Tracking the Milky Way atomic and molecular gas

Figure 1: Top: Continuous radio image of the pilot area in the 28 ° range

An international team of researchers, led by the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, has combined the two most powerful radio telescopes on the planet to make most of the North Galactic plane the most sensitive to radio radiation. I made a tall map. far. Data were obtained with the Karl G. Jansky Very Large Array (VLA) in New Mexico, in two different configurations, at the 100 m Eiffelsberg telescope near Bonn. This will provide for the first time a radio survey covering all angle scales up to 1.5 arcseconds. This is the apparent size of a tennis ball lying on the ground and seen from an airplane. Unlike previous studies, GLOSTAR traces molecular gases (from methanol and formaldehyde) and atomic gases via radio recombination lines, as well as radio continuums in the frequency range of 4-8 GHz with full polarization. The spectral lines were also observed at the same time.

An overview and initial results are published in a series of four related papers: Astronomy and astrophysics..

The Milky Way Star Formation Global View (GLOSTAR) project provides the most sensitive map of most of the North Galactic plane to date, taken at the Karl G. Jansky Super Large Array (VLA) in New Mexico. Offers. With two different configurations and the MPIfR 100m Effelsberg radio telescope. An exciting new set of data is currently being used to study the Milky Way’s interstellar medium and the giant stars that died at an early age.Immediately after the 50th birthday of the Effelsberg Radio Telescope, a series of treatises based on GLOSTAR data was published. Astronomy and astrophysics..

Interferometers like the VLA can produce very clear images of the sky, but large-scale radiation is often lost. However, diffuse radio radiation can be recovered by adding data from the 100 m Eiffelsberg telescope, as shown in Figure 1. “This clearly shows that the Eiffelsberg telescope is still very important after 50 years of operation,” says Andreas. Brunthaler, lead author of the first paper to outline the study and explain the difficult data reduction techniques involved. To map the entire 145 square degrees of the survey, the team had to combine small images from about 50,000 different locations. “VLA required about 700 hours of observation time and generated about 40 terabytes of raw data,” explains Sergio Dzib, who led the data calibration work for VLA data. The Effelsberg part of the study is underway, but the study data is already being used in new and exciting science.

Previous studies have detected only about 30% of the expected number of supernova remnants in the Milky Way. Thanks to the unprecedented sensitivity of the GLOSTAR study, 80 new candidates could be found on the VLA data alone, doubling the number of observed regions. This number is expected to increase with the addition of Effelsberg data. “This is an important step in solving this long-standing mystery of the lost supernova remnant,” explains Rohit Dokara, a PhD student at MPIfR and the lead author of his second treatise.

Exciting results of submillimeter and far-infrared wavelength surveys from the ground and space have led to the detection of large, cold, clustered dust masses throughout the galaxy. As a complement to these studies, the GLOSTAR study provides very powerful and comprehensive images of both ionized and molecular tracers. Star formation On the galactic plane.

The study also included the nearby CygnusX star-forming complex. Here, a new source was detected with a 6.7 GHz methanol maser release. “The 6.7GHz line from methanol is very Giant star Karl Menten, director of MPIfR, the initiator of GLOSTAR, discovered the methanol maser. This is the second strongest radio spectrum line in stellar media just 30 years ago. .. All methanol masers in the CygnusX complex are associated with dust emission, but less than half of the sources are also detected in radio continuums.

“These masers are star markers in a very early evolutionary stage, even before we see detectable radio radiation,” explains Gisela Ortiz-León of MPIfR, who leads research in the Cygnus X area. Identifying real giant “proto” stars has long been the goal of star formation research.

Light is strongly absorbed by interstellar dust, but radio waves can peep into the most central area of ​​the Milky Way. Better those evolutionary stages by searching the recently published catalog for new continuum maps observed at VLA towards the galactic center to look for radio emissions associated with potential young stellar objects. I understand. Hans Nguyen, another PhD student at MPIfR, said, “Although quite a few objects have radio radiation, many have no corresponding radio and dust radiation and are more evolved and already. It suggests that the birth clouds are dispersed. ” Who is leading the study of these young stellar objects? The relevant radio sources allow for further constraints on the rate of star formation in the galactic center.

It is also difficult to catalog a large number of sources. The expected number of sources in a complete GLOSTAR image is tens of thousands of sources of various natures. “There are nearly 100 sources per square degree, and we use all the information available to classify,” said MPIfR, co-author of four papers and lead the first source catalog paper. Former PhD student Sac Medina explains. We are currently preparing a catalog of complete GLOSTARD configuration images.

Since its very early days, MPIfR has conducted many extensive surveys of the radio sky, most of them at longer wavelengths. The GLOSTAR survey is the first survey in a 4-8 GHz regime that is comparable to space IR surveys in terms of spatial scale and dynamic range, and is therefore a true legacy for our global perspective on star formation. It provides its own dataset with values. Galaxy.

GLOSTAR, a global view of star formation in the Milky Way survey, uses VLA’s wideband (4-8 GHz) C-band receiver and a 100 m Effelsberg radio telescope. wireless A telescope for conducting unbiased surveys to characterize the Milky Way star-forming region. This study of the central plane of the galaxy detects tracers of early-stage storytelling of high-mass star formation: compact, ultra-compact, ultra-compact HII regions, and 6.7 GHz methanol (CH3OH) masers, some of the early evolutions. It is a stage of high-mass star formation and can be used to locate very young stellar objects. Many of them are still deeply embedded in their birth material. The observations are centered around 5.8 GHz and also cover emissions from 4.8 GHz formaldehyde (H2CO) and multiple radio recombination lines (RRL). All of these will be published in future publications. Observations of the GLOSTAR were made using the VLA B and D configurations and the Effelsberg 100m telescope for large structures.

ASKAP first glimpses the galactic plane

For more information:
A. Brunthaler et al, Global View on Star Formation: GLOSTAR Galactic Plane Survey. I. Galactic longitude range 28 ° Astronomy & Astrophysics (2021) overview and first results. DOI: 10.1051 / 0004-6361 / 202039856

R. Dokara et al, Global View on Star Formation: GLOSTAR Galactic Plane Survey. II. Supernova remnant in the first quadrant of the Milky Way, Astronomy and astrophysics (2021). DOI: 10.1051 / 0004-6361 / 202039873 NS.

G. Ortiz-Leon et al, Global View on Star Formation: GLOSTAR Galactic Plane Survey. III. 6.7GHz Methanol Maser Survey on CygnusX, Astronomy and astrophysics (2021). DOI: 10.1051 / 0004-6361 / 202140817

H. Nguyen et al, Global View on Star Formation: GLOSTAR Galactic Plane Survey. IV. Radio continuum detection of young stellar objects in the galactic center region, Astronomy and astrophysics (2021). DOI: 10.1051 / 0004-6361 / 202140802

Provided by
Max Planck Society

Quote: GLOSTAR: Tracking atomic and molecular gas in the Milky Way (July 22, 2021), https: // to 2021 7 Obtained on the 22nd of March.

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Tracking the Milky Way atomic and molecular gas

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