{"id":15423,"date":"2026-01-09T16:30:20","date_gmt":"2026-01-09T11:00:20","guid":{"rendered":"https:\/\/theeducationoverview.in\/?p=15423"},"modified":"2026-01-09T16:30:20","modified_gmt":"2026-01-09T11:00:20","slug":"new-study-may-redefine-how-the-mass-of-the-halo-around-galaxies-is-measured","status":"publish","type":"post","link":"https:\/\/theeducationoverview.in\/?p=15423","title":{"rendered":"New study may redefine how the mass of the halo around galaxies is measured"},"content":{"rendered":"
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New study may redefine how the mass of the halo around galaxies is measured<\/strong><\/span><\/h2>\n

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Posted On: 19 DEC 2025 3:23PM by PIB Delhi<\/strong><\/span><\/div>\n
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A new research study from Raman Research Institute (RRI), an autonomous institute of the Department of Science and Technology (DST) has revealed that contributions from matter in the intergalactic medium may be affecting measurements of the diffuse envelope surrounding a galaxy. The study has far-reaching implications, given that the envelope holds power to make or break galaxies and measuring the mass is crucial for tracing how galaxies form.<\/strong><\/span><\/p>\n

A galaxy evokes images of dust and stars sparkling within beautiful spirals. But beyond the galaxy\u2019s outskirts lurks a diffuse, ghostly halo spreading out as far as 10-20 times the size of the galaxy. Most of the galaxy\u2019s mass lies beyond the stars in this halo, composed of the mysterious dark matter \u2014 the invisible glue keeping the universe together \u2014 and gas. The gaseous component of the halo is called the circumgalactic medium or CGM. The region outside the CGM, constitutes the intergalactic medium or IGM.<\/strong><\/span><\/p>\n

Mapping the distribution of gas in CGM is essential because CGM connects the galaxy to the cosmic web \u2014 the filamentary scaffolding pervading the universe. In doing so, CGM plays a critical role in galaxy evolution by controlling the inflow of gas into the galaxy and outflow from it. By measuring the amount of highly ionized oxygen \u2014 oxygen with five of its electrons stripped off \u2014 contained in CGM, astronomers estimate the mass of CGM.<\/strong><\/span><\/p>\n

Observational astronomers use light from incredibly bright cores of distant galaxies to map the CGM. When light from such a background object passes through the gas in the CGM of a foreground galaxy, certain elements absorb particular wavelengths.<\/strong><\/span><\/p>\n

But there lies an inherent problem in the observational technique. When astronomers perform an observation, the measured ionized oxygen is the total integrated value along the line of sight.<\/strong><\/span><\/p>\n

As CGM and IGM both lie along the line of sight, there is no way to tell apart the contribution from CGM and IGM in the observed values. Current models take all of the ionized oxygen observed to be from the CGM.<\/strong><\/span><\/p>\n

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Fig 1<\/em>. Artistic representation of the circumgalactic medium surrounding the galaxy<\/em><\/strong><\/span><\/p>\n

This new research from Raman Research Institute (RRI) uses models to suggest that a lot of the gas attributed to CGM could be coming from IGM.<\/strong><\/span><\/p>\n

Dr. Kartick Sarkar, astrophysicist in the Astronomy and Astrophysics division at RRI and an author on the\u00a0new paper published in The Astrophysical Journal<\/a>\u00a0explains the relation between CGM and IGM drawing an analogy.<\/strong><\/span><\/p>\n

\u201cImagine a street magician showing their tricks. People would slowly start gathering around \u2026 and the crowd grows. Initially, people would rush in to see the show. However, as soon as they reach the boundary of the crowd, they stop,\u201d said Dr Sarkar. The magician in Dr. Sarkar\u2019s analogy is the galaxy, and the crowd is the CGM. \u201cThe bigger the magician, the bigger the crowd\u201d he pointed out. The region outside the CGM, not gravitationally bound by the galaxy, constitutes the intergalactic medium or IGM.<\/strong><\/span><\/p>\n

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Fig 2. Artistic representation of the presence of ionised oxygen surrounding galaxies, and the principal of their observation<\/em><\/strong><\/span><\/p>\n

\u201cWe are challenging the notion that the entire ionized oxygen belongs to CGM,\u201d says Dr. Sarkar. The team used a mathematical description of CGM and the gas falling into it from the IGM. They then calculated the amount of ionized oxygen (one of the most abundant elements in the universe) each of them contains and compared it with the observations.<\/strong><\/span><\/p>\n

\u201cWe\u2019re suggesting that a relatively small fraction of the ionized oxygen is coming from CGM and that there\u2019s a blanket of IGM around CGM which is contributing to the observed oxygen,\u201d says Dr. Sarkar. This contamination of CGM by IGM could lead to overestimating CGM\u2019s mass.<\/strong><\/span><\/p>\n

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Fig 3. Artistic representation of the presence of ionised oxygen in the intergalactic medium in the case of low-mass galaxies<\/em><\/strong><\/span><\/p>\n

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Dr. Sarkar and colleagues got their first hint of something being amiss when they noticed that the models for CGM mass disagree with the observations for low-mass galaxies. Their current theory of IGM confounding CGM measurements applies to galaxies across masses and can help explain the discrepancy observed in lower-mass galaxies.<\/strong><\/span><\/p>\n

“For high mass galaxies like our Milky Way, the CGM may contribute just 50% of the ionised oxygen, with the rest coming from the IGM. For lower mass galaxies, it can go down to 30%,” says Dr. Sarkar. The study highlights the need to consider contributions from IGM when interpreting CGM observations.<\/strong><\/span><\/p>\n

The researchers from RRI along with those from the Hebrew University of Jerusalem, Israel, are working towards upgrading their basic model into a more realistic and comprehensive one encompassing more of the parameters involved. \u201cWe\u2019re sure there\u2019s a discrepancy. Now we\u2019re trying to quantify this discrepancy exactly,\u201d says Dr. Sarkar.<\/strong><\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

New study may redefine how the mass of the halo around galaxies is measured Posted On: 19 DEC 2025 3:23PM by PIB Delhi A new research study from Raman Research Institute (RRI), an autonomous institute of the Department of Science and Technology (DST) has revealed that contributions from matter in the intergalactic medium may be …<\/p>\n","protected":false},"author":2,"featured_media":15424,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-15423","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-education-news"],"_links":{"self":[{"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=\/wp\/v2\/posts\/15423","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=15423"}],"version-history":[{"count":1,"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=\/wp\/v2\/posts\/15423\/revisions"}],"predecessor-version":[{"id":15425,"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=\/wp\/v2\/posts\/15423\/revisions\/15425"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=\/wp\/v2\/media\/15424"}],"wp:attachment":[{"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15423"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=15423"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/theeducationoverview.in\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=15423"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}