Let p be a prime and F(p) the maximal p-extension of a field F containing a
primitive p-th root of unity. We give a new characterization of Demuskin groups
among Galois groups Gal(F(p)/F) when p=2, and, assuming the Elementary Type
Conjecture, when p>2 as well. This characterization is in terms of the
structure, as Galois modules, of the Galois cohomology of index p subgroups of
Gal(F(p)/F).Comment: v2 (20 pages); added theorem characterizing decompositions into free
and trivial modules; to appear in J. Algebr
Let \L be a non-noetherian Krull domain which is the inverse limit of
noetherian Krull domains \L_d and let M be a finitely generated \L-module
which is the inverse limit of \L_d-modules Md. Under certain hypotheses
on the rings \L_d and on the modules Md, we define a pro-characteristic
ideal for M in \L, which should play the role of the usual characteristic
ideals for finitely generated modules over noetherian Krull domains. We apply
this to the study of Iwasawa modules (in particular of class groups) in a
non-noetherian Iwasawa algebra \Z_p[[\Gal(\calf/F)]], where F is a function
field of characteristic p and \Gal(\calf/F)\simeq\Z_p^\infty.Comment: 15 pages, substantial chenges in exposition, new section 2.
Context. Despite their profound effect on the universe, the formation of massive stars and stellar clusters remains elusive. Recent advances in observing facilities and computing power have brought us closer to understanding this formation process. In the past decade, compelling evidence has emerged that suggests infrared dark clouds (IRDCs) may be precursors to stellar clusters. However, the usual method for identifying IRDCs is biased by the requirement that they are seen in absorption against background mid-IR emission, whereas dust continuum observations allow cold, dense pre-stellar-clusters to be identified anywhere. Aims: We aim to understand what dust temperatures and column densities characterize and distinguish IRDCs, to explore the population of dust continuum sources that are not IRDCs, and to roughly characterize the level of star formation activity in these dust continuum sources. Methods: We use Hi-GAL 70 to 500 mdatatoidentifydustcontinuumsourcesintheell=30degandell=59degHi−GALsciencedemonstrationphase(SDP)fields,tocharacterizeandsubtracttheGalacticcirrusemission,andperformpixel−by−pixelmodifiedblackbodyfitsoncirrus−subtractedHi−GALsources.WeutilizearchivalSpitzerdatatoindicatethelevelofstar−formingactivityineachpixel,frommid−IR−darktomid−IR−bright.Results:WepresenttemperatureandcolumndensitymapsintheHi−GALell=30degandell=59degSDPfields,aswellasarobustalgorithmforcirrussubtractionandsourceidentificationusingHi−GALdata.WereportonthefractionofHi−GALsourcepixelswhicharemid−IR−dark,mid−IR−neutral,ormid−IR−brightinbothfields.Wefindsignificanttrendsincolumndensityandtemperaturebetweenmid−IR−darkandmid−IR−brightpixels;mid−IR−darkpixelsareabout10Kcolderandhaveafactorof2highercolumndensityonaveragethanmid−IR−brightpixels.WefindthatHi−GALdustcontinuumsourcesspanarangeofevolutionarystatesfrompre−tostar−forming,andthatwarmersourcesareassociatedwithmorestarformationtracers.Additionally,thereisatrendofincreasingtemperaturewithtracertypefrommid−IR−darkatthecoldest,tooutflow/masersourcesinthemiddle,andfinallyto8and24m bright sources at the warmest. Finally, we identify five candidate IRDC-like sources on the far-side of the Galaxy. These are cold (20 K), high column density (N(H2) gt 1022 cm−2) clouds identified with Hi-GAL which, despite bright surrounding mid-IR emission, show little to no absorption at 8 $m. These are the first inner Galaxy far-side candidate IRDCs of which the authors are aware. Herschel in an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation by NASA.The FITS files discussed in the paper would be released publicly WITH the Hi-GAL data (on the Hi-GAL website) when the Hi-GAL data is released publicly.Peer reviewe