Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-12-13
Nature 432 (2004) 369
Astronomy and Astrophysics
Astrophysics
3 Nature pages
Scientific paper
10.1038/nature03054
We know little about the outermost portions of galaxies because there is little light coming from them. We do know that in many cases atomic hydrogen (HI) extends well beyond the optical radius \cite{Casertano91}. In the centers of galaxies, however, molecular hydrogen (H2) usually dominates by a large factor, raising the question of whether H2 is abundant also in the outer regions but hitherto unseen.Here we report the detection of emission from carbon monoxide (CO), the most abundant tracer of H2, beyond the optical radius of the nearby galaxy NGC 4414. The molecular clouds probably formed in the regions of relatively high HI column density and in the absence of spiral density waves. The relative strength of the lines from the two lowest rotational levels indicates that both the temperature and density of the H2 are quite low compared to conditions closer to the center. The inferred surface density of the molecular material continues the monotonic decrease from the inner regions. We conclude that while molecular clouds can form in the outer region of this galaxy, there is little mass associated with them.
Braine Jonathan
Herpin Fabrice
No associations
LandOfFree
Molecular hydrogen beyond the optical edge of an isolated spiral galaxy does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Molecular hydrogen beyond the optical edge of an isolated spiral galaxy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molecular hydrogen beyond the optical edge of an isolated spiral galaxy will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-114846