Browsing by Author "Vutisalchavakul, Nalin"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Star formation in molecular clouds(2015-08) Vutisalchavakul, Nalin; Evans, Neal J.; Bromm, Volker; Lacy, John; Gebhardt, Karl; Heyer, Mark; Jogee, ShardhaThere has been many recent observations in the area of star formation. High-resolution observations of other galaxies enabled a study of extragalactic star formation in more detailed while large scale surveys of the Milky Way enabled a more comprehensive study of Galactic star formation. The main goal of this thesis is to use multi-wavelength, large-scale observations of the Milky Way to connect Galactic to extragalactic star formation and to study star formation regulation in molecular clouds. We tested the use of extragalactic star formation rate tracers on nearby molecular clouds and found that the total infrared and 24 μm luminosity underestimate star formation rates of nearby molecular clouds by a large factor, indicating a problem of using extragalactic tracers of star formation on small regions and regions with low mass or low star formation rates. We studied the relation between star formation and molecular gas distribution in a 11 square degree of the Galactic Plane on various spatial scales starting from a clump scale of around few parsecs to a scale of ≈ 200 parsec. The result shows a good correlation between molecular gas and star formation on a scale above ≈ 5 − 8′. The star formation relation that is seen on disk-averaged scales in other galaxies shows a large scatter on the small scales. We built a catalog of Galactic molecular clouds with measured star formation rates and studied the relations between properties of molecular clouds and star formation. We tested several models of star formation on the catalog of molecular clouds. We found that the dense gas mass shows significant correlations with star formation rates but the depletion time of dense gas varies with other properties of the clouds. We found that the free- fall efficiency is higher in dense gas compared to the general molecular gas of the clouds.Item The use of extra-galactic star formation tracers on star forming regions in the Milky Way(2011-08) Vutisalchavakul, Nalin; Evans, Neal J.; Lacy, JohnWe studied three groups of star forming clouds in the Milky Way: 5 clouds from Spitzer c2d Legacy survey, 10 clouds from Gould Belt survey, and 32 massive dense clumps. We determined the total diffuse 24[Greek letter mu] emission for each cloud and calculated the corresponding SFR using an extragalactic relation. Then the resulting SFRs were compared with SFRs calculated using the method of counting number of YSOs for c2d and Gould Belt clouds and using total infrared luminosity for massive dense clumps. The comparison shows quite a good correlation for the massive dense clumps, which are high-mass star forming regions, with the average ratio of SFR(L_IR)/SFR(25[Greek letter mu]) = 0.896+/-0.663. The result for low-mass star forming clouds (c2d and Gould Belt) shows very little to no correlation between L_24[Greek letter mu] and SFR(YSO count). Comparing 24[Greek letter mu] images with extinction maps shows that a significant portion of 24[Greek letter mu] emission does not come from star-forming regions in the cloud.