F. Galliano

Variations of the Mid-IR Aromatic Features inside and among Galaxies

We present the results of a systematic study of mid-IR spectra of Galactic regions, Magellanic H II regions, and galaxies of various types (dwarf, spiral, starburst), observed by the satellites ISO and Spitzer. We study the relative variations of the 6.2, 7.7, 8.6, and 11.3 ?m features inside spatially resolved objects (such as M82, M51, 30 Doradus, M17, and the Orion Bar), as well as among 90 integrated spectra of 50 objects. Our main results are that the 6.2, 7.7, and 8.6 ?m bands are essentially tied together, while the ratios between these bands and the 11.3 ?m band vary by 1 order of magnitude. This implies that the properties of the PAHs are remarkably universal throughout our sample and that the relative variations of the band ratios are mainly controlled by the fraction of ionized PAHs. In particular, we show that we can rule out both the modification of the PAH size distribution and the mid-IR extinction as an explanation of these variations. Using a few well-studied Galactic regions (including the spectral image of the Orion Bar), we give an empirical relation between the -->I6.2/I11.3 ratio and the ionization/recombination ratio -->G0/neT1/2gas, therefore providing a useful quantitative diagnostic tool of the physical conditions in the regions where the PAH emission originates. Finally, we discuss the physical interpretation of the -->I6.2/I11.3 ratio, on galactic size scales.

ISM properties in low-metallicity environments II. The dust spectral energy distribution of NGC 1569

We present newxa0450 and 850xa0 μ m SCUBA data of the dwarf galaxyxa0NGCxa01569. We construct the mid-infrared to millimeter SED ofxa0NGCxa01569, using ISOCAM, ISOPHOT, IRAS, KAO, SCUBA and MAMBOxa0data, and model the SED in order to explore the nature of the dust in low metallicity environments. The detailed modeling is performed in a self-consistent way, synthesizing the global ISRF of the galaxy using an evolutionary synthesis model with further constraints provided by the observed MIR ionic lines and a photoionisation model. Our results show that the dust properties are different in this low metallicity galaxy compared to other more metal rich galaxies. The results indicate a paucity of PAHs probably due to the destructive effects of the ISRFxa0penetrating a clumpy environment and a size-segregation of grains where the emission is dominated by small grains of sizexa0~

SPIRE imaging of M 82: Cool dust in the wind and tidal streams

3;rm nm

PHYSICAL CONDITIONS IN THE IONIZED GAS OF 30 DORADUS

, consistent with the idea of shocks having a dramatic effect on the dust properties inxa0NGCxa01569. A significant millimetre excess is present in the dust SED which can be explained by the presence of ubiquitous very cold dust (

Mapping the interstellar medium in galaxies with Herschel/SPIRE

T = 5{-}7

A multiwavelength infrared study of NGC 891

xa0K). This dust component accounts forxa040 toxa070% of the total dust mass in the galaxy (

Herschel-SPIRE observations of the disturbed galaxy NGC4438

1.6{-}3.4 times 10^5

Radial distribution of gas and dust in spiral galaxies ? The case of M 99 (NGC 4254) and M 100 (NGC 4321)

xa0

The elusive ISM of dwarf galaxies: excess submillimetre emission & CO-dark molecular gas

M_odot

The central region of spiral galaxies as seen by Herschel M 81, M 99, and M 100

) and could be distributed in small clumps (sizexa0