Class I methanol masers are believed to be produced in the shock-excited environment around star-forming regions. Many authors have argued that the appearance of various subsets of class I masers may be indicative of specific evolutionary stages of star formation or excitation conditions. Until recently, however, no major interferometer was capable of imaging the important 36 GHz transition. We report on Expanded Very Large Array observations of the 36 GHz methanol masers and Submillimeter Array observations of the 229 GHz methanol masers in DR21(OH), DR21N, and DR21W. The distribution of 36 GHz masers in the outflow of DR21(OH) is similar to that of the other class I methanol transitions, with numerous multitransition spatial overlaps. At the site of the main continuum source in DR21(OH), class I masers at 36 and 229 GHz are found in virtual overlap with class II 6.7 GHz masers. To the south of the outflow, the 36 GHz masers are scattered over a large region but usually do not appear coincident with 44 GHz masers. In DR21W, we detect an "S-curve" signature in Stokes V that implies a large value of the magnetic field strength if interpreted as due to Zeeman splitting, suggesting either that class I masers may exist at higher densities than previously believed or that the direct Zeeman interpretation of S-curve Stokes V profiles in class I masers may be incorrect. We find a diverse variety of different maser phenomena in these sources, suggestive of differing physical conditions among them.

Ground-based observations of the 11.072-GHz line of ozone were made from January 2008 through January 2009. These observations provide an estimate of the diurnal and seasonal variations of ozone in the mesopause region. The 11-GHz line is more sensitive to the ozone at higher altitudes than ground observations of the 142-GHz line, because of the reduced Doppler line width. The observations show an increase in the volume mixing ratio of ozone above 80 km at night by more than a factor of 10 and a seasonal variation of about a factor of 2, which is consistent with the semiannual variations of atomic hydrogen in the mesopause region. The diurnal amplitude and rates of change of the mixing ratios at sunrise and sunset are compared with ground-based observations of the 142-GHz line and the observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite, as well as with a simplified chemical model of the creation and destruction of ozone in the mesopause region.

Class I methanol masers appear to probe very early stages of star formation. An observational survey of the 44 and 36 GHz methanol lines toward several star-forming regions was conducted using the Haystack Observatory 37 m telescope. Examining the intensities of the 36 GHz Class I maser line as compared to the 44 GHz maser line, it is seen that the 36 GHz line is enhanced toward sources where there is no apparent sign of star formation. Sources where the 36 GHz emission is absent, but the 44 GHz emission is strong, appear to be those where ultracompact H II regions and millimeter continuum sources are present. Existing models for the excitation of Class I methanol masers show strong temperature and density dependences for the presence or lack of certain methanol transitions. The 36 GHz masers appear in regimes where the temperatures are low-below 100 K. The 44 GHz masers are excited in a wider range of gas temperatures (80-200 K), supporting the hypothesis that these transitions are still masing even when the 36 GHz masers are quenched.

AbstractClass I methanol masers are found near regions of high-mass star formation and are pumped by collisions. Some indication of long-term variability in these masers has previously been reported (Kurtz et al. 2004). Here we will present evidence for variations in the intensity of the Class I methanol masers at 44 GHz on much shorter timescales. We present preliminary results of the observation of the 44 GHz Class I methanol transition toward sources in the DR21 region that indicates variability on timescales of days to possibly hours.

Abstract OH(1720 MHz) and methanol masers are now recognized to be excellent probes of the interactions of supernova remnants with molecular clouds and tracers of massive star formation, respectively. To better understand the nature of star formation activity in the central region of the Galaxy, we have used these two classes of masers combined with the IRAC and MIPS data to study prominent sites of ongoing star formation in the nuclear disk. The nuclear disk is characterized by massive GMCs with elevated gas temperatures, compared to their dust temperatures. We note an association between methanol masers and a class of mid-infrared “green sources”. These highly embedded YSOs show enhanced 4.5μm emission due to excited molecular lines. The distribution of methanol masers and supernova remnants suggest a low efficiency of star formation (with the exception of Sgr B2), which we believe is due to an enhanced flux of cosmic ray electrons impacting molecular clouds in the nuclear disk. We also highlight the importance of cosmic rays in their ability to heat molecular clouds, and thus increase the gas temperature.