SPITZERANDHERSCHELMULTIWAVELENGTH CHARACTERIZATION OF THE DUST CONTENT OF EVOLVED H II REGIONS

Abstract

We have analyzed a uniform sample of 16 evolved H II regions located in a 2 • ×2 • Galactic field centered at (l,b) = (30 • , 0 • ) and observed as part of the Herschel Hi-GAL survey. The evolutionary stage of these H II regions was established using ancillary radio continuum data. By combining Hi-GAL PACS (70 µm, 160 µm) and SPIRE (250 µm, 350 µm and 500 µm) measurements with MIPSGAL 24 µm data, we built Spectral Energy Distributions (SEDs) of the sources and showed that a 2-component grey-body model is a good representation of the data. In particular, wavelengths > 70 µm appear to trace a cold dust component, for which we estimated an equilibrium temperature of the Big Grains (BGs) in the range 20 -30 K, while for λ < 70 µm, the data indicated the presence of a warm dust component at temperatures of the order of 50 -90 K. This analysis also revealed that dust is present in the interior of H II regions, although likely not in a large amount. In addition, the data appear to corroborate the hypothesis that the main mechanism responsible for the (partial) depletion of dust in H II regions is radiation-pressure-driven drift. In this framework, we speculated that the 24 µm emission which spatially correlates with ionized gas might be associated with either Very Small Grain (VSG) or BG replenishment, as recently proposed for the case of Wind-Blown Bubbles (WBB). Finally, we found that evolved H II regions are characterized by distinctive far-IR and sub-mm colors, which can be used as diagnostics for their identification in unresolved Galactic and extragalactic regions.

A Herschel/PACS Far-infrared Line Emission Survey of Local Luminous Infrared Galaxies

“…33 As we argued in Díaz-Santos et al (2013), the C II 158 [ ] deficit is likely caused by an increase of the amount of dust heated to high temperatures in the ionized region-close to the PDR front-of dust-bounded star-forming regions (see, e.g., Abel et al 2009;Paladini et al 2012), where the density of material is expected to increase significantly (Draine 2011). Furthermore, the deficit seems to be restricted to the nuclear region of galaxies, where the starburst is ongoing (Díaz-Santos et al 2014;Smith et al 2017).…”

Modeling and predicting the shape of the far-infrared to submillimeter emission in ultra-compact HII regions and cold clumps

“…Here, we did not perform any χ 2 minimization. For G29.1-0.0 and G29.2-0.0, we used temperature values of 29.5 K and 26.4 K, which is close to the value of the cold component (29.5 K and 25.6 K) derived by Paladini et al (2012) when using a two-component model with fixed dust emissivity index to minimize SEDs between 24 and 500 μm. In these two regions the 70 μm emission is largely dominated by emission from the cold component.…”

Hi-GAL, theHerschelinfrared Galactic Plane Survey: photometric maps and compact source catalogues

“…Bernard et al 2010;Paradis et al 2010;Compiègne et al 2010;Traficante et al 2014;Elia et al 2014) to dense, large-scale filaments (Molinari et al 2010a;Schisano et al 2014;Wang et al 2015), dust in HII regions (e.g. Paladini et al 2012;Tibbs et al 2012), clumps and massive star formation (e.g. Elia et al 2010Elia et al , 2013Bally et al 2010;Battersby et al 2011;Mottram & Brunt 2012;Wilcock et al 2012;Veneziani et al 2013;Beltrán et al 2013;Strafella et al 2015;Traficante et al 2015), Galactic central molecular zone studies (Molinari et al 2011a;Longmore et al 2012), triggered star formation (Zavagno et al 2010), and finally dust around post-main-sequence objects MartinavarroArmengol et al, in prep.).…”