We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
from 3 - Observations and Models
Published online by Cambridge University Press: 04 August 2010
A review is presented of ISO observations of molecular hydrogen, H2, toward various Galactic source types, such as shocks and photon dominated regions. In so doing I examine the similarities and differences in the H2 spectrum found under these different excitation conditions and mechanisms, and how the observations impact on some of the latest models.
Introduction
Before the launch of the Infrared Space Observatory (ISO, Kessler et al. 1996) observations of H2 were restricted to a hot component with an excitation temperature of about 2000 K in shock excited sources, and a non-thermally (i.e. fluorescently) excited component in photon dominated regions (PDRs). These components were typically probed with the 1–0 S(1) line at 2.12 µm as well as several other near-infrared ro-vibrational transitions, and in some cases pure rotational transitions from high J levels (e.g. Gredel 1994, Knacke & Young 1981). Only a few observations, principally toward the Orion star forming region, of lower energy pure rotational transitions existed, e.g. the 0–0 S(2) and 0–0 S(1) lines at 12.2786 and 17.0348 µm, but which already pointed to the existence of a lower temperature component in such sources (e.g. Beck, Lacy & Geballe 1979; Parmar, Lacy & Achtermann 1991, 1994; Richter et al. 1995; Burton & Haas 1997).
To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.
