is close to zero, the effect of nebular emission is to redden theUV-optical 1500-Vω colour by, on average, 0.4mag at z=8 declining to 0.25 mag at z = 4. Young and low-metallicity stellar populations, which typically have bluer pure stellar UV-optical colours, produce larger ionizing luminosities and are thus more strongly affected by the reddening effects of nebular emission. This causes the distribution of 1500-Vω colours to narrow and the trends with luminosity and redshift to weaken. The strong effect of nebular emission leaves observed-frame colours critically sensitive to the redshift of the source. For example, increasing the redshift by 0.1 can result in observed-frame colours changing by up to ̃0.6. These predictions reinforce the need to include nebular emission when modelling the spectral energy distributions of galaxies at high redshift and also highlight the difficultly in interpreting the observed colours of individual galaxies without precise redshift information. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.Interpreting the observed UV continuum slopes of high-redshift galaxies
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 430:4 (2013) 2885-2890
VLT/XSHOOTER and Subaru/MOIRCS spectroscopy of HUDF.YD3: no evidence for Lyman α emission at z=8.55
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 430:4 (2013) 3314-3319
No Evidence for Lyman-alpha Emission in Spectroscopy of z \gt 7 Candidate Galaxies
Monthly Notices of the Royal Astronomical Society Wiley 427:4 (2012) 3055-3070