Cosmic rays (CR) are ubiquitous in the Galaxy and have the important role of ionizing the dens gas of the ISM. New Herschel observations have shown the huge diagnostic power of the OH+ fundamental transition to measure the CR ionization rate in diffuse clouds. Based on previous serendipity observations toward OMC2-FIR4 within the KP CHESS, we discovered a tenuous foreground cloud absorbing the fundamental OH+ line. Similarly, Gupta et al. (2010) found an OH+ absorption component at a similar velocity towards Orion KL and estimated a large CR ionization rate more than 10 times larger than the average value observed in diffuse clouds . We propose here to roughly map the CR ionization rate in the direction of the OMC2 and OMC3 complex to understand its extent, nature, and, finally, the source of ionization.
Publication
Herschel CHESS discovery of the fossil cloud that gave birth to the Trapezium and Orion KL | Lopez-Sepulcre A. et al. | Astronomy & Astrophysics Volume 549 id.A114 9 pp. | 549 | 10.1051\\/0004-6361\\/201219416 | 2013A&A...549A.114L | http://adsabs.harvard.edu/abs/2013A%26A...549A.114L
Instrument
HIFI_HifiPoint_dbs
Temporal Coverage
2012-02-22T16:15:13Z/2012-02-22T16:32:15Z
Version
SPG v14.1.0
Mission Description
Herschel was launched on 14 May 2009! It is the fourth cornerstone mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
European Space Agency, lopez-sepulcre et al., 2012, 'Mapping the cosmic ray ionisation rate across the Northern end of the Orion A iant molecular cloud', SPG v14.1.0, European Space Agency, https://doi.org/10.5270/esa-ulwz78w
