MALT-45: A 7 mm survey of the southern Galaxy - I. Techniques and spectral line data

Abstract

We present the first results from the MALT-45 (Millimetre Astronomer's Legacy Team - 45 GHz) Galactic Plane survey. We have observed 5 square-degrees ($l=330-335$, $b=\pm 0.5$) for spectral lines in the 7 mm band (42-44 and 48-49 GHz), including $\text{CS}$ $(1-0)$, class I ${\text{CH}}_3\text{OH}$ 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 ${\text{CH}}_3\text{OH}$ 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 ${\text{CH}}_3\text{OH}$ masers were associated with the published locations of class II ${\text{CH}}_3\text{OH}$, ${\text{H}}_2\text{O}$ 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 $Spitzer$ 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 $v=1$.

Accepted by Monthly Notices of the Royal Astronomical Society on 2015 January 23. Appendices will be published with MNRAS

References in corpus (11)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• A Catalog of Extended Green Objects (EGOs) in the GLIMPSE Survey: A new sample of massive young stellar object outflow candidates
• A Class I and Class II Methanol Maser Survey of Extended Green Objects (EGOs) from the GLIMPSE Survey
• The 6-GHz Multibeam Maser Survey I. Techniques
• An Improved Model of SiO Maser Emission in Miras
• Accurate water maser positions from HOPS
• Molecular line mapping of the giant molecular cloud associated with RCW 106 - III. Multi-molecular line mapping
• A search for water masers associated with class II methanol masers - I. Longitude range 6 to 20 degrees
• Radio and infrared recombination studies of the southern massive star-forming region G333.6-0.2
• Molecular line mapping of the giant molecular cloud associated with RCW 106 - IV. Ammonia towards dust emission

Cited by in corpus (6)

• A search for water masers associated with class II methanol masers - I. Longitude range 6 to 20 degrees
• A catalog of 44 GHz methanol masers in massive star-forming regions. IV. The high-mass protostellar object sample
• MALT-45: A 7mm survey of the southern Galaxy - II. ATCA follow-up observations of 44GHz class I methanol masers
• A First Look for Molecules between 103 and 133 MHz using the Murchison Widefield Array
• A study of the interstellar medium towards the unidentified dark TeV $\gamma$-ray sources HESS J1614-518 and HESS J1616-508
• HCN hyperfine ratio analysis of massive molecular clumps