120 research outputs found
Filosofi, joka ei hukkunut hallintoon
Ilkka Niiniluoto: Dynaaminen sivistysyliopisto. Sata puhetta ja
kirjoitusta vuosilta 1987â2010.
Gaudeamus 2011
Feminismin kolme aaltoa
Kirja-arvostelu: Sukupuolen jÀrjestykset ja tasa-arvon paradoksit / Raija Julkunen. Vastapaino, 2010
VielÀ kerran Kiviselle ja Hedmanille
On aika lopettaa tÀmÀ keskustelu, jota ei voi keskusteluksi sanoa
Search for Hââș isotopologues toward CRL 2136 IRS 1
Context. Deuterated interstellar molecules frequently have abundances relative to their main isotopologues much higher than the overall elemental D-to-H ratio in the cold dense interstellar medium. Hââș and its isotopologues play a key role in the deuterium fractionation; however, the abundances of these isotopologues have not been measured empirically with respect to Hââș to date.
Aims. Our aim was to constrain the relative abundances of HâDâș and Dââș in the cold outer envelope of the hot core CRL 2136 IRS 1.
Methods. We carried out three observations targeting Hââș and its isotopologues using the spectrographs CRIRES at the VLT, iSHELL at IRTF, and EXES on board SOFIA. In addition, the CO overtone band at 2.3 ÎŒm was observed by iSHELL to characterize the gas on the line of sight.
Results. The Hââș ion was detected toward CRL 2136 IRS 1 as in previous observations. Spectroscopy of lines of HâDâș and Dââș resulted in non-detections. The 3Ï upper limits of N(HâDâș)/N(Hââș) and N(Dââș)/N(Hââș) are 0.24 and 0.13, respectively. The population diagram for CO is reproduced by two components of warm gas with the temperatures 58 and 530 K, assuming a local thermodynamic equilibrium (LTE) distribution of the rotational levels. Cold gas (<20 K) makes only a minor contribution to the CO molecular column toward CRL 2136 IRS 1.
Conclusions. The critical conditions for deuterium fractionation in a dense cloud are low temperature and CO depletion. Given the revised cloud properties, it is no surprise that Hââș isotopologues are not detected toward CRL 2136 IRS 1. The result is consistent with our current understanding of how deuterium fractionation proceeds
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