Linking dust emission to fundamental properties in galaxies: the low-metallicity picture

Abstract

Aims. In this work, we aim to provide a consistent analysis of the dust properties from metal-poor to metal-rich environments by linking them to fundamental galactic parameters. Methods. We consider two samples of galaxies: the Dwarf Galaxy Survey (DGS) and the Key Insights on Nearby Galaxies: a FarInfrared Survey with Herschel (KINGFISH), totalling 109 galaxies, spanning almost 2 dex in metallicity. We collect infrared (IR) to submillimetre (submm) data for both samples and present the complete data set for the DGS sample. We model the observed spectral energy distributions (SED) with a physically-motivated dust model to access the dust properties: dust mass, total-IR luminosity, polycyclic aromatic hydrocarbon (PAH) mass fraction, dust temperature distribution, and dust-to-stellar mass ratio. Results. Using a different SED model (modified black body), different dust composition (amorphous carbon in lieu of graphite), or a different wavelength coverage at submm wavelengths results in differences in the dust mass estimate of a factor two to three, showing that this parameter is subject to non-negligible systematic modelling uncertainties. We find half as much dust with the amorphous carbon dust composition. For eight galaxies in our sample, we find a rather small excess at 500 µm (≤1.5σ). We find that the dust SED of low-metallicity galaxies is broader and peaks at shorter wavelengths compared to more metal-rich systems, a sign of a clumpier medium in dwarf galaxies. The PAH mass fraction and dust temperature distribution are found to be driven mostly by the specific star formation rate, sSFR, with secondary effects from metallicity. The correlations between metallicity and dust mass or total-IR luminosity are direct consequences of the stellar mass-metallicity relation. The dust-to-stellar mass ratios of metal-rich sources follow the well-studied trend of decreasing ratio for decreasing sSFR. The relation is more complex for low-metallicity galaxies with high sSFR, and depends on the chemical evolutionary stage of the source (i.e. gas-to-dust mass ratio). Dust growth processes in the ISM play a key role in the dust mass build-up with respect to the stellar content at high sSFR and low metallicity. Conclusions. We conclude that the evolution of the dust properties from metal-poor to metal-rich galaxies derives from a complex interplay between star formation activity, stellar mass, and metallicity.

Can Dust Injected by SNe Explain the NIR–MIR Excess in Young Massive Stellar Clusters?

“…In fact, Relaño et al (2016) and Reines et al (2008) required an additional ∼ 1000-K blackbody component of "uncertain origin" to fit their observed IR SEDs. Similar excesses, more prevalent in the MIR, have also been observed in a number of blue compact dwarf galaxies (e.g: I Zw 18, II Zw 40, Mrk 930 and Haro 11 (Rémy-Ruyer et al 2015;Vanzi et al 2000;Izotov et al 2014)). Therefore, these observations not only point to the existence of a very hot dust component (∼400-1000 K), but also give compelling evidence for the presence of a persistent (i.e.…”

Molecular gas in low-metallicity starburst galaxies:

“…Especially in compact low-metallicity galaxies, this approach is, however, not free of large uncertainties, which are mostly driven by variations in the D/G ratio with the ISM density (Schruba et al 2012), uncertainties in its calibration at different metallicities, and variations with the SF history of each galaxy (Cormier et al 2014;Rémy-Ruyer et al 2014; see also Bolatto et al 2013). In our case, only ∼20% of the BCD sample have Herschel observations reported so far (see Rémy-Ruyer et al 2015), thus precluding a complete analysis based on the dust masses.…”

“…We used the dust masses compiled by Rémy-Ruyer et al (2014 to derive the H 2 masses following Cormier et al (2014) and assuming the metallicity dependent D/G ratio of Rémy-Ruyer et al (2015). The resulting dust-based M H 2 and α CO,dust are a factor of ∼1.5-30 higher than those derived using the Galactic α CO,MW .…”

The cosmic dust rate across the Universe

“…In the plots we are going to present we will refer to the metallicity of the gas expressed as log(O/H) + 12, as explained in Rémy-Ruyer et al (2014), in both data and models. The dust masses provided by Rémy-Ruyer et al (2015) are constrained on the basis of the spectral energy distribution of each galaxy. They provide two different values for the dust mass depending on the assumed dust species forming the carbonaceous grains: when carbon dust is assumed in form of amorphous carbonaceous grains, the dust mass is about 2.5 times lower than the one obtained by a graphitegrain model.…”