Galaxy inclination and the IRX-beta relation: Effects on UV star-formation rate measurements at intermediate to high redshifts. (arXiv:1811.03671v1 [astro-ph.GA])

Galaxy inclination and the IRX-beta relation: Effects on UV star-formation rate measurements at intermediate to high redshifts. (arXiv:1811.03671v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Wang_W/0/1/0/all/0/1">Weichen Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kassin_S/0/1/0/all/0/1">Susan A. Kassin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pacifici_C/0/1/0/all/0/1">Camilla Pacifici</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barro_G/0/1/0/all/0/1">Guillermo Barro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vega_A/0/1/0/all/0/1">Alexander de la Vega</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Simons_R/0/1/0/all/0/1">Raymond C. Simons</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Faber_S/0/1/0/all/0/1">S. M. Faber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Salmon_B/0/1/0/all/0/1">Brett Salmon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ferguson_H/0/1/0/all/0/1">Henry C. Ferguson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Perez_Gonzalez_P/0/1/0/all/0/1">Pablo G. Perez-Gonzalez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Snyder_G/0/1/0/all/0/1">Gregory F. Snyder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gordon_K/0/1/0/all/0/1">Karl D. Gordon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Z/0/1/0/all/0/1">Zhu Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kodra_D/0/1/0/all/0/1">Dritan Kodra</a>

At intermediate and high redshifts, measurements of galaxy star-formation
rates are usually based on rest-frame ultraviolet (UV) data. A correction for
dust attenuation, A_UV, is needed for these measurements. This correction is
typically inferred from UV spectral slopes (beta) using an equation known as
“Meurer’s Relation.” In this paper, we study this relation at a redshift of 1.5
using images and photometric measurements in the rest-frame UV (HST) through
mid-infrared (Spitzer). It is shown that massive star-forming galaxies (above
10^10 Msun) have dust corrections that are dependent on their inclination to
the line-of-sight. Edge-on galaxies have higher A_UV and infrared excess
(IRX=L(IR)/L(UV)) than face-on galaxies at a given beta. Interestingly, dust
corrections for low-mass star-forming galaxies do not depend on inclination.
This is likely because more massive galaxies have more disk-like
shapes/kinematics, while low-mass galaxies are more prolate and have more
disturbed kinematics. To account for an inclination-dependent dust correction,
a modified Meurer’s Relation is derived: A_UV=4.43+1.99 beta – 1.73 (b/a-0.67),
where b/a is the galaxy axis ratio. This inclination-dependence of A_UV can be
explained by a two-component model of the dust distribution inside galaxies. In
such a model, the dust attenuation of edge-on galaxies has a higher
contribution from a “mixture” component (dust uniformly mixed with stars in the
diffuse interstellar medium), and a lower contribution from a “birth cloud”
component (near-spherical dust shells surrounding young stars in H II regions)
than that of face-on galaxies. The difference is caused by the larger
path-lengths through disks at higher inclinations.

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