Dust Absorption and the Ultraviolet Luminosity Density atz ≈ 3 as Calibrated by Local Starburst Galaxies

Abstract

We refine a technique to measure the absorption corrected ultraviolet (UV) luminosity of starburst galaxies using rest frame UV quantities alone, and apply it to Lyman-limit U -dropouts at z ≈ 3 found in the Hubble Deep field (HDF). The method is based on an observed correlation between the ratio of far infrared (FIR) to UV fluxes with spectral slope β (a UV color). A simple fit to this relation allows the UV flux absorbed by dust and reprocessed to the FIR to be calculated, and hence the dust-free UV luminosity to be determined. International Ultraviolet Explorer spectra and InfraRed Astronomical Satellite fluxes of local starbursts are used to calibrate the F FIR /F 1600 versus β relation in terms of A 1600 (the dust absorption at 1600Å), and the transformation from broad band photometric color to β. Both calibrations are almost completely independent of theoretical stellar population models. We show that the recent marginal and non-detections of HDF U -dropouts at radio and sub-mm wavelengths are consistent with their assumed starburst nature, and our calculated A 1600 . This is also true of recent observations of the ratio of optical emission line flux to UV flux density in the brightest U -dropouts. This latter ratio turns out not to be a good indicator of dust extinction. In U -dropouts, absolute magnitude M 1600,0 correlates with β: brighter galaxies are redder, as is observed to be the case for local starburst galaxies. This suggests that a mass-metallicity relationship is already in place at z ≈ 3. The absorption-corrected UV luminosity function of U -dropouts extends up to M 1600,0 ≈ −24 ABmag corresponding to a star formation rate ∼ 200 M ⊙ yr −1 (H 0 = 50 km s −1 Mpc −1 , q 0 = 0.5 assumed throughout). The absorption-corrected UV luminosity density at z ≈ 3 is ρ 1600,0 ≥ 1.4 × 10 27 erg s −1 Hz −1 Mpc −3 . It is still a lower limit since completeness corrections have not been done and because only galaxies with A 1600 ∼ < 3.6 mag are blue enough in the UV to be selected as U -dropouts. The luminosity weighted mean dust absorption factor of our sample is 5.4 ± 0.9 at 1600Å.

Dusty star-forming galaxies at high redshift

“…With a UV spectral index of β = −1.5 ± 0.8, we can surmise that the expected L IR /L UV ratio for SMGs would be around ∼10 if a dust attenuation relation with β from Meurer et al (1999) is assumed, but again, factors of ∼100 are more typical for SMGs. Reddy et al (2012) recently studied the direct dust luminosity of UV-selected galaxies, comparing the UV spectral slope directly to stacked Herschel flux densities in GOODS-Herschel and found that the attenuation and reddening of the slope agree with previous results calibrated from local starburst galaxies.…”

A dusty, normal galaxy in the epoch of reionization

“…The constraints induced by the observed correlation between the UV spectral slope, β UV , and the ratio of observed infrared to UV luminosity, IRX 39 , with the flux uncertainties and β UV slope uncertainties included, are also shown in Extended Data Fig. 5.…”

Dust Properties of C ii Detected z ∼ 5.5 Galaxies: New HST/WFC3 Near-IR Observations

“…11 It is therefore a valid tool to study the ISM column density of galaxies (Meurer et al 1999;Kong et al 2004;Casey et al 2014). Furthermore, β is the only estimate of the dust content available for the vast majority of galaxies at z>3 due to the relative insensitivity of contemporary optical and IR surveys.…”