Mathematics – Logic
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...21115306l&link_type=abstract
American Astronomical Society, AAS Meeting #211, #153.06; Bulletin of the American Astronomical Society, Vol. 39, p.1005
Mathematics
Logic
Scientific paper
The diffuse interstellar bands (DIBs) are absorption profiles thought to be due to organic molecules such as polycyclic aromatic hydrocarbons. These molecules are ubiquitous in the Galaxy and may be of astrobiological importance. Observations of DIBs in the Galaxy are fairly mature and increasing rapidly in the Magellanic Clouds; however, studies of DIBs in other extragalactic sources are rare. We present a survey of DIBs in hydrogen (HI) rich galaxies known as damped Lyman-alpha (DLAs) systems and starbursting galaxies. These galaxies allow us to test the strengths of the DIBs in environments with varying amounts of gas, metallicity, reddening, and ionizing radiation. Understanding the environmental factors that enhance or inhibit the DIBs will give insight into the types of galaxies and cosmological epochs where these organic molecules arise.
We have DIB limits in six DLAs and DIB detections in the DLA with the highest HI content (z=0.5). The results suggest that DIBs in DLAs do not follow the Galactic HI-DIB relation, but they are not inconsistent with the DIBs in the Magellanic Clouds. Reddening is an important environmental factor for DIBs in DLAs. Our detection is consistent with the Galactic reddening-DIB relation. The limits indicate that DLAs are low in reddening suggesting that the environments of DLAs are not conducive to sustaining the organics that produce the DIBs. We also present preliminary findings of DIBs in 19 starbursting galaxies. Starbursting galaxies have significant reddening suggesting that DIBs may be more plentiful in starbursting galaxies than DLAs. Detections of DIBs in the z=0.5 DLA proves that the organics responsible for the DIBs existed in the Universe 5 billion years ago. More observations will allow us to determine the evolution of DIBs in cosmic time. Brandon Lawton acknowledges the support of NASA via the GSRP fellowship which helped fund this research dissertation.
Churchill Christopher W.
Ellison Sara L.
Johnson Rachel A.
Lawton Brandon L.
Rupke David S.
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