Sains Malaysiana 47(6)(2018): 1241–1249

http://dx.doi.org/10.17576/jsm-2018-4706-20

Dark Matter in the Central Region of NGC 3256

(Jirim Gelap di Rantau Tengah NGC 3256)

ISRAA ABDULQASIM MOHAMMED ALI¹, CHORNG-YUAN HWANG², ZAMRI ZAINAL ABIDIN^1* & ADELE LAURIE PLUNKETT³

¹Physics Department, University of Malaya, 50603 Kuala Lumpur, Federal Territory, Malaysia

²Institute of Astronomy, National Central University, 32001 Jhongli, Taiwan

³European Southern Observatory (ESO), Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago, Chile

Diserahkan: 12 Disember 2017/Diterima: 10 Januari 2018

ABSTRACT

We investigated the central mass distribution of the luminous infrared galaxy NGC 3256 at a distance of 35 Mpc by using CO(1-0) observations of the Atacama Large Millimeter and sub-millimeter Array (ALMA) and near-IR data of the Two Micron Sky Survey (2MASS). We found that there is a huge amount of invisible dynamical mass (4.48 × 1010 ) in the central region of the galaxy. The invisible mass is likely caused by some dark matter, which might have a cuspy dark matter profile. We note that this dark matter is difficult to explain with the conventional Modified Newtonian Dynamics (MOND) model, which is only applicable at a low acceleration regime, whereas the acceleration at the central region of the galaxy is relatively strong. Therefore, this discovery might pose a challenge to the conventional MOND models.

Keywords: Dark matter; evolution; galaxies; individual (NGC 3256)

ABSTRAK

Kami telah menjalankan kajian terhadap taburan jisim di kawasan pusat galaksi inframerah terang NGC 3256 pada jarak 35 Mpc dengan menggunakan cerapan CO(1-0) dari Atacama Large Millimeter dan sub-millimeter Array (ALMA) dan maklumat inframerah dekat daripada Two Micron Sky Survey (2MASS). Penemuan kami menunjukkan terdapat jumlah jisim dinamik ghaib yang besar (4.48 × 1010 ) di kawasan pusat galaksi. Jisim ghaib ini berkemungkinan besar merupakan jirim gelap, yang mempunyai profil 'cuspy'. Hal tersebut sukar diterangkan dengan model 'Modified Newtonian Dynamics' (MOND), yang hanya terpakai untuk kadar pecutan yang rendah, tetapi pecutan di kawasan pusat galaksi agak tinggi. Oleh yang demikian, penemuan ini mencabar model MOND konvensional.

Kata kunci: Evolusi; galaksi; individu (NGC 3256); jirim gelap

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* Pengarang untuk surat-menyurat; email: zzaa@um.edu.my