A new catalogue of infrared dark clouds

Date:

Share post:

Infrared dark clouds (IRDCs) are dark patches of cold dust and gas seen in the sky against the bright diffuse infrared glow of warm dust in our galaxy. These IRDCs, massive and rich in molecules, are natural sites for star birth – one of the main reasons why astronomers are actively studying them. IRDCs were first detected by two early space infrared missions, the Infrared Space Observatory and the Midcourse Space Experiment, but the IRAC camera on Spitzer revolutionized the field with its dramatically enhanced sensitivity and spatial resolution.

A new catalogue of infrared dark clouds
A false-colour infrared image of the Infrared Dark Cloud called “the Snake” as seen by the IRAC camera on the Spitzer
Space Telescope. Astronomers have produced a new catalogue of IRDCs from IRAC’s sky survey images using a new
 computational search-and-detection algorithm. (Blue dots are stars relatively undimmed by dust, while the
red dots are young stars embedded in the cloud) [Credit: NASA, JPL-Caltech/S. Carey (SSC/Caltech)]

IRAC had completed several surveys of the Milky Way before being shut off last February, and astronomers have been using the infrared images to identify and analyze the characteristics of IRDCs. The Submillimeter Array and ALMA facilities, operating with high sensitivity and resolution at submillimeter wavelengths where the cold molecular gas can be characterized, have enabled astronomers to follow up on these newly discovered sources and to determine the gas temperatures, densities and motions, leading to advances in our understanding of the earliest stages of star formation in these stellar nurseries.




One issue constraining research has been the lack of an up-to-date catalogue of IRDCs. There are three main difficulties: IRDC sizes can vary greatly, from those that are very extended (more than a light-year in size) to others that are over one hundred times smaller (and of course their distances are key to their angular appearances), their shapes are usually irregular and ill defined, and not least they often are located in complex regions with hundreds of other sources. Searching the Milky Way for them has been a daunting task.

CfA astronomers Jyothish Pari and Joe Hora have just completed a new catalogue of IRDCs containing 18,845 objects extracted from the IRAC infrared images using a new computer algorithm they developed that uses contour finding and neural network methods. The technique scans the images for the clouds’ dark edges and closed contours, and evaluates the reliability of the detections in an automated, objective technique that could be extended to use with other surveys. The results of the new catalog are in good agreement with earlier findings, but in addition to finding many more objects the new catalog contains more IRDCs in low-contrast regions and also confirms (as expected) that many of the previously identified IRDCs are actually comprised of two or more smaller objects.

The study is poblished in Publications of the Astronomical Society of the Pacific.

Source: Harvard-Smithsonian Center for Astrophysics [June 05, 2020]

ADVERTISEMENT

spot_img

Related articles

Physicists use observations of black holes to measure photon mass

A global team of scientists, including a University of Mississippi physicist, has determined the best constraint on the...

Most massive neutron star ever detected, almost too massive to exist

Neutron stars - the compressed remains of massive stars gone supernova - are the densest "normal" objects in...

An infrared close up of the moon

A first-of-its-kind camera developed in partnership between CU Boulder and Ball Aerospace will soon be landing on the...

Atoms may hum a tune from grand cosmic symphony

Researchers playing with a cloud of ultracold atoms uncovered behavior that bears a striking resemblance to the universe...

Boulders on a Martian landslide

The striking feature in this image, acquired by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's...

Detection of an echo emitted by our Galaxy’s black hole 200 years ago

An international team of scientists has discovered that Sagittarius A* (Sgr A*), the supermassive black hole at the...

Milky Way’s supermassive black hole may have ‘unseen’ siblings

Astronomers are beginning to understand what happens when black holes get the urge to roam the Milky Way. Credit: Yale...

The bold plan to see continents and oceans on another Earth

What if we could take a picture of an Earth-like planet around another star that was sharp enough...