ISM properties in low-metallicity environments
Journal Articles
Overview
Research
Identity
Additional Document Info
View All
Overview
abstract
We present new 450 and 850 microns SCUBA data of the dwarf galaxy NGC 1569.
We construct the mid-infrared to millimeter SED of NGC 1569, using ISOCAM,
ISOPHOT, IRAS, KAO, SCUBA and MAMBO data, 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 ISRF penetrating a clumpy
environment and a size-segregation of grains where the emission is dominated by
small grains of size ~3 nm, consistent with the idea of shocks having a
dramatic effect on the dust properties in NGC 1569. A significant millimetre
excess is present in the dust SED which can be explained by the presence of
ubiquitous very cold dust (T = 5-7 K). This dust component accounts for 40 to
70 % of the total dust mass in the galaxy (1.6 - 3.4 10^5 Msol) and could be
distributed in small clumps (size a few pc) throughout the galaxy. We find a
gas-to-dust mass ratio of 740 - 1600, larger than that of the Galaxy and a
dust-to-metals ratio of 1/4 to 1/7. We generate an extinction curve for NGC
1569, consistent with the modeled dust size distribution. This extinction curve
has relatively steep FUV rise and smaller 2175 Angstroms bump, resembling the
observed extinction curve of some regions in the Large Magellanic Cloud.
