An innovative study led by Dr. Sukanya ChakrabartiIn collaboration with Dr. Peter Craighas introduced a more precise map of the external gas disc of the Milky Way. This study, published in The Astrophysical Journal and available in ArxivUse a novel technique to overcome the limitations of the previous methods, providing new ideas about the structure of our galaxy. Presented at the 246th Meeting of the American Astronomical Society (AAS 2025) in Anchorage, Alaska, this research reveals the true nature of the atomic hydrogen disc of the galaxy and its “floculent” appearance of the galaxy.
Understand the “floculent” structure of the gas of the Milky Way
The external gas disc of the Milky Way has been challenging for a long time to map precisely, due to the complex nature of the gas itself. Traditional methods were based on kinematic distances, which assumed a soft speed model for the rotation of the galaxy. However, these methods proved to be inaccurate, particularly when deviations of the speed assumed were observed, as in spiral arms and near the galactic bulge.
The new study presents an innovative approach that is combined. Cepheides variable starsThey have known distances, with atomic hydrogen gas groups in the galaxy. This technique, called “patterns coincidence”, allows a precise mapping of the distribution of gases without depending on the speed -based models. As Dr. Chakrabarti He explains: “Distance is one of the most fundamental things that can measure in the universe, and one of the most fundamental things in which we can work in astronomy. Unless you know distances, you cannot map anything.” This method provides a clearer and more reliable map of the Milky Way Gas disc, revealing its highly grouped structure and disturbed for the first time.
The evolution of the gas mapping and the role of the cefid variables
One of the key challenges to map the gas disc of the Milky Way has been the dependence of kinematic distanceswhich converts speed information into distance estimates based on a supposed rotation curve. According Chakrabarti“The assignment of kinematic distances uses a supposed rotation curve to convert speed information into a distance estimate. For the stars, there are some really good ways to do this. But for gas, there is nothing.” This gap in understanding led to significant inaccuracies, especially in regions with complex movements, such as spiral arms and galactic bulge.
The solution, as detailed in this study, lies in the use of Cepheides variable starswhich are pulsating stars with precise and known distances. These stars, which have a regular bright pattern, allow researchers to “anchor” the distances of the nearly precision gas groups. When comparing the positions of young stars with gas in the galaxy, researchers could create a new map that reveals the true structure of the Milky Way Gas Disco. As Dr. Chakrabarti It reflects: “The structure in the stars is much softer than in gas. Gas has a very hairy appearance and actually seems much more disturbed.”
A new understanding of the gas distribution of the Milky Way
The newly created map shows that gas in the external regions of the Milky Way It does not follow the soft and ordered structure previously assumed. Instead, it exhibits a highly disturbed “flocculent” nature, with irregular groups of turbulent movement. These findings challenge the above assumptions about the softness of the galactic disk and suggest that gas is more dynamic and complex than what was thought.
This study marks the first time that the distribution of gas on the outer album of the galaxy has been mapped with such precision without depending on the traditional kinematic distances. The technique used in this research promises to improve our understanding of the Milky Way spiral structure, and could even shed light on large -scale phenomena, such as Dark matter and the interactions between the Milky Way and the dwarf galaxies. Dr. Peter CraigThe main author of the study, explains: “The maps generated using our new technique can capture characteristics in the gas that could be lost when assuming a soft rotation model for the Milky Way.”
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