NGC 5055 ve NGC 3627 Sarmal Galaksilerinde Molekül Bulutlarının Fiziğinin Araştırılması

Year 2024, Volume: 29 Issue: 1, 97 - 108, 30.04.2024

Hülya Eser Sulu Selçuk Topal

https://doi.org/10.53433/yyufbed.1363547

Abstract

Galaksiler morfoloji açısından birkaç kategoride gruplandırılabilse de, oldukça farklı içsel özelliklere sahiptirler. Sarmal galaksiler önemli miktarda moleküler gaz barındırır ve yıldız oluşumu olmayan eliptik galaksilere kıyasla devam eden yıldız oluşum aktivitesine sahiptir. Moleküler ışınım salma çizgileri, yıldızların doğup öldüğü gaz bulutlarının iç özelliklerini incelemek için kullanılır. Karbon monoksit (CO) galaksilerdeki yıldızlararası ortamda (YAO) kolaylıkla tespit edilebilir. Bu çalışmada, dört CO geçişini ve bunların çizgi oranlarını kullanarak NGC 5055 (M63) ve NGC 3627 (M66) disk galaksilerinin birçok bölgesinde gaz bulutunun fiziğini araştırıyoruz. 12CO(J=1-0) geçişi, diğer 12CO(J=2-1, J=3-2) ve 13CO(J=1-0) geçişlerine kıyasla, her iki galaksinin diskinde daha parlaktır. CO akı yoğunlukları galaksi merkezlerinden diskin eteklerine doğru bir azalma göstermektedir. Ancak NGC 3627, NGC 5055’e kıyasla oldukça düzensiz bir azalma eğilimine sahiptir. CO çizgi oranları merkezden uzaklaştıkça bir süre artış gösterir ve daha sonra azalmaya başlar. Her ne kadar NGC 5055 diskinin her iki tarafında çizgi oranları benzer değişim gösterse de, NGC 3627 diskinin her iki tarafında zıt bir değişime sahiptir. Bu nedenle YAO, galaksinin farklı bölgelerinde farklı sıcaklıklara, opaklığa, yoğunluklara ve yıldız oluşum seviyelerine sahip olabilir. Sonuçlarımız, her iki galaksinin merkezinde bulunan çizgi oranlarının farklı olduğunu göstermektedir. Bu fark, NGC 3627'nin merkezi bölgesinde çubuk yapısı nedeniyle oluşan gaz birikiminin bir sonucu olabilir. NGC 5055'in merkezindeki çizgi oranları literatürdeki diğer sarmal ve aktif galaksilerin merkezleri için bulunan aralıktadır, ancak NGC 3627'nin merkezindeki oranlar nispeten daha düşüktür.

Keywords

Galaksiler, Molekül bulutları, Sarmal galaksiler, Yıldız oluşumu

Probing the Physics of Molecular Clouds in Spiral Galaxies NGC 5055 and NGC 3627

Abstract

Although galaxies can be grouped in a few categories in terms of morphology, they have remarkably different intrinsic properties. Spiral galaxies host substantial amounts of molecular gas and have ongoing star formation activity with respect to elliptical galaxies lacking star formation. Molecular emission lines are used to probe the internal properties of molecular gas clouds where stars are born and die. Carbon monoxide (CO) is easily detectable in the interstellar medium (ISM) of galaxies. In this research, we probe the physics of the gas clouds at multiple positions in disc galaxies NGC 5055 (M63) and NGC 3627 (M66) using four CO transitions and their line ratios. 12CO(J=1-0) is the brightest across the disc of both galaxies compared to the other lines, i.e., 12CO(J=2-1, J=3-2) and 13CO(J=1-0). The CO intensities show a decrease from the center of the galaxies to the outskirts. However, NGC 3627 shows a rather irregular decrease pattern compared to NGC 5055. The CO line ratios show an increase up to a distance from the center and start to decrease. Although NGC 5055 shows a similar variation in the line ratios on each side of the disc, NGC 3627 has an opposite trend on either side. Therefore, the ISM could have different temperatures, opacity, densities, and levels of star formation in different regions of the galaxy’s disc. Our results indicate that the line ratios found at the center of both galaxies are different. The difference could be the result of the bar-driven gas accumulation in the center of NGC 3627. The line ratios in the center of NGC 5055 are within the range found for the centers of other spiral and active galaxies in the literature, but the ratios in the center of NGC 3627 are relatively lower.

Keywords

Galaxies, Molecular clouds, Spiral galaxies, Star formation

Thanks

The authors thank the anonymous referees for their useful comments and suggestions. This research has used the NASA/IPAC Infrared Science Archive, operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The James Clerk Maxwell Telescope is operated by the East Asian Observatory on behalf of The National Astronomical Observatory of Japan; Academia Sinica Institute of Astronomy and Astrophysics; the Korea Astronomy and Space Science Institute; the National Astronomical Research Institute of Thailand; Center for Astronomical Mega-Science (as well as the National Key R&D Program of China with No. 2017YFA0402700). Additional funding support is provided by the Science and Technology Facilities Council of the United Kingdom and participating universities and organizations in the United Kingdom and Canada. This publication made use of data from COMING, CO Multi-line Imaging of Nearby Galaxies, a legacy project of the Nobeyama 45-m radio telescope.

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