Revisiting Attenuation Curves: The Case of NGC 3351*

Abstract

Multiwavelength images from the far-UV (∼0.15 μm) to the submillimeter of the central region of the galaxy NGC 3351 are analyzed to constrain its stellar populations and dust attenuation. Despite hosting a ∼1 kpc circumnuclear starburst ring, NGC 3351 deviates from the IRX-β relation, the relation between the infrared-to-UV luminosity ratio and the UV continuum slope β that other starburst galaxies follow. To understand the reason for the deviation, we leverage the high angular resolution of archival near-UV-to-near-IR Hubble Space Telescope images to divide the ring into ∼60-180 pc size regions and model each individually. We find that the UV slope of the combined intrinsic (dust-free) stellar populations in the central region is redder than what is expected for a young model population. This is due to the region's complex star formation history, which boosts the near-UV emission relative to the far-UV. The resulting net attenuation curve has a UV slope that lies between those of the starburst attenuation curve (Calzetti et al. 2000) and the Small Magellanic Cloud extinction curve; the total-to-selective attenuation value, ¢ R (V ) = 4.93, is larger than both. As found for other star-forming galaxies, the stellar continuum of NGC 3351 is less attenuated than the ionized gas, with E(B − V ) star = 0.40 E(B − V ) gas . The combination of the "red" intrinsic stellar population and the new attenuation curve fully accounts for the location of the central region of NGC 3351 on the IRX-β diagram. Thus, the observed characteristics result from the complex mixture of stellar populations and dust column densities in the circumnuclear region. Despite being a sample of one, these findings highlight the difficulty of defining attenuation curves of general applicability outside the regime of centrally concentrated starbursts.

The average dust attenuation curve at z ∼ 1.3 based on HST grism surveys

“…We also highlight the correlation value found in Battisti et al (2016) between the UV slope, β phot and τ l B based on a sample of ∼10,000 galaxies in SDSS that were matched to UV data from GALEX, which is weaker than those relative to log((Hα+[NII])/[OIII]), log M⋆, and 12+log(O/H). The poor correlation between τ l B and the UV slope is most likely linked to the fact that the intrinsic UV slope of galaxies vary with SFH (e.g., Calzetti et al 2021) and that this relation also depends on the differential reddening factor between the ionised gas and stellar components (E(B − V )star/E(B − V )gas; see Salim & Narayanan 2020, for discussion). The log ((Hα+[NII])/[OIII]), log M⋆, and 12+log(O/H) correlations are shown in Figure 8.…”

The SCUBA-2 Cosmology Legacy Survey: the EGS deep field – III. The evolution of faint submillimetre galaxies atz< 4

“…Some of our SMGs are indeed located above the IRX-𝛽 relation (Zavala et al 2018). This effect could be due to various factors, including differing star-formation histories (Salmon et al 2016;Calzetti et al 2021). Elbaz et al (2018) observed a sample of massive starburst galaxies selected in Herschel bands and a complementary sample of 1.3 mmselected galaxies.…”

Extinction in the Large Magellanic Cloud Bar around NGC1854, NGC1856, and NGC1858

“…Also the extinction properties (and extinction law) are directly measured by us in our fields, including the value of R V . Other studies instead assume an average value of R V , which is known to be affected by large uncertanties (Calzetti et al 2000) and is not applicable outside the regime of centrally-concentrated starburst galaxies (Calzetti et al 2021). Furthermore, the fact that the empirical relationships that we discovered from a limited number of small star-forming regions is able to reproduce, to within a factor of two, also to the case of 30 Dor suggests that these relationships are meaningful also for the intense star-forming knots of high-redshift galaxies that 30 Dor mimics (e.g., Doran et al 2013;Crowther et al 2017).…”