Detection of a new methanol maser line with the Kitt Peak 12-m telescope by remote observing from Moscow

A new methanol maser line 6(-1)-5(0)E at 133 GHz was detected with the 12-m Kitt Peak radio telescope using remote observation mode from Moscow. Moderately strong, narrow maser lines were found in DR21(OH), DR21-W, OMC-2, M8E, NGC2264, L379, W33-Met. The masers have similar spectral features in other transitions of methanol-E at 36 and 84 GHz, and in transitions of methanol-A at 44 and 95 GHz. All these are Class I transitions, and the new masers also belong to Class I. In two other methanol transitions near 133 GHz, 5(-2)-6(-1)E and 6(2)-7(1)A+, only thermal emission was detected in some sources. Several other sources with wider lines in the transition 6(-1)-5(0)E also may be masers, since they do not show any emission at the two other methanol transitons near 133 GHz. These are NGC2071, S231, S255, GGD27, also known as Class I masers. The ratio of intensities and line widths of the 133 GHz masers and 44 GHz masers is consistent with the saturated maser model, in which the line rebroadening with respect to unsaturated masers is suppressed by cross relaxation due to elastic collisions.Comment: 4 pages, AASTeX text, uses aasms4.sty, 2 Postscript figures, to be published in Ap

Class I methanol masers in low-mass star formation regions

Four Class I maser sources were detected at 44, 84, and 95 GHz toward chemically rich outflows in the regions of low-mass star formation NGC 1333I4A, NGC 1333I2A, HH25, and L1157. One more maser was found at 36 GHz toward a similar outflow, NGC 2023. Flux densities of the newly detected masers are no more than 18 Jy, being much lower than those of strong masers in regions of high-mass star formation. The brightness temperatures of the strongest peaks in NGC 1333I4A, HH25, and L1157 at 44 GHz are higher than 2000 K, whereas that of the peak in NGC 1333I2A is only 176 K. However, rotational diagram analysis showed that the latter source is also a maser. The main properties of the newly detected masers are similar to those of Class I methanol masers in regions of massive star formation. The former masers are likely to be an extension of the latter maser population toward low luminosities of both the masers and the corresponding YSOs.Comment: 5 pages, 1 figure, Proc. IAU Symp. 287 "Cosmic Masers: from OH to H0". LSR velocities of the HH25 masers, which are presented in Table 1, are correcte

Non-equilibrium excitation of methanol in Galactic molecular clouds: multi-transitional observations at 2 mm

We observed 14 methanol transitions near lambda=2 mm in Galactic star-forming regions. Broad, quasi-thermal J(0)-J(-1)E methanol lines near 157 GHz were detected toward 73 sources. Together with the 6(-1)-5(0)E and 5(-2)-6(-1)E lines at 133 GHz and the 7(1)-7(0)E line at 165 GHz, they were used to study the methanol excitation. In the majority of the observed objects, the Class I 6(-1)-5(0)E transition is inverted, and the Class II 5(-2)-6(-1)E and 6(0)-6(-1)E transitions are overcooled. This is exactly as predicted by models of low gain Class I masers. The absence of the inversion of Class II transitions 5(-2)-6(-1)E and 6(0)-6(-1)E means that quasi-thermal methanol emission in all objects arises in areas without a strong radiation field, which is required for the inversion.Comment: 23 pages paper (uses aasms4.sty), 12 pages tables (uses apjpt4.sty), 10 Jpeg figures, submitted to the ApJ

