منابع مشابه
Enigma of H3 + in Diffuse Interstellar Clouds
1. INTRODUCTION H 3 + is of fundamental importance to interstellar chemistry both because it is a hydrogenic species (and >90% of all nuclei in the universe are hydrogen nuclei; see Figure 1) and because it serves as the universal protonator, initiating a chain of ion-neutral reactions that is responsible for the formation of most interstellar molecules. The chemistry of H 3 + in dense (molecul...
متن کاملExtragalactic molecular clouds and chemistry of diffuse interstellar clouds
Zusammenfassung Since the discovery of a cold molecular component of the interstellar medium in the 1970s, it has been realized that most of the dark clouds are actually molecular clouds, consisting mainly of molecular hydrogen and some amount of dust and other molecules. Nowadays, molecular clouds are recognized as places of star-formation in the Milky Way and other galaxies. Therefore, studie...
متن کاملNon-Thermal Chemistry in Diffuse Clouds with Low Molecular Abundances
High quality archival spectra of interstellar absorption from C I toward 9 stars, taken with the Goddard High Resolution Spectrograph on the Hubble Space Telescope, were analyzed. Our sample was supplemented by two sight lines, 23 Ori and β Sco, for which the C I measurements of Federman, Welty, & Cardelli were used. Directions with known CH absorption, but only upper limits on absorption from ...
متن کاملThe Thinnest Cold Hi Clouds in the Diffuse Interstellar Medium?
We confirm and discuss recently discovered cold HI clouds with column densities among the lowest ever detected. The column densities of Cold Neutral Medium (CNM) towards 3C286 and 3C287 are ∼ 10 cm, below an observational lower limit, and also below tiny-scale-atomic clouds detected by VLBI and time-variable profiles against pulsars. These column densities are close to the minimum imposed by th...
متن کاملExtinction Curves, Distances, and Clumpiness of Diffuse Interstellar Dust Clouds
We present CCD photometry in UBV RI of several thousand Galactic field stars in four large (> 1 degree) regions centered on diffuse interstellar dust clouds, commonly referred to as “cirrus” clouds (with optical depth AV less than unity). Our goal in studying these stars is to investigate the properties of the cirrus clouds. A comparison of the observed stellar surface density between on-cloud ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Highlights of Astronomy
سال: 1980
ISSN: 1539-2996
DOI: 10.1017/s1539299600004020