Tracing the outer disk of NGC 300: An ultraviolet view

Chayan Mondal; Annapurni Subramaniam; Koshy George

doi:10.1007/s12036-019-9603-4

paper

Tracing the outer disk of NGC 300: An ultraviolet view

arXiv:1907.06366 · doi:10.1007/s12036-019-9603-4

Abstract

We present an ultra-violet (UV) study of the galaxy NGC~300 using GALEX far-UV (FUV) and near-UV (NUV) observations. We studied the nature of UV emission in the galaxy and correlated it with optical, H~I and mid-infrared (3.6 $μ$ m) wavelengths. Our study identified extended features in the outer disk, with the UV disk extending up to radius 12 kpc ( $>$ 2R $_{25})$ . We estimated the FUV and NUV disk scale-length as 3.05 $\pm$ 0.27 kpc and 2.66 $\pm$ 0.20 kpc respectively. The scale-length in FUV is 2.3 times larger than that at 3.6 $μ$ m, and we also find the disk to gradually become flatter from longer to shorter wavelengths. We performed a statistical source subtraction to eliminate the background contaminants and identified 261 unresolved UV sources between the radii 5.3 kpc and 10 kpc (1 $\sim$ 2 R $_{25}$ ). The identified UV sources show an age range between 1 - 300 Myr with a peak at 25 Myr and a mass range between $1 0^{3} M_{⊙}$ to $1 0^{6} M_{⊙}$ , estimated using starburst99 models. The north-eastern spiral arm is found to be populated by young low mass sources suggesting that the star formation in this spiral arm is a recent phenomenon. The UV emission beyond the R $_{25}$ radius has contribution from these low mass sources and is extended up to $\sim$ 2R $_{25}$ radius. We conclude that NGC~300 has an extended UV disk, mainly populated by young low mass sources. The star formation rate is measured to be $\sim$ 0.46 $M_{⊙} / y r$ which is comparable to its near optical twin M33.

arXiv commentAccepted for publication in Journal of Astrophysics and Astronomy

Tracing the outer disk of NGC 300: An ultraviolet view

Abstract

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