Spectral Survey of the Star Formation Region DR21OH in the 4 mm Wavelength Range

The results of a spectral survey of the region of massive star formation DR21OH in the 4-mm wavelength range are presented. Sixty-nine molecules and their isotopologues have been detected, ranging from simple diatomic or triatomic species such as SO, SiO and CCH, to complex organic molecules such as CH$_3$OCHO or CH$_3$OCH$_3$. The obtained results qualitatively repeat the results of the survey of the same source at 3~mm. The inventories of molecules found at 3mm and 4mm overlap to a great extent. However, at 4 mm we found a number of species that have no allowed transitions in the 3-mm wavelength range, e.g. DCN, DNC, or SO$^+$. The bulk of the molecules detected at 4~mm are those that are common for dense cores, e.g., HC$_3$N or CH$_3$CCH, but some of the detected species are typical for hot cores. The latter include complex organic molecules CH$_3$OCHO, CH$_3$CH$_2$OH, CH$_3$OCH$_3$, etc. However, the detected emission of these molecules probably arises in a gas heated to 30 K only. Nine molecules, including complex species CH$_3$C$_3$N, CH$_3$CH$_2$CN, CH$_3$COCH$_3$, were found by spectral line stacking. This demonstrates the prospects of the method in the study of molecular clouds.Comment: 36 pages, 4 figure

Masers in star forming regions

Maser emission plays an important role as a tool in star formation studies. It is widely used for deriving kinematics, as well as the physical conditions of different structures, hidden in the dense environment very close to the young stars, for example associated with the onset of jets and outflows. We will summarize the recent observational and theoretical progress on this topic since the last maser symposium: the IAU Symposium 242 in Alice Springs.Comment: Submitted to Proceedings of IAU Symposium No. 287, Cosmic masers - from OH to H

APEX Millimeter Observations of Methanol Emission Toward High-Mass Star-Forming Cores

We present 247-GHz molecular line observations of methanol (CH$_3$OH) toward sixteen massive star-forming regions, using the APEX telescope with an angular resolution of $25''$. The sample covers a range of evolutionary states, including warm molecular cores, hot molecular cores, and ultracompact HII regions. The hot cores, all of which include UC HII regions, show rich molecular line spectra, although the strength of different species and transitions varies from source to source. In contrast, the warm cores do not show significant molecular line emission. Multiple methanol transitions are detected toward nine of the hot cores; eight of these had enough transitions to use the rotation diagram method to estimate rotational temperatures and column densities. The temperatures lie in the range 104$-$168 K and column densities from $3\times10^{16}$ to $7\times10^{18}$ cm$^{-2}$. Using the average methanol line parameters, we estimate virial masses, which fall in the range from 145 to 720 M$_\odot$ and proved to be significantly higher than the measured gas masses. We discuss possible scenarios to explain the chemical differences between hot cores and warm molecular cores. One of the observed methanol lines, $4_{2}-5_{1}A^{+}$ at 247.228 GHz, is predicted to show class II maser emission, similar in intensity to previously reported $J_0-J_{-1}E$ masers at 157 GHz. We did not find any clear evidence for maser emission among the observed sources; however, a weak maser in this line may exist in G345.01+1.79.Comment: Accepted for publication in The Astronomical Journa

A search for massive young stellar objects towards 98 CH3_{3}OH maser sources

Using the 13.7 m telescope of Purple Mountain Observatory (PMO), a survey of J=1-0 lines of CO and its isotopes was carried out towards 98 methanol maser sources in January 2008. Eighty-five sources have infrared counterparts within one arcmin. In the survey, except 43 sources showing complex or multiple-peak profiles, almost all the $^{13}$CO line profiles of the other 55 sources have large line widths of 4.5 km s$^{-1}$ on average and are usually asymmetric. Fifty corresponding Infrared Astronomical Satellite (IRAS) sources of these 55 sources are with $L_{bol}$ larger than $10^{3}L_{\odot}$, which can be identified as possible high-mass young stellar sources. Statistics show that the $^{13}$CO line widths correlate with the bolometric luminosity of the associated IRAS sources. We also report the mapping results of two sources: IRAS 06117+1350 and IRAS 07299-1651 here. Two cores were found in IRAS 06117+1350 and one core was detected in IRAS 07299-1651. The northwest core in IRAS 06117+1350 and the core in IRAS 07299-1651 can be identified as precursors of UC\simH{\sc ii} regions or high-mass protostellar objects (HMPOs). The southeast core of IRAS 06117+1350 has no infrared counterpart, seeming to be on younger stages than pre-UC\simH{\sc ii} phase.Comment: A search for massive young stellar objects. Accepted to RAA in 201