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 $v=1$.

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

References in corpus (48)

• Embedded Clusters in Molecular Clouds
• The Milky Way in Molecular Clouds: A New Complete CO Survey
• GLIMPSE: I. A SIRTF Legacy Project to Map the Inner Galaxy
• Toward Understanding Massive Star Formation
• 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
• Physical Conditions in Regions of Star Formation
• Systematic Molecular Differentiation in Starless Cores
• A Catalog of Extended Green Objects (EGOs) in the GLIMPSE Survey: A new sample of massive young stellar object outflow candidates
• The Southern Galactic Plane Survey: HI Observations and Analysis
• The Australia Telescope Compact Array Broadband Backend (CABB)
• The initial conditions of stellar protocluster formation. I. A catalogue of Spitzer dark clouds
• The Red MSX Source Survey: the Massive Young Stellar Population of our Galaxy
• A Class I and Class II Methanol Maser Survey of Extended Green Objects (EGOs) from the GLIMPSE Survey
• How Many Infrared Dark Clouds can form Massive Stars and Clusters?
• The ATLASGAL survey: a catalog of dust condensations in the Galactic plane
• Methanol masers : Reliable tracers of the early stages of high-mass star formation
• The H_2O southern Galactic Plane Survey (HOPS): I. Techniques and H_2O maser data
• The Co-ordinated Radio and Infrared Survey for High-Mass Star Formation - II. Source Catalogue
• The 6-GHz Multibeam Maser Survey I. Techniques
• Molecular Excitation and Differential Gas-Phase Depletions in the IC 5146 Dark Cloud
• The 6-GHz methanol multibeam maser catalogue IV: Galactic longitudes 186 to 330 including the Orion-Monoceros region
• Confirmation of the exclusive association between 6.7-GHz methanol masers and high-mass star formation regions
• Southern class I methanol masers at 36 and 44 GHz
• An Improved Model of SiO Maser Emission in Miras
• The Mopra Southern Galactic Plane CO Survey
• A 95 GHz Class I Methanol Maser Survey Toward GLIMPSE Extended Green Objects (EGOs)
• The RMS Survey: Near-IR Spectroscopy of Massive Young Stellar Objects
• The H2O southern Galactic Plane Survey(HOPS): NH3 (1,1) and (2,2) catalogues
• Detection of new sources of methanol emission at 95 GHz with the Mopra telescope
• CO bandhead emission of massive young stellar objects: determining disc properties
• Accurate water maser positions from HOPS
• The Relationship between Class I and Class II Methanol Masers
• Molecular line mapping of the giant molecular cloud associated with RCW 106 - III. Multi-molecular line mapping
• New 9.9-GHz methanol masers
• 86 GHz SiO maser survey of late-type stars in the Inner Galaxy. I. Observational data
• An Extensive, Sensitive Search for SiO Masers in High- and Intermediate-Mass Star-Forming Regions
• SPLASH: The Southern Parkes Large-Area Survey in Hydroxyl - First Science from the Pilot Region
• Detection of Class I Methanol (CH3OH) Maser Candidates in Supernova Remnants
• Expanded VLA Detection of 36.2 GHz Class I Methanol Masers in Sagittarius A
• Characterisation of the Mopra Radio Telescope at 16--50 GHz
• A search for water masers associated with class II methanol masers - I. Longitude range 6 to 20 degrees
• A search for 95 GHz class I methanol masers in molecular outflows
• High-velocity feature of the class I methanol maser in G309.38-0.13
• Radio and infrared recombination studies of the southern massive star-forming region G333.6-0.2
• Four highly luminous massive star forming regions in the Norma Spiral Arm.: I. Molecular gas and dust observations
• Molecular line mapping of the giant molecular cloud associated with RCW 106 - IV. Ammonia towards dust emission
• Pilot Observations for MALT-45: A Galactic Plane Survey at 7mm

Cited by in corpus (23)

• Planck 2015 results. XXV. Diffuse low-frequency Galactic foregrounds
• The HI/OH/Recombination line survey of the inner Milky Way (THOR): data release 2 and HI overview
• Online Database of Class I Methanol Masers
• H2O Southern Galactic Plane Survey (HOPS): Paper III - Properties of Dense Molecular Gas across the Inner Milky Way
• Discovery of six new class II methanol maser transitions, including the unambiguous detection of three torsionally excited lines toward G358.931-0.030
• OH maser emission in the THOR survey of the northern Milky Way
• A search for water masers associated with class II methanol masers - II. Longitude range 341${}^{\circ }$ to 6${}^{\circ }$
• 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
• Simultaneous observation of water and class I methanol masers toward class II methanol maser sources
• 84-GHz methanol masers, their relationship to 36-GHz methanol masers and their molecular environments
• Simultaneous Survey of Water and Class I Methanol Masers toward Red MSX Sources
• MALT-45: A 7mm survey of the southern Galaxy - II. ATCA follow-up observations of 44GHz class I methanol masers
• 44 GHz methanol masers: Observations toward 95 GHz methanol masers
• The physical parameters of clumps associated with class I methanol masers
• The first high-resolution observations of 37.7-, 38.3- and 38.5-GHz methanol masers
• A First Look for Molecules between 103 and 133 MHz using the Murchison Widefield Array
• MAGMO: Polarimetry of 1720-MHz OH Masers towards Southern Star Forming Regions
• Scaled up low-mass star formation in massive star-forming cores in the G333 giant molecular cloud
• Gas kinematics in massive star-forming regions from the Perseus spiral arm
• 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
• Interferometry of class I methanol masers, statistics and the distance scale