We present the first results from the MALT-45 (Millimetre Astronomers Legacy Team - 45 GHz) Galactic Plane survey. We have observed 5 square-degrees ($l = 330 - 335$, $b = pm0.5$) for spectral lines in the 7 mm band (42-44 and 48-49 GHz), including $text{CS}$ $(1-0)$, class I $text{CH}_3text{OH}$ masers in the $7(0,7)-6(1,6)$ $text{A}^{+}$ transition and $text{SiO}$ $(1-0)$ $v=0,1,2,3$. MALT-45 is the first unbiased, large-scale, sensitive spectral line survey in this frequency range. In this paper, we present data from the survey as well as a few intriguing results; rigorous analyses of these science cases are reserved for future publications. Across the survey region, we detected 77 class I $text{CH}_3text{OH}$ masers, of which 58 are new detections, along with many sites of thermal and maser $text{SiO}$ emission and thermal $text{CS}$. We found that 35 class I $text{CH}_3text{OH}$ masers were associated with the published locations of class II $text{CH}_3text{OH}$, $text{H}_2text{O}$ and $text{OH}$ masers but 42 have no known masers within 60 arcsec. We compared the MALT-45 $text{CS}$ with $text{NH}_3$ (1,1) to reveal regions of $text{CS}$ depletion and high opacity, as well as evolved star-forming regions with a high ratio of $text{CS}$ to $text{NH}_3$. All $text{SiO}$ masers are new detections, and appear to be associated with evolved stars from the $it{Spitzer}$ Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). Generally, within $text{SiO}$ regions of multiple vibrational modes, the intensity decreases as $v=1,2,3$, but there are a few exceptions where $v=2$ is stronger than $v=1$.
تحميل البحث