H2O masers in HII regions (Cadella+, 1994)

Details H2O masers in HII regions (Cadella+, 1994) H2O masers in HII regions (Cadella+, 1994)

Jun 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994ycat..32910261c&link_type=abstract

VizieR On-line Data Catalog: J/A+A/291/261. Originally published in: 1994A&A...291..261C

Computer Science

Masers, H Ii Regions

Scientific paper

The results of a survey of 22.2GHz H2O maser emission towards a large sample of HII regions (427) detected in hydrogen recombination lines (Lockman) are presented. The sample favours classical HII regions with large excitation parameter. We found 68 water maser sources, 17 of which are new detections. Adding the detections found in the literature, the total number of masers associated with the sample is 80. The overall maser percentage is low (19%), much less than what found in samples of ultracompact (UC) HII regions. The percentage changes if we divide our sample into two sub-classes: HII regions known to have ultracompact components (i.e. where a younger generation of star formation is also present) and the rest. In the first sub-class the maser percentage is 28%, in the second 15%. The total number of masers in HII regions where no UC component has been (so far) reported is 43. This value is greater than that expected from the ratio between the lifetime of the HII region (106yr) and that of the maser phase, even assuming a maser lifetime as long as 105yr. This implies that maser excitation (and star formation) occurs several times in the lifetime of the same star forming complex. From 410 positions observed, 230 can be associated with a high degree of confidence to an IRAS Point Source. We expect that most of the HII regions not associated with IRAS PS are diffuse regions in the last phases of their evolution. The percentage of water masers in this sub-class is very low: 8%. The number of masers with no counterpart in the Lockman sample (and above Dec=-30°) is very large: 334. This number most probably reflects the extreme high density conditions known to exist in the earliest phases of an HII region, which strongly reduce its radio continuum and line emission. The analysis of a homogeneous sample of classical HII regions allows to confirm in a quantitative fashion the well known result that the maser phenomenon occurs during the earliest phase of the evolution of a massive star and that it fades away as the HII region evolves into the diffuse stage.
(4 data files).

Affiliated with

Also associated with

No associations

Rating

H2O masers in HII regions (Cadella+, 1994) 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 H2O masers in HII regions (Cadella+, 1994), we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and H2O masers in HII regions (Cadella+, 1994) will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1509773