Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userPilot Observations for MALT-45: A Galactic Plane Survey at 7mm
187
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We introduce the MALT-45 (Millimetre Astronomers Legacy Team - 45 GHz) Galactic plane survey and describe pilot survey results with the Australia Telescope Compact Array (ATCA). The pilot survey was conducted to test the instrumentation and observational technique of MALT-45, before commencing the full survey. We mapped two half-square degree regions within the southern Galactic plane around the G333 giant molecular cloud, using fast mosaic mapping. Using the new Compact Array Broadband Backend (CABB) on the ATCA, we were able to observe two 2048 MHz spectral windows, centred on frequencies 43.2 and 48.2 GHz. Although only a coarse spectral resolution of around 7 km/s was available to us, we detect widespread, extended emission in the CS (1-0) ground state transition. We also detect eight Class I CH3OH masers at 44 GHz and three SiO masers in vibrationally excited (1-0) transitions. We also detect the H53a radio recombination line, non-vibrationally excited SiO (1-0) and emission in the CH3OH 1_1-0_0 A+ line.
rate research
Read More
We detail interferometric observations of 44GHz class I methanol masers detected by MALT-45 (a 7mm unbiased auto-correlated spectral-line Galactic-plane survey) using the Australia Telescope Compact Array. We detect 238 maser spots across 77 maser sites. Using high-resolution positions, we compare the class I CH$_3$OH masers to other star formation maser species, including CS (1-0), SiO $v=0$ and the H53$alpha$ radio-recombination line. Comparison between the cross- and auto-correlated data has allowed us to also identify quasi-thermal emission in the 44GHz class I methanol maser line. We find that the majority of class I methanol masers have small spatial and velocity ranges ($<$0.5pc and $<$5 km s$^{-1}$), and closely trace the systemic velocities of associated clouds. Using 870$mu$m dust continuum emission from the ATLASGAL survey, we determine clump masses associated with class I masers, and find they are generally associated with clumps between 1000 and 3000 $M_odot$. For each class I methanol maser site, we use the presence of OH masers and radio recombination lines to identify relatively evolved regions of high-mass star formation; we find that maser sites without these associations have lower luminosities and preferentially appear toward dark infrared regions.
We report the results of a pilot program for a Green Bank Telescope (GBT) MUSTANG Galactic Plane survey at 3 mm (90 GHz), MGPS90. The survey achieves a typical $1sigma$ depth of $1-2$ mJy beam$^{-1}$ with a 9 beam. We describe the survey parameters, quality assessment process, cataloging, and comparison with other data sets. We have identified 709 sources over seven observed fields selecting some of the most prominent millimeter-bright regions between $0deg < ell < 50deg$ (total area $approx 7.5 deg^2$). The majority of these sources have counterparts at other wavelengths. By applying flux selection criteria to these sources, we successfully recovered several known hypercompact HII (HCHII) regions, but did not confirm any new ones. We identify 126 sources that have mm-wavelength counterparts but do not have cm-wavelength counterparts and are therefore candidate HCHII regions; of these, 10 are morphologically compact and are strong candidates for new HCHII regions. Given the limited number of candidates in the extended area in this survey compared to the relatively large numbers seen in protoclusters W51 and W49, it appears that most HCHII regions exist within dense protoclusters. Comparing the counts of HCHII to ultracompact HII (UCHII) regions, we infer the HCHII region lifetime is 16-46% that of the UCHII region lifetime. We additionally separated the 3 mm emission into dust and free-free emission by comparing with archival 870 $mu$m and 20 cm data. In the selected pilot fields, most ($gtrsim80$%) of the 3 mm emission comes from plasma, either through free-free or synchrotron emission.
We describe observations with the Mopra radiotelescope designed to assess the feasibility of the H$_2$O maser southern Galactic plane survey (HOPS). We mapped two one-square-degree regions along the Galactic plane using the new 12 mm receiver and the UNSW Mopra spectrometer (MOPS). We covered the entire spectrum between 19.5 and 27.5 GHz using this setup with the main aims of finding out which spectral lines can be detected with a quick mapping survey. We report on detected emission from H$_2$O masers, NH$_3$ inversion transitions (1,1), (2,2) and (3,3), HC$_3$N (3-2), as well as several radio recombination lines.
The Radio Ammonia Mid-Plane Survey (RAMPS) is a molecular line survey that aims to map a portion of the Galactic midplane in the first quadrant of the Galaxy (l = 10 deg - 40 deg, |b| < 0.4 deg) using the Green Bank Telescope. We present results from the pilot survey, which has mapped approximately 6.5 square degrees in fields centered at l = 10 deg, 23 deg, 24 deg, 28 deg, 29 deg, 30 deg, 31 deg, 38 deg, 45 deg, and 47 deg. RAMPS observes the NH3 inversion transitions NH3(1, 1) - (5, 5), the H2O 6(1,6) - 5(2,3) maser line at 22.235 GHz, and several other molecular lines. We present a representative portion of the data from the pilot survey, including NH3(1,1) and NH3(2,2) integrated intensity maps, H2O maser positions, maps of NH3 velocity, NH3 line width, total NH3 column density, and NH3 rotational temperature. These data and the data cubes from which they were produced are publicly available on the RAMPS website (http://sites.bu.edu/ramps/).
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 $v=1$.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
