8 research outputs found
H_2 emission arises outside photodissociation regions in ultra-luminous infrared galaxies
Ultra-luminous infrared galaxies are among the most luminous objects in the
local universe and are thought to be powered by intense star formation. It has
been shown that in these objects the rotational spectral lines of molecular
hydrogen observed at mid-infrared wavelengths are not affected by dust
obscuration, leaving unresolved the source of excitation of this emission. Here
I report an analysis of archival Spitzer Space Telescope data on ultra-luminous
infrared galaxies and demonstrate that star formation regions are buried inside
optically thick clouds of gas and dust, so that dust obscuration affects
star-formation indicators but not molecular hydrogen. I thereby establish that
the emission of H_2 is not co-spatial with the buried starburst activity and
originates outside the obscured regions. This is rather surprising in light of
the standard view that H_2 emission is directly associated with star-formation
activity. Instead, I propose that H_2 emission in these objects traces shocks
in the surrounding material, which are in turn excited by interactions with
nearby galaxies, and that powerful large-scale shocks cooling by means of H_2
emission may be much more common than previously thought. In the early
universe, a boost in H_2 emission by this process may speed up the cooling of
matter as it collapsed to form the first stars and galaxies and would make
these first structures more readily observable.Comment: Main text and supplemental information, 21 pages including 6 figures,
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Customizing the degradation and load-bearing profile of 3D polycaprolactone-tricalcium phosphate scaffolds under enzymatic and hydrolytic conditions
Journal of Biomedical Materials Research - Part B Applied Biomaterials872562-569JBMRGcomplete
Incorporation of gelatin into chemically-cross-linked polyvinyl alcohol (PVA) hydrogels for endothelial cell culture
24th European Conference on Biomaterials - Annual Conference of the European Society for Biomaterials
The degradation profile of novel, bioresorbable PCL-TCP scaffolds: An in vitro and in vivo study
Journal of Biomedical Materials Research - Part A841208-218JBMR
Evaluation of hemocompatibility and endothelialization of hybrid poly(vinyl alcohol) (PVA)/gelatin polymer films
10.1002/jbm.b.32977Journal of Biomedical Materials Research - Part B Applied Biomaterials10181549-1559JBMR
Composite scaffold of poly(vinyl alcohol) and interfacial polyelectrolyte complexation fibers for controlled biomolecule delivery
10.3389/fbioe.2015.00003Frontiers in Bioengineering and Biotechnology3FEB