A SEARCH FOR 95 GHz CLASS I METHANOL MASERS IN MOLECULAR OUTFLOWS

Abstract

We have observed a sample of 288 molecular outflow sources including 123 high-mass and 165 low-mass sources to search for class I methanol masers at 95 GHz transition and to investigate relationship between outflow characteristics and class I methanol maser emission with the PMO-13.7m radio telescope. Our survey detected 62 sources with 95 GHz methanol masers above 3σ detection limit, which include 47 high-mass sources and 15 low-mass sources. Therefore the detection rate is 38% for high-mass outflow sources and 9% for low-mass outflow sources, suggesting that class I methanol maser is relatively easily excited in high-mass sources. There are 37 newly detected 95 GHz methanol masers (including 27 high-mass and 10 low-mass sources), 19 of which are newly identified (i.e. first identification) class I methanol masers (including 13 high-mass and 6 low-mass sources). Statistical analysis for the distributions of maser detections with the outflow parameters reveals that the maser detection efficiency increases with outflow properties (e.g. mass, momentum, kinetic energy and mechanical luminosity of outflows etc.). Systematic investigations of relationships between the intrinsic luminosity of methanol maser and the outflow properties (including mass, momentum, kinetic energy, bolometric luminosity and mass loss rate of central stellar sources) indicate a positive correlations. This further supports that class I methanol masers are collisionally pumped and associated with shocks, where outflows interact with the surrounding ambient medium.

A New 95 GHz Methanol Maser Catalog. I. Data

“…BGPS sources 1314 and 1710 were previously detected with the Mopra telescope (Chen et al 2011(Chen et al , 2013a, and the smaller beam size and southerly declination of these two sources mean that the previous observations have higher signal-to-noise than those reported here. Similarly, the observations of BGPS sources 1421, 6657, and 6955 by Gan et al (2013) have better signal-to-noise than our observations and so for the catalog we take the parameters from the published literature.…”

“…However, there were no systematic searches for the 95 GHz maser transition until Kalenskii et al (1994). We have combined the results of all previous 95 GHz methanol maser single-dish searches that are reported in Kalenskii et al (1994), Val'tts et al (1995, 2000, Ellingsen (2005), Kalenskii et al (2006), Fontani et al (2010), Chen et al (2011Chen et al ( , 2012Chen et al ( , 2013a, and Gan et al (2013) to produce a catalog of all maser sources in this transition.…”

“…This results in variable precision in estimates of sources parameters such as flux density, peak velocity, etc. Except for the sources detected by Chen et al (2011Chen et al ( , 2012 and Gan et al (2013), and in this survey, rms noise information was not given for individual sources. The sources detected by Kalenskii et al (2006) are given in units of antenna temperature, and those by Chen et al (2013a) are given in units of main beam temperature rather than flux density.…”

“…Recent interferometric observations (Kurtz et al 2004;Gómez et al 2010;Voronkov et al 2014;Gómez-Ruiz et al 2016) of 44 GHz class I methanol masers have improved our understanding of this transition. For the 95 GHz methanol masers, surveys toward the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) Extended Green Objects (EGOs; Chen et al 2011Chen et al , 2013a, and molecular outflow sources (Gan et al 2013) and cross-matching between the GLIMPSE point sources and the Bolocam Galactic Plane Survey (BGPS) sources (Chen et al 2012) have significantly increased the number of 95 GHz methanol masers that are known and the number of known class I maser regions in general. To date, high-resolution observations of the 95 GHz transition have only been made toward a few famous star-forming regions (e.g., Orion-KL (Plambeck & Wright 1988), DR 21 (Plambeck & Menten 1990), W33 and W51 (Pratap & Menten 1993)).…”

Radio and infrared study of the star-forming region IRAS 20286+4105

“…IRAS 20286+4105 has also been the target of many surveys to detect masers. Water, ammonia and Class I Methanol masers have been detected towards this region (Palla et al 1991;Brand et al 1994; Codella, Felli & Natale 1996; Molinari et al 1996; Urquhart et al 2011;Gan et al 2013). However, the search for Class II methanol and hydroxyl masers yielded negative results (van der Walt, Gaylard & MacLeod 1995; Edris, Fuller & Cohen 2007).…”