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Star Formation in the Small Magellanic Cloud

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Star Formation in the Small Magellanic Cloud Star Formation in the Small Magellanic Cloud E. Sabbi (STScI) Why Star Formation? Galaxy evolution scheme Collapse of Star formation protogalaxy and/or mergers Stellar evolution, nucleosynthesis Gas in/out-flows Mass and Stellar mass loss composition and death of the ISM To understand galaxy evolution theoretical models observational constraints chemical abundances galaxy formation gas/star/dark masses chemical evolution kinematics dynamical evolution star formation history IMF The Color-Magnitude Diagram: Stellar Evolutionary Phases The magnitude of a star is a measure of its luminosity The color of a star is a measure of its temperature The position of a star in the CMD is uniquely relatedThe Sun to its mass, age, and chemical composition Simple Stellar populations In a Simple Stellar old globular population stars are clusters characterized by: the same age the same chemical composition they are all at the same distance young stellar clusters Simple Stellar populations TO Simple Stellar populations chemical composition similar to those of high high and low mass stars redshift galaxies but no but high metallicity high mass stars The Small Magellanic Cloud MW LMC SMC Star Formation Tracers UV OPTICAL IR RADIO hot & stars & dust supernovae massive stars ionized gas The Small Magellanic Cloud (II) It has been greatly distorted by tidal interaction with the MW; It differs from the MW: 1) for it gas content (gas- richer) 2) metal abundance (metal- poorer) The SMC in Space and in Time: HST 4 young clusters 7 old clusters 7 fields The 4 Young Clusters NGC 346 NGC 602 NGC 299 NGC 376 Deep HST/ACS V,I,Ha, & UV imaging HST/NICMOS Near-IR imaging NGC 346 BS90 SNR0057-7226 HD5980 NGC 346 is a complex region shaped by the powerful winds of its most massive stars, some of which have already exploded as SN ~5’ x 5’ SNR0056-88 x 88 pc 7233 NGC 346: CMD ~80000 stars with σ <0.1 in both bands, down to F555W = 26.2 (0.65 Mo) Old SMC population Young Population (NGC 346) ? The inner region Pre-MS spatial distribution Sub-clusters NGC 346: ongoing SF IR: Spitzer data A model BS90 Age ~ 4 Gyr Mass ~ 7 x 104 Mo NGC 602 NGC 602 is a small bright star forming region located in the SMC “Bridge” (Westerlund 1964, Massey et al. 2000) NGC 602 in the IR YSO IRAC 3.0μm IRAC 4.5μm IRAC 8.0μm Two twin clusters : NGC 376 & NGC 299 NGC 376 NGC 299 Conclusions NGC 346 NGC 602 NGC 299 NGC 376 2 Myr 30 Myr 3 Myr old The parent cloud 5 Myr old 25 Myr old of molecular gas Broken shell Even if located in environments which fragmentized in structure differ for stellar density and gas many coeval content, these two clusters appear sud-clusters Second generation almost identical. Second of stars in the generation of periphery stars in the periphery.
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